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Jovian planets — the giants of solar systems

The gas planets, the giants of the solar system, the jovian planets — call them what you will, these planets have fascinated mankind for centuries, and they’re still one of the more intriguing astronomical bodies out there.

Jovian literally means “Jupiter-like”, from “Jove” — another name for the Roman god Jupiter (called Zeus by the Greeks). They are primarily composed of gas or ice and are much larger than the Earth. They’re also much easier to detect than other planets — largely because they’re so big.

The name-giver of all Jovian planets: Jupiter. Jupiter is 318 times as massive as Earth, and it is 2.5 times larger than all the planets in the solar system combined. Image credits: NASA.

You can’t walk on a jovian planet

Jovian planets are comprised of fluid (gases or ices) rather than rock or other solid matter. Although giant rocky planets can exist, these are thought to be much rarer than gas or ice giants.

Jupiter is made up almost entirely of hydrogen and helium — the same elements found in the Sun, though at different temperatures and pressures. Here on Earth, hydrogen and helium are gases, but under the huge temperatures and pressures of Jupiter, hydrogen can be a liquid or even a kind of metal. We’re not entirely sure what lies at the center of Jupiter, but researchers believe that most likely, the core is similar to a thick, boiling-hot soup with a temperature of about 55,000 Fahrenheit (30,000 Celsius).

Saturn has a similar structure, with layers of metallic hydrogen, liquid hydrogen, and gaseous hydrogen, covered by a layer of visible clouds. Unlike Jupiter and Saturn, Uranus and Neptune have cores of rock and metal and different chemical compositions.

A potential internal structure of the jovian planets. It’s not clear if the core consists of rock, but it must be something very dense and hot. Image credits: University of Virginia.

We’re not sure exactly what the surface of jovian planets is like, but based on all we know, it’s not something you can walk on. Jovian planets tend to have very thick clouds (the clouds on Jupiter, for instance, are 30 miles or 50 km thick). After that, there’s gaseous hydrogen and helium, then more and more condensed gas, until you ultimately end up in liquid, metallic hydrogen. Saturn has a similar structure, though it is far less massive than Jupiter.

You might even have trouble realizing where the atmosphere ends and where the “planet” begins.

Methane clouds on Neptune. Image credits: NASA / JPL.

Uranus and Neptune, much smaller than both Jupiter and Saturn, have gaseous hydrogen surrounding a mantle of ice and a rocky core.

Jovian planets also have atmospheres with bands of circulating material. These bands typically encircle the planet parallel to the equator, with lighter bands lying at higher altitudes and being areas of higher pressure, and darker bands being lower in the atmosphere as low-pressure regions. This atmospheric circulation is similar only in principle to that on Earth, it has a very different structure.

Atmospheric bands on Jupiter. Image credits: NASA/JPL.

There are also other, smaller visible structures. The most famous of these is Jupiter’s Great Red Spot, which is essentially a giant storm that has been active for centuries. Saturn’s hexagon is another very well-known feature — both of these are much larger than the Earth itself.

These spinning balls of gas and liquids are truly impressive, and we’re still learning new things about them.

Jovian planets in our solar system

While still far smaller than the sun, jovian planets are by far the largest planets in our solar system. Image credits: NASA / University of Virginia.

Not all gas planets are alike. In fact, the reason why some astronomers prefer the term jovian planets to gas giants is that not all jovian planets are made of gas.

For instance, just Jupiter and Saturn are true gas giants, whereas Uranus and Neptune are ice giants. However, even this is a bit misleading: at the temperature and pressures on these planets, distinct gas and liquid phases cease to exist. Even so, the chemistry of the two groups is different: hydrogen and helium dominate Jupiter and Saturn, whereas, in the case of Uranus and Neptune, it’s water, methane, and ammonia. The two latter planets are thought to have a slushie-like mantle that spans over half of the planet diameter.

Image credits: NASA.

All four of these planets have large systems of satellites, and these satellites can be very interesting in their own right (we’ll get to that in a minute — there’s a good chance that life may be hiding in the jovian satellites). Saturn, for instance, has 82 designated satellites, and countless undesignated moonlets. Despite being larger, Jupiter “only” has 79 known satellites. Uranus has 27 and Neptune has 14.

All these four planets also have rings, though Saturn’s are by far the most pronounced.

Artist’s impression of the Voyager probe with the Jovian planets and some of their satellites. If you look closely, you can see Neptune’s rings. Image credits: Don Davis.

Much of what we know about gas and ice giants in general, we extrapolate from what we see in our own solar system. This being said, astronomers are aware that jovian planets can be very different and have a much greater variety than we see in our solar system.

Extrasolar Jovian planets

Roughly speaking, jovian planets can be split into 4 categories:

  • gas giants (like Jupiter and Saturn) — mostly consisting of hydrogen and helium, and only 3-13% heavier elements;
  • ice giants (like Neptune and Uranus) — a hydrogen-rich atmosphere covering an icy layer of water;
  • massive solid planets (somewhat similar to the Earth, but huge) — tangible evidence for this type of planet only emerged in 2014, and these planets are still poorly understood. Astronomers suspect that solid planets up to thousands of Earth masses may be able to form, but only around massive stars;
  • super puffs — planets comparable in size with Jupiter, but in mass with the Earth. These planets are super rarefied, and were only discovered in the past decade; the most extreme examples known are the three planets around Kepler-51.
Artistic rendering of Gliese 3470 b — a rare “superpuff”. The two are believed to be comparable in mass. Image credits: NASA.

