Binary black holes and a potential Earth-like planet

By Phil Plait | August 31, 2011 1:52 pm

Two stories just came out that I would love to spend time writing up in full, but I’m trying to get a million things done before I leave for Dragon*Con in the morning, so I’ll be brief:

1) Astronomers using the Chandra X-ray Observatory have discovered a binary black hole: two ginormous beasts orbiting each other about 500 light years apart in the center of the gorgeous spiral galaxy NGC 3393. Each has a mass of at least one million times that of the Sun. While binary black holes in the centers of galaxies have been spotted before, this is the closest one found: a "mere" 160 million light years away!

2) A newly-discovered planet (PDF) orbiting a star just 36 light years away appears to be at just the right distance to potentially have liquid water on its surface. The planet, HD85512b, orbits a star somewhat smaller and cooler than the Sun, but close enough to it that it actually gets more heat on average than Earth does. The planet is hefty, 3.6 times the mass of the Earth, but the size is not known (you get that from transit data, which we don’t have, and it would give us an idea of the surface gravity). So we don’t know anything about it, really, but if conditions are just so, it has the best potential we know yet for a planet with liquid water. Nat Geo has a great writeup of all this.

Now, if the Universe would kindly oblige not doing anything interesting for a few more hours, I can finish packing!

CATEGORIZED UNDER: Astronomy, Cool stuff

Comments (38)

  1. Some may be dismayed that a potential Earth-like planet doesn’t get top billing. But I find it quite encouraging. When finding new Earths gets boring it’ll only be because we’ll have found so many already!

  2. Chris

    Actually there is a lot more to consider besides just being the right distance. Is the CO2 the right abundance? Plate tectonics. We happen to be lucky that the weathering and CO2 emitting volcanoes keep things pretty steady over time. (Till we messed it up. ) But a world which is bigger might have more geologic activity, pumping out more CO2 than weathering could put up with and you could get a natural runaway greenhouse effect.

    Also the planet is around a K5V star with a period of only 58 days. It’s probably tidally locked. So actually there might be pockets where a nice habitability zone could exist on the surface.

  3. riverlaw

    Slow down there, Chris :) They were not talking about finding life in this article.

  4. Chris

    That could be Ferenginar. With 50% cloud cover it’d rain a lot, and being more massive than the Earth would explain why the Ferengi are so short. High gravity.

  5. Keith Bowden

    I doubt that another world has to be exactly like Earth in order to have life on it – we evolved here in this way because these are the conditions we have. It’s the essence of evolution that we have adapted to our surroundings, so the “right” balance of CO2 is potentially… whatever it is. :)

    I know there are theoretical models for the event, but are we aware of any black holes currently (or even recently) in the process of eating each other? I know they have and that they spin faster after the merger. It would be cool to “see” it in action though, like the recent black hole eating a star.

  6. terryp

    that x-ray close-up looks to me like a pegasus. anyone else see it, or am i just insane?

  7. andy

    HD 85512b is only marginally less irradiated than Venus, I’d guess it’s probably also gone runaway greenhouse. Sure if you construct some magic atmosphere that has more clouds than Earth but without an enhanced greenhouse effect you can get it to be habitable, but show me a physically-plausible atmospheric mixture that will do this. (Let’s just bear in mind here that Venus with an Earthlike greenhouse effect but the same 100% cloud cover would actually be a colder planet than Earth – the reflective clouds more than compensate for it being closer to the Sun. Venus is an energy-efficient hellworld.)

    But hey that’s better than the original claims for Gliese 581c, which is substantially more irradiated than Venus…

  8. VinceRN

    Seem that the definition of “earth-like planet” has gotten pretty loose. Is anything that might have liquid water really “earth-like”? Shouldn’t earth-like mean something that we earth critter might theoretically be able to walk around on, something that is in some significant way like earth?

    Not that this new planet discover means any less, it is incredible that we can find these and our ability to find smaller ones in increasing rapidly. One day we will find something that is a little like earth, right star, right distance, right orbit, right radiation, etc…

    It wont be long before we have maps of dozens, or hundreds of nearby solar systems and know about real earth like worlds. Then physics will be standing there laughing at our frustration over not being able to get to them!

  9. Lascas

    Agree with VinceRN.

    Earth-Like seems to have lost its meaning.

