WR 102ka

WR 102ka also known as the Peony star is a Wolf-Rayet star that is one of several candidates for the most luminous known star in our Milky Way Galaxy. The nearer star Eta Carinae, which was the second brightest star in the sky for a few years in the 19th Century, appears to be slightly more luminous than WR 102ka, but it is known to be a binary star system. There is also the more recently discovered Pistol star which, like the Peony star, derives its name from the shape of the nebula it is embedded in and which has probably created through heavy mass loss via fierce stellar winds and perhaps also major "mini-supernova-like" eruptions as happened to Eta Carinae around the 1830s-1840s creating the lobes observed by the Hubble Space Telescope.

The luminosities of the Pistol Star, Eta Carinae and WR 102ka are all rendered somewhat uncertain due to heavy obscuration by galactic dust in the foreground, the effects of which must be corrected for before their apparent brightness can be reduced to estimate their physical radiated power, or "bolometric luminosity". Both Eta Carinae and WR 102ka are believed likely to explode as supernovas or hypernovas within the next few million years. As is typical of such extremely massive and luminous stars, both have expelled a considerable portion of their initial mass, when originally formed, in dense, massive stellar winds.

Because WR 102ka lies near the Galactic Center, it is the more distant and heavily obscured of the two, and is essentially totally obscured in visible wavelengths. Thus it must be observed in longer wavelength infrared light, which is able to penetrate the dust. The Spitzer Space Telescope observed WR 102ka at wavelengths of 3.6µm, 8µm, and 24µm on April 20, 2005. The observations were carried out by L. Oskinova, W.-R. Hamann, and A. Barniske of Potsdam University, Germany.

WR 102ka was previously observed by the Two Micron All Sky survey (2MASS) in the near-infrared J, H, and K_s bands, at 1.2µm, 1.58µm, and 2.2µm, respectively.