Exoplanets
Although the planets in our solar system may be very interesting, there are thousands of other fascinating planets within our galaxy. These planets are known as exoplanets, and 4,071 exoplanets have been discovered so far, spread across 3,043 solar systems. These planets are generally categorized as gas planets, similar to the gas giants in our solar system such as Uranus and Jupiter, or terrestrial planets, such as Mercury, Earth, or Venus. Here are some different types of planets:
Chthonian Planet: A former gas planet that had its atmosphere stripped off by its star, leaving only the core.
Coreless Planet: A theoretical type of terrestrial planet with no core, meaning that the entire planet is a rocky mantle.
Desert Planet: A terrestrial planet with no or very little liquid water on its surface, such as Mars.
Exomoon: A moon in another solar system.
Exoplanet: A planet outside of our solar system. Also known as an extrasolar planet.
Extragalactic Planet: A planet in another galaxy.
Gas Dwarf: A gas planet with less than 10 times the mass of Earth.
Gaseous Planet: A planet made of gas, such as Neptune or Jupiter.
Gas Giant: A planet made of gas larger than Uranus or Neptune.
Hot Jupiter: A large gas planet that orbits its star at a distance of less than 0.5 AU.
Hot Neptune: A smaller gas planet that orbits its star at a distance of less than 0.5 AU.
Ice Giant: A gas planet made of substances heavier than helium or hydrogen, such as ammonia or methane.
Jovian Planet: A gas planet similar in size to Jupiter or Saturn.
Lava Planet: A terrestrial planet with a surface made of molten rock.
Mega-Earth: A terrestrial planet more than 10 times as massive as Earth.
Mercurian Planet: A rocky planet much smaller than Earth, such as Mercury.
Mesoplanet: A planet significantly smaller than Mercury, but larger than Ceres.
Neptunian Planet: A gas planet similar in size to Uranus or Neptune.
Puffy Planet: A planet that is larger than Jupiter but has a very low density.
Pulsar Planet: A planet that orbits a pulsar, which is a rapidly rotating neutron star.
Rogue Planet: A planet that floats through the galaxy and does not orbit any stars.
Subterran Planet: A rocky planet similar in size to Mars.
Super-Jupiter: A gas planet much larger than Jupiter.
Super-Neptune: A gas planet significantly larger than Neptune but smaller than Saturn.
Superterran Planet: A rocky planet 25 to 100% bigger than Earth. Also known as Super-Earths.
Terran Planet: A rocky planet similar in size to Earth or Venus.
Terrestrial Planet: A planet with a solid surface.
Ultra-Short Period Planets (USPs): Planets that orbit around their star in less than 24 hours.
Chthonian Planet: A former gas planet that had its atmosphere stripped off by its star, leaving only the core.
Coreless Planet: A theoretical type of terrestrial planet with no core, meaning that the entire planet is a rocky mantle.
Desert Planet: A terrestrial planet with no or very little liquid water on its surface, such as Mars.
Exomoon: A moon in another solar system.
Exoplanet: A planet outside of our solar system. Also known as an extrasolar planet.
Extragalactic Planet: A planet in another galaxy.
Gas Dwarf: A gas planet with less than 10 times the mass of Earth.
Gaseous Planet: A planet made of gas, such as Neptune or Jupiter.
Gas Giant: A planet made of gas larger than Uranus or Neptune.
Hot Jupiter: A large gas planet that orbits its star at a distance of less than 0.5 AU.
Hot Neptune: A smaller gas planet that orbits its star at a distance of less than 0.5 AU.
Ice Giant: A gas planet made of substances heavier than helium or hydrogen, such as ammonia or methane.
Jovian Planet: A gas planet similar in size to Jupiter or Saturn.
Lava Planet: A terrestrial planet with a surface made of molten rock.
Mega-Earth: A terrestrial planet more than 10 times as massive as Earth.
Mercurian Planet: A rocky planet much smaller than Earth, such as Mercury.
Mesoplanet: A planet significantly smaller than Mercury, but larger than Ceres.
Neptunian Planet: A gas planet similar in size to Uranus or Neptune.
Puffy Planet: A planet that is larger than Jupiter but has a very low density.
Pulsar Planet: A planet that orbits a pulsar, which is a rapidly rotating neutron star.
Rogue Planet: A planet that floats through the galaxy and does not orbit any stars.
Subterran Planet: A rocky planet similar in size to Mars.
