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Oct. 23, 2015
In celebration of the 20th anniversary of the first confirmed planet around a sun-like star, more than 60 leaders in the field of exoplanet observations chose their favorites among the nearly 2,000 known exoplanets. Some of the exoplanets are rocky, some are gaseous, and some are very, very odd. But there's one thing each one of these strange new worlds has in common: All have advanced scientific understanding of our place in the cosmos.
Check out the astronomers' top 20 list of exoplanets below, along with artist's concepts depicting what they might look like.
1. Kepler-186f
Image above: Kepler-186f was the first rocky planet to be found within the habitable zone -- the region around the host star where the temperature is right for liquid water. This planet is also very close in size to Earth. Even though we may not find out what's going on at the surface of this planet anytime soon, it's a strong reminder of why new technologies are being developed that will enable scientists to get a closer look at distant worlds. Image Credits: NASA Ames/SETI Institute/JPL-Caltech.
2. HD 209458 b (nickname "Osiris")
Image above: The first planet to be seen in transit (crossing its star) and the first planet to have it light directly detected. The HD 209458 b transit discovery showed that transit observations were feasible and opened up an entire new realm of exoplanet characterization. Image Credits: NASA, European Space Agency, Alfred Vidal-Madjar (Institut d'Astrophysique de Paris, CNRS).
3. Kepler-11 system
Image above: This was the first compact solar system discovered by Kepler, and it revealed that a system can be tightly packed, with at least five planets within the orbit of Mercury, and still be stable. It touched off a whole new look into planet formation ideas and suggested that multiple small planet systems, like ours, may be common. Image Credits: NASA/JPL-Caltech.
4. Kepler-16b
Image above: A real-life "Tatooine," this planet was Kepler's first discovery of a planet that orbits two stars -- what is known as a circumbinary planet. Image Credits: NASA/JPL-Caltech.
5. 51 Pegasi b
Image above: This giant planet, which is about half the mass of Jupiter and orbits its star every four days, was the first confirmed exoplanet around a sun-like star, a discovery that launched a whole new field of exploration. Image Credits: NASA/JPL-Caltech.
6. CoRoT 7b
Image above: The first super-Earth identified as a rocky exoplanet, this planet proved that worlds like the Earth were indeed possible and that the search for potentially habitable worlds (rocky planets in the habitable zone) might be fruitful. Image Credits: ESO/L. Calçada.
7. Kepler-22b
Image above: A planet in the habitable zone and a possible water-world planet unlike any seen in our solar system. Image Credits: NASA/Ames/JPL-Caltech.
8. Kepler-10b
Image above: Kepler's first rocky planet discovery is a scorched, Earth-size world that scientists believe may have a lava ocean on its surface. Image Credits: NASA/Kepler Mission/Dana Berry.
9. Kepler-444 system
Image above: The oldest known planetary system has five terrestrial-sized planets, all in orbital resonance. This weird group showed that solar systems have formed and lived in our galaxy for nearly its entire existence. Image Credits: Tiago Campante/Peter Devine.
10. 55 Cancri e
Image above: 55 Cancri e is a toasty world that rushes around its star every 18 hours. It orbits so closely -- about 25 times closer than Mercury is to our sun -- that it is tidally locked with one face forever blisters under the heat of its sun. The planet is proposed to have a rocky core surrounded by a layer of water in a "supercritical" state, where it is both liquid and gas, and then the whole planet is thought to be topped by a blanket of steam. Image Credits: NASA/JPL-Caltech.
11. HD 189733 b
Image above: This exoplanet, about the size of Jupiter, is one of the most studied exoplanets and is the first caught passing in front of its parent star in X-rays. NASA’s Chandra X-ray Observatory and the European Space Agency’s XMM Newton Observatory have been used to observe a dip in X-ray intensity as HD 189733b transits its parent star. Image Credits: NASA/ESA/G. Bacon (STScI).
12. PSR B1257+12 system
Image above: Discovered in 1992 and 1994, the planets that orbit pulsar PSR B1257+12 are not only the smallest planetary bodies known to exist outside our solar system, they also orbit a neutron star. These weird "pulsar planets" demonstrated that planets exist in all environments in the galaxy -- even around the remnants of an exploded star. Image Credits: NASA/JPL-Caltech.
13. K2-3
Images above: Three super-Earths discovered by the K2 mission orbiting a nearby star. Their mass and radius are already known and soon they may reveal their atmospheric composition. Image Credits: ESO/M. Kornmesser/Nick Risinger/ L. Calcada.
14. HR 8799
Image above: The first directly imaged multi-exoplanet system. This system contains a debris disk and at least four massive planets. Image Credits: NRC-HIA, Christian Marois, Keck Observatory.
15. Kepler-36 system
Image above: The two known planets in this system have the most closely spaced orbits ever confirmed. On their closest approach, the neighboring duo comes within about 1.2 million miles of each other -- only five times the Earth-moon distance. Image Credits: ESO.
16. HD 114762 b
Image above: Discovered in 1989, three years prior to the pulsar planets and six years prior to 51 Peg b, HD 114762 b is truly the first discovered planet around a sun-like star. However, because its mass is 11 times that of Jupiter and was found in an orbit of 84 days, it was initially assumed (incorrectly) to be a brown dwarf. Image Credits: NASA/JPL-Caltech.
17. Kepler-452b
Image above: This world is the first Earth-sized planet found in the habitable zone of a sun-like star. The planet is 60 percent larger than Earth and 5 percent farther from its parent star than Earth is from the sun. Image Credits: NASA/Ames/JPL-Caltech.
18. HD 80606 b
Image above: This world has the most eccentric orbit, and as one scientist put it, "wears its heart on its sleeve," with storms, rotation, atmospheric heating, and a crazy orbit all plainly visible. Image Credits: NASA/JPL-Caltech/ UCSC.
19. WASP-47
Image above: Part of a compact multi-planet system, it's the only known hot Jupiter with close planetary companions. Image Credits: NASA/JPL-Caltech.
20. OGLE-2005-BLG-390
Image above: Part of a compact multi-planet system, it's the only known hot Jupiter with close planetary companions. Image Credits: NASA/JPL-Caltech.
NASA’s Jet Propulsion Laboratory, in Pasadena, manages NASA's Exoplanet Exploration program office. More information about exoplanets and NASA's planet-finding program is at http://planetquest.jpl.nasa.gov . Caltech manages JPL for NASA.
Images (mentioned), Text, Credits: NASA/Tony Greicius/JPL/Whitney Clavin.
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