Smallest exoplanet yet found

By Phil Plait | February 3, 2009 3:00 pm

The record for the smallest planet orbiting a sun-like star has once again been broken. The newest planet to hold the record in its tiny hand is COROT-Exo-7b, which has only twice the diameter of the Earth!

Drawing of smallest planet found around another star

COROT is a European satellite that stares at stars and looks for tiny drops in their brightness. There are many causes of such events, but one is from a planet passing in front of the star, making a mini-eclipse. This has a distinctive signature in the way the light of the star dims, so a planetary transit can be distinguished from other sources.

We know so much about the way stars behave now that by looking at how much the star dims, we can get a decent handle on the size of the planet (a big planet blocks more light, and a smaller one makes a smaller dip). In this case, the planet has a diameter of about 25,000 kilometers or so. That’s far smaller than the usual "hot Jupiters" detected, which are more than 100,000 km across. Like them, however, it’s very close to its parent star: it only takes about 20 hours to make an orbit! Even Mercury takes 88 days to round the Sun, so this new dinky ball must be practically touching the surface of its sun. Even though the star is a K0 type (slightly cooler than the Sun), the surface temperature of the planet must be well over 1000 C. Just so’s you know, this system is over 450 light years away from us.

The big questions is, what’s the mass of this planet? These observations cannot determine that; they only get its size. To find its mass, astronomers will have to take spectra of the star and look for a shift in the wavelengths from the Doppler shift as the planet tugs the star. I have not read the journal paper for this discovery — it’s not published yet — but it seems to me that kind of observation may still be beyond our current technology. The planet may not have enough mass to pull on the star hard enough for us to detect it.

Until we know that, we can’t say much about this little guy. Is it solid metal, or rock? What characteristics does it have? We simply don’t know. I’ll add that a lot of news stories — even the press release itself — are saying this is a planet that has a surface we could walk on. That’s baloney, no matter what. First of all, walking on a surface glowing red hot may be your idea of a fun perambulation, but it ain’t mine! Second, if the planet is rocky, the surface may very well be molten. Third, planets have surprised us before. While I doubt this is a gaseous body, we simply don’t know enough about it to say much about it past its size and temperature. In other words, saying anything more is pure speculation, and should be regarded as such.

Still, a planet this size strongly implies it’s rocky, like Earth, as opposed to a gas giant like Jupiter. We are very, very close to detecting an Earth-sized planet orbiting another star, maybe even one in an Earth-like orbit. I wouldn’t be surprised if we find one in the next year or two… but even then, we won’t know much about it besides its size and temperature. But that’s certainly enough to make for some exciting news!

Image credit: CNES

CATEGORIZED UNDER: Astronomy, Science

Comments (69)

  1. Davidlpf

    Wow, but we won’t be sending a landing team down there.

  2. Scott

    The gas giants are thought to have rocky cores, perhaps as big as the Earth. Could this be the rocky core from a very large gas giant that had its gas stripped/boiled off after getting close to its star?

  3. T_U_T

    wow what a crazy world. most probably tidally locked. One side molten, yellow glowing , other side dark with ethernal ice.

  4. Ken_g6

    Being that close to its star, I would be surprised if its mass can’t be found.

    I believe we’ve found the masses of Jupiter-mass planets at >1au from their stars. So since Jupiter is ~300 Earth masses, and gravity decreases with the inverse square of distance, any Earth-massed planet within 0.05au of its star should be detectable.

    I’m sure with some real distance/mass values you could get an even better estimate.

  5. tacitus

    It would be interesting to know if a planet that small could have a cool enough surface on the dark side to walk on, assuming it is tidally locked. I guess it would depend on how the blazing heat from the star is dissipated through the crust towards the night side.

    Anway, kudos to COROT. Their initial testing confirmed that they might be able to detect Earth-like planets — something which was beyond the initial parameters of the mission, btw — and now that promise is bearing fruit. Let’s hope that they’re able to keep the telescope operating long enough to detect such planets out in the habitable zone. I suspect that’s what they’re shooting for, even now.

  6. Thanks for the ‘splainer Phil — looks like we’re on the same page about this one. Also, I made up a size comparison graphic here: http://tinyurl.com/rocky-exoplanet You’re welcome to borrow.

  7. quasidog

    Awesome. 450 light years away? wow.

    That amazes me .. but also depresses me a bit too. I find it amazing that humans have the ability now to detect anything other than the light coming from a star that far away (let alone its shift in relative brightness) and after that detect planets. 450 light years ?! damn.

