Black Widow Star Circles Hourly

May 6, 2022 | Daily Space, Neutron Stars / Pulsars, Stars

IMAGE: An illustrated view of a black widow pulsar and its stellar companion. The pulsar’s gamma-ray emissions (magenta) strongly heat the facing side of the star (orange). The pulsar is gradually evaporating its partner. CREDIT: NASA’s Goddard Space Flight Center/Cruz deWilde

Folks, it is a star-eat-star world out there. Earlier this week, we mentioned a supernova explosion that came about from a star having its atmosphere eaten off. Now, we have news from MIT of another star system that includes a tiny, dense pulsar that is pulling material off its nearest companion star, while a third star shines on from a safe distance.

The two inner stars circle in a deadly tango every 62 minutes, while the outer object goes around every 10,000 years.

Cataloged as ZTF J1406+1222 and classified as a black widow binary, the inner pulsar is sustaining its high-speed spin by stealing rotation from its mate. Normally, pulsars slow down over time, but black widows instead devour mass, and with it angular momentum, from their companion stars, allowing them to look younger than they are and to stay young looking longer.

This really is the stuff of a horror novel.

The roughly one-hour orbit of the pulsar and its dying mate is the shortest orbital period so far observed for this kind of system. It also varies in optical brightness in a novel way: the pair appears to dim and fade by a factor of thirteen. This can’t be explained just as the one star blocking the light from the other and then allowing it to be seen again. Instead, it appears that the larger-sized and lower-mass companion is being heated up by the pulsar and locked in a death grip. As the two orbit, the heated side of the companion comes in and out of view, and that heated side is just brighter; it is like it is screaming out in light to point out where it is being destroyed.

Have I mentioned astronomers like to anthropomorphize things? 

The Universe is a violent place, and nothing is safe from the pull of gravity and the blast of light. Black widows abound, and the stellar variety is amazing in their destruction.

This work appears in the journal Nature and is led by Kevin Burdge.

More Information

MIT press release

A 62-minute orbital period black widow binary in a wide hierarchical triple,” Kevin B. Burdge et al., 2022 May 4, Nature


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