APOD: Kepler 22b: An Almost Earth Orbiting... (2011 Dec 07)

[EdwinsMyHero]

I have a question about this SETI investigation:

Let's suppose that, 600 years ago, Keppler 22b was at exactly the same stage in technology that we are today. Is our SETI ability good enough to pick up their RF?

At a distance of 600 light years, what would the inverse square law do to their signal strength?

How much would background radiation mask it?

Steve J

[Chris Peterson]

The chances of finding life on any particular exoplanet in the universe must be millions:1 or billions:1 or even trillions:1.

Or perhaps nearly every planet in a habitable zone has life. With such as small sample as our own solar system to use for reference, there's simply no way of knowing. It may be hard for life to develop, or it may be rare for it not to.

The chances of finding intelligent life on that same planet must be astronomically higher again.

What does "intelligent" mean? If you mean "technological", I'd agree... given the incredibly tiny fraction of time that life has been present on Earth with that characteristic. But intelligence of some degree arose here early, and has proven itself hardy.

[zloq]

Let's suppose that, 600 years ago, Keppler 22b was at exactly the same stage in technology that we are today. Is our SETI ability good enough to pick up their RF?

I think the general topic of SETI detection would involve a lot of open speculation - but the way you posed it makes it better defined because the sending and receiving technology is known.

Here are two papers that talk about this question:

http://arxiv.org/ftp/arxiv/papers/1102/1102.1938.pdf

http://arxiv.org/PS_cache/arxiv/pdf/100 ... 0850v1.pdf

Off hand I didn't know if the answer was 0.1 light years or 1000 light years - but these papers have estimates based on possible signals and detection modes. One point is that the ambient radiation of normal communication on earth is low since the signals are directed downward or from point to point on the planet. There are separate beams into space for things like radar detection of asteroids - but they are transient. But for the specific case of a recent message sent from earth with a directed 70m radio dish, there would be a chance to detect it as an integrated energy pulse over hours of observing at a distance of 648ly using a planned square kilometer radio array (SKA).

Another point is that advanced civilizations might become more radio quiet, rather than louder, due to improvements in efficiency. Periods of radio noise might be brief blips in a civilization's development - aside from their attempts to communicate. But that part is more speculative compared to your more concrete detectability question.

So - based on the ballpark estimates in these papers, the ambient radio emission would not be detectable and recognizable very far away at all - but a directed beam at least has a chance to be detected as an overall energy pulse - as long as it is aimed with a big radio dish and monitored at the right time in the right direction with another big dish. That's partly why the one paper recommends we don't send such beams. Additionally, there would be a 1200 year wait for any reply - which probably doesn't look good in a grant application.

zloq

[neufer]

<<At 2.4 times the size of the Earth, Kepler 22b is substantially larger than Earth and may therefore have a different composition. For example, the newly discovered planet may not be Earth-like, but rather more like Neptune, which is mostly ocean with a small rocky core. Nonetheless, Natalie Batalha, one of the scientists on the project, speculated "it's not beyond the realm of possibility that life could exist in such an ocean.">>

Scary ancient sea predator sported big, dangling eyes
With large claws and toothlike serrations in its mouth, it was already menacing enough
By Jennifer Welsh: MSNBC 12/7/2011

[b][color=#0000FF]A face only a mother could love: The 3-foot-long super-predator Anomalocaris. Credit: Katrina Kenny and University of Adelaide[/color][/b]

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[b][color=#0000FF]One of the stalked eyes of Anomalocaris from South Australia with arrows pointing to the boundary between the stalk & visual surface, plus the intricate lenses preserved (inset). Credit: John Paterson[/color][/b]

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<<The biggest, scariest predator of the ancient Cambrian oceans just got a lot more menacing: Researchers have found a pair of fossilized eyes that show the beast had excellent vision.