    It also depresses me slightly as at those distances we pretty much don’t have the opportunity to visit them (for a long long time) even with robot probes. It would pretty much suck in that respect if we could detect something that far away that was able to be colonised. I am really interested more so in the planets we can detect in the first 10 – 50 light years from us, as being so much more close to home sheds a little more hope on finding a planet like ours.

    Man that would be cool. Still .. its a long way to go regardless.

  8. Considering how close it is to its sun, it must be a pretty dense body to withstand tidal forces. Would an ordinary rocky planet like Earth be able to do that?

  9. Itzac

    Can’t you calculate the mass from the orbital period, orbital distance, and mass of the star? Or is one of those quantities still unknown?

  10. Crux Australis

    Dibs not on the away team!

  11. They have found the mass: 5 – 11 earth masses. If you go to exoplanet.eu, and click on the headline for CoRoT Exo-7-b you get to the page with the estimated radius and mass (and references).

    Interesting to compare Gliese 581c, no?

  12. Casey10s

    On Dave Mosher’s site he states it is 1/2 the size of earth but here, Phil states it is twice the size of Earth. On another note, how can one tell that the planet is a small planet close to the star rather than a big planet far way from the star? Does it has to do with calculating the mass of the star and determining what the time the planet should make a complete circle based on gravity calculations?

  13. Very cool (pardon the juxtaposition of terminology there)! :)

  14. gopher65

    Scott:

    That’s what I’m thinking too. This could well be a gas giant that has had its “atmosphere” (if you want to call it that) stripped off by the heat from the star.

    Do we know how old this star is?

  15. Sindragosa

    I remember reading an equation (I think it was the Drake equation, not sure) to find the probable number of intelligent races in our galaxy in Carl Sagan’s Cosmos. I dont have my copy right now but I think he made as estimation of the number of stars that have planetary systems.

    Now that we have much more accurate data about exo-planets, I wonder by how many degrees of magnitude the Drake equation today would differ from the one in Sagan’s book. Far beyond his wildest hopes I would assume. I wish he were here to see this.

  16. IVAN3MAN

    According to Wikipedia, the distance from the Sun/Earth of CoRoT-Exo-7b is 119.492 pc (390 light-years).

    The images below are from the Observatoire de Paris web-site:

    CoRoT-Exo-7b
    Image of star around which orbits CoRoT-Exo-7b.
    Credit: CFH telescope (Canada-France-Hawaii).

    Light curve of CoRoT-Exo-7b
    Light curve, revealing the transit of the planet in front of its star.
    (Click on either image for more detailed information.)

  17. Tony

    We are very, very close to detecting an Earth-sized planet orbiting another star, maybe even one in an Earth-like orbit. I wouldn’t be surprised if we find one in the next year or two…

    Phil — you should set up a prediction about when an Earth-size planet (in an Earth-like orbit?) will be discovered on LongBets.org.

  18. @ Tony,

    No, he’s saving that prediction up for the JREF Million Dollar Challenge. I hear the President has some influence with Dr. Plait. ;) :P

  19. MadScientist

    @Itzac: the period of revolution about the star can only tell us how far the planet is (assuming we know the mass of the star). The mass (unless comparable to the star!) has no effect on the distance or speed. If you were to orbit the earth in a space suit and at the same distance as the international space station, you’d be travelling just as fast as the space station despite the huge difference in mass – well, at least our best measurement techniques can’t tell the difference.

  20. Wow very cool. Thanks for letting me know. Probably has a lot of mass!

  21. pablo

    Phil, can you address the phenomenon of “hot Jupiters”? Years ago when i was an astronomy minor, I was taught that planetary system formation was heterogeneous, and that only terrestrial planets could form near a star.

  22. amphiox

    If this (or any hypothetical) planet was once the rocky core of a gas giant that had its atmosphere stripped away, or if it was originally and still is a terrestrial type rocky world, how would we be able to tell?

    And would this difference in historical origin have any significant bearing on the properties and qualities of the planet as it might be observed in the present? (Assuming that any gas that might or might not have been stripped away has been gone for a sufficiently long time)

  23. StevoR

    Awesome news! 8) THX BA.

    Could be astripped down HotJove core – or perhaps one of the carbon-based Diamond planets speculated about..

