A thousand oceans of water surrounds a nearby star

By Phil Plait | October 24, 2011 7:00 am

There’s cold water vapor orbiting the star TW Hydrae… and a lot of it. Enough to fill the Earth’s oceans thousands of times over!

TW Hydrae is a star located pretty close by, about 175 light years away. It’s lower mass than the Sun, so it glows an orange-red, but it’s also very young, less than 10 million years old. Stars that age are still shaking off the remnants of their formation, and that’s just the time you expect planets to get started.

And in fact it’s been known for years that TW Hydrae is surrounded by a giant disk, the leftover materials from its formation. Disks like that around other stars have been closely scrutinized, and we see lots of different materials in these disks, including various minerals, complex dust molecules, and even water. In general the water that’s been found is usually close in to the star and warm (which makes it easier to see).

Astronomers used the orbiting Herschel telescope to look at the disk of the star TW Hydrae in the infrared, and found water in the spectrum of the material there. And what they discovered is that it’s cold vapor, not warm. That’s the first time this has even been seen, and it’s kinda neat how this was done.


When you break light up into individual colors, you can learn a lot about the object emitting that light, including what it’s made of and what temperature it is. Water emits light at a lot of specific colors in the IR, but there’s one in particular that reveals its temperature. That’s the one the astronomers used to see the water around TW Hydrae.

Water is made up of one oxygen atom and two hydrogen atoms: H2O. Each hydrogen atom has a proton in it, and protons have a property scientists call spin. They can spin either one way or another; scientists call this spin up or spin down. This is important because the total amount of energy in a water molecule is different if the two hydrogen atoms spin the same way (say, both up) versus different ways (one up and the other down). The first case is called ortho, and the second para. Each emits a slightly different wavelength of light, which can be measured if you’re careful. And have Herschel at your service.

In room temperature water, you get three times as many ortho water molecules as para, but as the temperature drops that ratio gets closer to 1. When they looked at TW Hydrae, the ratio was low enough to know that the water was cold, and must be coming from farther out in the disk than is usually seen.

Not only that, but the strength of the line (how tall the feature in the spectrum is) tells you how much water is there. The amount they found? Enough to fill "thousands of Earth oceans" according to Michiel Hogerheijde, who led the team that made the discovery.

That’s pretty cool. It means that a lot of water is available to make planets when they form.

The thing is, we kinda knew this already: there’s a lot of water in our solar system. It’s not just Earth: moons in the outer solar system (like Europa and Enceladus) are almost entirely made of water, and it’s prevalent in the comet-like iceballs in the outer solar system called Kuiper Belt Objects, too. But our solar system is only one example of how stars and planets are formed. We still don’t know how typical our solar system is. We do know that making planets is easy, so easy that nearly half the stars in the sky may have them. But we still haven’t spotted another Earth-like planet, and even if we do, will it have water?

We still don’t know, but the odds of it being wet look better every day.

And I can’t leave this without noting that in this case, nature is imitating art: the TW Hydrae got its name for being in the constellation of Hydra, the water serpent… a beast that needs to live in water to survive! Coincidence, of course, but a funny one.

Disk art credit: NASA/JPL-Caltech. Plot: ESA/NASA/JPL-Caltech/Leiden Observatory


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- More images of exoplanet show it orbiting its star

CATEGORIZED UNDER: Astronomy, Pretty pictures
MORE ABOUT: Herschel, TW Hydrae, water

Comments (45)

  1. FC

    Not exactly on topic, but wanted to post just in case Phil Plait missed this: http://www.pbs.org/wgbh/nova/physics/fabric-of-the-cosmos.html
    Brian Greene has been busy.

  2. But we still haven’t spotted another Earth-like planet, and even if we do, will it have water?

    would it be Earth-like if it didnt have water?

    (yeah yeah, i presume you just mean size and that it is in the goldilocks zone)

  3. Pete Jackson

    Water, water, every where,
    Nor any drop to drink.

  4. Reverend J

    Maybe that’s why the aliens haven’t invaded earth yet! They don’t need to steal our water if they can pluck it out of space over there!

  5. Charlie

    To me, it always seemed sensible to assume that our solar system is typical, at least until proven otherwise. My impression is that the field of astronomy has taken the exact opposite approach. Is this correct? If so, is there any good explanation for it? (I understand the anthropic principle, but why appeal to this when there is no data saying you need to?)

  6. noen

    So could this be where life gets it’s first start? Could there be organic synthesis going on there? At least maybe enough to form the first organic compounds which could later “seed” any planets that form?

