HD 85512 b: Difference between revisions
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{{Infobox planet |
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| name = HD 85512 b |
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| caption = Artist’s impression of the rocky [[super-Earth]] HD 85512 b |
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<!-- DISCOVERY --> |
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| discoverer = Pepe ''et al.'' |
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| discovery_site = [[La Silla Observatory]] |
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| discovered = August 17, 2011 |
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| discovery_method = [[Radial velocity method|Radial velocity]] ([[High Accuracy Radial Velocity Planet Searcher|HARPS]]) |
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<!-- DESIGNATIONS --> |
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<!-- ORBITAL --> |
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| apsis = astron |
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| semimajor = (0.26 ± 0.005)<ref name=arxiv/> [[astronomical unit|AU]] |
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| eccentricity = (0.11 ± 0.1)<ref name=arxiv/> |
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| period = 54.43 (± 0.13)<ref name=arxiv/> [[day|d]] |
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| avg_speed = 94.913 ± 0.038 |
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| star = [[HD 85512]] |
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<!-- PHYS CHARS --> |
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| mean_radius = ≥1.3(?) {{Earth radius|link=y}} |
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| mass = 3.6 ± 0.5 {{Earth mass|link=y}} |
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| surface_grav = ~1.4 |
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| single_temperature = {{convert|298|K|C F}}<ref name=centauri/> |
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<!-- ATMOSPHERE --> |
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<!-- NOTES --> |
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'''HD 85512 b''' is an [[exoplanet]] orbiting [[HD 85512]], a [[K-type main-sequence star]] approximately 36 [[light-year]]s from Earth in the [[constellation]] of [[Vela (constellation)|Vela]].<ref name=arxiv1>{{cite journal|title=The HARPS search for Earth-like planets in the habitable zone: I – Very low-mass planets around HD20794, HD85512 and HD192310|first=F|last=Pepe|display-authors=etal|date=2011|arxiv=1108.3447|bibcode=2011A&A...534A..58P|doi=10.1051/0004-6361/201117055|volume=534|journal=Astronomy & Astrophysics|pages=A58}}</ref><ref name=arxiv>{{cite journal|title=A Habitable Planet around HD 85512?|first=L|last=Kaltenegger|first2=S|last2=Udry|first3=F|last3=Pepe|date=2011|arxiv=1108.3561|bibcode=2011arXiv1108.3561K}}</ref> |
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Due to its mass of at least 3.6 times the mass of Earth, HD 85512 b is classified as a [[Terrestrial planet|rocky Earth-size exoplanet]] (<5M⊕) and is one of the smallest exoplanets discovered to be just outside the inner edge of the [[habitable zone]].<ref name=arxiv/> HD 85512 b, along with [[Gliese 581 d]], was once considered to be one of the [[List of potential habitable exoplanets|best candidates for habitability]] in 2011.<ref name=maxisciences/> |
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==Physical characteristics== |
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===Mass, radius and temperature=== |
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The planet has a ''minimum'' Earth mass of 3.6 ± 0.5, ''minimum'' [[surface gravity]] of about 1.4 g and assuming an atmosphere like Earth's despite its far greater mass, an estimated temperature of 298 K (24.85 °C or 76.73 °F) at the top of its atmosphere. The estimated temperature is noted to be similar to temperatures in [[Southern France]],<ref name=centauri/><ref>{{cite news|title=Italian helps find planet that could sustain life|url=http://lagazzettadelmezzogiorno.it/notizia.php?IDNotizia=452563&IDCategoria=2694|newspaper=[[La Gazzetta del Mezzogiorno]]|date=September 2, 2011|accessdate=September 7, 2011}}{{dead link|date=October 2017 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> but various atmospheric conditions prevalent in the planet have to be analyzed to estimate the temperature of the surface.<ref name=centauri/> An estimated radius of 1.3 {{Earth radius}} is possible based on its mass. |
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===Host star=== |
