Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Study in Nature sheds new light on planet formation

05.07.2012
A study published in the July 5 edition of the journal Nature is challenging scientists' understanding of planet formation, suggesting that planets might form much faster than previously thought or, alternatively, that stars harboring planets could be far more numerous.

The study—a collaboration between scientists at the University of Georgia; the University of California, San Diego; the University of California, Los Angeles; California State Polytechnic University and the Australian National University—began with a curious and unexpected finding: Within three years, the cloud of dust circling a young star in the Scorpius-Centaurus stellar nursery simply disappeared.

"The most commonly accepted time scale for the removal of this much dust is in the hundreds of thousands of years, sometimes millions," said study co-author Inseok Song, assistant professor of physics and astronomy in the UGA Franklin College of Arts and Sciences. "What we saw was far more rapid and has never been observed or even predicted. It tells us that we have a lot more to learn about planet formation."

Lead author Carl Melis, a postdoctoral fellow at UC San Diego, said, "It's like the classic magician's trick: Now you see it, now you don't. Only in this case we're talking about enough dust to fill an inner solar system, and it really is gone."

The scientists first identified their star of interest by examining data from the Infrared Astronomical Satellite, or IRAS, which surveyed more than 96 percent of the sky in 1983. The star, known as TYC 8241 2652 1, was surrounded by a cloud of dust that was identifiable by its distinctive radiation of infrared energy. Like a skillet absorbing heat and then radiating it, the dust cloud was absorbing energy from the central star and radiating it in the infrared range. This warm dust is thought to be the raw material from which planets form, but scientists don't have a clear understanding of how long the process takes.

The scientists observed the same star in 2008 using a mid-infrared imager at the Gemini South Observatory in Chile and again with the same ground-based telescope in 2009. The 2008 observation revealed an infrared emission pattern similar to the 1983 measurement, but something surprising happened in 2009: The infrared emission dropped by nearly two-thirds. NASA's Wide-field Infrared Survey Explorer, or WISE, looked at the same star again in 2010, and the scientists found that the dust had mostly disappeared. The scientists confirmed their findings using two additional telescopes, the Japanese AKARI telescope and the European Space Agency's Photodetector Array Camera and Spectrometer, or PACS, at the Herschel Space Observatory, and the pattern held.

"It's as if you took a conventional picture of the planet Saturn today and then came back two years later and found that its rings had disappeared," said co-author Ben Zuckerman of UC Los Angeles, who has been investigating circumstellar disks since the 1980s.

The researchers explored several different explanations for how such a large quantity of dust could disappear so rapidly, and each of their explanations challenges conventional thinking about planet formation.

Runaway accretion. The most commonly held theory of planet formation is that minute particles of dust left over after a star forms clump onto each other, first through weak electrostatic interactions and later through gravitational forces. The aggregated dust particles eventually grow to become pebble-sized and then car- to house-sized objects. Ultimately, they become planets. The timescale at which this accretion occurs has been theorized and modeled mathematically, and Song said it is commonly thought to occur over hundreds of thousands of years, a time period that spans civilizations on Earth but is an astronomical blink of an eye.

"If what we observed is related to runaway growth, then our finding suggests that planet formation is very fast and very efficient," Song said. "The implication is that if the conditions are right around a star, planet formation can be nearly instantaneous from astronomical perspective."

The star that the scientists observed is 450 light years away, however, which means any planet formed would not be visible with today's technology.

Song added that a slightly different version of the "runaway accretion" theory suggests that dust grains accrete onto the central star in a very short timescale, implying that the star effectively eliminates planet-building material. If such events occur frequently, planet formation is much less likely than previously thought.

Collisional avalanche. Another explanation for the sudden disappearance of the dust is that it was expelled from the sun's orbit. Song explained that the particles are so small—a hundred times smaller than a grain of sand—that the constant stream of photons emanating from the sun could push them away and into each other, like pinballs, until they leave the suns' orbit.

Because large clouds of dust can be formed when orbiting planets crash into each other, astronomers have often viewed the presence of such clouds as indirect evidence of unseen planets. If clouds of dust are only fleeting, however, then many more stars than previously thought could harbor planets.

"People often calculate the percentage of stars that have a large amount of dust to get a reasonable estimate of the percentage of stars with planetary systems, but if the dust avalanche model is correct, we cannot do that anymore," Song said. "Many stars without any detectable dust may have mature planetary systems that are simply undetectable."

Next steps. Like many important discoveries, the scientists' finding raises more questions than it answers. Song said his colleagues now aim to compare measurements from 1983 with data from modern telescopes to systematically search for other stars that have rapidly depleted—or replenished—their dust clouds. The goal is to understand the frequency with which these processes occur and, ultimately, to advance understanding of how planets form.

"Many astronomers may feel uncomfortable with the suggested explanations for the disappearance of the dust because each of them has non-traditional implications," Song said, "but my hope that this line of research can bring us closer to a true understanding of how planets form."

Additional authors include Joseph Rhee of California State Polytechnic University and Simon Murphy and Michael Bessell of the Australian National University.

The study was supported by the Lawrence Livermore National Laboratory, the National Science Foundation and NASA.

Inseok Song | EurekAlert!
Further information:
http://www.uga.edu

More articles from Studies and Analyses:

nachricht The importance of biodiversity in forests could increase due to climate change
17.11.2017 | Deutsches Zentrum für integrative Biodiversitätsforschung (iDiv) Halle-Jena-Leipzig

nachricht Win-win strategies for climate and food security
02.10.2017 | International Institute for Applied Systems Analysis (IIASA)

All articles from Studies and Analyses >>>

The most recent press releases about innovation >>>

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

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

Im Focus: Wrinkles give heat a jolt in pillared graphene

Rice University researchers test 3-D carbon nanostructures' thermal transport abilities

Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

NASA detects solar flare pulses at Sun and Earth

17.11.2017 | Physics and Astronomy

NIST scientists discover how to switch liver cancer cell growth from 2-D to 3-D structures

17.11.2017 | Health and Medicine

The importance of biodiversity in forests could increase due to climate change

17.11.2017 | Studies and Analyses

VideoLinks
B2B-VideoLinks
More VideoLinks >>>