Old Lace

M33radio_opt_largeThis combined image of radio and visible light observations of the faint galaxy known as M33 looks like lace hanging in the sky. Also known as the Triangulum Galaxy, it is part of the Local Group of galaxies which includes the Andromeda Galaxy and the Milky Way. M33 is over thirty thousand light years across and more than two million light years away. The optical data in this image (mostly white) show the many stars within the galaxy as well as reddish star forming regions that are filled with hot hydrogen gas. The radio data (colored pink) from the Very Large Array (VLA) reveal the cooler hydrogen gas in the galaxy, gas which cannot be seen with an optical telescope. Mergedr, the radio and optical images show a more comprehensive view of star formation in this galaxy.

Image Credit: NRAO


M33M33, the Triangulum Galaxy, is a favorite of astronomers, amateur and professional alike, because of its orientation and relative proximity to us. It is the second nearest spiral galaxy to our Milky Way (after M31, the Andromeda Galaxy) and a part of the “local group” of galaxies. From our perspective, M33’s disk appears at moderate inclination. That permits us to see its internal structure clearly. M31 is oriented nearly edge-on.

The Galaxy Evolution Explorer took this picture of M33 in ultraviolet wavelengths. Ultraviolet imaging mostly shows us emissions from the atmospheres of hot, young stars. Young in this case means only a few hundred million years old. Observations of M33 allow astronomers to compare the population of young, massive stars with other components of the galaxy such as interstellar dust and gas. The clouds contain the raw material from which stars form. This comparison gives us insight into the star formation process as it occurs throughout an entire spiral galaxy and is an important resource for studies of galaxy evolution.

Image Credit: NASA