    Could be molten on one side although with an atmosphere and surely aplanet thatsize wouldhave one, I’d think theheta would be conducted around thesurface to the “dark side” too. Anmazung place to contemplate -I’d be on any away team – just give me a *very* heat-proof suit! ;-)

    The BA :

    “First of all, walking on a surface glowing red hot may be your idea of a fun perambulation, but it ain’t mine!”

    Sounds like strollng along Adelaide streets right now. We’re justabout use dtoredhot surfaces by now. Our South Australian heatwave is continuing albiet not quite so bad. Only 35 degrees Celcsius outside today after a week of 40 plus degrees. (For Fahrenheiters 38oC = 100 F I think. Wish you’d all get with the celscius system – and go metric too for that matter! ;-) )

    @ Pablo The Hot Jupiters (sometimes called Pegasids) formed further away from their stars and migrated inwards to their current scorching positions. At least that’s the current orthodoxy …

  24. StevoR-Correcting

    Typos! Arrgh! :-( When is the editingcapabilitycoming pleaseBA. This is so frustrating. I could swear the errors weren’t in the post when I sent it …

    TAKE II :

    Could be a stripped down Hot Jove core

    … Or perhaps one of the carbon-based “Diamond planets” speculated about for some years. Carbon-rich material not silicon-rich as our solar system could produce carbon planets with tarry surfaces, smoggy carbon monoxide (think ’twas) atmospheres and diamond layers below the surface, or maybe even exposed to the surface? Was an ‘Astronomy’ mag article on this idea some years ago.

    Could be molten on one side although with an atmosphere and surely a planet that size would have one, I’d think the heat would be conducted around the
    surface to the “dark side” too. Amazing place to contemplate. I’d be on any away team – just give me a *very* heat-proof suit! ;-)

    The BA :

    “First of all, walking on a surface glowing red hot may be your idea of a fun perambulation, but it ain’t mine!”

    Sounds like strollng along Adelaide streets right now. We’re just about used to walking on red hot surfaces by now. Our South Australian heatwave is continuing albeit not quite so bad. Only 35 degrees Celcsius outside today after a week of 40 plus degrees.

  25. StevoR-Correcting

    D’OH! Make that :

    When is the editing capability coming please BA?

    Serious Phil so many blogs for so long have edit /preview and dlete facilities why is it so hard to provide such here? It’d make this already superb blog just so much better. Please!

  26. News Just In (surprised the BA hasn’t posted on this yet!) :

    Iran has just launched its first all-Iranian satellite.

    Via Wikipedia (click my name to visit link) :

    “Iran launches Omid, the nation’s first domestically constructed satellite :

    Omid (Persian : meaning “Hope”) is Iran’s first domestically made satellite.Described as a data-processing satellite for research and telecommunications, Iran’s state television reported that it was successfully launched on February 2, 2009. After being launched by an Iranian-made carrier rocket, Safir 2, the satellite was placed into a low Earth orbit. The launch coincides with the 30th anniversary of the Iranian Revolution and was supervised by President Mahmoud Ahmadinejad who launched the satellite with the words “Allāhu Akbar”. He said the satellite was launched to spread “monotheism, peace and justice” in the world.”

    Wikipedia also has the “smallest exoplanet yet found!” news discussed here -Thanks BA – & today’s featured article is on Makemake the dwarf planet.

    French astronomers discover COROT-Exo-7b, the smallest exoplanet to have its diameter measured

  27. Okay link didn’t work – try this one instead .. Click my name.

  28. Hmmm .. still not. The Wikipage ‘Omid satellite’ is there though. Maybe too recently created a page?

  29. Quiet Desperation

    TINY PLANET HAZ GOTS TEH CUTES!

    We’ll need a Cute Planet Overload site, soon. ;-)

  30. StevoR

    Thanks Asimov Fan & congratulations Iran & its Omid satellite team!
    Well done Iran, well done! :-)

    Folks I think this is a very good thing & I think people’s fears of Iran stem from an ignorance fed the media and Israeli lobby. :-(

    Iran has far more to fear from us than we do from it.

    Iran is not the cardboard cartoon villian all too many people in America & the wider “Western” world seem to think it is – it is a complex, rich and diverse country withalongerand deeper historyof civilisation than the USA’s and most other nations globally. Iran deserves to be respected and better understood than it is and has been the victim of US and other Western attacks on many occassions – not least during the Iran-Iraq war where America used Saddam Hussein’s dictatorship as an expedient proxy to attack the Islamic Republic.

