News in Science

Mysterious supernova still astounds astronomers

StarStuff image of the week This is Supernova SN 1987A, one of the brightest stellar explosions since the invention of the telescope more than 400 years ago.

Supernova 1987A exploded in the Large Magellanic Cloud, a nearby galaxy about 168,000 light-years away.

The light from the supernova arrived here in 1987.

Dominating the image are three glowing loops of stellar material, formed when the fast expanding supernova collided with the dense, slower moving material in the stellar wind.

This stellar wind was ejected by the former star about 20,000 years before it went supernova.

These collisions cause intense heating and the production of powerful optical and X-ray energy emissions.

Outer, ejected materials lit up first, followed by the innermost materials powered by radioactive isotopes, such as cobalt-56, which decayed into iron-56.

There are still many mysteries surrounding these structures, and their origin remains largely unknown.

Another mystery is that of the missing neutron star at the heart of the supernova.

The star that exploded to create SN1987A was a blue supergiant known as Sanduleak -69° 202.

Blue supergiants can have surface temperatures of over 50,000°C, and can be a million times as luminous as the Sun.

The violent death of a high-mass star, such as SN 1987A, leaves behind a stellar remnant in the form of either a neutron star or a stellar mass black hole.

However astronomers have been unable to find a neutron star in the remnants of SN1987A, possibly because it's surrounded by an extremely dense cloud of thick dust.

It's also possible that so much material fell back onto the neutron star that it further collapsed into a stellar mass black hole.

Lopsided blast

Now, new data from NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, shows that the star exploded in a lopsided or asymmetrical blast, sending most of the ejected debris and material flying off in one direction, and the stellar core in the other.

NuSTAR found the "smoking gun" in the form of a radioisotope called titanium-44 which is produced at the core of a supernova explosion, providing astronomers with a direct probe into the mechanisms of a detonating star.

Titanium-44 continues to blaze in the supernova remnant due to its long half-life of around 60 years.

The NuSTAR data reveals that titanium-44 is moving away from us with a velocity of 2.6 million kilometres per hour.

The new findings follow similar observations made by NuSTAR last year of another supernova remnant, called Cassiopeia A, which also produced evidence of an asymmetrical explosion.

Together, these results suggest that lopsidedness is at the very root of core-collapse supernovae.

The image is based on observations undertaken with the High Resolution Channel of the Hubble Space Telescope's Advanced Camera for Surveys.

Related: How do astronomers use light to study stars and planets?

Hosted by Stuart Gary, StarStuff takes us on a weekly journey across the universe. StarStuff reports on the latest news and discoveries in science, with a special focus on astronomy, space sciences and cosmology.