"The animal itself has been known for quite some time, but we've never known the detail of the eyes," study researcher John Paterson, of the University of New England in Australia, told LiveScience. "It can tell us a great deal about how it saw its world and it also supports that it's one of the key predators during the Cambrian period."

The group of predators in question, which belong to the genus Anomalocaris, could reach more than 3 feet (1 meter) long and lived in shallow oceans more than 500 million years ago. The researchers call it the "world's first apex predator," because it had highly acute vision and was much larger than other animals in the ocean at that time. It also had large claws and toothlike serrations in its mouth to tear apart trilobites.

"When you look at the animal it has these really gnarly looking grasping claws at the top of its head, for grasping onto its prey," Paterson said. "It used these grasping claws at the front to shove its prey into its circular mouth, which is also fairly fearsome looking."

Previous fossils had preserved only the outlines of these creatures' eyes. Researchers knew the eyes were situated on stalks that protruded from its face, and they had thought the dangling eyes might be compound eyes, but weren't sure and couldn't tell how many lenses they might have had, or how sharp their vision might have been.

The eyes were discovered in a fossil from a 515-million-year-old deposit on Kangaroo Island, in South Australia. Other fossils discovered in this deposit show ancient eyes that aren't nearly as well developed, but still quite sharp compared with other animals of the day.

The fossils were pried from shale rock samples: "You split them along the really fine layers in the shale with hammer and chisel, like opening the pages of the book, and hopefully something will be looking back at you for the first time in 500 million years," Paterson told LiveScience. "I was actually the one that found the pair of eyes. That was a spine-tingling moment."

Compound eyes, the type of eyes seen in dragonflies and mosquitoes, are made up of multiple individual lenses. Dragonflies, one of the few living arthropods with similarly acute eyesight, have up to 28,000 lenses per eye, while a housefly may have 3,000. These 500 million-year-old creatures had around 16,000. Like pixels in a digital image, for compound eyes, more lenses mean a clearer picture. Based on the structure, this animal might have had an exceptionally clear, almost 360-degree view of the world around it, the researchers said. Such precise vision would have given these predators an advantage over their prey, which would need to evolve their own visual capabilities to avoid being eaten.

"It would have been very aware of its environment. It would have been a very capable predator, especially when you compare it to other animals in the same fossil sites that wouldn't have had as good of eyesight or could have even been blind," Paterson said. "Anomalocaris would have had a distinct advantage, I think."

The study will be published in Thursday's issue of the journal Nature.>>

[orin stepanek]

From the amount of replies this thread is getting; I'd say a lot of people are interested in the possibility of habitable planets out there.

[Chris Peterson]

From the amount of replies this thread is getting; I'd say a lot of people are interested in the possibility of habitable planets out there. 8-) :D

Habitable raises the possibility of inhabited. How can anybody not be fascinated by that?

[orin stepanek]

From the amount of replies this thread is getting; I'd say a lot of people are interested in the possibility of habitable planets out there.

Habitable raises the possibility of inhabited. How can anybody not be fascinated by that?

Oh! I am: There are people I know that say we are alone in the universe. While I guess that's possible; I don't believe that is very likely. Because of distances though; we may as well be! Sometimes I wish the neighboring stars were closer so we could go visit!

[ruprecht147]

A preprint of the discovery paper for Kepler-22b, by William J. Borucki and colleagues, is now available at archive.org. This paper demonstrates that Kepler-22 is a very interesting planetary system, but it also reveals that the hype we’ve been hearing about a “second Earth” or an “Earth twin” is largely or entirely a lot of media blather.

The star, Kepler-22, is a G5 dwarf similar to our Sun in mass, radius, and effective temperature. However, its metallicity (proportion of heavy elements to hydrogen) is only -0.29, whereas the metallicity of our Sun is 0. That means that the protoplanetary nebula where the Kepler-22 system formed most likely had a much smaller quantity of rocks and metals than the nebula in which the Solar System formed. Such an environment is not conducive to the formation either of gas giants like Jupiter or of massive rocky planets (i.e., scaled-up versions of Earth or Venus).