  10. Chris

    @terryp
    Nope, you’re insane :-P

  11. 4zero4

    @vinceRN: Considering the variations in planets, such as the plethora of gas giants, any planet that has liquid water really is quite close to earth. By my understanding of things, that is the single biggest requirement for life. Just because there are some differences doesn’t mean it’s not “earth like.” It just isn’t a perfect match, as far as we know.

  12. frankenstein monster

    This world is yet another super-venus. more solar heating+thicker atmosphere = runaway greenhouse effect. Even the Earth itself is near the inner edge of the habitable zone. So, I am deeply skeptical about habitability of any world with more insolation AND more mass…

  13. Ken

    a binary black hole: two ginormous beasts orbiting each other about 500 light years…

    Moment of incredible tension…

    apart

    Whew. Not “away”.

  14. Matt

    Low density could make this planet inviting (e.g., Jack Vance _Big Planet_). But I’m not going to get my panties in a bunch until spectral analysis detect free oxygen on one of these earth-like planets.

  15. mike burkhart

    I’ve heard of binary stars but this is the frist binary black holes I’ve heard of .I have also been thinking about the bigest mysteries for astronomers to solve:1Dark Mater2Is there Life out there?3Dark Energy4Other Universe5Posiable Other Planets in Our Solar System6Number of Planets orbiting other stars7Amount of Antimater in this Universe8Other dimetions then 4.And still the universe might have some new unkown objects we may discover,just like Quasars when discovered in the 60s they were a complete surpise.

  16. David

    @frankenstein monster: thicker atmosphere? The article says all they know is the distance from it’s star, and mass. Actually, it specifically says they don’t know anything else about it (other than it’s nearly circular orbit). The problem is, the planet doesn’t transit it’s star from our POV, which is needs to do for us to determine it’s size and the composition of it’s atmosphere.

  17. Messier Tidy Upper

    Wonderful news – always great to hear such exoplanetary finds although it may well be more SuperVenus than Super-Earth and is still thrice Erath’s mass.

    The binary Black Hole find is a great one too. :-)

    @1. Arik Rice :

    Some may be dismayed that a potential Earth-like planet doesn’t get top billing. But I find it quite encouraging. When finding new Earths gets boring it’ll only be because we’ll have found so many already!

    Except we haven’t – but many people seem to be under the false impressionwe have. We have a couple of good candidates for plausibly earthlike planet at best. Gliese 581 g – if it exists, perhaps Gl 581 d although its probably too massive and more an exo-Neptune type world if memory serves and now this one if it isn’t too hot and Cytherean* in nature.

    Mind you, Kepler (maybe CoROT too?) seems likely to come up with a lot more and hopefully better exo-Earth candidates soon. I can’t wait. :-)

    —-

    * Ie. “Venusean” along same lines as Mars being Areological and our Moon Selenological. Rarely used adjective but I like it. :-)

  18. Messier Tidy Upper

    See :

    http://en.wikipedia.org/wiki/Gliese_581_g

    for the wikibasics on Gliese 581 g & see also :

    http://en.wikipedia.org/wiki/Super-Earth

    &

    http://news.sciencemag.org/sciencenow/2008/06/02-01.html

    for the lowest mass non-pulsar planet yet found. :-)

  19. amphiox

    That could be Ferenginar. With 50% cloud cover it’d rain a lot, and being more massive than the Earth would explain why the Ferengi are so short. High gravity.

    Earth has on average 60% cloud cover. So 50% is actually less cloud cover than earth and presumably less rain!

    Sure if you construct some magic atmosphere that has more clouds than Earth

    Except that, as above, earth has 60% cloud cover and 50% is LESS than 60%. Also, the models are saying at least 50%, so more is also ok. The thickness of the atmosphere probably matters here.

    Seem that the definition of “earth-like planet” has gotten pretty loose

    The definition hasn’t changed (yet). It’s just that people (understandably) who aren’t experts in the field tend to read too much into the label.

    Scientifically “earth-like” means “it looks similar to us observing it here as earth would look to us observing it the same way if we were there looking here”. Since atmosphere isn’t something we can observe at present, it doesn’t actually enter into the scientific definition of “earth-like”. The most earth-like planet known in the universe is actually Venus.

