Posted on by Nancy Atkinson

Shedding Light on the Sun’s “Lithium Mystery”

Artist’s impression of a baby star still surrounded by a protoplanetary disc in which planets are forming. Credit: ESO

For decades, astronomers have known our Sun contains a low amount of lithium, while other solar-like stars actually have more. But they didn’t know why. By looking at stars similar to the Sun to study this anomaly, scientists have now discovered of a trend: the majority of stars hosting planets possess less than 1% of the amount of lithium shown by most of the other stars. “The explanation of this 60 year-long puzzle is for us rather simple,” said Garik Israelian, lead author on a paper appearing in this week’s edition of Nature. “The Sun lacks lithium because it has planets.”

This finding sheds light not only on the lack of lithium in our star, but also provides astronomers with a very efficient way of finding stars with planetary systems.

Isrealian and his team took a census of 500 stars, 70 of which are known to host planets, and in particular looked at Sun-like stars, almost a quarter of the whole sample. Using ESO’s HARPS spectrograph, a team of astronomers has found that Sun-like stars that host planets have destroyed their lithium much more efficiently than “planet-free” stars.

“For almost 10 years we have tried to find out what distinguishes stars with planetary systems from their barren cousins,” Israelian said. “We now have found that the amount of lithium in Sun-like stars depends on whether or not they have planets.”

These stars have been “very efficient at destroying the lithium they inherited at birth,” said team member Nuno Santos. “Using our unique, large sample, we can also prove that the reason for this lithium reduction is not related to any other property of the star, such as its age.”

Unlike most other elements lighter than iron, the light nuclei of lithium, beryllium and boron are not produced in significant amounts in stars. Instead, it is thought that lithium, composed of just three protons and four neutrons, was mainly produced just after the Big Bang, 13.7 billion years ago. Most stars will thus have the same amount of lithium, unless this element has been destroyed inside the star.

This result also provides the astronomers with a new, cost-effective way to search for planetary systems: by checking the amount of lithium present in a star astronomers can decide which stars are worthy of further significant observing efforts.

Now that a link between the presence of planets and curiously low levels of lithium has been established, the physical mechanism behind it has to be investigated. “There are several ways in which a planet can disturb the internal motions of matter in its host star, thereby rearrange the distribution of the various chemical elements and possibly cause the destruction of lithium,” said co-author Michael Mayor. ” It is now up to the theoreticians to figure out which one is the most likely to happen.”

Read the team’s paper.

Source: ESO

Posted on by Nancy Atkinson

Multi-Planet System is Chaotic, Dusty

NASA’s Spitzer Space Telescope captured this infrared image of a giant halo of very fine dust around the young star HR 8799. Image credit: NASA/JPL-Caltech/Univ. of Ariz.

Just what is going on over at the star HR 8799? The place is a mess! But we can just blame it on the kids. Young, hyperactive planets circling the star are thought to be disturbing smaller comet-like bodies, causing them to collide and kick up a huge halo of dust. HR 8799 was in the news in November 2008, for being one of the first with imaged planets. Now, NASA’s Spitzer Space Telescope has taken a closer look at this planetary system and found it to be a very active, chaotic and dusty system. Ah, youth: our solar system was likely in a similar mess before our planets found their way to the stable orbits they circle in today.

The Spitzer team, led by Kate Su of the University of Arizona, Tucson, says the giant cloud of fine dust around the disk is very unusual. They say this dust must be coming from collisions among small bodies similar to the comets or icy bodies that make up today’s Kuiper Belt objects in our solar system. The gravity of the three large planets is throwing the smaller bodies off course, causing them to migrate around and collide with each other. Astronomers think the three planets might have yet to reach their final stable orbits, so more violence could be in store. The planets around HR 8799 are about 10 times the mass of Jupiter.

“The system is very chaotic and collisions are spraying up a huge cloud of fine dust,” said Su. “What’s exciting is that we have a direct link between a planetary disk and imaged planets. We’ve been studying disks for a long time, but this star and Fomalhaut are the only two examples of systems where we can study the relationships between the locations of planets and the disks.”

When our solar system was young, it went through similar planet migrations. Jupiter and Saturn moved around quite a bit, throwing comets around, sometimes into Earth. Some say the most extreme part of this phase, called the late heavy bombardment, explains how our planet got water. Wet, snowball-like comets are thought to have crashed into Earth, delivering life’s favorite liquid.

