Extrasolar Planets - Exoplanets

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 ...

In the News ...

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.

Exoplanet shines with glowing water atmosphere   Scientific American - January 23, 2017

Credit: Engine House VFX, At-Bristol Science Centre, University of Exeter
Scientists have found compelling evidence for a stratosphere on an enormous planet outside our solar system. The planet's stratosphere -- a layer of atmosphere where temperature increases with higher altitudes -- is hot enough to boil iron.

' Signs of Alien Air Herald a New Era of Exoplanet Discoveries   Scientific American - January 23, 2017

For astronomers seeking Earth twins around other stars, the exoplanet GJ 1132 b probably isn't an identical sibling - but it may be the closest cousin yet found. It weighs in at just over one Earth mass, but circles its star in a warm orbit that could make it more like Venus than our own world. Moreover, its diameter is nearly 50 percent larger than that of Earth, suggesting it possesses a thick atmosphere. Now, after taking the closest-ever look at GJ 1132 b, a European collaboration has confirmed the presence of its atmosphere and found hints it might contain water and methane.

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.

The Five Most Earth-Like Exoplanets (So Far)   Epoch Times - November 19, 2015
Many of the claims about the habitability of exoplanets are greatly exaggerated. Here are the five top candidates for an Earth-twin, based on their ESI values.
1. Kepler 438b
2. Gliese 667Cc
3. Kepler 442b
4. Kepler 62e & 62f
5. Kepler 452b

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.

  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.

Researchers use Hubble Telescope to reveal cloudy weather on alien world   PhysOrg - December 31, 2013

Weather forecasters on exoplanet GJ 1214b would have an easy job. Today's forecast: cloudy. Tomorrow: overcast. Extended outlook: more clouds. A team of scientists led by researchers in the Department of Astronomy and Astrophysics at the University of Chicago report they have definitively characterized the atmosphere of a super-Earth class planet orbiting another star for the first time.

Distant 'waterworld' is confirmed   BBC - February 20, 2012

GJ 1214b is one of the most interesting exoplanets yet detected. Astronomers have confirmed the existence of a new class of planet: a waterworld with a thick, steamy atmosphere. Exoplanet GJ 1214b is a so-called "Super Earth" - bigger than our planet, but smaller than gas giants such as Jupiter. Observations using the Hubble telescope now seem to confirm that a large fraction of its mass is water. The planet's high temperatures suggest exotic materials might exist there. The planet was discovered in 2009 by ground-based telescopes. It is about 2.7 times the Earth's diameter, but weighs almost seven times as much. It orbits its red-dwarf star at a distance of just two million km, meaning temperatures on GJ 1214b probably reach above 200C.

  Re-thinking an alien world   PhysOrg - January 16, 2012

Forty light years from Earth, a rocky world named "55 Cancri e" circles perilously close to a stellar inferno. Completing one orbit in only 18 hours, the alien planet is 26 times closer to its parent star than Mercury is to the Sun. If Earth were in the same position, the soil beneath our feet would heat up to about 3200 F. Researchers have long thought that 55 Cancri e must be a wasteland of parched rock.

Kepler 22-b: Earth-like planet confirmed   BBC - December 6, 2011

Astronomers have confirmed the existence of an Earth-like planet in the "habitable zone" around a star not unlike our own. The planet, Kepler 22-b, lies about 600 light-years away and is about 2.4 times the size of Earth, and has a temperature of about 22C. It is the closest confirmed planet yet to one like ours - an "Earth 2.0". However, the team does not yet know if Kepler 22-b is made mostly of rock, gas or liquid.

Alien Planet Is Rolling Over, Forcing 4 Others to Do Same   Live Science - December 1, 2011

A huge alien planet turns super-slow somersaults as it hurtles through space, dragging its four sibling planets along for the topsy-turvy ride, a new study suggests. The giant exoplanet, known as 55 Cancri d, gets tugged by a faraway companion star as it orbits its own parent star. As a result, the planet performs a flip over the course of millions of years, and the other four planets in the system follow suit, researchers said.

