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Thread: Interstellar Comet

  1. #31
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    Radio observations are sometimes made from asteroids. I found one hint about passive research, and lots about active radar research. Even with some emitter and a different telescope receiving, although usually the emitter and receiver are the same (Green bank, Arecibo and others). Also, the ATA is not used just for SETI purposes.

    https://www.ieee.ca/millennium/aro/ARO_found.html

    Our companions in the solar system - planets, asteroids and comets emit waves detectable by radio telescopes on earth. These signals reflect temperature variations on planetary surfaces or within their atmospheres. From these radiations, composition and structure of the atmospheres and surfaces of other members of the solar system can be assessed
    Perhaps a bit more searching on ADS can yield some papers but I don't have time for that now.
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  2. #32
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    Quote Originally Posted by schlaugh View Post
    Sounds more like a publicity stunt just to draw eyeballs and clicks and donations. What can they possibly “hear” from an asteroid?


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    What if it's not an asteroid? But, in the unlikely event that it is a Super Voyager, on a Grand Tour of local stars. It's communication beam is probably a tight beam, pointed at its home system. Very slim chance of picking up any signal, if we even have the technology to receive such a signal.

  3. #33
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    Quote Originally Posted by Superluminal View Post
    What if it's not an asteroid? But, in the unlikely event that it is a Super Voyager, on a Grand Tour of local stars. It's communication beam is probably a tight beam, pointed at its home system. Very slim chance of picking up any signal, if we even have the technology to receive such a signal.
    Unlikely, but not impossible. There might be backscatter from the solar system's Zodiacal dust, for example.
    Selden

  4. #34
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    Quote Originally Posted by tony873004 View Post
    I'm just guessing, but I doubt that DAWN's camera is optimized for long-exposure deep sky observing, as its primary mission is to study something bathed in bright sunlight.

    Here are a few more animations and simulations of A/2017 U1 that I made that I posted on my Twitter account.
    https://twitter.com/tony873004/statu...34271495254018
    https://twitter.com/tony873004/statu...28678963658752
    https://twitter.com/tony873004/statu...09368903622656
    https://twitter.com/tony873004/statu...37689843023872
    I wonder if the possible orbit of planet nine is nearby

  5. #35
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    It now has a official name - 1I/2017 U1 (originally designated A/2017 U1) common name: 'Oumuamua.

    http://www.popularmechanics.com/spac...t-gets-a-name/

    The nomenclature problem is that the current designation scheme for comets and asteroids, established by the IAU's Minor Planet Center, does not allow a name to be given to an object based on such a short period of observation. However, this brief glimpse of A/2017 U1 was probably the only opportunity astronomers will have to observe the object before it leaves the solar system forever. "Due to the unique nature of this object, there is pressure to assign a name," the Minor Planet Center reported.

    And so a new naming style was born. The IAU Minor Planet Center established a preliminary naming scheme using the designation "I" for interstellar, rather than "C" for comet or "A" for asteroid. A/2017 U1 has now been designated 1I/2017 U1, and the astronomers who discovered the interstellar visitor using the Pan-STARRS 1 telescope on the volcano Haleakalā in Maui have also given the object a common name: 'Oumuamua.

  6. #36
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    Uh...Uh...

    The name 'Oumuamua is Hawaiian (for the location from which it was initially spotted) and roughly translates to "first scout" or "first messenger".

    Ah.... That feels better.
    0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 ...
    Skepticism enables us to distinguish fancy from fact, to test our speculations. --Carl Sagan

  7. #37
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    Quote Originally Posted by 01101001 View Post
    By the way, now 1I/ʻOumuamua
    0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 ...
    Skepticism enables us to distinguish fancy from fact, to test our speculations. --Carl Sagan

  8. #38
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    If 1I/ʻOumuamua had been a red dwarf star instead of an asteroid, the orbits of the planets would have been heavily perturbed. Earth's new semi-major axis would be > 7 AU.
    Here is a simulation of our new solar system. It will run in your browser.
    http://orbitsimulator.com/gravitySim...RedDwarf..html

  9. #39
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    Quote Originally Posted by tony873004 View Post
    If 1I/ʻOumuamua had been a red dwarf star instead of an asteroid, the orbits of the planets would have been heavily perturbed. Earth's new semi-major axis would be > 7 AU.
    Here is a simulation of our new solar system. It will run in your browser.
    http://orbitsimulator.com/gravitySim...RedDwarf..html
    Well, that would have solved global warming.

  10. #40
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    What a mess, would have to make changes to my garden planting schedule between the mini ice ages.

