A Lonely Dwarf


The Local Void is a vast, empty region of space adjacent to the Local Group, the group of galaxies that included our Milky Way. It’s composed of three separate sectors which are separated by bridges of “wispy filaments” of gas and dust. The exact size of the Local Void is unknown, but it is at least 150 million light-years across—and possibly 3 to 6 times larger still. It’s called a void because it has significantly fewer galaxies than expected from standard cosmology.

The irregular dwarf galaxy in the foreground of the picture is cataloged as KK 246, and it’s one of the few galaxies in the Local Void.

Image Credit: NASA / ESA

The Fornax Dwarf Spheroidal


Fornax_dwarf_galaxy
The Fornax Dwarf Spheroidal is an elliptical dwarf galaxy found in the constellation Fornax. The galaxy is a satellite of the Milky Way and contains six globular clusters. NGC 1049, the largest of its clusters, was discovered before the galaxy itself. The galaxy is receding from the Milky Way at 53 km/s.

Image Credit: ESO

Henize 2-10


A dwarf starburst galaxy about 30 million light years from Earth.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

A Starbursting Galaxy


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

Henize 2-10


A dwarf starburst galaxy about 30 million light years from Earth.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

A Recently Discovered Dwarf Galaxy


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

A Disorganized Dwarf


A distinctly disorganised dwarfUGC 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

A Hermit Galaxy


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

I Zwicky 18


I_Zwicky_18I Zwicky 18 is a dwarf irregular galaxy located about 59 million light years away. Spectroscopic observations with ground-based telescopes showed that I Zwicky 18 to be almost completely made up of hydrogen and helium, the main ingredients created in the Big Bang, and galaxies with I Zwicky 18’s youthful appearance are typically found only in the early universe. Initial observations with the Hubble Space Telescope suggested an age of 500 million years, but later Hubble observations found faint, older stars in the galaxy, suggesting its star formation started at least one billion years ago and possibly as much as ten billion years ago. It’s possible that the galaxy may have formed around the same time as most other galaxies.

Image Credit: NASA / ESA

Dwarfs


dwarf galaxyHappy, Sneezy, Dopey, … No, no … Balin, Bifur, Bofur, … No, not them either. This post is about one of the dwarf galaxies that is part of the M101 group. Ursa Major (The Great Bear) is home to Messier 101, the Pinwheel Galaxy. Messier 101 is one of the biggest and brightest spiral galaxies in the night sky. Like the Milky Way, Messier 101 is not alone with smaller dwarf galaxies in its neighborhood. NGC 5477, which is the main subject of the Hubble Space Telescope image above, is one of those companion galaxies. It’s a typical irregular dwarf galaxy with no obvious structure but plenty of signs of new star creation. The bright nebulae that extend across the galaxy are clouds of glowing hydrogen gas in which those new stars are forming. These glow pinkish red in real life, but appear white in this false color image which was taken through green and infrared filters using Hubble‘s Advanced Camera for Surveys. The field of view is about 3.3 arcminutes wide.

The picture includes numerous galaxies in the background; some are visible right through NGC 5477. This demonstrates that galaxies, far from being solid, opaque objects, are actually largely made up of the empty space between their stars.

Image Credit: NASA

A Dwarf Tadpole Galaxy


This Hubble Space Telescope image shows a firestorm of star birth is lighting up one end of the dwarf galaxy Kiso 5639. Kiso 5639 is really shaped like a pancake but, from our point of view, it seems to have brilliant blazing head and a long, starry tail. Its appearance earns it a place in the “tadpole” class of galaxies.

The bright pink head is glowing of hydrogen lit by radiation from new stars grouped into large clusters that less than a million years old.

Image Credit: ESA / NASA

NGC 1569


The NGC 1569 is a relatively nearby dwarf irregular galaxy in Camelopardalis. It’s characterized by a large starburst that has formed stars at a rate 100 times greater than that of the Milky Way during the last 100 million years.

The spectrum of NGC 1569 is blueshifted. This means that the galaxy is moving towards the Earth. In contrast, the spectra of most other galaxies are redshifted because of the expansion of the universe.

Image Credit: NASA

A Dwarf Galaxy


NGC 5949 is a dwarf galaxy around 44 million light-years from us. NGC 5949 is a relatively bulky example of a dwarf galaxy with a mass of about one percent of the Milk Way’s. It’s classified as a dwarf because of its relatively small number of constituent stars, but with loosely-bound spiral arms it is also classified as a barred spiral galaxy.

Image Credit: ESA / NASA

A Lonely Dwarf


Wolf – Lundmark – Melotte (WLM) is a lonely dwarf galaxy named for the three astronomers who discovered it. It’s about 3 million light-years from the Milky Way in the constellation Cetus, and it’s one of the most remote members of our local galaxy group. It’s so isolated that it may never have interacted with any other local group galaxy.

Image Credit: ESO

A Dwarf Starburst Galaxy


NGC 1705 is a oddball irregular dwarf galaxy undergoing a starburst. It’s about 17 million light-years from the Earth in the constellation Pictor. Dwarf galaxies were probably the first systems to collapse and start forming stars in the early universe. They represent the building blocks from which more massive objects (such as spiral and elliptical galaxies) were formed through mergers. The remaining dwarf galaxies are thought to be the leftovers of the galaxy-formation process.

Image Credit: NASA

NGC 4214


ngc-4214This is dwarf galaxy NGC 4214 which is forming clusters of new stars from its interstellar gas and dust. The young clusters of new stars are within glowing gas clouds. The gas glows because it is excited by the strong ultraviolet light emitted from the young stars forming in the gravitational collapse of the gas. These hot stars eject stellar winds moving at thousands of km/s which blow bubbles in the gas. Near the center of the galaxy, there is a cluster of hundreds of massive blue stars, each more than 10,000 X brighter than our Sun, and a huge bubble inflated by stellar winds and radiation pressure surrounds the cluster.

Image Credit: NASA / ESA

The Skyrocket Galaxy


Kiso 5639A firestorm of star birth is lighting up one end of the diminutive galaxy Kiso 5639. The dwarf galaxy is shaped like a flattened pancake, but because we see it edge-on, it resembles a skyrocket with a blazing head and a long tail.

Kiso 5639 is rare among nearby galaxies. It’s an example of a sort of elongated galaxies that occur in abundance at larger distances, where we observe the universe during earlier epochs. The bright gas in the galaxy’s head contains fewer heavier elements (referred to as “metals” by astronomers) such as carbon and oxygen than the rest of the galaxy. Stars consist mainly of hydrogen and helium, but cook up other “heavier” elements. When the stars die, they release their heavy elements and enrich the surrounding gas.

The galaxy, located 82 million light-years away, has taken billions of years to develop because it has been drifting through an isolated “desert” in the universe, devoid of much gas. Several dozen clusters of stars have been observed in the galaxy’s star-forming head, which spans 2,700 light-years across. These clusters have an average age of less than a million years. Other star formation is taking place throughout the galaxy but on a much smaller scale. Star clusters in the rest of the galaxy are between several million to a few billion years old. Observations suggest that less than a million years ago, Kiso 5639’s leading edge encountered a filament of gas in intergalactic space. The filament could have lost a large amount of matter the galaxy, stoking the vigorous star birth.

Image Credit: NASA