The radius and orbital period of Kepler-22b are well determined, so we know its size (2.38 times the radius of Earth) and its approximate temperature. However, as the discovery team notes, this information places virtually no constraints on the composition and internal structure of Kepler-22b.

According to the widely used models of Jonathan Fortney and colleagues (“Planetary Radii across Five Orders of Magnitude in Mass and Stellar Insolation,” 2007), if Kepler-22b had exactly the same structure and composition as the Earth, it would be more than 32 times as massive as Earth. In other words, it would be equivalent to the combined masses of Uranus and Neptune, except that this mass would be squeezed into a much smaller and denser volume. Because the parent star’s low metallicity rules out such a composition, we can safely conclude that Kepler-22b is not a rocky Super Earth, and thus not our big sister in the Galactic family of planets.

Again, according to Fortney’s models, a more physically plausible composition for a planet of 2.38 Earth radii would include at least 50% ice (along with rocks & metals) and yield a planet mass in the vicinity of 6 to 10 Earth masses. Kepler-22b would then be a scaled-up (and warmed-up) version of Ganymede or Titan, with the potential for a very deep global ocean surrounding an even deeper layer of ice. After the landmark study of A. Leger and colleagues (2004), such objects are typically called Ocean Planets. Whether such a planet would permit the genesis of living organisms (or make a congenial home for our descendants in the far future, a la Costner) is anybody’s guess, but the result would not be an Earthlike environment.

A fascinating and very recent study by Leslie Rogers and colleagues (“Formation and Structure of Low-Density Exo-Neptunes,” 2011) demonstrates that planets with structures similar to Neptune and Uranus – rock/ice cores with deep hydrogen atmospheres – can be formed with radii as small as 2 times Earth. At the orbital distance of Kepler-22b, such a Mini-Neptune could retain its hydrogen envelope for billions of years, and yet be only a few times heavier than Earth. As far as I understand, the atmospheric pressure implied by such an envelope would not permit the survival of liquid water, but others with a better knowledge of these things may wish to chime in.

In any event, it is far more likely that Kepler-22b is a Mini-Neptune, as theorized by Rogers et al., or an Ocean Planet, as theorized by Leger et al., than it is a sibling to our beautiful home. But the Kepler mission still has a long way to go, and we can be sure that many more fascinating planets will be revealed on this page over the next few years.

[Chris Peterson]

A preprint of the discovery paper for Kepler-22b, by William J. Borucki and colleagues, is now available at archive.org.

The paper can be found here.

With respect to an earlier discussion under this topic, I note that the planet is designated Kepler-22b, and the star is consistently designated Kepler-22 (not Kepler-22a). The more formalized name used for the star is KIC 10593626 (KIC is the Kepler Input Catalog). SIMBAD lists alternate catalog designations: Kepler-22, GSC 03546-02301, 2MASS J19165219+4753040, UCAC3 276-148830. The GSC and UCAC catalogs are commonly incorporated in star charting software, so those would be good catalog designators to use if you are interested in checking out this star yourself.

I don't know if the Wikipedia article is correct in stating that Kepler-22 is synonymous with Kepler-22a, but it is clear that in the discovery publication for this system, Kepler-22 is considered the proper designation for the star (and also for the system).

[zloq]

I don't know if the Wikipedia article is correct in stating that Kepler-22 is synonymous with Kepler-22a, but it is clear that in the discovery publication for this system, Kepler-22 is considered the proper designation for the star (and also for the system).

Yes - I consider that a good reference and it doesn't make a single reference to Kepler-22a. It only mentions Kepler-22 and Kepler-22b. Many of the references are ambiguous as to referring to the star or the system, but there are a few specific mentions of Kepler-22 as a star. They also never refer to the planetary system specifically, except as "this system." So they are only talking about the star, as Kepler-22, and the planet, as Kepler-22b - and there is never confusion in this specific context.

