G54.1+0.3, supernova remnant in Sagitta

 
G54.1+0.3, supernova remnant in Sagitta

SNR G54.1+0.3 is the dusty remnant of a core-collapse supernova explosion of about 17 light years across, located some 20,000 light-years away in the northern constellation Sagitta, the Arrow.

The general picture for a core-collapse supernova – goes something like this. When the nuclear power source at the center of a star is exhausted, the core collapses. In less than a second, a neutron star (or a black hole, if the star is extremely massive) is formed. The formation of a neutron star releases an enormous amount of energy in the form of neutrinos and heat, which reverses the implosion. All but the central neutron star is blown away at speeds in excess of 50 million kilometers per hour as a thermonuclear shock wave races through the now expanding stellar debris, fusing lighter elements into heavier ones and producing a brilliant visual outburst that can be as intense as the light of several billion Suns.

In this composite image of G54.1+0.3 X-rays from Chandra were overlaid on infrared data from Spitzer. X-rays from Chandra are seen in blue, and data from Spitzer in green (shorter wavelength infrared) and red-yellow (longer wavelength infrared).

The dust in G54.1+0.3 is flying past and engulfing a nearby family of stars. Scientists think the stars in the image are part of a stellar cluster in which the supernova exploded. The material ejected in the explosion is now blowing past these stars at high velocities.

The white source near the center of the image is PSR J1930+1852, a dense, rapidly rotating (7 times per second) neutron star, or pulsar, left behind after the supernova explosion. This pulsar, with a very-high-energy gamma-ray emission, is one of the youngest and most energetic pulsars in our galaxy. It generates a pulsar wind nebula, a wind of high-energy particles — seen in blue — that expands into the surrounding environment, illuminating the material ejected in the supernova explosion.

The energetic flow of radiation and particles from the pulsar also created a ring of particles and two jet-like structures (lighter blue).

During the supernova event, the pulsar is highly magnetized and creates an enormous electric field as it rotates. The electric field accelerates particles near the pulsar and produces jets blasting away from the poles, and as a disk of matter and anti-matter flowing away from the equator at high speeds. As the equatorial flow rams into the particles and magnetic fields in the nebula, a shock wave forms. The shock wave boosts the particles to extremely high energies causing them to glow in X-rays and produce a bright ring. The particles stream outward from the ring and the jets to supply the extended nebula.

The infrared shell that surrounds the pulsar wind is made up of gas and dust that condensed out of debris from the supernova. As the cold dust expands into the surroundings, it is heated and lit up by the stars in the cluster so that it is observable in the infrared. The dust closest to the stars is the hottest and is seen to glow in yellow in the image. Some of the dust is also being heated by the expanding pulsar wind as it overtakes the material in the shell.

The unique environment into which this supernova exploded makes it possible for astronomers to observe the condensed dust from the supernova that is usually too cold to emit in the infrared. Without the presence of the stellar cluster, it would not be possible to observe this dust until it becomes energized and heated by a shock wave from the supernova. However, the very action of such shock heating would destroy many of the smaller dust particles. In G54.1+0.3, astronomers are observing pristine dust before any such destruction.

Image Credit: X-ray: NASA/CXC/SAO/T.Temim et al.; Infrared: NASA/JPL-Caltech

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