    Obviously the things we can’t yet observe are very important, but until we actually can observe them, they are in the realm of science fiction speculation and not actual science. When we do develop the capacity for observing these things, the scientific definition of “earth-like ” will change. That’s how science works.

    Right now, though “earth-like” doesn’t mean “habitable”. It means “potentially habitable”, and thus it actually includes “Venus-like” and “Mars-like”, and “Super Earth/Venus/Mars-like”. Venus was “potentially habitable” – it could have been habitable if the right circumstances had occurred, at least at some point in its history. We know that those circumstances did not occur and Venus has not, at least right now, fulfilled that potential. Indeed, earth will probably go the same way at some point in the future as solar luminosity increases

  20. amphiox

    Note that the formation process of Earth and Venus is so similar that if Venus-like planets are common, Earth-like planets must be common too, and vice versa. Finding even a Super-Venus only 36 light years away is quite exciting and suggestive.

  21. Joseph

    Class M or it didn’t happen!

  22. Messier Tidy Upper

    @ 15. mike burkhart : Really? :-o

    I guess you must have missed seeing this :

    http://blogs.discovermagazine.com/badastronomy/2011/08/29/virgos-have-beautiful-eyes/#comment-411563

    recent comment then! ;-)

    Comment #15 in the ‘Virgos have beautiful eyes’ thread if the link fails.

    Hope you enjoy it and its links. :-)

  23. andy

    Except that, as above, earth has 60% cloud cover and 50% is LESS than 60%. Also, the models are saying at least 50%, so more is also ok. The thickness of the atmosphere probably matters here.

    Except that the 60% figure does not appear to be what they are using in their toy models – I’d guess that 60% figure includes clouds over the nightside and clouds that involve various levels of transparency, which probably get represented as constituting less cloud coverage in their 1D toy model. It is clear from the paper that they are requiring the planet to have a higher albedo (i.e. greater cloud coverage) than the Earth (albedo 0.3): for the nominal eccentricity of 0.11 the albedo must be higher than 0.52, if the orbit is circular the limit drops to 0.48.

  24. I wonder if it’ll be close enough to show up on the upgraded LIGO when that gets running.

  25. Don´t Panic

    Hmmm…. nothing intresting.
    Sorry, but I just read about star SDSS J102915+172927 and according to german rechearcher Elisabetta Caffau it only consists out hydrogen en helium. No metals.
    And that supposedly makes it a star that shouldn´t excist.
    Anyways, enjoy your Dragon*Con.

  26. Tom

    Is anyone aware of any studies about what the weather would be like on a tidally-locked planet? I have often seen write-ups speculating that a swath of territory along the longitudinal lines perpendicular to the star (i.e. the equivalent of a perpetual late-afternoon/twilight on earth) could be habitable. However, it seems to me that there would be howling winds from superheated air rising on the one side and the super-cold air rushing across from the cold side to fill the gap. Just wondering if there are any models that say it might actually be a stable environment.

  27. Turing E

    I may be wrong (Phil, please comment if I am!), but I recall from my chaotic dynamics courses that binary black holes are necessarily a chaotic system with no stable equilibrium points, which means that they are destined to be fairly short lived as they will eventually (and probably sooner rather than later) collide or fling themselves away from each other. If so, then we are pretty lucky to be seeing these guys together. I’m not sure of the precise timescale at which such a chaotic system will cause them to collapse (only that it is “short”, which in cosmological timescales can still be fairly large), but it’d be cool if we could catch something spectacular like a black hole collision happening.

  28. Now, if the Universe would kindly oblige not doing anything interesting for a few more hours, I can finish packing!

    A few more hours?! Jeebus, you crammin’ the kitchen sink in your bags? Leave some room for swag.

  29. Chris A.

    There was, back in the early 90s, speculation that the two major components of M31’s core (P1 and P2) each harbored black holes. But apparently P1’s stars aren’t centrally condensed enough to support that model.

  30. SkyGazer

    Is this interesting enough?

    “Dark Matter Is an Illusion, New Antigravity Theory Says”

    news.nationalgeographic.com/news/2011/08/110831-dark-matter-proof-gravity-quantum-theory-cern-space-science/

  31. Bryan Elliott

    Fun thought experiment:

    Take a binary black hole, and solve for a tragectory that brings you to a halt at the midpoint between them. If they are orbiting far enough away from each other, you won’t be torn in half by twin tidal forces, and can survive indefinitely. If they’re close enough together, time dilation at the equilibrium location could bring the end of the universe into a livable span.