  11. #41
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    Now we have a bit more information of our visitor from out of our solar system.

    It is cigar shaped and rotates once every 8 hours. It measures 180 meters by 30 meters. It is travelling at 40,000 miles per hour. There is no coma - a nebulous envelope of dust and gas created when comets heat up as they pass near the sun - is apparent. The WIYN team also failed to see a tail, the signature feature of a comet. It also has a reddish tinge and a low albedo, suggesting 1I/2017 U1 lacks the coating of ice that many comets acquire as they spend most of their time in cold storage in the outer reaches of the solar system.

    All the above suggest to me, it might be a space craft from another solar system.

    http://www.spacedaily.com/reports/Im...stery_999.html

    strange visitor, either asteroid or comet, zipping through our solar system at a high rate of speed is giving astronomers a once-in-a-generation opportunity to examine up close an object from somewhere else in our galaxy.

    "It's a really rare object," explains Ralf Kotulla, a University of Wisconsin-Madison astronomer who, with colleagues from UCLA and the National Optical Astronomy Observatory (NOAO), used the 3.5 meter WIYN Telescope on Kitt Peak, Arizona, to take some of the first pictures of the solar system interloper.

    The object, known to astronomers as 1I/2017 U1, measures 180 meters by 30 meters. In shape, the object resembles a fat cigar, half a city block long, and was first discovered Oct. 19 by astronomers at the University of Hawaii combing the sky for near-Earth objects. Since then, astronomers who have access to telescope time have been zooming in on the object to see what they might learn.

  12. #42
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    30 by 180 meters indicates a remarkably long, thin object, about 6 times longer than it is wide. The longest asteroid I found listed was 624 Hektor, which is apparently about 1.85 times longer than its width. It's thought to be made of two shorter asteroids, joined at the ends.
    Last edited by Ross 54; 2017-Nov-17 at 03:39 PM.

  13. #43
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    Quote Originally Posted by selvaarchi View Post
    It is cigar shaped and rotates once every 8 hours.
    Uh oh....not about the long axis I hope?

  14. #44
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    Interstellar object

    From Pirx´s Tale:
    Quote Originally Posted by Pirx
    The screens were blank. A routine shower, I thought. But the noon bulletin was far from routine: Luna’s long-range trackers had traced the swarm to another system!
    It was the second such swarm in astronautical history. Meteoroids travel along elliptical paths gravitationally tied to the sun like yo-yos; an alien swarm from outside the solar system, from somewhere in the galaxy at large, is regarded as a sensation, although more by astrophysicists than by pilots. For us, the difference is one of speed. Swarms in our own system travel in circum-terrestrial space at speeds no greater than the parabolic or the elliptical; those from outside may—and, as a rule, do—move at a hyperbolic velocity. Such things may send meteoritologists and astroballisticians into ecstasy, but not us.
    The radiotelegraph operator was fazed neither by the news nor by my lunchtime lecture.
    What actually was found inside the swarm, though:
    Quote Originally Posted by Pirx
    At exactly twenty-two kilometers, the other ship began to outstrip the Pearl. From now on the values would increase, which meant we were in the clear. All this time my eyes had been glued to the range-finder. I shifted my gaze back to the radar screen.
    What I saw was not a ship but a flying island. From twenty kilometers away, it now measured about two fingers in width. The perfectly symmetrical spindle had become a disk—better, a ring!
    I know what you’re probably thinking: an alien encounter. I mean, a ship measuring twenty kilometers in length…? An alien encounter. A catchy phrase, but who believes in it? My first impulse was to tail the thing. Really! I even grabbed the stick—then held back. Fat chance I’d have with all that scrap in tow. I heaved out of my seat and climbed a narrow shaft to the small, hull-mounted astrodome atop the cockpit. It was conveniently stocked with telescope and flares. I fired three in quick succession, aiming for the ship’s general radius, and tried to get a sighting in the glare. An island, yes, but still hard to locate right away. The flash blinded me for a few seconds, until my eyes adjusted to the brightness. The second flare landed wide, too far away to do any good; the third, just above it. In that immobilizing white light, I saw it.
    Only a glimpse, really, lasting no more than five or she seconds, because I was using one of those exceptionally bright flares that fade very fast. But in the space of those few seconds, I saw, looking down at an angle through my night glasses, whose eighty-power lenses brought it to within a few hundred meters, an eerily but sharply illuminated mass of metal. So massive, in fact, it barely fit into my field of vision. Stars showed in the center. A sort of hollow, cast-iron, spaceborne tunnel, but—as I noticed in the last glimmerings of light—somewhat squashed, more tire-shaped than cylindrical. I could see straight through the core, even though it wasn’t on the same axis; the monster stood at an angle to my line of vision, like a slightly tipped glass of water.
    There was no time for idle contemplation. I fired more flares; two failed to ignite, the third fell short, the fourth and fifth made it stand out—for the last time. Having crossed the Pearl’s tangent, it sheered off and quickly widened the gap—one hundred kilometers, two hundred, three hundred—until it was completely out of eye range.
    Quote Originally Posted by Pirx
    There are times when the human eye can behave like a camera lens, when a momentarily but brilliantly cast image can be not merely recalled but meticulously reconstructed as vividly as if viewed in the present. Minutes later, I could still visualize the surface of that colossus in the flare’s afterglow, its kilometers-long sides not smooth but pocked, almost lunar in texture; the way the light had spilled over its corrugated rills, bumps, and craterlike cavities—scars of its interminable wandering, dark and dead as it had entered the nebulae, from which it had emerged centuries later, dust-eaten and ravaged by the myriad bombardments of cosmic erosion. I can’t explain my certainty, but I was sure that it sheltered no living soul, that it was a billion-year-old carcass, no more alive than the civilization that gave birth to it.
    But the conclusion was:
    Quote Originally Posted by Pirx
    I sat down and estimated the probability of a sighting through Luna’s giant radiotelescope, the most powerful radioastronomical unit in the system. Powerful, yes, but not powerful enough to pick up a target of that magnitude at a distance of four hundred million kilometers. Case closed. I tore up my computations, got up, and quietly retired to my cabin, feeling as though I had committed a crime. We’d been visited by an intruder from the cosmos, a visit that occurs, who knows, maybe once in a million years—no, once in hundreds of millions of years. And because of a case of the mumps, because of a man named Le Mans and his convoy of scrap, and a drunken halfbreed, and an engineer and his brother-in-law, and my negligence—it had slipped through our fingers, to merge like a phantom with the infinity of space.
    No evidence whatever, in short.
    The Earth of Pirx´ Tale could not spot a dead ship - an asteroid-like object - at a distance of 400 million km. It was only through chance presence of a spaceship illegally passing within 22 km that it was spotted.
    The Earth of 2017 could not spot an asteroid-like object passing at 24 million km, but could and did spot it on the way out, at 30 million km.

