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Harvard Astronomers Challenge Theory That 'Oumuamua Was a Nitrogen Iceberg (livescience.com) 50

Posted by EditorDavid from the not-nitrogen dept.
"Although Oumuamua probably isn't some probe looking for humpbacked whales," writes Slashdot reader alaskana98, "it does continue to deliver plenty of intrigue — and controversy — for those astronomy buffs out there.

"In the latest move in the war on who gets to define what exactly OuMuaMua is, Harvard astrophysicists Amir Siraj and Avi Loeb have countered the prevailing hypothesis that it is a frozen chunk of nitrogen with their own — that it is simply not possible."

LiveScience reports: According to Siraj and his co-author, Harvard astrophysicist Avi Loeb, Jackson and Desch's conclusion that 'Oumuamua is a nitrogen iceberg is flawed because there isn't enough nitrogen in the universe to make an object like 'Oumuamua, which is somewhere between 1,300 and 2,600 feet (400 and 800 meters) long and between 115 and 548 feet (35 and 167 m) wide.

Pure nitrogen is rare, Siraj said, and has been found only on Pluto, where it makes up about 0.5% of the total mass. Even if all of the nitrogen ice in the universe was scraped off every Pluto-like planet that's predicted to exist, there still wouldn't be enough nitrogen to make 'Oumuamua.
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Harvard Astronomers Challenge Theory That 'Oumuamua Was a Nitrogen Iceberg More

Harvard Astronomers Challenge Theory That 'Oumuamua Was a Nitrogen Iceberg

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  • How could they possibly know? (Score:4, Interesting)

    by Shaeun ( 1867894 ) on Saturday November 20, 2021 @11:37AM (#62005051)
    I mean seriously, our sample size of the universe is extremely small, how could they possibly know based on the sample set we have. It could have been pure nitrogen, it could have been pure unobtanium... But the argument presented has no basis because there is no way to create the conclusion.

    • Re:How could they possibly know? (Score:4, Informative)

      by Baron_Yam ( 643147 ) on Saturday November 20, 2021 @11:44AM (#62005071)

      Not only that, but their math is awful.

      "Pure nitrogen is rare, Siraj said, and has been found only on Pluto, where it makes up about 0.5% of the total mass. Even if all of the nitrogen ice in the universe was scraped off every Pluto-like planet that's predicted to exist, there still wouldn't be enough nitrogen to make 'Oumuamua"

      Except that Pluto is what, 19 orders of magnitude more massive than Oumuaua? And the surface of Pluto is supposedly 98% nitrogen ice.

      Until Siraj does the math long form and shows the work, even as a complete lay person I'm going to ignore this.

      • Re:How could they possibly know? (Score:5, Interesting)

        by CrimsonAvenger ( 580665 ) on Saturday November 20, 2021 @12:08PM (#62005123)

        Yah, looks to me like someone lost track of some unit conversions when estimating the amount of nitrogen available. Hell, the planet we're all sitting on has (admittedly not frozen) around 4,000,000,000,000,000 tons of nitrogen in its atmosphere.

        Oumuamua was rather less than a quarter million tons of nitrogen...

        • Re: (Score:2)

          by splutty ( 43475 )

          For it to be a Chunk Of Ice, it needs to have split from something that IS that ice. There isn't any conceivable manner in which there is a pure nitrogen ice sheet, ball, blob, ocean, whatever the hell, that a chunk the size of the object could've been sheared off.

          It's not about "Total nitrogen in non ice, spread out, unusable form", it's specifically about "A chunk of nitrogen ice".

          If you could purify and freeze all the nitrogen on earth, well, we'd have an issue breathing.. But you get the point, I hope.

          • Didn't this space rock fly in from another galaxy? How do we know such a ball of frozen nitrogen doesn't exist? Could of broken off of some other object or even could of been significantly bigger but over the eons lost some of it's mass.

            Since we don't really know it's origins, it could be a chunk of nitrogen ice. I don't know myself, I'm not an astronomer.

