Sterrekunde

Hoe helder sou die son blyk uit die hipotetiese Planet Nine wat Caltech voorgestel het?

Hoe helder sou die son blyk uit die hipotetiese Planet Nine wat Caltech voorgestel het?


We are searching data for your request:

Forums and discussions:
Manuals and reference books:
Data from registers:
Wait the end of the search in all databases.
Upon completion, a link will appear to access the found materials.

Daar word gesê dat Theoretical Planet Nine, voorgestel deur Mike Brown en Konstantin Batygin van Caltech, 'n baan van 15-20 duisend jaar het. Ongeveer hoe helder sou die son verskyn uit die planeet nege aphelion en perihelion?


Tussen $ 1 / 40.000 $ en $ 1 / 8.000.000 $ van die helderheid gesien vanaf die aarde, afhangende van hoe die werklike baan sou blyk te wees, en waar die planeet in sy wenteltydperk van $ 15.000 $ is.

Helderheid daal as $ dfrac {1} {r ^ 2} $ met afstand vanaf die ligbron. Aarde is op $ 1 ~ textrm {AU}. $ Die teoretiese planeet is op $ 200 ~ textrm {AU} $ wanneer dit die naaste aan die son is, en tot $ 2800 ~ textrm {AU} $ op die punt verste van die son af aan die boonste punt van die geskatte baan.


So bv. $ 1/200 ^ 2 = 1 / 40.000 $ van die helderheid (helderheid) gesien vanaf die aarde.

Vir die manier waarop 'n mens dit sou ervaar, kan ons omskakel na blootstellingswaarde soos gebruik in fotografie: Die verskil in blootstellingswaarde (fotografiese 'stop') is $ log 2 $ van die helderheidsverhouding, dus sal ons $ 15 $ tot $ 23 $ hê stop minder lig as op aarde. Sonnige middag op aarde is $ 15 ~ textrm {EV}. $

Die helderheid van die middaguur op die planeetoppervlak sou dus wees:

  • Teen $ 200 ~ textrm {AU} is $ planeetbaan die naaste aan die son: ongeveer $ 0 ~ textrm {EV}, $ ongeveer dieselfde as 'n ligte binnekant

  • $ 400 ~ textrm {AU}, $ onderste grens op semi-hoofas: $ -2 ~ textrm {EV}, $ soortgelyk aan 'n landskap verlig deur die volmaan

  • $ 1500 ~ textrm {AU}, $ boonste grens op semi-hoofas: $ -6 ~ textrm {EV}, $ soortgelyk aan landskap verlig deur 'n kwartmaan

  • $ 2800 ~ textrm {AU}, $ boonste grens op aphelion (die punt op die baan die verste van die son af): $ -8 ~ textrm {EV}. $ Dit sou donker wees, maar u sou waarskynlik nog genoeg sien om te vermy dinge raakloop.


As dit bestaan, het die baan 'n perihelium van miskien 300 au en 'n aphelie van miskien 2700 au.

U kan dan net skaal vanaf die helderheid $ m = -26,7 $ van die son op die aarde. Dit sal tussen 12,4 en 17,1 sterker word. Dus nog baie helderder as die volgende helderste ster in die lug.


Kan 'Planet Nine' 'n skelm planeet wees?

'N Onlangse studie voer aan dat die hipotetiese planeet nege deur 'n ander sonnestelsel verlore kon gaan en dan deur die swaartekrag van ons son uit die intergalaktiese afval gestroop kon word.

Vandat wetenskaplikes die bestaan ​​van 'n "Planet Nine" voorgestel het, het sterrekundiges die hemel opgesoek vir tekens van die ontwykende liggaam. Maar as die planeet wel bestaan, is dit baie ver weg, aangesien daar geen direkte bewyse van sy huidige ligging was nie, en dit dui slegs op die oorsprong.

In 'n onlangse studie word aangevoer dat die geheimsinnige planeet, indien dit wel in die buitenste dele van die sonnestelsel bestaan, moontlik 'n 'skelm' was wat deur die son se swaartekrag vasgevang is.

Die moontlike bestaan ​​van Planet Nine is in Januarie 2016 deur die astrofisici Michael Brown en Konstantin Batygin van die California Institute of Technology voorgestel. Die navorsers het opgemerk dat sekere swaartekragafwykings in die buitenste sonnestelsel verklaar kon word deur 'n massiewe planeet wat buite die waargenome streke skuil. die sonnestelsel, ongeveer 20 keer verder as Neptunus se gemiddelde afstand van die son af.

Maar hoe kan 'n planeet wat tien keer groter is as die aarde so ver uitloop?

'N Studie wat verlede week tydens die 229ste vergadering van die American Astronomical Society in Grapevine, Texas, aangebied is, het 'n oplossing voorgestel. Nadat hy 156 rekenaarsimulasies geskep het van hipotetiese skelm planete wat ons sonnestelsel teëkom, het die voorgraadse James Vesper van die New Mexico State University dit "baie aanneemlik" gevind dat Planet Nine 'n gevangene skelm kan wees, berig Space.com.

Namate Kamala Harris se portefeulje groei, groei die ondersoek ook

"'N Skelm planeet is 'n voorwerp wat gevorm het soos 'n planeet van 'n skyf om 'n ster, soos die planete in ons eie sonnestelsel," sê Joshua Pepper, 'n astrofisikus en professor in fisika aan die Lehigh Universiteit wat nie by die nuwe studie betrokke was nie. in 'n e-pos aan The Christian Science Monitor. 'As die planeet egter vroeg in sy vorming naby 'n baie massiewer planeet sou gaan, voordat die wentelbane in sy tuisstelsel gaan sit het, kan dit slingervel uit sy sonnestelsel kry en sou hy nou deur die interstellêre ruimte in die Melkweg dwaal. onder die sterre. '

Volgens die studie is die skelm planeet in 60 persent van die simulasies deur gravitasiekragte uit die stelsel geslinger - maar in die ander 40 persent is dit deur die son gevang.

Dit sou help om die afstand van Planet Nine te verklaar, maar dit is steeds onwaarskynlik, sê Michael Smutko, 'n professor in astrofisika en fisika aan die Noordwes-Universiteit, wat nie by die navorsing betrokke was nie.

"Stel jou voor dat die son so groot soos 'n lemoen of appel was," vertel dr. Smutko per e-pos aan die Monitor. "Stel jou voor dat die planete miskien vrugtevlieë rondom die appelgrootte Son gons. Op hierdie skaal is die naaste ster aan die son, Proxima Centauri, nog 'n appel van ongeveer 1.400 kilometer weg! Dit is ongeveer Chicago van Tucson. Stel jou nou die kans voor van 'n vrugtevlieg in Chicago wat 1400 myl op pad is en die appel in Tucson vind kon gebeur, maar dit is nie die manier om te wed nie. '

Smutko verkies die teorie dat Planet Nine saam met die res van die sonnestelsel gevorm is.

"Die 'klassieke' planete, Mercurius, Venus, Mars, Jupiter en Saturnus is almal maklik met die blote oog sigbaar en is al duisende en duisende jare bekend," sê Smutko. "Omdat hierdie voorwerpe vanaand na nag hul posisies in die lug verander het in vergelyking met die agtergrondsterre (wat blykbaar nooit verander het nie), word godagtige eienskappe aan die planete gegee. Die naam 'planeet' kom trouens van die Griekse woord vir 'swerwer.' "

Na die uitvinding van die teleskoop in die vroeë 1600's, het planete minder geheimsinnig geword, wat 'n nuwe era van ondersoek tydens die wetenskaplike rewolusie ingelui het. In 1609-1610 het Galileo Galilei die fases van Venus deur middel van 'n teleskoop ondersoek om wetenskaplike bewys te lewer dat die voorwerpe in die sonnestelsel om die son wentel en nie oor die aarde nie, wat 'n belangrike verskuiwing in die mens se persepsie van die heelal aandui.

"Die [ontdekkings van latere planete] het mense gewys hoe uitgebreid die heelal was en hoeveel daar te leer was," sê Pepper. 'Maar dit het oor die algemeen nie die wêreldbeskouing van die beskawings wat dit ontdek het, verander nie, omdat daardie ontdekkings nie die beeld van die heelal wat hulle gehad het, verander het nie, die manier waarop Copernicus en Galileo ons begrip van die plek van die Aarde in die sonnestelsel verander het, die manier waarop Einstein ons persepsie van ruimte en tyd verander het. '

Kry die Monitor Stories waaroor u belangstel by u posbus afgelewer.

