Cidersomerset
17th October 2012, 21:53
Exoplanet around Alpha Centauri is nearest-everBy Jason 17 October 2012
Science and technology reporter, BBC News
http://news.bbcimg.co.uk/media/images/63512000/jpg/_63512516_eso1241e.jpg
Our nearest stellar neighbours have been the subject of study since ancient times
Astronomers have found the nearest planet outside our Solar System, circling one of the stars of Alpha Centauri just four light-years away.
The planet has at minimum the same mass as Earth, but circles its star far closer than Mercury orbits our Sun.
It is therefore outside the "habitable zone" denoting the possibility of life, as the researchers report in Nature.
However, studies on exoplanets increasingly show that a star with one planet is likely to have several.
At the very least, the work answers the question first posed in ancient times about planets around our nearest stellar neighbours.
The closest star to the Sun is Proxima Centauri, which is believed to be part of a three-star system that includes the brighter stars Alpha Centauri A and B.
The planet was found near Alpha Centauri B by the Harps instrument at the European Southern Observatory's La Silla facility in Chile.
That puts it far closer to Earth than any of the more than 840 confirmed exoplanets
Like a dance between one enormous and one tiny partner, as an exoplanet orbits its much larger host star, its gravity causes the star to move in a small orbit.
Harps and instruments like it measure the subtle change in colour - the redshift or blueshift - of the host star's light as its orbit moves it slightly closer to and further away from Earth.
'Landmark discovery'
What has delayed this finding is that because Alpha Centauri is itself a complicated system of stars orbiting one another, the effect of a comparatively tiny planet is difficult to detect.
But careful measurements over four years showed that the planet whips around Alpha Centauri B in just 3.6 days, and is estimated to have a surface temperature of about 1,200C.
Many planets in similar orbits are "tidally locked", meaning the same side is always facing the host star, but further observations will be required to examine the planet further, finding out for example if it has an atmosphere.
Since the very first planets outside our solar system were discovered in the early 1990s, the hope has been to find an "Earth twin" - a planet like ours, orbiting a star like ours, at a distance like ours.
The new planet around Alpha Centauri B matches Earth only in terms of its mass - making it among the smallest exoplanets we know of.
But in a catalogue with hundreds of confirmed planets and thousands of planet candidates added since 1992, it is otherwise unremarkable - except for its proximity.
"Alpha Centauri B is of course a very special case - it's our next door neighbour," said Stephane Udry of the Observatory in Geneva and senior author of the paper.
"So even if the discovery just stands perfectly normally in the discoveries we have had up to now, it's a landmark discovery, because it's very low-mass and it's our closest neighbour."
Marek Kukula, Public Astronomer at the Royal Observatory Greenwich, said that beyond that, the planet's very existence makes a tantalising suggestion.
"Everything that we've discovered in the last few years tells us that where we find one small, rocky planet there are likely to be others," he told BBC News.
"I think the odds are very good that there may well be other planets in this system a little further out, perhaps a little more comfortable temperatures - so I think the hunt is on."
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r-TJb9lPCD4
Published on 17 Oct 2012 by TBar1984
ESO's HARPS instrument finds Earth-mass exoplanet orbiting Alpha Centauri B. "European astronomers have discovered a planet with about the mass of the Earth orbiting a star in the Alpha Centauri system — the nearest to Earth. It is also the lightest exoplanet ever discovered around a star like the Sun. The planet was detected using the HARPS instrument on the 3.6-metre telescope at ESO's La Silla Observatory in Chile. The results will appear online in the journal Nature on 17 October 2012."
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The Exoplanet Next-Door: Astronomers Discover World in Nearest Star System
The small planet orbiting Alpha Centauri B, just four light-years away, is too hot for life but may have habitable neighbors
By John Matson
http://www.scientificamerican.com/article.cfm?id=alpha-centauri-planet
=======================================================
http://www.mnn.com/sites/default/files/AlphaCentauriExoplanet_m_10.jpg
An artist's illustration shows a planet just slightly more massive than Earth orbiting very close to Alpha Centauri B. (Image: ESA)
An alien planet discovered around a star in the Alpha Centauri system, the nearest to our own sun, has astronomers buzzing, and not just because it's the closest exoplanet to Earth ever seen.
