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Click! Extrasolar planets catalog
Click! First possible optical images of extrasolar planets

Latest news:

July 15, 2018

Ross 128B, one of the nearest exoplanets to Earth, may be habitable:

A study was published last month in The Astrophysical Journal Letters indicates that Ross 128B, one of the nearest exoplanets to Earth, just 11 light-years away, may be habitable.

Lead author Diogo Souto, of the Observatório Nacional in Rio de Janeiro, Brazil, said:

"Although Ross 128b is not Earth's twin, and there is still much we don’t know about its potential geologic activity, we were able to strengthen the argument that it's a temperate planet that could potentially have liquid water on its surface."

Ross 128b was discovered last year, appearing to circle in the "habitable zone" of its host star, the range of distances where liquid water could exist on a planet's surface. Its star, Ross 128, is a red dwark, the planet completes one orbit every 9.9 Earth days. Initial estimates also indicated that Ross 128b has a minimum mass just 1.35 times that of Earth and therefore stands a good chance of being rocky just like Earth.

The researchers analyzed Ross 128b's parent star using the Sloan Digital Sky Survey's Apache Point Observatory Galactic Evolution Experiment (APOGEE), a spectroscopic instrument installed on a telescope in New Mexico.

The APOGEE data revealed the abundances of certain key elements in Ross 128:, such as carbon, oxygen, magnesium and iron. Because stars and their orbiting planets coalesce from the same massive cloud of raw materials, thes eelements are likely to be found on Ross 128b as well.

Ross 128's observed iron-to-magnesium ratio indicates that the planet's core is larger than that of Earth. The team determined that temperatures at or near the surface of the star are around 5,400 °F (3000 °C). This, along with Ross 128b's radius and orbital distance, allowed to estimate how much stellar energy the planet receives and therefore how hot it is likely to be. The result was that Ross 128b probably has an "equilibrium temperature" of about 70 °F (21 °C). Of course this also depends of the planets' atmosphere composition and thickness; which are still unknown.

April 19, 2017

A "Super-Earth" orbiting a nearby star found:

AFP in Paris announces on April 19, 2017, that astronomers reported the discovery of a "super-Earth" planet orbiting a nearby star "which may offer the most promising target yet in the search for life beyond the Solar System."

The discoverers team leader is Jason Dittmann of the Harvard Smithsonian Center for Astrophysics, and the discovery is published in the journal Nature.

Planet LHS 1140b orbits red dwarf star LHS 1140 in the constellation of Cetus, only 40 light years away, in only 25 days, at a distance from its star where the temperature is neither too hot not too cold for liquid water to exist.

Previous planets in this temperate zone have already been spotted, but LHS 1140b is exceptional because it is "not far", and almost edge-on from Earth, so astronomers were able to get frequent looks at its light signature.

Early measurements suggest it is about five billion years old, or about 500 million years more than the Earth, and has a diameter about 1.4 times the size of our planet. Its mass is around seven times bigger than Earth's, which means it is dense rhather than made of gas. The neighbouring "red dwarf" star seems benign and stable.

The next step, in the years to come, will be to measure if the planet has an atmosphere.

April 6, 2017

Atmosphere detected around super-Earth exoplanet:

An astronomers team detected an atmosphere around the super-Earth GJ 1132b. They used the 2.2-m ESO/MPG telescope in Chile to take images of the planet's host star, red dwarf GJ 1132, measuring the slight decrease in brightness as the planet and its atmosphere absorbed some of the starlight while in transit in front of the host star.

The study was conceived and the observations coordinated by Luigi Mancini, formerly of the Max Planck Institute for Astronomy (MPIA) now working at the University of Rome Tor Vergata. Additional MPIA team members were Paul Mollière and Thomas Henning.

This is the first detection of an atmosphere around a low-mass super-Earth, in terms of radius and mass the most Earth-like planet around which an atmosphere has yet been detected. It is a significant step on the path towards the detection of life on an exoplanet.

Source: John Southworth et al., "Detection of the Atmosphere of the 1.6Exoplanet GJ 1132 b2/em>", in The Astronomical Journal, 2017, DOI: 10.3847/1538-3881/aa6477 available at https://arxiv.org/abs/1612.02425

March 22, 2017

7 Earth-sized planets found around dim star TRAPPIST-1:

Scientists have discovered seven Earth-sized planets tightly packed around dim star TRAPPIST-1 so that their "years" lasts between 1.5 and 13 days. The number of planets and the radiation levels they receive from their star, make these worlds a miniature analogue of our own Solar System.

The excitement was so great that the discovery was announced with an article in Nature from lead author Michaël Gillon, and a NASA news conference. In the last two decades, about 3500 planets have been found orbiting stars beyond our Sun. The first three planets of TRAPPIST-1 were actually detected last year.

TRAPPIST-1 is a small ultracool dwarf star with a luminosity roughly 1/1000th that of the Sun. Three of the seven TRAPPIST-1 planets actually receive similar amounts of radiation from the star as Venus, Earth and Mars. The seven planets have radii between three quarters and one times that of the Earth.

So close to the star, the planets are likely in tidal lock, with one half permanently turned towards the star, resulting in perpetual day on one side and everlasting night on the other. The associated extremes of temperatures could evaporate all water and collapse the atmosphere if the planet's winds are unable to redistribute heat.

Slight elongations in the planets paths around the star would cause the pull from the star's gravity to strengthen and weaken during its year, flexing the planet like a stress ball and generating tidal heat. This occurs on three of Jupiter's largest moons, including Europa and Ganymede, and it allows subsurface liquid oceans to exist.

March 28, 2012

Exoplanets in habitable zone around red dwarves:

Xavier Monfils, of the Observatory of the Sciences of the Universe in Grenoble, France, published in Astronomy and Astrophysics magazine, that the majority of exoplanets resembling the Earth would be satellites of small stars, the red dwarves.

He states on the website of the French newspaper Le Monde: "Our observations mean that approximately 40% of all the red dwarves have a super-Earth in their orbits in their habitable zone, where liquid water can exist on the surface of planet." According to his statistical calculations there would be tens of billion of habitable planets similar to the Earth.

March 5, 2012


Astronomers had already located "wandering planets" in the galaxy, i.e. planets "floating freely" in interstellar space instead of orbiting around a star. Two explanations coexist about such planets: the most massive would have formed in the manner of brown dwarves, by gravitational accretion, of too small masses to become stars; the least massive would mainly originate from an ejection from during the formation of classical planetary systems.

By recent detection of wandering planet by gravitational lensing and other observations, a group of astrophysicians of the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) affirms that the number of wandering planets in our galaxy the Milky Way could be between 5 and... 100000 per star.

The team considers that sone of these free planets might have enough internal energy to maintain a long time tectonic activity and with an atmosphere, they might shelter bacterial forms of life well after their ejection of a planetary system. Fragments of these planets could propagate life in the Galaxy. They suggest they may be a vehicle for interstellar panspermy, pointing out that several comets of our own system were not probably born withing our own protoplanetary disc.

The article, however, is not published or not yet published in a professional journal, it was deposited on the Arxiv pre-publication website at http://arxiv.org/abs/1201.2687

February 6, 2012


On February 2, 2012, an international team of astronomers lead by Guillem Anglada-Escudé, at Carnegie Institution for Science in Washington D.C, reported the discovery of a fourth exoplanet located in the "habitable zone", neither too hot, nor too cold, rocky, which can have liquid water on its surface and thus arbor life.

