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Posts Tagged ‘Brown dwarf

First Planet Discovered Orbiting a Brown Dwarf

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Astronomers have long supposed that planets can form around brown dwarfs just as they do around ordinary stars. Now they’ve found the first example

Geometry of the lens system. The closed figures composed concave curves represent the caustic and the line with an arrow is the source trajectory. M1 and M2 represent the binary lens components, where M1 is the heavier one. Greyscale represents the lensing magnification where brighter tone denotes higher magnifications. All lengths are scaled by the Einstein radius corresponding to the total mass of the binary lens

Geometry of the lens system. The closed figures composed concave curves represent the caustic and the line with an arrow is the source trajectory. M1 and M2 represent the binary lens components, where M1 is the heavier one. Greyscale represents the lensing magnification where brighter tone denotes higher magnifications. All lengths are scaled by the Einstein radius corresponding to the total mass of the binary lens (http://arxiv.org/abs/1307.6335)

Astrophysical calculations show that any star that is smaller than about 1/10th of the mass of the sun cannot sustain hydrogen fusion reactions at its core. These failed stars never light up. Instead they wander the galaxy as warm, dark balls of hydrogen known as brown dwarfs.

Brown dwarfs probably form through the same process that lead to ordinary stars but merely on a smaller scale. If that’s correct, planets should also form in the protoplanetary disks of gas and dust around brown dwarfs. Indeed, astronomers have seen a number of protoplanetary disks of this type.

Until now, however, they’ve never seen a planet orbiting a brown dwarf. That’s not really surprising.

The standard methods for detecting planets look for the way a star wobbles as a planet orbits or at how its magnitude changes as a planet passes in front. But given that brown dwarfs are dim and difficult to see, these methods have yet to produce fruit.

All that changes today with the announcement by an international team of astronomers that they’ve discovered a planet orbiting a brown dwarf the first time. These guys have made their discovery using an entirely different method of detection called gravitational lensing. This occurs when one body passes in front of another and its gravity focuses light from the more distant object towards Earth. That works regardless of the brightnesses involved.

The brown dwarf in question is almost 6000 light years from Earth in the Fish Hook constellation. Astronomers first noticed an unusual change in its brightness in April 2012. Further investigation showed that this was indeed a lensing event.

These guys conclude that the brown dwarf is being orbited by a planet about twice the mass of Jupiter at a distance of just under one astronomical unit. The brown dwarf itself is about 10 times larger than its companion.

That’s the first time astronomers have found an object orbiting a brown dwarf that can be truly described as a planet. The technical definition of a planet is that it must have formed in the parent object’s protoplanetary disk.

Astronomers have seen other planet-sized objects orbiting brown dwarfs but only at distances of several tens of astronomical units. That’s too far to have been part of the protoplanetary disk. “Thus,…,they are not bona fide planets,” say the team.

So that’s a modest first for this team. It raises the question of what kind of conditions exist on such a planet and, of course, whether these could support life.

This planet almost certainly does not fall into that category but where there is one planet, there are almost certainly others. Astronomers can now have some fun speculating on the Goldilocks zones around brown dwarfs where conditions are just right for life and how to spot the interesting planets inside them.

Read more at http://www.technologyreview.com/view/517556/

Written by physicsgg

July 29, 2013 at 1:11 pm

Posted in ASTRONOMY, ASTROPHYSICS

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Brown Dwarf Stars Could Host Earth-Size Planets

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Artist’s impression of the disc of dust and gas around a brown dwarf Click to Enlarge This artist’s impression shows the disc of gas and cosmic dust around a brown dwarf. Image released Nov. 30, 2012.CREDIT: ALMA (ESO/NAOJ/NRAO)/M. Kornmesser (ESO

Artist’s impression of the disc of dust and gas around a brown dwarf. This artist’s impression shows the disc of gas and cosmic dust around a brown dwarf. Image released Nov. 30, 2012.
CREDIT: ALMA (ESO/NAOJ/NRAO)/M. Kornmesser (ESO

Observations of a brown dwarf suggest Earth-size planets can form around these “failed” stars, according to new research.

Astronomers found evidence of tiny solid grains in a disk surrounding ISO-Oph 102, a brown dwarf embedded in a star nursery some 400 light-years from Earth.

Current planet-forming theory dictates that rocky worlds form over time as grains orbiting a protostar collide with each other and stick. Scientists previously thought that brown dwarfs have too few dusty particles, moving too quickly, for this process to happen.

We were completely surprised to find millimeter-sized grains in this thin little disk,” Luca Ricci, lead researcher of the study, said in a statement announcing the find. [Brown Dwarfs Make Rocky Planets Too? ]

“Solid grains of that size shouldn’t be able to form in the cold outer regions of a disk around a brown dwarf, but it appears that they do. We can’t be sure if a whole rocky planet could develop there, or already has, but we’re seeing the first steps, so we’re going to have to change our assumptions about conditions required for solids to grow,” added Ricci, an astronomer at the California Institute of Technology…..
Read more: www.space.com


http://youtu.be/JdncxsF4JQY

Written by physicsgg

December 10, 2012 at 11:58 am

Posted in ASTRONOMY, ASTROPHYSICS

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“The Pale Green Dot” -The Coldest Star in the Universe

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Same Temperature as the Human Body


NASA’s Wide-field Infrared Survey Explorer, or WISE, has uncovered the coldest brown dwarf known so far (green dot in very center of this infrared image). Called WISE 1828+2650, located in the constellation Lyra, this chilly star-like body isn’t even as warm as a human body, at less than about 80 degrees Fahrenheit (25 degrees Celsius). The blue dots are a mix of stars and galaxies.
Like other brown dwarfs, it began life like a star, collapsing under its own weight into a dense ball of gas. But, unlike a star, it didn’t have enough mass to fuse atoms at its core, and shine steadily with starlight. Instead, it has continued to cool and fade since its birth, and now gives off only a feeble amount of infrared light.
WISE’s highly sensitive infrared detectors were able to catch the glow of this object during its all-sky scan, which lasted from Jan. 2010 to Feb. 2011. WISE launched Dec. 14, 2009, and mapped the entire sky in 2010 with vastly better sensitivity thanits predecessors. It collected more than 2.7 million images taken at four infrared wavelengths of light, capturing everything from nearby asteroids to distant galaxies.
Since then, the team has been processing more than 15 trillion bytes of returned data. A preliminary release of WISE data,covering the first half of the sky surveyed, was made last April….
Read more: hwww.dailygalaxy.com

Written by physicsgg

March 17, 2012 at 8:10 am

Brown dwarf cooks up a storm

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A team led by astronomers from the University of Toronto have observed noticeable changes in brightness of a nearby brown dwarf, roughly 40 light years away, indicating the presence of a gigantic storm. Since brown dwarfs and giant gaseous planets have similar atmospheres, the team believe that this finding could lead us into understanding more about the weather that rages on the surface of distant worlds.

Astronomers have observed extreme brightness changes on a nearby brown dwarf that may indicate a storm grander than any seen yet on a planet. Image: Art by Jon Lomberg.

Using an infrared camera on the 2.5-metre telescope at Las Campanas Observatory in Chile, the scientists conducted a large survey of nearby brown dwarfs – sub-stellar objects that are too low in mass to sustain hydrogen fusion like main sequence stars – capturing repeated images of brown dwarf 2MASS 2139 over several hours. The team recorded the largest variations in brightness that has ever been witnessed on a cool brown dwarf….. Read the rest of this entry »

Written by physicsgg

September 13, 2011 at 3:56 pm

Posted in ASTRONOMY

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