WR 102

WR 102,  belongs to a class of rare stars known as Wolf Rayet stars. Unlike the spectra of most stars, which are dominated by narrow absorption lines, the spectra of W-R stars show broad emission lines of ionized helium and strongly ionized nitrogen or carbon. The spectra also indicate very high surface enhancement of heavy elements, depletion of hydrogen, and strong stellar winds. WR 102 is also unusual because it belongs to the rare spectral class WO2 being one of the few known oxygen-rich Wolf-Rayet stars, four in the Milky Way and five in other galaxies. It is also the hottest known star, with a temperature of 210,000 K compared to the Sun’s 6000 K. Modeling of the star’s atmosphere yielded an estimated luminosity of 282,000 luminosities of the Sun. It lies at a distance of 9500 light years in the constellation Sagittarius. The star is extremely small and dense for its brightness having a radius 0.58x of the Sun and a mass of 16.7 ± 1.4 solar masses.

A very strong stellar wind at about 5000 km/s results in a loss of mass at a rate of 10^-5 M solar masses/year. By comparison, the Sun loses (2–3) x 10^-14 solar mass per year due to the solar wind, hundreds of millions of times less than WR 102. Stellar wind and ultraviolet radiation leads to strong compression and ionization of the surrounding  interstellar matter that was ejected by the star. The ejected material which makes up the nebula is in the form of a complex structure of arches seen in the image. WO-class stars are in the last evolutionary stage before a supernova explosion. It is likely that WR 102 is in its last stage of nuclear reactions, near the end of helium combustion and will explode as a supernova in the next 1500 years. The large mass and rapid rotation will probably lead to a gamma-ray burst, but it’s not yet clear how fast this star is spinning. I

This image is made using narrowband 3nm filters that capture emissions from Hydrogen and Oxygen gases.  These emissions are created because of ultraviolet light from the central WR 102 star which  excite the Hydrogen and Oxygen gases which then re radiate light at their characteristic wavelengths. The Red color comes from  from Hydrogen emission  and the Blue Green from Oxygen emission.  The image was taken with a 24″ Planewave telescope located in Rio Hurtado, Chile.