Super-Jupiter: A gas planet much larger than Jupiter.
Super-Neptune: A gas planet significantly larger than Neptune but smaller than Saturn.
Superterran Planet: A rocky planet 25 to 100% bigger than Earth. Also known as Super-Earths.
Terran Planet: A rocky planet similar in size to Earth or Venus.
Terrestrial Planet: A planet with a solid surface.
Ultra-Short Period Planets (USPs): Planets that orbit around their star in less than 24 hours.
2MASS J2126-8140
2MASS J2126-8140 is an exoplanet that orbits the star TYC 9486-927-1 in a solar system located about 87 light-years away. It is a very massive gas planet with a mass of roughly 25.2 quintillion megatons (22.9 million yottagrams), or 13.3 times the mass of Jupiter. It orbits its star at an incredible distance of roughly 6,900 AU, 641 billion miles (1.03 trillion km), or roughly 10.9% of a light-year. In comparison, Neptune, the farthest-orbiting planet in our solar system, orbits the Sun at a distance of only 30 AU, or 2.79 billion miles (4.5 billion km). Despite the distance from its star, 2MASS J2126-8140 has a surface temperature of roughly 2,780 °F (1,527 °C). Due to the planet's incredible distance from its star, a single orbit takes roughly 900,000 years, compared to only 165 years on Neptune. Because 2MASS J2126-8140 is so far from its star, it was originally thought to be a rogue planet when it was discovered.
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J1407b
J1407b is a gas planet orbiting the star 1SWASP J140747. Its star is a main-sequence star similar in size to the Sun. It is a very young star, at an age of only about 16 million years. J1407b was discovered by scientists when its massive ring system caused a 56-day eclipse of its star. The ring system around J1407b consists of over 30 rings, with each one millions of miles in diameter, and the ring system as a whole is about 74 million miles (119.1 million km) in diameter, or 200 times as large as Saturn's ring system. If Saturn had a ring system this big, it would appear much larger than a full moon. Aditionally, divisions in the rings suggest that exomoons have formed around and are orbiting J1407b.
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Kappa Andromedae b
Kappa Andromedae b is a massive gaseous exoplanet (or brown dwarf) orbiting Kappa Andromedae. It is located roughly 130 light-years from Earth. Because it is so massive, with around 13 times the mass of Jupiter (2.09 quintillion gigatons or 24,674 yottagrams), some scientists think it may not be a planet and be a brown dwarf instead. Kappa Andromedae b orbits about 54.2 AU (5.027 billion miles or 8.091 billion km) from its star. Kappa Andromedae b has a surface temperature of around 2,600 °F (1,427 °C), making it reddish in color. Its, Kappa Andromedae, is fairly young, having formed between 20 and 50 million years ago. Kappa Andromedae is about 2.5 times as massive as the Sun, which was once thought to be too massive for a star to be able to have planets.
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Kepler-70b
Kepler-70b is a terrestrial planet that orbits the star Kepler-70. It has a diameter of roughly 6,024 miles (9,695 km). It orbits its star at a distance of only 0.006 AU (557,734 miles or 897,587 km). Because Kepler-70b orbits so close to its star, one year only lasts about 5 hours and 45 minutes. Kepler-70b's surface temperature is 13,332 °F (7,389 °C), which is hotter than the surface of the Sun. It has a density of about 5.5 g/cm³, which is very similar to Earth's density. There is also another planet in Kepler-70's solar system, Kepler-70c. Kepler-70 itself is a subdwarf star, which is a star that is dimmer than main-sequence stars like the Sun but brighter than red or white dwarfs. Kepler-70's diameter is about one-fifth of the Sun's diameter and it is expected to shrink into a white dwarf in the future.
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OGLE-2005-BLG-390Lb
OGLE-2005-BLG-390Lb is a terrestrial exoplanet orbiting the star OGLE-2005-BLG-390L, located about 21,500 light-years away from Earth. It is significantly larger than Earth, with a diameter of 13,381 miles (21,535 km) and a mass of roughly 3.28 quadrillion megatons (2,975 yottagrams). It orbits at a distance of around 242 million miles (389 million km) from its star which would be between Mars and Jupiter in our solar system. One orbit around its star, OGLE-2005-BLG-390L takes almost 10 Earth years. OGLE-2005-BLG-390Lb is extremely cold, with a surface temperature of -370 °F (-223 °C). Due to its low temperature, it has been nicknamed "Hoth" by NASA. Its star, OGLE-2005-BLG-390L has a mass of only 438 quintillion megatons (397 million yottagrams), which is about 22% of the Sun's mass. Its surface is likely made of materials with low boiling points, such as ammonia or nitrogen, which would all be frozen due to the temperatures on the planet.
