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.
The Sagittarius Window Eclipsing Extrasolar Planet Search, or SWEEPS, was a 2006 astronomical survey project using the Hubble Space Telescope's Advanced Camera for Surveys - Wide Field Channel to monitor 180,000 stars for seven days to detect extrasolar planets via the transit method.
The stars that were monitored in this astronomical survey were all located in the Sagittarius-I Window, a rare transparent view to the Milky Way's central bulge stars in the Sagittarius constellation as our view to most of the galaxy's central stars is blocked by lanes of dust. These stars in the galaxy's central bulge region are approximately 27,000 light years from Earth.
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.
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.
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.