Missing neutron star found 30 years after supernova explosion

On February 23, 1987, a supernova lit up the night sky, visible to the naked eye. As the closest such event in almost 400 years, it provided the perfect opportunity to study supernovae, but one predicted piece has been missing ever since. Now, more than 30 years on astronomers say they’ve finally found the neutron star that was produced in the explosion.

Supernova 1987A was a once-in-several-lifetimes event, as the first supernova to be visible to the naked eye since 1604. That’s because it was relatively close by – just 168,000 light-years away in the Large Magellanic Cloud, a dwarf galaxy that orbits the Milky Way. It flared up with the power of 100 million Suns, and glowed in the sky for several months. Even after it faded from view, the remnant of the explosion has remained as a cloud of dust and gas that astronomers have continued to study ever since.

But there was still one lingering question. Supernova theory said that a star of that mass should have collapsed into a neutron star, an incredibly small, dense, energetic object that should have been hard to miss. Yet missed it was, for 32 years. Some astronomers insisted it must have been hiding there, behind a thick veil of dust. Others suggested it may have collapsed into a black hole or a quark star – or maybe our theories are completely wrong, and there was nothing left at all.

Now, we may finally have our answer. As part of a new study, researchers from Cardiff University claim to have found that predicted neutron star, hiding in the dust. To do so, the team examined the supernova remnant using the Atacama Large Millimeter/submillimeter Array (ALMA) telescope in Chile.

The astronomers found that one certain patch of the dust looked brighter than the rest at the submillimeter wavelengths that ALMA measures. The neutron star was already suspected to be in this particular area.

“Although the light from the neutron star is absorbed by the dust cloud that surrounds it, this in turn makes the cloud shine in sub-millimeter light, which we can now see with the extremely sensitive ALMA telescope,” says Mikako Matsuura, an author of the study.

The team says that the finding helps confirm that our theories about supernovae are on the right track after all. In future, the researchers say that the dust cloud may start to clear up, making the neutron star directly visible.

The research was published in the Astrophysical Journal.

Source: Cardiff University