Die bestudering van planete gaan voort om vooropgestelde opvattings oor die sonnestelsel en ons rol daarin uit te daag. Selfs die degradering van Pluto van die status van planeet tot dwergplaneet in 2006 het wetenskaplikes en die algemene publiek gedwing om te heroorweeg wat 'n planeet is.

"As [Planet Nine] regtig bestaan, en bevestig en waargeneem word, sal dit waarskynlik vir ons sê dat die proses van planeetvorming gewelddadiger en chaotieser is as wat voorheen gedink is," sê Pepper. "En dit sou ons vertel dat daar nog baie ruimte is om te ontdek waar nuwe ontdekkings kan skuil."


'N Onsigbare planeet

Pluto is sy tuiste aan die rand van die Kuiper-gordel, 'n gebied van ysbedekte gesteentes wat oorgebly het van die vorming van die sonnestelsel. Batygin en Brown het opgemerk dat verskeie van die voorwerpe ooreenkomste in hul wentelbane gehad het, wat daarop dui dat hulle deur 'n massiewe liggaam geraak word. Die gewone verdagtes sou die reuse-planete van die sonnestelsel wees, maar die voorwerpe wat die paar raakgesien het, was te ver om deur die lywe geraak te word.

Deur die vreemde wentelbane van die voorwerpe te ontleed, stel Batygin en Brown die teenwoordigheid van 'n nuwe planeet in die sonnestelsel voor, 'n voorwerp vier keer so groot soos die aarde en tien keer so massief. Hulle het die moontlike baan van die onsigbare reus, wat hulle 'Planet Nine' genoem het, opgespoor. Om die waargenome steurnisse te bewerkstellig, het hulle 'n baan wat so naby as 200 astronomiese eenhede (AU) van die son af kom, gekarteer en so ver as 1 200 AE beweeg. (Een AU is die afstand van die aarde na die son en mdash ongeveer 93 miljoen myl, oftewel 150 miljoen kilometer.)

Nie almal is daarvan oortuig dat 'n enorme reus om die kante van die sonnestelsel sluip nie. Ann-Marie Madigan, 'n postdoktorale navorser aan die Universiteit van Kalifornië in Berkeley, het bevind dat die voorwerpe 'vanself kon organiseer', wat mekaar in hul ongewone wentelbane kon druk en trek. In die samewerking met mede-outeur Michael McCourt van die Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Massachusetts, het die paar gevind dat as die voorwerpe in die verspreide skyf ongeveer gelyk is aan die massa van die Aarde, hulle hulself na hul huidige wentelbane kon gesleep het. binne ongeveer 600 miljoen jaar na die geboorte van die sonnestelsel, wat die behoefte aan inmenging van Planet Nine weglaat.

Volgens Batygin en Brown is die Planet Nine-scenario egter waarskynliker, omdat huidige opnames daarop dui dat daar nie genoeg massa in die streek is nie. In hul navorsing merk hulle op dat die skyf materiaal wat die planete gebore het, moontlik met genoeg massa begin het, maar interaksies met die reuse-planete sou dit vinnig uit die sonnestelsel geslinger het.

'N Ander studie het voorgestel dat Planet Nine die Cassini-sonde van die NASA kon sleep en om Saturnus wentel. Agn & egraves Fienga aan die C & ocircte d'Azur-sterrewag in Frankryk en haar kollegas het Planet Nine bygevoeg tot 'n teoretiese model om te sien of die voorgestelde wêreld die raaisel van klein veranderinge in die baan van die ruimtetuig kan oplos wat bestaande sonstelselvoorwerpe nie kan verantwoord nie. As die ontbrekende planeet ongeveer 600 AE weg in die rigting van die sterrebeeld Cetus lê, kan rekening gehou word met die raaiselagtige versteurings.

Volgens Cassini se missiebestuurders ervaar die ruimtetuig egter eintlik geen geheimsinnige afwykings nie.

"Alhoewel ons dit graag sou wou as Cassini sou help om 'n nuwe planeet in die sonnestelsel op te spoor, sien ons geen steurings in ons baan wat ons nie met ons huidige modelle kan verklaar nie," het Earl Maize, Cassini-projekbestuurder by JPL, gesê n verklaring.

Ander voorwerpe in die Kuiper-gordel kan help om die saak vir die wêreld te spyker. Navorsing deur Renu Halhotra, Kathryn Volk en Xianyu Wang, almal aan die Universiteit van Arizona, onthul 'n halfdosyn ysbedekkende gesteentes waarvan die bane blyk te pas by die teenwoordigheid van 'n verre planeet.

'Dit is 'n ander bewys as wat Mike Brown en Konstantin Batygin voorgestel het,' het Volk aan Space.com gesê.

"Ek dink dit is regtig intrigerend."


Planeet Nege

'N Kunstenaar en illustrasies van 'n moontlike negende planeet in ons sonnestelsel wat aan die rand van ons sonnestelsel sweef. Die baan van Neptunus & rsquos word as 'n helder ring om die son vertoon. Krediet: ESO / Tom Ruen / nagualdesign

Dit hang miskien bashly aan die ysige buitekante van ons sonnestelsel, skuil in die donker, maar trek subtiele toutjies agter die skerms: strek die wentelbane van ver liggame uit, kantel miskien selfs die hele sonnestelsel eenkant toe.

As 'n planeet daar is, is dit buitengewoon ver en sal dit so bly (met geen kans nie en as u vra of u ooit met die aarde sal bots, of 'n duisternis van duisternis sal bring). Dit is 'n moontlike planeet nege, 'n wêreld miskien 10 keer die massa van die aarde en 20 keer verder van die son af as Neptunus. Die tekens tot dusver is indirek, hoofsaaklik die swaartekragvoetspore, maar dit dra nogtans by tot 'n dwingende saak.

Een van die mees toegewyde spoorsnyers sê dit is nou moeiliker om ons sonnestelsel sonder 'n Planet Nine voor te stel as met een.

Daar is nou vyf verskillende waarnemingslyne wat dui op die bestaan ​​van Planet Nine, & het rdquo gesê Konstantin Batygin, 'n planetêre astrofisikus van Caltech wie se span moontlik besig is om te sluit. & ldquoAs u hierdie verduideliking sou verwyder, en u sou dink dat Planet Nine nie bestaan ​​nie, dan genereer jy meer probleme as wat jy oplos. Skielik het u vyf verskillende raaisels, en u moet vyf verskillende teorieë uitdink om dit te verduidelik. & Rdquo

Batygin en sy medeskrywer, Caltech-sterrekundige Mike Brown, het die eerste drie broodkrummels op die Planet Nine & rsquos-roete beskryf in 'n artikel in Januarie 2016, gepubliseer in die Astronomical Journal. Ses bekende voorwerpe in die verre Kuiper-gordel, 'n gebied van ysige liggame wat strek vanaf Neptunus na buite na die interstellêre ruimte, het almal elliptiese bane wat in dieselfde rigting wys. Dit sou onwaarskynlik wees en ndash en agterdogtig genoeg wees. Maar hierdie wentelbane word ook op dieselfde manier gekantel, ongeveer 30 grade & ldquodownward & rdquo in vergelyking met die pannekoekagtige vlak waarbinne die planete om die son wentel.

Broodkruimel nommer drie: rekenaarsimulasies van die sonnestelsel met Planet Nine ingesluit, toon dat daar meer voorwerpe moet skuins ten opsigte van die sonvlak. In werklikheid sou die kanteling van die orde van 90 grade wees, asof die vlak van die sonnestelsel en hierdie voorwerpe 'n & ldquoX & rdquo vorm as dit langsaan gesien word. Seker genoeg het Brown besef dat vyf sulke voorwerpe wat al bekend is aan sterrekundiges die rekening vul.

Nog twee leidrade het na die oorspronklike koerant verskyn. 'N Tweede artikel van die span, gelei deur Batygin & rsquos-student Elizabeth Bailey, het getoon dat Planet Nine die planete van ons sonnestelsel gedurende die afgelope 4,5 miljard jaar kon laat kantel. Dit kan 'n jarelange raaisel verklaar: waarom is die vlak waarin die planete wentel, ongeveer 6 grade gekantel in vergelyking met die son se ewenaar?

& ldquo Oor lang tydperke sal Planet Nine die hele sonnestelselvliegtuig voorwend of laat slinger, net soos 'n blad op 'n tafel, & rdquo Batygin.

