Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Two new dusty planetary disks may be astrophysical mirrors of our Kuiper Belt

23.01.2006


Narrow debris belts, like Kuiper Belt, may herald shepherding companion star


These two bright debris disks of ice and dust appear to be the equivalent of our own solar system’s Kuiper Belt.



A survey by NASA’s Hubble Space Telescope of 22 nearby stars has turned up two with bright debris disks that appear to be the equivalent of our own solar system’s Kuiper Belt, a ring of icy rocks outside the orbit of Neptune and the source of short-period comets.

The debris disks encircling these stars fall into two categories - wide and narrow belts - that appear to describe all nine stars, including the sun, which are known to have debris disks linked to planet formation. In fact, the sharp outer edges of the narrow belts, such as the Kuiper Belt in our solar system, may be a tip-off to the existence of a star-like companion that continually grooms the edge, in the same way that shepherding moons trim the edges of debris rings around Saturn and Uranus.


Research astronomer Paul Kalas, professor of astronomy James Graham and graduate student Michael Fitzgerald of the University of California, Berkeley, along with Mark C. Clampin of Goddard Space Flight Center in Greenbelt, Md., will report their discovery and conclusions in the Jan. 20 issue of Astrophysical Journal Letters.

The newfound stellar disks, each about 60 light years from Earth, bring to nine the number of stars with dusty debris disks observable at visible wavelengths. The new ones are different, however, in that they are old enough - more than 300 million years - to have settled into stable configurations akin to the stable planet and debris orbits in our own solar system, which is 4.6 billion years old. The other seven, except for the sun, range from tens of millions to 200 million years old - young by solar standards.

In addition, the masses of the stars are closer to that of the sun.

"These are the oldest debris disks seen in reflected light, and are important because they show what the Kuiper Belt might look like from the outside," said Kalas, the lead researcher. "These are the types of stars around which you would expect to find habitable zones and planets that could develop life."

Most debris disks are lost in the glare of the central star, but the high resolution and sensitivity of the Hubble Space Telescope’s Advanced Camera for Surveys has made it possible to look for these disks after blocking the light from the star. Kalas has discovered debris disks around two other stars (AU Microscopii and Fomalhaut) in the past two years, one of them with the Hubble telescope, and has studied details of most of the other known stars with disks.

"We know of 100-plus stars that have infrared emission in excess of that emitted from the star, and that excess thermal emission comes from circumstellar dust," Kalas said. "The hard part is obtaining resolved images that give spatial information. Now, two decades after they were first discovered, we are finally beginning to see the dust disks. These recent detections are really a tribute to all the hard work that went into upgrading Hubble’s instruments during the last servicing mission."

The small sampling already shows that such disks fall into two categories: those with a broad belt, wider than about 50 astronomical units; and narrow ones with a width of between 20 and 30 AU and a sharp outer boundary, probably like our own Kuiper Belt. An astronomical unit, or AU, is the average distance between the Earth and sun, about 93 million miles. Our Kuiper Belt is thought to be narrow, extending from the orbit of Neptune at 30 AU to about 50 AU.

Most of the known debris disks seem to have a central area cleared of debris, perhaps by planets, which are likely responsible for the sharp inner edges of many of these belts.

Kalas and Graham speculate that stars also having sharp outer edges to their debris disks have a companion - a star or brown dwarf, perhaps - that keeps the disk from spreading outward, similar to the way that Saturn’s moons shape the edges of many of the planet’s rings.

"The story of how you make a ring around a planet could be the same as the story of making rings around a star," Kalas said. Only one of the nine stars is known to have a companion, but then, he said, no one has yet looked at most of these stars to see if they have faint companions at large distances from the primary star.

He suggests that a stray star passing by may have ripped off the edges of the original planetary disk, but a star-sized companion would be necessary to keep the remaining disk material, such as asteroids, comets and dust, from spreading outward.

If true, that would mean that the sun also has a companion keeping the Kuiper Belt confined within a sharp boundary. Though a companion star has been proposed before - most recently by UC Berkeley physics professor Richard Muller, who dubbed the companion Nemesis - no evidence has been found for such a companion.

A key uncertainty, Kalas said, is that while we can see many of the large planetesimals in our Kuiper Belt, we can barely detect the dust.

"Ironically, our own debris disk is the closest, yet we know the least about it," he said. "We would really like to know if dust in our Kuiper Belt extends significantly beyond the 50 AU edge of the larger objects. When we acquire this information, only then will we be able to place our sun correctly in the wide or narrow disk categories."

The star survey by Kalas, Graham, Fitzgerald and Clampin was one of the first projects of the Advanced Camera for Surveys aboard the Hubble, which was installed in 2002. The 22 stars were observed over a two year period ending in September 2004. The stars with debris disks detectable in visible light were HD 53143, a K star slightly smaller than the sun but about 1 billion years old, and HD 139664, an F star slightly larger than the sun but only 300 million years old.

"One is a K star and the other is an F star, therefore they are more likely to form planetary systems with life than the massive and short-lived stars such as beta-Pictoris and Fomalhaut," he noted. "When we look at HD 53143 and HD 139664, we may be looking at astrophysical mirrors to our Kuiper Belt."

The disk around the oldest of the two stars, HD 53143, is wide like that of beta-Pictoris (beta-Pic), which was the first debris disk ever observed, about 20 years ago, and AU Microscopii (AU Mic), which Kalas discovered last year. Both beta-Pic and AU Mic are about 10 million years old.

The disk around HD 139664, however, is a narrow belt, similar to the disk around the star Fomalhaut, which Kalas imaged for the first time early last year. HD 139664 has a very sharp outer edge at 109 AU, similar to the sharp outer edge of our Kuiper Belt at 50 AU. The belt around HD 139664 starts about 60 AU from the star and peaks in density at 83 AU.

"If we can understand the origin of the sharp outer edge around HD 139664, we might better understand the history of our solar system," Kalas said.

Robert Sanders | EurekAlert!
Further information:
http://www.berkeley.edu

More articles from Physics and Astronomy:

nachricht DGIST develops 20 times faster biosensor
24.04.2017 | DGIST (Daegu Gyeongbuk Institute of Science and Technology)

nachricht New quantum liquid crystals may play role in future of computers
21.04.2017 | California Institute of Technology

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: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

Early organic carbon got deep burial in mantle

25.04.2017 | Earth Sciences

A room with a view - or how cultural differences matter in room size perception

25.04.2017 | Life Sciences

Warm winds: New insight into what weakens Antarctic ice shelves

25.04.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>