    Moreover, Israel far from being in danger itself is the danger for that region. Israel has attacked its neighbours many times still occupies and persecutes its Palestinean neighbours and has provoked an incredible level of violence and all-too-well justified hatred because of its actions as an apartheid military theocracy where Jews are priviledged over non-Jews.

    I, for one, am looking forward to the day Iran when does get a reasonable
    nuclear deterent against American and Israeli attack. Such a development would make the world a far more balanced, peaceful and stable place as Israel and the US would at least need to think twice before launching yet another needless American war on another largely innocent country.

    If Israel cannot learn to live in peace with its Muslim, Christian and other neighbours it is time they seriously considered evacuating their nation and resettling it back in Europe or the US.

    As for the much over-hyped fear that Iran is in league with terrorists and would give them WMDs – don’t be silly – the Iranians are just NOT that stupid and know all too well what the consequences would be. After all, they’ve lived continously with the terror that Israel or the USA would use such WMDs on them. The term “terorist” is, of course, a matter of opinion.

    Posted in anticipation of those loony neo-con fans still out there… :-(

  31. Sundance

    @StevoR

    While I agree with you in principle on several political points you’ve just raised (and apparently you’re even a fellow South Australian :-) ), I do wonder if this is really an appropriate forum for such comments.

    If there’s one thing to be disappointed about with Iran’s successful satellite launch, it’s that it serves as another reminder that in the peaceful exploration of space, Australia has yet again been left behind when we could have been launching our own satellites (and astronauts) for decades.

  32. StevoR

    @ Sundance : true & yes I know its all off-topic too. Fair call.

    Its just I know there are so many nutters that will instantly respond to that story with this Islamophobic “Oh No! Shock! Horror! The big bad Iranians have good rockets now! Gasp! Horror!” type attitude & I just wanted to forstall it. I want sanity to prevail not anti-Iranian hysteria. Call it a pre-emptive attack if you like! ;-)

    Yes, I’m from South Australia too. :-)

  33. Bein'Silly

    Hey! If anyone’s really worried about Iranians in space, well don’t worry, I’ve got a cunning plan – let’s just offer to co-operate with the Iranian space agency and then rope them into the International Space Station project! That should keep ‘em busy and distracted for a good long while and ensure no further progress is made! ;-)

    PS. My suggested name for the ISS, when /if they ever get round to giving ita proper name = Horton. Y’know as in the white elephant! ;-)

    Cruel I know but .. durrnit we should be on Mars by now not still
    playing around with some supersized ‘Skylab’. :-(

  34. Bein'Silly

    Excellent news BA btw. We keep whittling the latest exoplanet finds down don’t we?

    Wonder if we’ll ever get down to dwarf exoplanets? ;-)

  35. Naomi

    IVAN3MAN, on the graph you posted, there are two spikes on either side, roughly equal in distance from the planet’s transit. They’re at (roughly) the -2 and 2 hour marks, and there’s a fair gap above the red line. Would that be anything significant, or just a coincidental blip?

  36. Sorry everyone — I goofed big time on the size. Phil, being truly awesome as he is, is right of course.

    I made the slip because of the lets-minimize-the-size-of-this-planet-as-much-as-possible language in the ESA press release (http://www.esa.int/esaSC/SEM7G6XPXPF_index_0.html).

    *still slapping forehead*

  37. Jason

    @Asimov Fan: The Wikipedia URL has parens in it: http://en.wikipedia.org/wiki/Omid_(satellite)

  38. Jason

    …and thanks to some brain-dead link parsing what I put up isn’t clickable. Copy and paste if you want to follow the link.

  39. Joe Meils

    What a fun time to be alive! It seems the discoveries are coming in a flood, amazing us all daily with the wonders of the universe.

    Should we start a betting pool on when the first “Type M” (as Star Trek always put it) planet will be found? I’ll put my dollar on the October of this year square.

  40. Gary Ansorge

    Yeah, yeah, Iran, (Bad Wolf!or some such nonsense).

    Now, back to small exoPlanets,,,

    I wonder how long a satellite in the L2 position could remain sequestered from the stars radiation. A small sat, say 1/2 earth size, might even be able to maintain a liquid H2O environment from re-radiation of heat from the main planet. Interesting story idea there.
    Guess we would need the mass data before we could calculate the L2 distance. Too close and it’s always in the penumbra,,,too far and it would receive too much stellar radiation spillage around the main object.

