Topic: extrasolar planet news

[Astronuc]

HAT-P-1 - Puffy planet poses pretty puzzle
http://news.bbc.co.uk/2/hi/science/nature/5346998.stm

Astronomers have found a strange new world that has them pondering again the essential properties of a planet.

This new object, designated HAT-P-1, orbits one member of a pair of stars 450 light-years away in the constellation Lacerta.

Although HAT-P-1's radius is about 1.38 times that of our own Jupiter, it has a mass that is only half that of Jupiter.

This makes it much bigger and lower in density than planets are usually, raising questions about how it formed.

The mathematical equations describing planetary structure do not fit.

HAT-P-1 is the largest of the 200 or so planets that have been detected outside our Solar System.

Like many of these extrasolar bodies, it orbits close to its parent star, revolving around it in just once every 4.5 Earth days.

Scientists know of one other extrasolar planet, HD 209458b, which is also puffed up about 20% bigger than predicted by theory. HAT-P-1 is 24% larger than expected.

http://www.cfa.harvard.edu/press/pr0624.html

http://arxiv.org/abs/astro-ph/0609369

[Astronuc]

Planets have scientists buzzing
http://news.bbc.co.uk/2/hi/science/nature/5378562.stm

A new wide-field survey of the sky has made its first major discovery - two planets orbiting far-distant stars.

The SuperWasp project uses camera lenses and super-sensitive detectors to monitor stars for tiny dips in light that might betray a passing planet.

The UK-led project identified a number of "suspects" and then handed the data to a French observatory for checking.

It used an instrument to analyse the light from the stars in detail and confirm the presence of the planets.

"To get these two we had to survey about 1.1 million stars and then go though several stages of filtering. It's a bit like panning for gold," Professor Andrew Collier Cameron from the University of St Andrews told BBC News.

The two extrasolar (outside our Solar System) planets, now known as Wasp-1b and Wasp-2b, are in the constellations of Andromeda and Delphinus.

Very hot

One is about 1,000 light-years from Earth; the other is about half that distance.

They are what astronomers term "hot Jupiters" - very large planets like the gas giants in our own Solar System but orbiting much closer in to their parent stars.

Whilst our Jupiter is almost 700 million km from the Sun and takes some 12 years to complete an orbit, these planets are just a few million km from their stars and take only a couple of days to complete an orbit.

This makes them extremely hot. Indeed, scientists think that of the 200 or so extrasolar planets detected to date, these may be among the hottest of the lot. Wasp-1b's temperature is estimated to be over 1,800C (3,300F).

SuperWasp (Wide Angle Search for Planets) is a new programme that puts eight lenses and top-quality CCD cameras on a robotic mount.

There are two set-ups: one is at La Palma observatory in the Canary Islands; the other is at the Sutherland Observatory in South Africa. Together they sweep the entire sky.

 

SuperWASP
Wide Angle Search for Planets
http://www.superwasp.org/

[Orstio]

This tally is consistent with the number of planets expected to be uncovered from such a distant survey, based on previous exoplanet detections made in our local solar neighbourhood that only encompasses six percent of the Milky Way’s disk. Extrapolated to the entire galaxy, the Hubble result provides strong evidence for the existence of about 6 billion Jupiter-sized planets in the Milky Way.

Five of the newly discovered planets represent a new extreme type of planet not yet found in any nearby searches. Dubbed Ultra-Short-Period Planets (USPPs), these worlds whirl around their stars in less than a day. The shortest-duration orbit is just 10 hours.

The planet bonanza was uncovered during an international Hubble survey, called the Sagittarius Window Eclipsing Extrasolar Planet Search (SWEEPS). Hubble looked at 180,000 stars in the crowded central bulge of our galaxy. Hubble’s narrow view covered a swath of sky that is no bigger in angular size than 2 percent the area of the full Moon. The results will appear in the Oct. 5 issue of the journal Nature.

