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Vocapedia > Space > Earth-like planets, exoplanets





How NASA’s TESS Spacecraft Will Hunt Exoplanets

Video        NYT - Out There        The New York Times        16 April 2018


NASA’s TESS spacecraft will spend two years

searching the sky for nearby alien worlds.



















Life in the universe

The Economist    Aug. 8, 2015





Life in the universe

Video        The Economist        Aug. 8, 2015


Does life exist anywhere else in the universe?

And how did it get started?

Scientists are seeking the answers in the cosmos,

our solar system and right here on planet Earth.

















The Planet Hunter

NYT    13 May 2014





The Planet Hunter

Video    Profiles in Science    The New York Times    13 May 2014


Geoffrey Marcy of the University of California, Berkeley,

has discovered scores of alien worlds,

so-called exoplanets circling distant stars.


Produced by:

Sean Patrick Farrell, Chris Cascarano, Roopa Vasudevan and Sofia Perpetua


Read the story here: http://nyti.ms/1oLO5Ry

Watch more videos at: http://nytimes.com/video





















This artists impression

shows the planet orbiting the star Alpha Centauri B,

a member of the triple star system that is the closest to Earth.


Alpha Centauri B is the most brilliant object in the sky

and the other dazzling object is Alpha Centauri A.


Our own Sun is visible to the upper right.


The tiny signal of the planet

was found with the HARPS spectrograph

on the 3.6-metre telescope

at ESOs La Silla Observatory in Chile.



Artists impression of the planet around Alpha Centauri B

NASA > Planet quest

October 16, 2012






















































































planet        UK / USA





















































































free-floating planets        USA

— dark, isolated orbs

roaming the universe unfettered to any host star —










unseen planet        USA










newborn planet        UK










planetesimals        USA

- remnants of the formation of (a) planetary system










planet with three suns


HD 131399Ab,

located in the constellation of Centaurus        UK






planet hunter        USA






planetary scientists        USA






moons        USA






alien world        USA







































habitable > atmosphere / air        USA










watery atmosphere        USA










habitable zone / "Goldilocks" zone        USA


habitable zone

where the temperatures

are lukewarm

and suitable for liquid water

on the surface

















habitable planets        UK










habitable planets        USA












habitable exoplanets        USA

















planetoid        USA






dwarf planet        UK






gaseous planet        UK






gaseous planet >  KOI-314c        UK






gas giant > free-floating planet > PSO J318.5-22        UK






gas giant > Jupiter-like planet > Kepler-1647b


A gas giant 3,700 light years away

is the largest planet

yet to be found orbiting two stars,

scientists have revealed.


Dubbed Kepler-1647b,

the Jupiter-like planet

lies in the constellation Cygnus,

and was spotted by astronomers

examining data from the Kepler space telescope

- an instrument launched in 2009

to look for potentially habitable planets

beyond our solar system.


Not only is it the largest “circumbinary” planet,

it also has one of the longest orbits

ever recorded for a transiting planet,

taking 1,107 days to complete its circuit.








faraway gas giant planet > WASP-107b        USA


Discovered in 2017,

this planet orbits a star about 212 light-years away

that's a little smaller and cooler than the Sun.


The planet is so close to its star

that it orbits once every 5.7 days,

and temperatures there

reach around 900 degrees Fahrenheit.


Even though the planet is about the size of Jupiter,

it is much lighter, with about the same mass as Neptune.


Its low density led some scientists to call it

a "cotton candy" or "super puff" planet.






Monstrous rocky planet

nicknamed 'Godzilla of Earths'        UK        2 June 2014


The 'mega-Earth' Kepler-10

is the most massive rocky planet ever discovered

and its surface may be cool enough for life
















NASA > Planet quest - The search for another Earth









NASA's Kepler mission / spacecraft


launched in March 2009

on a three-and-a-half year mission

to monitor 150,000 stars

in a patch of sky in the Milky Way.




