{{Short description|Star in the constellation Draco}} {{Sky|17|48|08.17|+|70|52|35.3|20.259}} {{Starbox begin}} {{Starbox image |image={{Location map|100x100|AlternativeMap=Draco_constellation_map.svg |alt=G 240-72 is located in the constellation Draco |caption=Location of G 240-72 in the constellation [[Draco (constellation)|Draco]]|border=infobox|mark=Red_pog.png|width=300 |label=G 240-72 |lat=49.8 |long=36.1 }}|caption= }} {{Starbox observe |epoch=[[J2000]] |equinox=[[J2000]] |constell=[[Draco (constellation)|Draco]] |ra={{RA|17|48|07.99282}}<ref name=GaiaDR3/> |dec={{DEC|+70|52|35.9221}}<ref name=GaiaDR3/> |appmag_v=14.15<ref name="Holberg2008"> {{cite journal | last=Holberg |first=J. B. |author2=Sion |author3=Oswalt |author4=McCook |author5=Foran |author6= Subasavage | date=2008 | journal=[[The Astronomical Journal]] | volume=135 |issue=4 | pages=1225–1238 | bibcode=2008AJ....135.1225H | doi=10.1088/0004-6256/135/4/1225 |title=A New Look at the Local White Dwarf Population |s2cid=122855486 |url=https://commons.erau.edu/publication/886 |url-access=subscription}}</ref> }} {{Starbox character |type=[[white dwarf]]<ref name="Holberg2008"/> |class=DQP9.0<ref name="Holberg2008"/> |appmag_1_passband=B |appmag_1=14.55<ref name="Simbad"/> |appmag_2_passband=V |appmag_2=14.15<ref name="Simbad"/> |appmag_3_passband=R |appmag_3=13.5<ref name="Simbad"/> |appmag_4_passband=I |appmag_4=13.1<ref name="Simbad"/> |appmag_5_passband=J |appmag_5=12.709 ± 0.021<ref name="Simbad"/> |appmag_6_passband=H |appmag_6=12.528 ± 0.023<ref name="Simbad"/> |appmag_7_passband=K |appmag_7=12.507 ± 0.023<ref name="Simbad"/>}} {{Starbox astrometry |prop_mo_ra=−1266.387 |prop_mo_dec=1108.801 |pm_footnote=<ref name=GaiaDR3/> |parallax=160.9952 |p_error=0.0119 |parallax_footnote=<ref name=GaiaDR3/> | absmag_v=15.23<ref name="Holberg2008"/>{{r|van Altena1995}}<ref name="note 1" group="note">From apparent magnitude and parallax.</ref> }} {{Starbox detail | mass=0.81 ± 0.01<ref name="Holberg2008"/> | gravity=8.36 ± 0.02<ref name="Holberg2008"/> | radius=0.00984<ref name="Holberg2008"/><ref name="note 2" group="note">From surface gravity and mass.</ref> | temperature=5590 ± 90<ref name="Holberg2008"/> | luminosity = 0.000085<ref name="ApJS199_2_29"/> |rotation=>100 years<ref name=Brinkworth2013/> | age_gyr=5.69<ref name="note 3" group="note">Cooling age, i. e. age as degenerate star (not counting duration of previous existence as main sequence star and as giant star)</ref><ref name="Sion2009"/>}} {{Starbox catalog |names={{odlist | 2MASS=J17480817+7052353 | EGGR=372 | G=240-72 | GJ=1221 | LHS=455 | LP=44-113 | NLTT=45565 | WD=1748+708}}<ref name="Simbad"/> }} {{Starbox reference | Simbad=GJ+1221 }} {{Starbox end}}
'''G 240-72''' (or '''WD 1748+708''', or '''LHS 455''', or '''GJ 1221''') is a nearby [[white dwarf]] (degenerate star) of spectral class DQP9.0,<ref name="Holberg2008"/> located 20.3 [[light-year]]s away in the constellation [[Draco (constellation)|Draco]].
==Distance== G 240-72 is the seventh closest white dwarf (after [[Sirius B]], [[Procyon B]], [[van Maanen's star]], [[Gliese 440]], [[40 Eridani B]] and [[Stein 2051|Stein 2051 B]]). Its [[parallax|trigonometric parallax]], as measured by the [[Gaia (spacecraft)|Gaia]] space telescope, is {{val|160.9952|0.0119|ul=mas}},<ref name=GaiaDR3/> corresponding to a distance of {{convert|6.2114|pc|ly|lk=on|abbr=off}}.
