Known Types of Alien Worlds

KNOWN TYPES OF ALIEN WORLDS In this representative example, various types of planets found orbiting other stars ("exoplanets“) are shown together in a single solar system. In reality, the different planets orbit different types of stars, from G-type yellow stars similar to our sun to small red dwarf stars. Planets and orbits are not shown to scale. Mega-Earth I Example: Kepler-10c Mass: about 17 Earth masses Diameter: 18,000 miles (28,970 kilometers) Orbit radius: About 22 million miles (35.4 milllon km) 1 A Mega-Earth has a mass similar to Neptune but is a rocky planet, not a gas giant Hot Jupiter 1 Example: 51 Pegasi b I Mass: about 0.5 Jupiter masses 1 Orbit radius: Less than 4.9 million miles (7.9 million km) I A Hot Jupiter is a massive gas giant planet orbiting close to its star Hot Neptune 1 Example: Gliese 436 b - Mass: about 22 Earth masses 1 Orbit radius: 2.7 million miles (4.4 million km) IA Hot Neptune is a gas giant planet orbiting close to its star Cthonian Planet LExample: COROT-7b 1 Mass: uncertain, about 8 Earth masses 1 Orbit radius: 1.6 million miles (2.58 million km) TA Cthonian planet is believed to be a Hot Jupiter that has lost all of its thick atmosphere, leaving the rocky core Super-Earth : Example: Kepler-22b I Mass: Uncertain 1 Radius: 2.4 times that of Earth 1 Orbit radius: 79 million miles (127 million km) IA Super Earth is larger than Earth but smaller than a gas giant such as Neptune Super Neptune Water World I Example: GJ 1214b - Mass: 6.55 Earth masses Orbit radius: 1.33 million miles (2.14 million km) 1 Example: HAT-P-11b I Mass: 26 Earth masses 1 Orbit radius:4.9 million miles (7.9 million km) 1 A super-Neptune is somewhat larger and more massive than Neptune Terrestrial Planet 1 Example: Earth I Mass: 0.003 Jupiter mass 1 Orbit radius: 93 million miles (150 million km) 1A goal of the exoplanet search is to find an alien I A water world is a super-Earth that may have vast oceans of liquid waterr analog of Earth, or an "ехо-Еarth" HABITAB LE where an Earth-size planet can have liquid water on its surface Gas Giant 1 Example: Jupiter I Mass: 318 Earth masses 1 Orbit radius: 484 million mifes (778 million km) A gas giant is a huge planet with a thick atmosphere of mostly hydrogen and helium surrounding a tiny, rocky core Neptune 1 Mass: 17 Earth masses 1 Orbit radius:2.8 billion miles Brown Dwarf 1 Example: Gliese 229B - Mass: 20-50 Jupiter masses 1 Orbit radjus: 3.73 billion miles (6 billion km) 1 A brown dwarf is smaller than a star and too How in mass to sustain hydrogen fusion (4.5 billion km) I Neptune is a gas giant with a thick atmosphere of hydrogen, helium, ammonia and methane surrounding a tiny, rocky core Rogue Planet I Example: Cha 110913-773444 1 Mass: 8 Jupiter masses - Orbits the Milky Way galaxy independently 1 Rogue planets were ejected from their solar system and now wander between the stars The Search Goes On Only a tiny fraction of our galaxy has been searched for possible Earth-type planets. Up until now, only large planets could be found, but search technology is rapidly approaching the point where small rocky planets similar to Earth might be detectable. Large Jupiter-size planets have been found nearly 28,000 light-years away. MILKY WAY GALAXY Exo-Earth search radius: 1,500 light-years EARTH SOURCES: NASA, AMES RESEARCH CENTER, JET PROPULSION LABORATORY, HARVARD-SMITHSONIAN CENTER FOR ASTROPHYSICS, CALIFORNIA INSTITUTE OF TECHNOLOGY, ROBERT HURT (GALAXY MAP) KARL TATE / O SPACE.com SPACE,