his photograph from the NASA Hubble Space Telescope presents the first clear view of one of the hottest known stars, the central star of nebula NGC 2440 in our Milky Way galaxy. The superhot star, called "the NGC 2440 nucleus" is the bright white dot in the center of this photograph. In previous photographs made with telescopes on the ground, blurring due to the atmosphere acted to smear together the light from the star with the glow of the surrounding nebula. By clearly separating the starlight from the nebular glow, astronomers have been able to make the most accurate estimate yet for the star temperature: a torrid 200,000 degrees Celsius (or 360,000 degree Fahrenheit) or more.
The picture was obtained with Hubble's Planetary Camera by scientists led by astrophysicist Dr. Sally Heap of NASA's Goddard Space Flight Center in Greenbelt, MD. It has been sharpened by computer image restoration. The brightness of the star compared to that of the surrounding nebula implies that the star, at a minimum of 200,000 K, is one of the hottest stars on record. "The Hubble photo also reveals intricate structure in the nebula that was not discernible in photos made from the ground," according to Dr. Heap. The nebula NGC 2440 was once described as "so complex it defies description," (a statement attributed to the late University of California astronomer Dr. Rudolph Minkowski) and this is the first time that its internal structures, consisting of filaments and oppositely directed blobs and streamers, have been shown in such great detail.
Credit: S. Heap, NASA/Goddard Space Flight Center