16Nov2017

Scientists Discover A New Planet In The Neighbourhood

Ross

Vast and impenetrable though the universe may be, now we know it harbors at least one friendly neighbour.

One of our closest celestial neighbours is a warm, rocky world, scientists say. Scientists report the discovery of an Earth-size exoplanet orbiting the star Ross 128, a dim red dwarf just 11 light years away.

The newfound world, dubbed Ross 128b, is the closest temperate planet known to orbit a “quiet star” – one that isn’t prone to devastating and potentially life-obliterating bursts of radiation. And it appears to meet some of the basic requirements for habitability. The planet is slightly more massive than Earth, so it is probably a rocky world with a solid surface.

The host star is much cooler and fainter than our sun, but Ross 128b orbits it closely and quickly – a year lasts just 9.9 days. The planet receives about 38 per cent more radiation than Earth does – enough to give it an equilibrium temperature between -60 degrees and 20 degrees Celcius, assuming it has an Earthlike atmosphere (and that’s a huge assumption).

Though the study authors call Ross 128b a “temperate planet”, it’s not clear whether it falls within the habitable zone – the Goldilocks region where a planet is just warm enough for liquid water to exist on its surface.

Additionally, no current telescopes are capable of analysing the wavelengths of light coming from the planet, which might provide clues about the existence of an atmosphere and the potential for life. But, when the powerful 39-metre Extremely Large Telescope comes online in 2024, this world will be one of its first targets.

Ross 128b is not Earth’s nearest extra-solar neighbour. The exoplanet Proxima b, which orbits the star next door to our sun, is even closer than Ross 128b – just 4.2 light years away. But its host star, a red dwarf called Proxima Centauri, has been compared to a hormonal teenager. It produces violent flares of radiation that can strip away an atmosphere and sterilise a planet. You would not be a happy camper if you lived in the vicinity.

Ross 128 is more like a 30-something with a good job, a membership in a yoga studio and an extensive collection of James Taylor albums. You could probably trust it not to fry its own planet.

Indeed, Ross 128 is so agreeable that it’s actually heading toward us. According to Nicola Astudillo-Defru, an astronomer at the University of Geneva and co-author of the study, the star’s orbit through the galaxy has put it on a path toward Earth. In 71,000 years, it will become our closest neighbour, and Ross 128 will be the closest temperate planet.

Ross 128b was detected via the High Accuracy Radial Velocity Planet Searcher (HARPS), a planet-seeking program based at La Silla Observatory in Chile. As most exoplanets are too distant and too dim to be seen directly, HARPS looks for the telltale signature of a small world orbiting a star.

 

An artist's impression of the temperate planet Ross 128 b, which lies only 11 light-years from Earth.

An artist’s impression of the temperate planet Ross 128 b, which lies only 11 light-years from Earth. Photo: ESO/M. Kornmesser

Remember, a planet doesn’t really orbit its sun. Rather, both the planet and the sun orbit their common centre of mass – the point at which the gravitational forces they exert on each other are at equilibrium. Since stars are so much heftier than planets, that centre of mass is a whole lot closer to the star than to the planet, but it is not exactly in the star’s middle. This produces a characteristic “wobble”.

All this wobbling affects the radiation these stars emit: the light changes frequency, much the way a sound changes pitch when its source is moving – a phenomenon known as the Doppler effect.

Using this technique, the scientists at La Silla sorted through night after night of observations of the star Ross 128, looking for evidence of a Doppler effect. After capturing the star at more than 150 points in time, they determined that they had enough evidence to confirm the presence of a planet.

Noting that this is just the latest exoplanet discovery of thousands, Astudillo-Defru acknowledged that this one “may feel like one more among others”. But no other exoplanet known to science is as close and as seemingly hospitable as Ross 128b. “This one is special,” Astudillo-Defru added.

To date, NASA’s Exoplanet Archive includes 3,550 confirmed alien worlds: tremendous “Hot Jupiters” that orbit close to their suns; hellish planets whose surfaces are as hot as a star’s; bodies so compacted that their carbon is crushed into a diamond; “rogue” globes of gas that roam through the galaxy not bound to any star. There are a few dozen “Earth twins” – worlds that, from a distance, look not unlike our own.

But at times, that catalogue can feel like a travel guide to lands we’ll never see. Scientists seldom observe exoplanets directly – instead, they intuit the bodies’ existence based on tiny fluctuations in the light coming from distant stars. And given the vast distances involved in interstellar travel, no Earthling has a hope of visiting most of these places.

That’s true even of Ross 128b. Eleven light years might be a skip and a jump in cosmic terms, but it is still far greater than any expanse any human has traversed. For comparison, the moon – still the most distant destination visited by people – is a mere 1.3 light seconds away.

Still, it’s hard to argue with Astudillo-Defru. Vast and impenetrable though the universe may be, now we know it harbors at least one friendly neighbour. There’s something special about that. Source: SMH

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