Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Astronomers discover most Earth-like extrasolar planet yet

14.06.2005


The world’s preeminent planet hunters have discovered the most Earth-like extrasolar planet yet: a possibly rocky world about 7.5 times as massive as the Earth.



This hot "super-Earth," just 15 light years away, travels in a nearly circular orbit only 2 million miles from its parent star, Gliese 876, and has a radius about twice that of Earth. All the nearly 150 extrasolar planets discovered to date that are orbiting normal stars have been larger than Uranus, an ice giant about 15 times the mass of Earth. "This is the smallest extrasolar planet yet detected and the first of a new class of rocky terrestrial planets," said team member Paul Butler of the Carnegie Institution in Washington. "It’s like Earth’s bigger cousin."

"This planet answers an ancient question," said team leader Geoffrey Marcy, professor of astronomy at the University of California, Berkeley. "Over 2,000 years ago, the Greek philosophers Aristotle and Epicurus argued about whether there were other Earth-like planets. Now, for the first time, we have evidence for a rocky planet around a normal star."


Marcy, Butler, theoretical astronomer Jack Lissauer of NASA/Ames Research Center, and post-doctoral researcher Eugenio J. Rivera of the University of California Observatories/Lick Observatory at UC Santa Cruz presented their findings today (Monday, June 13) during a press conference at the National Science Foundation (NSF) in Arlington, Va.

Part of a system that includes two other Jupiter-size planets, the new rocky planet whips around its star in a mere two days, and is so close to the star’s surface that the astronomers say its temperature probably tops 200 to 400 degrees Celsius (400 to 750 degrees Fahrenheit) - oven temperatures far too hot for life as we know it. Nevertheless, the ability to detect the tiny wobble that the planet induces in the star gives them confidence that they will be able to discover even smaller rocky planets in orbits more hospitable to life.

The team measures a minimum mass of 5.9 Earth masses for the new planet, which is orbiting Gliese 876 with a period of 1.94 days at a distance of 0.021 astronomical units (AU), or 2 million miles. Though the team has no proof that the planet is rocky, its low mass precludes it from retaining gas like Jupiter. Three other purportedly rocky extrasolar planets have been reported, but they orbit a pulsar, the flashing corpse of an exploded star.

Gliese 876 (or GJ 876) is a small, red star known as an M dwarf – the most common type of star in the galaxy. It is located in the constellation Aquarius, and, at about one-third the mass of the sun, is the smallest star around which planets have been discovered. Butler and Marcy detected the first planet in 1998, and it proved to be a gas giant about twice the mass of Jupiter. Then, in 2001, they reported a second planet, another gas giant about half the mass of Jupiter. The two are in resonant orbits, the outer planet taking 60 days to orbit the star, twice the period of the inner giant planet.

Data on the Gliese 876 system, gathered from research the astronomers conducted at the Keck Observatory in Hawaii, were analyzed by Lissauer and Rivera in order to model the unusual motions of the two known planets. Three years ago, they got an inkling that there might be a smaller, third planet orbiting the star. In fact, if they hadn’t taken account of the resonant interaction between the two known planets, they never would have seen the third. "We had a model for the two planets interacting with one another, but when we looked at the difference between the two-planet model and the actual data, we found a signature that could be interpreted as a third planet," Lissauer said.

A three-planet model consistently gave a better fit to the data, added Rivera. "But because the signal from this third planet was not very strong, we were very cautious about announcing a new planet until we had more data," he said.

Recent improvements to the Keck Telescope’s high-resolution spectrometer (HIRES) provided the crucial new data. Vogt, who designed and built HIRES, worked with the technical staff in the UC Observatories/Lick Observatory Laboratories at UC Santa Cruz to upgrade the spectrometer’s CCD (charge coupled device) detectors last August. "It is the higher precision data from the upgraded HIRES that gives us confidence in this result," Butler said.

The team now has convincing data for the planet orbiting very close to the star, at a distance of about 10 stellar radii. That’s less than one-tenth the size of Mercury’s orbit in our solar system. "In a two-day orbit, it’s about 200 degrees Celsius too hot for liquid water," Butler said. "That tends to lead us to the conclusion that the most probable composition of this thing is like the inner planets of this solar system - a nickel/iron rock, a rocky planet, a terrestrial planet."

"The planet’s mass could easily hold onto an atmosphere," noted Laughlin, an assistant professor of astronomy at UC Santa Cruz. "It would still be considered a rocky planet, probably with an iron core and a silicon mantle. It could even have a dense steamy water layer. I think what we are seeing here is something that’s intermediate between a true terrestrial planet like the Earth and a hot version of the ice giants Uranus and Neptune."

A paper detailing the team’s results has been submitted to The Astrophysical Journal. Coauthors on the paper are Steven Vogt and Gregory Laughlin of the Lick Observatory at the University of California, Santa Cruz; Debra Fischer of San Francisco State University; and Timothy M. Brown of NSF’s National Center for Atmospheric Research in Boulder, Colo.

Combined with improved computer software, the new CCD detectors designed by this team for Keck’s HIRES spectrometer can now measure the Doppler velocity of a star to within one meter per second - human walking speed - instead of the previous precision of 3 meters per second. This improved sensitivity will allow the planet-hunting team to detect the gravitational effect of an Earth-like planet within the habitable zone of M dwarf stars like Gliese 876. "We are pushing a whole new regime at Keck to achieve one meter per second precision, triple our old precision, that should also allow us to see Earth-mass planets around sun-like stars within the next few years," Butler said. "Our UC Santa Cruz and Lick Observatory team has done an enormous amount of optical and technical and detector work to make the Keck telescope a rocky planet hunter, the best one in the world," Marcy added.

Lissauer also is excited by another feat reported in the paper submitted to The Astrophysical Journal. For the first time, he, Rivera and Laughlin have determined the line-of-sight inclination of the orbit of the stellar system solely from the observed Doppler wobble of the star. Using dynamical models of how the two Jupiter-size planets interact, they were able to calculate the masses of the two giant planets from the observed shapes and precession rates of their oval orbits. Precession is the slow turning of the long axis of a planet’s elliptical orbit.

They showed that the orbital plane is tilted 40 degrees to our line of sight. This allowed the team to estimate the most likely mass of the third planet as 7.5 Earth masses. "There’s more dynamical modeling involved in this study than any previous study, much more," Lissauer said.

The team plans to continue to observe the star Gliese 876, but is eager to find other terrestrial planets among the 150 or more M dwarf planets they observe regularly with Keck. "So far, we find almost no Jupiter mass planets among the M dwarf stars we’ve been observing, which suggests that, instead, there is going to be a large population of smaller mass planets," Butler noted.

The astronomers’ research was supported by NSF, the National Aeronautics and Space Administration, the University of California and the Carnegie Institution of Washington.

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

More articles from Physics and Astronomy:

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

nachricht Light rays from a supernova bent by the curvature of space-time around a galaxy
21.04.2017 | Stockholm 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: 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

Molecular libraries for organic light-emitting diodes

24.04.2017 | Life Sciences

Research sheds new light on forces that threaten sensitive coastlines

24.04.2017 | Earth Sciences

Making lightweight construction suitable for series production

24.04.2017 | Machine Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>