An extrasolar planet is a planet which orbits a star other than the Sun, i.e. which belongs to a planetary system other than our solar system.
Extrasolar planets were discovered during the 1990s as a result of improved telescope technology, such as CCD and computer-based image processing along with the Hubble Space Telescope. Such advances allowed for more accurate measurements of stellar motion, allowing astronomers to detect planets, not visually (the luminosity of a planet being too low for such detection), but by measuring gravitational influences upon stars. In addition, extrasolar planets can be detected by measuring the variance in a star's apparent luminosity, as a planet passes in front of it. Besides the detection of at least 80 planets (mostly gas giants), many observations point to the existence of millions of comets also in extrasolar systems.
The Polish astronomer Aleksander Wolszczan claimed to have found the first extrasolar planets in 1993, orbiting the pulsar PSR 1257+12. Subsequent investigation has determined that these objects are not "true" planets in that they are technically "sub-brown dwarf masses orbiting an object that is or once was a star"; it is believed that they are unusual remnants of the supernova that produced the pulsar, and did not form as conventional planets do.
The first "true" extrasolar planet was announced on October 6, 1995 by Michael Mayor and Didier Queloz; the primary star was 51 Pegasi. Since then dozens of planets have been detected, many by a team led by Geoffrey Marcy at the University of California's Lick and Keck Observatories. The first system to have more than one planet detected was Upsilon Andromedae. The majority of the detected planets have highly elliptical orbits.
There are two main methods of detecting extrasolar planets, which are too faint to be detected by present conventional optical means. The first involves measuring the displacement in the parent star's spectral lines due to the Doppler effect induced by the planet orbiting the star and moving it through mutual gravitation.
The second involves catching the planet as it passes in front of the star's tiny disk which will cause the light of the star to "dip" in a distinctive way, and do so periodically as the planet completes multiple orbits. The second method is theoretically more sensitive, but is newer and has scored fewer successes. It also depends on the plane of the planet's orbit being aligned with the line of sight between the star and the Earth. As a result, any number of stars with planets that are not so aligned will be missed.
Most of the planets found are of relatively high mass (at least 40 times that of the Earth); however, a couple seem to be approximately the size of the Earth. This reflects the current telescope technology, which is not able to detect smaller planets. The mass distribution should not be taken as a reference for a general estimate, since it is likely that many more planets with smaller mass, even in nearby solar systems, are still undetected. Read more ...
First Radio Emission Received From a Planet Outside of Our Solar System Mysterious Universe - December 19, 2020
Astronomers May Have Detected The First Radio Signal From an Exoplanet Science Alert - December 19, 2020
Astronomers Peer Into The Atmosphere of a Rare Exoplanet That 'Shouldn't Exist' Science Alert - October 27, 2020
The discovery of the extraordinary exoplanet LTT 9779b was first announced a month ago. Just 260 light-years away, the planet was immediately pegged as an excellent candidate for follow-up study of its curious atmosphere. But it turns out we didn't even have to wait too long to learn more. LTT 9779b is a little bigger than Neptune, orbiting a Sun-like star - fairly normal so far. But two things are really peculiar. It's so close to its star, the planet orbits once every 19 hours; and, in spite of the scorching heat it must be subjected to at that proximity, LTT 9779b still has a substantial atmosphere. Infrared observations collected by the now-retired Spitzer Space Telescope included the planet's host star, and astronomers have now analyzed those data, publishing their results in a couple of studies.
First Habitable-Zone, Earth-Sized Exoplanet Discovered With Planet-Hunter TESS SciTech Daily - October 25, 2020
TESS, the Transiting Exoplanet Survey Satellite, was launched in 2018 with the goal of discovering small planets around the Sun's nearest neighbors, stars bright enough to allow for follow-up characterizations of their planets' masses and atmospheres. TESS has so far discovered seventeen small planets around eleven nearby stars that are M dwarfs - stars that are smaller than the Sun (less than about 60% of the SunÕs mass) and cooler (surface temperatures less than about 3900 kelvin). In a series of three papers that appeared together this month, astronomers report that one of these planets, TOI-700d, is Earth-sized and also located in its starÕs habitable zone; they also discuss its possible climate.