Die laaste teken van die teenwoordigheid van Planet Nine & rsquos behels die sonnestelsel & rsquos contrarians: voorwerpe uit die Kuiper-gordel wat in die teenoorgestelde rigting wentel van alles in die sonnestelsel. Die planeet Nine & rsquos-omwenteling beïnvloed die rede waarom hierdie liggame uit die verre Kuiper-gordel die binneste Kuiper-gordel belemmer en verontreinig.

& ldquo Geen ander model kan die vreemdheid van hierdie wentelbane omlê nie, & rdquo het Batygin gesê. & ldquo Dit blyk dat Planet Nine 'n natuurlike weg bied vir hul generasie. Hierdie dinge is met behulp van Planet Nine uit die sonnestelselvlak gedraai en dan deur Neptunus na binne versprei. & Rdquo

Die oorblywende stap is om Planet Nine self te vind. Batygin en Brown gebruik die Subaru-teleskoop op Hawaii en die Mauna Kea-sterrewag om dit te probeer doen. Die instrument is die & ldquobest hulpmiddel & rdquo vir die uitsoek van dowwe, uiters ver voorwerpe wat verlore gaan in groot dele van die lug, het Batygin gesê.

Maar waar kom Planet Nine vandaan? Batygin sê hy spandeer min tyd om te herkou oor die oorsprong daarvan en of dit nou 'n voortvlugtende uit ons eie sonnestelsel is, of net 'n dwalende skelm planeet wat deur die son en die swaartekrag gevang word.

& ldquo Ek dink Planet Nine & rsquos-opsporing sal ons iets vertel oor die oorsprong daarvan, & rdquo het hy gesê.

Ander wetenskaplikes bied 'n ander moontlike verklaring vir die Planet Nine-bewyse wat deur Batygin aangehaal word. 'N Onlangse ontleding gebaseer op 'n lugkarteringprojek genaamd die Outer Solar System Origins Survey, wat meer as 800 nuwe & ldquotrans-Neptuniese voorwerpe, & rdquo of TNO's ontdek het, dui daarop dat die bewyse ook ooreenstem met 'n ewekansige verspreiding van sulke voorwerpe. Tog kon die ontleding van 'n span onder leiding van Cory Shankman van die Universiteit van Victoria nie Planet Nine uitsluit nie.

As Planet Nine gevind word, sal dit 'n soort tuiskoms wees, of ten minste 'n familiereünie. Oor die afgelope twintig jaar het die opnames van planete rondom ander sterre in ons sterrestelsel gevind dat die mees algemene soorte aarde's en rdquo's is, en hul ietwat groter neefs en groter as die aarde, maar kleiner as Neptunus.

Tog is hierdie algemene planete van die tuinverskeidenheid opvallend in ons sonnestelsel afwesig. Met 'n gewig van ongeveer tien keer die aarde- en rsquos-massa, sal die voorgestelde Planet Nine goed pas.

Planet Nine kan blykbaar ons vermiste super Aarde wees.

Hierdie blog word gemodereer om strooipos, trolling en versoeke van hierdie regeringswebwerf te verwyder. Ons doen ons bes om kommentaar so vinnig as moontlik goed te keur.


Is agt genoeg? Nuwe studie werp planeet nege in twyfel, maar kan dit nie doodmaak nie

Die kunstenaar se indruk van die steeds hipotetiese Planet Nine as 'n ysreus wat die middelpunt verduister. [+] Melkweg, met 'n steragtige son in die verte. Die baan van Neptunus word as 'n klein ellips rondom die son getoon.

WIKIMEDIA COMMONS USERS TOMRUEN, NAGUALDESIGN

Ten spyte van al die vooruitgang wat in die mensegeskiedenis plaasgevind het, bly een buitengewone legkaart steeds in ons eie agterplaas: ons is nie seker hoeveel groot planete daar in ons sonnestelsel is nie. Ons huidige generasie teleskope het duisende voorwerpe in die asteroïde en Kuiper-gordel geopenbaar, benewens die agt groot planete en honderde mane. Anderkant die Kuiper-gordel lê die Oort-wolk, en daarbuite is daar nog duisende planete rondom ander sterre, wat honderde miljarde sterre in ons eie sterrestelsel waargeneem het, en sommige

2 triljoen sterrestelsels in die sigbare heelal.

En tog het sterrekundiges die afgelope paar jaar heftig gedebatteer of die agt planete wat ons sien almal daar is, en of daar nie 'n negende (of moontlik selfs meer) buite Neptunus is nie. Ongeveer die afgelope vyf jaar is 'n klein bevolking trans-Neptuniese voorwerpe met ongewone wentelbane ontdek, wat moontlik indirek dui op die teenwoordigheid van 'n groot, massiewe voorwerp baie keer verder van die son af as wat Neptunus is. Die resultaat is egter betwis, aangesien die steekproefgrootte klein is en ongekwantifiseerde onsekerhede bevat.

'N Nuwe referaat, wat op 9 Februarie 2021 in die Planetary Science Journal aanvaar is, het die spreekwoordelike mat uit die sterkste bewyse getrek wat die bestaan ​​van Planet Nine ondersteun. Dit is 'n ingewikkelde en fassinerende verhaal, so kom ons duik reg in.

Baie flou voorwerpe kan opgespoor word met toegewyde astronomiese opnames, maar die vind van 'n klein, flou,. [+] 'n verre voorwerp in ons sonnestelsel word nog moeiliker gemaak deur die probleem met 'weerkaatsde sonlig'. Vir 'n voorwerp wat twee keer so ver as 'n ander is, moet die lig eers twee keer so ver uitgaan, wat beteken dat net 1 / 4de soveel bereik, en dan weer twee keer so ver terugkom, wat lei tot 1/16 van die oorspronklike helderheid. Die 1 / r ^ 4-verhouding vir helderheidsafstand is in hierdie geval katastrofies.

Gedurende die afgelope dekades het ons van net 'n handjievol bekende voorwerpe verder as Neptunus gegaan tot 'n magdom daarvan. Daar is byna 3000 van hulle opgespoor vanaf vroeg in 2021, met ongeveer 70,000 meer wat na verwagting sal bestaan ​​met 'n grootte groter as ongeveer 30 kilometer in deursnee. Die meeste van hulle wentel in 'n skyfagtige verspreiding: die Kuiper-gordel, wat gewoonlik honderde jare neem om die son te wentel. Oor die algemeen is die meeste van hierdie wentelbane:

Die ongefilterde waarheid agter menslike magnetisme, entstowwe en COVID-19

Uitgelê: Waarom hierdie week se 'Strawberry Moon' so laag, so laat en so helder sal wees

Mars, Venus en 'n 'Super Solstice Strawberry Moon' -vonkel in skemer: wat jy hierdie week in die naghemel kan sien

  • in dieselfde rigting as die planete,
  • ellipties van vorm, maar nie uiters langwerpig nie,
  • en wentel binne ongeveer 30 grade van die Aarde-Son-vlak.

'N Paar van hierdie voorwerpe het egter uitsonderlike wentelbane. Sommige het baie hoë neigings, asof dit van buite die vliegtuig van die sonnestelsel kom. Ander is langwerpig, met die "lang" as van die elliptiese baan baie, baie langer as die "kort" as. En 'n paar van hulle het selfs verskeie parameters, gelyktydig, wat hulle buite die normale bereik plaas.

Die groot vraag wat ons moet vra as ons verantwoordelike wetenskaplikes is, is hoekom?

Die buitenste sonnestelsel, anderkant Neptunus, word oorheers deur klein, ysige liggame: die Kuiper-gordel. Die . [+] voorwerpe hier buite is oor die algemeen klein, met Pluto die grootste en met ongeveer 70 000 voorwerpe van 30 km of groter. As daar êrens nog 'n groot massa daar is, kan dit sommige van die bane van hierdie liggame aansienlik beïnvloed.

JOHNS HOPKINS UNIVERSITY TOEGEPASTE FISIKA LABORATORIE / SUIDWESE NAVORSINGSINSTITUUT (JHUAPL / SWRI)

As u 'n groot aantal klein liggame met 'n lae massa in 'n verre baan om 'n baie massiewer liggaam het - soos die voorwerpe in die Kuiper-gordel wat om die son wentel - verwag u ten volle dat daar interaksies tussen hierdie klein liggame gaan wees. Hulle sal swaarwegend met mekaar kommunikeer. Daar sal soms botsings wees en elke keer sal een van hulle migreer.

As u na binne in ons sonnestelsel migreer, kan u swaartekrag kry deur Neptunus. Dit is waar die meerderheid langetydse komete, soos Halley's Comet, vandaan kom, en ook waar Triton - die reuse-maan van Neptunus wat duidelik uit die Kuiper-gordel gevang is - sy oorsprong het. Hierdie klasse voorwerpe kan almal verklaar word met die konvensionele agt planete wat ons ken.

