Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

The locked migration of giant protoplanets

21.03.2006


In an article to be published in Astronomy & Astrophysics, two British astronomers present new numerical simulations of how planetary systems form. They find that, in the early stages of planetary formation, giant protoplanets migrate inward in lockstep into the central star.



The current picture of how planetary systems form is as follows: i) dust grains coagulate to form planetesimals of up to 1 km in diameter; ii) the runaway growth of planetesimals leads to the formation of ~100 – 1000 km-sized planetary embryos; iii) these embryos grow in an “oligarchic” manner, where a few large bodies dominate the formation process, and accrete the surrounding and much smaller planetesimals. These “oligarchs” form terrestrial planets near the central star and planetary cores of ten terrestrial masses in the giant planet region beyond 3 astronomical units (AU).

However, these theories fail to describe the formation of gas giant planets in a satisfactory way. Gravitational interaction between the gaseous protoplanetary disc and the massive planetary cores causes them to move rapidly inward over about 100,000 years in what we call the “migration” of the planet in the disc. The prediction of this rapid inward migration of giant protoplanets is a major problem, since this timescale is much shorter than the time needed for gas to accrete onto the forming giant planet. Theories predict that the giant protoplanets will merge into the central star before planets have time to form. This makes it very difficult to understand how they can form at all.


For the first time, Paul Cresswell and Richard Nelson examined what happens to a cluster of forming planets embedded in a gaseous protoplanetary disc. Previous numerical models have included only one or two planets in a disc. But our own solar system, and over 10% of the known extrasolar planetary systems, are multiple-planet systems. The number of such systems is expected to increase as observational techniques of extrasolar systems improve. Cresswell and Nelson’s work is the first time numerical simulations have included such a large number of protoplanets, thus taking into account the gravitational interaction between the protoplanets and the disc, and among the protoplanets themselves.

The primary motivation for their work is to examine the orbits of protoplanets and whether some planets could survive in the disc for extended periods of time. Their simulations show that, in very few cases (about 2%), a lone protoplanet is ejected far from the central star, thus lengthening its lifetime. But in most cases (98%), many of the protoplanets are trapped into a series of orbital resonances and migrate inward in lockstep, sometimes even merging with the central star. Figure 1 illustrates the migration of a swarm of protoplanets.

Cresswell and Nelson thus claim that gravitational interactions within a swarm of protoplanets embedded in a disc cannot stop the inward migration of the protoplanets. The “problem” of migration remains and requires more investigation, although the astronomers propose several possible solutions. One may be that several generations of planets form and that only the ones that form as the disc dissipates survive the formation process. This may make it harder to form gas giants, as the disc is depleted of the material from which gas giant planets form. (Gas giant formation may still be possible though, if enough gas lies outside the planets’ orbits, since new material may sweep inward to be accreted by the forming planet). Another solution might be related to the physical properties of the protoplanetary disc. In their simulations, the astronomers assumed that the protoplanetary disc is smooth and non-turbulent, but of course this might not be the case. Large parts of the disc could be more turbulent (as a consequence of instabilities caused by magnetic fields), which may prevent inward migration over long time periods.

This work joins other studies of planetary system formation that are currently being done by a European network of scientists. Our view of how planets form has drastically changed in the last few years as the number of newly discovered planetary systems has increased. Understanding the formation of giant planets is currently one of the major challenges for astronomers.

Jennifer Martin | alfa
Further information:
http://www.edpsciences.org/journal/index.cfm?edpsname=aa&niv1=others&niv2=press_release&niv3=PRaa200607

More articles from Physics and Astronomy:

nachricht Further Improvement of Qubit Lifetime for Quantum Computers
09.12.2016 | Forschungszentrum Jülich

nachricht Electron highway inside crystal
09.12.2016 | Julius-Maximilians-Universität Würzburg

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: Electron highway inside crystal

Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their work in the journal Science.

Topological insulators are currently the hot topic in physics according to the newspaper Neue Zürcher Zeitung. Only a few weeks ago, their importance was...

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

Researchers identify potentially druggable mutant p53 proteins that promote cancer growth

09.12.2016 | Life Sciences

Scientists produce a new roadmap for guiding development & conservation in the Amazon

09.12.2016 | Ecology, The Environment and Conservation

Satellites, airport visibility readings shed light on troops' exposure to air pollution

09.12.2016 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>