This planet called GJ 667Cc is only approximately 50% more massive than the Earth, rotates around its star in 28 days approximately, and is at only 22 light-years from the Earth (our galaxy iss more than 100.000 light-year in diameter).

The same researchers say they have clues suggesting that at least another exoplanet and perhaps two, or even three others are in orbit around same star.

The discovery shows that habitable planets can form in a larger variety of environments than previously thought, the authors say. Their paper is to be published in the scientific journal The Astrophysical Journal Letters.

January 12, 2012


An AFP newsbrief relayed in other media such as "Le Monde" in France reports that there are "more planets than stars in our galaxy", according to a study published on January 11, 2012 by an international team of astronomers lead by Arnaud Cassan, of the Institute of Astrophysics of Paris, principal author of the article which appears in the British scientific journal Nature.

Stars surrounded by planets, are thus "the rule, rather than the exception" within the Milky Way, he summarizes.

According to statistical calculations by his team, there are on average 1,6 planet for each star in our galaxy. He specified: "Planets are all the more numerous as they are small."

According to the estimates of the study, 17 % of stars have a planet of a mass comparable with that of Jupiter, 52% have planets of the size of Neptune and 62% have "super-Earths", planets five to ten times more massive than the Earth.

His colleague Daniel Kubas indicates in an official statement of the European Southern Observatory (ESO), in Chile: "It seems that there are literally billion planets having masses similar to the Earth in orbit around stars in the Milky Way ".

Let me note that these statistics are done using the number of exoplants already detected, approximately 700 in the 16 last years, and it should go without saying that smallest are the harder to detect and that these statistics can still be re-calculated and become higher in the future.

For memory: there are at least 250 billion stars in our galaxy, the Milky Way, and they are perhaps more than 400 billion (There are hundreds of billion galaxies in the Universe). If each star indeed has 1.6 planets statistically, we get for our galaxy alone, from 400 000 000 000 to 850 000 000 000 planets.

June 15, 2010


The number of dicovered exoplanets was 461.

But about June 15, 2010, rumours coming from the scientific circles ensure that the team using the NASA's Kepler space telescope discovered nearly 706 others exoplanets in just a few months using the transit method, by detecting the regular weakening of the star light when planets pass between them and the telescope.

A group including the head scientist of the Kepler team, William Borucki, of the NASA Ames Research Center, put on line, on June 15, on the ArXiv prepublication system, a semi-official announcement giving a total of 706 candidates planets, and five stellar systems having two or three planets.

It is said that an official annoucement was to follow, while frustrated astronomers protest against the way in which the Kepler team does not readily share the data.

In fact, it is possible that among the 706 candidates, some are not planets, but dwarf stars, so small that they are only 10 to 15 times the size of Jupiter. There would be "only" 400 particularly promising candidates, those below the minimal dwarf star size, but there would be no information published on the matter before February 2011 because the team seeks confirmations by other observations.

William Borucki wishes a selective publication, to avoid a too hasty publication of data on candidates who would later prove disappointing or worse, non-existent.

June 11, 2010


Astronomers have directly imaged a gas giant planet orbiting Beta Pictoris, about 60 light-years from Earth. The discovery suggests such planet form very early after the star is born: Beta Pictoris, about 75 percent more massive than our sun, is only 12 million years old, making it less than three-thousandths of the age of the sun, so the planet must have formed in even less time.

October 22, 2009


Methane, carbon dioxide and water were detected by spectometry thanks to the Hubble and Spitzer space telescopes, on an already known exoplanet, HD 209458b. The exoplanet is out of the "habitable zone" around its star but the discovery, the second of the kind, shows that current instruments are able to locate such molecules on planets out of the solar system, and that these molecules, essential to life, are probably nothing exceptional, expectedly, as component of exoplants.

October 20, 2009


32 exoplanets ranging in mass from five times the mass of Earth to 5 to 10 times the mass of Jupiter were found using a very sensitive instrument on a 3.6m telescope at the European Southern Observatory's La Silla facility in Chile.

The discovery now takes the number of known exoplanets to more than 400.

Stephane Udry from Geneva University, Switzerland, said that from the results, "we know now that at least 40% of solar-type stars have low-mass planets. This is really important because it means that low-mass planets are everywhere, basically. What's very interesting is that models are predicting them, and we are finding them; and furthermore the models are predicting even more lower-mass planets like the Earth."

Planet detection techniques are working right at the limits of the current technology, so as time goes by and improvement are made, the smaller exoplanets are now detectable, whereas only the biggest exoplanets were be detected initially.

The goal now is to find a rocky, earth-like, planet in a star's "habitable zone", an orbit not too near and not to far from the star, where temperatures are in a range that would support the presence of liquid water. Scientists believe the introduction of newer, more sensitive technologies will allow them to identify such an object within just a few years from now.

September 16, 2009


Artie Hartzes, director of the Observatory of Thuringen, Germany, reports that he is the co-discoverer of an exoplanet whose mass is at most 5 times that of the earth. It is rocky, but so close to its star that the surface temperature must be near 2.000 degrees Celsius, much too hot to support life since the rocks must be melted.

The planet, called Corot-7b, circles its star in only 20 hours, at 750.000 km/h, and is at approximately 500 light years from our planet.

April 21, 2009


The discovery of the smallest exoplanet by team of Michel Mayor of the Observatory of Geneva in Switzerland using the HARPS instrument on the European Southern Observatory 3.6 meter telescope in La Silla, Chile was announced on 21 April 2009. It was detected using the radial velocity technique, in which the orbit size and mass of a planet are determined based on the small perturbations it induces in its parent star's orbit via gravity.

The planet, Gliese 581 e is the fourth extrasolar planet found around the star Gliese 581, a red dwarf star approximately 20 light-years away from Earth. At a minimum of 1.9 Earth masses, it is the smallest extrasolar planet discovered around a normal star so far, the closest in mass to Earth, though at an orbital distance of just 0.03 Astronomical Unit from its parent star it is well out of the habitable zone and unlikely to possess an atmosphere due to its high temperature, small size, and strong radiation from the star.

(Ref. Mayor et al. (2009). "The HARPS search for southern extra-solar planets, XVIII. An Earth-mass planet in the GJ 581 planetary system". Astronomy and Astrophysics. http://obswww.unige.ch/~udry/Gl581_preprint.pdf.

December 24, 2008


Carbon dioxide, one of the signs that suggests a planet may be able to support life was detected in the atmosphere of gas giant HD 189733b, a "hot Jupiter" planet orbiting a star 63 light years from the sun and Earth.

The planet is too large and too hot to harbour lifeforms such as Earth animals or humanoids: the detection is significant in terms of technological prowess, not in terms of actual detection of extraterrestrial lifeforms.

Source: www.nature.com/news/2008/081121/full/news.2008.1248.html

June 16, 2008


A trio of planets more massive than Earth but less massive than Uranus has been spotted orbiting the sun-like star HD 40307, 42 light-years away, astrophysicists announced today at the international conference in Nantes, France.