Based on what we’ve seen so far, jovian planets seem pretty common across our galaxy. However, we’ve only started discovering exoplanets very recently, and it’s hard to say whether the planets we’ve found so far are representative of the larger picture.

However, based on the fact that researchers have discovered far more Neptune-sized planets than Jupiter-sized planets (although the latter are easier to discover), it’s pretty safe to say that it’s the Neptune-sized planets that are more common.

Image credits: NASA.

A particularly interesting class of jovian planets is the so-called Hot Jupiters.

Hot Jupiters are the easiest planets to detect. As the name implies, they are Jupiter-sized planets, but they lie very close to their stars and have a rapid orbital period that produces effects that are more easily detected. For instance, one such planet revolved around its star in only 18 hours, making for one very short year. Another freakish example of a Hot Jupiter is believed to have surface temperatures of 4,300°C (7,800°F) — which is hotter than some stars we know.

Extrasolar planets, and Hot Jupiters in particular, can shed a lot of light on the evolution of solar systems. It is believed that these planets form in the outer parts of solar systems (like Jupiter), but they slowly migrate towards the star, drawn by gravitational attraction. As they do so, they could wreak havoc on the entire solar system, much like a big billiards ball.

Artist’s impression of a Hot Jupiter. Image credits: ESO/L. Calçada.

Some jovian planets get so large that they blur the line between a planet and a brown dwarf. Brown dwarfs are neither truly stars nor planets. As a rule of thumb, jovian planets are only “planets” until they are 15 times the mass of Jupiter — after that, they “become” brown dwarfs.

Because of the limited techniques currently available to detect and study exoplanets, there are still many things we don’t know about exoplanets, even those as big as Jupiter. We tend to associate these planets by size with the ones in our own solar system, piecing together other available information (which is scarce). As our telescopes, equipment, and theoretical models become better, we will no doubt better our understanding of jovian planets, and exoplanets in general.

This image shows an artist’s impression of the ten hot Jupiter exoplanets studied by David Sing and his colleagues. From top left to to lower left these planets are WASP-12b, WASP-6b, WASP-31b, WASP-39b, HD 189733b, HAT-P-12b, WASP-17b, WASP-19b, HAT-P-1b and HD 209458b.

Life around Jovian planets

Jovian planets are not exactly life-friendly — at least not directly. A giant, spinning, mass of fluid you can’t even stand on, either very hot or very cold, doesn’t sound very attractive to life forms. But jovian satellites are a different story. In fact, astronomers are starting to believe that the satellites of Jupiter and Saturn may be the best places to look for extraterrestrial life in our solar system.

Both Jupiter and Saturn lie rather far from the Sun. They are cold, frigid places, as are their satellites — at least on the surface.

Jupiter’s icy moon, Europa. Image credits: NASA.

Researchers now believe that some of the icy satellites of Jupiter and Saturn (especially Europa and Enceladus) could host life under their frozen surfaces.

Although the surface temperatures are extremely low on these satellites, astronomers have some clues that both satellites may harbor oceans of liquid water beneath the frozen surface. Basically, the huge gravitational effect from their host planets causes friction and shear in the ice, which produces sufficient heat to melt the ice. This is called tidal heating. Geothermal and geological activity may also contribute to this effect, creating a liquid, salty water beneath the ice — and while this has not yet been confirmed, these could be suitable conditions for life to emerge.

Enceladus is believed to harbor a liquid ocean in its subsurface. Image credits: NASA / JPL.

In addition to Europa and Enceladus, several other jovian satellites could harbor life (with various degrees of likelihood): Callisto, Ganymede, Io, Triton, Dione, and even Pluto’s moon Charon could all have a liquid ocean compatible with life. NASA’s Clipper mission is set for launch in 2024, with the goal of exploring Europa’s potential habitability. Some scientists believe there are as many habitable exomoons as there are habitable exoplanets.

Jovian planets seem to play a key role in the structure of solar systems. Whether their satellites can hold life or not, they are an extremely important puzzle piece in our understanding of how solar systems form, evolve, and how the Earth fits in this grand cosmic puzzle.

Illustration of CI Tau, which is surrounded by a planetary disc and has four gas giants orbiting around it. Credit: University of Cambridge.

Gas giants orbiting young star may require astronomers to rethink planetary formation

Illustration of CI Tau, which is surrounded by a planetary disc and has four gas giants orbiting around it. Credit: University of Cambridge.

Illustration of CI Tau, which is surrounded by a planetary disc and has four gas giants orbiting around it. Credit: University of Cambridge.

Astronomers have discovered a peculiar solar system some 500 light-years away from Earth that may force them to rethink how planets form. The star in question is only two million years old — a mere ‘toddler’ by astronomical standards — but despite its very young age, it’s orbited by four Jupiter and Saturn-sized planets.

