This visitor from beyond our solar system will be probed for signs of life

Dec 15, 2017

By Ben Guarino

Our solar system has a visitor. It’s cylindrical, dark and reddish, a quarter-mile long. The object won’t be staying. This fall, astronomers announced that the thing came blazing into our neck of the galaxy at speeds of up to 196,000 mph. It is now headed away as quickly as it came.

The object’s trajectory is so strange and its speeds are so blistering that it probably did not originate from within our solar system. Its discoverers concluded that the object is a rare interstellar traveler from beyond our solar system, the first object of its kind observed by humans.

Astronomers at the University of Hawaii, who discovered the object with the Pan-STARRS 1 telescope, said the visitor was an asteroid. In October, they named the asteroid ‘Oumuamua — Hawaiian for “messenger.” ‘Oumuamua, which appears rocky or metallic, lacks the characteristics of a comet.

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7 comments on “This visitor from beyond our solar system will be probed for signs of life

  • @OP – This visitor from beyond our solar system will be probed for signs of life

    I think the suggestions of “signs of life” or “signs of alien technology”, are wild wish-thinking speculation.

    This is a rocky metallic asteroid from outside the Solar System, without even any signs of water!

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  • The mainstream media reporting on this is typically hyped up and inaccurate as with most science reporting. That “picture credit” at the top of this page is actually an artist’s fantasy impression because no one actually has a clue what this thing looks like in any detail. It was always too small and too far away for any of our telescopes to resolve as more than a faint dot of light. How we actually surmise it’s very elongated is only from its brightness (or light curve) which changes as it tumbles, diminishing when it’s head on to us and increasing when it’s sideways on. The amount of that change gives an indication of how non-spherical the object is but only an indication. Everything else in that artist’s impression is complete guesswork. Its colour spectrum gives an indication it’s reddish brown which is typical of other rocky metallic asteroids but other than that we know very little.

    The bit about its speed is vaguely correct but still not really. As it got closer to our solar system the sun’s gravity pulled it in and sped it up to over three times its arrival velocity. As it leaves us it will give back that extra speed and return to its interstellar norm of about 59,000 mph. Still over twice as fast as our best spacecraft but not quite what the article suggests. It would take it nearly 50,000 years just to get to our nearest stellar neighbour although it’s not heading out in that direction. It could actually have been travelling for millions or even billions of years already from wherever it originated from. As an absolute minimum it’s been travelling for hundreds of thousands of years because there are no star systems in the direction it arrived from that are closer than that. If it’s a spaceship (which it isn’t!) then the occupants are definitely looking a bit worse for wear by now.

    What I think is interesting about this is not the fancy painting and the hyperbole about what it might be but the details of how astronomers glean so much information about something they can actually barely see. The same techniques apply to all distant astronomical observations. For example we can’t directly see anything so small as a planet orbiting even our nearest stars but the light curve of the star itself tells us if anything passes in front of it and obscures a bit of it for a while. Spectra in both visible and non-visible frequency bands let us deduce what elements an object is made from and light curves give information about rotation and shape. Computers now process this information massively faster than people can do and sophisticated computer algorithms including self learning ones enable things to be spotted that no human could do even from the same raw data. In fact year on year we can go back to examine objects that have already been extensively studied and still glean more about them without actually needing more powerful telescopes. The computers pick up on otherwise hidden patterns in the data and information pops out.

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  • Arkrid Sandwich #2
    Dec 15, 2017 at 7:35 pm

    I put a comment and this link to an article about this extraterrestrial object on the “We just sent a message to try to talk to aliens on another world” – Nov 16, 2017 thread, but the mods are discouraging cross thread links, so you will have google it or look down the RDFS News index page, if you want to look at the related extraterrestrial comments.

    “Looking at the asteroid light curve database, there are five objects (out of 20,000) that have light curves that would suggest a shape up to an axis ratio of about 7-8 to 1,” Dr Meech told BBC News.

    “Our errors are very small, so we are confident this is really elongated. Also, one has to realise we don’t know where the rotation pole is pointed. We assumed that it was perpendicular to the line of sight. If it were tipped over at all, then there are projection effects and the 10:1 is a minimum. It could be more elongated!”

    “We also found that it had a reddish colour, similar to objects in the outer Solar System, and confirmed that it is completely inert, without the faintest hint of dust around it,” Dr Meech said.

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  • Thanks Alan, I had a look at the other thread. There’s actually some talk about trying to send a probe after this object to get a closer look.

