Some of the brightest stars in nearby galaxies are actually multiple star systems and star clusters according to recent observations with the Hubble Space Telescope. The discovery, made by Michele Cappellari and colleagues using the Wide-Field Planetary Camera on Hubble, means that astronomers will have to re-evaluate theories of star formation in these galaxies (The Astrophysical Journal 515 April 10 1999).
The stellar history of local galaxies is calculated by plotting the different size and brightness of stars in the target galaxy. However, when viewed from Earth, star systems and star clusters can sometimes appear as a single bright star.
The photographs taken with the Wide-Field Planetary Camera indicate that this mistake has happened with at least half of the stars previously identified in galaxy NGC 205. This led Cappellari and colleagues to calculate that in the last 100 million years, 1000 solar masses of gas has been turned into stars in this galaxy. They also suggest that this leads to one final puzzle – where did the gas come from? They speculate that high velocity hydrogen clouds may be orbiting NGC 205.
