The newly discovered double star has the shortest orbit of any known black widow. And every 10,000 years, a third, distant star interferes with the pair.

We know that the most barbaric and strange things happen in the universe. A new discovery proves that once again. Astronomers have come across a curious and very rare ‘black widow’. This ‘deadly’ binary star consists of a rapidly spinning neutron star – a pulsar – orbiting a smaller companion. And like its arachnid namesake, the pulsar appears to be slowly devouring its companion.

More about black widows in space
Black widows are binary stars, as mentioned, powered by pulsars; rapidly rotating neutron stars. Pulsars have a dizzying rotational period, emitting flashes of high-energy gamma and X-rays. Normally, pulsars ‘die’ quite quickly, because they burn an enormous amount of energy. But every now and then, a passing star can breathe new life into a pulsar. As a star approaches, the pulsar can steal material from its companion due to its strong gravitational pull. This causes the pulsar to emit new energy, further stripping the companion and eventually destroying it. Due to the striking resemblance to the dreaded black widow spiders that eat their mates, the double stars of the same name go through life.

Black widows in space are very rare. For example, researchers know about two dozen such binary stars. However, the newest candidate, named ZTF J1406+1222, is a special one. The binary star, which is located 3000 light-years away from Earth, turns out to have a record-breaking short orbit of only 62 minutes! This means that the pulsar and its prey complete one orbit around each other every 62 minutes.

third star

While that’s quite curious, the story gets even weirder. The system appears to be home to a third, more distant star that completes one orbit around the two innermost stars every 10,000 years.

Origin

The discovery of this possible triple black widow in space raises questions about how such systems emerge. However, the researchers do have a theory. For example, they suspect that this triple system — likely in the same way as most black widow binary stars — formed from a dense constellation of older stars known as a globular cluster. The cluster in question was then driven closer to the center of the Milky Way. The black hole’s gravity then pulled the cluster apart, leaving the striking triple system intact. “It’s a complicated birth scenario,” said study researcher Kevin Burdge. “This system has probably been orbiting the Milky Way longer than our sun has.”

New Approach

The research team discovered the remarkable triple system thanks to a new method. Although gamma and X-rays emitted by the pulsar normally reveal the existence of a black widow, the researchers made the current study use of visible light. In effect, they were studying the pulsar’s ‘prey’, rather than the pulsar itself. It turns out that the companion’s day side — the side that is constantly facing the pulsar — ​​can be many times hotter than its night side, due to the constant high-energy radiation it receives from the pulsar. “Instead of looking directly for the pulsar, we can try to find the star it is cooking,” Burdge explains. When you see a star’s brightness periodically change dramatically, Burdge reasoned, you may have stumbled upon a black widow.

Candidate

Although the researchers hypothesize that ZTF J1406+1222 is black widow, the team strangely enough did not detect any gamma or X-rays from the pulsar directly. ZTF J1406+1222 is therefore considered a ‘candidate’ for the time being, although the astronomers hope to confirm their suspicions with the help of future observations. “The only thing we know for sure is that we’re seeing a star with a day side much hotter than the night side, orbiting something every 62 minutes,” Burdge sums up. “However, everything seems to indicate that it is a binary black widow. But there’s some weird stuff going on, so it could potentially be something completely new as well.”

The team plans to continue to observe the curious system. In addition, they hope to use their new technique to uncover even more neutron stars and black widows.