The Spitzer results were published in the Nov. 1 issue of Astrophysical Journal. The observations were made before Spitzer began its “warm” mission and used up its liquid coolant.

Source: JPL

Posted on by Nancy Atkinson

No Earth-Sized Planet Hunting for Kepler Until 2011

Artist concept of Kepler in space. Credit: NASA/JPL

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A glitch in the Kepler spacecraft’s electronics means the space telescope will not have the ability to spot an Earth-sized planet until 2011, according to principal investigator William Borucki. Noisy amplifiers are creating noise that compromises Kepler’s view, and the team will have to generate and upload a software fix for the spacecraft. “We’re not going to be able to find Earth-size planets in the habitable zone — or it’s going to be very difficult — until that work gets done,” said Borucki, who revealed the problem last week to the NASA Advisory Council.

The team knew about the problem before launch, as the noisy amplifiers were noticed during ground testing before the device was launched. “Everybody knew and worried about this,” says instrument scientist Doug Caldwell. But he said the team thought it was riskier to pry apart the telescope’s electronic guts than to deal with the problem after launch.

Kepler launched on March 6, 2009 and is designed to look for the slight dimming of light that occurs when a planet transits, or crosses in front of a star.

The problem was is caused by amplifiers that boost the signals from the charge-coupled devices that form the heart of the 0.95-metre telescope’s 95-million-pixel photometer, which detects the light emitted from the distant stars. Three of the amplifiers are creating noise, and even though the noise affects only a small portion of the data, Borucki says, but the team has to fix the software — it would be “too cumbersome” to remove the bad data manually — so that it accounts for the noise automatically.

The team is hoping to fix the issue by changing the way data from the telescope is processed, and looks to have everything in place by 2011.

Borucki pointed out that the team was probably going to have to wait at least three years to find an extrasolar Earth orbiting in the habitable zone anyway. Astronomers typically wait for at least three transits before they confirm a planet’s existence; for an Earth-sized planet orbiting at a distance similar to that between the Earth and the Sun, three transits would take three years. But Borucki said that the noise will hinder searches for a rarer scenario: Earth-sized planets that orbit more quickly around dimmer, cooler stars — where the habitable zone is closer in. These planets could transit every few months.

The delay for Kepler could mean ground-based observers could now have the upper hand in the race for the holy grail of planet hunting: finding an Earth-like planet.

Kepler and CoRoT (Convection, Rotation and Planetary Transits) both look for transiting planets while the ground-based telescopes use radial velocity, looking for tiny wobbles in the motion of the parent stars caused by the planets’ gravity. The journal Nature quoted astronomer Greg Laughlin from the University of California at Santa Cruz, saying that the delay for Kepler makes it “more likely that the first Earth-mass planet is going to go to the radial-velocity observers”.

Source: Nature

Posted on by Nancy Atkinson

Organic Molecules Detected in Exoplanet Atmosphere

Artist concept of exoplanet HD 209458b. Credit: NASA/JPL-Caltech/T. Pyle (SSC)

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The basic chemistry for life has been detected the atmosphere of a second hot gas planet, HD 209458b. Data from the Hubble and Spitzer Space Telescopes provided spectral observations that revealed molecules of carbon dioxide, methane and water vapor in the planet’s atmosphere. The Jupiter-sized planet – which occupies a tight, 3.5-day orbit around a sun-like star — is not habitable but it has the same chemistry that, if found around a rocky planet in the future, could indicate the presence of life. Astronomers are excited about the detection, as it shows the potential of being able to characterize planets where life could exist.

HD 209458b is in the constellation Pegasus.

“It’s the second planet outside our solar system in which water, methane and carbon dioxide have been found, which are potentially important for biological processes in habitable planets,” said researcher Mark Swain of JPL. “Detecting organic compounds in two exoplanets now raises the possibility that it will become commonplace to find planets with molecules that may be tied to life.”

Over a year ago, astronomers detected these same organic molecules in the atmosphere of another hot, giant planet, called HD 189733b, using the same two space telescopes. Astronomers can now begin comparing the chemistry and dynamics of these two planets, and search for similar measurements of other candidate exoplanets.

The detections were made through spectroscopy, which splits light into its components to reveal the distinctive spectral signatures of different chemicals. Data from Hubble’s near-infrared camera and multi-object spectrometer revealed the presence of the molecules, and data from Spitzer’s photometer and infrared spectrometer measured their amounts.

