Famous Exoplanets, Introduction to Exoplanets

TOI-1278 b

Apr 7, 2022 by exoplanetkyo

TOI-1278 b is an exoplanet orbiting the star TOI-1278, located 246.1 light-years (parsecs) from the Solar System, and was announced in 2021.
The star TOI-1278 has an apparent magnitude of 13.5 and an absolute magnitude of 9.1.
This star has 0.6 times the mass of the Sun, a radius of 0.6 times that of the Sun, a surface temperature of 3,799 K, and a spectral type of MOV.
In this star’s planetary system, TOI-1278 b orbits the star TOI-1278 with an orbital period of 14.5 days and a semi-major axis of 0.10 astronomical units (14,211,797.7 km).

TOI-1278b was announced in 2021. It is a gas giant orbiting the M-type star TOI-1278, located in the constellation Cygnus, approximately 246.1 light-years (75.5 parsecs) from the Solar System. It has a mass 18.5 times that of Jupiter and a radius 1.09 times that of Jupiter. It takes 14.5 days to complete one orbit around its star and is located at a distance of 0.095 astronomical units from it. Such a close proximity to the star is characteristic among known M-dwarf systems.

The “TOI” in a star’s name stands for “Tess Objects of Interest” and refers to a catalog of celestial objects for which the TESS exoplanet-hunting satellite has indicated the potential presence of planets. Celestial objects listed in the TOI catalog undergo follow-up observations using methods other than the transit method, such as Doppler spectroscopy and direct imaging. (文責：小川)

References：
Artigau et al. 2021., TOI–1278 B: SPIRou Unveils a Rare Brown Dwarf Companion in Close-in Orbit around an M Dwarf, The Astronomical Journal 162 144
https://exoplanets.nasa.gov/exoplanet-catalog/

For more information about TOI-1278 b, please visit the Exokyoto database page below.
TOI-1278 b (exoplanetkyoto.org)

Famous Exoplanets, Introduction to Exoplanets

Proxima Centauri c

Feb 10, 2022 by exoplanetkyo

Proxima Centauri c is a super-Earth-sized exoplanet discovered in 2019 using the radial velocity method. Its estimated radius is 0.16 times that of Jupiter (1.8 times that of Earth), and its estimated mass is 0.03 times that of Jupiter (9.54 times that of Earth). Its host star is Proxima Centauri (an M-type star located approximately 4.2 light-years from the Sun), and Proxima Centauri c orbits at a distance of about 1.5 AU from the star, completing one orbit in approximately 5.3 years. Furthermore, its orbit lies just outside that of Proxima Centauri b, which is known as the closest potentially habitable planet to Earth. Proxima Centauri c itself lies far outside the star’s habitable zone and, with an estimated blackbody temperature of -231°C, is considered uninhabitable.

(※For more information on the host star Proxima Centauri, be sure to check out the article on Proxima Centauri b!)

It is generally believed that super-Earth-sized planets form near their host star’s snow line. However, in the case of Proxima Centauri c, Proxima Centauri’s snow line is located around 0.088 AU, while Proxima Centauri c is approximately 1.5 AU from its host star; therefore, this planet appears to challenge that theory. On the other hand, it is possible that this planet does not actually exist. Currently, space telescopes such as Gaia, launched by the ESA, are attempting to confirm the existence of Proxima Centauri c.

（文責：白樫）

References:
1) Proxima Centauri c, ExoKyoto, http://www.exoplanetkyoto.org/exohtml/Proxima_Centauri_cJP.html
2) “A second planet might orbit the closest star to the sun, and astronomers think it’s a super-Earth”, INSIDER,
https://www.businessinsider.com/super-earth-orbits-proxima-centauri-closest-star-to-sun-2020-1

Artist’s concept of Proxima Centauri c (Scenario 1: a rocky planet)
(Image Credit: Yuna Watanabe, Habitable Research Group Moriyama Junior High School )