  7. stjobe

    @5, Charlie:
    With a sample size of one, there’s not enough data to say either way if it’s typical or atypical. Our solar system might fall anywhere on the scale from typical to atypical, and hence it’s better not to assume it’s typical. For all we know it’s unique in at least one respect: It’s the only one with humans in it :)

  8. stjobe said:

    For all we know it’s unique in at least one respect: It’s the only one with humans in it

    One can only hope.

  9. Infinite123Lifer

    H20 just sprouts up (pardon the botany reference) in astronomical quantities here & there? (understatement of the year candidate) Hmmm? What events could percipitate such enourmous pooling. H20 is such an amazing molecule! To create large amounts of water in space you will need. . . .

    Any solution’s :-D

    How about a lot of stuff we will call space, throw in other stuff we call forces & elements & voila!

    Doh. . . and something we call time.
    I didn’t want to get to technical. . .:-)

  10. Carey

    Only thousands of oceans’ worth? For astronomy, “thousands” is not a very big number.

  11. Baris

    Wait, Europa and Enceladus are ENTIRELY made of water? There’s no rock? If they had oceans would the ocean floor just be the core of the moon?

  12. Mittop

    Anyone else reading this reminded of Larry Niven’s novels “The Integral Trees” and “The Smoke Ring”?

  13. Mike Torr

    Water, water everywhere, NAND any drop to drink. Coleridge had no idea about Boolean logic…

    Anyway, this is very cool, and reminds me of Larry Niven’s “The Integral Trees”.

  14. So the aliens in V (first version) were REALLY wasting their time here.

  15. Relativity

    So will this system make a ‘thousand” Earth-like planets? Hmmmm…

  16. uudale

    I may be mistaken about this, but isn’t water the most abundant chemical compound in the universe? Not in liquid form, of course, but doesn’t it exist in large quantities as molecules in the interstellar medium?

  17. Roger

    @Cardos 14,
    So were the aliens in “Battle Los Angles”. Probably because we have so much Ortho water….Para water has a funy taste and smell. ;)

  18. Jeff

    It might also bolster the idea that most of earth’s oceans were derived from infalling comets billions of years ago. There is a lot of water available from the outer solar system.

  19. Jess Tauber

    I’ll be ever more impressed if someone finds a Jupiter-sized inflatable pool toy.

    BTW, any info on whether the water is chlorine-treated? Last thing we need is to catch some space bug on our next visit.

  20. Andrew W
  21. Chris

    To the folks at NASA making the spectra, something I always tell my students. Label your axes! There are no units on the x-axis. I’m guessing it’s in km/s, to adjust for the Doppler shift, but it’d be nice to put something on there.

  22. Johan

    @16 uudale: No, water is not the most abundant molecule, H2 (hydrogen gas) is by far the most abundant one. And also CO (carbon monoxide) and perhaps OH (hydroxyl) are more abundant than H2O. But it is difficult to study H2O abundances from ground, since we have got a lot of it in the atmosphere – that’s why we sent up Herschel in space.

  23. Flunky #2

    @Chris 21
    This graphic was designed primarily for the general public, where simplifying things tends to make the key points most accessible.

    Rest assured, the fully-labeled version is available in the paper:
    http://www.sciencemag.org/content/334/6054/338

  24. amphiox

    @11,

    I’m pretty sure Europa and Enceledas have rocky cores.

  25. katwagner

    So cool! Last night on PBS’ Nova, the astronomers talked about how liquid methane lakes and rain on Titan (?) — anyway, Jupiter’s and Saturn’s moons possibly have the right elements for life. The element of energy found on the moons comes not from the sun, but from friction from the large planets: Saturn and Jupiter. The moons are all cracked and might have water.

    Liquid is needed to facilitate chemical reactions – but all you scientists know this. The little satellite that landed in the Utah desert a few years back was full of comet stuff and the amino acid that starts with “g” so they’re pretty sure life is all over the universe and want to find some PDQ.

  26. Joseph G

    I’ve often wondered if it’d be possible for a big planet-sized blob of liquid water to form in space, with no crunchy center? The main problem I could see would be solar wind splitting up water molecules and sweeping the component atoms away, in the absence of a magntic field such as Earth has.

  27. Impulse725

    On Europa: “Slightly smaller than Earth’s Moon, Europa is primarily made of silicate rock and probably has an iron core. It has a tenuous atmosphere composed primarily of oxygen. Its surface is composed of ice and is one of the smoothest in the Solar System. This surface is striated by cracks and streaks, while craters are relatively infrequent. The apparent youth and smoothness of the surface have led to the hypothesis that a water ocean exists beneath it”

    “It is believed that Europa has an outer layer of water around 100 km (62 mi) thick; some as frozen-ice upper crust, some as liquid ocean underneath the ice. Recent magnetic field data from the Galileo orbiter showed that Europa has an induced magnetic field through interaction with Jupiter’s, which suggests the presence of a subsurface conductive layer. The layer is likely a salty liquid water ocean. The crust is estimated to have undergone a shift of 80°, nearly flipping over (see true polar wander), which would be unlikely if the ice were solidly attached to the mantle. Europa probably contains a metallic iron core.”