NASA's Kepler mission

has discovered

the first transiting circumbinary system

-- multiple planets orbiting two suns --

4,900 light-years from Earth,

in the constellation Cygnus,

proving that more than one planets

can form and survive in orbit

around a binary star.













there could be as many as

40 billion habitable Earth-size planets in the galaxy,

based on a new analysis of data

from NASA’s Kepler spacecraft.        November 4, 2013        UK / USA





















Mercury        USA


the smallest

of the inner planets

(4,880 km/3,032 mi

in diameter),

and the closest to the Sun

(58 million km/36 million mi

- or 3.2 light minutes).








Mercury        UK






Neptune        USA


Dark, cold and whipped

by supersonic winds,

Neptune is the last

of the hydrogen and helium gas giants

in our solar system.


More than 30 times

as far from the sun as Earth,

the planet takes

almost 165 Earth years

to orbit our sun.


In 2011

Neptune completed its first orbit

since its discovery in 1846.






Neptune's orbit





Earth-size planet        UK






Earth-size planet        USA












Earth-like planet        UK






earth-like        USA






Earth-like world > GJ 1132b        UK






planet > LkCa 15 b        UK







the first planet ever detected in the Milky Way

that was born outside our galaxy        UK






planet > Hat-P-1























exoplanets        UK

– worlds outside our solar system -

– planets orbiting stars beyond our Sun –












exoplanet        USA


any planet that is outside of our solar system















watch?v=AxSqMdEA5M8 - NYT - 16 April 2018







exoplanet > Kepler 22-b o        UK






exoplanet > Gliese 581g        USA






exoplanet > Wasp-12b        UK






exoplanet > 51 Pegasi b,

the first exoplanet ever discovered        USA






exoplanet > super-Earth-sized planet        USA






exoplanets > NASA’s TESS Spacecraft        USA

watch?v=AxSqMdEA5M8 - NYT - 16 April 2018















parent star        UK






planet-like objects / "ice dwarfs"        UK











planet hunting        USA






a new planet-hunting technique

called gravitational microlensing        UK


















An artist's impression of the surface of Kepler 452b.

It orbits its star, which is 1,400 light-years away, in 385 days.


Credit: Danielle Futselaar

SETI Institute


NASA Says Data Reveals an Earth-Like Planet, Kepler 452b


JULY 23, 2015
















Earth-like planet / world        UK













Earth-like planet > Kepler 452b        USA






Earth-like planet / OGLE-2005-BLG-390Lb        UK






harbour life        UK






at the outer edges of the planetary system





extrasolar planets        UK






extrasolar planets        USA






The planet Mercury

is the smallest of the inner planets

(4,880 km/3,032 mi in diameter),

and the closest to the Sun

(58 million km/36 million mi - or 3.2 light minutes).        USA

mercury_and_messenger.html - broken link





Mercury        UK






elliptical orbit

















This artists impression shows

the free-floating planet CFBDSIR J214947.2-040308.9.

This is the closest such object to the Solar System.

It does not orbit a star and hence does not shine by reflected light;

the faint glow it emits can only be detected in infrared light.


Here we see an artists impression of an infrared view of the object

with an image of the central parts of the Milky Way

from the VISTA infrared survey telescope in the background.


The object appears blueish in this near-infrared view

because much of the light at longer infrared wavelengths

is absorbed by methane and other molecules in the planet's atmosphere.


In visible light the object is so cool that it would only shine dimly

with a deep red colour when seen close-up.



Artists impression of the free-floating planet CFBDSIR J214947.2-040308.9

Nasa > Planet quest

November 14, 2012












Corpus of news articles


Space > Planets,


Earth-like planets, exoplanets




A Sultry World Is Found

Circling a Distant Star


December 17, 2009

The New York Times



Call it Sauna World.

Astronomers said Wednesday that they had discovered a planet composed mostly of water.

You would not want to live there. In addition to the heat — 400 degrees Fahrenheit on the ocean surface — the planet is probably cloaked in a crushingly dank and dark fog of superheated steam and other gases. But its discovery has encouraged a growing feeling among astronomers that they are on the verge of a breakthrough and getting closer to finding a planet something could live on.

