How to Measure a Planet's Mass
Ukuqonda ubukhulu beplanethi kubalulekile ezicini eziningi zesayensi yamaplanethi kanye ne-astrophysics. Ngokulinganisa ubukhulu okunembile, ososayensi bangaphetha ukwakheka kweplanethi, ubuningi bayo, umphumela wamandla adonsela phansi, ngisho nomlando wokudalwa kwayo. Ngenkathi ubukhulu bendawo buyenza ibe nzima izilinganiso eziqondile, izindlela ezihlakaniphile ezingaqondile ziye zathuthukiswa emashumini eminyaka edlule. Lesi sihloko sizohlola amasu ahlukahlukene asetshenziswa ukukala ubunzima beplanethi, okuhlanganisa ukusebenzisana kwamandla adonsela phansi, amandla okujikeleza, kanye nezindlela ze-astrometric.
Gravitational Influence
Esinye sezimiso eziyisisekelo ezisetshenziswa ukukala isisindo seplanethi umthetho kaNewton wamandla adonsela phansi. Ngokwalo mthetho, amandla adonsela phansi phakathi kwezinto ezimbili alingana ngqo nomkhiqizo wobuningi bazo futhi alingana ngokuphambene nesikwele sebanga eliphakathi kwazo. Uma sisetshenziswa ezinhlelweni zamaplanethi, lesi simiso sivumela ososayensi ukuthi banqume ubukhulu beplanethi ngokutadisha imiphumela yamandla adonsela phansi enayo ezintweni eziseduze.
Gravitational Effects on Satellites
Ukuba khona kwamasathelayithi emvelo noma okwenziwa azungeza iplanethi kunikeza indlela elula yokulinganisa isisindo seplanethi. Ngokubuka umjikelezo wesathelayithi, ososayensi bangathola ulwazi olubalulekile mayelana nomthelela wamandla adonsela phansi womzimba oyinhloko.
Isikhathi sokuzungeza umhlaba (T) kanye ne-semi-major axis (a) yokujikeleza kwesathelayithi emhlabeni wonke kuhlobene nomthetho wesithathu kaKepler:
[ T^2 = \frac{4 \pi^2}{G(M+m)} a^3 ]
lapho u-(T) eyinkathi, (a) iyi-semi-major axis yomjikelezo, (G) iyi-gravitational constant, (M) iyisisindo seplanethi, kanye no-(m) iyisisindo sesathelayithi (esivame ukuba sincane uma siqhathaniswa no-(M)).
Ukubhala kabusha i-equation ye-(M):
[ M \approx \frac{4 \pi^2 a^3}{GT^2} ]
Ngokulinganisa ngokunembile isikhathi sokuzungeza kwesathelayithi kanye ne-axis eyinhloko, ososayensi bangakwazi ukubala isisindo seplanethi.
Gravitational Effects on Nearby Planets
Amaplanethi angaphakathi kwesimiso sezinkanyezi esifanayo asebenzisa amandla adonsela phansi komunye nomunye. Izinguquko ezicashile emizuliswaneni yawo ngenxa yalokhu kusebenzisana zingasetshenziswa ukulinganisa ubukhulu bawo. Ngokomlando, le ndlela ivumele izazi zezinkanyezi ukuthi zithole ubukhulu bamaplanethi afana neJupiter ngokubheka imiphumela yayo emizuliswaneni yamaplanethi nezinyanga eziseduze nayo.
Orbital Dynamics of Multiple Bodies
Ezinhlelweni ezinemizimba eminingi yamaplanethi, izifundo ezinemininingwane yokunyakaza kwazo zingaveza ubuningi. Ukusebenzisana okuyinkimbinkimbi kwamandla adonsela phansi ngaphakathi kwezinhlelo ezinjalo kuvame ukuhlaziywa kusetshenziswa amasu avela kuma-mechanics asezulwini.
Radial Velocity Method
Indlela yejubane le-radial ivame ukusetshenziswa ezifundweni ze-exoplanet kodwa ingasetshenziswa nasesimisweni sethu selanga. Le ndlela ilinganisa ukushintsha kwe-Doppler yenkanyezi noma yeplanethi—izinguquko ku-spectrum yenkanyezi ezibangelwa ukunyakaza kwayo kuye noma kude nathi. Lokhu kushintsha kubonisa ukudonsa okudonsela phansi iplanethi ekwenzayo enkanyezini yayo engumzali.
Uma bebona ukunyakaza okuvamile endaweni yenkanyezi, izazi zezinkanyezi zingalinganisa isisindo seplanethi engabonakali. Ubukhulu bokunyakaza kwenkanyezi buhlinzeka ngedatha ngesilinganiso sobuningi phakathi kwenkanyezi neplanethi ezungezayo.
Transit Timing Variations (TTV)
Uma iplanethi idlula inkanyezi yayo, kuba nokwehla okuncane ekukhanyeni kwenkanyezi. Uma amaplanethi amaningi ejikeleza inkanyezi efanayo, ukusebenzisana kwawo kwamandla adonsela phansi kungabangela ukushintshashintsha kwesikhathi esiqondile salezi zindlela zokuhamba. Ngokulinganisa ukushintshashintsha, okwaziwa ngokuthi yi-Transit Timing Variations (TTV), ososayensi bangaphetha ngobuningi bamaplanethi asebenzisanayo. Le ndlela ibe usizo kakhulu ekufundeni izinhlelo zangaphandle zamaplanethi ezinamaplanethi amaningi.