A crowded baby star

Since the first confirmation of an exoplanet orbiting a sun-like star in 1995, and with only a few narrow slices of our Milky Way galaxy surveyed so far, astronomers have confirmed 2,327 exoplanets, with a further 2,244 awaiting confirmation.

A recent statistical estimate places, on average, at least one planet around every star in the galaxy. However, only 1% of the stars astronomers have surveyed so far host a hot Jupiter — a class of gas giant exoplanets that are inferred to be physically similar to Jupiter but that have a very short orbital period.

Most of the hot Jupiters currently identified orbit stars that are at least hundreds of millions of years old. This is why CI Tau, the young star recently studied by researchers at the University of Cambridge, is so interesting. What’s more, it has not one but four gas giants orbiting it.

The astronomers used Atacama Large Millimeter/submillimeter Array (ALMA) to identify the exoplanets. CI Tau is surrounded by a huge disc of dust and ice, known as a protoplanetary disc, which will seed planets, moons, asteroids, and other objects in its system. ALMA’s instruments were able to find distinct gaps in the disc which theoretical modeling showed would correspond to gas giant planets orbiting the star.

According to the new study published the Astrophysical Journal Letters, the four planets differ greatly in their orbit. The closest planet to CI Tau, a juvenile hot Jupiter, is within the equivalent orbit of Mercury.

The farthest orbits are at a distance three times greater than that of Neptune from the Sun. The two outer planets are about the mass of Saturn, while the two inner planets are around one and 10 times the mass of Jupiter respectively. Given that the outermost planet is more than a thousand times further from the star than the innermost one, the system has also set a new record for the most extreme range of orbits observed so far.

Scientists are not sure what to make of this anomalous system. Hot Jupiters have always puzzled astronomers because they are often thought to orbit too close to their parent stars to have formed in situ — instead, they might be captured rogue planets. But considering the age of CI Tau, the findings suggest that hot Jupiters could form within close proximity of a star.

“It is currently impossible to say whether the extreme planetary architecture seen in CI Tau is common in hot Jupiter systems because the way that these sibling planets were detected—through their effect on the protoplanetary disc – would not work in older systems which no longer have a protoplanetary disc,” said Professor Cathie Clarke from Cambridge’s Institute of Astronomy, the study’s first author.

In the future, the team of researchers plans on studying CI Tau at multiple wavelengths to learn more about the disc and its planets. For instance, they would like to see whether the outer planets played a role in driving their innermost sibling into such an ultra-close orbit. How the two outer planets formed in the first place is also a mystery.

“Planet formation models tend to focus on being able to make the types of planets that have been observed already, so new discoveries don’t necessarily fit the models,” said Clarke. “Saturn mass planets are supposed to form by first accumulating a solid core and then pulling in a layer of gas on top, but these processes are supposed to be very slow at large distances from the star. Most models will struggle to make planets of this mass at this distance.”


Artist impression of WASP-18b. Credit: NASA.

Huge exoplanet ten times more massive than Jupiter has unique carbon monoxide atmosphere

About 300 light years away lies a weird planet, unlike any other astronomers have ever seen. Called WASP-18b, this hot giant has 10 times the mass of Jupiter and a peculiar atmosphere mostly made of carbon monoxide. The data suggests that there’s no water vapor to be found in its stratosphere, which could change our understanding of the formation of such planets.

Artist impression of WASP-18b. Credit: NASA.

Artist impression of WASP-18b. Credit: NASA.

WASP-18b was first identified by the Wide Angle Search for Planets survey which uses a double setup each comprising 8 cameras that cover 480 degrees of the sky. One set of cameras lies in the northern hemisphere, the other in the southern hemisphere. Since both setups entered operation in 2006, astronomers have used them to gather data on 30 million stars. By studying small changes or wobbles in the light of a star, scientists can determine whether a planet is passing by and, if yes, they can derive some of its properties. WASP-18b, along with another 100 planets or so have been discovered by the survey in this manner.

[panel style=”panel-info” title=”What’s a Hot Jupiter” footer=””]A ‘Hot Jupiter’ is an exoplanet like Jupiter but much hotter, with orbits that take it feverishly close to the parent star.[/panel]

This behemoth planet is quite different from many others discovered by the WASP survey or the prolific Kepler Space Telescope responsible for over 2,000 confirmed exoplanet sightings. When NASA scientists directed the lenses of the Hubble and Spritzer telescopes towards WASP-18b, they determined that there likely isn’t any water in the stratosphere which is instead largely made of carbon monoxide. Data suggests the stratosphere is packed with hot gas while the lower troposphere is dominated by cooler carbon monoxide.

“The composition of WASP-18b defies all expectations,” said Kyle Sheppard of NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

“We don’t know of any other extrasolar planet where carbon monoxide so completely dominates the upper atmosphere,” Sheppard said.

The team determined the two types of carbon monoxide signatures at a wavelength of about 1.6 micrometers and an emission signature at about 4.5 micrometers. This is the first time researchers have detected both types of fingerprints for a single type of molecule in an exoplanet’s atmosphere.

