Earth-like Exoplanets - Discussions & Developments

[MeteorWayne]

I did check, and none of Gliese 581's planets transit. The system of planets is tilted between 40 and 50 degrees to our view.

 

[Nehmo]

We don't know for sure, but considering the distance from the star, the tidal locking time would be less than the age of the system, so it's very likely.

" tidal locking time" is what, the time it takes a planet to stop spinning?

I searched, and found this by nummycakes http://arstechnica.com/civis/viewtopic. ... #p20864345
"Let's see... the wiki has the approximate timescale for tidal lock being:

... except for planet/satellite substitute star/planet.

The numbers are, from wikipedia, for star and planet:
a = 0.146 AU = 2.18e10m
radius of planet = 1.3-2 Earth radii = 8.3-12.7e6m = R
rigidity of planet ~ 3e10N/m²
mass of star = 0.31 solar masses = 6.16e29kg = M
mass of planet > 3.1-4.3 Earth masses = 1.8-2.6e25kg = m

Hence taking the minimum m and the maximum R:

Code:
t(lock) ~ 6 x (2.18e10)^6 x 12.7e6 x 3e10 / (1.8e25 x (6.16e29)²) x 10 billion years
~ 360,000 years


Gliese 581 is thought to be about 8 billion years old."

So, I suppose this means G581g would have locked in 360 k years? I'll have to review this. I'm posting while thinking.
~~ Nehmo

 

[MeteorWayne]

I haven't gone through all the numbers, my point was purely that the planet would have been tidally locked billions of years ago. Long before now

More detailed formula are here:

http://en.wikipedia.org/wiki/Tidal_locking

 

[Nehmo]

Another question is: How long would it take a (the space probe) Voyager http://voyager.jpl.nasa.gov/images/tour-l.jpg to reach Gl 581g, if it were shot in the correct direction?

V2 is now 12.8 light hours away in 33 years.
1 year = 8 765.81277 hours
V2 Now 0.00146 ly away
20.5 light-years to Gl 581g
0.46 million years for Voyager 2 to get there.


~~ Nehmo

 

[bdewoody]

Since everyone is speculating here I have wondered about something. Is it possible for a planet to have flora but no fauna or at least nothing higher than insects? And say we do happen across a planet with just plant life and we have a way to get there will the collective spirit of human kind allow ourselves to colonize such a planet or will the so called "prime directive" from the Satr Trek mentality prevent us from going there. When I say us I am referring to our decendants a few millenia from now.

 

[MeteorWayne]

That's not fair; you should have used Voyager 1. It's 114.886 AU from the sun (further along the way), moving faster (3.601 AU/yr), so if it were aimed in the right direction, would reach Gliese 581 in only 356,235 years~

MW

 

[EarthlingX]

www.newscientist.com : How to find out if exo-Earths host life

06 October 2010

by David Shiga

SO CLOSE, yet so far. Gliese 581 g is the first planet discovered that is the right mass and distance from its star for the surface to be awash with liquid water and perhaps life. Chances are we'll never know for sure without an armada of space telescopes, and their future looks uncertain. But a 2014 mission could tell us whether any habitable worlds with better viewing angles have signs of life.

...

To find evidence for life we would need to measure the light spectrum of the planet's atmosphere and look for the signature of water vapour, as well as possible by-products of life, such as oxygen and methane.

That would mean launching an expensive array of space telescopes to tease out the faint glow of the planet from the powerful glare of its star. NASA and the European Space Agency were hoping to launch such a mission in 2014, called the Terrestrial Planet Finder (TPF), or Darwin.

But in 2006 NASA backed away from the mission, postponing it indefinitely to free up more funds for human space exploration. Darwin/TPF was dealt another blow this August, when a key panel of US astronomers failed to recommend its construction in the next decade.

...

 

[SpacedCase]

Its disheartening to hear how steeply inclined 581g's orbit is. So it seems there isn't much near-term hope of additional information. I'd had a thought that "g" might turn out to be a binary planet and so not tide-locked, etc. Can the wobble method tell if it does have a large satellite or twin? I recall reading that moons might be inferred by their varying effect over hundreds or thousands of orbits. I suppose the closer in mass any such pair might be, the harder it would be to see an effect of one compared to the other upon their primary. Or does that only work with the transit method? No spectra. Nuts.