“This probably is not habitable, but it didn’t miss the habitable zone by that much,” said David Charbonneau of the Harvard-Smithsonian Center for Astrophysics, who led the team that discovered the new planet and will reports its findings on Thursday in the journal Nature.

Geoffrey W. Marcy, a planet hunter from the University of California, Berkeley, wrote in an accompanying article in Nature that the new work provided “the most watertight evidence so far for a planet that is something like our own Earth, outside our solar system.”

Only 2.7 times the size of Earth and 6.6 times as massive, the new planet takes 38 hours to circle a dim red star, GJ 1214, in the constellation Ophiuchus — about 40 light-years from here. It is one of the lightest and smallest so-called extrasolar planets yet found, part of a growing class that are less than 10 times the mass of the Earth.

Dr. Charbonneau’s announcement capped a week in which the list of known planets, including these “super-Earths,” grew significantly.

An international team of astronomers using telescopes in Australia and Hawaii reported in one paper that they had found three planets, including a super-Earth, orbiting 61 Virginis, a star in the constellation Virgo that is almost a clone of the Sun. In a separate paper, they reported finding a planet somewhat larger than Jupiter at the star 23 Librae. It was the first time, they said, that a super-Earth had been found belonging to a star like the Sun; the other home stars have been dwarfs.

And in yet another paper, a subset of the same group reported finding a super-Earth and probably two bigger planets circling HD 1461, a star in Cetus.

Paul Butler of the Carnegie Institution of Washington, who was involved in all three papers, said astronomers thought that from one-third to one-half of all Sun-like stars harbor such super-Earths orbiting at scorching distances much closer than Mercury is to the Sun.

In the 15 years since the first extrasolar planet was found, more than 400 have been detected. The field is getting more intense as dedicated planet-hunting instruments like the Kepler satellite from the National Aeronautics and Space Administration, due to report a new batch next month, get into the game.

Alan P. Boss, a planetary theorist at the Carnegie Institution of Washington, said of the planet hunters, “Give them a couple more years and they’re going to knock your socks off.”

Dr. Charbonneau’s planet, only 1.3 million miles from its home star, is distinguished by its relative coolness. It bakes rather than roasts, a consequence of the dimness of GJ 1214, which puts out one three-hundredth the Sun’s energy. He and his colleagues had set out to search for planets around such stars, noting that they are more numerous and that it is easier to discern planets around them.

“There is no question,” Dr. Charbonneau wrote in an e-mail message, “that small stars provide us with the fastest track to looking for life outside the solar system.”

His planet-hunting equipment is a bank of eight telescopes called MEarth, pronounced “mirth,” on Mount Hopkins in Arizona. They are only 16 inches in diameter, no bigger than those that grace the backyard of many amateur astronomers. They monitor the light of 2,000 nearby stars, looking for the regular blips caused when a planets passes by, or transits.

In May, Zachory Berta, a first-year graduate student of Dr. Charbonneau’s, called the group’s attention to a series of blips in the Ophiuchus star that seemed to be happening every 1.6 days. If he was right, Mr. Berta said, the next transit would occur at 6 a.m. on May 13.

Dr. Charbonneau was in Washington later that day preparing for a State Department dinner when he got a group e-mail message that began: “We have a winner. Congrats Zach!”

From the drop in starlight, the astronomers could calculate the diameter of the Ophiuchus planet, known now as GJ 1214b. Then they used a sensitive spectrograph on a 3.6-meter telescope in Chile to measure its gravitational tug on the star, thus deriving the planet’s mass. Dr. Charbonneau and his colleagues, using those two numbers, could calculate the density of the planet.

It was only the second time the density of a super-Earth had been measured, offering a rare chance for comparative planetology. The first — CoRoT 7b, discovered last year by the European Corot satellite — turned out to be about as dense as the Earth, suggesting that it is mostly rock.

The new planet is slightly heavier but significantly larger than the earlier one, and it is only about one-third Earth’s density.

