A long standing mystery in astronomy may be solved.  The MUSE (Multi Unit Spectroscopic Explorer) instrument on ESO's Very Large Telescope in Chile has given astronomers the best view so far of what is happening to a galaxy as it ploughs through a cluster.

Scientists have wondered how a blue gas-rich galaxy (producing new stars) can become a red gas-poor galaxy (non-star producing) in a short period of time.  What factors are at play?  For the first time, observations have been made of a galaxy as it moves through a galaxy cluster.

MUSE observed a spiral galaxy, ESO 137-001 located 200 million light years away in the constellation Triangulum Australe (the Southern Triangle).  ESO 137-001 is traveling at several million kilometers per hour as it moves through the Norma Cluster.  The galaxy is being stripped of most of it gas which is needed for star formation.

MUSE can measure the entire spectrum for each pixel in the frame when it takes a photo.  It can collect about 90,000 spectra every time it looks at an object.  This reveals the motions and properties of the gases and objects in a highly detailed map.

As the galaxy moves through the cluster, gas in the cluster is heated to several million degrees and pushes the cooler gas out of ESO 137-001.  The gas thrown out of ESO 137-001 forms a long tail behind the galaxy much like a comet tail.  The tail extends out over 200,000 light years.

MUSE has discovered that the motion of the blown away gas, along with the motion of the stars in the galaxy remains unchanged.  This indicates that the cluster gas itself, and not gravity, is the factor at work.  This process is known as ram-pressure stripping.

The thin spiral arms are the first parts of the galaxy to lose its gas, followed by the center of the galaxy.  Soon all the star-forming gas will be completely stripped out of ESO 137-001 leaving it without any materials needed to make new stars.

Two stars are merging and in about 700 million years will ignite a vast supernova explosion.

ESO's Very Large Telescope in Chile was used to observe the strange lopsided planetary nebula known as Henize 2-428 in the constellation Aquila.  Astronomers discovered that the central star was actually a pair of stars.  One theory of how certain bubble-shaped nebula such as the Cat's Eye nebula formed involved the presence of two stars.  These observations support that theory.

Telescopes in the Canary Islands continued the observations and determined the orbit of the two stars, their mass and their separation.  They found each star has a mass slightly less than our sun and they orbit each other every four hours.  They are close enough to each other that according to Einstein's theory of general relativity will get closer and closer to each other eventually merging into a single star.  The resulting star will be so massive that it will collapse in on itself exploding as a Type 1a supernova.

Until now, a pair of stars merging together and exploding as a supernova was just theory.  But now astronomers have actually found two stars at the center of a nebula.  When they eventually explode, the shock waves of gas will blow out into the existing nebula forming "bubbles" like we see in the Cat's Eye and other nebula.

The VISTA telescope at ESO's Paranal Observatory in Chile is mapping the southern sky. VISTA observes in the infrared allowing it to see through dust filled areas and reveal what is behind it.  As part of the survey VISTA is looking at the central regions of the Milky Way which is heavily filled with dust and gas.  The telescope searches for new and hidden objects.

The VVV (VISTA Variables in the Via Lactea) survey is observing the same areas of the sky at different times to locate and identify any objects that change over time.  Recently, the VVV survey looked at the Triffid Nebula and has discovered two unknown and distant Cepheid variable stars behind it., the first such stars found in the central plane of the Milky Way.  They lay beyond the central bulge of the Milky Way on the other side of the galaxy.

Cepheid variables are a type of bright star that is unstable and slowly brightens and then dims over time.  These Cepheid variables found by VISTA brighten and fade over a period of eleven days.

The view VISTA sees of the sky is completely different from what we see in the visible spectrum looking through a telescope.  We see the Triffid, for example, in blue and red with dark lines through it.  VISTA sees through all of that dust and gas and reveals the cosmos beyond.  Using VISTA astronomers will be able to gain new insight on known objects and discover unknown objects further out in the galaxy.