Telescope tagging team discovers 10 strange and exotic pulsars

Towards the center of our Milky Way galaxy, in the constellation of Sagittarius, astronomers have discovered 10 monstrous neutron stars. These special stars, called pulsars, reside together in the Terzan 5 globular cluster, a crowded home to hundreds of thousands of different types of stars.

The paper was published in the journal Astronomy and Astrophysics.

Pulsars are millions (or even billions) of times denser than other stars and spin rapidly, emitting bright pulses of light from their strong magnetic fields, making them a beacon for astronomers to find. In one of the most jam-packed places in our Milky Way, many pulsars in Terzan 5 have evolved into weird and strange shapes.

Astronomers already knew that 39 pulsars call Terzan 5 home. With the teamwork of the US National Science Foundation’s Green Bank Telescope (NSF GBT) and the South African Radio Astronomy Observatory’s MeerKAT telescope, 10 more have been added to the number.

“It’s very unusual to find new exotic pulsars. But what’s really exciting is the wide variety of such oddities in a single cluster,” shared Scott Ransom, a scientist with the National Radio Astronomy Foundation’s Observatory US National Science Foundation (NSF NRAO). The discoveries were made by an international team of astronomers from NSF NRAO, the Max Planck Institute for Gravitational Physics (Albert Einstein Institute) (AEI) and the Max Planck Institute for Radio Astronomy.

The Meerkat telescope was able to determine the approximate location of each pulsar by tracking and timing how fast they were spinning, compared to twenty years of observations of Terzan 5 taken by the NSF GBT, which revealed the strange and strange details of these stars.

“Without the NSF Green Bank Telescope archive, we would not have been able to characterize these pulsars and understand their astrophysics,” adds Ransom. The archival NSF GBT data allowed astronomers to determine the position of the pulsars on the sky, measure their specific motions, and see how their orbits changed over time.

Among the discoveries, astronomers saw two possible neutron stars pulled into each other’s orbit as a binary system. Of the 3,600 known pulsars in the galaxy, only 20 have been identified as double neutron star binaries.

When pulsars pair up in binaries, the gravitational pull from one to the other can steal material and energy, causing one to spin even faster, becoming a millisecond pulsar. This pair could be a record breaker, with a new contender for the fastest-spinning pulsar in a binary neutron-star system, and the longest orbit of its kind. The current record holder for the fastest spinning pulsar already resides in Terzan 5. Only future observations will reveal the truth.

Astronomers also observed three new rare “spider” pulsar binary systems (in addition to the five already known in the group) called Redbacks or Black Widows, depending on the types of companion stars they have. A companion star falls into the orbit of a spider pulsar, where a web of plasma fills the space between the two (caused by outflows from the companion star due to the pulsar’s energy) slowly dissipating the companion over time.

The discovery of these strange pulsars allows scientists to better understand globular clusters, neutron stars, and even test Einstein’s theory of general relativity, along with expanding what is known about the categories of pulsars. The research team is already making plans to find even more at Terzan 5, with the support of volunteers.

Citizen scientists who want to share in the excitement of this discovery can help at Einstein@Home. This project, led by scientists at AEI, has already discovered more than 90 new neutron stars.