In a First, Astronomers Find an Exoplanet by Using Radio Waves And a Wobbly Star Science Alert - August 5, 2020
The hunt for exoplanets in our galaxy is a deeply important endeavor. The more exoplanets we find, the better we can understand our own Solar System - and how life emerges in the Universe. To date, over 4,000 exoplanets have been confirmed - but a new discovery could widen the search, helping us to find exoplanets that previously have proven too difficult to detect.
Scientists discover distant 'mirror image' of the Earth and the sun Science Tech Daily - June 7, 2020
The star Kepler-160 and its companion KOI-456.04 are more reminiscent of the Sun-Earth system than any previously known exoplanet-star pair. Among the more than 4,000 known exoplanets, KOI-456.04 is something special: less than twice the size of Earth, it orbits a Sun-like star. And it does so with a star-planet distance that could permit planetary surface temperatures conducive to life. The object was discovered by a team led by the Max Planck Institute for Solar System Research in Gttingen. Its host star, called Kepler-160, actually emits visible light; the central stars of almost all other exoplanets, on the other hand, emit infrared radiation, are smaller and fainter than the Sun and therefore belong to the class of red dwarf stars.
This Newfound Alien Planet Has 3 Suns Space.com - July 27, 2019
Astronomers think they've spotted an alien planet with three suns on its horizon Ń but that still isn't the most interesting thing about the strange new world's sky. Scientists found the world, which they've dubbed LTT 1445Ab, in data gathered by NASA's Transiting Exoplanet Survey Satellite (TESS). LTT 1445Ab orbits just one of the three stars, all of which are red dwarfs in the latter half of their lives, and the system is about 22.5 light-years away from Earth.
Multiple metals - and possible signs of water - found in unique exoplanet PhysOrg - June 1, 2018
The team used the Gran Telescopio Canarias (GTC) to observe WASP-127b, a giant gaseous planet with partly clear skies and strong signatures of metals in its atmosphere. The planet's host star, WASP-127, is also lithium rich, which could point to an AGB star Š a bright red giant thousands of times brighter than the sun Š or a supernova having enriched the cloud of material from which this system originated. The researchers also found possible signs of water. While this detection is not statistically significant, as water features are weak in the visible range, our data indicate that additional observations in the near-infrared should be able to detect it.
Astronomers find exoplanet atmosphere free of clouds Science Daily - May 7, 2018
Scientists have detected an exoplanet atmosphere that is free of clouds, marking a pivotal breakthrough in the quest for greater understanding of the planets beyond our solar system.
Hubble detects helium in the atmosphere of an exoplanet for the first time Science Daily - May 3, 2018
Astronomers using the NASA/ESA Hubble Space Telescope have detected helium in the atmosphere of the exoplanet WASP-107b. This is the first time this element has been detected in the atmosphere of a planet outside the Solar System. The discovery demonstrates the ability to use infrared spectra to study exoplanet extended atmospheres.
Star system has record eight exoplanets BBC - December 14, 2017
Nasa has found a distant star circled by eight planets, equal to the complement in our own Solar System. It's the largest number of worlds ever discovered in a planetary system outside our own. The star known as Kepler-90, is just a bit hotter and larger than the Sun; astronomers already knew of seven planets around it. The newly discovered world is small enough to be rocky, according to scientists. "This makes Kepler-90 the first star to host as many planets as our own Solar System," said Christopher Shallue, a software engineer at Google, which contributed to the discovery. Engineers from Google used a type of artificial intelligence called machine learning to find planets that were missed by previous searches.
Extremely massive exoplanet discovered in the Milky Way's bulge PhysOrg - November 6, 2017
As a result of NASA's Spitzer Space Telescope observations of a microlensing event, astronomers have found an extremely massive alien world circling a star located in the Milky Way's bulge. The newly discovered planet, designated OGLE-2016-BLG-1190Lb, is the first Spitzer microlensing exoworld residing in the galactic bulge.
Earth-like planet just 39 light years away has a thick atmosphere Daily Mail - January 23, 2017
A rocky, oven-hot Earth-sized spotted orbiting a small nearby star just over a year ago is one of the best chances we have of finding alien life outside our solar system. The planet, named GJ1132b, is around 1.2 times the size of Earth and appears to be predominantly composed of rock and iron. Now scientists have taken the closest look yet at GJ1132b, confirming the presence of its thick atmosphere and finding hints the planet could be rich in water.