I guess if another paper were comparing planetary systems, it would use Kepler-22 and Kepler-16 to refer to the systems, and then use Kepler-22a and Kepler-16a as the stars in those systems. It would pretty much have to because otherwise the text would be ambiguous or full of unnecessary words like "star" and "system" to keep things clear. So in that sense - I still think it's unfortunate not to stick to the convention - because it does play a role of clarity in the overall field. This is particularly a pain in the neck when papers are automatically parsed and assigned metadata for searches. Oh well. I also think putting people up in space in a giant Winnebago is a bad idea - and NASA seems keen on that choice and is sticking to it. Granted, they do take some good timelapse movies out the window occasionally.

zloq

[Chris Peterson]

I guess if another paper were comparing planetary systems, it would use Kepler-22 and Kepler-16 to refer to the systems, and then use Kepler-22a and Kepler-16a as the stars in those systems. It would pretty much have to because otherwise the text would be ambiguous or full of unnecessary words like "star" and "system" to keep things clear.

I don't see that. In fact, I think most authors would go out of their way to avoid using the "a" suffix, which is confusing and contrary to how stars are typically identified. The proper, cataloged name of the star is Kepler-22, not Kepler-22a.

So in that sense - I still think it's unfortunate not to stick to the convention - because it does play a role of clarity in the overall field.

I actually think the paper does stick to the convention. This Kepler context is the only one I know of that refers to stars this way (and I don't actually see any references to it, outside the Wikipedia article). Otherwise, the convention is, and always has been, to use the same name for the star and for the system, and not to qualify the star with some letter (except in multiple star systems).

[Flase]

Does anybody know the latest on the hunt for exoplanets in the Alpha Centauri system? I do a web-search and don't find any recent news.

What if you find several exoplanets in the same system but you don't find them in the right order so that, say, in Alpha Centauri, you have AC-Bb further out from AC-Bd which is further still from AC-Bc? What is the naming convention?

[zloq]

I guess if another paper were comparing planetary systems, it would use Kepler-22 and Kepler-16 to refer to the systems, and then use Kepler-22a and Kepler-16a as the stars in those systems. It would pretty much have to because otherwise the text would be ambiguous or full of unnecessary words like "star" and "system" to keep things clear.

I don't see that. In fact, I think most authors would go out of their way to avoid using the "a" suffix, which is confusing and contrary to how stars are typically identified. The proper, cataloged name of the star is Kepler-22, not Kepler-22a.

So in that sense - I still think it's unfortunate not to stick to the convention - because it does play a role of clarity in the overall field.

I actually think the paper does stick to the convention. This Kepler context is the only one I know of that refers to stars this way (and I don't actually see any references to it, outside the Wikipedia article). Otherwise, the convention is, and always has been, to use the same name for the star and for the system, and not to qualify the star with some letter (except in multiple star systems).

Well I thought this topic was pretty much resolved - but now you are saying Kepler-22a is wrong altogether and the "formal" name for the star is Kepler-22 and never Kepler-22a. This means both the system (star and planets) and the star itself both have exactly the same name - which to me is undesirable. In most cases, exoplanet systems are described by themselves and this ambiguity would never be an issue - but whenever two systems are described both as systems and as individual components - the suffix is needed for clarity.

An example is: "Our solar system is similar to Kepler-22, but our sun is bigger than Kepler-22a while earth is smaller than Kepler-22b".

Who sets the rules? Well - the recent Science paper on Kepler-16 by Doyle says,

"Following the convention of (21), we can denote the third body Kepler-16(AB)-b, or simply “b” when there is no ambiguity."