Too bad the solar focus is well out of reach. Now that I think about it, why can't Jupiter be used for gravitational lensing instead? I'm sure the magnitude of it would be much smaller, but it would also be a heck of a lot easier to reach the focus. Wouldn't it? I guess its been considered and ruled out.

Though, shouldn't even the Earth produce such lensing? I am completely ignorant here, and not proud. I'm guessing a linear relationship between mass, distance to focus and resolving power. And I'm also assuming I'm wrong...

Edit
No not linear at all. Now that I've looked around it seems gravity-lensing requires a focal length around 15000au for Earth and about 55000au for Jupiter. Compared to ~550au for Sol. FAIL. Well, I was right about being wrong.

Edit 2
I think that should be ~5500au for Jupiter. Drowsy post...

 

[EarthlingX]

http://www.physorg.com : Discovery of an extrasolar earth-sized planet

October 8, 2010


An artist's conception of the extrasolar planetary system around the star Kepler-9. Astronomers have discovered an earth-sized planet in this system. Credit: NASA, Kepler, T. Pyle

(PhysOrg.com) -- There are now over 490 confirmed extrasolar planets. The vast majority are gas giants like Jupiter, but they are much stranger because many orbit close to their stars and so are much hotter than Jupiter (some are even closer to their star than Mercury is to the sun).

...

The quest for other earths is making good progress, however. Writing in the latest issue of the journal Science, a team of twelve CfA astronomers led by Matt Holman, together with a large group of colleagues, report using Kepler to discover an earth-sized extrasolar planet. They carefully analyzed the orbital motions of two Saturn-sized extrasolar planets in the system known as Kepler-9, and found that by meticulously accounting for their motions they could subtract their effects to hunt for even smaller dips, as small as 0.02% in stellar intensity.

They report finding a planet whose size is only about 1.5 earth-radii, making it one of the smallest extrasolar planets known. This planet orbits the star (its "year") in only 1.5924 days, however, and so it is very close to its star, hot, and thoroughly unearth-like. Nevertheless it represents a major step forward in the search for small planets. Unlike other recent discoveries (like that of a planet in its habitable, "Goldilocks," zone but considerably larger than the Earth), this new planet is small enough to raise expectations and the excitement for soon discovering extrasolar earths.

..


arxiv.org : Modeling Kepler transit light curves as false positives: Rejection of blend scenarios for KOI-377, and strong evidence for a super-Earth-size planet in a multiple system
...

The high-precision light curves from the Kepler mission contain valuable information on the nature of the phenomena producing the transit-like signals. To assist in exploring the possibility that they are the result of an astrophysical false positive, we describe a procedure we refer to as BLENDER to model the photometry not in terms of a planet orbiting a star, but instead as a "blend". A blend may consist of a background or foreground eclipsing binary (or star-planet pair) whose eclipses are attenuated by the light of the candidate and possibly other stars within the photometric aperture. We apply the technique to the case of KOI-377, a particularly interesting Kepler target harboring two previously confirmed Saturn-size planets (Kepler-9 b and Kepler-9 c) showing transit timing variations, and an additional shallower signal with a 1.6-day period that would correspond to a super-Earth with a radius of 1.4 R(Earth), the smallest yet discovered. Using BLENDER together with constraints from high-resolution imaging, spectroscopy, and astrometry (centroid motions), we are able to rule out all blends for the two deeper signals and provide independent validation of their planetary nature. For the shallower signal we rule out a large fraction of the false positive scenarios that might mimic these transit-like events. The false alarm rate (FAR) for remaining blends depends in part (and inversely) on the unknown frequency of small-size planets. Our most conservative (smallest) estimates of this frequency lead to a FAR of 0.0059, implying a high likelihood that the signal is due to a super-Earth-size planet rather than a false positive.

...

http://en.wikipedia.org/wiki/Kepler-9 (updated)

Kepler-9 is a star slightly more massive than the Sun, located in the constellation Lyra in the Kepler Mission's field of view. The star has two, possibly three, planets, which were discovered using the transit method. This multi-planet planetary system is the first to be discovered via the transit method.

...

 

[xXTheOneRavenXx]

If we are going to end up in stalemate debates over whether an earth-like planet is actually habitable or not, what is the point of searching for them if we can never in our life-time answer this question? Sure they will remain cataloged somewhere until such time we do get funding for a large enough telescope to detect the composition of their atmospheres.

