

Astronomers Discover Potentially Earthlike Planet Orbiting Binary Star - JohnIdol
http://www.technologyreview.com/blog/arxiv/27005/

======
retube
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.

~~~
johno215
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>.

~~~
retube
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.

~~~
splat
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.

~~~
danking00
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>

~~~
splat
The false positive rate seems to have been revised to 40% since I last
checked, but my reference is here (though they cite the Morton & Johnson
paper, too):

<http://adsabs.harvard.edu/abs/2011ApJ...736...19B>

The 10% false positive rate is for rank 2 targets, but the majority of targets
are rank 4, which have a 40% false positive rate. (See section 2.2.2)

To confirm that the stars have planets, one would do spectroscopic follow up.
You would see the slight wobbling of the host star due to the gravitational
influence of the planet, and this would manifest itself in a slight Doppler
shifting of the spectral lines of the host star. The problem is that most of
the stars that Kepler is observing are so faint that ground-based
spectroscopic follow-up is impossible except on the largest telescopes, and
even then you can only do it for a handful of the thousands of candidates that
Kepler is discovering.

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iwwr
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 cosmic barrier to entry.

But for our neighbourhood, there is still the possibility of a brown dwarf or
Jupiter-sized world lurking in the depths of our Oort cloud. Alternative
destinations are 500-750au which would be good spots to place a telescope
(exploiting the Sun as a gravitational lens) <http://www.centauri-
dreams.org/?p=10123> . You need intermediary objectives to make interstellar
exploration a more realizable goal.

~~~
cosgroveb
I probably did the calculations[1] wrong but the value I'm getting for the
apparent magnitude of 55 Cancri B at 1000 AU with an absolute magnitude of
12.66[2] is about -3.9121 which, if located in our Solar system, would be
bright enough to see in daylight, despite being almost 35 times as distant as
Pluto is to the Sun.

[1]
[http://ceres.hsc.edu/homepages/classes/astronomy/spring99/Ma...](http://ceres.hsc.edu/homepages/classes/astronomy/spring99/Mathematics/sec19.html)
[2] <http://en.wikipedia.org/wiki/55_Cancri>

~~~
iwwr
Still, it won't look like 'two suns in the sky', but more like Venus.

~~~
cosgroveb
Definitely. It would look like a pretty damn bright star, but not like a
second Sun.

------
ck2
Maybe in 50 years we can get probes up to 10% light speed.

200-250 years to reach the planet and then another 20 years for the signal to
get back (if we can somehow make a signal strong enough).

So 300 years from now our great-great-grandchildren might know (that's 70
years longer than US history).

But we'd actually have to spend some of that war and terrorism industry money
on NASA and private investment to accomplish that. Not sure the politicians
would ever bother.

------
JohnIdol
"We're left, like the starving donkey equidistant between two bails of hay,
unable to decide on what to celebrate" <\-- the closest of these things is 20
light years :[

~~~
jsvaughan
The scale of space is shocking. The fastest man made object, Helios 2
(<http://goo.gl/xCow>), at 250000kph, would take 17000 years to get to the
next nearest star, Alpha Centauri.

This post by Charles Stross is worth a read:
[http://www.antipope.org/charlie/blog-
static/2007/06/the_high...](http://www.antipope.org/charlie/blog-
static/2007/06/the_high_frontier_redux.html)

To quote: "interstellar travel for human beings is near-as-dammit a non-
starter"

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sambeau
This is one of those stories that makes my internal 12 year-old want to post
the following comment and my 42 year-old too in awe to stop it:

"Cool!"

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radarsat1
In the habitable zone 74% of its orbit? Although it sounds great, I'm left
skeptical: to support life, wouldn't that need to be 100%?

~~~
cryptoz
It doesn't need to be 100% if the atmosphere of the planet could keep enough
heat for the remaining 26% of the time, which is entirely likely.

This find is awesome, but it's not what the headline describes. The planet is
no "ExoEarth". It's a fantasticly cool exoplanet that could very probably
support life that vaguely resembles life on Earth (not humans, though).

~~~
danking00
It looks like the planet actually slides closer in to the star, thus the issue
would be keeping the environment cool enough.

~~~
Roboprog
Closer to a smaller, cooler star.

~~~
danking00
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.

------
jcasman
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.

------
njharman
"That's weird! The sky on Cancri 55 f must be out of this world. "

Really, that's the quality of writing from MIT Technology Review?

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

Arrrgh.

------
lawlit
The planet was discovered in April 2005, nothing news.

~~~
JohnIdol
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>

~~~
lawlit
Well I guess you're wrong -->
[http://web.archive.org/web/20061216012023/http://www.aas.org...](http://web.archive.org/web/20061216012023/http://www.aas.org/publications/baas/v37n2/dda05/29.htm)

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

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