The smallest of the trio weighs about 4.2 Earth masses and orbits HD 40307 every 4.3 Earth days, the largest, with a mass 9.4 times that of Earth, has a 20.4-day orbit. The middleweight is 6.7 Earth masses and has a 9.6-day trek around the star.

Spotting Earth-sized planets and planets with longer orbits is not yet possible with current technology, but the presence of super-Earths suggests finding a world like ours is just a matter of time, said the researchers.

The team located the trio with the HARPS instrument on the European Southern Observatory's (ESO) 3.6-meter telescope at La Silla, Chile. The planets were detected by gravitational effects on the parent star's orbit, or radial velocity, or wobble, method.

In addition, HARPS astronomers have tallied about 45 new candidate planets with a mass below 30 Earth masses and an orbital period shorter than 50 days. The researchers say the deluge of newly found planets implies that at least one out of every three sun-like stars harbors such planets.

The team was lead by Michel Mayor of the Geneva Observatory in Switzerland, who, with Didier Queloz, discovered the first extrasolar planet, around the star 51 Pegasi, by the wobble method in 1995. He said: "We have made very precise measurements of the velocity of the star HD 40307 over the last five years, which clearly reveal the presence of three planets."

Most of the 270 extrasolar planets already found orbit solar-like stars, and most are gas giants called "hot-Jupiters", the easiest to find. The researchers say about one out of every 14 stars outside our solar system harbors a hot-Jupiter. Mayor said "It is obvious that this is only the tip of the iceberg."

A basketful of other new exoplanets also got the spotlight at the same international conference, where researchers focused on extra-solar super-Earths: a duo orbiting the star HD 181433: a super-Earth (7.5 Earth masses) that orbits its star every 9.5 days, and a Jupiter-like planet with a nearly three-year period, a 22 Earth-mass planet having a period of four days, and a Saturn-like planet with a three-year period.

Team member Stephane Udry, also of the Geneva Observatory, said: "It is most probable that there are many other planets present: not only super-Earth and Neptune-like planets with longer periods, but also Earth-like planets that we cannot detect yet. Add to it the Jupiter-like planets already known, and you may well arrive at the conclusion that planets are ubiquitous."

June 18, 2007


Scientists announced on April 22, 2007, that they had found a small planet located just far enough from its star to sustain liquid water on its surface, and thus possibly support life.

But better computer simulation showed that it is not the case, as planet Gliese 581c is actually probably too hot to support liquid water or life.

However and by chance, the new computer models also suggests that the conditions on its neighbor planet Gliese 581d might be just right.

These findings are detailed in the May 25 issue of the journal Astronomy and Astrophysics.

April 22, 2007



Potentially habitable planet found


For the first time astronomers have discovered a planet outside our solar system that is potentially habitable, with Earth-like temperatures, a find researchers described Tuesday as a big step in the search for "life in the universe."

The planet is just the right size, might have water in liquid form, and in galactic terms is relatively nearby at 120 trillion miles away. But the star it closely orbits, known as a "red dwarf," is much smaller, dimmer and cooler than our sun.

There's still a lot that is unknown about the new planet, which could be deemed inhospitable to life once more is known about it. And it's worth noting that scientists' requirements for habitability count Mars in that category: a size relatively similar to Earth's with temperatures that would permit liquid water. However, this is the first outside our solar system that meets those standards.

"It's a significant step on the way to finding possible life in the universe," said University of Geneva astronomer Michel Mayor, one of 11 European scientists on the team that found the planet. "It's a nice discovery. We still have a lot of questions."

The results of the discovery have not been published but have been submitted to the journal Astronomy and Astrophysics.

Alan Boss, who works at the Carnegie Institution of Washington where a U.S. team of astronomers competed in the hunt for an Earth-like planet, called it "a major milestone in this business."

The planet was discovered by the European Southern Observatory's telescope in La Silla, Chile, which has a special instrument that splits light to find wobbles in different wave lengths. Those wobbles can reveal the existence of other worlds.

What they revealed is a planet circling the red dwarf star, Gliese 581. Red dwarfs are low-energy, tiny stars that give off dim red light and last longer than stars like our sun. Until a few years ago, astronomers didn't consider these stars as possible hosts of planets that might sustain life.

The discovery of the new planet, named 581 c, is sure to fuel studies of planets circling similar dim stars. About 80 percent of the stars near Earth are red dwarfs.

The new planet is about five times heavier than Earth. Its discoverers aren't certain if it is rocky like Earth or if its a frozen ice ball with liquid water on the surface. If it is rocky like Earth, which is what the prevailing theory proposes, it has a diameter about 1 1/2 times bigger than our planet. If it is an iceball, as Mayor suggests, it would be even bigger.

Based on theory, 581 c should have an atmosphere, but what's in that atmosphere is still a mystery and if it's too thick that could make the planet's surface temperature too hot, Mayor said.

However, the research team believes the average temperature to be somewhere between 32 and 104 degrees and that set off celebrations among astronomers.

Until now, all 220 planets astronomers have found outside our solar system have had the "Goldilocks problem." They've been too hot, too cold or just plain too big and gaseous, like uninhabitable Jupiter.

[Webmaster note: The instruments could detect only large planets up to now. Gliese 581 also has such a large planet which already had been detected, Gliese 581 B, and still could have more planets.]

The new planet seems just right - or at least that's what scientists think.

"This could be very important," said NASA astrobiology expert Chris McKay, who was not part of the discovery team. "It doesn't mean there is life, but it means it's an Earth-like planet in terms of potential habitability."

Eventually astronomers will rack up discoveries of dozens, maybe even hundreds of planets considered habitable, the astronomers said. But this one - simply called "c" by its discoverers when they talk among themselves - will go down in cosmic history as No. 1.

Besides having the right temperature, the new planet is probably full of liquid water, hypothesizes Stephane Udry, the discovery team's lead author and another Geneva astronomer. But that is based on theory about how planets form, not on any evidence, he said.

"Liquid water is critical to life as we know it," co-author Xavier Delfosse of Grenoble University in France, said in a statement. "Because of its temperature and relative proximity, this planet will most probably be a very important target of the future space missions dedicated to the search for extraterrestrial life. On the treasure map of the Universe, one would be tempted to mark this planet with an X."

Other astronomers cautioned it's too early to tell whether there is water.

"You need more work to say it's got water or it doesn't have water," said retired NASA astronomer Steve Maran, press officer for the American Astronomical Society. "You wouldn't send a crew there assuming that when you get there, they'll have enough water to get back."

The new planet's star system is a mere 20.5 light years away, making Gliese 581 one of the 100 closest stars to Earth. It's so dim, you can't see it without a telescope, but it's somewhere in the constellation Libra, which is low in the southeastern sky during the midevening in the Northern Hemisphere.

"I expect there will be planets like Earth, but whether they have life is another question," said renowned astrophysicist Stephen Hawking in an interview with The Associated Press in Orlando. "We haven't been visited by little green men yet." [Really?]

Before you book your extrastellar flight to 581 c, a few caveats about how alien that world probably is: Anyone sitting on the planet would get heavier quickly [sic - would weigh more], and birthdays would add up fast since it orbits its star every 13 days [that's what made it easier do detect].

Gravity is 1.6 times as strong as Earth's so a 150-pound person would feel like 240 pounds.