NASA Finds Smallest Earthlike Planet Outside Solar System   National Geographic - January 10, 2011

Rocky world 1.4 times Earth's size is "missing link," astronomer says. NASA's Kepler spacecraft has confirmed the discovery of a rocky world just 1.4 times the size of Earth circling a sunlike star.

Rocky exoplanet milestone in hunt for Earth-like worlds   BBC - January 10, 2011
Astronomers have discovered the smallest planet outside our solar system, and the first that is undoubtedly rocky like Earth. Measurements of unprecedented precision have shown that the planet, Kepler 10b, has a diameter slightly lower than Earth's, and a mass 4.6 times higher. However, because it orbits its host star so closely, the planet could not harbor life. The discovery has been hailed as "among the most profound in human history".

  Astronomers find first planet from another galaxy   PhysOrg - November 18, 2010
An exoplanet orbiting a star that entered our Milky Way from another galaxy has been detected by a European team of astronomers using the MPG/ESO 2.2-meter telescope at ESO's La Silla Observatory in Chile. The Jupiter-like planet is particularly unusual, as it is orbiting a star nearing the end of its life and could be about to be engulfed by it, giving tantalizing clues about the fate of our own planetary system in the distant future.

Discovery of an extrasolar earth-sized planet   PhysOrg - October 8, 2010
There are now over 490 confirmed extrasolar planets. The vast majority are gas giants like Jupiter, but they are much stranger because many orbit close to their stars and so are much hotter than Jupiter (some are even closer to their star than Mercury is to the sun).

Water-Ice Super-Earths   PhysOrg - August 27, 2010
A "super-Earth" is a planet around another star (an "exoplanet") whose mass is less than about ten times that of the Earth. Of the 480 or so extrasolar planets now known, most have masses larger than the mass of Jupiter, which is 318 times more massive than the Earth. About two dozen, though, appear to have masses that put them into the super-Earth category. About 70 exoplanets have orbits that happen to be aligned such that the planet passes directly between the star and the Earth (a transit).

New Planet System Found May Have Hidden "Super Earth"   National Geographic - August 26, 2010
A newly discovered planetary system orbiting a sunlike star may conceal a rare super-Earth, according to data from NASA's Kepler space telescope. Launched last March, Kepler was designed to look for extrasolar planets, aka exoplanets, via transits the periodic dimming of light from stars due to planets passing in front them, as seen from the telescope's vantage point. (Read about Kepler's first planet discoveries.) After analyzing seven months' worth of data from Kepler, a team led by Matt Holman of the Harvard-Smithsonian Center for Astrophysics found two transiting exoplanets orbiting the star Kepler-9, which lies about 2,300 light-years from Earth.

Rich exoplanet system discovered   BBC - August 24, 2010
The star is 127 light years away, in the southern constellation of Hydrus. They say this is the "richest" system of exoplanets - planets outside our own Solar System - ever found.

  Richest planetary system discovered around Sun-like star HD 10180   PhysOrg - August 24, 2010

'Superstorm' rages on exoplanet   BBC - June 23, 2010

Astronomers have measured high-speed winds in the atmosphere of a planet orbiting a distant star. Data on carbon monoxide gas in the atmosphere show that it is streaming at fierce speeds from the planet's hot day side to its cool night side. Writing in Nature, a team detected longitudinal winds of roughly 2km/s (7,000km/h) in the atmosphere of a "hot Jupiter" planet. Hot Jupiters are gas giants that orbit very close to their parent stars.

'Super-Earths' orbit nearby stars   BBC - December 15, 2009

Planet-hunters have discovered two "super-Earths" orbiting two nearby Sun-like stars. These rocky planets are larger than the Earth but much smaller than ice giants such as Uranus and Neptune. Scientists say the discoveries are a step towards finding potentially habitable planets - smaller planets that are comparable to the Earth.

