Here’s what really happened to Hanny’s Voorwerp | Science News

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Mystery Solved

Here’s what really happened to Hanny’s Voorwerp

Astronomers can finally explain a gas cloud’s strange glow

By
3:30pm, November 27, 2017
Hanny’s Voorwerp

GLOWING GAS  Hanny’s Voorwerp, the greenish smudge at the left of this image, is glowing thanks to photons from a feasting black hole in the galaxy at right.

The weird glowing blob of gas known as Hanny’s Voorwerp was a 10-year-old mystery. Now, Lia Sartori of ETH Zurich and colleagues have come to a two-pronged solution.

Hanny van Arkel, then a teacher in the Netherlands, discovered the strange bluish-green voorwerp, Dutch for “object,” in 2008 as she was categorizing pictures of galaxies as part of the Galaxy Zoo citizen science project.

Further observations showed that the voorwerp was a glowing cloud of gas that stretched some 100,000 light-years from the core of a massive nearby galaxy called IC 2497. The glow came from radiation emitted by an actively feeding black hole in the galaxy.

To excite the voorwerp’s glow, the black hole and its surrounding accretion disk, the active galactic nucleus, or AGN, should have had the brightness of about 2.5 trillion suns;

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