But oh, the view. The planet is 14 times closer to the star it orbits. Udry figures the red dwarf star would hang in the sky at a size 20 times larger than our moon [or sun]. And it's likely, but still not known, that the planet doesn't rotate, so one side would always be sunlit and the other dark.

Distance is another problem. "We don't know how to get to those places in a human lifetime," Maran said.

Two teams of astronomers, one in Europe and one in the United States, have been racing to be the first to find a planet like 581 c outside the solar system.

The European team looked at 100 different stars using a tool called HARPS (High Accuracy Radial Velocity for Planetary Searcher) to find this one planet, said Xavier Bonfils of the Lisbon Observatory, one of the co-discoverers.

Much of the effort to find Earth-like planets has focused on stars like our sun with the challenge being to find a planet the right distance from the star it orbits. About 90 percent of the time, the European telescope focused its search more on sun-like stars, Udry said.

A few weeks before the European discovery earlier this month, a scientific paper in the journal Astrobiology theorized a few days that red dwarf stars were good candidates.

"Now we have the possibility to find many more," Bonfils said.

Source: The European Southern Observatory, April 22, 2007, at: http://www.eso.org/outreach/press-rel/pr-2007/pr-22-07.html (Note: this website has currently too much visitors and may not respond until the news is cold.)

March 29, 2007


NASA Jet Propulsion Laboratory communiqué:

NASA Telescope Finds Planets Thrive Around Stellar Twins

Whitney Clavin (818) 354-4673
Jet Propulsion Laboratory, Pasadena, Calif.
News Release: 2007-036
March 29, 2007

The double sunset that Luke Skywalker gazed upon in the film "Star Wars" might not be a fantasy.

Astronomers using NASA's Spitzer Space Telescope have observed that planetary systems - dusty disks of asteroids, comets and possibly planets - are at least as abundant in twin-star systems as they are in those, like our own, with only one star. Since more than half of all stars are twins, or binaries, the finding suggests the universe is packed with planets that have two suns. Sunsets on some of those worlds would resemble the ones on Luke Skywalker's planet, Tatooine, where two fiery balls dip below the horizon one by one.

"There appears to be no bias against having planetary system formation in binary systems," said David Trilling of the University of Arizona, Tucson, lead author of a new paper about the research appearing in the April 1 issue of the Astrophysical Journal. "There could be countless planets out there with two or more suns."

Previously, astronomers knew that planets could form in exceptionally wide binary systems, in which stars are 1,000 times farther apart than the distance between Earth and the sun, or 1,000 astronomical units. Of the approximately 200 planets discovered so far outside our solar system, about 50 orbit one member of a wide stellar duo.

The new Spitzer study focuses on binary stars that are a bit more snug, with separation distances between zero and 500 astronomical units. Until now, not much was known about whether the close proximity of stars like these might affect the growth of planets. Standard planet-hunting techniques generally don't work well with these stars, but, in 2005, a NASA-funded astronomer found evidence for a planet candidate in one such multiple-star system.


Trilling and his colleagues used Spitzer's infrared, heat-seeking eyes to look not for planets, but for dusty disks in double-star systems. These so-called debris disks are made up of asteroid-like bits of leftover rock that never made it into rocky planets. Their presence indicates that the process of building planets has occurred around a star, or stars, possibly resulting in intact, mature planets.

In the most comprehensive survey of its kind, the team looked for disks in 69 binary systems between about 50 and 200 light-years away from Earth. All of the stars are somewhat younger and more massive than our middle-aged sun. The data show that about 40 percent of the systems had disks, which is a bit higher than the frequency for a comparable sample of single stars. This means that planetary systems are at least as common around binary stars as they are around single stars.

In addition, the astronomers were shocked to find that disks were even more frequent (about 60 percent) around the tightest binaries in the study. These coziest of stellar companions are between zero and three astronomical units apart. Spitzer detected disks orbiting both members of the star pairs, rather than just one. Extra-tight star systems like these are where planets, if they are present, would experience Tatooine-like sunsets.

"We were very surprised to find that the tight group had more disks," said Trilling. "This could mean that planet formation favors tight binaries over single stars, but it could also mean tight binaries are just dustier. Future observations should provide a better answer."

The Spitzer data also reveal that not all binary systems are friendly places for planets to form. The telescope detected far fewer disks altogether in intermediately spaced binary systems, between three to 50 astronomical units apart. This implies that stars may have to be either very close to each other, or fairly far apart, for planets to arise.

"For a planet in a binary system, location is everything," said co-author Karl Stapelfeldt of NASA's Jet Propulsion Laboratory in Pasadena, Calif.

"Binary systems were largely ignored before," added Trilling. "They are more difficult to study, but they might be the most common sites for planet formation in our galaxy."

Other authors on the paper include: John Stansberry, George Rieke and Kate Su of the University of Arizona; Richard Gray of the Appalachian State University, Boone, N.C.; Chris Corbally of the Vatican Observatory, Tucson; Geoff Bryden, Andy Boden and Charles Beichman of JPL; and Christine Chen of the National Optical Astronomical Observatory, Tucson.

JPL manages Spitzer for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology, also in Pasadena. The multiband imaging photometer for Spitzer was built by Ball Aerospace Corporation, Boulder, Colo.; the University of Arizona; and Boeing North American, Canoga Park, Calif. Co-author Rieke is the principal investigator.

For more information and graphics, visit:

www.spitzer.caltech.edu/Media and http://www.nasa.gov/spitzer

More information about extrasolar planets and NASA's planet-finding program is at:


October 4, 2006


The Hubble space telescope has found 16 more extrasolar planets orbiting a variety of stars in the central region of the Milky Way, our galaxy. Those are additional to the current number of 208 extrasolar planets already found. This time, the planets are much farther away.

Extrapolated to the galaxy, the Hubble result provides strong evidence for the existence of at least 6 billion Jupiter-sized planets in the Milky Way. They were detected by oberving 2 to 15 transits each, i.e. the dimming of the star's light when the planet passes in front of it. Most have very short periods, ranging from 10 hours to 1 or 2 days; which makes them easier to be detected via the transit method.

To of the 16 newly found planets have already been confirmed by ESO's Very Large Telescope (VLT).
( www.eso.org/outreach/press-rel/pr-2006/pr-38-06.html and Nature, vol 443, p. 534. )

October, 2006


"Exotic Earths: Forming Habitable Worlds with Giant Planet Migration", September 2006, see:


"Close-in giant planets (e.g. "Hot Jupiters") are thought to form far from their host stars and migrate inward, through the terrestrial planet zone, via torques with a massive gaseous disk. Here we simulate terrestrial planet growth during and after giant planet migration. Several-Earth mass planets also form interior to the migrating Jovian planet, analogous to recently-discovered "Hot Earths". Very water-rich, Earth-mass planets form from surviving material outside the giant planet's orbit, often in the Habitable Zone and with low orbital eccentricities. More than a third of the known systems of giant planets may harbor Earth-like planets."

May 18, 2006


Three planets of Neptune mass have been discovered orbiting the nearby sun-like star HD 69830a, known to have an asteroid belt. This is the first discovery of a multiple system of three Neptune-mass planets, with periods of 8.67, 31.6 and 197 days, which would put them in the habitable zone. Theoretical calculations favor a mainly rocky composition for both inner planets. The outer planet probably has a significant gaseous envelope surrounding a rocky or icy core.