==Properties== G 240-72 has a mass of 0.81 [[Solar mass]]es<ref name="Holberg2008"/> and [[surface gravity]] 10<sup>8.36</sup> ({{val|2.29|e=8}}) cm·s<sup>−2</sup>,<ref name="Holberg2008"/> or approximately 234 000 of [[Earth's gravity|Earth]]'s, corresponding to a radius 6850 [[kilometer|km]], or 107% of [[Earth's radius|Earth's]].
This white dwarf has a relatively low temperature of 5590 [[Kelvin|K]]<ref name="Holberg2008"/> (slightly cooler than the [[Sun]]), and an old cooling age, i.e. the age as a degenerate star (not counting the duration of its previous existence as a main sequence and giant star) of 5.69 [[Gigayear|Gyr]].<ref name="Sion2009"/> It has a white appearance, due to its similar temperature to the [[Sun]]. It has a pure helium atmosphere and rotates very slowly, with period of possibly over 100 years.<ref name="Brinkworth2013" />
==References== <references> <ref name=GaiaDR3>{{Cite Gaia DR3|1638979384378696704}}</ref>
<ref name="Simbad">{{cite web | url=http://simbad.u-strasbg.fr/simbad/sim-id?Ident=GJ+1221 | title =GJ 1221 – White Dwarf | publisher=[[Centre de Données astronomiques de Strasbourg]] | access-date=2011-10-23}}</ref>
<ref name="van Altena1995">{{cite book |url=http://webviz.u-strasbg.fr/viz-bin/VizieR-5?-source=I/238A/picat&GCTP=2835.01 |title=GCTP 2835.01 |series=The General Catalogue of Trigonometric Stellar Parallaxes |edition=Fourth |last1=Van Altena |first1=W. F. |last2=Lee |first2=J. T. |last3=Hoffleit |first3=E. D. |year=1995 |bibcode=1995gcts.book.....V |archive-date=2022-05-23 |access-date=2015-10-10 |archive-url=https://web.archive.org/web/20220523021021/http://webviz.u-strasbg.fr/viz-bin/VizieR-5?-source=I/238A/picat&GCTP=2835.01 |url-status=dead }}</ref>
<ref name="Sion2009"> {{cite journal | last1=Sion | first1=Edward M. | last2=Holberg | first2=J. B. | last3=Oswalt | first3=Terry D. | last4=McCook | first4=George P. | last5=Wasatonic | first5=Richard | date=2009 | journal=[[The Astronomical Journal]] | volume=138 |issue=6 | pages=1681–1689 | bibcode=2009AJ....138.1681S | doi=10.1088/0004-6256/138/6/1681 |arxiv = 0910.1288 |title=The White Dwarfs within 20 Parsecs of the Sun: Kinematics and Statistics |s2cid=119284418 }}</ref>
<ref name="ApJS199_2_29">{{cite journal | last1 = Giammichele | first1 = N. | last2 = Bergeron | first2 = P. | last3 = Dufour | first3 = P. | title = Know Your Neighborhood: A Detailed Model Atmosphere Analysis of Nearby White Dwarfs | journal = The Astrophysical Journal Supplement | volume = 199 | issue = 2 | page = 29 | date = April 2012 | arxiv = 1202.5581 | doi = 10.1088/0067-0049/199/2/29 | bibcode = 2012ApJS..199...29G | s2cid = 118304737 }}</ref>
<ref name="Brinkworth2013">{{Cite journal |last1 = Brinkworth |first1=Carolyn S. |last2 = Burleigh |first2=Matthew R. |last3 = Lawrie |first3=Katherine |last4 = Marsh |first4=Thomas R. |last5 = Knigge |first5=Christian |date = August 2013 |title = Measuring the Rotational Periods of Isolated Magnetic White Dwarfs |journal = [[The Astrophysical Journal]] |volume = 773 |issue = 1 |pages = 47 |doi = 10.1088/0004-637X/773/1/47 |bibcode = 2013ApJ...773...47B |issn = 0004-637X }}</ref> </references>
==Notes== <references group="note"/>
==External links== *[https://web.archive.org/web/20120513202710/http://www.chara.gsu.edu/RECONS/TOP100.posted.htm The 100 Nearest Star Systems (RECONS)]
{{Stars of Draco}}
[[Category:White dwarfs]] [[Category:Draco (constellation)]] [[Category:Gliese and GJ objects|1221]]