"Discovering the very short-period planets was a big surprise," said team leader Kailash Sahu of the Space Telescope Science Institute in Baltimore, USA. "Only the Hubble Space Telescope, with its superb resolution and sensitivity, can look across our galaxy and find planets around faint stars. Our discovery also gives very strong evidence that planets are as abundant in other parts of the galaxy as they are in our solar neighbourhood."

Hubble couldn’t view the 16 newly found planet candidates directly. Instead, astronomers used Hubble’s Advanced Camera for Surveys to search for planets by measuring the slight dimming of a star due to the passage of a planet in front of it. This event is called a transit. The planet would have to be about the size of Jupiter to block enough starlight, about 1 percent to 10 percent, to be measurable by Hubble. These planets are called "candidates" because astronomers only have mass measurements for two of them.

Nevertheless, following an exhaustive analysis, the team ruled out alternative explanations such as a grazing transit by a stellar companion that could mimic the predicted signature of a true planet. The finding could more than double the number of planets spied with the transit technique.

The planet candidate with the shortest orbital period, named SWEEPS-10, swings around its star in 10 hours. Located only 1.2 million kilometres from its star (roughly three times the distance between the Earth and the Moon), the planet is among the hottest ever detected, with an estimated temperature of about 1650 degrees C. "This star-hugging planet must be at least 1.6 times the mass of Jupiter, otherwise the star’s gravitational muscle would pull the planet apart," said Sahu.

How can a planet survive the scorching temperatures so close to a star? Sahu said that the star’s low temperature allows the planet to exist. "USPPs occur preferentially around normal red dwarf stars that are smaller and cooler than our Sun," Sahu explained. He cites the apparent absence of USPPs around sun-like stars in our local neighbourhood as evidence that they must have evaporated away when they migrated too close in to a hotter star.

There is an alternative reason why Jovian planets around cooler stars may migrate in closer to the star, than for hotter stars. That’s because the circumstellar disk out of which they formed extends closer to a cooler star. Ever since the discovery of the first "hot Jupiter" in 1995, astronomers have realized that this unusual type of massive planet must have spiralled in close to its parent star from a more distant location where it only could have originally formed. The inner edge of a circumstellar disk halts the migration.

Sahu and his team also found that all of the planet candidates revolve around stars abundant in elements heavier than hydrogen and helium, such as carbon. This bolsters theories that heavy-element-rich stars have the necessary ingredients to form planets.

Planetary transits only occur when the planet’s orbit is viewed nearly edge-on. However, only about 10 percent of hot Jupiters have edge-on orbits that allow the planet to be observed transiting a star. To be successful, transit surveys must view a large number of stars at once. The SWEEPS transit survey covered a rich field of stars in the Sagittarius Window (the term "window" implies a clear view into the Galactic Centre, much of the Galactic Plane is obscured by dust). Hubble monitored 180,000 stars for periodic, brief dimming in a star’s brightness. The starfield was observed over a continuous seven-day period 23 to 29 February, 2004. To ensure that the dimming was caused by an object orbiting a star, the team used Hubble to detect from 2 to 15 consecutive transits for each of the 16 planet candidates.

Two of the stars in the field are bright enough that the SWEEPS team could make an independent confirmation of a planet's presence by spectroscopically measuring a slight wobble in the star’s motion due to the gravitational pull of an unseen companion. They used the European Southern Observatory's Very Large Telescope, located on Cerro Paranal in Chile, to measure a slight wobble in the star. One of the planetary candidates had a mass below the detection limit of 3.8 Jupiter masses. The other candidate is 9.7 Jupiter masses, which is below the cutoff mass for a brown dwarf (a substellar object that forms like a star but does not shine by nuclear fusion) of 13 Jupiter masses.

"Because the stars are so faint and the field of view is so densely packed with stars, it is not feasible to use this radial-velocity method to confirm most of our planet candidates. We may have to wait for the NASA/ESA/CSA James Webb Space Telescope which could provide the needed sensitivity to confirm most of the planet candidates," Sahu said.

