Category: Extrasolar Planets

Our Solar System has 8 planets, but another, 55 Cancri, is catching up fast. Astronomers today announced the discovery of a 5th planet in the system, located 41 light-years away. This newly discovered planet weighs in with 45 times the mass of the Earth, and might look similar to Saturn in composition and appearance. But the news gets better, it’s in the star’s habitable zone, and could have water-covered moons.

The discovery of a 5th planet around 55 Cancri was made by astronomers from UC Berkeley, and several other collaborating universities, with funding from NASA and the National Science Foundation. Their research will appear in an upcoming issue of the Astrophysical Journal.

Astronomers used the radial velocity technique to find the planets. This is where the velocity of the star is carefully measured. Periodic changes in this velocity mean that a large planet’s gravity is yanking the star back and forth. In this case, the discovery was even more difficult, because there were already known planets in the system, polluting the data.

“It is amazing to see our ability to detect extrasolar planets growing,” said Alan Stern, associate administrator for the Science Mission Directorate at NASA Headquarters, Washington. “We are finding solar systems with a richness of planets and a variety of planetary types comparable to our own.”

Perhaps the coolest part of this whole discovery: the planet orbits its parent star once every 260 days. This places it within its star’s habitability zone, where liquid water can be present. It’s a little closer than our Earth is to the Sun, but its star is also a little fainter, so it all evens out.

Obviously, this rules out the planet itself, but it could have a collection of moons, just like Saturn. Instead of Saturn’s icy moons, this 5th planet of 55 Cancri could have ocean moons.

Finding this planet was an enormous challenge. The discoverers have been making observations of 55 Cancri for 18 years, before the first extra solar planets were ever found. They had to make more than 320 velocity measurements to disentangle the 5 planets from the data.

Original Source: NASA/JPL News Release

You know the science of planet hunting is getting mainstream when there’s very little fanfare for the discovery of 3 new extrasolar planets with the size of Jupiter. 3 new planets people! They’re named WASP-3, WASP-4, WASP-5, and were discovered by a European team of astronomers using observatories in South Africa and the Canary Islands.

The new planets were discovered using the SuperWASP instruments. These are high speed cameras affixed to two telescopes: SuperWASP-North at Roque de los Muchachos Observatory on the island of La Palma in the Canaries and SuperWASP-South at the South African Astronomical Observatory, South Africa. Both instruments are equipped with a detailed CCD camera array capable of monitoring up to 400,000 stars every minute.

They’re watching to see if any of those stars vary in brightness. If a star does get brighter and dimmer over a regular period, the astronomers can then determine if a planet is passing in front – an event known as a transit (or eclipse). Just by measuring the dimming, astronomers can then determine the size of the planet, and even some of its chemical constituents.

With this latest discovery, the three new planets all contain roughly the mass of Jupiter, but orbit much closer into their parent stars. They complete an orbit every 2 two days.

According to one of the discoverers, Dr Don Pollacco of Queen’s Astrophysics Research Centre, “these are among the shortest orbital periods yet discovered. Being so close to their star, the surface temperatures of the planets will be more than 2000 C, so it is unlikely that life as we know it could survive there. However, the finding of Jupiter-mass planets around other stars supports the idea that there are also many Earth-sized planets waiting to be discovered as the technology employed by astronomers improves.â€?

Even a relatively tiny planet the size of the Earth should visibly dim the light from a star as it passes in front. This is an exciting technique that should just get better and better over time.

Original Source: University of St. Andrews News Release

Science fiction writers have been imagining other worlds for years, and now they’re going to get a little scientific help, thanks to NASA. The agency recently modeled a range of roughly Earth-sized planets, from the familiar to the exotic. Instead of thinking just about planets with Earthlike characteristics, they imagined every possible kind of planet that might exist around other worlds. This should keep the writers busy.

We’re not talking about familiar looking planets, with strange surface features and aliens with pointed ears here, we’re talking about the very extremes of planetary formation: pure water ice, carbon, iron, silicate, carbon monoxide, and silicon carbide, and others which could be mixtures of these various compounds.

