This is the dwarf galaxy known as NGC 1140. It lies 60 million light-years away in the constellation of Eridanus. It has an irregular form, much like the Large Magellanic Cloud, a small galaxy that orbits the Milky Way. This small galaxy is undergoing a starburst. Despite being only about one-tenth the size of the Milky Way, it is creating stars at about the same rate—the equivalent of one star the size of our sun being created per year. The galaxy is full of bright, blue-white, young stars.
Galaxies like NGC 1140 are of particular interest to astronomers because their composition makes them similar to the intensely star-forming galaxies in the early Universe, and those early Universe galaxies were the building blocks of present-day large galaxies like our Milky Way. Because they are so far away, the early Universe galaxies are harder to study, so these closer starbursting galaxies are a good substitute for studyingt galaxy evolution.
Its vigorous star formation eventually will have a very destructive effect on this small dwarf galaxy. When the larger stars in the galaxy die and explode as supernovae, the gas blown into space may escape the gravitational pull of the galaxy. The ejection of gas from the galaxy throws away one of the building blocks for future star formation. Thus, NGC 1140’s starburst cannot last for long.
Image Credit: ESA
NGC 1156 is a dwarf irregular galaxy which contains zones of gas rotating in the opposite direction of most of the material in the galaxy. The counter-rotation is thought to be the result of tidal interactions with another gas rich galaxy some time in the past.
Image Credit: NASA / ESA
Henize 2-10 is a dwarf galaxy, and it is the first dwarf galaxy ever discovered to contain a supermassive black hole at its center. This was surprising because the black hole is about one quarter of the size of the one at the center of the Milky Way Galaxy. However, Henize 2-10 is only about1/1,000th the size of the Milky Way..
This image combines x-ray (Chandra), visible light (Hubble), and radio telescope (Very Large Array) views.
Image Credit: NASA / NRAO
When the Hubble Space Telescope photographed the globular star cluster NGC 6752 (located 13,000 light-years away in our Milky Way’s halo), the image revealed a never-before-seen dwarf galaxy cataloged as Bedin 1 located far behind the cluster’s crowded stellar population. The galaxy is only 30 million light-years away but had not been noticed before. It’s classified as a dwarf spheroidal galaxy because it measures only around 3,000 light-years at its greatest extent. Because it’s so small, it’s roughly a thousand times dimmer than the Milky Way.
Because it’s very old, 13 billion years, and relatively isolated, it’s seen hardly any interaction with other galaxies It’s the astronomical equivalent of a living fossil from the early universe.
This composite image above shows the location of Bedin 1 behind the globular cluster NGC 6752. The lower image of the complete cluster is a ground-based observation from the Digitized Sky Survey 2. The upper right image shows the full field of view of the Hubble Space Telescope. The upper left image highlights the region containing the galaxy Bedin 1.
Image Credits: NASA / ESA / DSS / STScI
UGC 4459’s diffused and disorganized appearance is characteristic of an irregular dwarf galaxy. Because they lack distinctive structure or shape, irregular dwarf galaxies are typically chaotic in appearance, with neither a nuclear bulge (a tightly-packed central group of stars) nor any trace of spiral arms extending from the center of the galaxy.
Image Credit: NASA
UGC 5340 is a nearby dwarf galaxy that is a bit of a puzzlement. It seems to be much younger that the Milky Way and the other galaxies in our local group. We don’t know for sure if that true or, if it is, why.
Image Credit: NASA / ESA
UGC 4879 is an irregular dwarf galaxy. It is very isolated, which means that it has not interacted with any surrounding galaxies, making it an ideal laboratory for studying star formation uncomplicated such interactions. Studies of UGC 4879 have revealed a significant amount of star formation in the first 4-billion-years after the Big Bang, followed by a strange nine-billion-year lull in star formation which ended about 1-billion-years ago. That behavior is puzzling, and the solitary galaxy continues to provide ample study material for astronomers looking to understand the complex mysteries of starbirth throughout the Universe.
Image Credit: ESA / NASA