            • Almost certainly not another galaxy, but yes, I believe you meant did it come from outside of our solar system. Yes, they predict that it did based on it's trajectory through our solar system. And of course, they don't profess to know what it was.
      • From the article: "Siraj and Loeb did not find that we made a mistake, and so they should have accepted the numbers we got," Desch told Live Science in an email. "Instead, they attempted their own back-of-the-envelope calculation and made a great number of approximations and estimates, and came up with different numbers that they say aren't favorable."

        • Of course, an Editor would realise this and think twice about publishing the story, or issue a correction.

          But: Slashdot.

      • The surface ice is indeed a very small part of the mass of pluto, you're going waaay overboard in your own arrogance, even worse than these idiot physicists.

        • Large impactor hits pluto, ejects a bunch of ice on an extra-solar voyage, oumuamua is born.

          This isn't, "We shot a laser at the rock and it turns out it wasn't what we thought." This is, "We made a bunch of assumptions that show that whatever this rock is, there's no way this other guy can possibly be right about what it might be."

          Wake me up on data.

          • Sure. Like the "other guy" said, they didn't find any mistakes in the math, so (paraphrasing) they should shut up.

          • That's a pretty unlikely outcome for a large impactor, isn't it? Don't those usually result in something more like an ejecta cloud, and not a single solid object? Plus the localized heating on impact would seem to suggest at least some of nitrogen would be converted to gas and not solidify into a large coherent object.

            It seems like this thing is torn between two sides, one side who wants a simplified answer and another who wants an extremely unlikely answer, closing the door on other speculation.

      • Considering that our planets atmosphere is > 70% nitrogen you are right.

    • It could have been pure nitrogen, it could have been pure unobtanium.

      There is not enough unobtainium in the whole universe to prove a negative, so we know the physicists didn't build their hyp^H^H^speculation from that!

    • Re: (Score:2)

      by PLAST ( 416196 )

      It's just a misleading formulation in the livescience article uncritically copy+pasted into the summary. From the article abstract:

      [W]e show that the mass budget in exo-Pluto planets necessary to explain the detection of ‘Oumuamua as a nitrogen iceberg chipped off from a planetary surface requires a mass of heavy elements exceeding the total quantity locked in stars with 95% confidence [...]

    • Re: (Score:2)

      by hey! ( 33014 )

      Nitrogen is actually pretty common in the universe; we can tell by looking at spectra. Overall it's the seventh most abundant element in our galaxy judging by spectra. But in the Solar System it's distributed unevenly; it's common on Earth where it makes up 78% of the atmosphere but rare on the Moon. It's common in some classes of asteroids but not others.

      Clearly the hypothesis that Oumuamua was mostly nitrogen would make it unlike Pluto, or indeed any other *known* object. There are other objects like

    • Summary Wrong! (Score:4, Informative)

      by Roger W Moore ( 538166 ) on Saturday November 20, 2021 @02:43PM (#62005551) Journal
      As usual, the summary is written by someone who did not read and understand even the abstract. They are NOT saying that there is not enough nitrogen in the universe since that would clearly be utter nonsense. What they are saying is that the model that OuMuaMua is a pure nitrogen iceberg that chipped off some planetary surface is not consistent with the amount of nitrogen available on planets.

      I am not an astrophysicist so I have no idea how plausible this argument is. However, since it relies on the amount and distribution of nitrogen in a solar system not on the total availability of nitrogen in the universe it is not one that can be immediately dismissed as obviously wrong.

    • Scientific click bait.

    • Re: (Score:1)

      by einyen ( 2035998 )
      I wonder if we know the trajectory of Oumuamua precisely enough, so that we can find it again, when we in 100+ years hopefully have the propulsion technology to catch up to it. It was only leaving the Solar system at about 70,000 mph or about 0.01% of light speed, so even with 100+ years of head start, we would only need a few percent of light speed to catch up quickly.

  • It was a spaceship.

    Simple as.

  • Conversely, if it were made of nitrogen, then there would be more in the universe than we previously knew about. Guessing we remote detect gaseous nitrogen from absorption and emission lines, but solid stuff?

  • For some reason, TFA reminds me of Larry Niven's "Ringworld" which was built by Pak Protectors who were able to transmute the mass of a gas giant like Jupiter into scrith and created the structure around the star.