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The planet orbits a ([[Stellar classification#Class K|K-type]]) [[star]] named [[HD 85512]]. The star has a mass of 0.69 {{Solar mass}} and a radius of around 0.53 {{Solar radius}}. It has a surface temperature of 4715 [[Kelvin|K]] and is 5.61 billion years old. In comparison, the Sun is about 4.6 billion years old<ref>{{cite web |url=http://www.universetoday.com/18237/how-old-is-the-sun/ |title=How Old is the Sun? |author=Fraser Cain |date=16 September 2008 |work= |publisher=[[Universe Today]] |accessdate=19 February 2011}}</ref> and has a surface temperature of 5778 K.<ref>{{cite web |url=http://www.universetoday.com/18092/temperature-of-the-sun/ |title=Temperature of the Sun |author=Fraser Cain |date=September 15, 2008 |work= |publisher=Universe Today |accessdate=19 February 2011}}</ref> |
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The star's [[apparent magnitude]], or how bright it appears from Earth's perspective, is 7.43 Therefore, HD 85512 is too dim to be seen with the naked eye, but can be viewed using good binoculars. |
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===Orbit=== |
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The planet orbits the parent star with about 11% of the Sun's luminosity at a distance of about 0.26 [[Astronomical unit|AU]],<ref name=maxisciences/> with an orbital period of about 54 days,<ref name=maxisciences/> and possibly tidally locked. |
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==Habitability and climate== |
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[[File:HD85512bWithHZ.svg|225px|thumb|left|Plot of the orbit of HD 85512 b compared to the star's habitable zone.]] |
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Models generated by ''Pepe et al (2011)'' suggest that for the temperature to be below 270 K (-3.15 °C), for a circular orbit, the planetary [[albedo]] should be 0.48 ± 0.05 and for an eccentricity of 0.11, the planetary albedo should be 0.52.<ref name=arxiv/> If the planet has 50% cloud cover, water may exist in liquid form on the planet<ref name=technologie.gazeta/> provided its atmosphere is similar to our own, thus increasing the planet's habitability potential.<ref name=kauno.diena/><ref name=sciam>{{cite web| url=http://www.scientificamerican.com/podcast/episode.cfm?id=exoplanet-looks-potentially-lively-11-08-22| title=Exoplanet Looks Potentially Lively| publisher=scientificamerican.com| accessdate=2011-08-25}}</ref><ref name=spaceref>{{cite web| url=http://www.spaceref.com/news/viewsr.html?pid=38197| title=Is There A Habitable Planet Circling HD 85512?| publisher=spaceref.com| accessdate=2011-08-31}}</ref> Also, if the albedo of the planet is increased due to cloud cover, water could be present in its liquid form on the planet, which would mean that the planet is on the edge of the habitability zone.<ref name=arxiv/><ref name=spaceref/> |
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However, PHL's new definition of the circumstellar habitable zone classifies this planet in the "too hot" zone, and it considers the planet "not habitable".<ref>http://phl.upr.edu/press-releases/anewhabitablezone</ref> |
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The planet would likely be inhospitable because of a [[runaway greenhouse effect]] on its surface. Any oceans on its surface would have boiled away due to the high stellar flux, and as this occurred, the temperature would have risen to around {{convert|322|K|C F}}. The [[water vapor]] would have accumulated in the atmosphere to the point where the surface temperature would rise to around {{convert|500|K|C F}} as the planet would have been overwhelmed by water vapor—a powerful greenhouse gas.<ref>http://csep10.phys.utk.edu/astr161/lect/venus/greenhouse.html</ref> Little amounts of [[carbon dioxide]] would have been present, as HD 85512 b was probably an [[ocean planet]] (with little to no landmasses) very shortly after its star was formed into the [[main sequence]], before the stellar flux increased to its estimated present state. The surface pressure would have also increased to about 100 times Earth's surface pressure (100 [[kilopascal]]s, 100 [[Atmosphere (unit)|atm]]) because of the amount of water vapor in the atmosphere. Thus, HD 85512 b is likely a [[desert planet]] rather than an ocean planet because of the increased stellar flux |
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==Discovery== |
