A second system is likely to have a belt of rocky bodies the size of Mars or smaller. The other two, the models show, do not have the proper conditions to form an Earth-size planet. Each system lies within 250 light years of Earth (a light year is about 5.88 trillion miles). Astronomers already have found evidence that each system contains at least two giant planets about the mass of Jupiter, which have migrated close to their stars, perhaps as close as Mercury is to the sun.
For each of the four systems, the researchers conducted 10 computerized simulations that placed small planet embryos, or protoplanets, in the system to see if they are able to gather more material and form a true planet the size of Earth. Each simulation assumed the same conditions in the planetary system except that the position and mass of each protoplanet was altered slightly, said Sean Raymond, a postdoctoral researcher at the University of Colorado, who took part in the work while he was an astronomy doctoral student at the University of Washington.
Raymond is lead author of a paper describing the research published in June in the Astrophysical Journal. Co-authors are Rory Barnes, a postdoctoral researcher at the University of Arizona who also took part in the work while a UW astronomy doctoral student, and Nathan Kaib, a UW doctoral student in astronomy. The work was funded by the National Aeronautics and Space Administration, NASA's Astrobiology Institute and the National Science Foundation.
"It's exciting that our models show a habitable planet, a planet with mass, temperature and water content similar to Earth's, could have formed in one of the first extrasolar multi-planet systems detected," Barnes said.
Recent studies show many known extrasolar planetary systems have regions stable enough to support planets ranging from the mass of Earth to that of Saturn. The UW models tested planet formation in systems called 55 Cancri, HD 38529, HD 37124 and HD 74156. The researchers assumed the systems are complete and the orbits of their giant planets are well established. They also assumed conditions that might allow formation of small bodies that could develop into rocky, Earth-like planets.
In the models, the scientists placed moon-sized planet embryos between giant planets and allowed them to evolve for 100 million years. With those assumptions, they found terrestrial planets formed readily in 55 Cancri, sometimes with substantial water and orbits in the system's habitable zone. They found HD 38529 is likely to support an asteroid belt and Mars-sized or smaller bodies but no notable terrestrial planets. No planets formed in HD 37124 and HD 74156.
"What surprised me the most was to see the system that only formed planets the size of Mars or smaller," Raymond said. "Anything that grew too big would be unstable, so there was an accumulation of a lot of smaller protoplanets maybe one-tenth the size of Earth."
It was significant, Kaib said, that the models showed conditions could remain stable enough for 100 million years so that a planetary embryo would have a chance to gather more substance and develop into a body the size of the moon or Mars. "In our early system, that's probably what our inner solar system looked like, with hundreds of bodies that size," he said.
Extrasolar planets have been discovered with increasing frequency in recent years because of techniques that detect giant planets by their gravitational effect on their parent stars. It is uncertain how the giant planets evolve, but they are thought to form far away from their host stars and then migrate inward, pushed by the gas discs from which they formed. If the migration occurs late in the system's development, the giant planets might destroy most of the materials needed to build Earth-like planets, Raymond said. He noted that while the presence of giant planets is fairly well established, it will be some time before it is possible to detect much smaller Earth-sized planets around other stars.
For another recent paper, Raymond ran more than 450 computer simulations to map giant planet orbits that allow Earth-like planets to form. If a giant planet is too close it will prevent rocky material from amassing into an Earth-sized planet. That study showed that only about 5 percent of the known giant-planet systems are likely to have Earth-like planets. But because of long observation times and sensitive equipment needed to detect planets the size of Saturn and Jupiter, it is possible there could be many planetary systems such as ours in this galaxy, he said.
Vince Stricherz | EurekAlert!
Astronomers find unexpected, dust-obscured star formation in distant galaxy
24.03.2017 | University of Massachusetts at Amherst
Gravitational wave kicks monster black hole out of galactic core
24.03.2017 | NASA/Goddard Space Flight Center
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
24.03.2017 | Materials Sciences
24.03.2017 | Physics and Astronomy
24.03.2017 | Physics and Astronomy