  15. #45
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    The article, linked below, has some interesting new details about the hyperbolic visitor to our solar system. The variations in light output, as it rotates, now imply that it is at least 10 times longer than its width. If the ends don't align directly with Earth at minimum brightness, the elongation would be even greater, we're told.

    Not a contact binary, it seems. The object is said to be spinning too fast for this to be a stable configuration. A couple of other, even less probable explanations for this object have been proposed.

    www.bbc.com/news/science-environment-42053634

  16. #46
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    Quote Originally Posted by selvaarchi View Post
    It is travelling at 40,000 miles per hour.....
    So that is 17.88 km/second. The report is that it is interstellar. What is the definitive observation establishing this?

    Quote Originally Posted by Ross 54 View Post
    The article, linked below, has some interesting new details about the hyperbolic visitor to our solar system.
    Yes, its observed path and speed relative to the Sun would confirm whether it was gravitationally captured by our solar system or not. But I question whether speed alone determines this? Don't solar-system-bound meteors occasionally strike earth at velocities higher than that?

    Quote Originally Posted by Ross 54 View Post
    The variations in light output, as it rotates, now imply that it is at least 10 times longer than its width. If the ends don't align directly with Earth at minimum brightness, the elongation would be even greater, we're told.
    That is too weird! The ends align, then it rotates into the full length side view, then back to looking at one end. There is a family of such configurations, which would cover the face of a clock. On the other hand I'm thinking there are only two configurations where it would be rotating and we detect no change in brightness at all ("spinning" counter-clockwise, and clockwise).

    I agree, it is tempting to imagine an intelligent interloper. A craft 4 football fields long, spinning to simulate a spectrum of gravities, just zooming through, now has abundant information about our system.... But if gathering information was its purpose, it would be beaming that information back to its source, not waiting hundreds of millions of years to deliver it in person. And I don't imagine we see any such transmissions. Oh well.

    Has there been any spectral analysis?
    Everyone is entitled to his own opinion, but not his own facts.