    The key question: can such a sweet spot exist? Can you live out your days watching the universe end? If so, what are the masses of the black holes, and the distance between them?

  32. @ Bryan Elliott:

    More importantly, what would it take to construct a restaurant at such a spot?

  33. Sili

    Each has a mass of at least one million times that of the Sun. While binary black holes in the centers of galaxies have been spotted before, this is the closest one found: a “mere” 160 million light years away!

    How much bigger does LIGO need to get to pick up gravity waves from them?

  34. Chris

    > How much bigger does LIGO need to get to pick up gravity waves from them?

    Good question. Here’s another: How big will the gravity waves get as those black holes spiral towards one another and finally merge? And how badly will that galaxy be disrupted by gravity waves when that happens?

    BTW, this will be “our” fate once the Andromeda and Milky Way Galaxies merge in about 4 billion years.

  35. Ryeguy

    Shouldn’t we be able to detect gravitational wave distortion (if it exists) by some lensing effect?

  36. amphiox

    An interesting point to consider with this planet is it’s age – over a billion years older than Earth. This means that it’s had several billions of years in the past when its star was younger and less luminous than it is today, so that even if it receives more solar heating than earth does today, it may not have in the past, and may have had a very long time receiving solar heating close to what Earth has experienced in our own history. It would be interesting to look at the models of earth’s future evolution, figure out the point when we think Earth flips over to Venus-like conditions, and compare Earth just before that point with this planet as it is now.

    Another thing to consider with respect to calling this planet “earth-like” is that the term is relative. At 3.6 earth masses there are only a very few currently known less massive exoplanets, and it is certainly smaller than all the other exoplanets in or even near their star’s habitable zones. And a degree of solar heating greater than earth but less than Venus is also closer to Earth than any other known exoplanet. So even if this planet turns out to be a super-Venus, it is still the most earth-like planet currently known, and is the very first exoplanet that can arguably be described as even more earth-like than either Venus or Mars.

    A third interesting point to consider, is that we believe that Venus went through a phase in its early history when it had pretty earth-like conditions, prior to the runaway greenhouse kicking in. This phase was, of course, quite short, and probably ended well before the planet was even a billion years old. But we now also believe that at some point in the future, earth will become like Venus, with a runaway greenhouse. In other words, just like Venus, Earth will have an early “Earth-like” phase, followed by a late “Venus-like” phase, with the only difference being that Earth’s “Earth-like” phase will last much longer.

    Therefore, it is within the realm of possibility that”Earth-like” and “Venus-like” exoplanets do not constitute two separate classes of planets, but separate stages in the evolutionary history of the same class of planet. In other words, many “earth-like” exoplanets will have both an “earth-like” and a “Venus-like” phase over the course of its lifespan, and the big question will be how long each of these phases last and at what point in time the flip-over occurs.

  37. Messier Tidy Upper

    @ ^36. amphiox :

    Therefore, it is within the realm of possibility that”Earth-like” and “Venus-like” exoplanets do not constitute two separate classes of planets, but separate stages in the evolutionary history of the same class of planet. In other words, many “earth-like” exoplanets will have both an “earth-like” and a “Venus-like” phase over the course of its lifespan, and the big question will be how long each of these phases last and at what point in time the flip-over occurs.

    Very good point and agreed. :-)

    There’s also the idea that our planet went through several “Snowball Earth” phases when it was totally ice covered and thus a very different sort of world for some millennia as well.

    Two stories just came out that I would love to spend time writing up in full, but I’m trying to get a million things done before I leave for Dragon*Con in the morning, so I’ll be brief.

    Fair enough BA, but I’d love it if you wrote these up in full with more details and considered opinion on them later if I may put in the request. :-)

  38. andy

    An interesting point to consider with this planet is it’s age – over a billion years older than Earth. This means that it’s had several billions of years in the past when its star was younger and less luminous than it is today, so that even if it receives more solar heating than earth does today, it may not have in the past, and may have had a very long time receiving solar heating close to what Earth has experienced in our own history.

    On the other hand the star is less massive than the Sun and therefore evolves at a slower rate, so the luminosity increase may not be all that much.

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