Nearby "Super Earth" May Have Oceans, Thick Atmosphere   National Geographic - December 16, 2009

A newfound "water world" orbiting a star just 40 light-years away is the first known Earthlike planet close enough for us to "sniff" its atmosphere, astronomers say. Dubbed GJ 1214b, the planet is only about 2.7 times larger than Earth and about 6.5 times more massive.

Discovery of a Retrograde or Highly Tilted Extrasolar Planet   PhysOrg - November 18, 2009
Astronomers have found that the extrasolar planet HAT-P-7b has a retrograde or highly tilted orbit. Studying such planets is important in understanding the diversity of planetary systems and assessing current models of how planets migrate. The findings could help astrobiologists in the search for habitable planets beyond our solar system.

  32 New Exoplanets Found   PhysOrg - October 19, 2009

32 New Planets Found Outside Our Solar System   National Geographic - October 19, 2009
The longest set of HARPS measurements ever made has firmly established the nature of the smallest and fastest-orbiting exoplanet known, CoRoT-7b, revealing its mass as five times that of Earth's. Combined with CoRoT-7b's known radius, which is less than twice that of our terrestrial home, this tells us that the exoplanet's density is quite similar to the Earth's, suggesting a solid, rocky world. The extensive dataset also reveals the presence of another so-called super-Earth in this alien solar system.

  First Solid Evidence for a Rocky Exoplanet   PhysOrg - September 16, 2009

The longest set of HARPS measurements ever made has firmly established the nature of the smallest and fastest-orbiting exoplanet known, CoRoT-7b, revealing its mass as five times that of Earth's. Combined with CoRoT-7b's known radius, which is less than twice that of our terrestrial home, this tells us that the exoplanet's density is quite similar to the Earth's, suggesting a solid, rocky world. The extensive dataset also reveals the presence of another so-called super-Earth in this alien solar system.

Sun-like star's 'oddball' planet   BBC - April 29, 2009
Astronomers have discovered a strange Jupiter-sized world circling a star similar to our own Sun. The planet has a highly unusual, elliptical orbit around its parent star. At its furthest point, the planet is about as far from its star as the Earth is from the Sun. But at its nearest, it is about 10 times closer to its star than Mercury is to the Sun, the team told the JENAM 2009 conference in Hertfordshire. The planet, HD80606b, makes its close approach every 111 days, according to the study. If an observer were to hover above the cloud tops of this world, they would see their parent star grow to 30 times the size that the Sun appears in our own sky. The team from University College London observed a transit, in which the strange world crossed in front of its parent star. The data gathered from this event provided the astronomers with the most precise data yet on the planet's size and density, its tilt and the eccentricity of its orbit.

First Exoplanet With CO2 Heats Up Hunt for Other Earths    National Geographic - December 8, 2008
The recent discovery of carbon dioxide in the atmosphere of a Jupiter-like planet 63 light-years away has some researchers excited that we may soon find habitable exoplanets - worlds circling other stars. This first discovery of the molecule on a far-flung planet, he said, is a step toward eventually finding biomarkers on smaller, more Earthlike worlds.

Discovering Fomalhaut b    NASA - November 14, 2008

Fomalhaut (sounds like "foam-a-lot") is a bright, young, star, a short 25 light-years from planet Earth in the direction of the constellation Piscis Austrinus. In this sharp composite from the Hubble Space Telescope, Fomalhaut's surrounding ring of dusty debris is imaged in detail, with overwhelming glare from the star masked by an occulting disk in the camera's coronagraph. Astronomers now identify, the tiny point of light in the small box at the right as a planet about 3 times the mass of Jupiter orbiting 10.7 billion miles from the star (almost 23 times the Sun-Jupiter distance). Designated Fomalhaut b, the massive planet probably shapes and maintains the ring's relatively sharp inner edge, while the ring itself is likely a larger, younger analog of our own Kuiper Belt - the solar system's outer reservoir of icy bodies. The Hubble data represent the first visible-light image of a planet circling another star.

