Extrasolar Planets Archives

August 17, 2007December 26, 2015 by Fraser Cain

Dead Star Found Polluted By Earthlike Planet

Astronomers have found a burned out white dwarf star with the remants of an Earthlike planet orbiting it. This chemical fingerprint gives hope that terrestrial planets, like the ones in our Solar System, could be common across the Universe. Now we just need to find some that havn’t been pulverized into planet powder.

The white dwarf star surrounded by planetary remains is called GD 362, and it’s located about 150 light-years from Earth. Although it’s a dying star, it has a ringlike structure around it like Saturn. During their observations, astronomers from UCLA captured the distinct signature of a rocky asteroid interacting with the white dwarf.

At some point in the recent past, an asteroid was torn apart by the powerful gravitational forces around the compact object, and the dust has polluted the white dwarf’s atmosphere. The relative abundances of elements match the chemical constituents of the planets in the inner Solar System.

Here’s a comment from Michael Jura, a UCLA professor and co-author of the research:

“What we have here is a composition of the white dwarf that is fairly similar to that of the inner planets of our solar system. Are there other terrestrial planets like Earth in other solar systems? This white dwarf’s fingerprint is a significant advance in demonstrating that something like terrestrial planet formation occurred around this other star and probably occurred around other stars as well, because it suggests the Earth’s composition is not unique.”

With this discovery, astronomers have evidence that the kinds of forces that made the Earth and planets in our Solar System happened around GD 362, back when it was a newly forming star. And it gives us a glimpse into the future fate of our planet.

In approximately 5 billion years, when our Sun starts to run out of hydrogen fuel, it will expand out enormously, consuming the inner planets, and maybe even the Earth. The change in the Sun’s density will affect the orbits of all the remaining planets. Some may spiral inward and be consumed by the Sun. Others may spiral outward into interstellar space. Others may collide into smaller and smaller objects. Eventually, our Sun may have its own ring of leftover planetary material. And one of those chunks might be a piece of the Earth.

Original Source: UCLA News Release

August 7, 2007December 26, 2015 by Fraser Cain

Large, Fluffy Planet Darkens a Distant Star

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

July 30, 2007December 26, 2015 by Fraser Cain

Imagine a View with Four Sunsets

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

July 19, 2007December 26, 2015 by Fraser Cain

Lopsided Disk Around a Young Star

If you look at drawings of our Solar System, you’ll notice all the planets are lined up nicely in a flat plane, and their orbits are roughly circular. If you can imagine the disk of material that the planets formed out of, it would have been a circle surrounding our Sun. And this circular shape is what astronomers have been seeing when they discover planetary debris disks around other stars.

Until now.

Using the Hubble Space Telescope, and the W.M. Keck Observatory, astronomers have turned up a young system where the star and its planetary disk of debris aren’t lined up. From our perspective here on Earth, the disk is seen edge-on, jutting out to one side of the star in an elliptical orbit.

What could have caused this situation? Astronomers think that the disk’s odd lopsided look is caused by dust following a highly elliptical orbit around the star. Perhaps its the gravitational interaction with planets sweeping up material, or maybe the system had an encounter with a nearby star that yanked the debris disk out on one side.

This discovery could help explain possible planetary upheavals in our own Solar System. For example, astronomers think that Neptune formed in between the orbits of Saturn and Uranus, and then something kicked it out to its current position.

Original Source:HubbleSite

July 17, 2007December 26, 2015 by Fraser Cain

Large Outer Planets are Rare

One of the big surprises the Universe had in store for extrasolar planet hunters is the number of enormous planets close into their parent stars – the hot Jupiters. Another surprise seems to be how few large planets are found in the outer reaches of a solar system.

The discovery was announced by an international team of astronomers who concluded a three-year survey of 54 young, nearby stars. These should be among the best candidates to have large, Jupiter-sized planets further than 5 astronomical units from their parent stars (1 astronomical unit is the distance from the Earth to the Sun).

They didn’t find a single planet.

Using the European Southern Observatory’s powerful telescopes, such as the 8.2-metre Very Large Telescope (VLT) in Chile, the team had the ability to find outer super Jupiter planets at distances of more than 10 astronomical units from their stars. They had the imaging capability to spot them, but none turned up.

