Astronomers have performed one of the highest resolution surveys in astronomical history, imaging two extremely intense regions of radiation around a pair of stars that orbit each other. To get a sense of the scale involved in the study, imaging using a telescope on Earth to see a flea on the surface of Pluto, which is 4.67 billion miles (7.5 billion kilometers) away from us.
This groundbreaking observation was made possible by the rare alignment and characteristics of a pair of stars orbiting each other roughly 6,500 light-years away. One is a brown dwarf — a substellar object that has an intermediate mass between a planet and a star — with a “wake” or comet-like tail. The other is rapidly spinning neutron star called a pulsar that emits a pulse of electromagnetic radiation, akin to a lighthouse.
The pulsar is only a few kilometers across but due to its incredibly high density, it’s more massive than our sun.
“The gas is acting as like a magnifying glass right in front of the pulsar,” said Robert Main, lead author of the new study published in the journalNature. “We are essentially looking at the pulsar through a naturally occurring magnifier which periodically allows us to see the two regions separately.” Main, who is a Ph.D. student at the Department of Astronomy & Astrophysics at the University of Toronto, worked closely with colleagues at the University of Toronto’s Dunlap Institute for Astronomy & Astrophysics and Canadian Institute for Theoretical Astrophysics, and the Perimeter Institute.
As the pulsar spins over 600 times a second, it emits a beam of high-power radiation from two hotspots on its surface. The less massive brown-dwarf star orbits the pulsar very quickly, in just over 9 hours, tracing a radius of roughly two million kilometers in size.
Since the brown dwarf star is so close to the pulsar, it gets blasted by the strong radiation beam, on only one side of the tidally-locked dwarf star. What should have been a relatively cool object actually is as hot as the sun’s surface, somewhere around 6000° C.
In time, the intense radiation will erode the brown dwarf until its matter is consumed by the pulsar, whose gravity will funnel gas and dust towards its center. For this reason, pulsars in this sort of binary system configuration are unceremoniously called ‘black widows,’ after the famous spider that eats its mate.
That’s pretty bad news for the brown dwarf, but on the flip side, it’s a great opportunity for science. Because of the way the brown dwarf’s mass alters light from the pulsar, Main and colleagues were able to make out features around the star some 20 kilometers apart — which is incredibly small, if you consider the scales and sizes involved here.
An important caveat is that these features were recorded as data points and not as optical images. This means that for the average viewer, the images won’t mean much. But ultimately, for the researchers, the data they’ve gathered is a veritable gold mine, which will allow them to better their understanding of the dynamics of pulsar-brown dwarf systems.
What’s more, the findings might offer valuable clues to the nature of mysterious phenomena known as Fast Radio Bursts, or FRBs.
“Many observed properties of FRBs could be explained if they are being amplified by plasma lenses,” say Main. “The properties of the amplified pulses we detected in our study show a remarkable similarity to the bursts from the repeating FRB, suggesting that the repeating FRB may be lensed by plasma in its host galaxy.”