Find Fomalhaut in the Celestial Sea   MSNBC - November 14, 2008

The star pattern that contains the brightest star of this watery fraternity is found in Piscis Austrinus, the Southern Fish. It is here that we find the most southerly of all the first magnitude stars visible from mid-northern latitudes and the one that is usually associated with these chilly autumn evenings is the bluish-white star Fomalhaut. This week, at around 7 p.m. local daylight time, you'll see Fomalhaut shining sedately, low almost due south above horizon. And just before midnight, it's dropping out of sight below the southwest horizon. In ancient Persia, star announced the arrival of autumn weather.

First Picture of Alien Planet Orbiting Sunlike Star? National Geographic - September 16, 2008

An image released today of a distant star and its potential planetary companion could go down in history as the first picture of a planet outside our solar system orbiting a sunlike star. The possible planet - a hot, young body (upper left) about eight times more massive than Jupiter - sits roughly 330 times as far from its host star as Earth is from the sun. The pair lies about 500 light-years from Earth.

Three "Super-Earths" Found Orbiting Sun-Like Star National Geographic - June 17, 2008

A trio of "super-Earths" have been found near a sun-like star, a team of European astronomers announced today. The planets orbiting the star HD 40307 which is 42 light-years away were found using an advanced "planet searcher" instrument at the European Southern Observatory in La Silla, Chile, the French and Swiss astronomers said.

Methane Detected on Distant Planet for First Time National Geographic - March 19, 2008

Methane has been detected in the atmosphere of a planet outside our solar system, the first time that an organic molecule has been found on a distant world. Studies of this carbon-bearing compound could shed light on the planet's formation and evolution.

Largest Known Planet Found, Has Density of Cork National Geographic - August 8, 2007

The biggest alien planet found so far is baffling scientists with properties that defy current scientific explanation. By all rights, TrES-4, a gas giant recently discovered about 1,400 light-years away in the constellation Hercules, shouldn't exist.

Distant Planets Could Have Plants of "Alien" Colors National Geographic - April 12, 2007

Scientists may be able to determine the color of extraterrestrial plant life while studying distant planets, according to a pair of new studies. Researchers have developed a way to analyze the light emitted by a given planet's parent star and determine how that light interacts with various chemicals in the planet's atmosphere.

First Sign of Water on Planet Outside Our System National Geographic - April 11, 2007
For the first time, astronomers have detected water in the atmosphere of a planet outside our solar system. Astronomer Travis Barman announced today that he has discovered water around planet HD209458b by combining theoretical models with observations from the Hubble Space Telescope. Scientists have predicted water vapor in the atmospheres of most planets orbiting other stars.

Future Space Telescopes Could Detect Earth Twin Science Daily - April 12, 2007

For the first time ever, NASA researchers have successfully demonstrated in the laboratory that a space telescope rigged with special masks and mirrors could snap a photo of an Earth-like planet orbiting a nearby star. This accomplishment marks a dramatic step forward for missions like the proposed Terrestrial Planet Finder, designed to hunt for an Earth twin that might harbor life.

Smallest extrasolar planet found BBC - June 13, 2005

Astronomers have detected the smallest extrasolar planet yet: a world about seven and a half times as massive as Earth, orbiting a star much like ours. All of the 150 or so exoplanets found orbiting normal stars are larger than Uranus, itself 15 times Earth's mass. The new find may be the first rocky world found around a star like our Sun. The newly discovered "super-Earth" orbits the star Gliese 876, located 15 light-years away in the direction of the constellation Aquarius.

First extrasolar planet seen BBC - March 2005

A European team claims to have obtained the first direct image of a planet beyond our own Solar System. The "extrasolar planet" is said to orbit a star called GQ Lup - thought to be like a young version of our Sun. Similar claims have been made in the past, but skeptical scientists believe the pictures merely show objects that share the same view in the sky.