Astronomers Discover Potentially Earthlike Planet Orbiting Binary Star • Hacker News Board

Re: Astronomers Discover Potentially Earthlike Planet Orbiting Binary Star

#21

Post by splat » Mon, Jul 18, 2011, 3:08 PM UTC

retube wrote: post #6

johno215 wrote: post #5

Earlier quoted context omitted.

This has become a common pattern with exo-planet reporting. Often they are reported to be "earth like" or "habitable" when they only have potential for liquid water. Also, some of these planets that are reported may not actually exits. See http://en.wikipedia.org/wiki/Gliese_581_g .

Yeah well it's an unfortunate by-product of a) research institutions feeling the pressure to spin their output in a way which is consumer-friendly and b) the publishing industry turning that spin into an absurd attention-grabbing headline.

It's more a by-product of the fact that the Kepler mission has produced so many planet candidates (with an estimated ~50% false positive rate) that it would require about 30 years of telescope time on the world's largest telescopes to actually confirm that the stars have planets.

Re: Astronomers Discover Potentially Earthlike Planet Orbiting Binary Star

#22

Post by dmragone » Mon, Jul 18, 2011, 3:31 PM UTC

iwwr wrote: post #8

A red dwarf from 1000 au would only look like a moderately bright star, won't it? On the other hand, it would be close enough that if aliens inhabited, they could send a probe with present-day human level of technology. That is, the nearby star would serve as a stepping stone and an excuse to bridge the gap to interstellar space. Compare it to our Alpha Centauri, which lies just shy of 300K au, a relatively costly co…

What would the level of light produced by this red dwarf in comparison to, say, the light produced by a full moon on Earth?

Re: Astronomers Discover Potentially Earthlike Planet Orbiting Binary Star

#23

Post by danking00 » Mon, Jul 18, 2011, 4:08 PM UTC

splat wrote: post #21

retube wrote: post #6

Earlier quoted context omitted.

Yeah well it's an unfortunate by-product of a) research institutions feeling the pressure to spin their output in a way which is consumer-friendly and b) the publishing industry turning that spin into an absurd attention-grabbing headline.

It's more a by-product of the fact that the Kepler mission has produced so many planet candidates (with an estimated ~50% false positive rate) that it would require about 30 years of telescope time on the world's largest telescopes to actually confirm that the stars have planets.

Can you cite a source for your 50% false positive rate? I found a source[1] that argues for a ten percent false positive rate.

What do you mean to "confirm" that the stars have planets? I could imagine, directly imaging them is confirmation, but, as I understand it, that's nearly impossible for the average exoplanet we've found. What types of data are Kepler and COROT lacking which you desire for confirmation?

[1] http://arxiv.org/abs/1101.5630

Re: Astronomers Discover Potentially Earthlike Planet Orbiting Binary Star

#24

Post by danking00 » Mon, Jul 18, 2011, 4:12 PM UTC

Roboprog wrote: post #17

danking00 wrote: post #15

Earlier quoted context omitted.

It looks like the planet actually slides closer in to the star, thus the issue would be keeping the environment cool enough.

Closer to a smaller, cooler star.

Yes, but the habital zone scales with star size, so a radial position less than the habital zone would indeed be warmer than desirable for Earth-like life.

Re: Astronomers Discover Potentially Earthlike Planet Orbiting Binary Star

#25

Post by iwwr » Mon, Jul 18, 2011, 4:26 PM UTC

dmragone wrote: post #22

iwwr wrote: post #8

A red dwarf from 1000 au would only look like a moderately bright star, won't it? On the other hand, it would be close enough that if aliens inhabited, they could send a probe with present-day human level of technology. That is, the nearby star would serve as a stepping stone and an excuse to bridge the gap to interstellar space. Compare it to our Alpha Centauri, which lies just shy of 300K au, a relatively costly co…

What would the level of light produced by this red dwarf in comparison to, say, the light produced by a full moon on Earth?

Much lower. You can still read off the light of the full moon, barely.

http://en.wikipedia.org/wiki/Apparent_magnitude#Table_of_not...

For comparison's sake, if the Sun were 600au away, it would be as bright as the full moon. This red dwarf is much less luminous as it is, being at 1000au would make it bright, but unremarkable.

To put things more into prespective, this red dwarf at 1000au distance would be as bright as our Sun 50K au away (or 0.8 ly away).

Re: Astronomers Discover Potentially Earthlike Planet Orbiting Binary Star

#26

Post by rbanffy » Mon, Jul 18, 2011, 4:46 PM UTC

retube wrote: post #4

Sensationalist headline. Actually just a candidate for supporting liquid water (and then only for some of it's fairly elliptic orbit). And it's pretty damn big, so not likely to be a rock, more like a gas giant (If it _doesn't _ have a large gaseous atmosphere it would I think be the biggest rock planet ever discovered.) So "habitable exo-planet" is stretching things............... a lot.

> So "habitable exo-planet" is stretching things............... a lot.

Not to say anything about how hard would it be just to get there.

Re: Astronomers Discover Potentially Earthlike Planet Orbiting Binary Star

#27

Post by sdfjkl » Mon, Jul 18, 2011, 6:52 PM UTC

"The sky on Cancri 55 f must be out of this world."

Arrrgh.

Re: Astronomers Discover Potentially Earthlike Planet Orbiting Binary Star

#28

Post by lawlit » Mon, Jul 18, 2011, 7:05 PM UTC

JohnIdol wrote: post #12

lawlit wrote: post #7

The planet was discovered in April 2005, nothing news.

I thought discovery of 55 Cancri f was published in this paper on the 11th of July this year --> http://arxiv.org/abs/1107.1936

Well I guess you're wrong --> http://web.archive.org/web/20061216012023/http://www.aas.org...

It was discovered in April 2005. http://en.wikipedia.org/wiki/55_Cancri_f

Re: Astronomers Discover Potentially Earthlike Planet Orbiting Binary Star

#29

Post by jcasman » Mon, Jul 18, 2011, 8:25 PM UTC

Posted similar comment directly to the article. Quite pleased with myself for noticing a typo without having to check. It's probably "Gliese 581g" without the extra "4" that the author is referring to in the list of top candidates. It proves the point, though, that this is a hot area of astronomy. I'm no expert, but I was familiar enough with the first exasolar discoveries to notice the typo immediately.

Re: Astronomers Discover Potentially Earthlike Planet Orbiting Binary Star

#30

Post by civilian » Mon, Jul 18, 2011, 8:47 PM UTC

lawlit wrote: post #28

JohnIdol wrote: post #12

Earlier quoted context omitted.

I thought discovery of 55 Cancri f was published in this paper on the 11th of July this year --> http://arxiv.org/abs/1107.1936

Well I guess you're wrong --> http://web.archive.org/web/20061216012023/http://www.aas.org... It was discovered in April 2005. http://en.wikipedia.org/wiki/55_Cancri_f

Yes, but the 'news' is that it is within the habitable zone. (For certain definitions of habitable.)