Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Astronomers’ first direct evidence: young low-mass objects are twice as heavy as predicted

20.01.2005


Although mass is the most important property of stars, it has proved very hard to measure for the lowest mass objects in the universe. Thanks to a powerful new camera, a very rare, low-mass companion has finally been photographed.



The discovery suggests that, due to errors in the models, astronomers have overestimated the number of young "brown dwarfs" and "free floating" extrasolar planets. An international team of astronomers lead by University of Arizona Associate Professor Laird Close reports the discovery in today’s (Jan 20.) issue of Nature.

The image has allowed the team to directly measure the mass of a young, very low mass object for the first time. The object, more than 100 times fainter than its close primary star, is 93 times as massive as Jupiter -- almost twice as heavy as theory predicts it should be. Their findings challenge current ideas about the astronomical brown dwarf population and the existence of widely publicized free-floating extrasolar planets.


Brown dwarfs are objects 75 times more massive than Jupiter but not massive enough to burn as stars. If young objects identified as brown dwarfs are twice as massive as has been thought, many actually are low mass stars. Objects recently identified as ’free-floating’ planets are in turn likely just low mass brown dwarfs.

Close of the UA’s Steward Observatory and his international colleagues detected the faint, very-low-mass companion, named AB Dor C, which orbits the very young star AB Doradus A (AB Dor A) at only 2.3 times the distance between the Earth and the sun, or about the distance between the sun and the asteroids beyond Mars.

Astronomers searching for very low mass objects look at young nearby stars because low mass companion objects will be brightest when young, before they contract and cool. Astronomers had suspected since the early 1990s that well-known AB Dor A -- a star 48 light years (14.9 parsecs) from Earth and only 50 million years old -- has a low-mass companion because its position ’wobbles’ as it’s pulled by an unseen companion. But even the Hubble Space Telescope tried and failed to detect the companion because it was too faint and too close to the glare of the primary star.

Close and his colleagues from Germany (Rainer Lenzen, Wolfgang Brandner), Spain (Jose C. Guirado), Chile (Markus Hartung, Chris Lidman), and the United States (Eric Nielsen, Eric Mamajek, and Beth Biller) succeeded in photographing the elusive companion. They used Close and Lenzen’s novel high-contrast camera on the European Southern Observatory’s 8.2-meter Very Large Telescope in Chile in February 2004.

Close and Lenzen developed the new high-contrast adaptive optics camera, the NACO Simultaneous Differential Imager, or NACO SDI, for hunting extrasolar planets. The SDI camera enhances the ability of the powerful 8.2-meter VLT telescope and its existing adaptive optics system to detect faint companions that normally would be lost in the glare of the primary star.

Close and his team are the first to image a companion so faint – 120 times fainter than its star -- and so near its star. The tiny distance between the star and the faint companion (0.156 arcseconds) is the same as the width of a dime (1.5 centimeters) seen 8 miles (13 kilometers) away. Once they located the companion, they observed it at near infrared wavelengths to measure its temperature and luminosity.

"We were surprised to find that the companion was 400 degrees Celsius cooler and 2.5 times fainter than the latest models predicted," Close said.

"We used our discovery of the companion’s exact location, along with the star’s known ’wobble’, to accurately determine the companion’s mass," team member Jose Guirado said.

"Theory predicts that this low-mass, cool object would be about 50 Jupiter masses," Close said. "But theory is incorrect: This object is between 88-98 Jupiter masses. This discovery will force astronomers to rethink what masses of the smallest objects produced in nature really are."

"Objects like AB Dor C are very rare," Wolfgang Brandner said. "Only one percent of stars have close very low mass companions -- and only about one percent of nearby stars are young. Hence, we are very lucky to be able to accurately measure the mass of even a single low mass companion that is accurately known to be young."

The NACO SDI camera is a unique type of camera using adaptive optics, which removes the blurring effects of Earth’s atmosphere to produce extremely shape images. SDI splits light from a single star into four identical images, then passes the resulting beams through four slightly different methane-sensitive filters. When the filtered light beams hit the camera’s detector array, astronomers can subtract the images so the bright star disappears, revealing a fainter, lower-mass methane-rich object otherwise hidden in the star’s scattered light halo.

The National Science Foundation awarded Close a prestigious 5-year, $545,000 Faculty Early Career Development award that supports his search for extrasolar planets using SDI cameras on the European Southern Observatory’s 8.2-meter VLT in Chile and on the UA/Smithsonian 6.5-meter MMT on Mount Hopkins, Ariz. This research was also supported by NASA.

Authors of the Jan. 20 Nature letter, "A dynamical calibration of the mass-luminosity relation at very low stellar masses and young ages," are: Laird Close of the UA Steward Observatory, Rainer Lenzen of the Max Planck Institute for Astronomy in Heidelberg, Jose C. Guirado of the University of Valencia (Spain), Eric L. Nielsen of UA Steward Observatory, Eric E. Mamajek of the Harvard-Smithsonian Center for Astrophysics, Wolfgang Brandner of the Max Planck Institute for Astronomy in Heidelberg, Markus Hartung and Chris Lindman of the European Southern Observatory (Chile), and Beth Biller of the UA Steward Observatory.

Laird M. Close | EurekAlert!
Further information:
http://www.arizona.edu

More articles from Physics and Astronomy:

nachricht Light-emitting bubbles captured in the wild
28.02.2017 | Georg-August-Universität Göttingen

nachricht Scientists reach back in time to discover some of the most power-packed galaxies
28.02.2017 | Clemson University

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Safe glide at total engine failure with ELA-inside

On January 15, 2009, Chesley B. Sullenberger was celebrated world-wide: after the two engines had failed due to bird strike, he and his flight crew succeeded after a glide flight with an Airbus A320 in ditching on the Hudson River. All 155 people on board were saved.

On January 15, 2009, Chesley B. Sullenberger was celebrated world-wide: after the two engines had failed due to bird strike, he and his flight crew succeeded...

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

New technology offers fast peptide synthesis

28.02.2017 | Life Sciences

WSU research advances energy savings for oil, gas industries

28.02.2017 | Power and Electrical Engineering

Who can find the fish that makes the best sound?

28.02.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>