The Hubble SWEEPS program is an important proof-of concept for CNES’s COROT mission scheduled for launch in December 2006 and NASA’s Kepler Mission, scheduled for launch in October 2008. COROT and Kepler will continuously monitor regions of the Milky Way galaxy to detect transiting planets. They will be sensitive enough to detect possibly hundreds of Earth-sized planet candidates in or near the habitable zone around a star. The habitable zone encompasses the distances from a star where liquid water can exist on a planet’s surface. As with the SWEEPS program, the COROT and Kepler detections will remain candidate planets until they can be independently verified by observations that would provide an independent estimate of planetary masses.

[Astronuc]

Water Mysteriously Absent from Extrasolar Planets' Atmospheres
 
Contrary to predictions, two planets orbiting distant stars show no signs of water and other simple compounds; dark clouds or haze may hide them

For the first time, telescopes have captured the light spectra emitted directly from planets outside of our solar system. Researchers trained the infrared-sensitive Spitzer Space Telescope on two extrasolar gas giant planets, called HD 209458 b and HD 189733 b.

The atmospheres are most notable for what they lack: "We find no evidence for water in the spectrum, and all the theorists will tell you that there should be water (in the form of vapor) in the atmosphere(s) of these planets," says astrophysicist Jeremy Richardson of the NASA Goddard Space Flight Center, a member of a team that analyzed HD 209458 b. A second group measured the spectrum of HD 189733 b, which is about 60 light-years away, and a third one reanalyzed the data from the former, which resides in the constellation Pegasus, more than 150 light-years distant.

 

I was wondering why it is considered mysterious.  If the planet was close to its star, e.g. closer than Venus is to the Sun, then it shoudn't be a mystery - should it?

[Astronuc]

http://en.wikipedia.org/wiki/HD_209458_b

HD 209458 b is an extrasolar planet that orbits the Sun-like star HD 209458 in the constellation Pegasus, some 150 light-years from Earth's solar system. HD 209458 is an 8th magnitude star, visible from Earth with binoculars.

HD 209458 b was the first transiting extrasolar planet discovered, the first extrasolar planet known to have an atmosphere, the first extrasolar planet observed to have an evaporating hydrogen atmosphere, the first extrasolar planet found to have an atmosphere containing oxygen and carbon, and one of the first two extrasolar planets to be directly spectroscopically observed. It is also the first extrasolar planet found to have water vapor in its atmosphere.

. . . .

On February 21, 2007, NASA and Nature released news that HD 209458 b was one of the first two extrasolar planets to have their spectra directly observed, the other one being HD 189733b.

. . . .

On April 10, 2007, Travis Barman of the Lowell Observatory announced evidence that the atmosphere of HD 209458 b contained water vapor. Using a combination of previously published Hubble Space Telescope measurements and new theoretical models, Barman found strong evidence for water absorption in the planet's atmosphere.

A spectrum of an extrasolar planet

Identification of Absorption Features in an Extrasolar Planet Atmosphere

[Astronuc]

A few BBC articles on extra solar planets can be found at -

Planet hunters find 'super-Earth'
http://news.bbc.co.uk/1/hi/sci/tech/4801842.stm


International astronomers suspect it is a bare, icy, rocky world, much colder than the Earth and 13 times its mass.

The planet was spotted last April but details have only just been revealed in a paper submitted to Astrophysical Journal Letters.

The extra-solar planet is one of a mere handful detected using a novel technique called microlensing.

The planet orbits a star about half as big as our Sun, positioned some 9,000 light-years away. At -201°C, it is one of the coldest extra-solar planets to be discovered.

Smallest Earth-like planet found  (that was until Gliese 581c was found - and much closer too!)
http://news.bbc.co.uk/1/hi/sci/tech/4647142.stm
The new planet has five times the Earth's mass and can be found about 25,000 light-years away in the Milky Way, orbiting a red dwarf star.

