Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

July 21, 1998
See Explanation.  Clicking on the picture will download 
 the highest resolution version available.

Nearby Spiral M33
Credit & Copyright: D. Malin (AAO), IAC, RGO, Isaac Newton Telescope

Explanation: M33 is a prominent nearby spiral galaxy. Nicknamed the Triangulum, M33 is one of the larger members of the Local Group of Galaxies. Two massive spiral galaxies dominate the Local Group: M31 and our Milky Way Galaxy. M33 is the only other spiral galaxy known in the Local Group. At 3 million light-years, M33 is the second closest spiral galaxy. M33 is thought by some to be a satellite galaxy to massive M31. M33 is close enough to appear twice the angular size of the full moon, when viewed with binoculars. Globular clusters in M33's halo appear unusual and might be much younger than globular clusters in our Galaxy's halo.

Tomorrow's picture: Dark Craters on Ganymede

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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)
NASA Technical Rep.: Jay Norris. Specific rights apply.
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&: Michigan Tech. U.