The team eventually came up with 14 different types of solid planets that might exist. “We have learned that extrasolar giant planets often differ tremendously from the worlds in our solar system, so we let our imaginations run wild and tried to cover all the bases with our models of smaller planets,” said NASA’s Marc Kuchner. “We can make educated guesses about where these different kinds of planets might be found. For example, carbon planets and carbon-monoxide planets might favor evolved stars such as white dwarfs and pulsars, or they might form in carbon-rich disks like the one around the star Beta Pictoris. But ultimately, we need observations to give us the answers.”

They calculated how gravity should compress planets of varying composition. For example, a pure water planet would be about the same size as the Earth, while an iron planet would be a third our size.

The researchers are hoping their calculations will help future planet hunters identify new discoveries. When powerful planet finders, such as ESA’s Corot mission start making discoveries, astronomers will be working hard to categorize what they’re looking at, based only on the mass and size. Even more powerful observatories, such as the James Webb Space Telescope will let astronomers actually measure the chemical constituents of a planet, and help reveal if we’re looking at a sphere of carbon or water ice.

Their paper will appear in the October 20th issue of the Astrophysical journal.

Original Source: NASA News Release

When a star like our own Sun nears the end of its 10 billion year life, it expands up into a red giant, consuming any planets foolish enough to orbit closely. But what happens to the more distant planets? Astronomers have discovered just such a planet, orbiting a red giant star. Perhaps this gives us hope for the fate of our own planet Earth, when the Sun expands too. Not so fast.

An international team of astronomers from 15 different countries announced the planetary discovery, and their article will be published in the September 13th edition of the journal Nature.

The planet is called V 391 Pegasi b, and before its parent star transformed into the red giant we see today, it orbited at roughly the same distance as the Earth. As the star expanded, its centre of gravity changed, and the planet’s orbit spiraled outward, keeping pace with the changing star. Although the star now engulfs a distance comparable between the Sun and the Earth, the planet is now out past the orbit of Mars; takes 3.2 years to complete a full year.

So does this mean the Earth’s safe? Not so fast. Here’s one of the researchers, Steve Kawaler from Iowa State University:

“We shouldn’t take too much heart in this – this planet is larger than Jupiter, so a smaller planet like the Earth could still be vulnerable. As far as our planets are concerned, we expect Mercury and Venus to disappear in the Sun’s envelope, whereas Mars should survive. The fate of the Earth is less clear because its position is really at the limit: it appears more likely that the Earth will not survive the red giant expansion of the sun either, but it is not for sure.”

Finding this planet was incredibly laborious work. It took seven years of observations and calculations to confirm its existence. It also marks the first time that a new technique was used to discover planets. Traditionally, astronomers measure the change in a planet’s velocity as it’s yanked back and forth by the gravity of a large planet using a technique called spectroscopy, where the spectrum of its light shifts. In the case of V391 Pegasus b, the astronomers measured small variations in timing of light coming from the star to determine its velocity.

Original Source: University of Delaware News Release

Ever wonder how the Earth got its oceans? Well, new data gathered by NASA’s Spitzer Space Telescope could provide a clue. The telescope imaged a planetary disk forming around a young star, surrounded by a cloud of water vapour. This water is raining down right into the dusty disk where planets are thought to form.

Now that’s convenient.

The discovery appears in the August 30th edition of the journal Nature. According to the discovering astronomers, there’s enough water vapour located in the star system NGC 1333-IRAS 4B, located about 1,000 light-years away, to fill up the oceans on Earth 5 times over.

Astronomers used to believe that Earth’s water arrived early on in our Solar System’s formation in the form of icy comets. The early Earth was bombarded by comets large and small, and our oceans slowly built up over time. But this research indicates that water falling as ice will actually vapourize as it arrives from the stellar envelope to its disk.