  17. #47
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    Quote Originally Posted by Cougar View Post
    Has there been any spectral analysis?
    Apparently yes, and it's red-ish.

    https://www.nature.com/articles/nature25020

    A brief visit from a red and extremely elongated interstellar asteroid
    ...
    Spectroscopic measurements show that the object’s surface is consistent with comets or organic-rich asteroid surfaces found in our own Solar System. Light-curve observations indicate that the object has an extreme oblong shape, with a 10:1 axis ratio and a mean radius of 102±4 m, assuming an albedo of 0.04. Very few objects in our Solar System have such an extreme light curve. The presence of ‘Oumuamua suggests that previous estimates of the density of interstellar objects were pessimistically low. Imminent upgrades to contemporary asteroid survey instruments and improved data processing techniques are likely to produce more interstellar objects in the upcoming years.
    And...
    https://www.eso.org/public/news/eso1737/

    Combining the images from the FORS instrument on the VLT using four different filters with those of other large telescopes, the team of astronomers led by Karen Meech (Institute for Astronomy, Hawai`i, USA) found that `Oumuamua varies dramatically in brightness by a factor of ten as it spins on its axis every 7.3 hours.

    Karen Meech explains the significance: “This unusually large variation in brightness means that the object is highly elongated: about ten times as long as it is wide, with a complex, convoluted shape. We also found that it has a dark red colour, similar to objects in the outer Solar System, and confirmed that it is completely inert, without the faintest hint of dust around it.”

    These properties suggest that `Oumuamua is dense, possibly rocky or with high metal content, lacks significant amounts of water or ice, and that its surface is now dark and reddened due to the effects of irradiation from cosmic rays over millions of years. It is estimated to be at least 400 metres long.

  18. #48
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    Here is an article from NASA on the our visitor.

    https://www.jpl.nasa.gov/news/news.php?feature=7006

    The observations and analyses were funded in part by NASA and appear in the Nov. 20 issue of the journal Nature. They suggest this unusual object had been wandering through the Milky Way, unattached to any star system, for hundreds of millions of years before its chance encounter with our star system.

    "For decades we've theorized that such interstellar objects are out there, and now - for the first time - we have direct evidence they exist," said Thomas Zurbuchen, associate administrator for NASA's Science Mission Directorate in Washington. "This history-making discovery is opening a new window to study formation of solar systems beyond our own."

    Immediately after its discovery, telescopes around the world, including ESO's Very Large Telescope in Chile, were called into action to measure the object's orbit, brightness and color. Urgency for viewing from ground-based telescopes was vital to get the best data.

    Combining the images from the FORS instrument on the ESO telescope using four different filters with those of other large telescopes, a team of astronomers led by Karen Meech of the Institute for Astronomy in Hawaii found that 'Oumuamua varies in brightness by a factor of 10 as it spins on its axis every 7.3 hours. No known asteroid or comet from our solar system varies so widely in brightness, with such a large ratio between length and width. The most elongated objects we have seen to date are no more than three times longer than they are wide.

  19. #49
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    Quote Originally Posted by Cougar View Post
    So that is 17.88 km/second. The report is that it is interstellar. What is the definitive observation establishing this?



    Yes, its observed path and speed relative to the Sun would confirm whether it was gravitationally captured by our solar system or not. But I question whether speed alone determines this? Don't solar-system-bound meteors occasionally strike earth at velocities higher than that?



    That is too weird! The ends align, then it rotates into the full length side view, then back to looking at one end. There is a family of such configurations, which would cover the face of a clock. On the other hand I'm thinking there are only two configurations where it would be rotating and we detect no change in brightness at all ("spinning" counter-clockwise, and clockwise).

    I agree, it is tempting to imagine an intelligent interloper. A craft 4 football fields long, spinning to simulate a spectrum of gravities, just zooming through, now has abundant information about our system.... But if gathering information was its purpose, it would be beaming that information back to its source, not waiting hundreds of millions of years to deliver it in person. And I don't imagine we see any such transmissions. Oh well.

    Has there been any spectral analysis?
    My bold. Observation of the speed relative to the Sun is definitive. If it is more than about 1.414 times what a body in a circular orbit at the same distance would be, it is gravitationally unbound, regardless of the direction of its motion. That is physics-101 conservation of energy. We can get higher speeds relative to Earth in head-on collisions with bound bodies in retrograde orbits.

    I am not the least bit tempted to think it may be an intelligent interloper. I have seen nothing written about it that is contrary to a rock that originally was adrift in interstellar space, perhaps having been ejected from another stellar system, before its current chance close encounter with the Sun.

  20. #50
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    Quote Originally Posted by Cougar View Post
    I agree, it is tempting to imagine an intelligent interloper. A craft 4 football fields long, spinning to simulate a spectrum of gravities, just zooming through, now has abundant information about our system.... But if gathering information was its purpose, it would be beaming that information back to its source, not waiting hundreds of millions of years to deliver it in person. And I don't imagine we see any such transmissions. Oh well.
    Would we see such transmissions if they were a) directed away from us or b) made of waves we cannot detect at all?