All of these observations point to the curious possibility that this planet may contain 300 times more metals than other exoplanets of similar mass. If that’s true, WASp-18b clearly did not form in the same way as other Hot Jupiters before it.

“This rare combination of factors opens a new window into our understanding of physicochemical processes in exoplanetary atmospheres,” said Nikku Madhusudhan, a co-author of the study from the University of Cambridge.

Findings appeared in the Astrophysical Journal Letters.

The day side of the planet, called WASP-12b, eats light rather than reflects it into space. Credit: NASA, ESA, and G. Bacon (STScI).

Odd Jupiter-sized exoplanet is hot enough to melt metal but paradoxically pitch-black

An oddball called WASP-12b, an exoplanet orbiting a star somewhat heftier than the sun, is the “blackest” planet we’ve found so far. NASA’s Hubble Space Telescope turned its lens towards WASP’s patch of the galaxy — some 1,400 light-years away — to find that this hot Jupiter traps at least 94 percent of the visible starlight falling into its atmosphere.

The day side of the planet, called WASP-12b, eats light rather than reflects it into space. Credit: NASA, ESA, and G. Bacon (STScI).

The day side of the planet, called WASP-12b, eats light rather than reflects it into space. Credit: NASA, ESA, and G. Bacon (STScI).

Hot Jupiters are gas giants that orbit extremely close to their parent stars. Being in such proximity, their orbital period is very short, typically less than 10 days. In WASP-12b’s case, it takes 1.09 Earth days to complete a full revolution. That’s around the main yellow dwarf star, since WASP is actually a trinary system and further includes two red dwarf stars, each roughly 37 percent and 38 percent of the sun’s mass, respectively.

Orbiting so close to the planet also forced WASP-12b into a tidal lock, with one side always facing the sun while another is shrouded, just like our moon. On the day side of the planet, the surface gets blistering hot sitting at roughly 2,500°C (4,600 degrees Fahrenheit), enough to melt some metals.

A light eater

The day side is so hot it can’t possibly sustain any clouds, so the extremely intense light emanating from WASP just punches through the planet’s atmosphere where it’s absorbed by hydrogen atoms. Almost nothing is reflected, back making this planet darker than asphalt.

“We did not expect to find such a dark exoplanet,” said Taylor Bell of McGill University and the Institute for Research on Exoplanets in Montreal, Quebec, Canada. “Most hot Jupiters reflect about 40 percent of starlight.”

The dark side of WASP-12b is a different matter altogether, as one would expect. It’s a full 1,090°C (2,000 degrees Fahrenheit) colder than the day side, a temperature still really high, but low enough to allow cloud formation. Previously, observations of the day-night interface detected evidence of water vapor and possibly clouds and hazes in the atmosphere.

All of this goes to show that there’s still much we don’t know about hot Jupiters. Right now, anything between 2,500°C (4,600 degrees F) and 1,200°C (2,200 degrees F) is considered a hot Jupiter, and WASP-12b falls like an arc between these limits with its day-night sides.

WASP-12b also comes as a friendly reminder that exoplanets come in all colors. Previously, Hubble detected another hot Jupiter with a glowing water atmosphere. Another Jupiter-like world called HD 189733b is a deep cobalt blue that’s reminiscent of Earth’s color as seen from space. Now, black is on the palette too.

Scientists find water clouds and exotic, primitive atmosphere on a “warm Neptune”

It’s a type of planet which we didn’t even know existed — a Neptune-sized planet closer to a star than its namesake.

Artistic representation of the newly discovered “warm Neptune.” Image credits: NASA/GSFC.

A pioneering new study has revealed what astronomers believed to be evidence of water vapor and exotic clouds around a planet located some 437 light-years away from Earth. The planet, called HAT-P-26b, is a so-called warm Neptune — a Neptune-sized gas giant orbiting very close to its sun, which makes it much hotter. The new study also showed that the planet has an atmosphere composed almost entirely of hydrogen and helium, something which was even more unexpected.

“This exciting new discovery shows that there is a lot more diversity in the atmospheres of these exoplanets than we have previously thought,” David Sing, an astrophysics professor at the University of Exeter in England, said in a statement.

The chemical composition indicates a primitive atmosphere. Researchers believe that, compared to the gas giants in our own solar neighborhood, this planet either developed later in the history of its solar system, closer to its star — or both. It’s a quirk, but it’s a quirk which can be very useful. It kind of breaks the pattern we’ve been seeing in other, similar planets, and this allows astronomers to look at such planets in a new light and better understand the formation and evolution of different solar systems.

“Astronomers have just begun to investigate the atmospheres of these distant Neptune-mass planets, and almost right away, we found an example that goes against the trend in our Solar System,” says one of the researchers, Hannah Wakeford from NASA’s Goddard Space Flight Centre. “This kind of unexpected result is why I really love exploring the atmospheres of alien planets.”

The study itself didn’t employ any new technique. Basically, when the planet passes between its star and the Earth, a fraction of the light emitted by its star is captured and filtered by its atmosphere — but only for some wavelengths. By analyzing the wavelengths of the light which manages to reach us, we can infer the composition of the atmosphere. However, the study was innovative in the sense that it applied the technique to a much smaller planet than previous efforts. This was facilitated by the unusual orbit of the planet — the fact that it’s so close to its star. HAT-P-26b completes a full rotation around in star in just 4.23 days, which makes such observations much easier.

