17 thoughts on “A Minimoon”

  3. Can someone explain to me how an object that orbits the sun can have a different year than Earth, but never be further than .3 AU away from Earth?

    1. The asteroid interacts with the gravity fields of the Sun, Earth, and Moon strongly. It is in orbit around the Sun almost exactly in phase with the Earth, and at almost exactly the same distance as the Earth, but out of the plane of the Earth’s orbit. Its interaction with the gravity fields in the Earth/Moon gravity well keep 2016 HO3 from moving more than a certain distance away, and from moving less than a smaller distance away. Thus, when looked at from Earth, it *seems* to orbit the Earth/Moon gravity well in a plane almost 90 degrees from the plane of the Earth’s orbit around the Sun, though the Earth/Moon gravity well alone would not be strong enough to hold 2016 HO3.

  4. Think of it as an object orbiting the Sun in close enough company to the Earth that it effectively spirals around the Earth in the process. Earth’s gravity is undoubtedly altering its orbit all the time. Hence the slight difference in “year” lengths? Probably a varying rather than stable difference.

    Between 36 and 91 meters wide? That’s a useful amount of mass. And likely not a lot of delta V to get there. Could we see a race to get a probe there?

    1. Without relativity, its years have to average out to ours or it has to be on the other side of the sun sometimes.

    2. I would hope that both Deep Space Industries and Planetary Resources have some interest in 2016 HO3. I have only heard 2 comments about its compositions, and one of them denigrated its present usefulness because it was so close to Earth’s orbit that it supposedly could not contain much water, the first salable resource that PR and DSI mention. I wonder whether that is correct beyond the very surface layers of the body, myself. The other comment mentioned, without giving calculations, that it could be possible to get to 2016 HO3 and back in 5 months. If so, it would have substantially better attractiveness to most VC investors than would a body like Bennu, a CC asteroid, which has an 8 years long mission to it under way with a sample return included.

      Bennu has the certainty of getting ice back and other scientific samples, but in a timeframe leaving from Earth that makes it of academic interest only. 2016 HO3 may have a flight timeframe that could be of industrial interest, but may not have the scientific payoff of an essentially unmodified early solar system object that will have interest for scientists.

  7. There always seem to be things popping up that we never knew were there and yet we tend to be very certain about what is out there.

  8. I thought we had mini-moons coming and going all the time?

    The article doesn’t mention how long its earth orbit is?

    It seems just the right size to hollow out and add a thrust engine to it?

    Perhaps as Buzz Aldrin’s cycler?

    1. “I thought we had mini-moons coming and going all the time?”

      We do. They are usually at most 7m or so in diameter. The estimates I have seen indicate they might mass as much as 300 tons total most of the time.

      Their estimated average lifetime in orbit through the Earth/Moon gravity well is about 10 months, on *very* strange “fuzzy” orbits. The reason this “quasi-moon” has a longer lifetime is that its primary is actually the Sun, not the Earth/Moon gravity well.

      1. Well we wanted rock, and we skip the part of hauling one back to Earth Moon L-point.
        Actually this rock seems to be in a Earth/Sun/Moon L-point- or “higher orbit” of L-point and one might move to closer L-points.
        But “larger than 36.5 meters across, but no more than 91 meters wide”
        is getting in range of being a dangerous impactor, so moving it “incorrectly” has a liability aspect.

        Now how to get to it? It seems like it take long time or use more delta-v and get there faster. It’s basically 10 times further than Earth/Sub L 1 or 2. And a lot closer than Earth/Sun L 4/5.
        60 degrees or 1/6th Earth orbital circumference: 157 million km- about 1/4 distance to L-4/5.
        So other time factor, it’s less delta-v than low lunar orbit- yes?

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