[Sarah90]

Am confused.  Is this same one?
 'Goldilocks' planet may be just right for life
00:01 25 April 2007
NewScientist.com news service
Hazel Muir

A planet about five times as massive as Earth orbits in the habitable zone around a lightweight red dwarf star called Gliese 581, which also appears to host two other planets. If you could stand on the small planet's surface, you would see its host star looming 10 times wider in the sky than our own Sun appears (Illustration: ESO)Related ArticlesDanger zones mapped for developing planets
18 April 2007
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11 April 2007
First sign of water found on an alien world
10 April 2007
Search New Scientist
Contact us
Web LinksPlanet search and stellar kinematics, Geneva Observatory
European Southern Observatory
PlanetQuest, NASA
  For the first time, astronomers have spotted a cosy alien planet that might be hospitable to life. The planet is not much bigger than the Earth, and it enjoys balmy temperatures of about 20° C (68° F) as well as spectacular scarlet sunsets.
"It's the smallest, lightest planet known at this time," says Stéphane Udry from the Geneva Observatory in Switzerland. "And it's just at the right distance from its star for liquid water to possibly exist on its surface."
Udry and colleagues discovered the planet using the European Southern Observatory's 3.6-metre telescope in Chile. They monitored a small, dim "red dwarf" star called Gliese 581, which lies 20.5 light years away, and is already known to have a Neptune-class planet.
Subtle "wobbles" of the star suggested that it has two additional planets. One is about eight times as massive as the Earth and orbits once every 84 days. The other may be only five times as massive as the Earth, making it the smallest planet ever found around a normal star.
Just rightTheory predicts that the small planet should be about 50% wider than the Earth and have a rocky surface. It orbits its dim star every 13 days, and the astronomers calculate that it has a pleasant surface temperature of about 0 to 40°C – just right for liquid water, so the planet might be habitable.
"If you take an average value for the amount of starlight heating the planet, you get something like 20° C," Udry told New Scientist. That's similar to the average temperature in New York City, US, in June.
Astronomers have discovered "super-Earths" slightly larger than this one before. However, they are either too hot or too cold for liquid water to exist. The smallest world circling Gliese 581 is a "Goldilocks" planet with the conditions just right for potential life.
Spectacular sunsetsSunrises and sunsets on the planet must be spectacular. If you could stand on its surface, you would see its red host star looming 10 times wider in the sky than our own Sun appears.
Team member Xavier Delfosse from Grenoble University in France says he hopes that spacecraft missions will probe the world for signs of life over the next decade or two.
"On the treasure map of the universe, one would be tempted to mark this planet with an X," says Delfosse. "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."

[Astronuc]

Am confused.  Is this same one?
 'Goldilocks' planet may be just right for life

Yes, that is the one.  As the article states, there are other planets that are too hot (like Venus) or too cold, like Uranus or Neptune to support life, as we know it.

Gliese apparently has surface temperatures in the range of 0 - 40°C, which is the range of water temperatures, which are compatible for life on the earth.

 :koala

[Astronuc]

An interesting and perhaps relevant paper -

Detailed Models of super-Earths: How well can we infer bulk properties?
Authors: Diana Valencia (1), Dimitar D. Sasselov (2), Richard J. O'Connell (1); ((1) Earth and Planetary Sciences Dept., Harvard University; (2) Harvard-Smithsonian Center for Astrophysics)
http://arxiv.org/abs/0704.3454

The field of extrasolar planets has rapidly expanded to include the detection of planets with masses smaller than that of Uranus. Many of these are expected to have little or no hydrogen and helium gas and we might find Earth analogs among them. In this paper we describe our detailed interior models for a rich variety of such massive terrestrial and ocean planets in the 1-to-10 earth-mass range (super-Earths). The grid presented here allows the characterization of the bulk composition of super-Earths detected in transit and with a measured mass. We show that, on average, planet radius measurements to better than 5%, combined with mass measurements to better than 10% would permit us to distinguish between an icy or rocky composition. This is due to the fact that there is a maximum radius a rocky terrestrial planet may achieve for a given mass. Any value of the radius above this maximum terrestrial radius implies that the planet contains a large (> 10%) amount of water (ocean planet).