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Proxima Centauri b
Proxima Centauri b is the closest known exoplanet to Earth, and was discovered in August of 2016. It orbits Proxima Centauri, a star located 4.2 light-years from Earth. Proxima Centauri b orbits its star at a distance of only 0.05 AU, or 4,647,790 miles (7,479,894 km). It is estimated to have a mass roughly 1.3 times the mass of Earth, which would give it a mass of roughly 7.7 quadrillion megatons (6,985 yottagrams). Its diameter is estimated to be somewhere between 6,334 and 11,876 miles (10,194 to 19,112 km). The average temperature on the surface of Proxima Centauri b is -38 °F (-39 °C), which is much colder than on Earth. The star that it orbits, Proxima Centauri, is only about 15% of the Sun's size and 12% of the Sun's mass.
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PSR B1620-26 b
PSR B1620-26 b is an exoplanet located roughly 12,400 light-years from Earth. It orbits around two different stars, PSR B1620-26 and WD B1620-26. PSR B1620-26 b is a gas giant with an average surface temperature of -330.1 °F (-201 °C). It is about 2.5 times as massive as Jupiter, with a mass of about 4.75 quintillion megatons (4,309,128 yottagrams). The main star that it orbits, PSR-B1620-26, is a neutron star that spins 100 times every second and has a diameter of only about 12.4 miles (19.96 km). The other star that it orbits is a white dwarf, with a diameter of only 86,434 miles (139,102 km) but a mass of roughly 676 quintillion megatons (613 million yottagrams). PSR B1620-26 b orbits its star very slowly, with one orbit taking roughly 100 years. PSR B1620-26 b is also the oldest known exoplanet, being roughly 13 billion years old, in comparison to our solar system, which is roughly 4.6 billion years old.
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TRAPPIST-1e
TRAPPIST-1e is a terrestrial exoplanet orbiting the star TRAPPIST-1, about 40 light-years away from Earth. Unlike most solar systems, which only have one planet, the TRAPPIST-1 system has seven planets, with TRAPPIST-1h being the farthest from its star. TRAPPIST-1e orbits only about 0.029 AU (2.72 million miles or 4.38 million km) from its star. However, TRAPPIST-1 has a very low temperature for a star, at only 4,060 °F (2,238 °C). This means that TRAPPIST-1e has a surface temperature of only -16.7 °F (-27.0 °C). TRAPPIST-1e is similar in size to Earth, with a diameter of 7,205 miles (11,595 km) and has only slightly weaker gravity than Earth at 9.13 m/s². TRAPPIST-1e scored at a 0.95 on the Earth Similarity Index (ESI), which is a measure of how similar a planet is to Earth. The highest any planet in our solar system was Mars, with a 0.73 and the lowest was Jupiter, with a 0.12. TRAPPIST-1e is also similar to Earth because its density is 5.65 g/cm³, compared to Earth's 5.51 g/cm³. It is also very likely to have liquid water on its surface, and its interior is made of rock and iron, just like Earth.
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TrES-2b
TrES-2b is a hot Jupiter that orbits the star GSC 03549-02811. It is slightly larger than Jupiter, with a diameter of approximately 110,513 miles (177,853 km). It is also slightly more massive than Jupiter, with a mass of about 2.28 quintillion megatons (2,068,381 yottagrams). Because TrES-2b is a hot Jupiter, it orbits its very close to its star. On average, TrES-2b orbits only 3,305,508 miles (5,319,699 km) from its star, which is several times closer than Mercury orbiting the Sun. TrES-2b also orbits very quickly, with a single orbit around its star taking less than 2.5 Earth days. However, the reason that TrES-2b is famous is because it is the darkest known exoplanet. It reflects only 0.04% of the light that hits it, making it even darker than coal. The planet in our solar system that reflects the most light is Venus, which reflects about 75% of the light that hits it. Even Mercury, the least reflective planet in our solar system, still reflects 11% of the light that hits it. Some scientists think that TrES-2b may be so dark because it may be missing the reflective clouds that many other gas giants have.
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