The discovering team studied a total of 30 stellar embryos, using Spitzer’s infrared spectrograph, which can peer through obscuring dust. Of all the systems they analyzed, only one had such a strong signature of water. The vapour was easy to spot for Spitzer because when the ice falling from the envelope into the planet-forming disk, it heats up, glowing with infrared light.

Is this a rare situation? The astronomers believe the water signature was so bright because the star system is perfectly lined up for Spitzer to be able to see its bright core. It’s also probably that this phase of planetary formation is very short lived, so the other systems have already gone through this phase, or will do so shortly.

Original Source: NASA/JPL/Spitzer News Release

An international team of astronomers announced today that they have discovered the largest extrasolar planet; it’s 70% larger than Jupiter. Amazingly, this new planet, dubbed TrES-4 is actually less massive than Jupiter. With the large size, and lower mass, the planet has a low density. You might call it fluffy.

The discovery of TrES-4 was made by astronomers working with the Trans-atlantic Exoplanet Survey. This is network of small automated telescopes in Arizona, California, and the Canary Islands designed to carefully measure the amount of light coming from stars. A periodic dimming and brightening is a candidate for a transiting planet, changing the light from its star as it moves by.

TrES-4 has a density of 0.2 grams per cubic centimetre. That works out to be less than the density of balsa wood. It would easily float in water if you had a large enough pool.

The planet is located about 1,400 light-years away, and orbits its host star in 3.5 days. This puts it into the hot Jupiter classification, orbiting only 7.2 million km (4.5 million miles) from its star, and reaching a temperature of 1,600 Kelvin (2,300 degrees F).

How did a planet with so little mass get so large? Good question.

“TrES-4 appears to be something of a theoretical problem,â€? said Edward Dunham, Lowell Observatory Instrument Scientist. “It is larger relative to its mass than current models of superheated giant planets can presently explain. Problems are good, though, since we learn new things by solving them.”

To capture transiting planets, the network of telescopes take wide-field timed exposures of clear skies on as many nights as possible. Astronomers then measure the amount of light coming from every single star in the field to detect if any have changed in brightness. In the case of TrES-4, it dims the amount of light received by the star by about 1%. It’s not a lot, but the telescopes and observing techniques can tease the data out.

Once the astronomers had a candidate discovered with the TrES network, they switched from the 10-cm telescopes they were using to the powerful 10-metre W.M. Keck telescopes atop Mauna Kea, Hawaii. They also made follow up observations with the Lowell Observatory and Fred L. Whipple Observatory in Arizona.

Original Source:Lowell Observatory News Release

Here in the Solar System, we’ve only got one star: the Sun. That gives us nice predictable daily and annual cycles; night and day, the seasons, that sort of thing. Astronomers have found a newly forming extrasolar planetary system that has 4 stars. The discovery, made using NASA’s Spitzer Space Telescope, revealed a dusty disk surround a pair of stars in the quadruple-star system HD 98800.

The system itself is pretty complicated, so bear with me as I try to explain it. There are two pairs of binary stars; 2 + 2 = 4 stars in total. These two binary groupings are separated by 50 astronomical units (AU); approximately the distance between the Sun and Pluto. Around one of these binary pairs, astronomers discovered two belts of material.

The first belt sits at approximately 1.5 to 2 AU (twice the distance from the Sun to the Earth), and seems to consist of fine grains of dust. The second belts is further out at approximately 5.9 AU and is probably made up of asteroids or comets.

When astronomers see gaps in disks of material, their first instinct is to assume planets cleared them out. In this situation, however, they can’t rule out the complex interaction between the 4 stars. Collisions caused by objects in the asteroid belt should migrate inward to the inner disk; however the particles don’t evenly fill out the inner disk as expected.

Some day, future inhabitants of this world might look out their alien windows and see two bright suns, and two dimmer ones together in the sky. And every once in a while, all the suns would dip down to the horizon at roughly the same time.

The sunsets would be spectacular.

Original Source: Spitzer News Release