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.
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.