Aan die ander kant kan u voorwerpe vind wat lyk asof hulle deur iets anders "geskop" is: iets wat veel verder as die Kuiper-gordel is, wat duisende jare neem om selfs 'n enkele omwenteling rondom die son te voltooi. As so iets daar is, sou u 'n nuwe, beduidende bevolking van hierdie verre voorwerpe verwag met 'n spesifieke stel ongewone baanparameters. Ons noem dit ETNO's: ekstreme trans-Neptuniese voorwerpe.

Gebaseer op hul wentelparameters, val die meeste voorwerpe van anderkant Neptunus in 'n bekende. [+] kategorieë soos die Kuiper-gordel of die verspreide skyf. Losstaande voorwerpe is skaars, met Sedna miskien die uitsonderlikste voorwerp vir beide die grootte en die wentelparameters. Buiten Neptunus, maar nog steeds in die Kuiper-gordel, is die voorwerpe die vroegste, mees ongerepte oorblyfsels uit die periode van planeetvorming in ons sonnestelsel. Let daarop dat die meeste voorwerpe wat nog bestaan ​​nog nie gevind is nie.

Wikimedia Commons-gebruiker Eurocommuter

Ongeveer 5 jaar gelede het twee Caltech-sterrekundiges - Konstantin Batygin en Mike Brown - besluit om die groeperingseienskappe van 'n stel van hierdie ongewone voorwerpe te bestudeer en te verwag dat dit net lukraak versprei is. Met die agt bekende planete en die grootte-en-massa-verdeling van die Kuiper-gordelvoorwerpe wat ons verwag het, moet ongewone voorwerpe baanparameters hê, soos in watter rigting hul lang asse wys of hoe hul wentelvlakke in lyn is met die aarde-sonvlak , wat ewekansig versprei word.

Maar die ETNO's wat hulle gehad het, alhoewel daar maar 'n paar van hulle was (destyds ongeveer tien), het 'n ander verhaal vertel. In plaas van 'n ewekansige verspreiding vertoon die ongewone voorwerpe wat hulle geïdentifiseer het, groeperingseienskappe wat verband hou. Die kans dat hierdie ETNO's ewekansig sou saamgevoeg word soos dit gevind is, was nie net laag nie, dit was opmerklik onwaarskynlik: soos een-uit-duisende onwaarskynlik.

U sou waarskynlik nie u lewe op hierdie kans wed nie, maar daar was 'n moontlike fisiese verklaring hiervoor waarop u sou kon wed: 'n massiewe planeet, miskien tussen die massa van die Aarde en Neptunus, wat baie verder as selfs die rand van die Kuiper-gordel.

In teorie sal Planet Nine waarskynlik soortgelyk wees aan die eksoplanet 55 Cancri e, wat ongeveer is. [+] twee keer die Aarde se radius, maar agt keer die Aarde se massa. Hierdie nuwe studie verontagsaam egter die bestaan ​​van so 'n wêreld in ons buitenste sonnestelsel.

'N Voorwerp wat hierdie massiewe, selfs so ver weg is, sou voldoende wees om sy baan gedurende die leeftyd van die Sonnestelsel skoon te maak, wat dit volgens die definisie van die Internasionale Astronomiese Unie 'n bona fide planeet maak. Hoe ironies: dieselfde definisie wat Pluto amptelik in 2006 "gedegradeer" het, bevorder miskien nou 'n nuwe, voorheen onvoorsiene liggaam tot die status van "Planet Nine", maar hierdie keer goed!

Natuurlik is daar twee goeie maniere om op te volg:

  1. Die direkte roete. As daar 'n groot, massiewe voorwerp daar is, selfs so ver van die son af, moet dit moontlik gevind word. Op die oomblik is daar, op grond van die indirekte data wat ons het, 'n baie groot soekgebied waar die hipotetiese Planet Nine kan wees, en slegs die grootste grondteleskope kan dit direk beeld. Tot dusver geen geluk nie.
  2. Die indirekte roete. Vermoedelik, as daar 'n negende planeet daar is, moet die aanvanklike ETNO's wat gebruik word om die bestaan ​​van Planet Nine af te lei, 'n klein steekproef wees van 'n veel groter aantal liggame. Met beter, dieper, meer omvattende opnames, moet ons in staat wees om baie meer van hierdie ongewone voorwerpe te vind, en hulle moet dieselfde groepering vertoon - eerder as ewekansige groepering - as Planet Nine bestaan.

Die wentelbane van die geselekteerde TNO's deur Batygin en Brown, tesame met die voorgestelde Planet Nine. In die. [+] verre toekoms sal Planet Nine - waarvan die begin baie kontroversieel is - nie eers voldoende temperature bereik om potensieel bewoonbaar te word as die son 'n rooi reuse-ster word nie.

K. Batygin en M. E. Brown Astronom. J. 151, 22 (2016), met wysigings / toevoegings deur E. Siegel

U mag dalk aan die tier kom en iets vra soos: 'Oke, nou ja, dit is ongeveer vyf jaar gelede, en ons het niks direk gevind nie, maar ons moet beslis meer voorwerpe hê - ETNO's, of hoe? - wat nou in hierdie 'ongewone' kategorie val. So, wat wys hulle? ' Voordat ek u egter kan vertel dat ek wil hê dat u iets moet besef: dit is moontlik dat hierdie aanvanklike populasie voorwerpe, ten spyte van wat ons waargeneem het, eintlik glad nie gekluster kan wees nie.

Dink hieraan: daar is 'n groot lug daar buite, ongeveer 40.000 vierkante grade in totaal. As u na verre voorwerpe in die buitenste sonnestelsel soek, in die hoop om hul wentelbane te bepaal, moet u:

  1. let op hierdie flou, verre voorwerp,
  2. beeld dit verskeie kere oor 'n tydperk van twee tot vier jaar,
  3. volg hoe dit beweeg relatief tot die agtergrond van vaste sterre,
  4. en dan eers kan jy hul wentelbane bepaal.

Dit is waar: ons het die afgelope paar jaar baie meer voorwerpe buite Neptunus ontdek deur middel van verskeie onafhanklike opnames, soos OSSOS (Outer Solar System Origins Survey) en die Dark Energy Survey se DECam-instrument. Maar wat ons sien, vertel ons nie wat ons eintlik het nie.

Vier van die Trans-Neptuniese voorwerpe wat deur OSSOS gevind is, getoon saam met die baan van Neptunus ter vergelyking. . [+] Die OSSOS-voorwerpe vertoon nie dieselfde korrelasies as die vorige wat deur die Planet Nine-span geïdentifiseer is nie, maar was dit te wyte aan lae statistieke, of was dit te wyte aan die akkurate boekhouding van hul keuse-vooroordeel?

C. Shankman et al., ArXiv: 1706.05348v2

Die rede hiervoor word in die sterrekunde as vooroordeel bekend. Daar is baie verskillende maniere waarop u resultate bevooroordeeld kan wees. As jy met jou blote oog na die hemelhemel kyk, sien jy die helderste sterre soos gesien vanaf die aarde. Die meeste van hierdie sterre is intrinsiek helder, maar baie ver is 'n paar intrinsiek flouer, maar betreklik naby. Die oorgrote meerderheid sterre is te flou om met die blote oog gesien te word, maar selfs die naaste ster aan ons, Proxima Centauri, benodig 'n teleskoop van aansienlike omvang! In sterrekunde noem ons hierdie Malmquist-vooroordeel: ons is bevooroordeeld teenoor die voorwerpe wat die maklikste is om te sien.

Hier is 'n ander soort vooroordeel: spelvooroordeel. U kan slegs die voorwerpe waarneem wat sal verskyn wanneer en waar u teleskope kyk! Faktore soos:

  • waar is jou teleskoop op die aarde geleë,
  • waarheen wys dit,
  • wanneer het jy waargeneem,
  • hoe lank het u waargeneem (wat help om te bepaal hoe flou u kan sien),
  • en ander faktore soos in watter filter / band u waargeneem het,

kan almal 'n rol speel in die bepaling van wat u sien. Onrusbarend is dat die gevolge van die voorwerpe wat in die aanvanklike studie tot die gevolgtrekking gekom het dat Planet Nine bestaan, kon bestaan ​​- die opname van Sheppard en Trujillo - het hul seleksievooroordeel nie gekwantifiseer nie.