 

[Astronuc]

And the hottest extrasolar planet is  . . . .

HD 149026b

Located 279 light-years away in the constellation Hercules, HD 149026b is a so-called hot Jupiter, a giant gas planet that orbits very close to its star. It is a scorching 3,700 degrees Fahrenheit (2,040 degrees Celsius), three times hotter than Mercury and hotter than the coolest stars.

. . . .

Until very recently, HD 149026b was also the densest planet known. It contains higher levels of heavy elements-those other than hydrogen and helium-than all of the planets in our solar system combined, and its core might have up to 90 times the mass of the Earth.

"HD 149026b is simply the most exotic, bizarre planet," Harrington said. "It's pretty small, really dense, and now we find that it's extremely hot."

HD 149026b is a so-called "transiting" planet, meaning its orbit takes it directly in front of its star as seen from Earth. Using NASA's Spitzer Space Telescope, Harrington and his team measured the total light emitted by the planet-star system and used the information to calculate HD 149026b's temperature.

It is so hot that metals like titanium and vanadium may exist as vapors in the atmosphere!?

Jonathan Fortney at NASA Ames Research Center in California has indicated that HD 149026b orbits a very metal rich star.

[Astronuc]

Space telescope spots new planet
http://news.bbc.co.uk/1/hi/sci/tech/6611557.stm

The French-led Corot mission has spied its first planet - a very hot world bigger than Jupiter - passing in front of a far-off star.

The spacecraft was launched on 27 December last year and is the first to hunt for Earth-like planets from space.

Corot scientists said to find a planet so early on "significantly exceeded pre-launch expectations".

The new body is called Corot-exo-1b and can be found 1,500 light-years away in the constellation of Monoceros.

Corot hunts for planets by monitoring stars for tiny dips in brightness that result from objects transiting their faces.

 

[remcook]

also...the first map of an exoplanet:

http://www.spaceflightnow.com/news/n0705/09planetmap/

[vishniac]

Planet with unusual forms of water and ice:
http://edition.cnn.com/2007/TECH/space/05/16/odd.exoplanet.reut/index.html

What is cool is the discovery was made by a little observatory a few kilometers from where I live and they'll come and give a lecture about it at my school in two weeks. 8)

[Astronuc]

New, Distant Planets Discovered
http://www.npr.org/templates/story/story.php?storyId=10538664

Morning Edition, May 30, 2007 · Astronomers have announced the discovery of 28 more planets outside our solar system. Although the new finds are Jupiter-like "gas giants" with no solid surface, they are all part of multiple planet systems like our own. Smaller, Earth-like planets could also be in those systems, but for now, they're too small to detect.

[Astronuc]

Have Astronomers Observed the Aftermath of a Distant Planetary Collision?
 

Astronomers announced today that a mystery object orbiting a star 170 light-years from Earth might have formed from the collision and merger of two protoplanets. The object, known as 2M1207B, has puzzled astronomers since its discovery because it seems to fall outside the spectrum of physical possibility. Its temperature, luminosity, age, and location do not match up with any theory.

http://www.physorg.com/news119109042.html
 

The announcement was made in a press conference at the 211th meeting of the American Astronomical Society.

2M1207B orbits a 25-Jupiter-mass brown dwarf called 2M1207A seen in the direction of the constellation Centaurus. Computer models show that 2M1207A is very young, only about 8 million years old; therefore its companion should also be 8 million years old. At that age, it should have cooled to a temperature of less than 1300 degrees Fahrenheit (1000 Kelvin). However, observations show that 2M1207B is actually about 2400 degrees F (1600 K). The extra heat might be the result of a protoplanetary collision.