Featured Research

from universities, journals, and other organizations

Sunny super-Earth? Atmosphere of super-Earth exoplanet observed for time first by two Japanese telescopes

Date:
June 12, 2013
Source:
National Astronomical Observatory of Japan
Summary:
Astronomers have observed the atmosphere of super-Earth "GJ3470b" for the first time using two telescopes. This super-Earth is an exoplanet, having only about 14 times the mass of our home planet, and it is the second lightest one among already-surveyed exoplanets. The observational data revealed that this planet is highly likely to NOT be covered by thick clouds.

Image of Super-Earth “GJ3470b”. The size of the planet (front) and primary star (back) is draw with actual ratio.
Credit: NAOJ

A research team led by Akihiko Fukui (NAOJ), Norio Narita (NAOJ) and Kenji Kuroda (the University of Tokyo) observed the atmosphere of super-Earth "GJ3470b" for the first time using two telescopes at OAO (Okayama Astrophysical Observatory, NAOJ). This super-Earth is an exoplanet, having only about 14 times the mass of our home planet, and it is the second lightest one among already-surveyed exoplanets. The observational data revealed that this planet is highly likely to NOT be covered by thick clouds.

It is very difficult to measure the radii of exoplenets, so in many cases we have information only about masses. However, if an exoplanet has a particular orbit of "Planetary Transit (Primary Transit)" where it passes in front of the primary star (parent star), we can estimate the radius of the planet. During the transit, the observed brightness of the star slightly drops depending on the size of the planet. So, we can estimate the radius of the planet by measuring the fading rate of light very precisely.

The research team performed highly accurate observations on the transit of exoplanet GJ3470b using the Near-Infrared Imager/Spectrograph (ISLE) camera mounted on the 188cm reflecting telescope and three visible light cameras on Multicolor Imaging Telescopes for Survey and Monstrous Explosions (MITSuME) telescope, all belonging to OAO, simultaneously. They measured the brightness dropping rates of the stars in 4 colors (from visible to near infrared). The observations enabled to estimate each radius by color for the planet. As a result, the radius derived from near infrared radiation (1.3 micrometer wavelength) is about 6% shorter than that from visible light. The difference of radii between colors probably is the reflection of the atmospheric characteristics of the planet. When the light from the primary star is transmitted through the thick atmosphere of the planet, certain wavelengths of light are absorbed or scattered by atmospheric molecules, which could cause the difference of apparent radii for each observation wavelength.

So far, the atmosphere of only two super-Earths including GJ3470b has been studied in detail. Estimation of the radius of an exoplanet is a very difficult task. Generally, the fading rate of the light from the star caused by the super-Earth's transit is extremely low. In the case of GJ3470b, however, the size of the primary star is small, so the planet-to-primary star size ratio is relatively large. Therefore, the fading rate of light from the primary star due to the transit becomes larger so it is measurably observable using ground-based telescopes with a medium size diameter.

The estimated radius of the planet by the near infrared radiation observations this time turns out to be about 4.3 times larger than that of Earth. Moreover, theoretical calculations based on the mass and radius of the planet expected that the planet should have huge amount of atmosphere. Fukui commented, "Suppose the atmosphere consists of hydrogen and helium, the mass of the atmosphere would be 5 to 20% of the total mass of the planet. Comparing that to the fact that the mass of Earth's atmosphere is about one ten-thousandth of a percent (0.0001%) of the total mass of the Earth, this planet has a considerably thick atmosphere."

Because differences in radii by colors were found in this observation, it is safe to say that thick clouds do not cover GJ3470b. If thick clouds covered the planet, no differences in radii by color should exist.