This new data helps astronomers constrain their calculations about where and how giant planets form in other solar systems. They can refine their models to better understand how our own giant planets might have formed.

Original Source: UA News Release

July 12, 2007December 26, 2015 by Fraser Cain

If There’s Oxygen, There’s Life

If aliens visited our Solar System, it would only take them a moment to figure out which planet is the one with all the life on it. That’s because our atmosphere has a high percentage of oxygen in its atmosphere. The presence of oxygen in our atmosphere has given scientists the key to searching for life on other worlds. But what if there are purely natural processes, that could confuse the search for life, fooling powerful new space observatories like the Terrestrial Planet Finder and Darwin.

Don’t worry. A new simulation by a team of US researchers shows that no natural process on a habitable world with liquid water could keep high levels of oxygen and ozone present in an alien atmosphere. If there’s oxygen, there’s life.

Most of the oxygen (O2) in the Earth’s atmosphere was thought to have been generated though photosynthesis. Plants use energy from the Sun, taking in carbon dioxide and releasing O2 as a byproduct. Over time, this oxygen has built up in our atmosphere to its current ratio of 21%, with the rest nitrogen and other trace gases.

This ratio is very important to the search for life in the Universe. Over the next few decades, a fleet of spacecraft and experiments are being built that will be so sensitive, they’ll be able to analyze the atmosphere of a distant Earth-sized world. Find oxygen or ozone in that planet’s atmosphere – so goes the thinking – and you’ve found a world with life. Like our own planet, some organic process is refreshing the oxygen in the atmosphere, stopping it from reacting away.

One recently canceled spacecraft is the Terrestrial Planet Finder, which would be sensitive enough to analyze the chemical constituents of a distant atmosphere. Sadly, this mission was scrapped after budgets were transfered to support the Vision for Space Exploration, which will send humans back to the Moon, and on to Mars. Don’t worry, though, the Europeans are working on the problem too with their Darwin mission. And it hasn’t been canceled… yet.

These missions (if they do get launched) will be able to spot oxygen and ozone in a distant world’s atmosphere. But could they be fooled? Are there natural processes that could generate similar levels of oxygen and ozone? If so, then it would make the search for life extremely difficult, generating false positives that would confuse scientists.

There have been a few scenarios that scientists think might create false positives for life. For example, in a runaway greenhouse planet like Venus, large amounts of hydrogen could be escaping from a hot, moist atmosphere. Since this hydrogen is originating from water (H2O), this would leave oxygen behind. If an extrasolar planet was losing its ocean to space, it might fool the detectors.

In another situation, a frozen, Mars-like planet could be large enough to retain heavy gases, but too small to maintain volcanic outgassing. The frozen surface would then inhibit the loss of oxygen, but also not consume it.

The trick to both of these scenarios, though, is that they would exist on planets outside a star’s habitable zone. Careful observers would be able to rule them out ahead of time.

A team of US researchers has developed a simulation to see if there are scenarios that could generate false positives, and they weren’t able to find anything that would fool future telescopes. The research paper is titled Abiotic Formation of O2 and O3 in High-CO2 Terrestrial Atmospheres, and it was recently accepted into the journal Astronomy & Astrophysics.

They ran many simulations, factoring in all the potential variables that would simulate an Earthlike world, including different rates of volcanic outgassing and ultraviolet radiation.

They weren’t able to come up with any scenarios in which a habitable planet with liquid water could generate a false positive result for O2 or O3 that would fool a telescope like the Terrestrial Planet Finder or Darwin.

Original Source: Arxiv research paper

July 12, 2007December 26, 2015 by Fraser Cain

Water Vapour Discovered in an Extrasolar Planet

Scientists have reported the first conclusive evidence of water vapour in the atmosphere of an extrasolar planet. Before we load up the spaceships to search for life, however, consider the fact that this planet, HD 189733b, is larger than Jupiter, and orbits its parent star in just 2.2 days. That’s hot hot water.