The discovery was published in this month's Nature scientific magazine in a paper by Christophe Lovis, Michel Mayor, Francesco Pepe, Yann Alibert, Willy Benz, François Bouchy, Alexandre C. M. Correia, Jacques Laskar, Christoph Mordasini, Didier Queloz, Nuno C. Santos, Stéphane Udry, Jean-Loup Bertaux and Jean-Pierre Sivan.

September 9, 2005


On September 9, 2005, astronomers using the NASA's Spitzer Space Telescope discovered that the star GM Aurigae, about 420 light-years away, 1 million years old and 1.05 times as massive as the Sun is surrounded by a protoplanetary disk of dust

The disk has a gap which was likely formed by one or more giant gas planets, quite similar to Jupiter and the other planets we're familiar with in the solar system.

New observations of a young star and its surroundings are like a snapshot of our own solar system when it was forming, astronomers announced, because the newly discovered gap extends roughly from the orbit of Jupiter to the orbit of Uranus.

The astronomers puzzled that large planets could form so quickly.

"GM Aurigae is essentially a much younger version of our Sun, and the gap in its disk is about the same size as the space occupied by our own giant planets," said Dan Watson, professor of physics and astronomy at the University of Rochester. "Looking at it is like looking at baby pictures of our Sun and outer solar system."

August 31, 2004


Donald Savage
Headquarters, Washington
(Phone: 202/358-1727)

August 31, 2004

Whitney Clavin
Jet Propulsion Laboratory, Pasadena, Calif.
(Phone: 818/354-4673)



Astronomers announced today the first discovery of a new class of planets beyond our solar system about 10 to 20 times the size of Earth - far smaller than any previously detected. The planets make up a new class of Neptune-sized extrasolar planets.

In addition, one of the new planets joins three others around the nearby star 55 Cancri to form the first known four-planet system.

The discoveries consist of two new planets. They were discovered by the world renowned planet-hunting team of Drs. Paul Butler and Geoffrey Marcy of the Carnegie Institute of Washington and University of California, Berkeley, respectively; and Barbara McArthur of the University of Texas, Austin. Both findings were peer-reviewed and accepted for future publication in the Astrophysical Journal. NASA and the National Science Foundation (NSF) funded the research.

"NASA, along with our partner NSF, is extremely proud of this significant planetary discovery," said Al Diaz, Associate Administrator of NASA's Science Mission Directorate. "The outcome of the tremendous work of the project scientists is a shining example of the value of space exploration."

"These Neptune-sized planets prove that Jupiter-sized, gas giants aren't the only planets out there," Marcy said. Butler added, "We are beginning to see smaller and smaller planets. Earth-like planets are the next destination."

Future NASA planet-hunting missions, including Kepler, the Space Interferometry Mission and the Terrestrial Planet Finder, will seek such Earth-like planets. Nearly 140 extrasolar planets have been discovered.

Both of the new planets stick very close to their parent stars, whipping around them in a matter of days. The first planet, discovered by Marcy and Butler, circles a small star called Gliese 436 about every two-and-one-half days at just a small fraction of the distance between Earth and the sun, or 4.1 million kilometers (2.6 million miles). This planet is only the second known to orbit an M dwarf, a type of low-mass star four-tenths the size of our own sun. Gliese 436 is located in our galactic backyard, 30 light-years away in the constellation Leo.

The second planet, found by McArthur, speeds around 55 Cancri in just under three days, also at a fraction of the distance between Earth and the sun, at approximately 5.6 million kilometers (3.5 million miles). Three larger planets also revolve around the star every 15, 44 and 4,520 days, respectively. Marcy and Butler discovered the outermost of these in 2002. It is still the only known Jupiter-like gas giant to reside as far away from its star as our own Jupiter. The 55 Cancri is about 5 billion years old, a bit lighter than the sun, and is located 41 light-years away in the constellation Cancer. "55 Cancri is a premier laboratory for the study of planetary system formation and evolution," McArthur said.

Because the new planets are smaller than Jupiter, it is possible they are made of rock, or rock and ice, rather than gas. According to the scientists, the planets may have, like Earth, formed through gradual accumulation of rocky bodies. "A planet of Neptune's size may not have enough mass to hold onto gas, but at this point we don't know," Butler said.

Both discoveries were made using the "radial velocity" technique, in which a planet's gravitational tug is detected by the wobble it produces in the parent star. Butler, Marcy and collaborators, including Dr. Deborah Fischer of San Francisco State University and Dr. Steven Vogt of the University of California, Santa Cruz, discovered their "Neptune" after careful observation of 950 nearby stars with the W.M. Keck Observatory in Mauna Kea, Hawaii. They were able to spot such a relatively small planet, because the star it tugs on is small and more susceptible to wobbling.

McArthur and collaborators Drs. Michael Endl, William Cochran and Fritz Benedict of the University of Texas discovered their "Neptune" after obtaining over 100 observations of 55 Cancri from the Hobby-Eberly Telescope at McDonald Observatory in West Texas. Combining this data with past data from Marcy, Fischer and Butler from the Lick Observatory in California, and archival data from NASA's Hubble Space Telescope, the team was able to model the orbit of 55 Cancri's outer planet. This, in turn, allowed them to clearly see the orbits of the other three inner planets, including the new Neptune-sized one.

For visuals depicting the new planets and information about NASA's planet-hunting missions on the Internet, visit:


August 28, 2004


NASA: Major extra-solar discovery announcement scheduled August 31, 2004

A NASA communiqué announces,

"[...] A team of planet-hunters will announce their discovery of a new class of planets beyond our solar system at a NASA Science Update at 1 p.m. EDT on Tuesday, August 31. Their discovery represents a significant and much-anticipated advance in the hunt for extra-solar planets. [...]"

The event will also be webcast live at: http://planetquest.jpl.nasa.gov/webcasts/ssu_0804.html

May 27, 2004


Raw Ingredients for Life Detected in Planetary Construction Zones

May 27, 2004

NASA has announced new findings from the Spitzer Space Telescope, including the discovery of significant amounts of icy organic materials sprinkled throughout several "planetary construction zones," or dusty planet-forming discs, which circle infant stars.

These materials, icy dust particles coated with water, methanol and carbon dioxide, may help explain the origin of icy planetoids like comets. Scientists believe these comets may have endowed Earth with some of its water and many of its biogenic, life-enabling materials.

Drs. Dan Watson and William Forrest of the University of Rochester, N.Y, identified the ices. They surveyed five very young stars in the constellation Taurus, 420 light-years from Earth. Previous studies identified similar organic materials in space, but this is the first time they were seen unambiguously in the dust making up planet-forming discs.

In another finding, Spitzer surveyed a group of young stars and found intriguing evidence that one of them may have the youngest planet detected. The observatory found a clearing in the disc around the star CoKu Tau 4. This might indicate an orbiting planet swept away the disc material, like a vacuum leaving a cleared trail on a dirty carpet. The new findings reveal the structure of the gap more clearly than ever before. Because CoKu Tau 4 is about one million years old, the possible planet would be even younger. As a comparison, Earth is approximately 4.5-billion years old.