The newfound extrasolar planet Alpha Centauri Bb, it turns out, is not only the nearest alien world to Earth, it's also extremely Earthlike in size and mass. The planet is much too hot and too close to its parent star to support life, but its existence suggests the tantalizing possibility that there may be more planets waiting to be found in our neighboring star system.
Here's a look at the numbers behind the newfound alien planet Alpha Centauri Bb:
25 trillion: The number of miles Alpha Centauri Bb is from Earth. That's about 40 trillion kilometers. Sound far? It's still the closest star system to our sun.
3.6 million: The distance, in miles, at which the planet orbits its parent star Alpha Centauri B. This is much closer to the star than Mercury is to our sun. Earth is 93 million miles (150 million km) from the sun.
40,000: The approximate number of years it would take an unmanned spacecraft like NASA's Voyager 1 probe now leaving our solar system to reach Alpha Centauri Bb. You'd need a lot of snacks for that trip.
2,240: The likely surface temperature in Fahrenheit (it's 1,227 degrees Celsius) for planet Alpha Centauri Bb. The planet is so hot, its surface is likely melted into a molten slag, making it a truly hellish "lava world." Bring your sunscreen.
800: The lower limit for confirmed alien planets scientists have discovered since the mid-1990s. There are thousands more awaiting confirmation.
4.3: The number of light-years Alpha Centauri Bb is from Earth. The star system is visible only from the Southern Hemisphere of our planet. (Sorry, northern stargazers!)
3.2: The number of Earth days it takes planet Alpha Centauri Bb to complete one "year" around its parent star. BONUS! 3 is also the number of stars in the Alpha Centauri system. There's Alpha Centauri A and B (the new planet's sun), and Proxima Centauri, which is actually slightly closer to Earth than the other two.
2: The number of sunlike stars in the Alpha Centauri system. The stars Alpha Centauri A and B are both similar to our sun and. Proxima Centauri is much fainter than Earth.
1.13: The mass of alien planet Alpha Centauri Bb as compared to that of Earth. It is the first Earth-mass planet around a sunlike star ever found, scientists say.
http://www.mnn.com/earth-matters/space/stories/alpha-centauri-exoplanet-by-the-numbers
Science and technology reporter, BBC News
http://news.bbcimg.co.uk/media/images/63512000/jpg/_63512516_eso1241e.jpg
Our nearest stellar neighbours have been the subject of study since ancient times
Astronomers have found the nearest planet outside our Solar System, circling one of the stars of Alpha Centauri just four light-years away.
The planet has at minimum the same mass as Earth, but circles its star far closer than Mercury orbits our Sun.
It is therefore outside the "habitable zone" denoting the possibility of life, as the researchers report in Nature.
However, studies on exoplanets increasingly show that a star with one planet is likely to have several.
At the very least, the work answers the question first posed in ancient times about planets around our nearest stellar neighbours.
The closest star to the Sun is Proxima Centauri, which is believed to be part of a three-star system that includes the brighter stars Alpha Centauri A and B.
The planet was found near Alpha Centauri B by the Harps instrument at the European Southern Observatory's La Silla facility in Chile.
That puts it far closer to Earth than any of the more than 840 confirmed exoplanets
Like a dance between one enormous and one tiny partner, as an exoplanet orbits its much larger host star, its gravity causes the star to move in a small orbit.
Harps and instruments like it measure the subtle change in colour - the redshift or blueshift - of the host star's light as its orbit moves it slightly closer to and further away from Earth.
'Landmark discovery'
What has delayed this finding is that because Alpha Centauri is itself a complicated system of stars orbiting one another, the effect of a comparatively tiny planet is difficult to detect.
But careful measurements over four years showed that the planet whips around Alpha Centauri B in just 3.6 days, and is estimated to have a surface temperature of about 1,200C.
Many planets in similar orbits are "tidally locked", meaning the same side is always facing the host star, but further observations will be required to examine the planet further, finding out for example if it has an atmosphere.
Since the very first planets outside our solar system were discovered in the early 1990s, the hope has been to find an "Earth twin" - a planet like ours, orbiting a star like ours, at a distance like ours.
The new planet around Alpha Centauri B matches Earth only in terms of its mass - making it among the smallest exoplanets we know of.
