View source for Astronomy:GD 61

{{Short description|Star in the constellation Perseus}}
{{Starbox begin
| name=GD 61
}}
{{starbox observe
| epoch=J2000
|constell=[[Astronomy:Perseus (constellation)|Perseus]]
| ra={{RA|04|38|39.39}}<ref name=SIMBAD/>
| dec={{DEC|+41|09|32.5}}<ref name=SIMBAD/>
| appmag_v=14.8<ref name="xu">{{cite journal|last=S. Xu (许偲艺) and M. Jura|title=Spitzer Observations of White Dwarfs: The Missing Planetary Debris around DZ Stars|date=2012|journal=The Astrophysical Journal|volume=745|issue=1|pages=88–102|bibcode=2012ApJ...745...88X|doi=10.1088/0004-637X/745/1/88|arxiv = 1109.4207 |s2cid=118755550}}</ref>
}}
{{starbox character
| type=DBAZ3<ref name=SIMBAD>{{cite simbad |title = GD 61 |access-date = 20 October 2013}}</ref>
}}
{{Starbox detail
| source=<ref name="farihi" />
| mass=70%
| temperature=17,280
| age_myr=600
}}
{{Starbox catalog
| names = 2MASS J04383938+4109325, EGGR 315, WD 0435+41, Lan 542   
}}
{{ Starbox reference
| Simbad = GD+61
}}
{{starbox end}}

'''GD 61''' is a [[Astronomy:White dwarf|white dwarf]] with a protoplanetary system located 150 light-years from Earth in the constellation [[Astronomy:Perseus (constellation)|Perseus]].<ref>{{cite web|url=https://www.sciencenews.org/article/water-seen-rubble-around-star|title=Water seen in rubble around star
|date=13 October 2013|access-date=14 October 2013|author=Rosen, Meghan|work=ScienceNews}}</ref> It is thought to have been a main-sequence star of spectral type A0V with around three times the mass of the Sun that has aged and passed through a [[Astronomy:Red giant|red-giant]] phase, leaving a dense, hot remnant that has around 70% of the Sun's mass and a surface temperature of 17,280 K. It is thought to be around 600 million years old, including both its life as a main-sequence star and as a white dwarf.<ref name="farihi">{{cite journal|author1=Farihi, J. |author2=Brinkworth, C. S. |author3=Gänsicke, B. T. |author4=Marsh, T. R. |author5=Girven, J. |author6=Hoard, D. W. |author7=Klein, B. |author8=Koester, D. |title=Possible Signs of Water and Differentiation in a Rocky Exoplanetary Body|journal=The Astrophysical Journal Letters|year=2011 |volume=728|issue=1|pages= L8–L13|bibcode=2011ApJ...728L...8F|doi=10.1088/2041-8205/728/1/L8|arxiv = 1101.0158 |s2cid=46224877 }}</ref> It has an apparent magnitude of 14.8.<ref name="xu"/> GD 61 was first noted as a potential degenerate star in 1965, in a survey of white-dwarf suspects by astronomers from the [[Astronomy:Lowell Observatory|Lowell Observatory]] in Arizona.<ref>{{cite journal|author1=Giclas, Henry L. |author2=Burnham, Robert |author3=Thomas, Norman Gene |date=1965|title=A list of white dwarf suspects I : special objects of small proper motion from the Lowell survey|journal=Bulletin / Lowell Observatory|volume=6|issue=6|pages=155–64|bibcode=1965LowOB...6..155G}}</ref>

In 2013, a circumstellar disk that resulted from the destruction of a water-rich asteroid was detected in close orbit around GD 61, which makes this the first detection of solid or liquid water on an extrasolar body. This asteroid would originally have been 26% water by mass, close to the water content of [[Astronomy:Ceres (dwarf planet)|Ceres]].<ref name=circumstellar>[https://arxiv.org/abs/1310.3269 Evidence for water in the rocky debris of a disrupted extrasolar minor planet]</ref> This evidence suggests that a planet, with a rocky surface similar to Earth's, may have existed in the past, with the asteroid thus being an artifact from this period, now possibly part of a debris field from the hypothetical planet's breakup. Such a planet would have had both a rocky surface and water, two key ingredients for life.<ref name=watery>{{cite web|url=http://phys.org/news/2013-10-watery-asteroid-dying-star-habitable.html |title=Watery asteroid discovered in dying star points to habitable exoplanets |publisher=Phys.org |date=10 October 2013 |access-date=12 October 2013}}</ref><ref>{{cite web|last=Mack |first=Eric |url=http://news.cnet.com/8301-17938_105-57607077-1/newly-spotted-wet-asteroids-point-to-far-flung-earth-like-planets/ |title=Newly spotted wet asteroids point to far-flung Earth-like planets &#124; Crave - CNET |publisher=News.cnet.com |date=17 October 2011 |access-date=12 October 2013}}</ref> The researchers used the [[Astronomy:Cosmic Origins Spectrograph|Cosmic Origins Spectrograph]] on the Hubble Space Telescope to determine the elemental composition. The elements magnesium, silicon, iron, and oxygen were detected, all components of rocky planets, although the levels of oxygen were much higher than what could be accounted for. The lack of associated carbon left only one candidate for the oxygen excess—water.<ref name=watery/><!-- cites previous two sentences -->

==See also==
*[[Astronomy:Extraterrestrial liquid water|Extraterrestrial liquid water]]
*[[Astronomy:24 Themis|24 Themis]], the first Solar System asteroid detected having liquid water

==References==
{{reflist}}

{{Stars of Perseus}}

[[Category:White dwarfs]]
[[Category:Astrobiology]]
[[Category:Perseus (constellation)]]

{{Sourceattribution|GD 61}}