In this case, the reference 21 is, "On the naming convention used for multiple star systems and extrasolar planets" by Hessman available at http://arxiv.org/abs/1012.0707

Looking at the examples in Hessman, the system Kepler-22 comprises Kepler-22Aa and Kepler-22Ab - which are then allowed to be shortened by rule 2. Additionally, the 'a' is implicitly allowed to drop when no ambiguity results - but my whole point is that ambiguity does arise when the star and the system are both described in the same context and so the 'a' should not be dropped in those cases. Either way - the 'formal' name for the star would be Kepler-22Aa, similar to his single-star example in Figure 1.

Hessman goes through many examples of the complex situations that arise, and where conventions have failed in the past. He also answers Flase's question regarding how names attempt to capture both the history of discovery and the dynamics of complex hierarchies of orbiting components - and the difficulties involved.

Hessman does not discuss the issue of searches and metadata that I mentioned, which is why I think the 'a' should never be dropped. Kepler systems are different from normal stars because they only exist as named entities by virtue of having a discovered component - so you always know the system involves at least one star and at least one planet. Never dropping the 'a' (or whatever the suffix is on the star(s)) keeps references to the star fully distinct from the system itself.

In my encouraging this, I am fully in the spirit of Hessman's letter, in which he says,

Naming conventions are not physically important – no one really cares if an object is called Sirius B, CMa Ab, GJ 244 #2, RXF J064508.6-164240, or “Rover”, but names convey both historical and physical information about the object and the naming convention used should at least not confuse. This is particularly true for the benefit of observers, who are definitely interested in knowing which object on the sky is meant by what name. Unlike the multiple star community, which is suffering from over a century of jumbled naming conventions, the exoplanet community is still sufficiently young that it is possible to adopt a uniform nomenclature which maximizes the usefulness of the names and minimizes the amount of confusion while consciously staying as close as possible to the provisional I.A.U. multiple star naming standard.

As long as papers come out talking about Kepler systems by themselves, there will be little ambiguity in dropping the 'a' on the star - though that will reduce the quality of metadata for searches. But papers comparing both system and star properties would suffer from ambiguity, and the 'a' would be needed. Either way, the 'a' is implicitly there by the convention, and when no problems arise it is dropped - as long as there is no ambiguity. Since the exoplanet community is young and papers are only now coming out on the discovered Kepler systems, I would avoid dropping the 'a' altogether when the star itself is specifically mentioned.

zloq

[Flase]

If we got to know the Alpha Centauri system well with several planets, they might start to be named after mythology like Jupiter and Mars. Fenrir's a good name, a monstrous norse wolf that bit off the hand of Tyr (after whom Tuesday is named).

[ruprecht147]

Does anybody know the latest on the hunt for exoplanets in the Alpha Centauri system?

What if you find several exoplanets in the same system but you don't find them in the right order . . .

I think that the Observatoire de Geneve and at least one other group are regularly observing the Alpha Centauri system, but the most recent reference I can find for this activity is a blog post by Greg Laughlin from 2009 (http://oklo.org/2009/08/29/lobbying-for-alpha-cen/). Nevertheless, you can be sure that if anybody ever finds anything, we'll see the headlines!

The recent articles relating to Alpha Centauri that I find in archiv.org are mostly theoretical -- there's still a lot of debate as to whether we can even expect to find any planets in this system, since it's a close, eccentric binary.

And of course, given its binary nature, Alpha Centauri actually consists of 2 stars: Alpha Centauri A (a G2 star similar to our Sun) and Alpha Centauri B (a cooler K1 star). The established naming convention for extrasolar planets is to assign the lowercase letter "b" to the first substellar object discovered in any star system, and then "c," "d," etc. to the objects discovered subsequently. The letters are assigned without regard to the separations of the planets from the star -- so that in one system, planet b might orbit inside planet c, but in another, planet c might orbit inside planet b.

I think everybody agrees that this system is incredibly boring and likely to cause confusion, and that it results in planet names that are just about impossible to remember, but there you go!