    Of course it’s not quite so easy to catch and study such a fast moving object as it looks in sci fi movies. To build up enough speed to chase down Oumuamua a probe would have to do a loop round the sun and Jupiter to take advantage of their gravity wells to boost speed and also burn all its fuel at the optimum point to add the most kinetic energy. Then hopefully if the calculations are right it sets off in pursuit at anywhere between 1.5 and 2.5 times the asteroid’s velocity but with no way to alter course or speed much except perhaps for a tweak to direction with any last fuel saved. So if the probe does manage to catch up it will also shoot on past with no way of slowing for a longer look. The best that could be hoped for would be some good photos, measurements with whatever instruments are on board and maybe a laser shot to evaporate a bit of the asteroid’s surface and see what it’s made off from the spectrum.

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  • Arkrid Sandwich #5
    Dec 16, 2017 at 6:26 am

    Of course it’s not quite so easy to catch and study such a fast moving object as it looks in sci fi movies.

    In the Non-specialist media, there is a general lack of understanding of the time required to plan and construct space projects, the scale of planetary systems, the velocities of orbits, or the methods of determining the shape of distant objects.

    The New Horizons Spacecraft was launched in 2006.

    After its astonishing flyby of Pluto in 2015, scientists have just discovered that the probe’s next target is not one object but very likely two.

    Earth-based observations suggest the small icy world, referred to simply as MU69, has a moonlet.

    It seems New Horizons will now be making a two-for-the price-of-one flyby when it has its encounter on New Year’s Eve and New Year’s Day, 2019.

    The plan is for the spacecraft to pass the 30-40km-wide main object with a separation of just 3,500km, acquiring high-resolution pictures and other data.

    This should reveal new information on the Kuiper Belt – the band of distant, frozen material that orbits far from the Sun. On flyby day, New Horizons and MU69 will be some 6.5 billion km (4.5 billion miles) from Earth.

    “Besides being the farthest exploration in the history of humankind, this flyby is also going to the most primitive and pristine object ever explored,” said Prof Alan Stern, the principal investigator on New Horizons.

    There are some pictures and discussions on the various shapes of asteroids on the link.

    To build up enough speed to chase down Oumuamua a probe would have to do a loop round the sun and Jupiter to take advantage of their gravity wells to boost speed and also burn all its fuel at the optimum point to add the most kinetic energy.

    I can’t take seriously a plan to put resources into a probe to an individual small rocky object, which appears to have been inactive and “dead” for millennia or a lot longer!

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  • As I said above, the takeaway for me in all this is how astronomers deduce things about celestial objects by measuring what you might at first think is something completely different. We can’t directly tell how big this object is or what shape it is but we deduce from its brightness and light curve (its varying brightness). Two of the quantities that can be very difficult to measure for distant objects are mass and distance. I’ll look at mass briefly.

    There’s no direct way of viewing something distant and telling what its mass is. Even if we know its size fairly accurately that doesn’t mean we know its density. Knowing density can give good clues to what something is made from so we need to know mass as well as size.

    For objects that have something else in orbit round them the law of gravity tells us what we need to know. An object creates a gravitational field that depends on its mass and that creates a force of attraction with any other object with mass. A stable orbit is defined as when the notional centrifugal force generated by the orbiting object’s speed exactly balances the gravitational attraction trying to pull it towards what it’s orbiting round. The bigger the gravitational pull of a planet the faster any moon needs to orbit at a given distance. If we can measure the speed and distance of the moon we can calculate the mass of the planet. What we can’t do is calculate the mass of the moon unless it’s large enough to measureably affect the motion of the planet. All objects orbit at the same speed at a given distance regardless of their size just as all objects fall at the same rate in a vacuum regardless of their size.

    This technique which comes from a combination of Newton’s Laws of Gravity and Kepler’s Laws of Planetary Motion works for stars and planets, planets and moons, black holes and stars and even binary stars – basically anything with something else going round it. It allowed early astronomers to accurately calculate the mass of the sun and all the planets in our solar system except for Mercury and Venus which have no moons. It wasn’t until we could send probes to them and see how fast they orbited that we could accurately work out the masses of those two planets.

    For stars which are too distant to detect any orbiting planets we have a problem. Even if we can directly see how large the star is we can’t assume its density is the same as any other star. A novel technique is helping overcome that though. It has been discovered that the light from stars has a characteristic flicker which is proportional to the gravitational field at the star’s surface. As the photons exit this field they are slightly affected by it. The strength of the gravitational field is a function of the mass and diameter so if we have already managed to work out the star’s size we can calculate its mass from the light flicker and hence its density.

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