The most recent supernova explosion in the Milky Way.

Scientists have found the likely trigger for the most recent supernova in the Milky Way, by studying the remnant called G1.9+0.3. This object belongs to a special class of supernovas called Type Ias used to measure the expansion rate of the Universe. By combining data from Chandra (seen in this image where red, green, and blue show low, medium, and high-energy respectively) and the VLA, scientists have determined that a merger of two white dwarf stars triggered the supernova in G1.9+0.3. It is important to identify the trigger mechanism for Type Ias because this could affect their use as "standard candles" in cosmology.
Credit: X-ray NASA/CXC/CfA/S.Chakraborti et al.


Type Ia supernovae, have been used to measure distances in space and have helped astronomers to measure the accelerating expansion of the Universe. Since the brightness of these objects is known, scientists can estimate their distance by analyzing how dim they appear. Type Ia supernovae occur in binary systems but there are two possible mechanisms that can trigger such an explosion. In both cases one of the stars is a white dwarf that accumulates material from a companion star, but the companion star can be either a giant star or another white dwarf. Knowing the exact triggering mechanism is essential for astronomers, since if there are more than one mechanism, the contribution from each mechanism may change over time. If this is the case then scientists need to recalibrate some of the ways they use to measure distances in cosmology.

G1.9+0.3 belongs to the Type Ia category and has been identified as the remnant of the most recent supernova in our Galaxy that occurred about 110 years ago. Using data from NASA’s Chandra X-ray Observatory and the NSF’s Jansky Very Large Array astronomers observed that the X-ray and radio brightness of the object increased with time. This indicates that this supernova explosion was triggered by two white dwarfs. It is, however, unclear if this result implies that all Type Ia supernovae are caused by white dwarf collisions. More observations from similar objects in nearby galaxies will help us better understand what causes these impressive explosions and improve our understanding regarding the expansion rate of our Universe.


Publication: Chakraborti et al. 2016

Source: Chandra