Space

July 26, 2013

NASA’s WISE finds mysterious centaurs may be Comets

The true identity of centaurs, the small celestial bodies orbiting the sun between Jupiter and Neptune, is one of the enduring mysteries of astrophysics.

Are they asteroids or comets? A new study of observations from NASA’s Wide-field Infrared Survey Explorer finds most centaurs are comets.

Until now, astronomers were not certain whether centaurs are asteroids flung out from the inner solar system or comets traveling in toward the sun from afar. Because of their dual nature, they take their name from the creature in Greek mythology whose head and torso are human and legs are those of a horse.

“Just like the mythical creatures, the centaur objects seem to have a double life,” said James Bauer of NASA’s Jet Propulsion Laboratory in Pasadena, Calif. Bauer is lead author of a paper published online July 22 in the Astrophysical Journal. “Our data point to a cometary origin for most of the objects, suggesting they are coming from deeper out in the solar system.”

Cometary origin means an object likely is made from the same material as a comet, may have been an active comet in the past, and may be active again in the future.

The findings come from the largest infrared survey to date of centaurs and their more distant cousins, called scattered disk objects. NEOWISE, the asteroid-hunting portion of the WISE mission, gathered infrared images of 52 centaurs and scattered disk objects. Fifteen of the 52 are new discoveries. Centaurs and scattered disk objects orbit in an unstable belt. Ultimately, gravity from the giant planets will fling them either closer to the sun or farther away from their current locations.

Although astronomers previously observed some centaurs with dusty halos, a common feature of outgassing comets, and NASA’s Spitzer Space Telescope also found some evidence for comets in the group, they had not been able to estimate the numbers of comets and asteroids.

Infrared data from NEOWISE provided information on the objects’ albedos, or reflectivity, to help astronomers sort the population. NEOWISE can tell whether a centaur has a matte and dark surface or a shiny one that reflects more light. The puzzle pieces fell into place when astronomers combined the albedo information with what was already known about the colors of the objects. Visible-light observations have shown centaurs generally to be either blue-gray or reddish in hue. A blue-gray object could be an asteroid or comet. NEOWISE showed that most of the blue-gray objects are dark, a telltale sign of comets. A reddish object is more likely to be an asteroid.

“Comets have a dark, soot-like coating on their icy surfaces, making them darker than most asteroids,” said the study’s co-author, Tommy Grav of the Planetary Science Institute in Tucson, Ariz. “Comet surfaces tend to be more like charcoal, while asteroids are usually shinier like the moon.”

The results indicate that roughly two-thirds of the centaur population is comets which came from the frigid outer reaches of our solar system. It is not clear whether the rest are asteroids. The centaur bodies have not lost their mystique entirely, but future research from NEOWISE may reveal their secrets further.

The paper is available online at:  http://iopscience.iop.org/0004-637X/773/1/22/

JPL, managed by the California Institute of Technology in Pasadena, managed and operated WISE for NASA’s Science Mission Directorate. The NEOWISE portion of the project was funded by NASA’s Near Earth Object Observation Program. WISE completed its key mission objective, two scans of the entire sky, in 2011 and has been hibernating in space since then.

 




All of this week's top headlines to your email every Friday.


 
 

 

Headlines July 30, 2014

News: Software to power F-35 running as much as 14 months late - Software needed to operate Lockheed Martin’s F-35 jet, the Pentagon’s costliest weapons system, may be as much as 14 months late for required flight testing, according to a Pentagon review.   Business: Lockheed will turn on JLTV production line In August; 6-D truck...
 
 

News Briefs July 30, 2014

U.S. military deaths in Afghanistan at 2,197 As of July 29, 2014, at least 2,197 members of the U.S. military had died in Afghanistan as a result of the U.S.-led invasion of Afghanistan in late 2001, according to an Associated Press count. At least 1,819 military service members have died in Afghanistan as a result...
 
 
Lockheed Martin photograph by Tom Reynolds

F-35B successfully completes wet runway, crosswind testing

Lockheed Martin photograph by Tom Reynolds F-35B aircraft BF-4, piloted by Lockheed Martin Test Pilot Dan Levin, starts down the runway as part of wet runway and crosswind testing at Edwards AFB, Calif. In an important program ...
 

 
boeing-chinook

Boeing delivers first U.S. Army multiyear II configured Chinook

Boeing July 29 delivered the first multiyear II configured CH-47F Chinook helicopter to the U.S. Army one month ahead of schedule. The delivery was celebrated in a ceremony at the production facility in Ridley Township, Penn. ...
 
 
Army photograph by SSgt. Angela Stafford

Engineers developing safer, more accurate tracer round

Army photograph Tracer rounds enable the shooter to follow the projectile trajectory to make aiming corrections. However, the light emitted by these rounds also gives away the position of the shooter. Engineers at Picatinny Ars...
 
 
NASA photograph by Carla Thomas

Katherine Lott awarded NASA Armstrong employee scholarship

NASA photograph by Carla Thomas Katherine Lott, the recipient of the 2014 NASA Armstrong Employee Exchange Council Joseph R. Vensel Memorial Scholarship, is congratulated by NASA Armstrong center director David McBride. Flankin...
 




0 Comments


Be the first to comment!


Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>