 

[EarthlingX]

SDC : 500th Alien Planet Could Be Discovered This Month

By Mike Wall
SPACE.com Senior Writer
posted: 12 October 2010
12:50 pm ET



Less than 20 years after first finding a planet beyond our solar system, astronomers are poised to hit a big milestone — the discovery of alien world No. 500.

As of Tuesday (Oct. 12), the confirmed tally stands at 494 extrasolar planets, with more than 70 discovered so far in 2010 alone. At that rate, No. 500 could be announced before October is out — just a month or so after another watershed moment, the discovery of the first potentially habitable alien planet.

"Where we are, I'd expect that by the end of October, we'll be at 500 if things keep going the way they're going," said Jon Jenkins of the SETI (Search for Extraterrestrial Intelligence) Institute. Jenkins is the analysis lead for NASA's planet-hunting Kepler mission.

And the 1,000th world could be discovered surprisingly soon, as the space-based Kepler mission has already offered up hundreds of planet candidates that await further observation and confirmation.

...

Other important milestones could follow closely on the heels of exoplanet 500, not all of them numerical. One big moment that should happen relatively soon, Jenkins said, is the discovery of a potentially habitable alien world that's transiting its star, a setup that would allow for more detailed observations.

...

When a planet transits its parent star, starlight passes through its atmosphere (if the planet has one). Astronomers can scrutinize this light for compelling evidence of life in the planet's air, such as significant quantities of both methane and oxygen. As one example, a gas giant planet called HD 209458b has been found to contain oxygen, carbon and water.

So the discovery of a transiting Earth-like world in its parent star's habitable zone — that range of distances that supports the existence of liquid water — would occasion some celebration in planet-hunting circles, as well as a frenzy of follow-up research. And it could be just around the corner.

"I wouldn't be surprised if that happened next year," Jenkins said.

 

[MeteorWayne]

It was stuck on 490 for a few weeks, then 492 and now 494 in another 10 days or so. I expect a big data dump will all of a sudden put the count way over 500

http://exoplanet.eu/catalog.php

MW

 

[EarthlingX]

http://exoplanet.eu/catalog.php :

update : 13 October 2010
All Candidates detected 496 planets

[youtube]http://www.youtube.com/watch?v=9Ji_GdAk9vU[/youtube]

AMNHorg | October 14, 2010

Join astrophysicist and Hayden Planetarium Director Neil deGrasse Tyson as he hosts and moderates a panel discussion dedicated to the perennial question "Is Earth Unique?" With what we now know about the stars in our galaxy and the planets that orbit them, we can begin to address this question with informed debate.

Panelists are selected for their diverse expertise in geology, biology, chemistry, and physics and for the ways they have applied these fields to address the past, present, and future of planet Earth.

This event is a special Asimov Panel Debate in celebration of the Rose Center's 10th Anniversary. For more information, visit http://www.amnh.org

 

[TheAnt]

In related news: Beta Pictoris b have now been directly imagined.

The text also details why we yet cannot imagine planets closer to the host star with this tech.

http://www.sciencedaily.com/releases/20 ... 105935.htm

 

[EarthlingX]

In related news: Beta Pictoris b have now been directly imagined.

The text also details why we yet cannot imagine planets closer to the host star with this tech.

http://www.sciencedaily.com/releases/20 ... 105935.htm

Yes, and here's a thread started about it :

No longer "blinded by the light"


Two planets have been retracted :

exoplanet.eu : Interactive Extra-solar Planets Catalog

update : 15 October 2010
All Candidates detected 494 planets

 

[TheAnt]

EarthlingX wrote: "Yes, and here's a thread started about it :"

Aha, 4 hours later, was asleep them, but yes I jump over there. I had the thought of confirmed and retracted planet claims in mind also.

 

[EarthlingX]

EarthlingX wrote: "Yes, and here's a thread started about it :"

Aha, 4 hours later, was asleep them, but yes I jump over there. I had the thought of confirmed and retracted planet claims in mind also.

That thread was started

Fri Oct 15, 2010 1:45 UTC

and you posted

Fri Oct 15, 2010 23:15 UTC

or 21h 30 min later.

No big deal, just to get facts straight. Perhaps you were not awake yet ?