“This ‘warm Neptune’ is a much smaller planet than those we have been able to characterize in depth, so this new discovery about its atmosphere feels like a big breakthrough in our pursuit to learn more about how solar systems are formed, and how it compares to our own,” added Sing, the co-leader of a new study about HAT-P-26b that was published online today (May 11) in the journal Science.

So how would the sky of this alien planet look like? If you were looking through the water clouds, you’d likely see a washed-out, gray sky. While there is some water vapor, the clouds are much more exotic, likely made of disodium sulfide. These clouds would cause scattering in all colors, which is why you’d likely end up with a grayscale sky.

In recent years, telescope and telescope arrays such as NASA’s Kepler have revealed several intriguing planets, greatly expanding our understanding of alien worlds and their solar systems. The variety we are seeing is staggering and sometimes unexpected, but studies like this go a long way towards helping astronomers understand this variety.

Journal Reference: H.R. Wakeford el al., “HAT-P-26b: A Neptune-mass exoplanet with a well-constrained heavy element abundance,” Science (2017).

Water detected in a planet outside our solar system

Astronomers have recently discovered water in the atmosphere of a planet outside our solar system, using a novel technique – they believe that this new method could reveal more and more planets which feature water; so far, all life as we know it, is based on water. They made their discovery on a Jupiter-like planet that is orbiting the nearby star tau Boötis.

An artist’s conception of a hot-Jupiter extrasolar planet orbiting a star similar to tau Boötes. Credit: David Aguilar, Harvard-Smithsonian Center for Astrophysics

Researchers had already discovered water vapor on a handful of planets – but there were only two ways of doing this, both pretty limited:

– the first one worked only if the studied planet has an orbit that passes it in front of its star, when viewed from Earth.
– the other method worked only if he planet is sufficiently far away from its host star.

Needless to say, most of the exoplanets don’t fill into either of these categories – so it was virtually impossible to find water.

Chad Bender, a research associate in the Penn State Department of Astronomy and Astrophysics and a co-author of the paper, talked about their discovery:

“We now are applying our effective new infrared technique to several other non-transiting planets orbiting stars near the Sun,” Bender said. “These planets are much closer to us than the nearest transiting planets, but largely have been ignored by astronomers because directly measuring their atmospheres with previously existing techniques was difficult or impossible.” With the new detection technique and more-powerful future telescopes such as the James Webb Space Telescope and the Thirty Meter Telescope, the astronomers expect to be able to examine the atmospheres of planets that are much cooler and more distant from their host stars, where liquid water is even more likely to exist.

Tau Boötis b is an extrasolar planet approximately 51 light-years away – while extremely far away per se, it’s relatively close in astronomic terms; it is one of the very first exoplanets ever discovered. It’s a so-called hot Jupiter, with a mass approximately 4 times larger than that of Jupiter, and it orbits its star in a so-called “torch orbit”, at a distance from the star less than one seventh that of Mercury’s from the Sun. An orbital revolution (a “year”) takes only 3 days 7.5 hours to complete. Although it hasn’t been directly calculated, it seems very safe to assume that the planet is made of gas, and it also seems extremely unlikely that the planet holds life – the estimated temperature is over 1.300 degrees Celsius (over 2400 Fahrenheit).

“Planets like tau Boötes b, which are as massive as Jupiter but much hotter, do not exist in our solar system. Our detection of water in the atmosphere of tau Boötes b is important because it helps us understand how these exotic hot-Jupiter planets form and evolve. It also demonstrates the effectiveness of our new technique, which detects the infrared radiation in the atmospheres of these planets.”

Bender is leading a larger project to characterize the atmospheres of many hot-Jupiter extrasolar planets. Hopefully, as they develop and refine the technique more and more, they will be able to apply it to more Earth-like planets – ultimately, discovering which planets have the biggest chances of hosting life.

Journal Reference:

  1. Alexandra C. Lockwood, John A. Johnson, Chad F. Bender, John S. Carr, Travis Barman, Alexander J. W. Richert, Geoffrey A. Blake. Near-IR Direct Detection of Water Vapor in tau Boötis b. The Astrophysical Journal, 2014; 783 (2): L29 DOI: 10.1088/2041-8205/783/2/L29
Hot-Jupiter exoplanet illustration. (c) NASA

Signs of water found in the atmosphere of 5 alien planets

Hot-Jupiter exoplanet illustration. (c) NASA

Hot-Jupiter exoplanet illustration. (c) NASA

Using the Hubble telescope, astronomers have identified faint signals of water in the atmosphere of five exoplanets. The alien planets, however, are classed as hot-Jupiters – huge planets with a surface temperature too hot to support life. Finding water on planets light years away from Earth is definitely of great note and marks a step forward in scientists’ quest (and whole of mankind for that matter) of discovering life supporting planets outside our solar system and alien life itself.

