![]() ![]() ![]() The reported X-ray flare prompted Fiona Harrison, an astronomer who leads NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR) satellite, to train the X-ray space telescope on Sgr A*. Yet the focus on the Galactic Centre has paid off unexpectedly. ![]() “I’m just worried that this is overblown,” she says. ![]() The result would be a Galactic fizzle rather than fireworks. If she is right, Sgr A* may swallow some of the gas, but the star itself would have enough momentum to escape the black hole’s grasp. Andrea Ghez, an astronomer studying G2 at the University of California, Los Angeles, says that her infrared observations at the Keck telescopes on Mauna Kea in Hawaii suggest that G2 may not be a gas cloud, but rather a star surrounded by gas. The observing frenzy is likely to jeopardize regularly scheduled observations, and some astronomers worry that the pay-off may be disappointing. “I don’t think there was ever such a large camp of telescopes looking at the Galactic Centre,” says Stefan Gillessen, an astronomer at the Max Planck Institute for Extraterrestrial Physics in Garching, Germany, who last year reported that G2 was on course for Sgr A* ( S. Gillessen et al. The VLA, for example, is already scanning radio frequencies around Sgr A* every two months, and will do so every month once G2 arrives. Many telescope directors are scheduling additional monitoring of the Galactic Centre. Its arrival would deliver insight into how objects accrete into the swirling disk of material around a black hole, as well as offering the first chance for astronomers to measure the time that it takes for objects to be captured and swallowed up.Įvery flicker of emissions from Sgr A* sparks a flurry of speculation, intensifying the usual cycle of observation and coordinated follow-up that characterizes high-energy astronomy. The cloud, which is about three times the mass of Earth, was first spotted near Sgr A* in 2012 (and was later found in 2002 data). The magnetar’s accidental discovery is a by-product of astronomers’ excitement about the arrival of the gas cloud, dubbed G2. “There’s huge interest in finding pulsars around supermassive black holes, and this is the first example,” says Geoffrey Bower, a radioastronomer at the University of California, Berkeley, who carried out the recent VLA observations. The magnetar’s regular radio pulses could be used to measure the warping of space-time near the monster black hole and to test predictions of Einstein’s general theory of relativity. Its position near Sgr A* makes it a precious find. If the flare wasn’t the arrival of the gas cloud, what was it?Īn answer soon came from other telescopes watching the drama at the centre of the Galaxy: the flare was coming from a magnetar, a highly magnetized kind of pulsar, or rotating neutron star. Within hours of seeing the report, he had trained the VLA’s radio dishes on the scene, only to find nothing remarkable. But Frail did not want to risk missing the action. The cloud’s death was not expected until between September this year and March 2014. Astronomers were speculating that the flare might be a sign that a gas cloud they had been tracking had begun its death spiral into the black hole.įrail was sceptical. Frail, who is in charge of the Very Large Array (VLA) of radio telescopes near Socorro in New Mexico, had seen a report last month about a long-lived X-ray flare emanating from the centre of the Milky Way, home to a supermassive black hole called Sagittarius A* (Sgr A*). Dale Frail couldn’t resist the prospect of watching a black hole swallow its prey. ![]()
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