"These early results show Spitzer will dramatically expand our understanding of how stars and planets form, which ultimately helps us understand our origins," said Dr. Michael Werner, Spitzer project scientist at NASA's Jet Propulsion Laboratory , Pasadena, Calif., which manages the mission.

Spitzer also discovered two of the farthest and faintest planet-forming discs ever observed. These discs surround two of more than 300 newborn stars uncovered for the first time in a stunning new image of the dusty stellar nursery called RCW 49. It is approximately 13,700 light-years from Earth in the constellation Centaurus.

"Preliminary data suggest that all 300 or more stars harbor discs, but so far we've only looked closely at two. Both were found to have discs," said Dr. Ed Churchwell of the University of Wisconsin, Madison, Wis., principal investigator of the RCW 49 research, with Dr. Barbara Whitney of Space Science Institute, Boulder, Colo.

Planet-forming, or "protoplanetary," discs are a natural phase in a star's life. A star is born inside a dense envelope of gas and dust. Within this envelope, and circling the star, is a flat, dusty disc, where planets are born.

"By seeing what's behind the dust, Spitzer has shown us star and planet formation is a very active process in our galaxy," Churchwell said.

Spitzer's exquisitely sensitive infrared eyes can see planet-forming discs in great detail. "Previously, scientists could study only a small sample of discs, but Spitzer is already on its way toward analyzing thousands of discs," Werner said.

Spitzer's infrared spectrograph instrument, which breaks apart infrared light to see the signatures of various chemicals, was used to observe the organic ices and the clearing within CoKu Tau 4's disc. Spitzer's infrared array camera found the new stars in RCW 49. Papers on the research will appear in the September 1 issue of the journal Astrophysical Journal Supplements. For images and information about the research on the Internet, visit: http://www.spitzer.caltech.edu/ and http://photojournal.jpl.nasa.gov

JPL manages the Spitzer Space Telescope mission for NASA's Office of Space Science, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology, Pasadena, Calif. JPL is a division of Caltech. Spitzer's infrared spectrograph was built by Cornell University, Ithaca, N.Y., and Ball Aerospace Corporation, Boulder, Colo. The instrument’s development was led by Dr. Jim Houck of Cornell. Spitzer's infrared array camera was built by NASA Goddard Space Flight Center, Greenbelt, Md. The camera's development was led by Dr. Giovanni Fazio of Smithsonian Astrophysical Observatory, Cambridge, Mass.

Whitney Clavin (818) 354-4673

Nancy Neal/Dwayne Brown (202) 358-1547/1726
NASA Headquarters, Washington


Source NASA - JPL, www.jpl.nasa.gov/releases/2004/133.cfm

July 3, 2003


Thursday in Paris at the "Extrasolar Planets: Today and Tomorrow" conference, researchers with the Anglo-Australian Telescope (AAT) in New South Wales, Australia have detected a large planet orbiting HD 70642, a sun-like star at 90 light-years from Earth in the Puppis constellation.

The newfound planet is about twice as massive as Jupiter and orbits its star from a distance of 3.3 AU, which would place it somewhere between Mars and Jupiter in our Solar System. It completes one orbit in six years.

These conditions around HD70642 are quite similar to our solar system. Thus it suggests that there may be a similar type of planetary systems around this star. So far, generally much larger extrasolar planets were found, orbiting quite near their star and at quite fast speed, although another extrasolar planet that might be smaller than Jupiter had already been found in 2001, around 47 Ursae Majoris.

"Pessimists" have interpreted this as a sign that earth-type planets may be extremely very rare. But of course large, fast and close to their star planets had much more chances to be detected than Jupiter-like planets as a result of the "wobble" detection method: a star "wobbles" more if there is a nearby fast and large planet. With the improvement of detection methods, I expect that more and more jupiter-like planet will now be detected, and over time, smaller earth like planet my be detected too.

9 January 2003


Astronomers from the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Massachussets, USA, announced they have detected the most distant extrasolar planet (OGLE-TR-56b) ever found in the constellation Sagittarius, located 5,000 light-years away.

They used the transit technique, now established as the most accurate tool available to astronomers today with the potential for finding Earth-like planets in the future.

4 December 2002


For the first time the mass of an extrasolar planet has been accurately measured. Gliese 876b is now known to weigh between 1.89 and 2.4 times as much as Jupiter. The result has been obtained using astrometry of the planet's trajectory, a different method than the wobble method, which is therefore validated.

29 November 2001


Regarding the news item underneath, I feel I need to add a precision.

Several media have titled this news item: "first exoplanet with an atmosphere discovered" instead of "first discovery of an atmosphere around an exoplanet."

The obvious difference is that in no case this discovery means that the other 80 or so extrasolar planet discovered so far have no atmosphere. They might have one also.

Nevertheless, it should be noted that the detection methods used for now are not precise enough yet to easily detect Earth sized planets. We are for now dealing with a giant planet, certainly not suitable for humanoid-like lifeforms.

28 November 2001


Astronomers announced today the first detection of an atmosphere around a planet orbiting another star, as they discovered a small amount of sodium above a large planet 150 light-years away.

More significant, the technique used in the investigation could eventually lead to the discovery of more interesting chemicals that might reveal the presence of extraterrestrial life. "For the first time, we can begin to chart the atmosphere around other planets," said Timothy Brown of the National Center for Atmospheric Research.

Brown worked with Caltech astronomer David Charbonneau, who led the study, which was detailed at a NASA press conference. The discovery was made using the Hubble Space Telescope. To optimize their precious telescope time, the researchers confined their search to sodium, an element they expect would exist around extrasolar planets, or exoplanets as astronomers call them. "Sodium is kind of like skunk scent," Brown explained in a telephone interview. "It's easy to detect, even if there's only a little bit of it there."

Several research groups have been pursuing a similar goal with ground-based telescopes, but none have made a firm detection, said Andrew Collier Cameron, an exoplanet hunter at the University of St. Andrews in Scotland.

The planet's atmosphere was examined during a transit over its star. The starlight changed as it was filtered through the planet's atmosphere. A spectrograph, broke the light into its component colors based on wavelength. Different elements and compounds created different light signatures. Though the star HD 209458 also has sodium in its outer layers, the astronomers noted a slight additional amount of sodium - less than 1% - as the starlight passed through the planet's atmosphere.

15 November 2001


Since the 6th October, 1995 several new planets orbiting other suns have been discovered and officially announced. Rather ironically in the sense of ufology, on the 20 September, 1996, a planet was discovered orbiting the star Zeta 2 Reticuli, a sunlike star from a double star system.

In 1961, Betty and Barney Hill were allegedly abducted by aliens and taken aboard their spacecraft. Their case has been widely publicized and was the first such case to receive worlwide attention, as it was the first case to be thoroughly investigated. During her abduction, Betty was shown a star map. She was asked by an alien to point out the Earth, but since Betty had no knowledge of astronomy, she couldn't reply. After her abduction, and under the controversial "hypnotic regression" method Betty Hill drew the star map as accurately as possible. A few years later, Marjorie Fish built a few models of star systems using plastic balls and wire.

One of these models matched Betty Hill's diagram. The star system from which Betty had allegedly been told the aliens originated from was Zeta 2 Reticuli.