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HD 85512 b was discovered by scientists at [[University of Geneva]], Switzerland,<ref name=maxisciences>{{cite web|url=http://www.maxisciences.com/plan%E8te-habitable/des-chercheurs-decouvrent-une-planete-potentiellement-habitable_art16635.html|title=Researchers find potentially habitable planet|publisher=maxisciences.com|language=French|accessdate=2011-08-31}}</ref><ref name=kauno.diena>{{cite web|url=http://kauno.diena.lt/naujienos/mokslas-ir-it/rasta-planeta-kurioje-galetu-egzistuoti-gyvybe-373401|title=Found a planet where life could exist|publisher=maxisciences.com|language=Lithuanian|accessdate=2011-08-31}}</ref> led by Swiss astronomer [[Stéphane Udry]]<ref name=technologie.gazeta>{{cite web|url=http://technologie.gazeta.pl/internet/1,114257,10139412,Super_Ziemia_krazaca_w_ekosferze_.html|title=Super Earth circulating in ekosferze?|publisher=technologie.gazeta.pl|language=Polish|accessdate=2011-08-31}}</ref> of the Guaranteed Time Observations (GTO) program of High Accuracy Radial velocity Planet Searcher ([[High Accuracy Radial Velocity Planet Searcher|HARPS]]), a high-precision [[Echelle grating|echelle]] [[spectrograph]] installed on [[European Southern Observatory|ESO]]'s 3.6 m telescope at [[La Silla Observatory]] in Chile.<ref name=centauri>{{cite web|url=http://www.centauri-dreams.org/?p=19560|title=HARPS: Hunting for Nearby Earth-like Planets|publisher=centauri-dreams.org|accessdate=2011-08-25}}</ref> The team used the [[Doppler spectroscopy]] technique which determines the [[minimum mass]] of the planet through slight changes in motion of the parent star. It was discovered on August 17, 2011. |
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On August 17, 2011, researchers released a study of the planet. The study makes assumptions about the planet actually having the minimum mass allowed by existing observations, not being tidally locked, and having one specific composition out of the wide parameter set available to conclude that HD 85512 b is the most habitable exoplanet discovered up to that point<ref name=arxiv/> and one of the most stable exoplanets discovered by the High Accuracy Radial Velocity Planet Searcher.<ref name=centauri/>arth2 |
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==Possibility as target for interstellar probe== |
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Reaching HD 85512 b at the current record spacecraft speed, the [[Helios (spacecraft)|Helios Probes]] (247,517 km/hour | 153,800 mi/hour), it would take approximately 156,971 years.<ref name="worldsfastest group">{{cite web| title=The World's Top 12 Fastest Vehicles| url=http://www.popularmechanics.com/technology/engineering/extreme-machines/worlds-top-12-fastest-vehicles#slide-1| work=Popular Mechanics}}</ref> |
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==See also== |
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{{Portal|Astronomy|Space}} |
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*[[Carbon planet]] |
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*[[Circumstellar habitable zone]] |
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*[[Earth analog]] |
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*[[Gliese 581 d]] |
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*[[Gliese 581 g]] |
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*[[Gliese 667 Cc]] |
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*[[Habitable zone]] |
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*[[Kepler 22 b]] |
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*[[Planetary habitability]] |
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*[[Super-Earth]] |
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{{commons category|HD 85512 b}} |
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==References== |
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{{Reflist}} |
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==Notes== |
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{{reflist|group=note}} |
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==External links== |
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* [https://www.cfa.harvard.edu/~lkaltenegger/Home_files/KalteneggerHD85512.pdf A Habitable Planet around HD 85512] |
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{{Gliese 370}} |
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{{Extraterrestrial life}} |
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{{Sky|09|51|07.1|-|43|30|10|36.3}} |
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[[Category:HD 85512]] |
[[Category:HD 85512]] |
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Latest revision as of 18:48, 20 October 2024
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