    Gary 7

  41. Trebuchet

    I’m really impressed by the graph posted by Ivan3Man — the light apparently falls off by only a factor of .00035 — and we can detect that! Awesome.

    I’m also curious how they can tell the variation is due to a planet and not something like a major sunspot on the rotating star. I expect they’ve got it figured out, I just wonder how.

  42. Raven

    StevoR: I’m not worried about Iran inparticularly, but Islam in general certainly worries me. I’ve read enough of the Qur’an to know that Muslims are specifically told to go out and forcibly convert all non-Muslims (well, technically there are no non-Muslims, since everyone is born Muslim, and just doesn’t know it yet:P). Anyone who can’t be converted is an Enemy of Allah, and must be, as the Daleks would state, exterminated.

    As far as any given *true* Muslim is concerned, there should only be 1 question: are you a moderate, liberal Muslim who believes that non-believers should be passively and peacefully converted over long periods of time, or are you a conservative Muslim who believes that non-believers should be conquered, forcibly converted, or killed?

    Anyone who believes otherwise isn’t a real Muslim, and has no place calling themselves a Muslim, since they obviously aren’t following Allah’s will, as stated in the Holy Texts:P.

    In short, I see no alternative but an eventual war. Why? Because peacefully or through war, *I* will not convert to Islam, ever. I’m an atheist, and I’d rather see the world burn than fall before that corrupt, evil religion. As the Jem’hdar would say, “Victory is Life”.

  43. Quiet Desperation

    Iran is not the cardboard cartoon villian all too many people in America & the wider “Western” world seem to think it is

    A country can’t be a villain, but it’s leaders can. When Mahmoud “We have no gay people” Ahmadinejad insists on doing his best Snidely Whiplash impression on a daily basis, what am I to think?

    it is a complex, rich and diverse country withalongerand deeper historyof civilisation than the USA’s and most other nations globally.

    So what happened? Senility, perhaps?

    I, for one, am looking forward to the day Iran when does get a reasonable
    nuclear deterent against American and Israeli attack.

    And you can see no room for debate on the practicalities of major theocracies (especially ones with a tradition of martyrdom) having nuclear weapons? No room for debate whatsoever in your mind? That’s not hysteria. It’s an honest question asked by many people with several orders of magnitude more geopolitical experience than you or me combined.

  44. gss_000

    @Vagueofgodalming

    That mass is just an estimate. It’s not official nor can it be 100% relied upon until it is confirmed.

    BTW, did you hear this, from New Scientist (http://tinyurl.com/cf2zot) on Monday:

    “THE first direct image of three extrasolar planets orbiting their host star was hailed as a milestone when it was unveiled late last year. Now it turns out that the Hubble Space Telescope had captured an image of one of them 10 years ago, but astronomers failed to spot it. This raises hope that more planets lie buried in Hubble’s vast archive.”

    This is why all Hubble data, even if it seems inconsequential like an image of a publically chosen object, could be very valuable later.

  45. Dave Mosher, actually Casey10s caught it!

  46. IVAN3MAN

    Naomi:

    IVAN3MAN, on the graph you posted, there are two spikes on either side, roughly equal in distance from the planet’s transit. They’re at (roughly) the -2 and 2 hour marks, and there’s a fair gap above the red line. Would that be anything significant, or just a coincidental blip?

    That’s very observant of you! :-) The article at the Observatoire de Paris web-site (click on the image) does not give any further information on the minor peaks and troughs in the light curve of CoRoT-Exo-7b parent star.

    In my opinion (I’m making an educated guess here!), if the detectors on COROT are sensitive enough to detect a dip of approximately ±1% in the observed brightness of the star in question, then they could just be sensitive enough to detect solar flare outbursts from the star, which would probably show up as a ‘blip’ in the light curve. However, it might just be random electronic noise from the detectors themselves.

    Dr. Phil Plait, what’s your opinion on this?

  47. 20 hours for an orbit? Even the slightest deviation from a circular orbit would drive ferocious tidal heating that would make Io look inert.

  48. Mark

    Can I ask a stupid question?

    The transit method only works in cases where our line of sight to the star passes along its orbital plane.

    Given the number of stars that are close enough to observe an exoplanet, shouldn’t the number of stars where this is possible be small? Like, really really small? Or am I missing an order of magnitude here? (The probability is really small, but the number of stars is large).

    Does this imply that;
    1) Almost all stars have planets?
    2) Almost all stars have orbital planes lined up due to some “rule”?