 

[EarthlingX]

www.thespacereview.com : SIM and the “ready, aim, aim” syndrome

by Philip Horzempa

Monday, October 18, 2010

While the space community’s attention has been diverted by the continuing debate over the fate of the Constellation human spaceflight program, an equally momentous controversy has been brewing in NASA’s Astronomy division. It may sound absurd, but NASA is on the verge of pulling the plug on the search for other Earths orbiting nearby stars. While it will continue with a low-level effort to detect giant “unearthly” planets, those are not the worlds that hold out much hope to be life-supporting.

Right now, we humans are on the threshold of being able to find twins of our Earth. This would be the fulfillment of years of effort to answer one of the “Big Questions” of civilization: “Are we alone in the universe?” Instead of charging ahead, with gusto, to address this issue, the space agency is reluctant. It appears about to turn aside from this grand challenge. This momentous change in NASA’s vision is taking place under the radar of public attention.

...


Related, older news :

www.nature.com : No scope for agency collaboration in space

Published online 29 September 2010

Adam Mann

It ought to be a match made in heaven. Two telescopes — one European, one American — with similar research objectives and a combined price tag of more than US$2 billion are both looking for support from funding agencies and the scientific community. In the current budget climate, it would seem natural for the projects to combine forces and push for one joint mission. Instead, it seems that in about a dozen years' time there will be two orbiting observatories doing the same job.

...

 

[EarthlingX]

blogs.discovermagazine.com : Gallery of exoplanets: real pictures of alien worlds

October 18th, 2010 7:00 AM

Phil Plait

In 1994, finding planets orbiting other sun-like stars was still something of a dream. Then, just a year later, the first one was found, opening a floodgate of discoveries.

We know of nearly 500 other planets orbiting other stars. However, the methods of finding these exoplanets are indirect. We measure their effect on their parent stars, but we didn't directly see the planets themselves... until 2005, when the first image of an actual world orbiting another star was announced.

As of October 2010, only 7 such planets have been imaged, but we'll soon have more. This gallery shows the best of these images, including the first alien solar system to have its picture taken.

...

 

[MeteorWayne]

Apparently there has been another dispute/retraction...the Extrasolar Planets Encylopedia Catalog is down to 493.

 

[xXTheOneRavenXx]

So does anyone know if there has been a finally ruling on Gliese581 g?

 

[MeteorWayne]

Well, there's no such thing as a final "ruling"...just the methodical collection of data and analysis as the scientific process moves forward.
I haven't seen any recent news.

 

[EarthlingX]

sci.esa.int : New roadmap to guide ESA in search for exoplanets

28 Oct 2010

The idea of other planets hidden in the vastness of space has long captured human imagination and there has been a recent explosion in the number of exoplanets discovered, with the total fast approaching 500. As the research community heads towards this milestone, ESA called on them for recommendations on how the Agency could build upon this success. The result is a recently published roadmap from the Exoplanet Roadmap Advisory Team (EPR-AT), which looks at the future of the field and how to reach their ultimate, long-term goal: finding an Earth-like planet with possible signatures of life.

Finding a twin of our own planet has long been the holy grail of exoplanet research. But whilst it represents the end destination for the new roadmap, the journey is equally important as it allows a better understanding of exoplanets and exoplanetary systems themselves. The authors of this roadmap, who come from research institutions across Europe, focus on three key areas: the continued detection of ever smaller exoplanets, the characterisation of their internal structure, and analysing the composition of their atmospheres, including the search for biosignatures.

Biosignatures would provide the best indication yet of life on other worlds but are likely outside of the realm of present-day facilities. Broadband photometry or low resolution spectroscopy from ground-based telescopes can already reveal some molecular species in exoplanetary atmospheres, but detection of actual biosignatures on small, Earth-like planets will likely require future, dedicated facilities, on ground and in space.

"Space telescopes aren't just important because they can find smaller planets," notes Malcolm Fridlund, Secretary for EPR-AT. "They also provide more detail than can be achieved from the ground, such as spectroscopic information about terrestrial atmospheres."

Such research illustrates a shift in emphasis; as space missions like Kepler and COROT detect more and more planets it is no longer satisfactory just to find them, researchers want to characterise them too in order to conduct detailed comparative planetology. Ground-based telescopes, equipped with highly sensitive spectrometers, are also crucial in both following up the initial space-based detection and analysing the planet's characteristics. With this synergy in mind the authors of the report make recommendations across three broad categories: ground, space and technology.

The complete report, A European Roadmap for Exoplanets, prepared by the ESA-appointed Exoplanet Roadmap Advisory Team (EPR-AT) is available to download here.