The discovery was made using the mighty Spitzer space telescope. The astronomers pointed Spitzer at the parent star, and measured the chemical consistency of its light as the planet passed in front – aka, transited. As the starlight dimmed – blocked by the planet – the chemical constituents of the star changed to show a distinctive pattern. Astronomers know that only water can absorb these specific wavelengths of infrared radiation.

As I mentioned above, this planet is certainly a “hot Jupiter”. It contains 1.15 the mass of Jupiter (and 1.25 the diameter), but it orbits its parent star at a distance of only 4.5 million km. In comparison, our own Mercury is a distant 70 million km from the Sun.

It’s close, so it’s hot. Its atmospheric temperature is about 1000 Kelvin (more than 700 C). With this heat, all the water vapour in its atmosphere can’t condense, rain or form clouds.

It’s also tidally locked to its parent star, only showing one face to the star at all times (like the Moon and the Earth). This constant facing probably generates fierce winds that sweep around the planet from the day side to the night side.

Like I said, not the best place to find life, but still, an amazing discovery.

Original Source:ESA News Release

June 25, 2007December 26, 2015 by Fraser Cain

Imagining Plants on another Planet

If and when astronomers finally start discovering life on other worlds, they’ll be wondering what kinds of lifeforms are there. They probably won’t have plants as we know them, but there’ll be some kind of life that converts light from the Sun into energy. What would this life look like?

It turns out, the look of the plant life on another planet will depend on the light from the Sun. This is according to new research from Robert Blankenship at Washington University in St. Louis. Plants here on Earth are green because of chlorophyll, which converts solar power into sugars for metabolism. But this isn’t the best molecule. Ideally, you want something black, which absorbs all of the light.

Blankenship is part of a NASA working group at the Jet Propulsion Laboratory. They’re studying the light that comes from stars and extrasolar planets, looking for clues that would hint at extrasolar life. Specifically, they’re looking for elements which are out of balance from what a world should be if it was completely lifeless. For example, here on Earth, the free oxygen in our atmosphere wouldn’t be around if there wasn’t a natural process replenishing it. There’s also a very specific wavelength of light, 700 nanometres out, where there are signs of very intense chlorophyll absorption.

Original Source: Washington University in St. Louis News Release

June 13, 2007December 26, 2015 by Fraser Cain

Hidden Planet Disturbs a Ring of Dust

You can’t see it, but there’s a Neptune-sized planet hidden in a ring of dust around the star Fomalhaut. At least, this is according to new research from the University of Rochester. A recent photograph taken by Hubble shows that this ring around Fomalhaut is slightly off-centre, and nobody knew why, until now.

Protoplanetary rings have been discovered around many newly forming stars. As the star matures, its powerful solar wind kicks in, blowing out all the remaining dust and gas that helped form the planets. In the case of Fomalhaut, this ring is elliptical, with the parent star off to one side.

To give the ring this elliptical shape, researcher Alice Quillen determined that a Neptune-sized planet must be tucked up right against the inner side of this ring. Its gravity is tossing dust in the area out of orbit. How this planet got into an elliptical orbit is a bit of a mystery, though. Usually planets form in nice circular disks, which translate to circular orbits.

Original Source: University of Rochester News Release

June 8, 2007December 26, 2015 by Fraser Cain

Stable Star Gives the Best Chance for Life

One of the biggest news stories of the year was an Earth-sized planet orbiting Gliese 581. Even more importantly, this terrestrial planet is orbiting within the star’s habitable zone, where any water will likely be in liquid form. But it takes more than just water to encourage life, you need a nice, stable star. And according to a new survey, Gliese 581 fits the bill there too.

The survey was done by Canada’s MOST telescope, nicknamed the Humble Space Telescope. It’s a suitcase-sized space observatory with the ability to watch for changes in brightness with incredible sensitivity. MOST focused on Gliese 581 for 6 weeks, watching for any flareups, or drops in light.

According to University of British Columbia researcher, Jaymie Matthews, the brightness of the star only changed a few tenths of a percent during their observations. That means its radiation output remains very stable over time.

So, Gliese 581c has the possibility of liquid water and stable warming from the star. Good news for potential life on this distant planet.

Original Source: UBC News Release