Artist’s concept of Proxima Centauri c (as a rocky planet, part 2)
(Image Credit: Yuna Watanabe, Habitable Research Group Moriyama Junior High School )

Artist’s concept of Proxima Centauri c (as a gas giant)
(Image Credit: Yuna Watanabe, Habitable Research Group Moriyama Junior High School )

Famous Exoplanets

TOI-1231 b

Aug 26, 2021 by exoplanetkyo

TOI-1231 b is an exoplanet orbiting the star TOI-1231, located 89.7 light-years (27.5 parsecs) from the Solar System; it was announced in 2021.
The star TOI-1231 has an apparent magnitude of 12.3 and an absolute magnitude of 10.1.
This star has 0.5 times the mass of the Sun, a radius of 0.5 times that of the Sun, a surface temperature of 3562 K, and a spectral type of M3V.
The planet TOI-1231 b orbits the star TOI-1231 with an orbital period of 24.2 days and a semi-major axis of 0.13 astronomical units (19,268,205.7 km).

TOI-1231b was discovered by TESS.
Its host star, TOI-1231, is classified as an M-type main-sequence star. Stars smaller than G-type main-sequence stars—the category to which the Sun belongs—are classified as M-type main-sequence stars, and TOI-1231 is only about half the size of the Sun. Due to its apparent magnitude of 12.3 and its location in the constellation Cygnus, it cannot be seen from most regions of Japan.
This article focuses on TOI-1231b, the only planet discovered so far.
Previously, it was predicted that using TESS, only a single planet—rock-free and no larger than Neptune—would be found in the habitable zone of an M-type dwarf star. TOI-1231b is attracting attention as the first planet to meet these criteria.
One of the characteristics of TOI-1231b is that its surface temperature is approximately 330 K (about 57°C).
Future research is anticipated to determine whether liquid water exists and if there is a possibility of life.
（文責：藤井）

If you’d like to learn more about TOI-1231 b, click the link below↓

TOI-1231 b (exoplanetkyoto.org)

Famous Exoplanets

HD 40307 ｇ

Sep 26, 2020 by exoplanetkyo

HD 40307 g was discovered using the radial velocity method, based on data observed by HARPS in 2012. The planet’s host star, HD 40307, is classified as a K type main-sequence star. The K-type star is slightly smaller than our Sun’s G-type star and is actually only 0.77 times the size of the Sun. Unfortunately, the star’s apparent magnitude is only 4.17, so it is not visible from Earth, but it is located 42 light-years away in the Pictor constellation. Six planets have been discovered orbiting HD 40307.

HD 40307 g, is the outermost of the six planets found orbiting the star. The planet orbits about 0.6 the distance between the Sun and Earth in about 197 days.
It is assumed to be about 7.1 times the mass of the Earth, which makes it a rocky planet. The radial velocity method measures the changes in the wavelength of light of a star to detect a planet. This is based on the Doppler Effect; the wavelength of light is shorter when the star is moving toward us and longer when the star is moving away. This means we can only detect the earthward motion, and the measured value versus the true value will be different depending on the observable angle. Therefore, only the lower limit is known.

この惑星の最大の特徴は、ハビタブルゾーンつまり水が液体で存在できる範囲にいることです。さらに、この星は大きさの分類上スーパーアースに分類されますが、初めて発見されたハビタブルゾーンにいるスーパーアース型の太陽系外惑星になります。くわえて、潮汐ロックがかかっている可能性が比較的低くなっています。潮汐ロックとは公転周期と自転周期が完全に一致して、主星に向けられる面がいつも同じになることです。比較的多くのハビタブル惑星が多く見つかっているより軽い恒星系では主星の温度が低いため主星と惑星の距離が近くなり潮汐ロックがかかっている可能性が高くなってしまいます。潮汐ロックがかかってしまうと主星に向いている面の気温が高くなり、逆に逆面では気温が低くなり生物が生きていくのにあまり適さない環境になってしまいます。HD　40307ｇは比較的その恐れが少なく生物が存在する希望がより高くなります。
（大山　航）