“What we probably have here is a water world,” said Dr. Charbonneau, explaining that there are three basic ingredients abundant enough to go into the recipe for a planet.

They are light gases like hydrogen and helium, rocks like iron and silicates and so-called volatile materials like water.

The best recipe for the new planet would be a world that is predominantly water, with small amounts of rock in a core tens of thousands of miles underwater, surrounded by a suffocating atmosphere. By comparison, Earth is 0.06 percent water.

Dr. Charbonneau said the weight of the new planet’s presumptive atmosphere that kept the water liquid rather than just boiling into space. If all such super-Earths have this type of atmosphere, he and his colleagues write in their paper, none of them is likely to harbor life. Astronomers would have to redouble their efforts to seek even smaller planets to find habitable environments.

Dr. Charbonneau acknowledged that a different recipe, with more rock and a very puffy atmosphere, would also fit the data. That is unlikely, he and other planet experts say, but the sauna world theory may be soon tested.

The planet is close enough to be studied directly by telescopes on or near Earth. Indeed, Dr. Charbonneau said his team had already applied for observing time on the Hubble Space Telescope.

“Our own TV signals,” he said, “have already passed this star.”

A Sultry World Is Found Circling a Distant Star,







Now in Sight: Far-Off Planets


November 14, 2008
The New York Times


A little more of the universe has been pried out of the shadows. Two groups of astronomers have taken the first pictures of what they say — and other astronomers agree — are most likely planets going around other stars.

The achievement, the result of years of effort on improved observational techniques and better data analysis, presages more such discoveries, the experts said, and will open the door to new investigations and discoveries of what planets are and how they came to be formed.

“It’s the tip of the iceberg,” said Christian Marois of the Herzberg Institute of Astrophysics in Victoria, British Columbia. “Now that we know they are there, there is going to be an explosion.”

Dr. Marois is the leader of a team that recorded three planets circling a star known as HR 8799 that is 130 light-years away in the constellation Pegasus. The other team, led by Paul Kalas of the University of California, Berkeley, found a planet orbiting the star Fomalhaut, only 25 light-years from Earth, in the constellation Piscis Austrinus.

In an interview by e-mail, Dr. Kalas said that when he finally confirmed his discovery last May, “I nearly had a heart attack.”

In scratchy telescope pictures released Thursday in Science Express, the online version of the journal Science, the planets appear as fuzzy dots that move slightly around their star from exposure to exposure. Astronomers who have seen the new images agreed that these looked like the real thing.

“I think Kepler himself would recognize these as planets orbiting a star following his laws of orbital motion,” Mark S. Marley of the Ames Research Center in Mountain View, Calif., wrote in an e-mail message elaborating on HR 8799.

More than 300 so-called extrasolar planets have been found circling distant stars, making their discovery the hottest and fastest-growing field in astronomy. But the observations have been made mostly indirectly, by dips in starlight as planets cross in front of their home star or by wobbles they induce going by it.

Astronomers being astronomers, they want to actually see these worlds, but a few recent claims of direct observations have been clouded by debates about whether the bodies were really planets or failed stars.

“Every extrasolar planet detected so far has been a wobble on a graph,” said Bruce Macintosh, an astrophysicist from Lawrence Livermore National Laboratory in California and a member of Dr. Marois’s team. “These are the first pictures of an entire system.”

The new planetary systems are anchored by young bright stars more massive than our own Sun and swaddled in large disks of dust, the raw material of worlds.

The three planets orbiting HR 8799 are roughly 10, 9 and 6 times the mass of Jupiter, and orbit their star in periods of 450, 180 and 100 years respectively, all counterclockwise.

The Fomalhaut planet is about three times as massive as Jupiter, according to Dr. Kalas’s calculations, and is on the inner edge of a huge band of dust, taking roughly 872 years to complete a revolution of its star.

Both systems appear to be scaled-up versions of our own solar system, with giant planets in the outer reaches, leaving plenty of room for smaller planets to lurk undetected in the warmer inner regions. Dust rings lie even farther out, like the Kuiper belt of icy debris extending beyond the orbit of Neptune.