Newborn giant planet grazes its star Science Daily - June 21, 2016
For the past 20 years, exoplanets known as 'hot Jupiters' have puzzled astronomers. These giant planets orbit 100 times closer to their host stars than Jupiter does to the Sun, which increases their surface temperatures. But how and when in their history did they migrate so close to their star? Now, an international team of astronomers has announced the discovery of a very young hot Jupiter orbiting in the immediate vicinity of a star that is barely two million years old -- the stellar equivalent of a week-old infant. This first-ever evidence that hot Jupiters can appear at such an early stage represents a major step forward in our understanding of how planetary systems form and evolve.
Bizarre Comet-like Alien Planet Is First of Its Kind Live Science - June 25, 2015
A Neptune-size planet appears to be masquerading as a comet, with a gargantuan stream of gas flowing behind it like a comet's tail. The bizarre find is the first of its kind ever discovered by astronomers. The strange, comet-like planet, known as GJ 436b, is orbiting a red dwarf star and is about 22 times as massive as Earth. Astronomers detected the giant gas cloud around the planet using NASA's Hubble Space Telescope and Chandra X-ray Observatory.
Earth-size Kepler-186f NASA - April 18, 2014
Planet Kepler-186f is the first known Earth-size planet to lie within the habitable zone of a star beyond the Sun. Discovered using data from the prolific planet-hunting Kepler spacecraft, the distant world orbits its parent star, a cool, dim, M dwarf star about half the size and mass of the Sun, some 500 light-years away in the constellation Cygnus. M dwarfs are common, making up about 70 percent of the stars in our Milky Way galaxy. To be within the habitable zone, where surface temperatures allowing liquid water are possible, Kepler-186f orbits close, within 53 million kilometers (about the Mercury-Sun distance) of the M dwarf star, once every 130 days. Four other planets are known in the distant system. All four are only a little larger than Earth and in much closer orbits, also illustrated in the tantalizing artist's vision. While the size and orbit of Kepler-186f are known, its mass and composition are not, and can't be determined by Kepler's transit technique. Still, models suggest that it could be rocky and have an atmosphere, making it potentially the most Earth-like exoplanet discovered so far ...
First potentially habitable Earth-sized planet confirmed by Gemini and Keck observatories Science Daily - April 18, 2014
The first Earth-sized exoplanet orbiting within the habitable zone of another star has been confirmed by observations with both the W. M. Keck Observatory and the Gemini Observatory. The initial discovery, made by NASA's Kepler Space Telescope, is one of a handful of smaller planets found by Kepler and verified using large ground-based telescopes. It also confirms that Earth-sized planets do exist in the habitable zone of other stars.
Habitable Worlds NASA - March 3, 2014
Is Earth the only known world that can support life? In an effort to find life-habitable worlds outside our Solar System, stars similar to our Sun are being monitored for slight light decreases that indicate eclipsing planets. Many previously-unknown planets are being found, including over 700 worlds recently uncovered by NASA's Kepler satellite. Depicted above in artist's illustrations are twelve extrasolar planets that orbit in the habitable zones of their parent stars. These exoplanets have the right temperature for water to be a liquid on their surfaces, and so water-based life on Earth might be able to survive on them. Although technology cannot yet detect resident life, finding habitable exoplanets is a step that helps humanity to better understand its place in the cosmos.
Kepler telescope bags huge haul of planets BBC - February 27, 2014
The science team sifting data from the US space agency's (Nasa) Kepler telescope says it has identified 715 new planets beyond our Solar System. This is a huge new haul. In the nearly two decades since the first so-called exoplanet was discovered, researchers had claimed the detection of just over 1,000 new worlds. Kepler's latest bounty are all in multi-planet systems; they orbit only 305 stars. The vast majority, 95%, are smaller than our Neptune, which is four times the radius of the Earth. Four of the new planets are less than 2.5 times the radius of Earth, and they orbit their host suns in the "habitable zone" - the region around a star where water can keep a liquid state.
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