Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

UCSB astronomer uncovers the hidden identity of an exoplanet

02.07.2013
Hovering about 70 light-years from Earth –– that's "next door" by astronomical standards –– is a star astronomers call HD 97658, which is almost bright enough to see with the naked eye.

But the real "star" is the planet HD 97658b, not much more than twice the Earth's diameter and a little less than eight times its mass. HD 97658b is a super-Earth, a class of planet for which there is no example in our home solar system.


This image shows the relative size of the Earth and Sun next to those of HD 97658 (the star) and HD 97658b (the super-Earth exoplanet). Credit: Jason Eastman and Diana Dragomir

While the discovery of this particular exoplanet is not new, determining its true size and mass is, thanks to Diana Dragomir, a postdoctoral astronomer with UC Santa Barbara's Las Cumbres Observatory Global Telescope (LCOGT). As part of her research, Dragomir looked for transits of this exoplanet with Canada's Microvariability & Oscillations of Stars (MOST) space telescope.

The telescope was launched in 2003 to a pole-over-pole orbit about 510 miles high. Dragomir analyzed the data using code written by LCOGT postdoctoral fellow Jason Eastman. The results were published online today in the Astrophysical Journal Letters.

A super-Earth is an exoplanet with a mass and radius between those of the Earth and Neptune. Don't be fooled by the moniker though. Super-Earth refers to the planet's mass and does not imply similar temperature, composition, or environment to Earth. The brightness of HD 97658 means astronomers can study this star and planet in ways not possible for most of the exoplanet systems that have been discovered around fainter stars.

HD 97658b was discovered in 2011 by a team of astronomers using the Keck Observatory and a technique sometimes called Doppler wobble. But only a lower limit could be set on the planet's mass, and nothing was known about its size.

Transits, such as those observed by Dragomir, occur when a planet's orbit carries it in front of its parent star and reduces the amount of light we see from the star ever so slightly. Dips in brightness happen every orbit, if the orbit happens to be almost exactly aligned with our line of sight from Earth. For a planet not much bigger than our Earth around a star almost as big as our Sun, the dip in light is tiny but detectable by the ultraprecise MOST space telescope.

The first report of transits in the HD 97658 system in 2011 turned out to be a false alarm. That might have been the end of the story, but Dragomir knew that the ephemeris of the planet's orbit (a timetable to predict when the planet might pass in front of the star) was not exact. She convinced the MOST team to widen the search parameters, and during the last possible observing window for this star last year, the data showed tantalizing signs of a transit –– tantalizing, but not certain beyond doubt. A year later, MOST revisited HD 97658 and found clear evidence of the planet's transits, allowing Dragomir and the MOST team to estimate the planet's true size and mass for the first time.

"Measuring an exoplanet's size and mass leads to a determination of its density, which in turn allows astronomers to say something about its composition," Dragomir said. "Measuring the properties of super-Earths in particular tells us whether they are mainly rocky, water-rich, mini gas giants, or something entirely different."

The average density of HD 97658b is about four grams per cubic centimeter, a third of the density of lead but denser than most rocks. Astronomers see great significance in that value –– about 70 percent of the average density of Earth –– since the surface gravity of HD 97658b could hold onto a thick atmosphere. But there's unlikely to be alien life breathing those gases. The planet orbits its sun every 9.5 days, at a distance a dozen times closer than we are from our Sun, which is too close to be in the Habitable Zone, nicknamed The Goldilocks Zone. The Goldilocks nickname is apropos: If a planet is too close to its star, it's too hot; if it's too far away, it's too cold, but if it's in the zone, it's "just right" for liquid water oceans, one condition that was necessary for life here on Earth.

Over the past few years, systems with massive planets at very small orbital radii have proved to be quite common despite being generally unexpected. The current number of confirmed exoplanets exceeds 600, with the vast majority having been discovered by radial velocity surveys. These are severely biased toward the detection of systems with massive planets (roughly the mass of Jupiter) in small orbits. Bucking that trend is HD 97658b, which orbits its star at a distance farther than many of the currently known exoplanets. HD 97658b is only the second super-Earth known to transit a very bright star.

"This discovery adds to the still small sample of transiting super-Earths around bright stars," said Dragomir. "In addition, it has a longer period than many known transiting exoplanets around bright stars, including 55 Cnc e, the only other super-Earth in this category. The longer period means it is cooler than many closer-in exoplanets, so studying HD 97658b's properties is part of the progression toward understanding what exoplanets in the habitable zone might be like."

Julie Cohen | EurekAlert!
Further information:
http://www.ia.ucsb.edu

More articles from Physics and Astronomy:

nachricht Igniting a solar flare in the corona with lower-atmosphere kindling
29.03.2017 | New Jersey Institute of Technology

nachricht NASA spacecraft investigate clues in radiation belts
28.03.2017 | NASA/Goddard Space Flight Center

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: A Challenging European Research Project to Develop New Tiny Microscopes

The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.

To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...

Im Focus: Giant Magnetic Fields in the Universe

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...

Im Focus: Tracing down linear ubiquitination

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...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

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...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Researchers shoot for success with simulations of laser pulse-material interactions

29.03.2017 | Materials Sciences

Igniting a solar flare in the corona with lower-atmosphere kindling

29.03.2017 | Physics and Astronomy

As sea level rises, much of Honolulu and Waikiki vulnerable to groundwater inundation

29.03.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>