Galaxy For Everyone
NASA's Wide-Field Infrared Explorer, or WISE, the mission team has put together this image showing just a sample of the millions of galaxies that have been imaged by WISE during its survey of the entire sky.
NGC 300 is seen in the image in the upper left panel. This is a textbook spiral galaxy. At about 39,000 light-years across, NGC 300 is only about 40 percent the size of the Milky Way galaxy.
The upper right image shows Messier 104, or M104, also known as the Sombrero galaxy. Although M104 is also classified as a spiral galaxy, it has a very different appearance than NGC 300. In part, this is because the dusty, star-forming spiral disk in M104 is seen nearly edge-on from our point of view. M104 also has a large, ball-shaped bulge component of older stars, seen here in blue.
The large, fuzzy grouping of stars at the center of the lower left panel is the galaxy Messier 60, or M60. This galaxy does not have a spiral disk, just a bulge, making it a massive elliptical galaxy. M60 is about 20 percent larger than the Milky Way galaxy, and lies in the Virgo cluster of galaxies. The brighter dense spot inside but off-center from the blue core of M60 is a separate spiral galaxy called NGC 4647.
Recent evidence suggests there is a black hole at the center of M60 with a mass of about 4.5 billion times that of the sun, making it one of the largest black holes known.
The galaxy in the lower right panel is Messier 51, or NGC 5194, also frequently referred to as the Whirlpool galaxy. The Whirlpool is a "grand design" spiral galaxy. It is interacting with its smaller companion -- NGC 5195, a dwarf galaxy, which can be seen as a bright spot near the tip of the spiral arm extending up and to the right of the larger galaxy. The Whirpool's very bright spiral arms show areas of compressed dust and gas.