So, for example, if you list the 4 planets of GJ 581 in order of their distance from the host star, you get GJ 581 e, GJ 581 b, GJ 581 c, and GJ 581 d. If you do the same for the 5 planets of 55 Cancri, you get 55 Cancri e, 55 Cancri b, 55 Cancri c, 55 Cancri f, and 55 Cancri d.

55 Cancri is actually a binary system (as is Alpha Centauri), and the planet-hosting star is the brighter of the two, so it's officially 55 Cancri A. If you go with that official nomenclature, the planet names become 55 Cancri Ae, 55 Cancri Ab, etc.

But in practice, nobody does this. If planets are ever discovered around 55 Cancri B (a perfectly presentable M dwarf) then those practical naming conventions would need to be revisited.

Maybe by then we'll have actual names for planet-hosting stars, so that 55 Cancri A might become, say, Draupadi, and the 5 planets could be named after the mythical Draupadi's 5 sons: Prativindhya, Sutasoma, Srutakirti, Satanika, and Srutasena.

At least one can dream.

[Flase]

Maybe by then we'll have actual names for planet-hosting stars, so that 55 Cancri A might become, say, Draupadi, and the 5 planets could be named after the mythical Draupadi's 5 sons: Prativindhya, Sutasoma, Srutakirti, Satanika, and Srutasena.

The trouble with that idea is that you might find a sixth orbiting body and then you'd have to see if she had a dog or something. I'm guessing that idea would be better for a planet with moons.

Actually a system of letters and numbers is cool. For example in the movie Alien, the planet they visit is LV-426. Such a name helps give the impression that it is a god-forsaken hostile alien rock lightyears from anywhere...

[geckzilla]

Any planet not in our solar system is officially outside our celestial monkeysphere and only warrants structured, incremental naming.

[Beyond]

Any planet not in our solar system is officially outside our celestial monkeysphere and only warrants structured, incremental naming.

Outside our celestial monkeysphere OH! Someplace we can't get to, to screw up

[geckzilla]

http://en.wikipedia.org/wiki/Dunbar's_number

or, the humorous and vulgar version: (my favorite)
http://www.cracked.com/article_14990_wh ... phere.html

[Ann]

The idea of naming the extra-solar planetary systems out there after human gods is... okay, I guess, since no one but ourselves will probably ever know what we call them. After all, if an alien species a few hundred light-years away in space were to call the Sun or even the Earth KbZaZaŨpzAza, then what's that to us?

But I find it a little depressing to name all the interesting planetary systems after male gods and their sons. What is the cosmos out there, an infinity of Y chromosomes?

In any case, if we bear in mind how many alien solar systems we are likely to find out there, we may be running out of gods, whether male or female, before we are done naming them all.

Ann

[Chris Peterson]

In any case, if we bear in mind how many alien solar systems we are likely to find out there, we may be running out of gods, whether male or female, before we are done naming them all.

We're already scraping the barrel of obscure mythologies just to name objects in our own system!

[Flase]

Of course there are female names like Venus, Ceres and 4 Vesta.

[bactame]

If 22b is a water world this would perhaps be one of the best type of worlds to visit. Splashdown would be literal and if gravity were a too great your sinking could be salvation. As you sink the formation of a swim bladder could allow you to reach neutral buoyancy pretty quickly. Indeed having a choice between going to Mars or going to 22b i would choose 22b in a flash.

[Beyond]

http://en.wikipedia.org/wiki/Dunbar's_number

or, the humorous and vulgar version: (my favorite)
http://www.cracked.com/article_14990_wh ... phere.html

geckzilla, your favorite is also mine. But I'm not quite sure if that is a good thing or not.

[NoelC]

I wonder whether intelligent life, if it's possible to evolve for more than a few hundred years after embracing technology, wouldn't be communicating via means other than radio waves.

Looked at another way, if our successors are still around in a few thousand years, will they all be communicating via entangled photons, connections via dimensions outside our universe, or something REALLY advanced, even beyond our current imaginations?

Now, with that in mind, is it likely we'll hear them on the radio?

-Noel