UV stars tell how Milky Way evolved
doi:10.1038/nindia.2014.62 Published online 7 May 2014
Researchers have developed a model of stellar population synthesis that provides insights into the structure and evolution of the Milky Way 1. They developed the model based on ultraviolet images of stars obtained by a space telescope.
Previous models have been based on surveys of the Milky Way performed at visible and infrared wavelengths. As these surveys did not include stars that predominantly emit at ultraviolet wavelengths, they excluded hot blue stars, such as white dwarfs, that lie deep within the Milky Way.
To obtain a comprehensive picture of the galaxy, the researchers analysed images captured by the Galaxy Evolution Explorer (GALEX), an ultraviolet space telescope. This telescope took images of hot stars that have emissions at near- and far-ultraviolet wavelengths. The researchers then developed their model based on these images of hot stars.
They found that hot stars, such as white dwarfs and blue horizontal branch stars, were dominant. They also found that bright stars emitting at near-ultraviolet wavelengths have thin disks. However, thick-disk stars emitting at near-ultraviolet wavelengths constitute about 60 per cent of the total stars in the Milky Way.
White dwarfs are the final stage of stellar evolution. The researchers say that white dwarfs provide important information about the star-formation history of the Milky Way. They add that ultraviolet light can be used to identify hot stars, because hot objects emit most of their light at ultraviolet wavelengths.
- Pradhan, A. C.et al. A stellar population synthesis model for the study of ultraviolet star counts of the Galaxy. Astron. Astrophys.(2014) doi: 10.1051/0004-6361/201321757