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Earth Mass Planet Orbits Alpha Centauri B

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#1    Waspie_Dwarf

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Posted 16 October 2012 - 11:54 PM

Planet Found in Nearest Star System to Earth
ESO’s HARPS instrument finds Earth-mass exoplanet orbiting Alpha Centauri B


www.eso.org said:

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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.

Alpha Centauri is one of the brightest stars in the southern skies and is the nearest stellar system to our Solar System — only 4.3 light-years away. It is actually a triple star — a system consisting of two stars similar to the Sun orbiting close to each other, designated Alpha Centauri A and B, and a more distant and faint red component known as Proxima Centauri [1]. Since the nineteenth century astronomers have speculated about planets orbiting these bodies, the closest possible abodes for life beyond the Solar System, but searches of increasing precision had revealed nothing. Until now.

Our observations extended over more than four years using the HARPS instrument and have revealed a tiny, but real, signal from a planet orbiting Alpha Centauri B every 3.2 days,” says Xavier Dumusque (Geneva Observatory, Switzerland and Centro de Astrofisica da Universidade do Porto, Portugal), lead author of the paper. “It’s an extraordinary discovery and it has pushed our technique to the limit!

The European team detected the planet by picking up the tiny wobbles in the motion of the star Alpha Centauri B created by the gravitational pull of the orbiting planet [2]. The effect is minute — it causes the star to move back and forth by no more than 51 centimetres per second (1.8 km/hour), about the speed of a baby crawling. This is the highest precision ever achieved using this method.

Alpha Centauri B is very similar to the Sun but slightly smaller and less bright. The newly discovered planet, with a mass of a little more than that of the Earth [3], is orbiting about six million kilometres away from the star, much closer than Mercury is to the Sun in the Solar System. The orbit of the other bright component of the double star, Alpha Centauri A, keeps it hundreds of times further away, but it would still be a very brilliant object in the planet’s skies.

The first exoplanet around a Sun-like star was found by the same team back in 1995 and since then there have been more than 800 confirmed discoveries, but most are much bigger than the Earth, and many are as big as Jupiter [4]. The challenge astronomers now face is to detect and characterise a planet of mass comparable to the Earth that is orbiting in the habitable zone [5] around another star. The first step has now been taken [6].

This is the first planet with a mass similar to Earth ever found around a star like the Sun. Its orbit is very close to its star and it must be much too hot for life as we know it,” adds Stéphane Udry (Geneva Observatory), a co-author of the paper and member of the team, “but it may well be just one planet in a system of several. Our other HARPS results, and new findings from Kepler, both show clearly that the majority of low-mass planets are found in such systems.

This result represents a major step towards the detection of a twin Earth in the immediate vicinity of the Sun. We live in exciting times!” concludes Xavier Dumusque.
ESO will hold an online press conference offering journalists the opportunity to discuss the result and its impact with the scientists. To participate please read our media advisory



Notes

[1] The components of a multiple star are named by adding uppercase letters to the name of the star. Alpha Centauri A is the brightest component, Alpha Centauri B is the slightly fainter second star and Alpha Centauri C is the much fainter Proxima Centauri. Proxima Centauri is slightly closer to Earth than A or B and hence is formally the closest star.

[2] HARPS measures the radial velocity of a star — its speed towards or away from the Earth — with extraordinary precision. A planet in orbit around a star causes the star to regularly move towards and away from a distant observer on Earth. Due to the Doppler effect, this radial velocity change induces a shift of the star’s spectrum towards longer wavelengths as it moves away (called a redshift) and a blueshift (towards shorter wavelengths) as it approaches. This tiny shift of the star’s spectrum can be measured with a high-precision spectrograph such as HARPS and used to infer the presence of a planet.

[3] Using the radial velocity method, astronomers can only estimate a minimum mass for a planet as the mass estimate also depends on the tilt of the orbital plane relative to the line of sight, which is unknown. But, from a statistical point of view, this minimum mass is often close to the real mass of the planet.

[4] NASA’s Kepler mission has found 2300 candidate planets using an alternative method — searching for the slight drop in the brightness of a star as a planet passes in front of it (transits) and blocks some of the light. The majority of planet candidates detected by this transit method are very distant from us. But, in contrast, the planets found by HARPS are around stars close to the Sun — with the new discovery being the closest yet. This makes them better targets for many kinds of additional follow-up observations such as characterising the planet’s atmosphere.

[5] The habitable zone is a narrow annular region around a star in which water may be present in liquid form if conditions are right.

