Planet found in Earth's nearest neighbour star system

N

nutball

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An exoplanet has been discovered orbiting Alpha Centauri B, which is a member of the closest star system to Earth, just 4.3 light-years away. The planet mass is (probably) of order one-to-a-few Earth masses, so it is likely a rocky planet.

http://www.eso.org/public/news/eso1241/

The orbital period is so short that it'll be nothing more than a scorched wasteland, however it's discovery holds out the possibility that there are other planets in the system at longer periods, possibly in the habitable zone.
 
UniversalTruth said:
:LOL: Only 4.3 light-years away and they did manage somehow to discover it just now? WTH?
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4.3 light years is 40,681,440,000,000 km

An earth sized planet would be just 0.06 milliarcsecond across. For comparison Hubble's angular resolution is 0.05 arcsecond.

Cheers
 
UniversalTruth said:
But that doesn't explain anything. I really hope they don't discover planets by seeing them. :LOL:
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From another site...
The other reason this is important is that the signal from the planet is incredibly weak. It was found through its gravity. As it orbits Alpha Cen B, the planet tugs on the star, like two children holding hands and swinging each other around. This sets up a very small but detectable Doppler shift in the starlight. The more massive the planet is, the harder it tugs on the star, and the bigger the signal (making it easier to detect). Also, the closer in a planet is, the larger the signal is… and you get the added benefit of a short orbital period, so you don't have to observe as long to see the cycle of the Doppler shift.

In this case, the planet is low mass but very close in. The Doppler shift in the starlight amounts to a mere half meter per second – slower than walking speed! When I read that I was stunned; that low of a signal is incredibly hard to detect.
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Half meter per second? That means they're detecting frequency shifts of 1 part in a billion!

How the hell do you measure frequency that accurately? On top of that, isn't Doppler broadening on the order of 10^-5? Meaning they are locating the center of a spectral line to an accuracy of 1/10,000th of its width?
 
Mintmaster said:
How the hell do you measure frequency that accurately?
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It's challenging, but if you cross-correlate the spectra with a reference spectrum you can make pretty precise measurements of the offsets (ie. the trick is to use a whole bunch of spectral lines, not just one).
 
For comparison Hubble's angular resolution is 0.05 arcsecond.
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I posted this before but for ~1.5 billion they can build a device with 1500x the light gathering of the hubble.
But we cant afford it!
zuckenberg got 1+ billion the other day.
 
zed said:
I posted this before but for ~1.5 billion they can build a device with 1500x the light gathering of the hubble.
But we cant afford it
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Yup, they better spend this money to destroy lives of whole nations, like Lybia, Iraq, Afghanistan, Vietnam, Syria, perhaps Iran... and many more :rolleyes:
 
UniversalTruth said:
Yup, they better spend this money to destroy lives of whole nations, like Lybia, Iraq, Afghanistan, Vietnam, Syria, perhaps Iran... and many more :rolleyes:
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This type of post is not warranted on this forum. Go to the RPSC forum if you wish to discuss your gripes about the Middle East. Try not to make a post like this again outside of RPSC.
 
Maybe they could mechanically mask out the star, like is done in solar observatories...?
 
Grall said:
Maybe they could mechanically mask out the star, like is done in solar observatories...?
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Often they look at stars, and if they notice that their brightness goes down and back up periodically, they figure some planet is getting in front of it.

That doesn't work very well for planets with long orbital periods, though. If you see a temporary decline in brightness and then nothing for another 150 years, it's kind of hard to conclude anything. And obviously, it only works if the Earth, the star and the exoplanet are roughly aligned.

And if the planet is small, then the decline in the brightness of the star is not very significant, perhaps not enough to be detected. That's why most of the exoplanets we know are "hot Jupiters", i.e. very large planets that orbit close to their star, with short orbital periods: they produce frequent, easy to confirm, large declines in brightness.
 
Alexko said:
That doesn't work very well for planets with long orbital periods, though. If you see a temporary decline in brightness and then nothing for another 150 years, it's kind of hard to conclude anything. And obviously, it only works if the Earth, the star and the exoplanet are roughly aligned.
Click to expand...

The chance of the planet passing in front of the start from our view point also falls significantly.

Cheers
 
The exciting thing about this is:
1. Our neighbour star system has rocky planets
2. There's a decent chance it has a rocky planet in the goldylocks zone
3. Current propulsion tech can get us there in 40,000 years
4. There are other proposed propulsion technologies which could get us there much, much faster but which lack funding to investigate/develop
5. Even the possibility of another habitable planet within human reach will greatly increase governments willingness to invest in the tech to get us there
6. Within our life times we see interstellar drive technology become a reality (even though we may not be around when our first probes reach another star system).
7. I want to be around for that.
 
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