“This demonstrates that we can detect the molecules that matter for life processes,” said Swain. Astronomers can now begin comparing the two planetary atmospheres for differences and similarities. For example, the relative amounts of water and carbon dioxide in the two planets is similar, but HD 209458b shows a greater abundance of methane than HD 189733b. “The high methane abundance is telling us something,” said Swain. “It could mean there was something special about the formation of this planet.”

Rocky worlds are expected to be found by NASA’s Kepler mission, which launched earlier this year, but astronomers believe we are a decade or so away from being able to detect any chemical signs of life on such a body.

If and when such Earth-like planets are found in the future, “the detection of organic compounds will not necessarily mean there’s life on a planet, because there are other ways to generate such molecules,” Swain said. “If we detect organic chemicals on a rocky, Earth-like planet, we will want to understand enough about the planet to rule out non-life processes that could have led to those chemicals being there.”

“These objects are too far away to send probes to, so the only way we’re ever going to learn anything about them is to point telescopes at them. Spectroscopy provides a powerful tool to determine their chemistry and dynamics.”

For more information about exoplanets and NASA’s planet-finding program, check out PlanetQuest.

Source: Spitzer

Posted on by Nancy Atkinson

HARPS Discovers 32 New Exoplanets

A planet 6 times the mass of Earth orbits around the star Gliese 667 C, which belongs to a triple system. Credit: ESO

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Astronomers have found 32 new planets outside our solar system with the High Accuracy Radial Velocity Planet Searcher, better known as HARPS, the spectrograph for the European Southern Observatory’s (ESO) 3.6-metre telescope. The number of known exoplanets is now at 406, and HARPS itself has discovered more than 75 exoplanets in 30 different planetary systems. Included in this most recent batch are several low-mass planets – so-called “Super Earths” about the size of Neptune. The image above is an artist’s impression of a planet discovered that is 6 times the mass of Earth, which circles the low-mass host star, Gliese 667 C, at a distance equal to only 1/20th of the Earth-Sun distance. Two other planets were discovered previously around this star.

“HARPS is a unique, extremely high precision instrument that is ideal for discovering alien worlds,” said ESO astronomer Stéphane Udry. “We have now completed our initial five-year program, which has succeeded well beyond our expectations.”

No Earth-like planets were discovered in this group that was announced today at an exoplanet conference in Portugal.

HARPS has facilitated the discovery of 24 of the 28 planets known with masses below 21 Earth masses. As with the previously detected super-Earths, most of the new low-mass candidates reside in multi-planet systems, with up to five planets per system. This new group includes a total of 11 planets with masses between 5 and 21 times that of Earth – and 9 in multi-planet systems — and increases the number of known low-mass planets by 30%.

HARPS uses the radial velocity technique which measures the back-and-forward motions of stars by detecting small changes in a star’s radial velocity as it wobbles slightly from a gentle gravitational pull from an otherwise unseen planet. HARPS can detect changes in velocity as small as 3.5 km/hour, a steady walking pace.

Notable discoveries by HARPS during the past five years include the first super-Earth in 2004 (around µ Ara; ESO 22/04); in 2006, the trio of Neptunes around HD 69830 (ESO 18/06); in 2007, Gliese 581d, the first super Earth in the habitable zone of a small star (ESO 22/07); and in 2009, the lightest exoplanet so far detected around a normal star, Gliese 581e (ESO 15/09). More recently, they found a potentially lava-covered world, with density similar to that of the Earth’s (ESO 33/09).

“These observations have given astronomers a great insight into the diversity of planetary systems and help us understand how they can form,” says team member Nuno Santos.

Source: ESO

Posted on by Jean Tate

Exoplanet

Hubble's view showing a possible exoplanet Fomalhaut b (NASA/HST)

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An exoplanet – or extrasolar planet – is a planet which orbits a star other than our own Sun.

After a bit of a false start – lasting many decades! – when a small number of detections of planets around other stars were reported but not confirmed, the first reliable, independently confirmed exoplanet was discovered – by Campbell, Walker, and Yang – in 1988 (though solid confirmation came only in 2003), around Gamma Cephei. Between 1988 and 2003, two planets were detected, and confirmed, orbiting a pulsar (which has the catchy name of PSR 1257+12) – in 1992 – and an exoplanet was discovered, and confirmed, around the ordinary (main sequence) star 51 Pegasi (in 1995). It was this discovery that started the modern exoplanet gold rush.

