Tag Archives: light echo

Echoes From an Exploding Star

*Astronomers watch a delayed broadcast of a powerful stellar eruption.*

Astronomers are watching the astronomical equivalent of streaming live video of a spectacular outburst from the unstable, behemoth double-star system Eta Carinae, which initially was seen on Earth nearly 170 years ago.

Dubbed the “Great Eruption,” the outburst lasted from 1837 to 1858 and caught the attention of sky-watchers at the time, including the British astronomer Sir John Herschel. He did not have the benefit of the imaging cameras and spectrographs that modern astronomers use to learn about stars, so we only have a historical record of the star’s visual brightness. (more…)

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Cosmic Curiosity Reveals Ghostly Glow of Dead Quasar

The green Voorwerp in the foreground remains illuminated by light emitted up to 70,000 years ago by a quasar in the center of the background galaxy, which has since died out. Image credit: WIYN/William Keel/Anna Manning

While sorting through hundreds of galaxy images as part of the Galaxy Zoo citizen science project two years ago, Dutch schoolteacher and volunteer astronomer Hanny van Arkel stumbled upon a strange-looking object that baffled professional astronomers. Two years later, a team led by Yale University researchers has discovered that the unique object represents a snapshot in time that reveals surprising clues about the life cycle of black holes.

In a new study, the team has confirmed that the unusual object, known as Hanny’s Voorwerp (Hanny’s “object” in Dutch), is a large cloud of glowing gas illuminated by the light from a quasar-an extremely energetic galaxy with a supermassive black hole at its center. The twist, described online in the Astrophysical Journal Letters, is that the quasar lighting up the gas has since burned out almost entirely, even though the light it emitted in the past continues to travel through space, illuminating the gas cloud and producing a sort of “light echo” of the dead quasar. (more…)

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