[6] ESPRESSO, the Echelle SPectrograph for Rocky Exoplanet and Stable Spectroscopic Observations, is to be installed on the ESO Very Large Telescope. Currently undergoing final design, it is scheduled to start operating in late-2016 or early-2017. ESPRESSO will feature radial velocity precision of 0.35 km/hour or less. For comparison, Earth induces a 0.32 km/hour radial velocity on the Sun. This resolution should thus enable ESPRESSO to discover Earth-mass planets in the habitable zone. The ESPRESSO consortium is led by team members responsible for the current discovery..


More information

This research was presented in a paper “An Earth mass planet orbiting Alpha Centauri B”, to appear online in the journal Nature on 17 October 2012.

The team is composed of Xavier Dumusque (Observatoire de Genève, Switzerland; Centro de Astrofisica da Universidade do Porto, Portugal), Francesco Pepe (Observatoire de Genève), Christophe Lovis (Observatoire de Genève), Damien Ségransan (Observatoire de Genève), Johannes Sahlmann (Observatoire de Genève), Willy Benz (Universität Bern, Switzerland), François Bouchy (Observatoire de Genève; Institut d’Astrophysique de Paris, France), Michel Mayor (Observatoire de Genève), Didier Queloz (Observatoire de Genève), Nuno Santos (Centro de Astrofisica da Universidade do Porto) and Stéphane Udry (Observatoire de Genève).

The year 2012 marks the 50th anniversary of the founding of the European Southern Observatory (ESO). ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning the 39-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.


Links Contacts

Xavier Dumusque
Observatoire de l’Université de Genève
Switzerland
Tel: +41 22 379 22 64
Email: xavier.dumusque@unige.ch

Stéphane Udry
Observatoire de l’Université de Genève
Switzerland
Tel: +41 22 379 24 67
Email: stephane.udry@unige.ch

Willy Benz
Center for Space and Habitability
Bern, Switzerland
Email: willy.benz@space.unibe.ch

Francesco Pepe
Observatoire de l’Université de Genève
Switzerland
Tel: +41 223 792 396
Cell: +41 79 302 47 40
Email: francesco.pepe@unige.ch

Damien Ségransan
Observatoire de l’Université de Genève
Switzerland
Tel: +41 223 792 479
Email: damien.segransan@unige.ch

Nuno Santos
Centro de Astrofisica da Universidade do Porto
Porto, Portugal
Tel: +351 226 089 893
Email: Nuno.Santos@astro.up.pt

Richard Hook
ESO, La Silla, Paranal, E-ELT and Survey Telescopes Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org


Posted Image Source: ESO


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#2    Euphorbia

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Posted 17 October 2012 - 12:30 AM

View PostWaspie_Dwarf, on 16 October 2012 - 11:54 PM, said:

Planet Found in Nearest Star System to Earth
ESO's HARPS instrument finds Earth-mass exoplanet orbiting Alpha Centauri B


Cool story, but I thought that Proxima Centauri was the closest star:

The closest star to our Sun would be one of the three in the Alpha Centauri system. The system is only 4.27 light years from the Sun. Alpha Centauri A is the primary in the system. It is slightly larger than our Sun. It has a similar yellowish color with a stellar classification of spectral type G2 V. It also rotates every 22 days compared to 25 for the Sun. The secondary, Alpha Centauri B, is slightly smaller and has a spectral type of K1 V. It is orangish-yellow compared to the primary. It is 90% as massive as our Sun and about 14% smaller in radius. It rotates every 41 days. The third in the system is called Proxima Centauri. It would technically, be the closest single star to our Sun at 4.22 light years.

http://www.universet...-star-to-earth/

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#3    Imaginarynumber1

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Posted 17 October 2012 - 02:44 AM

Just read this story. Such an awesome discovery.

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#4    joc

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Posted 17 October 2012 - 04:16 AM

I have a question.  I'm a bit skeptical of this 'planet'.  My question is, why have we been able to find planets orbiting stars considerably farther away than Alpha Centauri but are just now discovering a planet so close to us?   How did this planet escape us for all of these years?

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#5    WhyDontYouBeliEveMe

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Posted 17 October 2012 - 10:20 AM

View Postjoc, on 17 October 2012 - 04:16 AM, said:

I have a question.  I'm a bit skeptical of this 'planet'.  My question is, why have we been able to find planets orbiting stars considerably farther away than Alpha Centauri but are just now discovering a planet so close to us?   How did this planet escape us for all of these years?
i dont understand that either.. yeah why dont they spend money to explore the oceans first . to know our planet a bit better . . why the universe? weird scientist !