There are now nearly 400 exoplanets detected and confirmed (and a few more whose status is uncertain). The Extrasolar Planets Encyclopaedia is a website which keeps track of all announcements, confirmations, etc. It also has an excellent tutorial on the methods used to discover such planets.

The first multiple system – a star with more than one exoplanet – discovered was Upsilon Andromedae (this star is actually a binary, so the discovery was a first in two ways). The first planet was discovered in 1996, and the second (and third!) in 1999. In this case independent confirmation came quite quickly. Today more than 20 such multiple-planet systems are known.

Most exoplanets have been discovered by the radial velocity, or Doppler, method: the star’s apparent speed away from (or towards) us – as measured by sensitive spectrographs – varies in a regular way, due to the gravitational pull of the exoplanet (remember that two bodies in a stable gravitational system will orbit the center of mass). Almost all have been found by ground-based telescopes. This is likely to change in the next few years as dedicated space-based telescopes – such as NASA’s Kepler and the ESA’s COROT – continue to make new discoveries. As these use the transit method (detecting tiny changes in a star’s intensity, as an exoplanet goes between it and us), the Doppler method may soon lose its ‘most exoplanets discovered’ status.

There are literally dozens of Universe Today stories on exoplanets! Here are a few, covering many different aspects: Smallest Terrestrial Exoplanet Yet Detected, Astrometry Finds an Exoplanet, Exoplanet Has Oddball Orbit, New Technique Allows Astronomers to Discover Exoplanets in Old Hubble Images, Carbon Dioxide Detected on Exoplanet HD 189733 b, and Exoplanet Image Confirmed.

There’s also a great overview of this topic in the Astronomy Cast episode A Zoo of Extrasolar Planets, and the somewhat older episode Discovering Another Earth is excellent too.

Source: Wikipedia

Posted on by Nancy Atkinson

Rocky World COROT-7b Rains Rocks

The exoplanet Corot-7b is so close to its Sun-like host star that it must experience extreme conditions. Sister planet, CoRot-7c is seen in the distance. Credit: ESO

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If any creature lives on COROT-7b, the recently confirmed rocky exoplanet, they might think the sky is falling. This planet is close enough to its star that its “day-face” is hot enough to melt rock, and according to models by scientists at Washington University in St. Louis, COROT-7b’s atmosphere is made up of the ingredients of rocks and when “a front moves in,” pebbles condense out of the air and rain into lakes of molten lava below. Yikes!

This unusual rocky world was the first planet found orbiting the star COROT-7, an orange dwarf in the constellation Monoceros, or the Unicorn. COROT-7b is less than twice the size of Earth and only five times its mass. But this place is nothing like Earth.

“The only atmosphere this object has is produced from vapor arising from hot molten silicates in a lava lake or lava ocean,” said Bruce Fegley Jr., Ph.D., professor at Wash U, who created models of COROT-7b along with research assistant Laura Schaefer. Their paper appears in the Oct. 1 issue of The Astrophysical Journal.

This star-facing side has a temperature of about 2600 degrees Kelvin (4220 degrees Fahrenheit). That’s infernally hot—hot enough to vaporize rocks. The global average temperature of Earth’s surface, in contrast, is only about 288 degrees Kelvin (59 degrees Fahrenheit).

The side in perpetual shadow, on the other hand, is positively chilly at 50 degrees Kelvin (-369 degrees Fahrenheit).

COROT detects small, transiting exoplanet. Credits: CNES
COROT detects small, transiting exoplanet. Credits: CNES

So, what might the planet’s atmosphere be like? To find out Schaefer and Fegley used thermochemical equilibrium calculations with a special computer program called MAGMA that was used to study high-temperature volcanism on Io, Jupiter’s innermost Galilean satellite.

Because the scientists didn’t know the exact composition of the planet, they ran the program with four different starting compositions. “We got essentially the same result in all four cases,” says Fegley.
Perhaps because they were cooked off, COROT-7b’s atmosphere has none of the volatile elements or compounds that make up Earth’s atmosphere, such as water, nitrogen and carbon dioxide.

“Sodium, potassium, silicon monoxide and then oxygen — either atomic or molecular oxygen — make up most of the atmosphere.” But there are also smaller amounts of the other elements found in silicate rock, such as magnesium, aluminum, calcium and iron.

Why is there oxygen on a dead planet, when it didn’t show up in Earth’s atmosphere until 2.4 billion years ago, when plants started to produce it?