With the help of Hubble’s Wide Field Camera 3, NASA researchers closely followed five planets: WASP-17b, HD209458b, WASP-12b, WASP-19b and XO-1b. All of these planets are extremely far away, as you can imagine, so naturally analyzed the light absorbed by the atmosphere of these planets to see what it’s made of. Light can tell you a great deal about the chemical composition of a planet as certain wavelengths are absorbed by certain molecules only – this method is called spectroscopy.

[RELATED] Most Earth-like planet in terms of size and mass discovered

All five planets showed signs of water in their atmosphere, with the strongest signatures found in WASP-17b and HD209458b, as reported in two separate studies published by NASA researchers in the Astrophysical Journal.

“We’re very confident that we see a water signature for multiple planets,” Avi Mandell, of NASA’s Goddard Space Flight Center in Greenbelt, Md., lead author of one of the studies, said in a statement. “This work really opens the door for comparing how much water is present in atmospheres on different kinds of exoplanets — for example, hotter versus cooler ones.”

This isn’t the first time signs of water have been found in the atmosphere of distant worlds, however the two studies mark the first time researchers measured and compared profiles of the substance in detail across multiple alien worlds. For all planets, the water signature was fainter than expected, based on previous observations with Spitzer, possibly due to hazes absorbing in the NIR or non-solar compositions.

[ALSO READ] First cloud-map of an extrasolar planet

Faint or not, it’s highly likely that water is present in the air of these worlds. It’s little steps like these that might eventually help scientists refine their methods and lead to the milestone discovery we’re all waiting for.

“These studies, combined with other Hubble observations, are showing us that there are a surprisingly large number of systems for which the signal of water is either attenuated or completely absent,” Heather Knutson of the California Institute of Technology in Pasadena, a co-author on Deming’s paper, said in a statement. “This suggests that cloudy or hazy atmospheres may in fact be rather common for hot Jupiters.”

First cloud map of an extrasolar planet

Astronomers have created the first cloud map of a planet outside our solar system, a sizzling, Jupiter-like world known as Kepler-7b.

Kepler-7b (left), which is 1.5 times the radius of Jupiter (right), is the first exoplanet to have its clouds mapped.

Kepler-7b (left), which is 1.5 times the radius of Jupiter (right), is the first exoplanet to have its clouds mapped.

NASA’s Kepler and Spitzer space telescopes found patchy clouds on this hot Jupiter which was discovered in January 2010. Hot Jupiters are some of the most common planets from what we know so far; they are gas giants just like Jupiter, but they have high surface temperatures because they orbit very close to the Sun (tipically 2 – 7 times closer than the Earth), which makes them very bright and relatively easy to study.

Kepler-7b is marked by high clouds in the west and clear skies in the east.

“By observing this planet with Spitzer and Kepler for more than three years, we were able to produce a very low-resolution ‘map’ of this giant, gaseous planet,” said Brice-Olivier Demory of Massachusetts Institute of Technology in Cambridge. Demory is lead author of a paper accepted for publication in the Astrophysical Journal Letters. “We wouldn’t expect to see oceans or continents on this type of world, but we detected a clear, reflective signature that we interpreted as clouds.”

Like Kepler, Spitzer can fix its gaze at a star system as a planet orbits around the star, gathering clues about the planet’s atmosphere; it is able to detect infrared light, and thus it was able to measure Kepler-7b’s temperature, estimating it to be between 815 and 980 degrees Celsius (1,500 and 1,800 degrees Fahrenheit). Interestingly, this is a very low temperature for a planet which orbits its Sun-like star 16 times closer than the Earth.

“Kepler-7b reflects much more light than most giant planets we’ve found, which we attribute to clouds in the upper atmosphere,” said Thomas Barclay, Kepler scientist at NASA’s Ames Research Center in Moffett Field, Calif. “Unlike those on Earth, the cloud patterns on this planet do not seem to change much over time — it has a remarkably stable climate.”

The method shows promise in studying earth-like planets and their atmosphere.

“With Spitzer and Kepler together, we have a multi-wavelength tool for getting a good look at planets that are trillions of miles away,” said Paul Hertz, director of NASA’s Astrophysics Division in Washington. “We’re at a point now in exoplanet science where we are moving beyond just detecting exoplanets, and into the exciting science of understanding them.”

nasa eyes

Explore all 900-plus exoplanet discoveries with NASA’s “Eyes on Exoplanets,” a fully rendered 3D visualization tool, available for download at http://eyes.nasa.gov/exoplanets. The program is updated daily, and it’s a simply brilliant tool for those passionate about space exploration and astronomy.

For the first time, researchers discover true color of distant planet

The world, known as HD189733b, has a deep azure hue, probably the result of molten silicate glass rain in the atmosphere, which scatters blue light.

blue planet

The giant planet is one of the closest and most studied in the exoplanets recently discovered; it is a sauna, a hazy hothouse swept by blow-torch winds powered by the molten silicates. It is most likely what astrophysicists call a “hot Jupiter” – a planet which originally was very similar to Jupiter, both in terms of composition and distance to its star, but then migrated much closer to its star.

