Astronomical Observatory: Cool Images

Astr112 Photography Projects, Spring 2005

Holmberg II Jonathan derNederlanden

Holmberg II is an irregular dwarf galaxy that belongs to the M81 group, lying close to 9.8 million light years away.The linear size of Holmberg II 50 kly. Also known as UGC 4305, it is one of nine low-surface-brightness galaxies discovered by Erik Holmberg in the 1950's. Holmberg II is often studied as its closeness, lack of density waves and deformation caused by the pull of other galaxies form an ideal environment for observing star formation.

This photograph was taken on a 16" Schmidt-Cassgrain reflector with a clear filter and 300 seconds of exposure. The bright spots in the photo are areas of massive star formation containg hundereds of young, blue, O stars. In June of 2004, astronomers discovered, at the center of the galaxy a strong X-ray source. It has since been found that this is the result of the first ever observation of a nebulae powered by an intermediate-massed black hole.

References:
http://anzwers.org/free/universe/galgrps/m81.html
http://www.daviddarling.info/encyclopedia/H/Holmberg_II_Dwarf.html
http://www.maris.com/content/index.php3?id=20&mode=rs5_u&cur=5001