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Earth-sized planet around nearby star is astronomy dream come true
http://www.nature.com/news/earth-sized-planet-around-nearby-star-is-astronomy-dream-come-true-1.20445
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Planet orbiting Proxima Centauri is likely to be the focus of future
interstellar voyages.
Corrected:
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Ricardo Ramirez
The newly discovered planet orbits Proxima Centauri every 11.2 days.
Proxima Centauri, the star closest to the Sun, has an Earth-sized planet
orbiting it at the right distance for liquid water to exist. The discovery,
reported today in Nature, fulfils a longstanding dream of science-fiction
writers — a potentially habitable world that is close enough for humans to send
their first interstellar spacecraft.
“The search for life starts now,” says Guillem Anglada-Escudé, an astronomer at
Queen Mary University of London and leader of the team that made the discovery.
Humanity’s first chance to explore this nearby world may come from the recently
announced Breakthrough Starshot initiative, which plans to build fleets of tiny
laser-propelled interstellar probes in the coming decades. Travelling at 20% of
the speed of light, they would take about 20 years to cover the 1.3 parsecs
from Earth to Proxima Centauri.
LISTEN
How a science-fiction story about our nearest neighbour became a reality
00:00
Proxima’s planet is at least 1.3 times the mass of Earth. The planet orbits its
red-dwarf star — much smaller and dimmer than the Sun — every 11.2 days. “If
you tried to pick the type of planet you’d most want around the type of star
you’d most want, it would be this,” says David Kipping, an astronomer at
Columbia University in New York City. “It’s thrilling.”
Earlier studies had hinted at the existence of a planet around Proxima.
Starting in 2000, a spectrograph at the European Southern Observatory (ESO) in
Chile looked for shifts in starlight caused by the gravitational tug of an
orbiting planet. The resulting measurements suggested that something was
happening to the star every 11.2 days. But astronomers could not rule out
whether the signal was caused by an orbiting planet or another type of
activity, such as stellar flares.
Star and planet align
In January 2016, Anglada-Escudé and his colleagues launched a campaign to nail
down the suspected Proxima planet. ESO granted their request to observe using a
second planet-hunting instrument, on a different telescope, for 20 minutes
almost every night between 19 January and 31 March. “As soon as we had 10
nights it was obvious,” Anglada-Escudé says.
The team dubbed the work the ‘pale red dot’ campaign, after the famous 'pale
blue dot' photograph taken of Earth by the Voyager 1 spacecraft in 1990.
Because Proxima is a red-dwarf star, the planet would appear reddish or
orangeish, perhaps bathed in light similar to the warm evening tints of Earth.
The exoplanet next door
NOTE This video contains an error. At 0:54 an animation representing the radial
velocity method for finding exoplanets is incorrect. Here is a link to a
correct representation https://www.eso.org/public/unitedkingdom/videos/eso1035g/
Although the planet orbits at a distance that would permit liquid water, other
factors might render it unlivable. It might be tidally locked — meaning that
the same hemisphere always faces the star, which scorches one side of the
planet while the other remains cool. The active star might occasionally zap the
planet with destructive X-ray flares. And it's unclear whether the planet has a
protective, life-friendly atmosphere.
Proxima itself belongs to the triple-star system Alpha Centauri. In 2012, a
Nature paper reported that an Earth-mass planet orbited another member of that
stellar trio, Alpha Centauri B. That result has now mostly been dismissed, ,
but exoplanet specialists say the Proxima claim is more likely to hold up.
“People call me Mr Sceptical, and I think this result is more robust,” says
Artie Hatzes, an astronomer at the Thuringian State Observatory in Tautenburg,
Germany.
False alarm
This time, the combination of new observations and older measurements dating
back to 2000 increases confidence in the finding, Anglada-Escudé’s team argues.
“It’s stayed there robustly in phase and amplitude over a very long time,” says
team member Michael Endl, an astronomer at the University of Texas at Austin.
“That’s a telltale sign of a planet.” The data even contain hints that a second
planet may exist, orbiting Proxima somewhere between every 100 and 400 days.
The researchers now hope to learn whether the Proxima planet's pass across the
face of its star can be seen from Earth. The chances are low, but such a
‘transit’ could reveal details of the planet, such as whether it has an
atmosphere. A team led by Kipping has been independently looking for transits
around Proxima, and is frantically crunching its data in search of any signal.
The discovery of the Proxima planet comes at a time of growing scientific
interest in small planets around dwarf stars, says Steinn Sigurdsson, an
astrophysicist at Pennsylvania State University in University Park. NASA’s
Kepler space telescope has shown that rocky planets are common around such
stars, which themselves are the most common type of star in the Galaxy. “This
is a total vindication of that strategy,” he says.
One day, the Proxima planet might be seen as the birth of a new stage in
planetary research. “It gives us the target and focus to build the next
generation of telescopes and one day maybe even get to visit,” says Kipping.
“It's exactly what we need to take exoplanetary science to the next level.”
Journal name:
Nature
Volume:
536,
Pages:
381–382
Date published:
(25 August 2016)
DOI:
doi:10.1038/nature.2016.20445
Corrected:
The video accompanying this story contains an error. At 0:54 an animation
representing the radial velocity method for finding exoplanets is incorrect.
Here is a link to a correct representation
https://www.eso.org/public/unitedkingdom/videos/eso1035g/
Anglada-Escudé, G. et al. Nature 536, 437–440 (2016).
Article
PubMed
Dumusque, X. et al. Nature 491, 207–211 (2012).
Article
PubMed
ChemPort
Hatzes, A. P. Astrophys. J. 770, 133 (2013).
Article
Rajpaul, V., Aigrain, S. & Roberts, S. Mon. Not. R. Astron. Soc. 456, L6–L10
(2016).
Article
>From nature.com
The truth about exoplanets
17 February 2016
Rebooted Kepler spacecraft hauls in the planets
07 January 2016
The exoplanet files
18 November 2015
Climate scientists join search for alien Earths
17 April 2015
The exoplanet next door
16 October 2012
>From elsewhere
Pale Red Dot
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Alexandra Witze
Alex covers Earth and planetary sciences, with a little dabbling in astronomy.
She studied geology at the Massachusetts Institute of Technology and science
communication at the University of California, Santa Cruz. Among other places
she has worked as a journalist for Science News and the Dallas Mor…
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