Astronomers used the Hubble’s imaging spectrograph and measured both the light emitted by the star which it orbits, and the light reflected by the planet. To isolate the planet’s light, they substracted one from the other, though the process is not nearly as simple as it sounds.

“We inferred the color,” said astrophysicist Tom Evans at the U.K.’s University of Oxford, who led the study. By knowing the wavelength, “we can imagine the color the planet would have if we could look at it with our own eyes.”

It’s estimated that the temperature on the surface of the planet is a whopping 1000 C (1832 F) with winds howling at 7000 km/h (4349 miles/h). It’s atmosphere is extremely volatile, changeable and exotic, with hazes and violent bursts of evaporation. Not the habitable paradise Earth is.

So our planet appears blue from outer space due to the oceans, which absorb red and green wavelengths more strongly than blue ones. To accentuate the effect, scattered molecules of oxygen and nitrogen in the atmosphere also selectively absorb wavelengths. Mars appears red due to its rusty surface, very rich in oxide, absorbing the blue and green wavelengths and reflecting the red ones. But the color of HD 189733b comes solely from the interplay of light in its super-heated atmosphere.

The fact that astronomers were able to measure this is a stunning achievement in itself.

“We are really pushing the limits of what we can measure,” said Mr. Evans.

Stars don’t consume their planets – usually

Stars have a pull on all planets, but they exhibit a special kind of attraction towards a class of planets called ‘Hot Jupiters‘.

hot jupiter

Hot Jupiters, also called roaster planets or pegadisds are a class of extrasolar planets very similar to Jupiter, but which have very high temperatures because they orbit very close to the Sun. It is thought that all of these planets have migrated from the extremities of the solar system to their current position because there would not have been enough material so close to the star for a planet of that mass to have formed so close to its star.

So they’re formed far away from their star, and then they start getting closer; and closer… and closer! Logic tells you, as they move closer to the star, the gravitational attraction increases, and they will probably end up in eaten by the star. But a new study using data from NASA’s Kepler Space Telescope shows that hot Jupiters are in fact not often consumed by their stars – instead, remaining stable for several billions of years.

“Eventually, all hot Jupiters get closer and closer to their stars, but in this study we are showing that this process stops before the stars get too close,” said Peter Plavchan of NASA’s Exoplanet Science Institute at the California Institute of Technology, Pasadena, Calif. “The planets mostly stabilize once their orbits become circular, whipping around their stars every few days.”

The study, which was published in the Astrophysical Journal, is the first to show that hot Jupiter planets halt their inward march on stars, stabilizing an orbit as the migration ceases.

“When only a few hot Jupiters were known, several models could explain the observations,” said Jack Lissauer, a Kepler scientist at NASA’s Ames Research Center, Moffet Field, Calif., not affiliated with the study. “But finding trends in populations of these planets shows that tides, in combination with gravitational forces by often unseen planetary and stellar companions, can bring these giant planets close to their host stars.”

The full paper can be read here.


An artist impression of one of the two gas giants discovered orbiting a sun-like star, part of a star cluster. (c) NASA/JPL-Caltech

First evidence of planet formation around sun-like stars in clusters

An artist impression of one of the two gas giants discovered orbiting a sun-like star, part of a star cluster. (c) NASA/JPL-Caltech

An artist impression of one of the two gas giants discovered orbiting a sun-like star, part of a star cluster. (c) NASA/JPL-Caltech

Astronomers, financially backed by NASA, have for the first time ever discovered tantilizing evidence that planets can form and exist around sun-like stars, densly packed together in star clusters. The finding is of significant importance, as scientists claim that it shows that planet can indeed exist in extremely harsh environments, like star clusters.

The two planets, Pr0201b and Pr0211b, were discovered each circling their own sun-like star in the Beehive Cluster, also known as the Praesepe – a cluster containing more than 1000 stars very close to one another which orbit around a center. The planets, discovered and analyzed by the 1.5-meter Tillinghast telescope located at the Smithsonian Astrophysical Observatory’s Fred Lawrence Whipple Observatory near Amado, Arizona, are not habitable – far from it.

The planets are in class called Hot Jupiters, massive gas giants with boiling hot environments, because of a very tight orbit.

“We are detecting more and more planets that can thrive in diverse and extreme environments like these nearby clusters,” says Mario R Perez, NASA astrophysics program scientist in the Origins of Solar Systems Program.

“Our galaxy contains more than 1,000 of these open clusters, which potentially can present the physical conditions for harboring many more of these giant planets.”

These aren’t the first planets discovered orbiting around stars in a cluster, however they’re the first to be found orbiting around stars similar to our sun. The astronomers involved in the study hope this latest discovery might help answer how hot Jupiters wind up so close to their stars. Also, it offers proof that planets can form in harsh environments.

“This has been a big puzzle for planet hunters,” says Sam Quinn, a graduate student in astronomy at Georgia State University.

“We know that most stars form in clustered environments like the Orion nebula, so unless this dense environment inhibits planet formation, at least some sun-like stars in open clusters should have planets. Now, we finally know they are indeed there.”