Die 3D-bane van die voorwerpe van die Kuiper-gordel beïnvloed deur Planet Nine. Soos Mike Brown gesê het: 'Die verre. [+] voorwerpe met wentelbane om die sonnestelsel is voorspel deur die Planet Nine-hipotese. En toe vyf minute later gevind. ' Maar dit kon net ontdek word as gevolg van waar die goeie data bestaan.

Mike Brown / http://www.findplanetnine.com/

Maar die OSSOS-opname het gedoen! Vanaf 2017 het hulle hul eerste bevindings van hierdie ongewone, ekstreme trans-Neptuniese voorwerpe (ETNO's) gepubliseer, en kon hulle rekord hou van seleksievooroordeel. Toe hulle dit gedoen het, het dit baie kontroversie ontketen, want as u rekening hou met vooroordeel van die seleksie, is daar geen beduidende bewyse vir Planet Nine nie. Aan die ander kant, as u moenie neem rekening met seleksievooroordeel, en kyk net na die data daarsonder - veral as u dit kombineer met die Sheppard- en Trujillo-data - daar is nog steeds baie sterk bewyse vir Planet Nine!

Laat ons dus vinnig vorentoe gaan na die hede. Daar is nou drie relevante opnames, aangesien die data van Sheppard en Trujillo en OSSOS bygevoeg word deur die DECam-data, en 'n totaal van miskien 'n paar dosyn van hierdie voorwerpe. Wat u ideaal sou kon doen, is om deur al die opnames te gaan kyk en uit te vind waar dit gekyk het, wanneer dit gekyk het en hoe lank dit gesoek het: die groot faktore waarmee u u keusevooroordeel kan kwantifiseer. . As u dit kan doen, kan u dit wat u gesien het op 'n lukrake manier op 'n verantwoordelike manier vergelyk.

Daarom is hierdie nuwe referaat so opwindend: danksy die ongelooflike werk van die gegradueerde student aan die Universiteit van Michigan, Kevin Napier, is die voorkeur vir al drie hierdie opnames gekwantifiseer.

Die seleksiefunksie vir ekstreme trans-Neptuniese voorwerpe met ontdekte voorwerpe getoon. Waar die . [+] wit punte stem ooreen met waar die teleskope gewys het / waargeneem waar die rooi punte ooreenstem met waar voorwerpe gevind is. Die groepering stem ooreen met waar ons gekyk het, sonder enige bykomende effekte.

K.J. Napier et al., ArXiv: 2102.05601

Die foto wat u hierbo sien - Figuur 6 van die papier - toon aan waar die waarnemings met die wit strepe en die kolletjies die sensitiefste is vir voorwerpe wat verskyn, en die rooi punte die voorwerpe toon wat eintlik gevind en gekies is as die fisiese interessante. Die rooi punte is die gegewens wat ons het. Die wit gebied verteenwoordig die relatiewe waarskynlikheid om voorwerpe op daardie plekke te vind.

Verrassing, verrassing: die data is gegroepeer op die plekke waarheen ons gekyk het, en nie by voorkeur op die plekke waar ons nie gekyk het nie. Waarna hulle gekyk het, was: "hoe vol vertroue kan ons 'n nie-gegroepeerde sonnestelsel uitsluit?" Vorige werk in 2019 het dit uitgesluit op die 99,8% vertrouensvlak: dit is redelik selfversekerd! Maar in die nuwe koerant kon hulle dit net uitsluit by die

83% vertrouensvlak, wat beteken dat daar iets soos 'n een-uit-ses-kans is dat dit lukraak kan wees. That’s not particularly compelling, and might reasonably considered enough to greatly weaken the motivation to continue the search for Planet Nine.

But this does not mean that Planet Nine is dead, not by any means. If we want to understand the distribution of these ETNOs — these exceptional, extreme, objects — we really need to have good data on hundreds of them, not

20 or so. It’s still possible that the objects really are clustered, and that the clustering is due to a distant, massive planet, and just happen to be clustered in the directions we observed. Without more comprehensive, better data, we simply cannot know.

If you were to look 'down' on our Solar System, these are the extreme trans-Neptunian objects you'd . [+] see. They can only be seen when they're closest to the Sun at certain times of the year, and this 'selection bias' may be the cause of the apparent clustering, not an additional planet.

Michele Bannister / @astrokiwi

It’s eminently possible that this new analysis, rather than reducing the strength of the signal in support of clustering, simply increases the uncertainties to such a level that a very real signal no longer stands out from the noise. With the data we have in hand today, it isn’t enough to decide the issue, either in favor of or opposition to the existence of an additional planet beyond Neptune. Still, it’s a remarkable study and a remarkable advance, and the quantification of selection bias brings us one important step closer to understanding what’s out there beyond the limits of where our telescopes can presently reach.

Hopefully, with the advent of new ground-based and space-based telescopes on the way, and the Vera Rubin Observatory in particular, we’ll either find Planet Nine or rule it out entirely. Whether it exists or not is for the Universe to decide, but finding it and understanding what’s occurring in the outer reaches of our Solar System is entirely up to us.


The Earth’s Second Moon, 1846-present

In 1846, Frederic Petit, director of the observatory of Toulouse, stated that a second moon of the Earth had been discovered. It had been seen by two observers, Lebon and Dassier, at Toulouse and by a third, Lariviere, at Artenac, during the early evening of March 21 1846. Petit found that the orbit was elliptical, with a period of 2 hours 44 minutes 59 seconds, an apogee at 3570 km above the Earth’s surface and perigee at just 11.4 km (!) above the Earth’s surface. Le Verrier, who was in the audience, grumbled that one needed to take air resistance into account, something nobody could do at that time. Petit became obsessed with this idea of a second moon, and 15 years later announced that he had made calculations about a small moon of Earth which caused some then-unexplained peculiarities in the motion of our main Moon. Astronomers generally ignored this, and the idea would have been forgotten if not a young French writer, Jules Verne, had not read an abstract. In Verne’s novel “From the Earth to the Moon”, Verne lets a small object pass close to the traveller’s space capsule, causing it to travel around the Moon instead of smashing into it:

“It is”, said Barbicane, “a simple meteorite but an enormous one, retained as a satellite by the attraction of the Earth.”

“Is that possible?”, exclaimed Michel Ardan, “the earth has two moons?”

“Yes, my friend, it has two moons, although it is usually believed to have only one. But this second moon is so small and its velocity is so great that the inhabitants of Earth cannot see it. It was by noticing disturbances that a French astronomer, Monsieur Petit, could determine the existence of this second moon and calculated its orbit. According to him a complete revolution around the Earth takes three hours and twenty minutes. . . . “

“Do all astronomers admit the the existence of this satellite?”, asked Nicholl

“No”, replied Barbicane, “but if, like us, they had met it they could no longer doubt it. . . . But this gives us a means of determining our position in space . . . its distance is known and we were, therefore, 7480 km above the surface of the globe where we met it.”

Jules Verne was read by millions of people, but not until 1942 did anybody notice the discrepancies in Verne’s text:

  1. A satellite 7480 km above the Earth’s surface would have a period of 4 hours 48 minutes, not 3 hours 20 minutes.
  2. Since it was seen from the window from which the Moon was invisible, while both were approaching, it must be in retrograde motion, which would be worth remarking. Verne doesn’t mention this.
  3. In any case the satellite would be in eclipse and thus be invisible. The projectile doesn’t leave the Earth’s shadow until much later.

Dr. R.S. Richardson, Mount Wilson Observatory, tried in 1952 to make the figures fit by assuming an eccentric orbit of this moon: perigee 5010 km and apogee 7480 km above Earth’s surface, eccentricity 0.1784.

Nevertheless, Jules Verne made Petit’s second moon known all over the world. Amateur astronomers jumped to the conclusion that here was opportunity for fame — anybody discovering this second moon would have his name inscribed in the annals of science. No major observatory ever checked the problem of the Earth’s second moon, or if they did they kept quiet. German amateurs were chasing what they called Kleinchen (“little bit”) — of course they never found Kleinchen.

W. H. Pickering devoted his attention to the theory of the subject: if the satellite orbited 320 km above the surface and if its diameter was 0.3 meters, with the same reflecting power as the Moon, it should be visible in a 3-inch telescope. A 3 meter satellite would be a unaided-eye object of magnitude 5. Though Pickering did not look for the Petit object, he did carry on a search for a secondary moon — a satellite of our Moon (“On a photographic search for a satellite of the Moon”, Popular Astronomy, 1903). The result was negative and Pickering concluded that any satellite of our Moon must be smaller than about 3 meters.

