Newly-discovered pulsar unravels mystery of monster black hole’s strange diet


Astronomers observing the centre of our galaxy have made a new discovery — a type of star they didn't think they'd find in the area, called a magnetized pulsar or 'magnetar' — and this star is helping them to gain new insights into the supermassive black hole that lies at the heart of the Milky Way.

Sagittarius A* — the supermassive black hole that lies at the centre of our galaxy — should be feasting on the abundant of gas and dust in the region around it, but instead it seems to be on some kind of a starvation diet, only consuming a small fraction of what's available. The reason for this has been a mystery.

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Since a black hole's magnetic field has a strong effect on how quickly gas and dust spirals into it — a strong field will make it spiral in fast, but an even stronger field will actually slow it down — knowing the strength of Sagittarius A*'s magnetic field would help scientists solve the mystery. However, until now there was no way to measure the field strength.

"We always knew the magnetic field was important, but we never quite knew how strong to dial it in in our models," theoretical astrophysicist Christopher Reynolds, from the University of Maryland, College Park, who did not take part of the study, told Science.

Having this pulsar in the region of the black hole is great, though, because of the polarized light that pulsars emit. Measuring this light and the degree to which it's polarized can show scientists exactly how strong the magnetic field is. It's fairly weak right near the pulsar — only about 2% of the strength of Earth's magnetic field — but with how far this pulsar is from the black hole, the researchers figured out that the strength of the field close to the black hole is much stronger, and more than enough to account for Sagittarius A*'s strange diet.

The following video doesn't say much, but zooms in on the new discovery, and shows an artist's impression of the pulsar rotating. The periodic tick you hear from the video is the signal of the pulsar as it rotates.

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This new discovery and the results from it are giving us answers about one of the most important objects in our galaxy, but they will likely prove invaluable over the next year, as a huge gas cloud called G2 goes through an encounter with Sagittarius A*. The leading edge of the cloud has already reached the black hole and it will take another year or so before they're finally done with each other.

The European Southern Observatory released a computer simulation video showing the encounter so far and how its expected to proceed from here:

(Image courtesy: MPIfR/Ralph Eatough)

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