Extrasolar hot Jupiter sheds some light on our own solar system

Since 1995, over 500 planets that don’t orbit our Sun have been discovered, with the numbers increasing more and more in the past years. But only recently did astrophysicists observe that in some of these cases, the star seems to be spinning in one direction, and the planet orbits it in the totally opposite direction – totally counterintuitive and against what we generally believe about planetary formation.

“That’s really weird, and it’s even weirder because the planet is so close to the star,” said Frederic A. Rasio, a theoretical astrophysicist at Northwestern University. “How can one be spinning one way and the other orbiting exactly the other way? It’s crazy. It so obviously violates our most basic picture of planet and star formation.”

The size and proximity to the star is what led to the ‘hot Jupiter’ name, but aside from this information, researchers didn’t really know that much about them; so they set out to study what can cause such a flipped rotation, and why these hot Jupiters have such close orbits.

“Once you get more than one planet, the planets perturb each other gravitationally,” Rasio said. “This becomes interesting because that means whatever orbit they were formed on isn’t necessarily the orbit they will stay on forever. These mutual perturbations can change the orbits, as we see in these extrasolar systems.”

The thing is, typically enough, astrophysicists have considered our solar system to be typical for the Universe, but observations don’t seem to confirm this belief.

“We had thought our solar system was typical in the universe, but from day one everything has looked weird in the extrasolar planetary systems,” Rasio said. “That makes us the odd ball really. Learning about these other systems provides a context for how special our system is. We certainly seem to live in a special place.”

The physics they used to solve this issue is basically orbital mechanics, but the approach they needed, and the amount of detail and successful approximation is absolutely stunning.

“It was a beautiful problem,” said Naoz, “because the answer was there for us for so long. It’s the same physics, but no one noticed it could explain hot Jupiters and flipped orbits.”

“Doing the calculations was not obvious or easy,” Rasio said, “Some of the approximations used by others in the past were really not quite right. We were doing it right for the first time in 50 years, thanks in large part to the persistence of Smadar.”

Of course, a computer model was necessary, but the steps that have to be taken until that computer model are the most important. It takes a sharp mind, and a correct approach to take everything from paper and put it on a hard disk.

“It takes a smart, young person who first can do the calculations on paper and develop a full mathematical model and then turn it into a computer program that solves the equations,” Rasio added. “This is the only way we can produce real numbers to compare to the actual measurements taken by astronomers.”

In their model, they created a simple solar system with a star similar to the Sun and two planets; one of them is a Jupiter-like planet that forms far from the star, where this kind of planets are thought to form. The other planet is even farther away from the sun than the inner planet, and it interacts gravitationally with it, shaking the whole system.

The effects of this model are the exact ones they were trying to get: the inner gas giant moves closer and closer towards the Sun and starts orbiting in the opposite direction of the star’s spin. These changes occur because (according to the model) the two orbits are exchanging angular momentum, and the inner one loses energy via strong tides. The gravitational couple forces the inner planet to adopt an eccentric, needle-like orbit; in order for this to happen, it has to lose a lot lot of angular momentum, giving it away to the outer planet, and thus its orbit gradually shrinks because of all the dissipated energy, pulling it closer and closer to the star, and sometimes flipping its orbit in the process.

Astronomers upset the theory of planetary formation

The discovery of 9 new planets raises some serious questions on the matter of how planets are formed. Two astronomers from the University of California, Santa Barbara reported the discovery, and of them, two are spinning in the opposite direction the planets in our solar system are spinning. This, along with other recent studies of exoplanets (planets outside the solar system) seems to put the final nail in the primary theory regarding planetary formation.


Artistic illustration of a Hot Jupiter

This was the highlight at the UK National Astronomy Meeting in Glasgow, Scotland that took place this week, and now researchers from this field will have a whole lot of work to do, basically starting from scratch (almost).

“Planet evolution theorists now have to explain how so many planets came to be orbiting like this,” said Tim Lister, a project scientist at LCOGT. Lister leads a major part of the observational campaigns along with Rachel Street of LCOGT, Andrew Cameron of the University of St. Andrews in Scotland, and Didier Queloz, of the Geneva Observatory in Switzerland.

The 9 planets are pretty interesting by themselves too; they are so-called “Hot Jupiters”. As you could guess by the name, they are giant gas planets that orbit quite close to their star (which is of course why they’re hot). Since this type of planet was discovered no more than 15 years ago, their origin has remained a mystery. However, they are quite easy to detect due to the gravitational effect they have on their star.

The general belief is that at their cores, these planets have a mix of rock and ice particles found only in the cold outer reaches of planetary systems. The logical conclusion is that Hot Jupiters have to form quite far away from their star and then migrate closer as millions of years pass. Numerous astronomers believed this happens due to the interactions the planets have with the dust cloud from which they are formed. However, this idea does not explain why they orbit in a direction contrary to that of the disk.

Another theory suggests that it was not interaction with the disk at all, but rather a slower evolution that was affected by gravitational relationships with more distant planetary or stellar companions over hundreds of millions of years. It would probably be imposed an elongated orbit and would suffer have a “tidal” movement, until it was parked in a more circular orbit close to the star.

“In this scenario, smaller planets in orbits similar to Earth’s are unlikely to survive,” said Rachel Street.