“This is a window into what our own solar system might have looked like when it was 60 million years old,” Dr. Marois said.

Sara Seager, a planetary theorist at the Massachusetts Institute of Technology, said it was significant that the planets in both cases seemed to be associated with disks of dust, particularly Fomalhaut, one of the brightest and closest stars known to be host to a massive disk.

“Fomalhaut is like a Hollywood star to astronomers, so we have some personal excitement here,” Dr. Seager said. “It feels like finding out that one of your four closest friends just won the lottery big time”

Alan Boss, a planetary theorist at the Carnegie Institution of Washington, said the triple-planet system in Pegasus was particularly promising, “as we expect planets to form in systems in general, whereas spurious background interlopers will generally appear as single ‘planets.’ ” But he and others cautioned that much more study of these objects was necessary and that the masses imputed to them were still highly uncertain.

Being able to see planets directly opens the door to spectroscopic observations that can help determine the composition, temperature and other physical characteristics of planets and allow for comparisons with one another and with their parent stars. Dr. Macintosh said he hoped to train a spectroscope on his new planets as early as Monday.

The new images are the fruits of a long campaign by astronomers to see more and more of the unseeable. In particular, it is a triumph for the emerging technology of adaptive optics, in which telescope mirrors are jiggled and warped slightly many times a second to compensate for the atmospheric turbulence that blurs star images.

The problem in seeing other planets is picking them out of the glare of their parent stars, which are millions of times brighter, at least in visible light. As a result, planet hunters usually look for infrared, or heat radiation, which is emitted copiously by planets still shedding heat from the process of formation.

For their observations, Dr. Marois and his colleagues used the 8-meter in diameter Gemini North and the 10-meter Keck telescopes on Mauna Kea in Hawaii, both of which had been fitted with adaptive optics. Then they processed the images with a special computer program, which Dr. Marois described as “a software coronagraph,” for processing the images.

The team first spied a pair of dots about four billion and six billion miles out from HR 8799 in October last year. Following up, they discovered a third planet closer in, at about two billion miles. Then they discovered an old observation from 2004, which also showed the planets and how far they had moved around the star in three years.

“Seeing the orbit is one of the coolest things,” Dr. Macintosh said.

Dr. Kalas did his work with the Hubble Space Telescope, which is immune to turbulence because it is in space. He used a coronagraph to block light from the actual star.

He said he had been driven to look for a planet around Fomalhaut after Hubble photographs in October 2004 showed that a dust ring around the star had a suspiciously sharp inner edge, often a clue that the ring is being sculpted by the gravity of some body orbiting nearby.

A second set of Hubble observations, in July 2006, revealed a dot moving counterclockwise around the star. “I basically held my breath for three days until I could confirm the existence of Fomalhaut in all of my data,” Dr. Kalas recalled.

Fomalhaut is also a young star, about 200 million years old, and its dust ring extends 11 billion to 20 billion miles from its planet, Dr. Kalas said. In order not to disturb or roil the dust ring, Fomalhaut’s planet must be less than three Jupiter masses, well within regulation planet size, Dr. Kalas and his collaborators calculated.

A more detailed analysis, with another team member, Eugene Chiang of the University of California, Berkeley, as lead author will appear in the Astrophysical Journal, Dr. Kalas said.

In an e-mail message, Dr. Kalas pointed out that Fomalhaut was the closest exoplanet yet discovered, “close enough to contemplate sending spacecraft there.”

Now in Sight: Far-Off Planets, NYT, 14.11.2008,






Smaller Version of the Solar System

Is Discovered


February 15, 2008
The New York Times


Astronomers said Wednesday that they had found a miniature version of our own solar system 5,000 light-years across the galaxy — the first planetary system that really looks like our own, with outer giant planets and room for smaller inner planets.