The research team plans to conduct observations of even higher accuracy using the Subaru Telescope or other large telescopes. "GJ3470b's orbit of its primary star is very close, at just 0.036 AU (astronomical units), which is about 28 times less than the distance between the Sun and Earth, and revolves in a short cycle of only 3.3 days. Scientists still don't understand well how such a planet was formed. GJ3470b is really possibly not covered by thick clouds, so we believe the composition of the planet's atmosphere could be detected without being blocked by its clouds. If we find any substance, such as water or methane, which becomes ice at low temperatures, it probably means that this planet was originally formed at a distance (a few astronomical units) from the primary star, where ice could exist, and moved toward the primary star thereafter. In contrast, if such substance cannot be found in the atmosphere, it can be thought to be quite likely that this planet was formed near the primary star. We expect to obtain important clues for figuring out how super-Earths were formed through observations of the atmospheric component of GJ3470b," said Fukui.

The frequently sunny weather in Okayama Prefecture was in our favor in obtaining the observation results. A continuously clear sky over several hours through an expected transit time is crucial to precisely measure the radius of an exoplanet. So it can be said that the "Sunny District" Okayama brought on this finding of the "sunny super-Earth." The researchers will continue observations with the telescopes at OAO, hoping to lead to further progress.


Story Source:

The above story is based on materials provided by National Astronomical Observatory of Japan. Note: Materials may be edited for content and length.


Journal Reference:

  1. Akihiko Fukui, Norio Narita, Kenji Kurosaki, Masahiro Ikoma, Kenshi Yanagisawa, Daisuke Kuroda, Yasuhiro Shimizu, Yasuhiro H. Takahashi, Hiroshi Ohnuki, Masahiro Onitsuka, Teruyuki Hirano, Takuya Suenaga, Kiyoe Kawauchi, Shogo Nagayama, Kouji Ohta, Michitoshi Yoshida, Nobuyuki Kawai, Hideyuki Izumiura. OPTICAL-TO-NEAR-INFRARED SIMULTANEOUS OBSERVATIONS FOR THE HOT URANUS GJ3470b: A HINT OF A CLOUD-FREE ATMOSPHERE. The Astrophysical Journal, 2013; 770 (2): 95 DOI: 10.1088/0004-637X/770/2/95

Cite This Page:

National Astronomical Observatory of Japan. "Sunny super-Earth? Atmosphere of super-Earth exoplanet observed for time first by two Japanese telescopes." ScienceDaily. ScienceDaily, 12 June 2013. <www.sciencedaily.com/releases/2013/06/130612093544.htm>.
National Astronomical Observatory of Japan. (2013, June 12). Sunny super-Earth? Atmosphere of super-Earth exoplanet observed for time first by two Japanese telescopes. ScienceDaily. Retrieved October 20, 2014 from www.sciencedaily.com/releases/2013/06/130612093544.htm
National Astronomical Observatory of Japan. "Sunny super-Earth? Atmosphere of super-Earth exoplanet observed for time first by two Japanese telescopes." ScienceDaily. www.sciencedaily.com/releases/2013/06/130612093544.htm (accessed October 20, 2014).

Share This



More Space & Time News

Monday, October 20, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Comet Siding Spring Grazes Mars' Atmosphere

Comet Siding Spring Grazes Mars' Atmosphere

Newsy (Oct. 19, 2014) A comet from the farthest reaches of the solar system passed extremely close to Mars this weekend, giving astronomers a rare opportunity to study it. Video provided by Newsy
Powered by NewsLook.com
Latin America Launches Communications Satellite

Latin America Launches Communications Satellite

AFP (Oct. 17, 2014) Argentina launches a home-built satellite, a first for Latin America. It will ride a French-made Ariane 5 rocket into orbit, and will provide cell phone, digital TV, Internet and data services to the lower half of South America. Duration: 00:41 Video provided by AFP
Powered by NewsLook.com
This Week @ NASA, October 17, 2014

This Week @ NASA, October 17, 2014

NASA (Oct. 17, 2014) Power spacewalk, MAVEN’s “First Light”, Hubble finds extremely distant galaxy and more... Video provided by NASA
Powered by NewsLook.com
Saturn's 'Death Star' Moon Might Have A Hidden Ocean

Saturn's 'Death Star' Moon Might Have A Hidden Ocean

Newsy (Oct. 17, 2014) The smallest of Saturn's main moons, Mimas, wobbles as it orbits. Research reveals it might be due to a global ocean underneath its icy surface. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins