Dwarf Galaxy M60-UDC1

This NASA/ESA Hubble Space Telescope image shows the dwarf galaxy M60-UDC1. Lying about 50 million light-years away, M60-UCD1 is a tiny galaxy with a diameter of 300 light-years – just 1/500th of the diameter of the Milky Way! Despite its size it is pretty crowded, containing some 140 million stars.

The dwarf galaxy may actually be the stripped remnant of a larger galaxy that was torn apart during a close encounter with its neighbor, a massive galaxy called Messier 60.

Circumstantial evidence for this comes from the recent discovery of a monster black hole, which is not visible in this image, at the center of the dwarf. The black hole makes up 15 percent of the mass of the entire galaxy, making it much too big to have formed inside a dwarf galaxy.

Image credit: NASA, ESA and A. Seth (University of Utah, USA)

Note: For more information, see Big Surprises Can Come in Small Packages - Hubble Helps Astronomers Find Smallest Known Galaxy With Supermassive Black Hole.

M60-UCD1

M60-UCD1: A galaxy about 54 million light years from Earth.

The densest galaxy in the nearby Universe may have been found. The galaxy, known as M60-UCD1, is located near a massive elliptical galaxy NGC 4649, also called M60. This composite image of M60 and the region around it presents X-rays from Chandra (pink) and optical data from Hubble (red, green, and blue). The Chandra image shows hot gas and double stars containing black holes and neutron stars, and the HST image reveals stars in M60 and neighboring galaxies including M60-UCD1. The inset is a close-up view of M60-UCD1 in an HST image. The density of stars in M60-UDC1 is about 15,000 times greater than found in Earth’s neighborhood in the Milky Way, meaning that the stars are about 25 times closer.

Scale: Image is 3.2 arcmin on a side (about 50,000 light years).

Image credit: X-ray: NASA/CXC/MSU/J.Strader et al, Optical: NASA/STScI

Note: For more information, see M60-UCD1: NASA's Hubble and Chandra Find Evidence for Densest Nearby Galaxy.

ARP 116

Two very different galaxies feature in this image taken by the NASA/ESA Hubble Space Telescope, forming a peculiar galaxy pair called Arp 116.

Arp 116 is composed of a giant elliptical galaxy known as Messier 60, and a much smaller spiral galaxy, NGC 4647.

Astronomers have long tried to determine whether these two galaxies are actually interacting. Although they overlap as seen from Earth, there is no evidence of new star formation, which would be one of the clearest signs that the two galaxies are indeed interacting. However, recent studies of very detailed Hubble images suggest the onset of some tidal interaction between the two.

Photo credit: NASA, ESA

Note: For more information, see A Family Portrait of Galaxies.

Nearby Galaxies

To celebrate the one-year anniversary of the launch of 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. In fact, it is such a good representation of a spiral galaxy that astronomers have studied it in great detail to learn about the structure of all spirals in general. Infrared images like this one from WISE show astronomers where areas of gas and warm dust are concentrated -- features that cannot be seen in visible light. This gas and dust is primarily found near star-forming regions in the spiral arms. There isn't a significant amount of gas and dust in the central core in this type of spiral galaxy, so it appears relatively dim. 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. In visible light, a dark dust lane extends across the galaxy, blocking out some of the bright starlight in the disk behind it, and causing it to resemble a sombrero. This dust lane encircles the entire galaxy and glows brightly in infrared; it is seen here as bright circle surrounding a dense galactic core.

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. In visible light, M60 is much brighter than NGC 4647. However, in the longest infrared wavelengths that WISE sees, the opposite is true. 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. Two more galaxies are near the upper left corner of this panel, NGC 4638 (the brighter one) and NGC 4637. In addition, two different asteroids were caught crossing the field of view when WISE imaged this portion of the sky (seen as dotted green lines extending out from M60 at about the 2 o'clock and 8 o'clock positions).

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. These arms have been enhanced by the recent encounter with NGC 5195.

These images were made from observations by all four infrared detectors aboard WISE. Blue and cyan represent infrared light at wavelengths of 3.4 and 4.6 microns, which is primarily light from stars. Green and red represent light at 12 and 22 microns, which is primarily light emitted from warm dust.

WISE launched into space aboard a Delta II rocket on December 14, 2009, from Vandenberg Air Force Base, California.

Photo credit: NASA/JPL-Caltech/UCLA