WR 124 is a
Wolf–Rayet star in the
constellation of
Sagitta surrounded by a ring
nebula of expelled material known as
M1-67.[9] It is one of the fastest runaway
stars in the
Milky Way with a radial velocity around 200
km/s. It was discovered by
Paul W. Merrill in 1938, identified as a high-velocity Wolf–Rayet star.[10] It is listed in the
General Catalogue of Variable Stars as QR Sagittae with a range of 0.08 magnitudes.[5] NASA's James Webb Space Telescope has captured detailed infrared images of WR 124,[11] revealing significant dust production and offering new insights[12] into the life cycles of massive stars and their contributions to the cosmic dust budget.
Distance
A 2010 study of WR 124 directly measured the expansion rate of the M1-67
nebula expelled from the star using
Hubble Space Telescope camera images taken 11 years apart, and compared that to the expansion velocity measured by the
Doppler shift of the nebular emission lines.[8] This yielded a distance of 3.35
kpc, which is less than previous studies, and the resulting
luminosity of 150,000 times the
Sun (L☉) is much lower than previously calculated. The luminosity is also lower than predicted by models for a star of this spectral class. Previous studies had found distances of 5 kpc[9] to 8.4 kpc,[3] with corresponding luminosities of 338,000–1,000,000 L☉, as expected for a typical WN8h which is a very young star just moving away from the
main sequence. The distance to WR 124 calculated from the
parallax published in
Gaia Data Release 2 is 6,203+1,621 −1,123pc.[13]Gaia Early Data Release 3 gives a similar parallax, which would suggest a distance 6,400+500 −500pc.[1]
Physical characteristics
With an assumed visual
absolute magnitude of −7.22 and 3.1 magnitudes of
extinction, WR 124 would be 8.5 kpc away. The temperature of around 40,000 K means that most of its energy is emitted at
ultraviolet wavelengths, the
bolometric luminosity is 1,000,000
L☉ and the radius is 26
R☉. The mass is calculated from evolutionary models to be 33
M☉.[3]
WR 124 is measured to still be about 15% hydrogen with most of the remaining mass being helium. A young highly massive and luminous WN8h star would still be burning hydrogen in its core, but a less luminous and older star would be burning helium in its core.[15] The result of modelling the star purely from its observed characteristics is a luminosity of 1,000,000 L☉ and a mass of 33 M☉, corresponding to a relatively young hydrogen-burning star at around 8 kpc.[3] In either case, it has only a few hundred thousand years before it explodes as a type Ib or Ic
supernova.
The mass loss rate is 10−5M☉–10−4M☉ per year, depending on the distance and properties determined for the star.[9]
Nebula
WR 124 is surrounded by an intensely hot nebula formed from the star's extreme stellar wind.[9] The nebula M1-67 is expanding at a rate of over 150,000 km/h (93,000 mph) and is nearly 6
light-years across, leading to the dynamical age of 20,000 years. M1-67 has little internal structure, though large clumps of material have been detected, some of which have 30 times the mass of
Earth and stretch out up to 150 billion km (93 billion mi). If placed in the
Solar System, one of these clumps would span the distance from the Sun to
Saturn.
^
abcCutri, Roc M.; Skrutskie, Michael F.; Van Dyk, Schuyler D.; Beichman, Charles A.; Carpenter, John M.; Chester, Thomas; Cambresy, Laurent; Evans, Tracey E.; Fowler, John W.; Gizis, John E.; Howard, Elizabeth V.; Huchra, John P.; Jarrett, Thomas H.; Kopan, Eugene L.; Kirkpatrick, J. Davy; Light, Robert M.; Marsh, Kenneth A.; McCallon, Howard L.; Schneider, Stephen E.; Stiening, Rae; Sykes, Matthew J.; Weinberg, Martin D.; Wheaton, William A.; Wheelock, Sherry L.; Zacarias, N. (2003).
"VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)". CDS/ADC Collection of Electronic Catalogues. 2246: II/246.
Bibcode:
2003yCat.2246....0C.
^
abKukarkin, B. V.; Kholopov, P. N.; Pskovsky, Y. P.; Efremov, Y. N.; Kukarkina, N. P.; Kurochkin, N. E.; Medvedeva, G. I. (1971). "The third edition containing information on 20437 variable stars discovered and designated till 1968". General Catalogue of Variable Stars: 0.
Bibcode:
1971GCVS3.C......0K.
^Kharchenko, N. V.; Scholz, R.-D.; Piskunov, A. E.; Röser, S.; Schilbach, E. (2007). "Astrophysical supplements to the ASCC-2.5: Ia. Radial velocities of ˜55000 stars and mean radial velocities of 516 Galactic open clusters and associations". Astronomische Nachrichten. 328 (9): 889.
arXiv:0705.0878.
Bibcode:
2007AN....328..889K.
doi:
10.1002/asna.200710776.
S2CID119323941.
^
abcdeSota, A.; Maíz Apellániz, J.; Morrell, N. I.; Barbá, R. H.; Walborn, N. R.; Gamen, R. C.; Arias, J. I.; Alfaro, E. J.; Oskinova, L. M. (2019). "The Galactic WN stars revisited. Impact of Gaia distances on fundamental stellar parameters". Astronomy & Astrophysics. A57: 625.
arXiv:1904.04687.
Bibcode:
2019A&A...625A..57H.
doi:
10.1051/0004-6361/201834850.
S2CID104292503.
^
abcdCrowther, Paul A.; Pasquali, A.; De Marco, Orsola; Schmutz, W.; Hillier, D. J.; De Koter, A. (1999). "Wolf–Rayet nebulae as tracers of stellar ionizing fluxes. I. M1-67". Astronomy and Astrophysics. 350: 1007.
arXiv:astro-ph/9908200.
Bibcode:
1999A&A...350.1007C.