Galaxies are what make everything possible. They are complex, enormous, and home to all the stars in the universe. Galaxies come in many different forms; there are spiral, elliptical, irregular, and even merged galaxies. Typically, galaxies don’t just exist alone in space either but are part of a local group. For example, our galaxy, the Milky Way, is part of the Local Group that consists of another, even more massive galaxy known as Andromeda, as well as 52 other galaxies known as Dwarf galaxies. They are much smaller and contain a low number of stars in comparison to the Milky Way and Andromeda. Our Local Group of galaxies are all gravitationally bound, which will lead to an inevitable merger between ourselves and Andromeda in about 4 billion years from now. But outside of our group is a different story as it is Dark Energy that is creating more and more space in between our group of galaxies and the others that exist in outer space. It is truly a remarkable thing that we are able to observe this before our very eyes. The following galaxies are just a handful of the billions of others that exist in the observable universe. The majority of the following text is provided by NASA. From top to bottom, left to right:
Antennae Galaxy: Visible on the upper right, NGC 4038 used to be a normal spiral galaxy, minding its own business, until NGC 4039, toward its left, crashed into it. The evolving wreckage, is known famously as the Antennae. As gravity restructures each galaxy, clouds of gas slam into each other, bright blue knots of stars form, massive stars form and explode, and brown filaments of dust are strewn about. Eventually the two galaxies will converge into one larger spiral galaxy. The Antennae lies 45 million light years away from Earth.
Whirlpool Galaxy: Follow the handle of the Big Dipper away from the dipper’s bowl until you get to the handle’s last bright star. Then, just slide your telescope a little south and west and you might find this stunning pair of interacting galaxies, the 51st entry in Charles Messier famous catalog(M51). Perhaps the original spiral nebula, the large galaxy with well defined spiral structure is also cataloged as NGC 5194. Its spiral arms and dust lanes clearly sweep in front of its companion galaxy (top),NGC 5195. The pair are about 31 million light-years distant and officially lie within the angular boundaries of the small constellation Canes Venatici. Though M51 looks faint and fuzzy to the human eye, deep images like this one can reveal the faint tidal debris around the smaller galaxy.
Centaurus A: At only 11 million light-years distant and spanning over 60,000 light-years across, the peculiar elliptical galaxy is also known as NGC 5128. Forged in a collision of two otherwise normal galaxies, Centaurus A’s fantastic jumble of young blue star clusters, pinkish star forming regions, and imposing dark dust lanes are seen here in remarkable detail. Near the galaxy’s center, left over cosmic debris is steadily being consumed by a central black hole with a billion times the mass of the Sun. As in other active galaxies, that process likely generates the radio, X-ray, and gamma-ray energy radiated by Centaurus A.
Andromeda Galaxy: A mere 2.5 million light-years away, the Andromeda Galaxy really is just next door as large galaxies go. So close, and spanning some 260,000 light-years, its spiral arms stand out in visible light images of Andromeda (also known as M31), the arms look more like rings in the GALEX ultraviolet view, dominated by hot, young, massive stars. As sites of intense star formation, the rings have been interpreted as evidence Andromeda collided with its smaller neighboring elliptical galaxy M32 more than 200 million years ago. The large Andromeda galaxy and our own Milky Way are the dominant members of the local galaxy group. It is also believed to contain close to one trillion stars. For comparison, the Milky Way contains somewhere between 200-400 billion.
Needle Galaxy: Magnificent spiral galaxy NGC 4565 is viewed edge-on from planet Earth. Also known as the Needle Galaxy for its narrow profile, bright NGC 4565 is a stop on many telescopic tours of the northern sky, in the faint but well-groomed constellation Coma Berenices. This sharp, colorful image reveals the galaxy’s bulging central core cut by obscuring dust lanes that lace NGC 4565’s thin galactic plane. An assortment of other background galaxies is included in the pretty field of view, with neighboring galaxy NGC 4562 at the upper left. NGC 4565 itself lies about 40 million light-years distant and spans some 100,000 light-years.
Sombrero Galaxy:This floating ring is the size of a galaxy. In fact, it is part of the photogenic Sombrero Galaxy, one of the largest galaxies in the nearby Virgo Cluster of Galaxies. The dark band of dust that obscures the mid-section of the Sombrero Galaxy in optical light actually glows brightly in infrared light. The above image, digitally sharpened, shows the infrared glow, recently recorded by the orbiting Spitzer Space Telescope, superposed in false-color on an existing image taken by NASA's Hubble Space Telescope in optical light. The Sombrero Galaxy, also known as M104, spans about 50,000 light years across and lies 28 million light years away. M104 can be seen with a small telescope in the direction of the constellation Virgo.