#6    Taun

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Posted 17 October 2012 - 10:36 AM

View Postjoc, on 17 October 2012 - 04:16 AM, said:

I have a question.  I'm a bit skeptical of this 'planet'.  My question is, why have we been able to find planets orbiting stars considerably farther away than Alpha Centauri but are just now discovering a planet so close to us?   How did this planet escape us for all of these years?

The vast majority of exo-planets thus far discovered are roughly Jupiter sized... Earth-sized planets are extremely hard to find as they have much less effect on the 'wobble' of a star - and cause much less dimming of the star by transiting...  The Centauri system is much much closer and thus much easier to study in finer detail...


#7    joc

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Posted 17 October 2012 - 10:59 AM

View PostTaun, on 17 October 2012 - 10:36 AM, said:

The vast majority of exo-planets thus far discovered are roughly Jupiter sized... Earth-sized planets are extremely hard to find as they have much less effect on the 'wobble' of a star - and cause much less dimming of the star by transiting...  The Centauri system is much much closer and thus much easier to study in finer detail...
Thanks;  makes sense! :)

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#8    Timonthy

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Posted 17 October 2012 - 12:07 PM

View PostEuphorbia, on 17 October 2012 - 12:30 AM, said:

Cool story, but I thought that Proxima Centauri was the closest star:

The closest star to our Sun would be one of the three in the Alpha Centauri system. The system is only 4.27 light years from the Sun. Alpha Centauri A is the primary in the system. It is slightly larger than our Sun. It has a similar yellowish color with a stellar classification of spectral type G2 V. It also rotates every 22 days compared to 25 for the Sun. The secondary, Alpha Centauri B, is slightly smaller and has a spectral type of K1 V. It is orangish-yellow compared to the primary. It is 90% as massive as our Sun and about 14% smaller in radius. It rotates every 41 days. The third in the system is called Proxima Centauri. It would technically, be the closest single star to our Sun at 4.22 light years.

http://www.universet...-star-to-earth/
Cool story bro.

But the article is titled:
'Planet Found in Nearest Star System to Earth'

:D

Edited by Timonthy, 17 October 2012 - 12:07 PM.

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#9    Sundew

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Posted 17 October 2012 - 12:58 PM

Perhaps the locals call it Centauri Prime?
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#10    Euphorbia

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Posted 17 October 2012 - 01:17 PM

View PostTimonthy, on 17 October 2012 - 12:07 PM, said:

Cool story bro.

But the article is titled:
'Planet Found in Nearest Star System to Earth'

:D

I fully understand that, but the article also says "a more distant and faint red component known as Proxima Centauri".........which is actually closer to us than the other two stars are. I don't know if this was a typo on their part, or if there's some disagreement over which is closer.

Other than that, yes, it was a great bit of news! I love these kinds of stories!

If I see something that I believe is a mistake, I'm going to point it out.....

Edited by Euphorbia, 17 October 2012 - 01:19 PM.

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#11    Vidgange

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Posted 17 October 2012 - 01:42 PM

Damn, that is some cool news!!! Sadly it appears to be too close to Centauri B to be habitable...

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#12    shaddow134

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Posted 17 October 2012 - 04:50 PM

Where there is one,there maybe more,good news when you consider the system is so close in astronomical terms..


#13    Grey14

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Posted 17 October 2012 - 05:14 PM

View PostEuphorbia, on 17 October 2012 - 01:17 PM, said:

I fully understand that, but the article also says "a more distant and faint red component known as Proxima Centauri".........which is actually closer to us than the other two stars are. I don't know if this was a typo on their part, or if there's some disagreement over which is closer.

Other than that, yes, it was a great bit of news! I love these kinds of stories!

If I see something that I believe is a mistake, I'm going to point it out.....

They were refering to it being more distant from Alpha Centauri A and B not from our solar system.

Edited by Grey14, 17 October 2012 - 05:15 PM.

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#14    Euphorbia

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Posted 17 October 2012 - 06:00 PM

View PostGrey14, on 17 October 2012 - 05:14 PM, said:

They were refering to it being more distant from Alpha Centauri A and B not from our solar system.

OK, got it....thanks! Although they could have worded it differently....

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#15    Waspie_Dwarf

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Posted 17 October 2012 - 07:08 PM

View PostEuphorbia, on 17 October 2012 - 06:00 PM, said:

Although they could have worded it differently....
Why? It is perfectly clear if you read it in context. What they actually said was:

Quote

a system consisting of two stars similar to the Sun orbiting close to each other, designated Alpha Centauri A and B, and a more distant and faint red component known as Proxima Centauri.


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