galaxy

The Milky Way is smaller than astronomers previously thought, according to new research. For the first time, scientists have been able to precisely measure the mass of the galaxy that contains our solar system. Researchers have found that the Milky Way is approximately half the weight of ou neighboring galaxy – Andromeda – which has a similar structure to our own. The Milky Way and Andromeda are the two largest in a region of galaxies which astronomers call the Local Group.

In this new study, researchers were also able to work out the mass of invisible matter found in the outer regions of both galaxies, and reveal their total weights. They say 90 per cent of both galaxies' matter is invisible. Scientists say that Andromeda's extra weight must be present in the form of dark matter, the little-understood invisible substance which makes up most of the outer regions of galaxies. They estimate that Andromeda contains twice as much dark matter as the Milky Way, causing it to be twice as heavy.

In February of 2012, astronomers using NASA's Hubble Space Telescope discovered a cluster of young, blue stars in the spectacular edge-on galaxy (ESO 243-49 above), encircling the first intermediate-mass black hole ever found. The presence of the star cluster suggests that the black hole was once at the core of a now-disintegrated dwarf galaxy.

Via NASA:

Almost every object in the above photograph is a galaxy. The Coma Cluster of Galaxies pictured above is one of the densest clusters known - it contains thousands of galaxies. Each of these galaxies houses billions of stars - just as our own Milky Way Galaxy does. Although nearby when compared to most other clusters, light from the Coma Cluster still takes hundreds of millions of years to reach us. In fact, the Coma Cluster is so big it takes light millions of years just to go from one side to the other! The above mosaic of images of a small portion of Coma was taken in unprecedented detail in 2006 by the Hubble Space Telescope to investigate how galaxies in rich clusters form and evolve. Most galaxies in Coma and other clusters are ellipticals, although some imaged here are clearly spirals. The spiral galaxy on the upper left of the above image can also be found as one of the bluer galaxies on the upper left of this wider field image. In the background thousands of unrelated galaxies are visible far across the universe.

Via NASA:

These two mighty galaxies are pulling each other apart. Known as the "Mice" because they have such long tails, each spiral galaxy has likely already passed through the other. The long tails are created by the relative difference between gravitational pulls on the near and far parts of each galaxy. Because the distances are so large, the cosmic interaction takes place in slow motion -- over hundreds of millions of years. NGC 4676 lies about 300 million light-years away toward the constellation of Bernice's Hair (Coma Berenices) and are likely members of the Coma Cluster of Galaxies. The above picture was taken with the Hubble Space Telescope's Advanced Camera for Surveys in 2002. These galactic mice will probably collide again and again over the next billion years until they coalesce to form a single galaxy.

Five billion light-years from earth, there's a massive galactic pileup unfolding in slow motion. As four clusters of galaxies plow into each other, thousands of individual galaxies are colliding—creating huge amounts of cosmic chaos and a lot of energy.

New images of this phenomenon—one of the largest galactic mergers on record—suggest it's also producing more than just pretty pictures. It's also serving as quite possibly the largest particle accelerator of all time, besting the exquisitely engineered Large Hadron Collider one million times over.

Why does this galaxy have such a long tail? In this stunning vista, based on image data from the Hubble Legacy Archive, distant galaxies form a dramatic backdrop for disrupted spiral galaxy Arp 188, the Tadpole Galaxy. The cosmic tadpole is a mere 420 million light-years distant toward the northern constellation Draco. Its eye-catching tail is about 280 thousand light-years long and features massive, bright blue star clusters. One story goes that a more compact intruder galaxy crossed in front of Arp 188 - from right to left in this view - and was slung around behind the Tadpole by their gravitational attraction. During the close encounter, tidal forces drew out the spiral galaxy's stars, gas, and dust forming the spectacular tail.

Although they look far apart, M31 and M33 are locked in a mutual gravitational embrace. Radio astronomers have found indications of a bridge of neutral hydrogen gas that could connect the two, evidence of a closer encounter in the past. Based on measurements, gravitational simulations currently predict that the Milky Way, M31, and M33 will all undergo mutual close encounters and potentially mergers, billions of years in the future.