    Do I have a good reason to be confused here? *giggles*

  49. I see andy from the HD80606 b thread is here. You are an exoplanet researcher, are you not? Perhaps you can answer this question for me. Is it true that the only exoplanets that can have their diameters measured are the ones that transit their star? And I would assume the diameter is based on how long it takes for the light curve to dip once the planet reaches the limb of the star?

    Haven’t some exoplanets had both their diameter and mass measured, and thus their density measured? I seem to recall some news about a so called “balsa wood” exoplanet with a density of about 0.2 grams per cubic centimeter. TrES-4 I believe it was called. Was it a transiting planet too?

    http://www.lowell.edu/media/releases.php?release=20070806

  50. @Ken_g6 “I believe we’ve found the masses of Jupiter-mass planets at >1au from their stars. So since Jupiter is ~300 Earth masses, and gravity decreases with the inverse square of distance, any Earth-massed planet within 0.05au of its star should be detectable.”

    I believe Doppler detectability is based on the velocity of the star orbiting the barycenter. If I’ve done the math correctly I believe it should be proportional to:

    Mp / sqrt(r * Ms)

    Mp is mass of planet
    r is distance of planet from star
    Ms is mass of star

    So, that explains why massive planets (high Mp) in close to their star (low r) were the first to be discovered (e.g., 51 Pegasi b). Assuming you can detect an exoplanet with 1 Jovian mass at 5 AU orbiting a 1 solar mass star, you should be able to detect an exoplanet with 1 Earth mass at 5.0E-5 AU orbiting a 1 solar mass star. That’s inside the body of the star so that’s telling us that detection of Earth-like planets is still not possible without lower detection thresholds for the Doppler shift.

    Of course, this doesn’t apply to the transit method, only the Doppler spectral method. Interestingly enough, it’s also telling us that low mass stars (e.g., red dwarfs) have a better detectibility than more massive stars. So for a 0.1 solar mass red dwarf it is 3 times easier to detect exoplanets than for a 1 solar mass star. That might explain why some of the lowest mass exoplanets discovered to date have been found around red dwarfs (e.g., Gliese 876 d).

  51. Gopher65

    Mark:

    Assuming that the planetary orbits are randomly aligned (which I think is the case), yes the number should be pretty small. Not vanishingly small, but pretty small.

  52. IVAN3MAN

    Mark:

    Can I ask a stupid question? The transit method only works in cases where our line of sight to the star passes along its orbital plane.
    Given the number of stars that are close enough to observe an exoplanet, shouldn’t the number of stars where this is possible be small? Like, really really small? Or am I missing an order of magnitude here? (The probability is really small, but the number of stars is large).
    Does this imply that; 1) Almost all stars have planets? 2) Almost all stars have orbital planes lined up due to some “rule”?
    Do I have a good reason to be confused here?

    No, Mark, it’s not “a stupid question”.

    According to Wikipedia, the probability of a planetary orbital plane being directly on the line-of-sight to a star is the ratio of the diameter of the star to the diameter of the orbit. About 10% of planets with small orbits have such alignment, and the fraction decreases for planets with larger orbits. For a planet orbiting a sun-sized star at 1 AU, the probability of a random alignment producing a transit is 0.47%. However, by scanning large areas of the sky containing thousands or even hundreds of thousands of stars at once, transit surveys can in principle find extrasolar planets at a rate that could potentially exceed that of the radial-velocity method, although it would not answer the question of whether any particular star is host to planets.

  53. I welcome our very hot exo-planet overlords!

  54. @Bein’silly:
    I believe the Commander of Expedition One unofficially christened the ISS Space Station Alpha. I’ll check on that, though.

  55. @Bein’silly:
    The ISS website has details of every expedition. Interestingly enough, Expedition One was the only mission to have detailed mission logs recorded by the commander. It is the only expedition that I could find that used the name ‘Alpha’. This was the radio call sign used to identify the ISS, so I’m not sure if that moniker is still used. I do know that then NASA administrator was not in favor of naming the ISS ‘Alpha’ for fear of ticking the Russians off. Interestingly, when they crew was given the go-ahead, the Russian Mission Control erupted in cheers.

  56. Sorry for getting off topic Phil, but he asked! :) :)

  57. I see andy from the HD80606 b thread is here. You are an exoplanet researcher, are you not?

    Heh, I wish I were. Probably would have been if I hadn’t burned out on academia in my final year as an undergrad, but I still maintain an interest in the subject.