“Oxygen is the most abundant element in rock,” says Fegley, “so when you vaporize rock what you end up doing is producing a lot of oxygen.”

The peculiar atmosphere has its own singular weather. “As you go higher the atmosphere gets cooler and eventually you get saturated with different types of ‘rock’ the way you get saturated with water in the atmosphere of Earth,” explains Fegley. “But instead of a water cloud forming and then raining water droplets, you get a ‘rock cloud’ forming and it starts raining out little pebbles of different types of rock.”

Even more strangely, the kind of rock condensing out of the cloud depends on the altitude. The atmosphere works the same way as fractionating columns, the tall knobby columns that make petrochemical plants recognizable from afar. In a fractionating column, crude oil is boiled and its components condense out on a series of trays, with the heaviest one (with the highest boiling point) sulking at the bottom, and the lightest (and most volatile) rising to the top.

Instead of condensing out hydrocarbons such as asphalt, petroleum jelly, kerosene and gasoline, the exoplanet’s atmosphere condenses out minerals such as enstatite, corundum, spinel, and wollastonite. In both cases the fractions fall out in order of boiling point.

The atmosphere of COROT-7b may not be breathable, but it is certainly amusing.

Source: Washington University

Posted on by Fraser Cain

Super Earths

An artist’s impression of Gliese 581d, an exoplanet about 20.3 light-years away from Earth, in the constellation Libra. Credit: NASA

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The holy grail in the search for extrasolar planets will be the discovery of Earthlike planets orbiting other stars. With better telescopes and techniques, astronomers will eventually be able to even detect the atmospheres of extrasolar planets and determine if there’s life there. Although Earth-sized planets are impossible to detect with current observatories, astronomers are now finding super earths.

A super Earth is a terrestrial planet orbiting a distant star. But instead of having the mass of our own planet, it might have 2, 5, or even 10 times the mass of the Earth. Although that makes them large, very massive planets, they’re not as large or massive as gas giants.

And just because they’re called super Earths doesn’t mean they’re habitable, or even Earthlike in climate at all. Super Earths could be orbiting close to their parent star, or well outside the solar system’s habitable zone.

Scientists haven’t completely settled on a definition for super Earths. Some believe a planet should be considered a super Earth if it’s a terrestrial planet between 1 and 10 Earth masses, while others think it should be between 5 and 10 Earth masses.

The first super Earth ever discovered was found in 1991 orbiting a pulsar. Obviously that wouldn’t really be a very habitable place to live. The first super earth found orbiting a main sequence star was found in 2005, orbiting the star Gliese 876. It’s estimated to have 7.5 times the mass of the Earth, and orbits its parent star every 2 days. With such a short orbital period, you can expect that it’s orbiting very close to its parent star. Temperatures on the surface of the planet reach 650 kelvin.

The first super earth found within its star’ habitable zone was Gliese 581 c. It’s estimated to have 5 Earth masses, and orbits its parent star at a distance of 0.073 astronomical units (1 AU is the average distance from the Earth to the Sun). That’s pretty close to the star, and Gliese 581 c would probably have a runaway greenhouse effect, similar to Venus. But right beside that is Gliese 581 d, with a mass of 7.7 Earths and an orbit of 0.22 AU. This planet could very well have liquid water on its surface.

The smallest super Earth discovered so far is MOA-2007-BLG-192Lb, which has only 3.3 times the mass of the Earth, and was orbiting a brown dwarf star. But this record will probably be beaten by the time you read this, as planet hunters get better. It’s only a matter of time before a true Earthlike planet is discovered.

We have written many articles about super Earths. Here’s an article speculating on the kinds of atmospheres that super Earths might have, and another article about how similar super Earths really are to our own planet.

Here’s an artist’s impression of a super Earth features on NASA’s Astronomy Picture of the Day website, and here’s an article from NASA about super Earths.

We also recorded an episode of Astronomy Cast dealing with the different kinds of extrasolar planets you can find. Listen to it here. Episode 125: A Zoo of Extrasolar Planets.

