H1504+65

{{short description|White dwarf in Ursae Minoris constellation}}

{{notability|astro|date=January 2024}}

{{Starbox begin

| name = H1504+65

}}

{{Starbox observe

| epoch = J2000

| constell = Ursa Minor

| ra = {{RA|15|02|09.6297}}

| dec = {{DEC|+66|12|19.1461}}

| appmag_v = 15.9

}}

{{Starbox character

| class =

| b-v =

| u-b =

| variable =

}}

{{Starbox astrometry

| radial_v =

| prop_mo_ra = {{val|−6.055|0.128}}

| prop_mo_dec = {{val|8.106|0.112}}

| parallax = 2.0573

| p_error = 0.0591

| parallax_footnote =

| absmag_v =

}}

{{Starbox detail

| mass =

| radius =

| luminosity =

| temperature = 200,000

| metal_fe =

| rotational_velocity =

| age_gyr =

}}

{{Starbox catalog

| names = WD 1501+663

}}

{{Starbox reference

| Simbad = RBS+1455

}}

{{Starbox end}}

H1504+65 is an enigmatic peculiar star in the constellation Ursa Minor. With a surface temperature of 200,000 K (360,000°F) and an atmosphere composed of carbon, oxygen and 2% neon, it is the second hottest white dwarf ever discovered, with only RX J0439.8−6809 being hotter. It is thought to be the stellar core of a post-asymptotic giant branch star, though its composition is unexplainable by current models of stellar evolution.{{cite journal|last=Werner|first=K.|author2=Rauch, T.|date=2011|title=UV spectroscopy of the hot bare stellar core H1504+65 with the HST Cosmic Origins Spectrograph|journal=Astrophysics and Space Science|volume=335|issue=1|pages=121–24|doi=10.1007/s10509-011-0617-x|bibcode = 2011Ap&SS.335..121W |s2cid=116910726}}