Pickering’s article on the possibility of a tiny second moon of Earth, “A Meteoritic Satellite”, appeared in Popular Astronomy in 1922 and caused another short flurry among amateur astronomers, since it contained a virtual request: “A 3-5-inch telescope with a low-power eyepiece would be the likeliest mean to find it. It is an opportunity for the amateur.” But again, all searches remained fruitless.

The original idea was that the gravitational field of the second moon should account for the then inexplicable minor deviations of the motion of our big Moon. That meant an object at least several miles large — but if such a large second moon really existed, it would have been seen by the Babylonians. Even if it was too small to show a disk, its comparative nearness would have made it move fast and therefore be conspicuous, as today’s watchers of artificial satellites and even airplanes know. On the other hand, nobody was much interested in moonlets too small to be seen.

There have been other proposals for additional natural satellites of the Earth. In 1898 Dr Georg Waltemath from Hamburg claimed to have discovered not only a second moon but a whole system of midget moons. Waltemath gave orbital elements for one of these moons: distance from Earth 1.03 million km, diameter 700 km, orbital period 119 days, synodic period 177 days. “Sometimes”, says Waltemath, “it shines at night like the Sun” and he thinks this moon was seen in Greenland on 24 October 1881 by Lieut Greely, ten days after the Sun had set for the winter. Public interest was aroused when Waltemath predicted his second moon would pass in front of the Sun on the 2nd, 3rd or 4th of February 1898. On the 4th February, 12 persons at the post office of Greifswald (Herr Postdirektor Ziegel, members of his family, and postal employees) observed the Sun with their unaided eye, without protection of the glare. It is easy to imagine a faintly preposterous scene: an imposing-looking Prussian civil servant pointing skyward through his office window, while he reads Waltemath’s prediction aloud to a knot of respectful subordinates. On being interviewed, these witnesses spoke of a dark object having one fifth the Sun’s apparent diameter, and which took from 1:10 to 2:10 Berlin time to traverse the solar disk. It was soon proven to be a mistake, because during that very hour the Sun was being scrutinized by two experienced astronomers, W. Winkler in Jena and Baron Ivo von Benko from Pola, Austria. They both reported that only a few ordinary sunspots were on the disk. The failure of this and later forecasts did not discourage Waltemath, who continued to issue predictions and ask for verifications. Contemporary astronomers were pretty irritated over and over again having to answer questions from the public like “Oh, by the way, what about all these new moons?”. But astrologers caught on — in 1918 the astrologer Sepharial named this moon Lilith. He considered it to be black enough to be invisible most of the time, being visible only close to opposition or when in transit across the solar disk. Sepharial constructed an ephemeris of Lilith, based on several of Waltemath’s claimed observations. He considered Lilith to have about the same mass as the Moon, apparently happily unaware that any such satellite would, even if invisible, show its existence by perturbing the motion of the Earth. And even to this day, “the dark moon” Lilith is used by some astrologers in their horoscopes.

From time to time other “additional moons” were reported from observers. The German astronomical magazine “Die Sterne” reported that a German amateur astronomer named W. Spill had observed a second moon cross our first moon’s disc on May 24, 1926.

Around 1950, when artificial satellites began to be discussed in earnest, everybody expected them to be just burned-out upper stages of multistage rockets, carrying no radio transmitters but being tracked by radar from the Earth. In such cases a bunch of small nearby natural satellites would have been most annoying, reflecting radar beams meant for the artificial satellites. The method to search for such natural satellites was developed by Clyde Tombaugh: the motion of a satellite at e.g. 5000 km height is computed. Then a camera platform is constructed that scans the sky at precisely that rate. Stars, planets etc will then appear as lines on the photographs taken by this camera, while any satellite at the correct altitude will appear as a dot. If the satellite was at a somewhat different altitude, it would produce a short line.

Observations began in 1953 at the Lowell Observatory and actually invaded virgin territory: with the exception of the Germans searching for “Kleinchen” nobody had ever paid attention to the space between the Moon and the Earth! By the fall of 1954, weekly journals and daily newspapers of high reputation stated that the search had brought its first results: one small natural satellite at 700 km altitude, another one 1000 km out. One general is said to have asked: “Is he sure they’re natural?”. Nobody seems to know how these reports originated — the searches were completely negative. When the first artificial satellites were launched in 1957 and 1958, the cameras tracked those satellites instead.

But strangely enough, this does not mean that the Earth only has one natural satellite. The Earth can have a very near satellite for a short time. Meteoroids passing the Earth and skimming through the upper atmosphere can lose enough velocity to go into a satellite orbit around the Earth. But since they pass the upper atmosphere at each perigee, they will not last long, maybe only one or two, possibly a hundred revolutions (about 150 hours). There are some indications that such “ephemeral satellites” have been seen it is even possible that Petit’s observers did see one. (see also)

In addition to ephemeral satellites there are two more possibilities. One is that the Moon had a satellite of its own — but despite several searches none has been found (in addition it’s now known that the gravity field of the Moon is uneven or “lumpy” enough for any lunar satellite orbit to be unstable — any lunar satellite will therefore crash into the Moon after a fairly short time, a few years or possibly a decade). The other possibility is that there might be Trojan satellites, i.e. secondary satellites in the lunar orbit, travelling 60 degrees ahead of or behind the Moon.

Such “Trojan satellites” were first reported by the Polish astronomer Kordylewski of Krakow observatory. He started his search in 1951, visually with a good telescope. He was hoping for reasonably large bodies in the lunar orbit, 60 degrees away from the Moon. The search was negative, but in 1956 his compatriot and colleague, Wilkowski, suggested that there may be many tiny bodies, too small to be seen individually but many enough to appear as a cloud of dust particles. In such a case, they would be best visible without a telescope i.e. with the unaided eye! Using a telescope would “magnify it out of existence”. Dr Kordylewski was willing to try. A dark night with clear skies, and the Moon being below the horizon, was required.

In October 1956, Kordylewski saw, for the first time, a fairly bright patch in one of the two positions. It was not small, subtending an angle of 2 degrees (i.e. about 4 times larger than the Moon itself), and was very faint, only about half as bright as the notoriously difficult Gegenschein (counterglow — a bright patch in the zodiacal light, directly opposite to the Sun). In March and April 1961, Kordylewski succeeded in photographing two clouds near the expected positions. They seem to vary in extent, but that may be due to changing illumination. J. Roach detected these cloud satellites in 1975 with the OSO (Orbiting Solar Observatory) 6 spacecraft. In 1990 they were again photographed, this time by the Polish astronomer Winiarski, who found that they were a few degrees in apparent diameter, that they “wandered” up to ten degrees away from the “trojan” point, and that they were somewhat redder than the zodiacal light.

So the century-long search for a second moon of the Earth seems to have succeeded, after all, even though this ‘second moon’ turned out to be entirely different from anything anybody had ever expected. They are very hard to detect and to distinguish from the zodiacal light, in particular the Gegenschein.

But people are still proposing additional natural satellites of the Earth. Between 1966 and 1969 John Bargby, an American scientist, claimed to have observed at least ten small natural satellites of the Earth, visible only in a telescope. Bargby found elliptical orbits for all the objects: eccentricity 0.498, semimajor axis 14065 km, which yields perigee and apogee heights of 680 and 14700 km. Bargby considered them to be fragments of a larger body which broke up in December 1955. He based much of his suggested satellites on supposed perturbations of artificial satellites. Bargby used artificial satellite data from Goddard Satellite Situation Report, unaware that the values in this publication are only approximate and sometimes grossly in error and can therefore not be used for any precise scientific analysis. In addition, from Bargby’s own claimed observations it can be deduced that when at perigee Bargby’s satellites ought to be visible at first magnitude and thus be easily visible to the unaided eye, yet no-one has seen them as such.

In 1997, Paul Wiegert (et al) discovered that the near-Earth asteroid 3753 Cruithne has a very strange orbit and can be considered a companion to Earth, though it certainly does not orbit the Earth directly. 2002 AA29 also has a special relationship with Earth.


No Planet Nine? Small-body Pile-up Could Explain Odd Orbits

By: Javier Barbuzano June 11, 2018 3

Get Articles like this sent to your inbox

New research shows that interactions between small objects beyond Neptune’s orbit —and not a hypothetical Planet Nine — could be the reason some far-flung solar system objects “detach” from their original orbits.

Astronomers have been struggling to explain the orbits of 30 or so bodies at the outer rims of the solar system, called “detached objects.” These worlds are smaller than Pluto and travel in elliptical trajectories around the Sun.