“It looks like a scale model of our solar system,” said Scott Gaudi, an assistant professor of astronomy at Ohio State University. Dr. Gaudi led an international team of 69 professional and amateur astronomers who announced the discovery in a news conference with reporters.

Their results are being published Friday in the journal Science. The discovery, they said, means that our solar system may be more typical of planetary systems across the universe than had been thought.

In the newly discovered system, a planet about two-thirds of the mass of Jupiter and another about 90 percent of the mass of Saturn are orbiting a reddish star at about half the distances that Jupiter and Saturn circle our own Sun. The star is about half the mass of the Sun.

Neither of the two giant planets is a likely abode for life as we know it. But, Dr. Gaudi said, warm rocky planets — suitable for life — could exist undetected in the inner parts of the system.

“This could be a true solar system analogue,” he said.

Sara Seager, a theorist at the Massachusetts Institute of Technology who was not part of the team, said that “right now in exoplanets we are on an inexorable path to finding other Earths.” Dr. Seager praised the discovery as “a big step in finding out if our planetary system is alone.”

Since 1995, around 250 planets outside the solar system, or exoplanets, have been discovered. But few of them are in systems that even faintly resemble our own. In many cases, giant Jupiter-like planets are whizzing around in orbits smaller than that of Mercury. But are these typical of the universe?

Almost all of those planets were discovered by the so-called wobble method, in which astronomers measure the gravitational tug of planets on their parent star as they whir around it. This technique is most sensitive to massive planets close to their stars.

The new discovery was made by a different technique that favors planets more distant from their star. It is based on a trick of Einsteinian gravity called microlensing. If, in the ceaseless shifting of the stars, two of them should become almost perfectly aligned with Earth, the gravity of the nearer star can bend and magnify the light from the more distant one, causing it to get much brighter for a few days.

If the alignment is perfect, any big planets attending the nearer star will get into the act, adding their own little boosts to the more distant starlight.

That is exactly what started happening on March 28, 2006, when a star 5,000 light-years away in the constellation Scorpius began to pass in front of one 21,000 light-years more distant, causing it to flash. That was picked up by the Optical Gravitational Lensing Experiment, or Ogle, a worldwide collaboration of observers who keep watch for such events.

Ogle in turn immediately issued a worldwide call for continuous observations of what is now officially known as OGLE-2006-BLG-109. The next 10 days, as Andrew P. Gould, a professor of mathematical and physical sciences at Ohio State said, were “extremely frenetic.”

Among those who provided crucial data and appeared as lead authors of the paper in Science were a pair of amateur astronomers from Auckland, New Zealand, Jennie McCormick and Grant Christie, both members of a group called the Microlensing Follow-Up Network, or MicroFUN.

Somewhat to the experimenters’ surprise, by clever manipulation they were able to dig out of the data not just the masses of the interloper star and its two planets, but also rough approximations of their orbits, confirming the similarity to our own system. David P. Bennett, an assistant professor of astrophysics at the University of Notre Dame, said, “This event has taught us that we were able to learn more about these planets than we thought possible.”

As a result, microlensing is poised to become a major new tool in the planet hunter’s arsenal, “a new flavor of the month,” Dr. Seager said.

Only six planets, including the new ones, have been discovered by microlensing so far, and the Scorpius event being reported Friday is the first in which the alignment of the stars was close enough for astronomers to detect more than one planet at once. Their success at doing just that on their first try bodes well for the future, astronomers say.

Alan Boss, a theorist at the Carnegie Institution of Washington, said, “The fact that these are hard to detect by microlensing means there must be a good number of them — solar system analogues are not rare.”

Smaller Version of the Solar System Is Discovered, NYT, 15.2.2008,






Pictures Reveal

Mercury’s Tumultuous Past


January 31, 2008
The New York Times


WASHINGTON — The Messenger spacecraft that zipped past Mercury two weeks ago found more evidence of the innermost planet’s turbulent past, including ridges that run hundreds of miles and a unique feature made up of more than 100 troughs radiating in all directions, scientists said Wednesday.