Source: Wikipedia

Posted on by Nancy Atkinson

Biggest Exoplanet Yet Orbits the Wrong Way

An artist's impression of a transiting exoplanet Credit:NASA/Hubble

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Planet hunters from the UK have discovered the largest exoplanet yet, and its uniqueness doesn’t end there. Dubbed WASP-17, this extra large world is twice the size of Jupiter but is super-lightweight, “as dense as expanded polystyrene” one astronomer said. Plus it is going the wrong way around its home sun, making it the first exoplanet known to have a retrograde orbit. As a likely a victim of planetary billiards, astronomers say this unusual planet casts new light on how planetary systems form and evolve.

Astronomers say the planet must have flipped direction after a near miss with another huge “big brother” planet swung it around like a slingshot. “Newly formed solar systems can be violent places,” said graduate student David Anderson, of Keele University. “Our own moon is thought to have been created when a Mars-sized planet collided with the recently formed Earth and threw up a cloud of debris that turned into the moon. A near collision during the early, violent stage of this planetary system could well have caused a gravitational slingshot, flinging WASP-17 into its backwards orbit.”

An artist's impression of a transiting exoplanet. Credit: ESA C Carreau
An artist's impression of a transiting exoplanet. Credit: ESA C Carreau

Though it is only half the mass of Jupiter it is bloated to nearly twice Jupiter’s size.

Astronomers have long wondered why some extra-solar planets are far bigger than expected, and WASP-17 points to the explanation. Scattered into a highly elliptical, retrograde orbit, it would have been subjected to intense tides. Tidal compression and stretching would have heated the gas-giant planet to its current, hugely bloated extent. “This planet is only as dense as expanded polystyrene, seventy times less dense than the planet we’re standing on”, said Coel Hellier, also of Keele University.

WASP-17 is the 17th new exoplanet found by the Wide Area Search for Planets (WASP) consortium of UK universities. The WASP team detected the planet using an array of cameras that monitor hundreds of thousands of stars, searching for small dips in their light when a planet transits in front of them. Geneva Observatory then measured the mass of WASP-17, showing that it was the right mass to be a planet. The WASP-South camera array that led to the discovery of WASP-17 is hosted by the South African Astronomical Observatory.

Read the team’s paper here.

Source: STFC

Posted on by Abby Cessna

Giant Planets

Jupiter, seen by Cassini. Image credit: NASA/JPL

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While the inner four planets seem large, they are nothing compared to the four outer planets, which are also known as gas giants or Jovian planets. The four giant planets in our Solar System are Jupiter, Saturn, Uranus, and Neptune.

Jupiter is the largest planet in our Solar System, and it truly is a giant planet. Jupiter is so large that you could fit 1321 Earths inside the planet. It is a gas giant, which means that it is comprised almost entirely of gas with a liquid core of heavy metals. Since none of the gas giants has a solid surface, you cannot stand on any of these planets, nor can spacecraft land on them. Another common characteristic of the giant planets is that they all have dozens of moons. In fact, Jupiter has 63 moons that have been discovered so far.  

All of the giant planets in our Solar System have rings, but Saturn’s rings are by far the most famous of any. This planet’s ring system is composed of rock, dust, and other particles. The other planetary ring systems are made of similar elements.

Uranus and Neptune are also gas giants, but instead of just helium and hydrogen, they also have significant amounts of ices in their atmospheres. These ices include water, methane, and ammonia. It is the methane in the atmospheres of Uranus and Neptune that give the planets their blue color. Uranus and Neptune are also known as ice giants because of the proportion of ices in their atmospheres.

Giant planets are not limited to our Solar System either. In fact, astronomers have discovered many Jupiter-like planets in other solar systems. For example, in 2007, a group of British astronomers discovered three gas giants that are heavier than Jupiter is. These gas giants are much closer to their star than our Solar System’s gas giants are to the Sun. Scientists think that this may be one reason why these extrasolar planets are heavier, suggesting that only heavier planets can survive closer to a star. Because these planets are so much closer to their sun, they are much hotter than Jupiter and our Solar System’s other gas giants are.

These are just a handful of the gas giants discovered in different solar systems. Astronomers have discovered other extrasolar planets much bigger than Jupiter. Since all of the first extrasolar planets found were gas giants similar to Jupiter, astronomers began to despair of ever finding Earth-like planets that could support life. Recently though, astronomers have discovered different types of extrasolar planets, raising their hopes of finding life on other planets.

Universe Today has a number of articles to check out on gas giants and how big planets get.

You should also take a look at these articles on gas giants and British scientists discover giant planets hotter and heavier than Jupiter.

Astronomy Cast has an episode on extrasolar planets, hot Jupiters, and pulsar planets you should not miss.