Astrometric Methods
I-Astrometry ihilela ukulinganisa ngokunembile izikhundla kanye nokunyakaza kwezinkanyezi ngokuhamba kwesikhathi. Ukwehluka kwalokhu kunyakaza kungabonisa ukuthi kukhona amaplanethi. Lapho inkanyezi ihamba kancane ngenxa yokudonswa kwamandla adonsela phansi kweplanethi ezungezayo, indawo yayo iyashintsha njalo. Ngokulandelela lokhu kushintsha, ososayensi bangabona izici zokujikeleza kweplanethi, okuhlanganisa nobukhulu bayo.
Astrometric Measurements of Stars
Kwababona izinkanyezi, izazi zezinkanyezi zibona 'ukuzamazama' kwenkanyezi okubangelwa ukudonswa kwamandla adonsela phansi kweplanethi ezungezayo. Lokhu kuzamazama kuphumela ekushintsheni okuncane endaweni yenkanyezi. Ngokuhlaziya lokhu kushintsha kwesimo, ubunzima beplanethi ezungezayo bungalinganiswa. I-Astrometry idinga ukunemba okukhulu, okuvame ukufezwa ngezindawo zokuhlola ezisemkhathini njenge-Gaia mission, edweba izikhundla zezinkanyezi ngokunemba okungakaze kubonwe.
Gravitational Lensing
Ukubona i-gravitational lens, okuwumphumela we-Einstein's General Relativity, kunikeza enye indlela engaqondile yokulinganisa isisindo seplanethi. Lapho ukukhanya okuvela enkanyezini ekude kudlula eduze kwento enkulu njengeplanethi, insimu yamandla adonsela phansi yeplanethi ingagoba ukukhanya, ikhulise futhi iguqule isithombe senkanyezi.
Microlensing Events
Ekulenseni okudonsela phansi, iplanethi edlula phakathi kwethu nenkanyezi ekude isebenza njengelensi, ikhanyisa futhi iphambukise ukukhanya kwenkanyezi okwesikhashana. Izici zalesi senzakalo sokukhanya zincike ebunzini beplanethi elensi kanye nebanga layo kokubili enkanyezini nakumbukeli.
Ngokutadisha izehlakalo ezinjalo ze-microlensing, ososayensi bangalinganisa ubukhulu beplanethi ye-lensing. Le ndlela iwusizo kakhulu ekutholeni nasekulinganiseni amaplanethi okungaba nzima ukuwabona ngezindlela zejubane eliqondile noma eliqondile.
Combining Methods for Greater Precision
Ngokuvamile, inhlanganisela yalezi zindlela ezingenhla isetshenziswa ukukala isisindo seplanethi ngokunemba okuphezulu. Isibonelo, idatha yejubane le-radial ehlanganiswe nokubonwa kokuhamba inganikeza kokubili isisindo kanye ne-radius yeplanethi, okuholela ekulinganisweni kobuningi bayo, futhi ngenxa yalokho, ukwakheka kwayo okungenzeka.
Esimisweni sethu selanga, ubuningi bamaplanethi bunqunywe ngokunemba okuphezulu kusetshenziswa amasu amaningi. Isibonelo, ubuningi beJupiter neSaturn buyaziwa amakhulu eminyaka ngemiphumela yabo yamandla adonsela phansi enyangeni nasemaplanethini aseduze. Imisebenzi yanamuhla efana neJuno (ezungeza iJupiter) neCassini (eyayizungeza iSaturn) ilungise lezi zilinganiso.
Kumaplanethi angaphandle, inhlanganisela yejubane eliqondile kanye nezindlela zokuhamba kube yiyona ethela kakhulu, eveza ubuningi obunembile kumakhulu amaplanethi.
Conclusion
Ukulinganisa isisindo seplanethi kuhilela ukuqonda nokusebenzisa izimiso eziyisisekelo zamandla adonsela phansi kanye nokuguquguquka kwe-orbital. Kusukela ekuhlaziyeni imijikelezo yezinyanga kuya ekubukeni ukuntengantenga kwezinkanyezi, ukushintshashintsha kwesikhathi sokuthutha, kanye nemicimbi yokulinganisa amandla adonsela phansi, ososayensi bathuthukise izindlela eziningi zokulinganisa amaplanethi ngaphakathi nangaphandle kwesimiso sethu selanga. Indlela ngayinye inikeza ukuqonda okuhlukile futhi, uma isetshenziswa ndawonye, inikeza isithombe esiphelele sesisindo seplanethi. Njengoba ubuchwepheshe bokubuka buqhubeka nokuthuthuka, ikhono lethu lokukala isisindo seplanethi lizoba nembile kakhulu, livule ukuqonda okujulile kwezwe elihlukahlukene eligcwele indawo yonke yethu.
