A gush of light unleashed by the explosive death of a star is the gift that keeps on giving.
The dead star is no longer visible, but the light emitted by the stellar blast, called a supernova, is still reverberating through space three years after the star’s demise was discovered.
This black-and-white movie, assembled from images taken by the Advanced Camera for Surveys aboard NASA’s Hubble Space Telescope, reveals an expanding shell of light from the explosion — a phenomenon called a “light echo” — sweeping through interstellar space. The “echoing” light looks like a ripple expanding on a pond.
The Hubble observations cover a time span of more than two years. The supernova was discovered on Jan. 21, 2014.
The light echo is caused by light scattering off interstellar dust clouds and nicely illustrates that space between stars is not a totally empty void.
The scattered light from the stellar blast travels different distances to arrive at Earth. Some light comes to Earth directly from the supernova blast. Other light is delayed because it travels indirectly. In this case, the light is bouncing off a huge dust cloud that extends 300 to 1,600 light-years around the supernova and is being reflected toward Earth.
The stellar explosion, called SN 2014J, occurred in the nearby starburst galaxy M82, or Cigar Galaxy, 11.4 million light-years away. So far, astronomers have spotted only 15 light echoes around supernovae outside our Milky Way galaxy. Light echo detections from supernovae are rarely seen because they must be nearby for a telescope to resolve them.
SN 2014J is classified as a Type Ia supernova and is the closest such blast in at least four decades. Therefore, the Hubble observations of the stellar blast’s light echo are the most detailed images of a Type Ia supernova. These stars explode in binary systems composed of a burned-out white dwarf star and a companion star. As the companion spills material onto the white dwarf, an explosion may eventually be triggered when the white dwarf can no longer support the extra pressure of the accumulated matter. The details of this process are still the subject of ongoing research.
Publication: November 9, 2017