    Is it true that the only exoplanets that can have their diameters measured are the ones that transit their star? And I would assume the diameter is based on how long it takes for the light curve to dip once the planet reaches the limb of the star?

    IIRC the way to determine the radius is to determine how much the star’s light is dimmed during transit – bigger planets obstruct more of the star’s light. Problem with using the time it takes the light curve to dip is stellar limb darkening.

    It’s also possible to get radii for directly-observed planets (like the ones orbiting HR 8799), but this relies more on theoretical models than the transit measurements do.

  58. StevoR

    Tom Marking Says:
    February 4th, 2009 at 2:00 pm

    … Haven’t some exoplanets had both their diameter and mass measured, and thus their density measured? I seem to recall some news about a so called “balsa wood” exoplanet with a density of about 0.2 grams per cubic centimeter. TrES-4 I believe it was called. Was it a transiting planet too?

    My info on this (I’m keeping my own exoplanets liszt for reference!) :

    TrES-4 The “Balsawood planet” : Discovered October 2007. This Hot Jupiter is the record-holder for largest diameter being 70 % larger than Jupiter’s radius but with a density of just 0.2 grams per cubic centimeter making its density equivalent to balsawood and thus less dense than Saturn. If there was an ocean big enough to float this planet –like Saturn would do so. It would also sizzle being around, 1,330 degrees Celsius (1,600 Kelvin) from orbiting its star in 3 And half days. It was discovered through transiting and directly measured by a team from the Lowell Observatory as part of the Trans-Atlantic Exoplanet Survey (hence TrES) and presents a problem for the theorists being much larger than current models can explain. The Balsawood planet is 1,400 light years distant.

    Hope that helps and isn’t too late!

  59. StevoR-Correctin'

    D’oh!

    That’s three & a half days -small ‘a’ naturally NOT star in “3 And half days” whatever they are? 3 half And-romedan days maybe? ;-)

    Editing BA, please!
    Pasted from word & there’s still typos. How annoying. Sigh. :-(

  60. StevoR-Correctin'

    Well from the smallest exoplanet to the largest and now back to Iran because Quiet Desperation and Raven need answering :

    No post on Omid yet from the BA? :-( Seems not. Pity I’d like to see his views on it and have an on-topic spot to discuss it too ..

    @ Raven saying :
    February 4th, 2009 at 9:07 am

    “StevoR: I’m not worried about Iran in particular, but Islam in general certainly worries me. I’ve read enough of the Qur’an to know that Muslims are specifically told to go out and forcibly convert all non-Muslims … Anyone who can’t be converted is an Enemy of Allah, and must be, as the Daleks would state, exterminated.’

    Nonsense! That’s exactly the sort of Islamophobic cartoon villain simplistic misunderstanding I feared we’d get.

    Its also totally wrong. In doctrinal terms – respecting the “people of book” (Jews & Christians) and treating all people as equal before God Islam is actually the most egalitarian and tolerant of all the big three monotheisms.

    You can’t have read much of the Qu’ran or had some very bad & biased teachers of it to come to your mis-understanding about what Islam means. Do you have any Muslim friends? Have you studied or read more widely about it and its history? I suggest you invest in doing so & learn what you’re talking about before spouting ignorant Islamophobic tripe like that.

    Raven : “As the Jem’hdar would say, “Victory is Life”.

    Lets see now : Real, complex, multi-faceted global civilisations of Muslims and Islam

    Versus

    Fictional Star Trek alien baddies.

    Big difference there! Can’t you spot it? ;-)

    Oh & for the record I’m an atheist with a long-standing interest in the South-West Asian (“Islamic world”) region who has studied this area for many years and sucecssfully completed an Honours thesis on the Palestinean issue.

    QuietDesperation :

    “A country can’t be a villain, but it’s leaders can. When Mahmoud Ahmadinejad insists on doing his best Snidely Whiplash impression on a daily basis, what am I to think?”

    About the same as when Dubya Bush tells the world that God told him to invade Iraq. :-(

    Actually, Ahmadinejhad is a lot saner and more legitimate a president than Bush, George II the lesser ever was. Okay he uses a bit of OTT rhetoric which is part of that cultural style – Muslim poetry tends to hyperbole and poetic exaggeration – like a lot of other political oratory round the world ..

    But then you need to look at the actions & their context – how many nations has Iran invaded lately? None! Not a one since before World War I – during which incidentally, the Arabs fought on the Allied side only to be betrayed by the Zionist lobby.