An artist's rendering of Sedna, which looks reddish in color in telescope images.
NASA / JPL-Caltech

Sedna is one of the most well-known detached objects: a reddish world found in 2003, it’s one-third the size of the Moon and has an orbital period of 11,400 years — the longest of any object known in the solar system. At closest approach it passes 76 times farther away than the distance between the Sun and Earth. At its farthest, it goes more than 900 times that distance.

The orbits of Sedna and the other detached objects appear to be completely removed from Neptune’s gravitational pull. Yet their trajectories share similarities that seem to point to a common but unknown source of gravitational influence. For that reason astronomers have pointed to the influence of a yet-to-be-found ninth planet of the solar system, hiding far beyond Pluto’s orbit. Astronomers have proposed the existence of this alleged planet to explain not only the detachment of these objects’ orbits, but also other characteristics, such as their orbits’ tilt relative to the plane where most of the planets of the solar system reside.

These panels show the location of Sedna with respect to the rest of the solar system. Moving clockwise, each panel zooms successively outward. The first panel shows the orbits of the inner planets and the asteroid belt. In the second panel, Sedna is shown well outside the orbits of the outer planets and the more distant Kuiper Belt objects. Sedna's full orbit is illustrated in the third panel along with the object's current location. The final panel zooms out much farther, showing that even this large elliptical orbit falls inside the inner edge of the Oort cloud.
NASA / JPL-Caltech

But Planet Nine isn’t the only plausible source of disruption in our system’s outskirts. A group of researchers led by Ann-Marie Madigan and Jacob Fleisig (both at University of Colorado, Boulder) have found that the combined gravitational pull of the many smaller bodies beyond Neptune’s orbit (known as trans-Neptunian objects, or TNOs) could do the trick. Thanks to computer simulations, they have found that the combined gravity of the smaller TNOs could push the larger members of their family — such as Sedna — into detached orbits. The researchers presented their findings on June 6th at the 232nd meeting of the American Astronomical Society.

According to Fleisig, the key to this mechanism is the precession of the TNO orbits. If all the objects were the same size, their orbits would move at the same rate and stay stable. But the team’s simulations showed that the larger bodies’ orbits revolve around the Sun more slowly than their smaller counterparts. The motion is similar to the hands of a clock, where the minute hand catches up with the hour hand. When that happens, the larger body feels the gravity of its smaller counterparts piling up behind it. Their combined pull changes the largest object’s path, pushing it away from the Sun.

“For this mechanism to work you need a significant amount of objects out there,” Fleisig says.

That raises the question: Is there enough mass in the outer solar system to make this happen? To Fleisig and his team, the answer is yes. “If we look at the objects that have been detected so far, there’s just a handful of them,” Fleisig says. “We wouldn’t have found them in the time scales that humans have been looking at the sky if that was all there was out there.”

Hal Levison (Southwest Research Institute) says he likes this idea but will remain cautious until the group publishes their work in a peer-reviewed paper, which is currently in preparation. “This could be a really big deal,” Levison says. Nevertheless, he warns, there might be something in the simulations that is “not likely to happen in nature.”

One of the main proponents of the existence of “Planet Nine,” astronomer Mike Brown (Caltech), agrees that the new work puts forward a way to detach objects’ orbits. But he doesn’t think the work rules out the existence of “Planet Nine.” The detachment of the orbits was more a “side effect” of the existence of the rogue planet than the reason to look for it, he argues. “The mechanism discussed here doesn't actually create any of the main effects of Planet Nine, including lining up the orbits, tilting the orbital planes, and generating a population of high-inclination nearby objects,” Brown says. According to Brown, Planet Nine is still required to cause all of these major effects.

However, findings like this may put a bit more of pressure on the supporters of Planet Nine and those actively looking for it. “It’s become a moving target,” Levison says, “I’m very skeptical.” Then he adds, “but not to the point to say we shouldn’t look for it.”


Making the Case for "Planet Nine"

By: J. Kelly Beatty January 20, 2016 19

Get Articles like this sent to your inbox

Does a massive, extremely distant planet orbit the Sun? A new analysis of distant solar-system orbits argues that it should exist.

It's been almost a century since self-made astronomer Percival Lowell died. He famously predicted the existence of a "Planet X" beyond Neptune, which led to a search effort at Lowell Observatory, which in turn led to the hiring of Clyde Tombaugh, which . . . well, you know the rest of the story.

The hypothesized "Planet Nine" would average about 100 billion km away and take 10,000 to 20,000 years to orbit the Sun.
Caltech / Robert Hurt

Now a new, prediction-driven search for a massive, distant planet is under way, spurred by orbital quirks among some of the solar system's most distant objects. That search will be accelerated thanks to a new analysis that provides circumstantial evidence for a seriously big, yet-to-be-discovered planet very far from the Sun.

Writing in February's Astronomical Journal, Konstantin Batygin and Michael Brown (Caltech) describe how Kuiper Belt objects that average at least 150 a.u. from the Sun and never come closer than about 50 a.u. share an interesting dynamical property. They have perihelia, the point of their orbits closest to the Sun, that all cluster near the ecliptic plane — and they're all moving south to north when they pass through perihelion. (For the future interplanetary navigators among you, this orbital parameter is termed argument of perihelion.)

It's more than just a quirk coincidence, and this clustering started to get lots of attention after the discovery of the object 2012 VP113 a few years ago. In announcing that find, Chadwick Trujillo (Gemini Observatory) and Scott Sheppard (Carnegie Institution for Science) noted the perihelic similarity of 2012 VP113, 90377 Sedna, and 10 other bodies. Moreover, these objects orbit in a kind of dynamical "no man's land" that defies easy explanations for how they got there. They conclude that a massive planet, even farther out, could have been responsible. I wrote a long blog about all of this in 2014.

Orbits for the six most distant known objects in the solar system, whose orbits (shown in magenta) remain beyond Neptune), all align in one direction. A hypothesized massive "Planet Nine" (orange orbit) could be responsible for their perplexing alignment.
Caltech / Robert Hurt

Batygin and Brown have taken this idea to the next level. Their analysis shows that the solar system's six most-distant objects not only have clustered perihelia but also follow elliptical orbits oriented the same way in space, angled below the ecliptic plane by about 30°. All told, these six orbits are so similar that there's only a 0.007% chance of this having occurred by chance. Moreover, these copycat orbits couldn't simply be a holdover from the solar system's formation. Over time, subtle perturbations from the giant planets would cause them to slowly drift apart. Something must be actively keeping them corralled.

Recent analysis shows that the particular perturbation mechanism envisioned by Trujillo and Sheppard, which assumed a big body in a very distant, circular orbit, won't work. Instead, Batygin and Brown invoke a massive hypothetical body in a highly eccentric orbit, which they've nicknamed "Planet Nine," to impose this order. It would have a perihelion roughly 300 a.u. away and would naturally explain not only the clustered perihelia but also the dynamically puzzling orbits of Sedna and its kin.

"Planet Nine" wouldn't have jerked all these other bodies into orbital submission all at once, via dramatic close-call encounters. Rather, over time its mass would gradually perturb objects like Sedna into confined orbits via resonances — much as Neptune has captured Pluto into a 3:2 resonance (that is, Neptune completes three orbits in the time Pluto takes to go around twice).

And how did this proposed planet manage to form so far from the Sun? Most likely it didn't. Batygin and Brown suggest it's a castoff — a body that formed much, much closer in and got ejected outward by Jupiter or perhaps by the Sun itself.

So Where is "Planet Nine"?

Black lines show the range of possible locations and observing characteristics for the putative "Planet Nine." (Red lines delineate the Milky Way blue line is the ecliptic.)
Konstantin Batygin & Mike Brown

If Batygin and Brown are right, this object must have at least 10 times Earth's mass (2 to 4 times its diameter) and occupy a highly elongated orbit that perhaps averages about 700 astronomical units (100 billion kilometers) from the Sun. Actually, a wide range of orbits are possible, as shown at right, and there's no way to know where the putative object might now lie along that orbit — whose period might be 10,000 to 20,000 years.

"Surely," I can sense you thinking, "such a large object would have been discovered by now." Well, probably not. When closest to the Sun, it wouldn't be particularly faint. But the elongated orbit means that most of the time it lingers far from perihelion. So odds are it's near aphelion and around magnitude 22 — beyond the range of most telescopic surveys to date.Worse, the predicted aphelion region corresponds to a portion of the sky that includes the Milky Way and that hasn't yet been covered by major surveys.

