NASA’s Hubble Space Telescope has observed a planet outside our solar system that looks as black as fresh asphalt because it eats light rather than reflecting it back into space. This light-eating prowess is due to the planet’s unique capability to trap at least 94 percent of the visible starlight falling into its atmosphere.
The oddball exoplanet, called WASP-12b, is one of a class of so-called “hot Jupiters,” gigantic, gaseous planets that orbit very close to their host star and are heated to extreme temperatures. The planet’s atmosphere is so hot that most molecules are unable to survive on the blistering day side of the planet, where the temperature is 4,600 degrees Fahrenheit. Therefore, clouds probably cannot form to reflect light back into space. Instead, incoming light penetrates deep into the planet’s atmosphere where it is absorbed by hydrogen atoms and converted to heat energy.
“We did not expect to find such a dark exoplanet,” said Taylor Bell of McGill University and the Institute for Research on Exoplanets in Montreal, Quebec, Canada, lead researcher of the Hubble study. “Most hot Jupiters reflect about 40 percent of starlight.”
But the planet’s nighttime side is a different story. WASP-12b has a fixed day side and night side because it orbits so close to the star that it is tidally locked. The nighttime side is more than 2,000 degrees Fahrenheit cooler, which allows water vapor and clouds to form. Previous Hubble observations of the day/night boundary detected evidence of water vapor and possibly clouds and hazes in the atmosphere. WASP-12b is about 2 million miles away from its star and completes an orbit once a day.
“This new Hubble research further demonstrates the vast diversity among the strange population of hot Jupiters,” Bell said. “You can have planets like WASP-12b that are 4,600 degrees Fahrenheit and some that are 2,200 degrees Fahrenheit, and they’re both called hot Jupiters. Past observations of hot Jupiters indicate that the temperature difference between the day and night sides of the planet increases with hotter day sides. This previous research suggests that more heat is being pumped into the day side of the planet, but the processes, such as winds, that carry the heat to the night side of the planet don’t keep up the pace.”
The researchers determined the planet’s light-eating capabilities by using Hubble’s Space Telescope Imaging Spectrograph to search in mostly visible light for a tiny dip in starlight as the planet passed directly behind the star. The amount of dimming tells astronomers how much reflected light is given off by the planet. However, the observations did not detect reflected light, meaning that the daytime side of the planet is absorbing almost all the starlight falling onto it.
First spotted in 2008, WASP-12b circles a Sun-like star residing 1,400 light-years away in the constellation Auriga. Since its discovery, several telescopes have studied the exoplanet, including Hubble, NASA’s Spitzer Space Telescope, and NASA’s Chandra X-ray Observatory. Previous observations by Hubble’s Cosmic Origins Spectrograph (COS) revealed that the planet may be downsizing. COS detected material from the planet’s super-heated atmosphere spilling onto the star.
The results will appear online Sept. 14 in The Astrophysical Journal Letters.
Darubini ya angani ya NASA ya Hubble imegundua sayari moja nje ya mfumo wetu wa jua ambayo inaonekana nyeusi kama lami safi kwa sababu inakula mwanga badala ya kuirudisha kwenye anga. Uwezo huu wa kula mwanga unatokana na uwezo wa kipekee wa sayari hiyo ya kukamata angalau asilimia 94 ya mwanga wa nyota inayoonekana unaoanguka katika anga yake. "WASP-12b ni moja ya ""Jupiters moto"" - sayari kubwa gesi kwamba mzunguko karibu sana na nyota yao mwenyeji na ni joto kwa joto kali." Anga la sayari hiyo ni moto sana hivi kwamba molekuli nyingi haziwezi kuishi katika sehemu ya jua yenye joto kali, ambapo joto ni digrii 4,600 Fahrenheit. Kwa hiyo, yaelekea mawingu hayawezi kuumbwa ili kutafakari nuru kurudi angani. Badala yake, nuru inayokuja huingia ndani ya angahewa la sayari ambapo huchukuliwa na atomu za hidrojeni na kubadilishwa kuwa nishati ya joto. "Hatukutazamia kupata sayari ya nje yenye giza kama hilo", alisema Taylor Bell wa Chuo Kikuu cha McGill na Taasisi ya Utafiti wa Sayari za Nje huko Montreal, Quebec, Canada, mtafiti mkuu wa utafiti wa Hubble. Jupita yenye joto zaidi huonyesha asilimia 40 ya mwanga wa nyota, lakini upande wa usiku wa sayari hiyo ni hadithi tofauti. WASP-12b ina upande wa mchana na upande wa usiku, kwa sababu inazunguka karibu sana na nyota yake. Wakati wa usiku, joto la anga ni la chini ya digrii 2,000 Fahrenheit, na hivyo mvuke wa maji na mawingu hufanyizwa. Uchunguzi wa awali wa Hubble wa mpaka wa mchana na usiku uligundua uthibitisho wa mvuke wa maji na labda mawingu na ukungu katika angahewa. WASP-12b iko umbali wa kilomita milioni mbili kutoka kwa nyota yake na huzunguka dunia mara moja kwa siku. "Utafiti huu mpya wa Hubble unaonyesha zaidi utofauti mkubwa kati ya idadi ya ajabu ya Jupita moto", Bell alisema. "Wasiwasi wa WASP-12b ni kwamba ""Jupiter"" ni ""Jupiter"" ya joto." Uchunguzi wa zamani wa Jupita moto unaonyesha kwamba tofauti ya joto kati ya pande za mchana na usiku za sayari hiyo huongezeka wakati pande za mchana zina joto zaidi. Utafiti huu wa awali unaonyesha kuwa joto zaidi linasukumwa kwenye upande wa mchana wa sayari, lakini michakato kama vile upepo, ambayo hubeba joto kwa upande wa usiku wa sayari haifanyi mwendo huo.Watafiti waliamua uwezo wa kula mwanga wa sayari kwa kutumia Hubble Space Telescope Imaging Spectrograph kutafuta mwanga unaoonekana kwa kupungua kidogo kwa mwanga wa nyota wakati sayari ilipita moja kwa moja nyuma ya nyota. Kiasi cha giza huwaambia wataalamu wa nyota ni nuru ngapi inayorudishwa na sayari hiyo. Hata hivyo, uchunguzi huo haukugundua mwangaza unaorudiwa, ikimaanisha kwamba upande wa mchana wa sayari hiyo unafyonza karibu mwangaza wote wa nyota unaomwangukia. WASP-12b, ambayo iligunduliwa mwaka 2008, inazunguka nyota inayofanana na Jua, iliyo umbali wa miaka 1,400 ya mwanga kutoka kwenye nyota ya Auriga. Tangu kugunduliwa kwake, darubini kadhaa zimechunguza sayari hiyo ya nje, kutia ndani Hubble, Darubini ya Anga ya Spitzer ya NASA, na Chandra X-ray Observatory ya NASA. Uchunguzi wa Hubble Cosmic Origins Spectrograph (COS) ulionyesha kwamba huenda sayari hiyo ilikuwa ikipungua. COS iligundua nyenzo kutoka kwa anga la sayari yenye joto sana ikimwagika kwenye nyota. Matokeo ya utafiti huo yatatolewa katika jarida la The Astrophysical Journal Letters.