    Presumably entirely water was meant for effect, not the actual composition. It is a lot of water though.

  28. PayasYouStargaze

    @26 katwagner

    On BBC’s QI they also discussed methane lakes and rain on Titan. One of the guests was Prof. Brian Cox, who named Titan as the moon most likely to be inhabited by Ewoks. The conversation then moved on to the particulars of tossing an Ewok into a lake of fart. lol

  29. Messier Tidy Upper

    Superluminous news and great write-up. Thanks BA. :-)

    @15. Relativity : “So will this system make a ‘thousand” Earth-like planets? Hmmmm…”

    Not likely. Because water doesn’t just turn into earth-like planets.

    FWIW there’s (almost certainly) an awful lot of water inside Jupiter ..and Neptune .. and Pluto and other planets in our solar system.

    The gas giants and ice dwarfs probably contain many tens if not hundreds of earth masses of water. Pluto, Eris, Ceres and the other ice dwarfs are mostly frozen water mixed withrock – ditto comets and some asteroids. pOh plus many of the outer planet’s moons are primarily ice (eg. Mimas, Enceladus, Miranda) or ice-rock mixtures (Europa, Ganymede, Charon) too.

    We also think that Venus and Mars had oceans once but Venus grew too hot and Mars was too small to retain much atmosphere and thus cooled down too much. Mercury and the Moon have traces of water in polar comets although they likely didn’t form with much.

    So of all the water in the solar system only a tiny percentage ended up on Earth.

    I expect the same will apply for TW Hydrae too with most of the thousand masses of water going into objects that are NOT Earth-like planets.

  30. DataJack

    Few things make me love science more than the fact that we can use our understanding of proton properties to determine the temperature of water in space, hundreds of light years away.

  31. uudale

    @22 Johan,

    Thank you. I was thinking about what was the most abundant compound (two different elements) that wasn’t a diatomic molecule like H2.

  32. Messier Tidy Upper

    @ 30. MTU :

    I expect the same will apply for TW Hydrae too with most of the thousand masses of water going into objects that are NOT Earth-like planets.

    (For clarity : ) Although, hopefully, there *is* one or two or three earth-masses of water going into forming oceans on one or two or three earth-like planets and/or moons in the TW Hydrae system still! ;-)

    Wonder how long before planets finish forming there and what sort of worlds there’ll be and evolve into?

  33. Betul

    When talking about cold water in space, what is the temperature range? I am curious if it is still in liquid state or does it actually mean ice when referred to cold water?

  34. CarlNB

    What is the most important thing that we have learned from all this? We have learned something that has always been a pet suspicion of mine. We have learned that we should be careful not to “overly conclude” from something that may just be a coincidence. As I read I automatically assumed, from the star’s name, that we knew about this water all along, but not so. Perhaps, similarly, the emigrants that came at the time of the land bridge over the Bering Straits came by boat. We should be careful about “over concluding”.

  35. @35. Betul asks :

    When talking about cold water in space, what is the temperature range? I am curious if it is still in liquid state or does it actually mean ice when referred to cold water?

    Ice usually & generally amorphous ice which is a formof ice not usually found on Earth. (Click on my name here for relevant wikipedia entry for that info & source.)

    Although it depends exactly where that water is and what pressures its under.

    Liquid water is very rare requiring a specific temperature and pressure range. It’s found only on Earth at the surface although soem may temproarily be present on Mars whereas elsewhere frozen water will sublimate or go straight into vapour – gaseous – phase state.

    Liquid water – oceans – may exist beneath the icy crust of Europa and some other Jovian moons and maybe also true for Saturnean, and other outer planetary moons even including possibly Pluto & Charon. Pus comets and some asteroids.

    Ice also forms a variety of types – not just our familiar “ice I” – some of which can endure high temperatures and pressures. Hence many “SuperEarths”or “gas dwarfs” as MIT exoplanet hunter Sara Seager more perhaps accurately describes them (eg. Gliese 436 b, Gliese 581 d, HD 181433 b) are sometimes dubbed “Hot Ice” planets because they may have layers of these high-pressure ices beneath steamy dense atmospheres and no solid surface.

