Posts Tagged ‘exoplanets

Astronomers Discover Habitable ExoEarth Orbiting Binary Star

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Red and orange suns would light the skies of the most exotic exo-Earth yet discovered

In recent years, the search for an Earth-like planet orbiting another star has been the most exciting in science. The world has waited with baited breath for the discovery of another Earth.

But the discovery of Earth 2.0 has been a damp squib. Not because astronomers haven’t found one; on the contrary! The problem is they’ve found too many candidates. And these have turned out to be so unlike Earth that it’s hard to imagine that any of them can be a convincing twin.
We’re left, like the starving donkey equidistant between two bails of hay, unable to decide on what to celebrate.
The top candidates so far are these:

Gliese 4581 g, the fourth rock from a red dwarf some 20 light years from Earth in the constellation of Libra

GJ 1214 b, a sub-Neptune-sized planet orbiting a star in the constellation of Ophiucus 40 light years away

and HD 28185 b, a gas giant in a near circular orbit that is entirely within the habitable zone of a Sun-like star in the constellation of Eridanus. This planet’s moons, if it has any, may be good candidates for ‘other Earths’

Today, we can add another strange planet to the list: 55 Cancri f, one of five planets known to orbit an orange dwarf star some 40 light years away in the constellation of Cancer.

Kaspar von Braun at the California Institute of Technology in Pasadena and a few pals have measured its orbit accurately for the first time. These guys are able to confirm that 55 Cancri f is a genuine candidate to support liquid water.
They say that although this planet’s orbit is much more elliptical than Earth’s, it still spends most of its time (74 per cent) in the habitable zone.
Furthermore, 55 Cancri f is quite like Earth in some ways. Its year is about the same length as ours. And with moderate greenhouse warming, it could support liquid water all year round.
But unlike Earth, its mass is about the same as Neptune’s (although it doesn’t seem to have a large gaseous atmosphere).
And one other thing. it has two suns! This system consists of an orange dwarf star with a companion red dwarf that orbits at a distance of about 1000 AU. 55 Cancri f is part of a binary star system.
That’s weird! The sky on Cancri 55 f must be out of this world. For one half of the year, red and orange suns would light the daytime sky. Then, at night, the red dwarf would be visible for half the year and distant stars only visible for the other half.
That makes Cancri 55 f, if not the most promising exo-Earth, then at least the most exotic.
Ref: The 55 Cancri System: Fundamental Stellar Parameters, Habitable Zone Planet, and Super-Earth Diameter

Written by physicsgg

July 18, 2011 at 7:08 am


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New Planets Feature Young Star and Twin Neptunes

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Illustration of a system with twin Neptune-like planets

An international team, including Oxford University scientists, has discovered 10 new planets. Amongst them is one orbiting a star perhaps only a few tens of million years old, twin Neptune-sized planets, and a rare Saturn-like world.
The planets were detected using the CoRoT (Convection, Rotation and Transits) space telescope, operated by the French space agency CNES. It discovers planets outside our solar system — exoplanets — when they ‘transit’, that is pass in front of their stars.
The new finds were announced on 14 June at the Second CoRoT Symposium, held in Marseille…. Read the rest of this entry »

Written by physicsgg

July 14, 2011 at 6:25 pm


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Ethane: A Fingerprint For Life On Exoplanets

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Before discussing the conclusions of this paper released this week, I’ll start with a pub-quiz style question. How much of Earth’s atmosphere has not been made by living things?
The answer is: less than 1%, which is mostly argon. The overwhelming majority is biogenic; the nitrogen is a product of denitrifying bacteria, the oxygen from plants, and the inconspicuous CO2 is produced by everything, but especially animals.
So, would an alien astronomer look at a spectrum of Earth, see this cocktail of gases, and think, “Hmmm. Clearly this planet is harbouring life?” The chances are that they would. Earth looks decidedly odd from a distance. It would show a combination of a water-rich atmosphere, combined with a strong ozone absorption; this ozone peak is basically a proxy for oxygen, and its presence implies a continuous biological source of oxygen – especially in combination with reduced species such as methane, nitrous oxide, and methyl chloride. Without being replenished, oxygen rapidly removes itself by reacting with other gases and things on the Earth (you should see my brother’s car!).

From Hanel et al 1975, Exploration of the Solar System by infrared imaging. Apologies for the poor quality photo of a textbook.

The problem is, oxygen can also be produced by non-biological processes, and moreover, life doesn’t necessarily produce oxygen anyway. In fact, life got on pretty much fine for a long period of time without oxygen before it was released en masse, in what you could call the greatest mass pollution event in Earth’s history. So long lived was this period that we might expect most alien life supporting planets to be harbouring single celled ETs…….Read more:

Written by physicsgg

June 17, 2011 at 8:30 am


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Corot telescope in exoplanet haul

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Corot and other telescopes measure the light change when a planet "transits"

Ten new planets outside our Solar System have been spotted by the French-led Corot satellite, bringing the total number of known exoplanets to 561.

They include one planet orbiting an unusually young star, and two Neptune-sized planets orbiting the same star.
Corot, launched in 2006, spots planets by measuring the tiny dip in stellar light that occurs when planets pass between the stars and the Earth.
It has now added 23 planetary systems to the ever-growing roster.
Corot, operated by France’s space agency CNES, was launched in late 2006. It went into orbit shortly before Kepler, a similar mission by the American space agency Nasa.
Originally scheduled to run only until mid-2008, its remit has since been extended to 2013.
It has since established itself not only as a planet-hunter but also a precise instrument for astroseismology – the study of the composition of stars based on the light they emit.
In the latest list of 10 exoplanet finds, seven are so-called “hot Jupiters”, gas giant planets similar to our own Jupiter but far closer to their host star – completing their orbits in just days.
Two more orbit the star Corot-24, with diameters equal to and about 1.4 times that of Neptune, completing their orbits in five and 12 days, respectively.
One of the hot Jupiter planets orbits the star Corot-18, which is believed to be just 600 million years old. This is of particular interest to astrophysicists because there is much to be learned from the earliest stages of planet formation.
“If we want to understand the conditions in which planets form, we need to catch them within the first few hundred million years,” said Suzanne Aigrain, a University of Oxford astrophysicist who is part of the Corot team.
“In the case of Corot-18, different ways of determining the age give different results, but it’s possible that the star might be only a few tens of millions of years old. If this is confirmed, then we could learn a lot about the formation and early evolution of hot gas giant planets by comparing the size of Corot-18b to the predictions of theoretical models.”

  • 1. 4-colour CCD camera and electronics: Captures and analyses starlight
  • 2. Baffle: Works to shield the telescope from extraneous light
  • 3. Telescope: A 30cm mirror; it views the star fields
  • 4. Proteus platform: Contains communication equipment, temperature controls and direction controls
  • 5. Solar panel: Uses the Sun’s radiation to power the satellite

Written by physicsgg

June 14, 2011 at 9:04 pm


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