WR 124 is a

Wolf–Rayet star Wolf–Rayet stars, often abbreviated as WR stars, are a rare heterogeneous set of stars with unusual spectroscopy, spectra showing prominent broad emission lines of ionised helium and highly ionised nitrogen or carbon. The spectra indicate very ...

in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The first constellati ...

of Sagitta surrounded by a ring nebula of expelled material known as M1-67. It is one of the fastest runaway

star A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ...

s in the

Milky Way The Milky Way or Milky Way Galaxy is the galaxy that includes the Solar System, with the name describing the #Appearance, galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars in other arms of the galax ...

with a radial velocity around . It was discovered by Paul W. Merrill in 1938, identified as a high-velocity Wolf–Rayet star. It is listed in the General Catalogue of Variable Stars as QR Sagittae with a range of 0.08 magnitudes.

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 The Hubble Space Telescope (HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the Orbiting Solar Observatory, first space telescope, but it is one of the largest and most ...

camera images taken 11 years apart, and compared that to the expansion velocity measured by the Doppler shift of the nebular emission lines. This yielded a distance of , which is less than previous studies, and the resulting

luminosity Luminosity is an absolute measure of radiated electromagnetic radiation, electromagnetic energy per unit time, and is synonymous with the radiant power emitted by a light-emitting object. In astronomy, luminosity is the total amount of electroma ...

of 150,000 times the Sun () 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 to , with corresponding luminosities of , as expected for a typical WN8h which is a very young star just moving away from the

main sequence In astronomy, the main sequence is a classification of stars which appear on plots of stellar color index, color versus absolute magnitude, brightness as a continuous and distinctive band. Stars on this band are known as main-sequence stars or d ...

. The distance to WR 124 calculated from the parallax published in Gaia Data Release 2 is . Gaia Early Data Release 3 gives a similar parallax, which would suggest a distance .

Physical characteristics

With an assumed visual absolute magnitude of −7.22 and 3.1 magnitudes of

extinction Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

, WR 124 would be away. The temperature of around means that most of its energy is emitted at

ultraviolet Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of ...

wavelengths, the bolometric luminosity is and the radius is . The mass is calculated from evolutionary models to be . 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. The result of modelling the star purely from its observed characteristics is a luminosity of and a mass of , corresponding to a relatively young hydrogen-burning star at around . In either case, it has only a few hundred thousand years before it explodes as a type Ib or Ic

supernova A supernova (: supernovae or supernovas) is a powerful and luminous explosion of a star. A supernova occurs during the last stellar evolution, evolutionary stages of a massive star, or when a white dwarf is triggered into runaway nuclear fusion ...

. The mass loss rate is – per year, depending on the distance and properties determined for the star.

Nebula

WR 124 is surrounded by an intensely hot nebula formed from the star's extreme stellar wind. The nebula M1-67 is expanding at a rate of over and is nearly 6

light-year A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distances and is equal to exactly , which is approximately 9.46 trillion km or 5.88 trillion mi. As defined by the International Astr ...

s 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 Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...

and stretch out up to . If placed in the

Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...

, one of these clumps would span the distance from the Sun to

Saturn Saturn is the sixth planet from the Sun and the second largest in the Solar System, after Jupiter. It is a gas giant, with an average radius of about 9 times that of Earth. It has an eighth the average density of Earth, but is over 95 tim ...

External links

*http://apod.nasa.gov/apod/ap981109.html *http://hubblesite.org/newscenter/archive/releases/1998/38/image/a

References

{{DEFAULTSORT:WR 124 Wolf–Rayet stars Runaway stars Sagitta Sagittae, QR Merrill's star 094289