    How many times has the USA and Israel attacked and threatened to wipe out other nations – ones that pose them far less threat than Iran faces from its foes? Lots! Gaza, Lebanon, Palestine, Iraq, Syria, Egypt, Afghanistan, Vietnam, Cuba, Panama, the list is long and blood-stained….

    Iran lacks WMDs, Israel has them -in violation of UN laws.
    Iran obeys international law. Israel & the US flout it.

    Iran has US troops and a number of US proxies on its immediate borders – & a bellicose nuclear-armed Russia to its North as well.

    So you can hardly blame Iran for wanting to be able to defend themselves against the real, clear and present dangers to them.

    Look up the CIA role in the Shah’s regime – that might give you some inkling why they see the US as the “Great Satan.” They *don’t* hate us because we’re supposedly so free and democratic (both arguable claims btw.) they hate us because we threaten them and have done tonnes of really nasty stuff to them in the past. :-(

    Try and see the other side of the story for once QD.
    Just try I dare you! ;-)

    QD : “And you can see no room for debate on the practicalities of major theocracies (especially ones with a tradition of martyrdom) having nuclear weapons? No room for debate whatsoever in your mind? That’s not hysteria. It’s an honest question asked by many people with several orders of magnitude more geopolitical experience than you or me combined.”

    I do know what I’m talking about in this area – you’ve made it very clear that you don’t! :-P

    Ideally there’d be NO nuclear weapons – or all the WMDs would be in UN hands with NO single nation given the power to destroy any others. I’ve been to Hiroshima. I know what even the first most primitive A-bombs can do. I grew under the threat of nuclear extinction in the Cold War.

    I’ve concluded that perhaps the nation *least* trustworthy with regard to having WMDs is the USA. After all it has been responsible for more attacks and aggression against other nations that really are “peace-loving” rather than war-mongers who spew pro-Peace rhetoric as they invade, occupy and terrorise with “shock & awe” bombing campaigns. :-(

    If ever a nation needed to swear off using aggression against other nations and limit itself very strictly to a small military restricted to genuine self-defence only – as they forced the Japanese to do post WWII – that nation is the USA.

    Plus if everyone has WMD’s then everyone is equal and has a deterrent – USA vs USSR, India Vs Pakistan and everyone knowing just how bad nukes are is evidence that Mutually Assured Destruction – nasty, ugly and frightening as it is, works.

    I hope one day NO nation alone has WMDs – that they are banned and this ban enforced by a genuine global government.

    Until that time, Iran having a real deterrent against US or Israeli attack is about the last, best hope for peace.

    I know this is off-topic – but some points were raised by others that just *had* to be answered. :-(

  61. Joker

    @StevoR: Here’s hoping reincarnation is real – & you are born in your next life as a left-handed lesbian Jew in a Muslim country! ;-)

  62. Dov Henis

    What Makes A Planet An Earth Counterpart

    A. “Smallest exoplanet yet is found”
    http://www.sciencenews.org/view/generic/id/43038/title/Smallest_exoplanet_yet_is_found
    Finding a planet just under twice Earth’s size puts astronomers closer to discovering an Earth counterpart.

    B. What is “an Earth counterpart”?

    An “Earth counterpart” may be either a still “pre-lifed” or an already “bio-sphered” planet.

    The features that would render a pre-lifed planet a pre-lifed Earth counterpart would include the environmental and compositional parameters of the 4.6 BYA Earth.

    The features that would render a bio-sphered planet a bio-sphered Earth counterpart would include a bio-sphere comprising the Planet’s primal organisms, its genes, and the chemical constituents of their evolved organisms, where:

    Organism = a self-replicable temporary constrained-energy genetic system that supports and maintains a planet’s biosphere by maintenance of its genes.

    Dov Henis
    (comments from the 22nd century)
    “Life’s Manifest”
    http://www.the-scientist.com/community/posts/list/112.page#578

  63. Amalekite

    @ 43 Raven :

    I’d rather see the world burn than fall before that corrupt, evil religion. As the Jem’hdar would say, “Victory is Life”.

    Being Islamophobic, racist and stereotyping much there Raven? :roll:

  64. Quaunta

    IF solar energy is usful in space could there be away to send to the sun a huge vaucum device to suck up plasma and then use it to push itself back to earth and as a fueling station for furute space flights from our near earth orbit?

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