    But that's what makes 'Oumuamua so fascinating, he [Siraj] added. "I don't really care what it is, because every single possibility is an astrophysical object we've never seen before, so that's why it's exciting."

    So if you're middle aged and see something that looks like a tree root that smells wonderful, don't eat it.

  • It’s actually aliens... (Score:5, Funny)

    by burtosis ( 1124179 ) on Saturday November 20, 2021 @12:13PM (#62005139)
    Plot twist, it was A ginormous nitrogen iceberg. You see, aliens have been hanging out around the edge of the heliosphere, lobbing objects through on very large eccentric and interstellar like orbits, starting with the common stuff and getting more and more unlikely. It’s half an intellectual test but mostly they find it extremely funny.

  • The original paper (Score:5, Informative)

    by ortholattice ( 175065 ) on Saturday November 20, 2021 @12:18PM (#62005157)
    Here is the actual paper: https://arxiv.org/abs/2103.14032 [arxiv.org]

  • when the stuff is so rare and alienz are so abundant.

    Poster child for abolishing tenure.

  • Next time we see something like this, we should see if we can adjust it's trajectory so that we can get it to Mars. We need all the Nitrogen we can get to enhance its atmosphere and use as fertilizer for crops.

    Too bad that reality says that if it's big enough to be helpful, it's too massive to redirect.

    • Bezos Dr. Evilesque rocket could entice it to submit.

    • Surface gravity of Pluto is something like 1/16th that of Earth's.

      I say, send a nuclear powered harvester to Pluto to break off chunks and lob them towards Mars. Nitrogen the HELL out of that planet.

      Actually no. Use Charon instead, then there's half again as little gravity to deal with.

  • Comment removed based on user account deletion

  • Desch's conclusion that 'Oumuamua is a nitrogen iceberg is flawed because there isn't enough nitrogen in the universe to make an object like 'Oumuamua, which is somewhere between 1,300 and 2,600 feet (400 and 800 meters) long and between 115 and 548 feet (35 and 167 m) wide.

    ORLY?

    The universe is a big place and even one Pluto has a lot of nitrogen ice. So (ignoring all the OTHER pure nitrogen lying around in the universe - such as in - and "blowing off" from, the atmospheres of planets like Earth...):

    mass of Pluto = 1.30900 x 10^22 kilograms
    Pure nitrogen [ice] is rare, Siraj said, and has been found only on Pluto, where it makes up about 0.5% of the total mass.
    mass of nitrogen ice on Pluto: 6 x 10^24 g
    Nitrogen frost [as glaciers on Pluto's surface under its gravitational field] has a density of 0.85 g cm^â'3. [enough denser than water ice that water icebergs float on nitrogen frost glaciers]
    volume of nitrogen ice on Pluto: 7 x 10^18 m^3
    volume of nitrogen ice in Oumuamua (using upper numbers for dimensions: 800 x 167 x 167 m and treating it as a rectangular solid): 2.23 x 10^7 m^3

    So unless I made a mistake above, just the nitrogen frost on ONE Pluto, not even accounting for expansion due to lower self-gravity, could build over thirty billion rectangular-solid flying nitrogen frost blocks big enough to carve into full-sized Oumuamuas of the maximum of its estimated dimensions.

    Now consider that there are 1.25Ã--10^11 galaxies in the observable universe, and even at only one Pluto-like object per galaxy that's a LOT of nitrogen ice. At another factor of 10^11 stars per galaxy, even if Pluto-like objects are rare there's a few more orders of magnitude to multiply by.

    So I think somebody slipped a decimal point somewhere. By a bunch. Can somebody check the numbers above to see whether it's me, rather than the guys at Harvard?

    • The actual article is that for it to be a chip off of a terrestrial body that is pure nitrogen, given what we know about planetary formation, is impossible.

      The summary is very simplistic and misleading.

    • So unless I made a mistake above, just the nitrogen frost on ONE Pluto, not even accounting for expansion due to lower self-gravity, could build over thirty billion rectangular-solid flying nitrogen frost blocks big enough to carve into full-sized Oumuamuas of the maximum of its estimated dimensions.

      The authors seem to base their calculations on an earlier published estimate of 'Oumuamua having a 450 million year lifetime and being ejected by a young star.

