G 240-72

{{Starbox begin

|name= G 240-72

}}

{{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|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

|ra={{RA|17|48|07.99282}}

|dec={{DEC|+70|52|35.9221}}

|appmag_v=14.15

{{cite journal

| last=Holberg |first=J. B.

| 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}}}}

{{Starbox character

|class=DQP9.0

|appmag_1_passband=B

|appmag_1=14.55

|appmag_2_passband=V

|appmag_2=14.15

|appmag_3_passband=R

|appmag_3=13.5

|appmag_4_passband=I

|appmag_4=13.1

|appmag_5_passband=J

|appmag_5=12.709 ± 0.021

|appmag_6_passband=H

|appmag_6=12.528 ± 0.023

|appmag_7_passband=K

|appmag_7=12.507 ± 0.023}}

{{Starbox astrometry

|prop_mo_ra=-1266.387

|prop_mo_dec=1108.801

|pm_footnote=

|parallax=160.9952

|p_error=0.0119

|parallax_footnote=

| absmag_v=15.23{{r|van Altena1995}}From apparent magnitude and parallax.

}}

{{Starbox detail

| mass=0.81 ± 0.01

| gravity=8.36 ± 0.02

| radius=0.00984From surface gravity and mass.

| temperature=5590 ± 90

| luminosity = 0.000085

|rotation=>100 years

| age_gyr=5.69Cooling age, i. e. age as degenerate star (not counting duration of previous existence as main sequence star and as giant star)}}

{{Starbox catalog

|names={{odlist | 2MASS=J17480817+7052353 | EGGR=372 | G=240-72 | GJ=1221 | LHS=455 | LP=44-113 | NLTT=45565 | WD=1748+708}}

}}

{{Starbox reference

| Simbad=GJ+1221

}}

G 240-72 (or WD 1748+708, or LHS 455, or GJ 1221) is a nearby degenerate star (white dwarf) of spectral class DQP9.0, located 20.3 light-years away in the 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 B). Its trigonometric parallax, as measured by the Gaia space telescope, is {{val|160.9952|0.0119|ul=mas}}, 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 masses and surface gravity 10^8.36 (2.29 · 10⁸) cm·s⁻², or approximately 234 000 of Earth's, corresponding to a radius 6850 km, or 107% of Earth's.

This white dwarf has a relatively low temperature of 5590 K (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 Gyr. 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.[https://iopscience.iop.org/article/10.1088/0004-637X/773/1/47/pdf MEASURING THE ROTATIONAL PERIODS OF ISOLATED MAGNETIC WHITE DWARFS]

References

{{reflist|refs=

{{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}}

{{cite web|url=http://webviz.u-strasbg.fr/viz-bin/VizieR-5?-source=I/238A/picat&GCTP=2835.01|title=GCTP 2835.01|work=The General Catalogue of Trigonometric Stellar Parallaxes |edition=Fourth |author1=Van Altena W. F. |author2=Lee J. T. |author3=Hoffleit E. D. |year=1995}}

{{cite journal

| last=Sion |first=Edward M.

|author2=Holberg |author3=Oswalt |author4=McCook |author5= Wasatonic

| 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

}}

{{citation

| 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

| postscript = .

}}

Notes

External links

[https://web.archive.org/web/20120513202710/http://www.chara.gsu.edu/RECONS/TOP100.posted.htm The 100 Nearest Star Systems (RECONS)]

Category:White dwarfs

Category:Draco (constellation)

1221

J17480817+7052353