Kepler-1649cについてのより詳しいデータは以下のデータベースページをご参考に。

http://www.exoplanetkyoto.org/exohtml/HD_40307_gJP.html

• M. Mayor, S. Udry, C. Lovis, F. Pepe, D. Queloz, W. Benz, J.-L. Bertaux, F. Bouchy, C. Mordasini, D. Segransan (2009). “The HARPS search for southern extra-solar planets. XIII. A planetary system with 3 Super-Earths (4.2,6.9&9.2Earth masses)”. Astronomy and Astrophysics 493 (2): 639-644
• Tuomi, Anglada-Escude, Gerlach, Jones, Reiners, Rivera, Vogt, Butler, Mikko, Guillem, Enrico, Hugh R. R., Ansgar, Eugenio J., Steven S., R. Paul (2012年). “Habitable-zone super-Earth candidate in a six-planet system around the K2.5V star HD 40307”

Famous Exoplanets, Introduction to Exoplanets

AU Mic b

Jun 29, 2020 by exoplanetkyo

AU Microscopii (hereinafter referred to as AU Mic) is a star located in the southern constellation Microscopium about 32.3 light-years (9.79 Parsecs) away from our solar system. AU Mic is a young red dwarf star that is classified as an M1 Ve. Its apparent magnitude is 8.7 and its temperature is 3730 K. It is a small star, at only 60% the radius of our sun, and it radiates only 9% of our sun’s light.

The most interesting thing about AU Mic is the debris disk found around it, which is circumstellar disk of dust that orbits the star. This disk was found and then confirmed in 2003 by Paul Kalas and collaborators using the University of Hawaii 2.2-m telescope on Mauna Kea, Hawaii. The disk was detected from about 35 to 210 astronomical units from the star, a region where dust lifetimes exceed the present stellar age. The total amount of dust that makes up the disk is thought to be at least 6 lunar masses.

Within the debris disk, a planet was recently discovered. AU Mic b orbits its host star in about 8.46 days at a distance of 0.07 astronomical units. It has a radius 0.4 of Jupiter and a mass of about 0.18 of Jupiter. The fact that a planet exists within the debris disk offers scientists a chance to study planet formation and evolution.

(Ling Cassandra)

Imaginary Picture of AU Mic b (Ryusuke Kuroki, Yosuke A. Yamashiki)

Size of AU Mic & AU Mic b in comparison with our Solar System

**Habitable zone calculated based on Kopparapu et al.(2013) around the star AU Mic**

For more information on AU Mic, please visit the ExoKyoto database:

http://www.exoplanetkyoto.org/exohtml/AU_Mic_b.html

Imaginary Picture of AU Mic b by Miu Shimizu

Introduction to Exoplanets

Kepler-1649 c

Apr 17, 2020 by exoplanetkyo

Kepler-1649 c is an Earth-sized exoplanet discovered by re-analyzing data from the Kepler space telescope. Its size is around 1.06 times the radius of the earth, and the mass is 1.21 times the mass, estimated by ExoKyoto. The host star, Kepler-1649, is an M5V type red-dwarf with a surface temperature of 3240K. Its radius is estimated to be about 25% of the sun and its mass is about 21.9%. The exoplanet orbits the red dwarf, at around 0.0855 astronomical units (1,280,000 km) which takes about 19.5 days. The estimated black body temperature of Kepler-1649 c is 245.39K assuming an albedo of 0.3, which is almost the same as the earth (255K). If the atmospheric pressure and components are similar to the earth, it is very probable that its environment also resembles the Earth

However, the exoplanet is most likely tidally locked, due to it revolving around a red dwarf star. Also, the light seen from the surface of the planet would be significantly different from sunlight on Earth, composed of about 90% infrared rays and only 8.87% visible light component (according to Exo Kyoto).

Ultraviolet radiation, including extreme ultraviolet radiation, is estimated to be about 0.17%, which requires more detailed observation.