But in a catalogue with hundreds of confirmed planets and thousands of planet candidates added since 1992, it is otherwise unremarkable - except for its proximity.
"Alpha Centauri B is of course a very special case - it's our next door neighbour," said Stephane Udry of the Observatory in Geneva and senior author of the paper.
"So even if the discovery just stands perfectly normally in the discoveries we have had up to now, it's a landmark discovery, because it's very low-mass and it's our closest neighbour."
Marek Kukula, Public Astronomer at the Royal Observatory Greenwich, said that beyond that, the planet's very existence makes a tantalising suggestion.
"Everything that we've discovered in the last few years tells us that where we find one small, rocky planet there are likely to be others," he told BBC News.
"I think the odds are very good that there may well be other planets in this system a little further out, perhaps a little more comfortable temperatures - so I think the hunt is on."
-------------------------------------------------------------------------------------------------
r-TJb9lPCD4
Published on 17 Oct 2012 by TBar1984
ESO's HARPS instrument finds Earth-mass exoplanet orbiting Alpha Centauri B. "European astronomers have discovered a planet with about the mass of the Earth orbiting a star in the Alpha Centauri system — the nearest to Earth. It is also the lightest exoplanet ever discovered around a star like the Sun. The planet was detected using the HARPS instrument on the 3.6-metre telescope at ESO's La Silla Observatory in Chile. The results will appear online in the journal Nature on 17 October 2012."
------------------------------------------------------------------------------------------------
The Exoplanet Next-Door: Astronomers Discover World in Nearest Star System
The small planet orbiting Alpha Centauri B, just four light-years away, is too hot for life but may have habitable neighbors
By John Matson
http://www.scientificamerican.com/article.cfm?id=alpha-centauri-planet
=======================================================
http://www.mnn.com/sites/default/files/AlphaCentauriExoplanet_m_10.jpg
An artist's illustration shows a planet just slightly more massive than Earth orbiting very close to Alpha Centauri B. (Image: ESA)
An alien planet discovered around a star in the Alpha Centauri system, the nearest to our own sun, has astronomers buzzing, and not just because it's the closest exoplanet to Earth ever seen.
The newfound extrasolar planet Alpha Centauri Bb, it turns out, is not only the nearest alien world to Earth, it's also extremely Earthlike in size and mass. The planet is much too hot and too close to its parent star to support life, but its existence suggests the tantalizing possibility that there may be more planets waiting to be found in our neighboring star system.
Here's a look at the numbers behind the newfound alien planet Alpha Centauri Bb:
25 trillion: The number of miles Alpha Centauri Bb is from Earth. That's about 40 trillion kilometers. Sound far? It's still the closest star system to our sun.
3.6 million: The distance, in miles, at which the planet orbits its parent star Alpha Centauri B. This is much closer to the star than Mercury is to our sun. Earth is 93 million miles (150 million km) from the sun.
40,000: The approximate number of years it would take an unmanned spacecraft like NASA's Voyager 1 probe now leaving our solar system to reach Alpha Centauri Bb. You'd need a lot of snacks for that trip.
2,240: The likely surface temperature in Fahrenheit (it's 1,227 degrees Celsius) for planet Alpha Centauri Bb. The planet is so hot, its surface is likely melted into a molten slag, making it a truly hellish "lava world." Bring your sunscreen.
800: The lower limit for confirmed alien planets scientists have discovered since the mid-1990s. There are thousands more awaiting confirmation.
4.3: The number of light-years Alpha Centauri Bb is from Earth. The star system is visible only from the Southern Hemisphere of our planet. (Sorry, northern stargazers!)
3.2: The number of Earth days it takes planet Alpha Centauri Bb to complete one "year" around its parent star. BONUS! 3 is also the number of stars in the Alpha Centauri system. There's Alpha Centauri A and B (the new planet's sun), and Proxima Centauri, which is actually slightly closer to Earth than the other two.
2: The number of sunlike stars in the Alpha Centauri system. The stars Alpha Centauri A and B are both similar to our sun and. Proxima Centauri is much fainter than Earth.
1.13: The mass of alien planet Alpha Centauri Bb as compared to that of Earth. It is the first Earth-mass planet around a sunlike star ever found, scientists say.
http://www.mnn.com/earth-matters/space/stories/alpha-centauri-exoplanet-by-the-numbers