New planet-hunting tool chases after star system's little brown dwarf [View all]

[Judi Lynn]

New planet-hunting tool chases after star system's little brown dwarf

The Sphere instrument on the VLT in Chile peers with all its might into the blackness around a binary star system and returns a surprise for astronomers.

by Michael Franco

@writermfranco
/February 18, 2015 5:30 AM PST

Usually, stories related to the Very Large Telescope array -- a collection of four telescopes built by the European Southern Observatory in Chile -- have to do with astounding things the high-powered lenses have discovered. On Wednesday, the VLT made news for something it failed to spot -- namely, a brown dwarf star that was believed to have been orbiting a binary star system known as V471 Tauri, in the Taurus constellation.

One of the two closely orbiting stars that make up V471 Tauri is a white dwarf and the other is a normal star like our sun, according to a report about the star system on NASA's Chandra X-ray Observatory's website. The binary system is located about 163 light-years from Earth and the distance between the two stars is one-thirtieth the distance between Mercury and the sun, which means they make a full revolution around each other every 12 hours.

When either star passes in front of each other, astronomers can read the changing light signals from the system. A team of led by Adam Hardy of Chile's Universidad Valparaiso measured the changes in brightness down to a very accurate 2 seconds by using the Ultracam system on ESO's New Technology Telescope. The Ultracam is a superfast camera attached to the VLT that can take up to 500 pictures per second in three different colors simultaneously.

The researchers discovered that the eclipses between the two stars didn't happen at a regular interval like they anticipated. To explain the anomaly, astronomers have theorized that there must be a brown dwarf orbiting the system and warping the orbit of the binary stars with its gravitational influence. Brown dwarfs, which are sometimes described as "failed stars," form when a cloud of gas and dust begins to congeal around a central core as in star formation. But in the case of the dwarfs, the material at the core never gets packed in tightly enough to start nuclear fusion and lead to a proper star. So these brown stars float through the galaxy -- not quite stars, not quite planets.


More:
http://www.cnet.com/news/very-large-telescope-fails-to-find-star-systems-little-brown-dwarf/