Planet Found Orbiting Alpha Centauri!

Drakkith

From here: http://blogs.discovermagazine.com/ba...-has-a-planet/

marcus

Good find! The impressive thing was that the wobble speed they were detecting, by Doppler, was only about 1/2 a meter per second. 20 inches per second.

A foot per second is about one billionth of the speed of light----one ten-millionth of a percent.

So they were detecting the regular lengthening and shortening of particular wavelengths in the star's light by on the order of a ten-millionth of a percent.

The ability to do that is a step forward---it means being able to detect significantly lower-mass planets including some farther out from star. Fine accomplishment!

Drakkith

Wow, that's one hell of a fine measurement! Now if only my little 8 inch scope was able to do that...

SHISHKABOB

too hot for liquid water?

>puts away his copy of SMAC :(

litup

So many close in planets have been found, is that the galactic norm? It kind of takes the wind out of our sails for the interstellar science fiction 'just found a nice Earth planet we can get to in 100 years with our new photon drive' set:)

litup

I will say, however, on the new planet at AC, if and/or when we ever get to do interstellar probes or human travel to the nearby stars, AC would seem to be a natural first try, since besides being the closest, you get a nice 3 for one deal, 3 stars within 1/10th of a light year from one another, 3 for the price of one, great deal for the astronaut set.

Drakkith

It is simply a result of planets that are close to their stars being MUCH easier to detect than planets further away. I fully expect to find lots of planets at all kinds of distances from their stars as time passes and our detections methods get more sensitive.

mfb

~4 orders of magnitude below doppler broadening of the spectral lines.
And just a factor of ~5 above an earth-like planet.
The next generation of telescopes will find them.
It is an amazing time to live in.

A significant fraction of all stars nearby has known planets - and that includes only planets which can be detected today.

Transits are not so distance-dependent. The other interesting exoplanet this week is 5000 light years away. It orbits a double-star, which is part of a system with 4 stars.

Drakkith

Sure they are. The closer to the star, the more transits, the easier it is to detect and confirm them. One of the reasons so many hot jupiters were found initially by the Kepler spacecraft was that their transits occurred very rapidly, whereas longer period planets weren't detected until later on and then had to wait much longer for a 2nd transit to verify them.

mfb

Oh sorry, I misread your post as "planets close to our star".
That distance matters, too, as the overall apparent brightness (and with it, the precision of spectroscopy and relative luminosity measurements) goes down.

You are right, the distance between planets and their corresponding stars is really important.

Kepler requires 3 transits for a confirmation - the second transit does not confirm that the signal is periodic.

cepheid

Don't get me wrong, I share the optimism that this result produces about our ability to make measurements fine enough to detect Earth-like planets -- eventually. But I wonder if that ability isn't being overstated somewhat. After all, presumably a large reason why this worked (given our current sensitivity and precision) is because we were looking at *the most nearby star* that we could possibly look at, right?

Also, when I mentioned this find to a colleague, their response was, "okay, so why is this exciting?" A valid question. Sure, it's an Earth-size planet orbiting the nearest star. But it's not like the conditions there are anything like Earth, nor is the probability of going to the nearest star (and it not being a one-way trip) in our lifetimes any better than the probability of going to any other star. Not only that, but even if conditions were like Earth, why would that be exciting? Maybe I can understand the public's fascination with that, but not astronomers. It presupposes that the "holy grail" of exoplanet science is to find *a* planet just like Earth that might be capable of supporting life similar to our own. I would dispute that that is of primary importance, *astronomically* speaking. (Besides, even if you hold finding evidence of extraterrestrial life to be of primary importance, which I don't, why the bias towards life similar to what's here? If there's anything life has taught us, it's that it is extremely resilient and adaptable. Who's to say that some other really alien form of life with a totally different biochemistry that isn't immediately recognizable as such doesn't exist? But this is off-topic). Shouldn't exoplanet people be trying to understand more about how the physical process of planet formation works, and about how prevalent (or exceptional) solar systems like our own are? About what kinds and diversities of systems and planets exist? Not to mention how common planets are at all in our Galaxy (and I acknowledge that Kepler is beginning to answer that question)? It really bothers me sometimes what the media gets all worked up about and what they portray as being meaningful and scientifically significant, as compared to what actually is.

Garth

One reason that this is so exciting is that an earth sized planet has been discovered in the star system 'next door'. They are therefore probably not rare.

Okay this one is too hot, but cooler 'Earths' (further away from their parent star) will be more difficult to find - give them time....

Garth

cepheid

If you think my main objection to to the buzz was that this one was too hot, you didn't read my post in its entirety.

Okay, maybe I'm just in a snarky mood today...

sshai45

I think you just answered why the media would get so excited. Because the general public (i.e. those who are not researchers in the field) and researchers in the field have two very different standards of what constitutes "exciting". The general media is made for the general public, not for researchers, when it comes to these topics. And why should it be anything else? I don't see anything wrong with them getting excited about it, since their target audience is not researchers.

Drakkith

Why is this exciting? Why is finding a new moon around Neptune exciting? Because it is! Lol.
Anyways, I thought it was cool and worth posting given that Alpha Centauri is the closest star system to our own and is a triple star system. If that isn't exciting, then I guess you aren't excited about exoplanets like I am.

Of course you are speaking to a guy who has done exoplanet transit light curves and participated in the Planethunters project at Zooniverse.org, so maybe I'm just biased!

cepheid

My complaint was not that the public should be interested in different things, but that the media misrepresent the science that is being done, what avenues of inquiry are being pursued, what questions are of interest, and the significance of a given finding in the broader context of the field.

Not only are extrasolar planets the branch of astronomy towards which I'm least inclined, but I think I've also just been oversaturated with exoplanet talks and media hype surrounding "discoveries" that just involve the results of applying the same observational technique over and over again. I don't want to see another light curve, or to hear about one particular object that somehow managed to serve as an excuse for a whole paper.

Drakkith

Well, that's disheartening to hear, but to each his own. As for the observational techniques, isn't that what practically all astronomical discoveries involve? Doing the same thing but more accurate, for longer, at different wavelengths, etc? And is the orbital characteristics of a planet in a multiple star system or the analysis of a spectrum of the emitted light from a hot planet not good enough for a paper? I thought that was how all science got done, by doing little things one at a time.