    Assuming Oumuamua continues on ballistic cruise for a while and does not initiate any active maneuvers to change its orbit (or rotational period or axis), when would Oumuamua become undetectable for us?
    If Oumuamua suddenly does accelerate, but remains in continuous movement in Solar System, how easy would that be to notice?
    And until when would we be able to detect if Oumuamua has jumped out of lightcone and is no longer present in Solar System?

  21. #51
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    Quote Originally Posted by chornedsnorkack View Post
    Would we see such transmissions if they were a) directed away from us or b) made of waves we cannot detect at all?

    Assuming Oumuamua continues on ballistic cruise for a while and does not initiate any active maneuvers to change its orbit (or rotational period or axis), when would Oumuamua become undetectable for us?
    If Oumuamua suddenly does accelerate, but remains in continuous movement in Solar System, how easy would that be to notice?
    And until when would we be able to detect if Oumuamua has jumped out of lightcone and is no longer present in Solar System?
    An answer to the first question depends on how much telescopic light gathering we can bring to bear on it. The others are unanswerable unless you give us some hypothetical quantitative information.

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    The idea now seems to be that the object is quite dense. This is presumably because high density material would be necessary to hold together such a long, thin object, if it were an asteroid. The spectra taken of it had suggested it was like D and P class asteroids in our solar system. These are calculated to have very low densities, only about 1.4 times that of water.

  23. #53
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    Quote Originally Posted by Ross 54 View Post
    The idea now seems to be that the object is quite dense. This is presumably because high density material would be necessary to hold together such a long, thin object, if it were an asteroid. The spectra taken of it had suggested it was like D and P class asteroids in our solar system. These are calculated to have very low densities, only about 1.4 times that of water.
    Like an intergalactic spaceship

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    Quote Originally Posted by chornedsnorkack View Post
    Would we see such transmissions if they were a) directed away from us or b) made of waves we cannot detect at all?

    Assuming Oumuamua continues on ballistic cruise for a while and does not initiate any active maneuvers to change its orbit (or rotational period or axis), when would Oumuamua become undetectable for us?
    If Oumuamua suddenly does accelerate, but remains in continuous movement in Solar System, how easy would that be to notice?
    And until when would we be able to detect if Oumuamua has jumped out of lightcone and is no longer present in Solar System?
    ʻOumuamua. The ʻokina is a consonant and part of the name (perhaps this should be an entry in the "trivial things that bug me" thread).

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    Quote Originally Posted by chornedsnorkack View Post
    Would we see such transmissions if they were a) directed away from us or b) made of waves we cannot detect at all?
    I think you answered (b) yourself - if we can't detect something, then we can't detect it.

    As far as (a), it would depend on how far from our line-of-sight, how tight the beam was, is it a wavelength we are even listening to, and what the strength of the non-direct (scattered beam) was.
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  26. #56
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    Quote Originally Posted by selvaarchi View Post
    Like an intergalactic spaceship
    Wouldn't a star ship have a relatively low density because it's mostly hollow? See: typical large cruise ship. Lots of volume, not much mass.

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    Quote Originally Posted by schlaugh View Post
    Wouldn't a star ship have a relatively low density because it's mostly hollow? See: typical large cruise ship. Lots of volume, not much mass.
    Not if it is a robotic probe and is packed with instruments to gather information during its intergalactic journey.

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    We cannot, in principle, confirm or deny its presence on its orbit before the earliest found precovery images, on 14th of October, 5 days before discovery. Correct?

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    Quote Originally Posted by chornedsnorkack View Post
    We cannot, in principle, confirm or deny its presence on its orbit before the earliest found precovery images, on 14th of October, 5 days before discovery. Correct?
    Well, we can extrapolate. It would most likely be where Newtonian gravitation suggests. I suppose there are many less likely scenarios that would place it somewhere else.
    Everyone is entitled to his own opinion, but not his own facts.

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    The gaps in our coverage also include:

    The conspicuously weird lightcurve may be expected to change as the directions Oumuamua to Sun and to Earth relative to rotation axis change. However, we cannot analyze the part of lightcurve before discovery - too few observations

    Also, we know that Oumuamua has had no coma since discovery. But if it followed a ballistic trajectory, it passed within 0,25 AU of Earth. Could Oumuamua have emitted a small puff of coma which was gone by the time it was discovered at 1 AU and already cooling?

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