Thursday, 28 April 2016

Search for signs of life on distant planets advances

• Scientists spot Earth-like world in nearby star system, narrow down location for Planet Nine
The hunt for extraterrestrial life has long focused on planets at a just-right distance from alien stars, where liquid water can exist on a planet’s surface. PHOTO CREDIT: Nicolle Rager Fuller
The hunt for extraterrestrial life has long focused on planets at a just-right distance from alien stars, where liquid water can exist on a planet’s surface. PHOTO: Nicolle Rager Fuller
Astronomers believe they have found an Earth-like planet orbiting a star 16 light years away.The mysterious world was spotted around the star, GJ 832, which is already known to harbour two other exoplanets.
Scientists say the third planet may lie in the star’s ‘Goldilocks zone’ with a mass of one to 15 times that of Earth, suggesting it could be habitable.
GJ 832 is a red dwarf star with a mass of around half that of our sun. It has two exoplanets called Gliese 832b and Gliese 832c.The larger of the two, Gliese 832b, has the widest orbit and is located 3.53 AU from its host star. It has around 60 percent the mass of Jupiter.Gliese 832c, meanwhile, is a ‘super-Earth’ and around five times more massive than our planet. Its orbit is close, coming within 0.16 AU of its star.
As a comparison, in Earth’s solar system, the innermost planet Mercury comes no closer than 0.3 AU to the sun.At the time of its discovery in 2014, researchers said Gliese 832c might be the most similar planet to our own ever found – and may even have Earth-like temperatures, albeit with large seasonal shifts.
They said the exoplanet is in the star Gliese 832’s ‘habitable zone,’ the just-right range of distances that could allow liquid water to exist on a world’s surface.
But researchers now believe the planet is more likely to be a hostile ‘Venus 2.0’ with a thick atmosphere, according to a report in Discovery.
Instead, they say a third planet may be sandwiched between the two – and it may be far more Earth-like than Gliese 832c.By studying the electromagnetic spectrum of GJ 832, researchers have been attempting to find out what orbits the red dwarf.
Meanwhile, researchers may be narrowing in on the location of the mysterious Planet Nine.Using data from the Cassini spacecraft, a pair of astronomers has worked out the possibility of several orbits for the mystery world.Their results suggest the ninth planet is lurking near the constellation of Cetus, somewhere in relatively small area of the sky.
Researchers inferred Planet Nine’s presence from the peculiar clustering of six previously known objects that orbit beyond Neptune. They say there’s only a 0.007 per cent chance, or about one in 15,000, that the clustering could be a coincidence.
Instead, they say, a planet with the mass of 10 Earths has shepherded the six objects into their strange elliptical orbits, tilted out of the plane of the solar system.
The unknown world, dubbed ‘Planet Nine’ or ‘Planet X,’ is thought to be 10 times more massive than Earth and the furthest planet from the sun.
But, since its existence was first proposed, United States National Aeronautic Space Agency (NASA) has warned that claims of a new planet lurking in our solar system are premature.
In a paper published this month, Matthew Holman and Matthew Payne describe the new method that could accelerate the search for Planet Nine.
The researchers are analysing data from the Cassini spacecraft in a way that considers multiple orbits as opposed to just one, Payne explained to New Scientist.
Through this analysis, the team has been able to tighten predictions for the position, distance, and mass for a possible distant planet at the edge of our solar system.
The research pins the location of Planet Nine to two ‘stripes,’ which were then overlapped with the favoured orbit of Konstantin Batygin and Mike Brown, two Caltech planetary scientists who proposed the existence of the ninth planet earlier this year.Astronomers have so far focused their search for alien life on planets that are similar to our own.
But extra-terrestrial beings could be residing on worlds that look like giant eyeballs instead, according to one researcher.These planets have one side permanently gazing at their host red dwarf star because they are ‘tidally locked’ in the same way that moon is to Earth.
Sean Raymond in Nautilus explains that if you were standing on the surface of a planet like this, the sun would remain fixed in one spot on the sky.As a result, these ‘eyeball’ planets have a permanent day side and permanent night side.
This means that the water is trapped unable to reach the temperate side of the planet, creating huge glaciers on the dark side.These planets could either be ‘hot eyeball’ worlds or ‘icy eyeball’ planets. A hot eyeball planet is located close to its star, on an orbit that makes it hotter overall than Earth.
The day side would be roasting with any water boiling into vapour, while the night side would be freezing.But at the terminator – the boundary between night and day – conditions could be just right for life to thrive.This technique is known as the ‘radial velocity method’ (RV) and works by looking at the pattern of changes in the frequency of starlight.
Suman Satyal of the University of Texas at Arlington recently took a closer look at the starlight spectrum of GJ 832.“We obtained several radial velocity curves for varying masses and distances for the middle planet,” Satyal writes in a paper published by the arXiv pre-print service.
Their as yet unnamed exoplanet could exist with an orbit between 0.25 to 2.0 AU from the star with a mass of one to 15 Earth masses.The planet would likely be super-Earth, possibly a world occupying the star’s habitable zone where alien life could exist.
“We have provided an estimated number of RV observations for the additional planet for further observational verification,” the researchers said.
“We put Planet Nine at a while different slew of locations – all different possibilities on the sky, different distances, different masses – and tried to find out whether that constrains things even more,” Payne told New Scientist.
Based on their analysis, the researchers suggest the ninth planet may be toward the constellation of Cetus, in a small area of the sky that makes up just 20 degrees in radius.And, researchers with the Dark Energy Survey are coincidentally investigating this zone as well, New Scientist points out.

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