It appears that the smallest and densest stars in the universe may rival black holes in their ability to spit out extremely powerful jets to speeds almost matching that of light, according to astronomers using the Karl G. Jansky Very Large Array (VLA) located on the Plains of San Agustin in New Mexico.
The stars that have come forward are known as neutron stars – dense objects that are made in the aftermath of a supernova explosion. Neutron stars are the second most compact forms of matter in the known universe after black holes. “These things are typically about one and a half times the mass of the Sun and yet they’re only ten to 15 kilometres (6.21 to 9.32 miles) across, so they’re incredibly dense,” says James Miller-Jones from the Curtin University node of the International Centre for Radio Astronomy Research (ICRAR) in Western Australia.
Black holes and neutron stars can be found in binary systems where they siphon gas from their normal companion star, which causes them to blast out powerful jets at breakneck speeds. Previously, it was believed that black holes were the kings of making powerful jets – even the smallest amount of material that they consume can kickstart an enormous amount of activity.
That is until astronomers came across the neutron star PSR J1023+0038 – a millisecond pulsar that spends years at a time doing very little in the way of consuming its companion star, only occasionally coming out of starvation mode. When observed in the year 2013 and later in 2014, it was only sipping a trickle of material, which left astronomers believing that the compact star would only release a feeble jet. “Unexpectedly, our radio observations with the Very Large Array showed relatively strong emission, indicating a jet that is nearly as strong as we would expect from a black hole system,” says Adam Deller of ASTRON, the Netherlands Institute for Radio Astronomy. “It’s surprising and it tells us that something we hadn’t previously suspected must be going on in some systems that include a neutron star and a much more normal companion star.”
To date, there is only one other neutron star we know of that throws out powerful jets capable of rivalling the ones made by black holes. “This is casting neutron stars in a new light and showing that they can sometimes launch jets to rival those coming from black holes,” concludes Miller-Jones.