A preliminary look at data from the flyby, including 1,213 images, shows a small, cratered planet that superficially looks like Earth’s moon but is very different in reality, they said.

The robot spacecraft, the first to visit the planet in more than three decades, passed 124 miles above Mercury’s surface on Jan. 14 before continuing on a path that is to bring it back three more times in the next three years before settling into orbit.

During the encounter, the Messenger’s seven scientific instruments scanned the planet, its magnetic field and its wispy atmosphere in great detail.

“Our little craft has returned a gold mine of exciting data,” said Dr. Sean C. Solomon of the Carnegie Institution of Washington, the mission’s lead investigator.

“We were continually surprised,” Dr. Solomon said at a NASA news conference. “It was not the planet we expected. It was not the moon.”

Mercury remains a very dynamic planet and is a key to understanding the evolution of the inner solar system and its four rocky planets, including Earth, he said.

NASA’s Mariner 10 spacecraft, which made three flybys of Mercury in 1974 and 1975, mapped about 45 percent of the planet’s surface. The Messenger craft took pictures of another 30 percent during its first visit and should complete the portrait when it returns on its next flyby in October, scientists said.

After that visit and another in September 2009 to slow the craft, the Messenger is to settle into orbit around Mercury on March 18, 2011, for at least a year of studies.

Among the features spotted by the Messenger — short for the $446 million mission’s formal name, Mercury Surface, Space Environment, Geochemistry and Ranging — is one informally called “the spider.” It appears to be an impact crater 25 miles in diameter from which more than 100 flat-bottomed troughs shoot out in all directions, said Louise Prockter, an imaging instrument scientist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md., which built and operates the spacecraft.

“It’s a real mystery, a very unexpected find,” Ms. Prockter said, unlike anything ever observed in the solar system. It is unclear if the impact crater caused the shattered-looking feature or came later, after the troughs formed for another reason, she said.

Pictures Reveal Mercury’s Tumultuous Past, NYT, 31.1.2008,






Scientists Discover

Planet Orbiting Star


November 7, 2007
Filed at 10:53 p.m. ET
The New York Times


LOS ANGELES (AP) -- A new planet was discovered orbiting a sun-like star 41 light years away, making it the first known planetary quintet outside our solar system, astronomers said Tuesday.

The newfound planet joins four others circling the nearby star 55 Cancri in the constellation Cancer. Although it resides in the star's so-called habitable zone, a place where liquid water and mild temperatures should exist, it is more like Saturn than Earth and therefore not likely to support life.

Still, scientists have not ruled out the possibility of finding an Earth-like planet within the system as technology improves.

''It's a system that appears to be packed with planets,'' said co-discoverer Debra Fischer, an astronomer at San Francisco State University.

Ranked fourth from 55 Cancri, the latest planet is about 45 times the mass of Earth and has an orbit of 260 days. It was detected after nearly two decades of observations by ground-based telescopes using the Doppler technique that measures a planet's stellar wobble.

The other planets in the 55 Cancri system were discovered between 1996 and 2004. The innermost planet is believed to resemble Neptune, while the most distant is thought to be Jupiter-like.

Scientists have detected about 250 exoplanets, or planets orbiting a star other than the sun. The 55 Cancri star holds the record for number of confirmed planets. Only one other star is known to have four planets, while several others have three or less.

''We can now say there are stars like the sun that have many worlds around them,'' said planetary scientist Jonathan Lunine of the University of Arizona, Tucson, who had no role in the discovery.

The research will appear in a future issue of the Astrophysical Journal. It was funded by NASA, the National Science Foundation and the University of California.

The latest discovery shows that our solar system is not unique, scientists said.

''When you look up into the night sky and see the twinkling lights of stars, you can imagine with certainty that they have their own complement of planets,'' said astronomer Geoff Marcy of the University of California, Berkeley, who was part
of the research.


