Sunday, June 13

Astronomers find a giant flickering star near the heart of the Milky Way | Space


Astronomers have seen a giant flickering star, 100 times larger than the sun, lurking near the heart of the Milky Way.

The telescope observations revealed that over a few hundred days the huge star, which is more than 25,000 light-years away, dimmed by 97% and then slowly returned to its former brightness.

The unexpected and dramatic dimming was likely caused by an orbiting planet or companion star surrounded by a disk of opaque dust that crosses in front and blocks light that would otherwise have reached Earth.

“It seemed to come out of nowhere,” said Dr. Leigh Smith of the University of Cambridge Institute for Astronomy, of the star’s sudden dimming. It began to fade in early 2012 and almost disappeared in April of that year before recovering for the next 100 days.

VVV-WIT-08: sequence of images of the star fading and brightening.
VVV-WIT-08: sequence of images of the star fading and brightening. Photography: ESO

Astronomers noticed the mysterious darkened star in data collected by the Vista telescope, operated by the European Southern Observatory in Chile. The instrument has been observing a billion stars for almost a decade looking for examples that vary in brightness in the infrared range of the electromagnetic spectrum.

When scientists find variable stars that don’t fall into established categories, they call them “what is this” or “WIT” objects. His latest discovery is called VVV-WIT-08.

Because the huge star was in such a dense region of the galaxy, the researchers wondered if an unknown dark object could have strayed in front of it by chance. The simulations suggested that this was highly unlikely without an unlikely number of dark objects floating around the Milky Way.

Animation shows how a huge dust cloud could have caused a giant star to 'blink' - video
Animation shows how a huge dust cloud could have caused a giant star to ‘blink’ – video

Much more likely, the telescope view of VVV-WIT-08 was obscured when a dusty disk around an orbiting planet or a second star got in its way. Astronomers’ calculations, reported in the Monthly Notices from the Royal Astronomical Society, suggested that the disk was tilted to resemble an ellipse of the Earth and had to be gigantic, with a radius of at least a quarter of the distance from Earth to the sun.

It is not the first flickering star astronomers have discovered. A huge disk of dust causes the giant star Epsilon Aurigae to dim by about 50% every 27 years. Another star known as TYC 2505-672-1 is part of a binary system and is dwarfed by the disk around its companion star every 69 years. It’s unclear when VVV-WIT-08 will dim again, but astronomers believe it will happen in the next 20 to 200 years. Two more twinkling stars were observed alongside VVV-WIT-08, but the researchers have fewer details about them.

The flood of discoveries will help astronomers understand what appears to be a new class of “blinking giants” stars. “Once you start accumulating collections of various of these things, you can look at their properties together and unravel the mysteries where these discs come from,” Smith said. “It allows us to learn how these systems evolve and what they do at the end of their lives.”


www.theguardian.com

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