Meanwhile, Kevin Luhman (Penn State University) has already looked for distant planets using observations from NASA's Wide-field Infrared Survey Explorer (WISE), which would be sensitive to the heat a big body radiates to space. The problem is that a distant "Jupiter" or "Saturn" should be quite warm, whereas a 10-Earth-mass "mini-Neptune" wouldn't. Now Luhman is checking a limited set of WISE observations made at longer infrared wavelengths, covering only about 20% of the sky, that just might reveal a smaller, cooler object.

Even if the proposed "Planet Nine" is never seen directly, the circumstantial case for its existence might be strengthened once we've discovered more very distant Kuiper Belt objects and assessed their orbital distribution.

You can check out the Batygin-Brown paper here, but be forewarned it's dense with higher-order math. You might find the going a little easier by reading Caltech's press release.


Shift-Stacking the Night Away

Editor’s note: Astrobites is a graduate-student-run organization that digests astrophysical literature for undergraduate students. As part of the partnership between the AAS and astrobites, we occasionally repost astrobites content here at AAS Nova. We hope you enjoy this post from astrobites the original can be viewed at astrobites.org.

The Transiting Exoplanet Survey Satellite (TESS), which just recently finished its primary mission to search for planets around nearby, bright stars, has also provided a treasure trove of other information for astronomers. As it stares at the sky, waiting to catch the brief flicker of a distant planet passing in front of its host star, TESS’s steady, unwavering gaze catches everything from stellar pulsations, to gamma-ray bursts, to distant solar system objects tumbling through the dark.

Artist’s rendering of the hypothetical Planet Nine in the outskirts of our solar system. [Caltech/R. Hurt, IPAC]

10x as distant as Neptune, “Planet Nine” would appear incredibly faint, due to the small amount of sunlight that reaches it. Furthermore, if it happens to lie near the star-studded galactic plane on the sky, it would be incredibly difficult to pick out in images.

An image of Planet Nine could be in some of the many exposures that TESS has already taken, although likely not in plain sight. Given that TESS takes 30-minute exposures of each patch of sky, the signal from our distant solar system companion would probably be extremely weak and hard to detect. One way around this issue is to “stack” multiple exposures on top of each other. This acts to boost the signal from any faint sources in an image above any background noise from the camera. Unfortunately, even the most distant solar system bodies move across the TESS field of view between exposures. Because the object is in a different place in each image, you lose any benefit from simply stacking the images on top of each other in place.

To solve this problem, the authors of today’s paper make use of a clever technique called “shift stacking”. Although an object will appear at a different location on each exposure, one can shift the sequence of exposures in such a way that the same pixels on each image correspond to the location of the object. By doing so, the images can then be stacked and added together and an object too faint to be visible in a single image now pops out.

Figure 1: Top: An illustration of the process by which a series of images, taken at different times, are combined to convert a faint, moving source into a much brighter, single point. Bottom: When searching for an undetected source, the path on the image is unknown. In this case, the algorithm must try out different guesses for the correct trajectory. The “correct” path is the one that produces the strongest signal on the final image. [Rice & Laughlin 2020]

Trying to guess the correct path for an undetected object can be slow ordeal. One simplification, however, makes this task much easier to conquer. Most outer solar system objects move incredibly slowly because they are so far from the Sun. They move so slowly, in fact, that their motion on the sky is almost entirely dominated by the Earth’s motion. This fact really helps to narrow down the range of possible guesses for the path of any undetected body. Because the Earth’s motion dominates, a body’s path across the images depends only on its distance from the Sun, and not on the specific shape of its orbit.

Figure 2: An application of the shift-stacking technique to three previously known outer solar system bodies: Sedna (top), 2015 BP519 (middle) and TG 422 (bottom). In the leftmost column, the known orbital parameters are used to calculate the trajectory of the object on the image. Next, the trajectory of the object is guessed using both a polynomial (middle) and PCA (right) technique to model the baseline flux. In all cases, the objects are recovered. [Rice & Laughlin 2020]

Next, the authors attempt to recover these three outer solar system bodies without telling the algorithm ahead of time about the trajectories of these bodies. Instead, the algorithm tries to guess the path by maximizing the brightness of the point source in the shift-stacked images. This is shown in the middle and right hand columns of Figure 2. Here, “polynomial” and “PCA” refer to the technique used to subtract the baseline flux from the images. Although the polynomial technique is less computationally expensive, it sometimes results in the object itself being removed from the images.

Lastly, the authors apply their blind search algorithm to TESS sectors 18 and 19. Although this is only a small piece of the observing footprint of the telescope, these two sectors partially overlap with the galactic plane, which is where the shift-stacking technique is particularly useful. In total, the authors provide a list of 17 new outer solar system body candidates, which will need to be followed up with ground-based observations to confirm. From the TESS images, the distance, brightness, and size of the objects are estimated. Unfortunately, none appear anywhere near as large as what is expected for the hypothetical planet nine. It is, however, exciting that this technique finds so many new candidate objects from such a small search area. Presently, there are only about 100 known distant outer solar system bodies! Although this technique is quite computationally expensive to run, a more clever implementation that involves convolutional neural networks could allow this to be run on the entire sky.

Original astrobite edited by Bryanne McDonough.

About the author, Spencer Wallace:

I’m a member of the UW Astronomy N-body shop working with Thomas Quinn to study simulations of planet formation. In particular, I’m interested in how this process plays out around M stars, which put out huge amounts of radiation during the pre main-sequence phase and are known to host extremely short period planets. When I’m not thinking about planet formation, I’m an avid hiker/backpacker and play bass for the band Night Lunch.


Planet Nine Could Be Our Solar System's Missing 'Super Earth'

Planet Nine is out there, and astronomers are determined to find it, according to a new statement from NASA. In fact, mounting evidence suggests it's hard to imagine our solar system without the unseen world.

The hypothetical planet is believed to be about 10 times more massive than Earth and located in the dark, outer reaches of the solar system, approximately 20 times farther from the sun than Neptune is. While the mysterious world still has yet to be found, astronomers have discovered a number of strange features of our solar system that are best explained by the presence of a ninth planet, according to the NASA statement.

"There are now five different lines of observational evidence pointing to the existence of Planet Nine," Konstantin Batygin, a planetary astrophysicist at the California Institute of Technology (Caltech) in Pasadena, said in the statement. "If you were to remove this explanation and imagine Planet Nine does not exist, then you generate more problems than you solve. All of a sudden, you have five different puzzles, and you must come up with five different theories to explain them." [The Evidence for 'Planet Nine' in Our Solar System (Gallery)]

In 2016, Batygin and co-author Mike Brown, an astronomer at Caltech, published a study that examined the elliptical orbits of six known objects in the Kuiper Belt, a distant region of icy bodies stretching from Neptune outward toward interstellar space. Their findings revealed that all of those Kuiper Belt objects have elliptical orbits that point in the same direction and are tilted about 30 degrees "downward" compared to the plane in which the eight official planets circle the sun, according to the statement.

Using computer simulations of the solar system with a Planet Nine, Batygin and Brown also showed that there should be even more objects tilted a whopping 90 degrees with respect to the solar plane. Further investigation revealed that five such objects were already known to fit these parameters, the researchers said.

Since then, the astronomers have found new evidence that further supports the existence of Planet Nine. With help from Elizabeth Bailey, an astrophysicist and planetary scientist at Caltech, the team showed that Planet Nine's influence might have tilted the planets of our solar system, which would explain why the zone in which the eight major planets orbit the sun is tilted by about 6 degrees compared to the sun's equator.

"Over long periods of time, Planet Nine will make the entire solar-system plane precess, or wobble, just like a top on a table," Batygin said in the statement.

Finally, the researchers demonstrate how Planet Nine's presence could explain why some Kuiper Belt objects orbit in the opposite direction from everything else in the solar system.

"No other model can explain the weirdness of these high-inclination orbits," Batygin said in the statement. "It turns out that Planet Nine provides a natural avenue for their generation. These things have been twisted out of the solar system plane with help from Planet Nine and then scattered inward by Neptune."

Going forward, the researchers plan to use the Subaru Telescope at Mauna Kea Observatory in Hawaii to find Planet Nine, and then deduce where the mysterious world came from.

The most common type of planets discovered around other stars in our galaxy has been what astronomers call "super Earths" &mdash rocky worlds that are larger than Earth but smaller than Neptune. However, no such planet has yet been discovered in our solar system, meaning that Planet Nine could be our missing "super Earth," the researchers said.

Editor's Note: This article has been updated to clarify that some Kuiper Belt objects unexpectedly orbit in the opposite direction to the rest of the Solar System, not all of them.