On the Net:

NASA: http://www.nasa.gov

Scientists Discover Planet Orbiting Star, NYT, 7.11.2007,
http://www.nytimes.com/aponline/us/AP-Planetary-System.html - broken URL






A Planet? Maybe It’s a Star


August 4, 2006
The New York Times


A tiny star with a giant planet is further muddling astronomers’ notion of what a planet is. The planet is one of perhaps only two or three planets around other stars to be photographed directly, but it may be more like a star than a planet.

The tiny star, known as Oph1622, is so small that it never lighted up, a failed star known as a brown dwarf. Even among brown dwarfs, it is small, with a mass equal to 14 Jupiters, or about one-seventy-fifth that of the Sun.

In a paper published yesterday on the Web site of the journal Science, astronomers at the University of Toronto and the European Southern Observatory report that a photograph of Oph1622 also shows a planet about half as large as the star itself, with a mass equal to seven Jupiters.

The two are separated by 22 billion miles, or about six times the distance between the Sun and Pluto. Both are young, about a million years old. Astronomers refer to them both by a recently coined word, planemo (pronounced PLAN-uh-mo), short for planetary mass object — planet-size bodies that may or may not be planets.

“It really stands out as something quite unusual and intriguing,” said Ray Jayawardhana, a professor of astronomy at the University of Toronto and an author of the Science paper. “The Oph1622 pair adds to the rich diversity of worlds that have been discovered recently, a diversity that we couldn’t really have imagined barely a decade ago.”

Within the solar system, astronomers have been debating where to put the dividing line between planets and smaller clumps of rock and ice like comets and asteroids. The discovery of an object larger than Pluto in the outer solar system last year has rekindled debate on whether Pluto, by far the smallest among the current roster of nine planets, should be demoted.

Outside the solar system, the dividing line between planets and stars has also become blurry.

In the past decade astronomers have found 200 planets around other stars. Almost all of these have been indirectly detected from a slight shift in the frequency of a star’s light caused by the gravitational pull of a planet.

In 2004, astronomers reported the first direct sighting of a distant planet, with about the mass of five Jupiters, seen next to a brown dwarf known as 2M1207 about 230 light-years away in the constellation Hydra. Astronomers have since seen small, faint companions around a couple other stars, but are uncertain whether those companions are planets or brown dwarfs.

Oph1622, about 400 light-years from Earth, should add to the confusion. Dr. Jayawardhana said its companion had the mass of a planet but was born in the manner of stars.

Star systems form in two steps. First, a cloud of gas collapses under gravity into one, two and sometimes three stars. A disk of leftover gas and dust then coalesces into planets.

But it is impossible to roll the clock back millions or billions of years, and astronomers cannot conclusively say how some objects formed.

Brown dwarfs, by some definitions, have a mass greater than about 13 Jupiters, the minimum amount for fusion reactions involving a heavy form of hydrogen known as deuterium to begin. (The fusing of ordinary hydrogen requires much higher temperatures and much higher mass, about 75 times that of Jupiter. That is the upper mass limit for brown dwarfs.)

But some astronomers say that many brown dwarfs are embryonic stars that were ejected out of nascent star systems. Others say that brown dwarfs formed just like other stars, but from smaller gas clouds. Astronomers have also observed free-floating planet-size objects not in orbit around a star, and they debate whether these objects formed in the same way as stars or were ejected from other star systems.

Astronomers had thought it was impossible to form stars much smaller than the Sun, because the outward pressure of gas molecules bouncing around would keep small gas clouds from collapsing. “People used to think it’s hard to make stars this small,” said Paolo Padoan, a professor of physics at the University of California, San Diego.

But Oph1622’s planet could not have formed the usual planet way, Dr. Jayawardhana said. Most known planetary disks have only 1 percent to 2 percent as much mass as the parent star, and thus the disk rotating around Oph1622 would have been too small to produce a planet half as large as itself, he said.

Complex computer simulations by Dr. Padoan show that turbulence within the gas clouds can generate shock waves traveling a few thousand miles per hour that tear the clouds into smaller pieces and provide the necessary kick to overcome the outward pressure and cause the smaller clouds to collapse.

A Planet? Maybe It’s a Star,










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