The information about this found planet (zeta2 Ret 0.27(J) 0.14 18.9 (d) 0.) was allegedly removed from the Extra Solar Planets Encyclopaedia site after 4 days. The official reason was allegedly that "the data may have been misinterpreted and there probably is no planet." Fortunately, several person had saved the original version of the Encyclopaedia with the Zeta 2 Reticuli information still present.

My own modest attempt to find any trace of the allegedly discovered Zeta 2 Reticuli planet in the Extra Solar Planets Encyclopaedia listing and the few other listings yielded nothing so far.

However a visitor of my site looked better and wrote to me on 11.11.2001 that the saved missing information are copied on the MUFOR site at http://www.mufor.org/extrasol.html

15 October 2001


Eight new extrasolar planets, at least two of which have circular orbits reminiscent of the planets in our solar system have been detected. They orbit their stars at distances ranging from about 0.07 AU to 3 AU. (One AU, or astronomical unit, is the distance from Earth to the Sun.) They range in maximal mass from 0.8 to 10 times the mass of Jupiter, the largest planet in our solar system. The total of known planets outside our solar system reaches 80.

24 August 2001


An extrasolar planet that might be smaller than Jupiter has been found orbiting a star similar to our Sun. It's the second planet found around the star called 47 Ursae Majoris, creating a picture of a solar system that might be similar to ours and adding evidence to the idea that researchers eventually will find Earth-like planets. The star 47 Ursae Majoris is a yellow star similar to the Sun, estimated to be seven billion years old and located about 51 light-years from Earth, which is significantly close to us.

6 April 2001


The international team of astronomers from the Geneva Observatory and other research institutes discovered 11 new planetary companions to solar-type stars. The discoveries include a giant planet that circles its Sun-like central star in an orbit similar to Earth's and whose potential satellites could theoretically be "habitable."

The discovery also includes two new multi-planet systems. The masses of these new objects range from slightly less than, to about 10 times the mass of the planet Jupiter.

The new detections are based on measured velocity changes of the stars, performed with the CORALIE spectrometer on the Swiss 47-inch (1.2-meter) Leonard Euler telescope at the European Space Observatory's La Silla Observatory. Instruments on telescopes at the Haute-Provence Observatory in France and on the twin Keck telescopes on Mauna Kea, Hawaii were also used to verify the findings. Some of the new planets have unusual characteristics: one is a two-planet system revolving around the star HD 82943 that indicates one orbital period is nearly exactly twice as long as the other -- cases like this (referred to as "orbital resonance") are well known in our own solar system.

Another two-planet system around star HD 74156 has a Jupiter-like planet and a more massive planet farther out from the star.

They also discovered a planet (at star HD 80606) with the most elongated orbit detected so far, moving between a near point of 3.1 million and far point of 78.9 million miles (5 million and 127 million kilometers) from the central star.


8 May 2000Planet A around the pulsar 1257+12 confirmed [cannot be a heliospheric propagation artefact] (Wolszczan et al.)
4 May 20005 new planets at La Silla (Swiss 1.2-m Leonhard Euler telescope) [plus 2 brown dwarfs]
27 April 2000Two planets orbiting BD -10 3166 and HD 52265 (Butler et al.)
29 Mars 2000Two sub-Saturn mass planets around HD 16141 and HD 46375 by Marcy. Butler and Vogt.
19 Mars 2000Ball Aerospace, Lookheed Martin, SVS and TRW to conduct TPF architecture studies.
5 Mars 2000'Eddington': a space mission to detect Earth-like planetary transits (and stellar oscillations) pre-selected by ESA.
1995The 1st extrasolar planet is detected.
14 February 1999The 32nd planet candidate found around HD 12661 by the SFSU Team.
8 February 1999The 31st planet found by the AFOE Team around HD 89744
25 January 1999A planet found around GJ 3021 (Naef et al., with Coralie)
8 January 1999Michelson Summer School on Stellar Interferometry (with applications to planet detection)
10 December 1999The PLANET Team claims that Jupiter mass planets with separations of 1.5-3 AU occur in less than 1/3 of systems.
23 November 1999HD 209458:
- planet discovered independently by radial velocity by Elodie and Coralie Teams
- transit detected first by Charbonneau et al. (September 1999)
20 November 1999Possible detection of star light reflected from the planet tau Boo b (Cameron et al., to be confirmed)
15 November 1999Six new planets detected by Marcy et al: HD 209458, HD 37124, HD 177830, HD 134987, HD 222582, HD 10697
12 November 1999Meeting Computational Astrobiology for the 21st Century (November 18th)
5 November 1999Speculations about ` supercomets ' around W 3(OH) (Slysh et al.)
5 November 1999MACHO-97-BLG-41: Planet in binary star or binary rotation effect?
15 November 1999Observation of a planetary transit for HD 209458 (Henry et al.)
19 October 1999MACHO 97-BLG-41: the PLANET Team can explain the data as a rotating binary lens.
15 October 1999FAME (astrometric mission with a precision of 50 microarcsec) selected by NASA. Launch 2004.
12 October 1999Circumstellar disks found by Trilling et al. around the planetary systems rho CrB and HD 210277. (also searched for but not found around 51 Peg, ups And and Gliese 876).
1 October 1999UMBRAS: project for a coronographic space screen.
28 September 1999Planet around HD 192263 found by Santos et al. at Swiss telescope at La Silla discovered independently by Marcy et al.
17 September 1999Search for telluric extrasolar planets threatened by French ministry of research?
6 Septenber 19991 MJ planet announced by Swiss Team (Udry et al.)
2 September 1999The planet candidates of the summer: iota Hor = HR 810 by Kürster et al. (press release, no preprint; first preliminary announcement in July 1998) 97-BLG-41 by Bennet et al. (microlensing)
5 May 1999Short duration Macho event 99-BLG-23 ( ~ 1 day).Observations are URGENTLY requested.
2 May 1999Meeting on the ESA IRSI/Darwin project (Stockholm, 16 - 19 November 1999)
28 April 1999Serious doubts on planets around the pulsar PSR 0329+54 (Konacki et al.).
15 April 1999Three planets around upsilon Andromedae found by SFSU and AFOE groups.
12 April 1999Meeting on the ESA IRSI/Darwin project (Stockholm, october 5 - 8 1999)
6 April 1999From PLANET Team: High Magnification or Possible Caustic Crossing Event: OGLE 99-BLG-005.
1 April 1999Strong constraints on a substellar companion to the star Proxima Centauri (Kürster et al.,)
1 February 1999The lightest planet found around HD 75289 by Mayor et al.
15 January 1999Claimed Earth-mass planet revisited by PLANET team
11 January 1999Dust ring around HD 141569 seen by Hubble
30 Deceber 1998Microlensing event compatible with Earth-mass planet (S.H. Rhie et al., MPS collab.)
24 November 1998Planet found around the binary star Gl 86 by Swiss team at 1.2 m Swiss telescope at La Silla
24 November 1998Creation of an Extrasolar Planetary Foundation.
13 November 1998Five Discovery missions selected by NASA. No one about extrasolar planets.
4 November 1998NASA Ames to Host Astrobiology Meeting Nov. 5-7
22 September 1998A possible planet around the solar twin HD187123 (Butler, Marcy, Vogt & Apps)
24 September 1998A planet around the star HD 210277 (Marcy, Butler & Vogt)
12 October 1998Two more planets: HD 195019 and HD 217107 (Debra Fischer et al. at Lick and Keck)
14 October 1998To be announced soon: planet around HD 168443 (Marcy et al.)
22 October 1998Image of the circumstellar disk around 55 Cnc (Trilling & Brown)