      If I interpreted their paper [arxiv.org] correctly, the first thing to account for is that the nitrogen fragment production rate back then would need to have been 2 orders of magnitude greater than expected in order to explain the rate at which these objects are detected. The second thing is that the estimated sublimation and cosmic ray erosion over that time wou

  • It looks like a turd, so it's obviously space whale fecal matter. I mean. It's only logical and obvious!

  • PSA: The summary sucks (Score:3)

    by bill_mcgonigle ( 4333 ) * on Saturday November 20, 2021 @04:35PM (#62005781) Homepage Journal

    Everybody here is being viscous because they think "LiveScience" knows what they're talking about but the Chair of the Harvard Astrophysics Department doesn't.

    Perhaps they have amnesia about Gell-Mann Amnesia?

    Anyway, if you track it, it didn't even travel through our solar system - our solar system passed by it. The thing is in the equivalent of a geostationary orbit for our galaxy.

    It's super-reflective and would make a good navigational marker even if it's completely natural.

    • Anyway, if you track it, it didn't even travel through our solar system - our solar system passed by it. The thing is in the equivalent of a geostationary orbit for our galaxy.

      What? The term "geostationary" doesn't make sense for comparison, as galaxies have no equivalent surface for 'Oumuamua to remain facing against, aside from maybe the surface of our galaxy's central black hole Sagittarius A*. But that is spinning incredibly fast in comparison, so there's nothing that can be stationary with regards to that.

      Maybe you meant that 'Oumuamua has a near-zero orbital speed around the center of the Milky Way, i.e. that it isn't orbiting around the galaxy like the star systems are, bu

    • The thing is in the equivalent of a geostationary orbit for our galaxy.

      Interesting frame of reference you've got there but possibility a wee bit subjective...

  • There's more Nitrogen in our atmosphere than (supposedly) in Oumuamua. So how can we conclusively say it is impossible for enough Nitrogen to exist in ice form somewhere from where a chunk like Oumuamua could come off?

    The universe if ... fucking huge. Huge enough and old enough to see many things possible. It is not just possible, but inevitable for a world with as much atmospheric nitrogen as Earth to, say, get knocked off its original orbit and star system, and then freeze its balls off away as it trave

  • Their argument seems to apply to N2 icebergs chipped off or pluto-like objects, but how well known is it that there are not nitrogen asteroids in some solar systems? Is it possible to have the right combination of conditions that N2 would condense to solid, similarly to the way we can get object in our solar system that are substantially made of ice.

  • If this argument is true, then these Harvard boys have explored the entire universe and found all that it contains... after all they are apparently able to assert with certainty that there's not enough nitrogen in the ENTIRE UNIVERSE to make an object so small it can barely be seen by people with their most powerful telescopes as it passes near this teensy tiny planet orbiting a tiny insignificant star in an otherwise unremarkable arm of an unremarkable galaxy...

    Enough nitrogen to make a thousand oumuamua's

  • Pure nitrogen is rare, Siraj said, and has been found only on Pluto ... Even if all of the nitrogen ice in the universe was scraped off every Pluto-like planet that's predicted to exist, there still wouldn't be enough nitrogen to make 'Oumuamua

    Maybe the reason that pure nitrogen is rare on planets is because it is mainly found in Oumuamua style objects floating around in the (non-planetary) universe?

  • I have read the LiveScience press release (LiveScience is the publisher) and the abstract of the paywalled paper (which I cannot retrieve even using SciHub) so all I know is what it is in these two pieces of text, but the claims as presented are preposterous.

    The press release asserts as their conclusion:

    Pure nitrogen is rare, Siraj said, and has been found only on Pluto, where it makes up about 0.5% of the total mass. Even if all of the nitrogen ice in the universe was scraped off every Pluto-like planet that's predicted to exist, there still wouldn't be enough nitrogen to make 'Oumuamua.

    The mass of Pluto is 1.3*10^22 kg. Using 0.5% as the nitrogen content, we have 6.5*10^19 kg of nitrogen on Pluto. The maximum possible mass of 'Oumuamua, using the values in the press release, is 167*167*80

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