There may, however, be a catch in one hypothesis underpinning the search for a 'second Earth'; having a terrestrial mass might not necessarily make it an analogue of the Earth. "We cannot make an effective search for terrestrial planets until we properly understand what that term means. Recently two small bodies with approximately the same mass and not too different diameter have been found. One of them has characteristics compatible with its being made of iron and rock, the other of ice and rock: are both terrestrial?" asks Fridlund. By travelling down the route outlined by EPR-AT the community will be able to better define what they are looking for. "Answering this question will help lead us to the ultimate goal of finding out if there is life elsewhere in the Universe," Fridlund adds.

...



Interactive Extra-solar Planets Catalog :

All Candidates detected 494 planets

 

[EarthlingX]

keckobservatory.org : Study says solar systems like ours may be common

Kamuela, HI, Oct. 28, 2010

- Nearly one in four stars like the Sun could have Earth-size planets, according to observations of nearby solar-mass stars made with the Keck telescopes in Hawai’i.

UC Berkeley astronomers Andrew Howard and Geoffrey Marcy chose 166 G and K stars within 80 light years of Earth and observed them for five years in order to determine the number, mass and orbital distance of any of the stars’ planets. The Sun is the best known of the G stars, which are yellow, while K-type dwarfs are slightly smaller, orange-red stars.

The researchers found increasing numbers of smaller planets, down to the smallest size detectable today – planets called super-Earths, about three times the mass of Earth. The census, funded by NASA and the University of California, is the most extensive of its kind to date.

“Of about 100 typical Sun-like stars, one or two have planets the size of Jupiter, roughly six have a planet the size of Neptune, and about 12 have super-Earths between three and 10 Earth masses,” said Howard, a research astronomer in UC Berkeley’s Department of Astronomy and at the Space Sciences Laboratory. “If we extrapolate down to Earth-size planets – between one-half and two times the mass of Earth – we predict that you’d find about 23 for every 100 stars.”

“This is the first estimate based on actual measurements of the fraction of stars that have Earth-size planets,” said Marcy, UC Berkeley professor of astronomy. Previous studies have estimated the proportion of Jupiter and Saturn-size exoplanets, but never down to Neptune’s and super-Earths, enabling an extrapolation to Earth-size planets.

“What this means,” Howard added, “is that, as NASA develops new techniques over the next decade to find truly Earth-size planets, it won’t have to look too far.”

Because the researchers detected only close-in planets, there could be even more Earth-size planets at greater distances, including within the habitable zone located at about the same distance as Earth is from the Sun. The habitable, or “Goldilocks,” zone is the distance from a star neither too hot nor too cold to allow the presence of liquid water.

The researchers’ results conflict with current models of planet formation and migration, Marcy noted. After their birth in a protoplanetary disk, planets had been thought to spiral inward because of interactions with the gas in the disk. Such models predict a “planet desert” in the inner region of solar systems. The new study finds a surplus of close-in, small planets. “These results will transform astronomers’ views of how planets form,” Marcy said.

Howard and Marcy report their results in the Oct. 29 issue of the journal Science.

...

 

[EarthlingX]

http://www.space.com : 500th Alien Planet Discovered, With Hundreds More to Come

By Mike Wall
SPACE.com Senior Writer
posted: 22 November 2010
04:41 pm ET

The 500th alien world appears to have been discovered, according to extrasolar planet trackers.

Less than 20 years after confirming the first planet beyond our own solar system, astronomers have bagged exoplanet No. 500. The milestone was reached Friday (Nov. 19), according to the Extrasolar Planets Encyclopedia, a database compiled by astrobiologist Jean Schneider of the Paris-Meudon Observatory.

As of today (Nov. 22), the count stands at 502 alien worlds, the database reports.

The 500th extrasolar planet was reported in the midst of the discovery of several others. And there's always the risk a previous discovery turns out to be a false alarm, dropping the count.

For such reasons, it makes little sense to permanently anoint one particular world as "exoplanet 500," Schneider told SPACE.com.

That being said, the 500th alien planet currently appears to be one of four newfound extrasolar worlds, based on Schneider's list. They appear on the list just after another extrasolar planet, HIP 13044 b, which astronomers announced last week to be from an alien galaxy.

...


Interactive Extra-solar Planets Catalog :

update : 22 November 2010

All Candidates detected 502 planets