What's the closest extrasolar planetary system? It may well be planets of the dim red dwarf star cataloged as Lalande 21185, a mere 8 light years distant. This star is too faint to be seen by the naked eye and its planets have not been imaged directly. Instead, their presence is inferred by a long series of telescopic observations, tracking the star as it wiggles and wobbles in mutual gravitational response to the masses of its orbiting planets. Our own planetary system would be detectable by such a technique. Using data obtained from frequent observations of this star over the last 50 years, University of Pittsburgh astronomer George Gatewood recently announced that much of Lalande 21185's wobble is most likely due to an unseen planet with approximately 90% of the mass of Jupiter and an orbital period of 5.8 years. His work also indicates that a second and possibly third planet of similar mass could well be present in the system. Massive planets orbiting a red dwarf star would be very different from the Earth-sized planet with rings and moons lit by a cool, dim sun.

Nevertheless, the existence of a planetary system so near our own suggests the intriguing possibility that planets are common in our galaxy.


"With this one, everything hangs together," said veteran extrasolar planet discoverer Marcy. "This is what we've been waiting for."

For the first time astronomers have observed the passage of an extrasolar planet across the disk of its star, confirming the existence of the planet and providing new insights about the distant world, scientists reported November 12.

The discovery of a planet around HD 209458, a Sun-like star 153 light-years from the Earth, began November 5 when astronomers Geoff Marcy, Paul Butler, and Steve Vogt detected a wobble in the star based on previous observations.

Such wobbles have been seen in about two dozen other stars and have been linked to the existence of planets orbiting them. Based on their data, Marcy and colleagues determined that the planet was about five-eighths the mass of Jupiter and orbited very close to its parent star, completing one orbit every 3.5 days.

They passed on their findings to another astronomer, Greg Henry of the Tennessee State University Center of Excellence in Information Systems. Henry operates a series of automated telescopes at Fairborn Observatory in southern Arizona, and looks for possible transits by extrasolar planets, when the planets pass directly in front of the star as seen from Earth.

No such transits have been observed with any previously-discovered extrasolar planets. However, on November 7, at the time predicted by Marcy and colleagues using their data, Henry's telescope detected a 1.7 percent dip in the star's brightness, which Henry and Marcy interpret as the shadow cast by the passing planet.

"This planetary transit occurred at exactly the time predicted from Marcy's observations, confirming absolutely the presence of a companion," Henry said. "We've essentially seen the shadow of the planet."

With a period of 3.523 days, Henry plans to attempt to observe the next transit, on the night of November 14. In addition, they have asked astronomers to attempt to observe that transit was well as ones scheduled for November 18 and November 22.

By combining Marcy's radial-velocity data with Henry's transit data, the astronomers have learned more about this extrasolar planet than they know about most others. The dimming of the light from the transit indicates that the planet has a diameter 60 percent greater than Jupiter. That size, combined with the mass from the radial-velocity data, gives the planet a density of just 0.21 grams per cubic centimeter, one-fifth that of liquid water.

That density means the planet is a gas giant like Jupiter. However, the planet is just 5.25 million km (3.25 million mi.) from the star. Current theories of planet formation don't allow gas giants to form so close to their parent stars because of the high temperatures.

Because a number of such large planets have been discovered very close to their parent stars, theorists have worked on theories to explain how planets could form farther from the Sun and migrate inward. "This supports the theory that extrasolar planets very near their star did not form where they are, but formed farther out and migrated inward," Henry said.

The use of two separate techniques to discover the planet also helps to erase any remaining doubts that the radial velocity variations now seen in more than two-dozen stars is caused by anything other than orbiting planets.

"This is the first independent confirmation of a planet discovered through changes in a star's radial velocity and demonstrates that our indirect evidence for planets really is due to planets," said Marcy. "With this one, everything hangs together. This is what we've been waiting for."

Lost in the announcement about the dual discovery of this planet is the recent discovery of five other extrasolar planets by Marcy and colleagues, all using the radial velocity technique. These five other planets are all more massive and distant than the one orbiting HD 209458, with masses from 1 to 6.6 times the mass of Jupiter and distances from their stars of 0.58 to 2 astronomical units.

Efforts to discover planets by looking for brief dimming in stars caused by transits have been ongoing for some time, but have not been successful until now. A group at NASA proposed a dedicated mission, Kepler, that would monitor 100,000 stars simultaneously to look for any transits. That mission has not been funded by the space agency, however.



This false-colour image of the young Trapezium star cluster in the Orion Nebula was made with an infrared camera at wavelengths about twice as long as visible light. The infrared data are part of a sensitive survey of this nearby star forming region in which astronomers have identified over 100 extremely low mass objects, candidates for elusive brown dwarf stars. Brown dwarfs are failed stars with masses so low (about 8% of the Sun's) that they can not sustain nuclear hydrogen burning, a sun-like star's main energy source. While brown dwarfs are thought to be still massive enough to burn deuterium for energy, thirteen of the low mass objects show evidence of lying below even the deuterium burning limit (about 1.3% of the Sun's mass) falling in a range more commensurate with giant planets. These drifting, "free-floating planets" are perhaps as little as 8 times as massive as Jupiter and likely formed along with the cluster stars a million or so years ago. They are detectable in the infrared because they are still hot from formation, but will eventually cool and fade. If the Trapezium is typical of young star clusters, then the survey results suggest that brown dwarfs and free-floating planets may be fairly common, but there are not enough to solve the mystery of dark matter in the Universe.



Gliese 876 is smaller than the Sun, only about 1/3 as massive, and too faint to be seen without a telescope. But it is known to be one of the nearest stars, only 15 light-years distant. Astronomers have just announced findings that imply Gliese 876 has a planet at least 1.6 times as massive as Jupiter - making this now one of the closest suspected planetary systems. Like many recent discoveries, this planet's detection is not based on direct imaging but on spectroscopic measurements of the periodic change in motion or "Doppler wobble" produced in the parent star as the planet orbits. The Doppler wobble of Gliese 876 indicates that its planet orbits once every 61 days at an average distance of about 1/5 the radius of the Earth's orbit.


These near-infrared Hubble images of dust surrounding young stars offer the latest tantalizing evidence for planets beyond our Solar System. At left, the dark gap seen in the dust disk is reminiscent of a similar large gap in Saturn's rings believed to be sculpted by orbiting moons. By analogy, the gap in the dust disk of HD 141569 may be a larger scale result of unseen orbiting planets. At right is a relatively thin stellar dust ring suggestive of planetary rings held in place by orbiting moons. On a much larger scale this ring around the star HR 4796A could also indicate the presence of orbiting planet-sized bodies too faint to be directly visible. For a distance comparison, the orbit of Neptune is drawn at the lower right of each picture. The overwhelmingly bright starlight at the center has been blocked out to reveal the dim dust features.

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