    I’m not sure how many Earth-masses of ice exist in our solar system but most of the water in our solar system is NOT found on Earth. Which is kind of a good thing because if it was, its doubtful we’d have any solid land at all! ;-)

    *****

    Once thought to be rocky, we now believe Ceres may contain 200 million cubic kilometres of water in its mantle. This is more than the amount of fresh water on the Earth.
    - Page 10, “Ceres may be a failed miniplanet” by Jeff Foust in Astronomy Now magazine, November, 2005.

  36. Liquid water – oceans – may exist beneath the icy crust of Europa and some other Jovian moons and maybe also true for Saturnean, and other outer planetary moons even including possibly Pluto & Charon.

    Click on the link in my name for this comment or search space-dot-com for the ‘Pluto’s Moon is an Ice Machine’ article for one source on that. There was a good article about a possible sub-Charonian sea in New Scientist – or was it an astronomy magazine about that possibility as well.

    Much of the water in our solar system is mixed with other compounds – such as I gather on our own Moon.

    Mars may have huge aquifers of permafrost and even liquid water beneath its sands of rust and basalt surface as Kim Stanley Robinson speculates in his Mars trilogy.

    Venus could well have had an immense ocean or three early in its planetary history when our Sun was much cooler before our daytime star grew too luminous and boiled those Cytherean seas away.

    When our solar system was young there could well have been three planets with oceans, seas and lakes of liquid water before Venus suffered a runaway greenhouse effect due to its proximity to the Sun and Mars, lacking sufficient mass, lost its magnetic field and early denser atmosphere preventing liquid water from being stable on its surface. Chance could well have deprived us of having three (unprotected human~)habitable worlds in our solar system had Mars been a little more massive and located where Venus orbits or just outside that and Venus be orbiting where Mars is today. Maybe?

    As it is there may still be life on a number of worlds with watery ecologies in our solar system not just obvously present on Earth but as well below the Europan ice, underground Martian microbes, even Charonean cave dwelling waterbugs near its still warm core and possibly more. But then also maybe not.

    So much we still have to discover. So many unanswered questions and speculations that may or may not have factual equivalents.

  37. R. D. McConnell

    Where is the definitive scientific evidence that “water” is necessary for life? Or “Life as we know it”, or, for that matter, the existance of “black matter”?

    My suspicion is the same in both cases: it doesn’t exist in scientifically provable form.

    I’m an atheist, so I’m not asking this as some religious nut-case, but rather as an interested, educated person.

  38. Dragonfly

    Hm, sounds remarkably similar to the ‘earth canopy’ theory, which hypothesis the earth once had a ‘canopy’ of water or ice in its upper atmosphere.

  39. Nigel Depledge

    Cardoso (14) said:

    So the aliens in V (first version) were REALLY wasting their time here.

    No, the water was a cover story. They actually came here to harvest people for food.

    But, to be frank, the cover story was so flimsy that everyone should have seen through it from day one. Why go so deep into a star’s gravity well to get water that is abundantly available in the Kuiper Belt (and perhaps even more so in the Oort Cloud)?

    If they were really after water, they could have made off with a few dozen KBOs and we would never even have noticed (unless they took Pluto).

  40. Nigel Depledge

    Pete Jackson (3) said:

    Water, water, every where,
    Nor any drop to drink.

    Ah, yes, from early in Part the Third. Funnily enough, Phil’s title reminded me of the beginning of Part the Fourth:

    (After the mariner assures the wedding guest that he did not die along with the rest of his crew-mates, and therefore isn’t some undead thing, he resumes the narrative: )

    Alone, alone; all, all alone. Alone on a wide, wide sea;
    And never a saint took pity on my soul in agony.
    The many men so beautiful, and they all dead did lie,
    And a thousand, thousand slimy things lived on; and so did I.

  41. Nigel Depledge

    Chris (21) said:

    To the folks at NASA making the spectra, something I always tell my students. Label your axes! There are no units on the x-axis. I’m guessing it’s in km/s, to adjust for the Doppler shift, but it’d be nice to put something on there.

    Actually, since this is an IR spectrum, the x-axis might well be in per centimetres (cm^-1).

  42. nomuse

    Nigel…it was worse than that. The 1983-series Visitors made a big deal about wanting to trade for certain (unnamed) “chemicals.” They went so far as to park a ship and run hoses to a chemical plant…but as Donovan later discovered, they were drying the solution and sifting the precipitate back down over LA (talk about your chemtrails!) — keeping only the water.

    What a run-around that was! At least they could have claimed they were doing their own heavy-water extraction. Or just, you know, asked for water. It isn’t like a couple of city-diameter ships are going to be able to carry away that much, not in comparison with the size of Earth’s oceans!

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