Month: January 2018

Introduction to Exoplanets

CoRoT-7b

Jan 29, 2018 by exoplanetkyo

(Imaginary Image of CoRoT-7b by Rina Maeda from Moriyama SGH)　A tidally locked planet with a surface temperature of over 2000 degrees on the day-side, and ice on the night-side.


(Imaginary Image of CoRoT-7b　Credit: Ryusuke Kuroki, Yosuke Yamashiki )

CoRoT-7b is an exoplanet discovered by the COROT space telescope mission, using the transit method in February 2009. The planet is located in the center of the constellation Monoceros, 489 light years away from our solar system. It has a very small radius at 1.52 times that of the Earth, which was the smallest exoplanet when it was discovered. It has an extremely short orbit of only 0.85 days (about 20 hours) and orbits very close to its host star at a distance of 2.57 million km (0.02 AU, less than 1/20th of the distance between the Sun and Mercury).
Due to its density, CoRoT-7b is classified as a Super Earth, but it has also been considered as a Super Io.
Io, one of Jupiter’s moons, is volcanically active, with an interior temperature that rises due to tidal heating, which is caused by Jupiter’s gravity. CoRoT-7b is thought to be the same, experiencing tidal heating due to the influence of its hoststar CoRoT-7 along with another orbiting planet CoRoT-7c.
CoRoT-7b is tidally locked, due to its short orbital length radius, and because one surface is always facing the host star, that side of the planet can reach over 2000 degrees Celsius, while the opposite side can reach -200 degrees Celsius. ExoKyoto estimates the temperature on the day-side to be about 2110 K (assuming an albedo of 0.1) or 1982 K (assuming an albedo of 0.3).
CoRoT-7b is thought to be a rocky planet like Earth, but it is unlikely to support life due to its severe temperatures. Land on the star side would be covered with molten lava, and there is a possibility of active volcanic activity on the other side.

（執筆　佐藤啓明　修正担当　山敷庸亮）
Victoria Jaggard （2010）「最も地球に似た系外惑星はスーパーイオ」（Reference 2018-1-19）

“AstroArts” 　(2009)　「最小の系外惑星を発見」（参照2018-1-19）

“AstroArts”　(2009)「最小系外惑星は、地球に似た岩石惑星か」（参照2018-1-19）

CoRoT-7’s Habitable Zone

CoRoT-7’s Location on the Stellar Map

For more information on CoRoT-7b, please see the following:
http://www.exoplanetkyoto.org/exohtml/CoRoT-7_bJP.html

Introduction to Exoplanets

GJ667Cc

Jan 29, 2018 by exoplanetkyo

(Image of a tidally locked planet like GJ667Cc Credit: Natsuki Shirako, SGH Moriyama High School)


(Imaginary Image of GJ667Cc Credit: Miu Shimizu  (SGH Moriyama High School) )

The planet, dubbed GJ 667Cc, orbits a red dwarf star 22 light-years from Earth, in the constellation Scorpio. A binary pair of orange dwarf stars are part of the same system.

The new planet has a mass 4.5 times that of Earth and orbits its host star every 28 days.

The red dwarf is relatively dim, so the planet receives slightly less light from its star than Earth does from the sun. But most of the star’s light is infrared, so the planet should absorb more of its incoming energy than Earth does from sunlight.

That means if the planet has a rocky surface—which is predicted for planets less than ten times Earth’s mass—and an atmosphere, it could support liquid water and maybe life said co-discoverer Guillem Anglada-Escudé, who conducted the work while at the Carnegie Institution for Science in Washington, D.C.

“If it has an atmosphere, it’s probably reddish all the time, because the star is really red,” Anglada-Escudé said. “It would be like being evening all the time.”

The host star GJ 667 C has an apparent magnitude of 10.2, with an absolute magnitude of 11.04. It is 0.33 times more massive and 0.34 times bigger compared with our sun. The surface temperature is 3600 K with it’ spectral type of M1.5v. In this planetary system, the extrasolar planet GJ 667 Cc orbits around the star GJ 667 C with its orbital distance of 0.125.

（梨元昴・山敷庸亮）

Reference

http://www.eso.org/public/archives/releases/sciencepapers/eso1328/eso1328a.pdf


GJ667Cc’s Habitable Zone (Kopparapu et al. 2013)


Location of GJ667C on the Stellar Map

For more information about GJ667Cc, please visit the ExoKyoto Database:
http://www.exoplanetkyoto.org/exohtml/GJ_667_C_cJP.html

Famous Exoplanets, Introduction to Exoplanets

Kepler-90 i (Kepler 90 System)

Jan 9, 2018 by exoplanetkyo


Kepler-90 is a G-type main-sequence star located in the Lyra constellation, about 2545 light years from Earth.
It has a mass and volume are about 1.13 and 1.2 times that of our sun. Our sun has a surface temperature of about 5778 Kelvin and it is around 4.6 billion years old, while Kepler-90 has a surface temperature of about 5930 Kelvin and is an estimated 2 billion years old.

<Fig. 1 Imaginary Image of Kepler-90: Image credit Fuka Takagi & Yosuke A. Yamashiki>

A remarkable discovery found that Kepler-90 also has eight planets in its solar system, the same as our own. This makes Kepler-90 hold the record for most planets orbiting a star that we have discovered yet.

<Fig. 2　Planets Orbiting Kepler-90, Using the ExoKyoto Application>

NASA and Google announced n November 14, 2017, that they discovered Kepler-90i, the eighth planet in the Kepler-90 system. Kepler-90i was discovered by analyzing data from the Kepler Space Telescope using a new machine learning system developed by Google. NASA also discovered Kepler-80g using the same system.

<Fig. 3 Imaginary Image of Kepler-90i　Image Credit Ryusuke Kuroki, Yosuke A. Yamashiki>

Kepler-90’s planetary system structure is similar to that of our own solar system. All of the six inner planets are rocky planets, slightly larger than Earth or smaller than Neptune, and the two outer planets are large gas giants. The outermost planet, Kepler-90h, is a Jupiter-sized planet that orbits the host star at the same distance (1.01 AU) as the Earth to the Sun, orbiting the star in about 331 days.

Of course, there are slight differences from our solar system. The outermost planet has an orbital radius roughly equal to that of Earth, and all eight planets are squeezed into a much smaller area than the planets in our solar system. The orbits of the six inner planets are particularly small, for instance, while Mercury has an orbital period of 88 days, Kepler-90i orbits Kepler-90 in just 14.4 days. Consequently, the surface temperature of Kepler-90i can reach 640 Kelvin, and life on the surface is thought to be impossible.

Kepler90Movie

<Movie 1 Kepler-90 and its Planetary Orbits>

It is widely thought that the planets in the Kepler-90 system were once spread out, but for some reason have now moved closer to the host star in their current orbit.

AI produced by Google discovered the new planet by using a neural network of mathematical models, similar to how the human brain works, which identifies a planet’s signal with incredible accuracy. The AI already discovered two exoplanets after analyzing only 670 of the approximately 200,000 celestial objects observed by the Kepler Space Telescope. More exoplanets are expected to be discovered by this method in the near future.

＜村嶋慶哉・山敷庸亮＞

For more information on Kepler-90i, please visit the ExoKyoto Database:

http://www.exoplanetkyoto.org/exohtml/Kepler-90_iJP.html

 For more information about the host star Kepler-90, please visit the ExoKyoto Database:

http://www.exoplanetkyoto.org/exohtml/Kepler-90JP.html