Astronomers find Kuiper Belt-like ring around Proxima Centauri

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Worlds without end: Astronomers have found a dusty ring 1 to 4 astronomical units from the nearest star, Proxima Centauri.

Because Proxima Centauri is a smaller, dimmer star, its system is more compact. Proxima b [the star’s known exoplanet] circles the star at 0.05 astronomical units (a.u., the average distance between Earth and the Sun) — for reference, Mercury orbits the Sun at 0.39 a.u. The dusty ring lies well beyond that, extending from 1 to 4 a.u.

The Proxima ring is similar in some ways to the Kuiper Belt, a cold, dusty belt in the far reaches of our solar system (beyond 40 a.u.) that contains a fraction of Earth’s mass. While the Kuiper belt is well known for larger members such as Pluto and Eris, it also contains fine grains, ground down through collisions over billions of years. The dust ALMA observed around Proxima Centauri is composed of similar small grains. The average temperature and total mass of the Proxima ring is also about the same as our Kuiper Belt.

Because the ring here much closer to the star than our Kuiper Belt, the material is much more densely packed. Moreover, the presence of both a ring and an exoplanet suggests more planets might remain undiscovered there, increasing the chances that this star could have a solar system very worthwhile exploring.



  • Dick Eagleson

    By the time we send people there, extraterrestrial civilization will also be expert at building free-flying rotating habs out of found materials. Knowing in advance that there are materials to be found is all that’s needed to make seeding any nearby extra-Solar star system with people a cinch bet.

  • So much for the Centauri ala Babylon 5.

  • Dick Eagleson


    Not so, it would seem.

    The Centauri always seemed to me like Czarist-era Russians with ray guns and starships and not just because of the accent Peter Jurasik put on for his role of Ambassador Molari.

    Absent an encounter with real-life aliens who speak English with Russian accents, that particular sound seems likely to be all but absent among humans who actually move out from Earth to live in space. Russia, it now seems clear, is in rapid and terminal decline. Excepting, perhaps, its considerable legacy of orbital debris, Russia’s once formidable space presence will be all but gone by mid-century. By the middle of the next century the Russian nation may be gone as well. The Russian culture is founded on being the dominant bully in its neighborhood. That is a role its rapidly declining population can no longer support. As with much else in its history, Russia’s end is not likely to be a good one, whether it be a protracted death by inches or a quick coup de grâce.

  • pzatchok

    I remember reading an article by Asimov in which just this ring was theorized and he proposed using our kuiper belt as a resource stop on our way to Proxima Centauri’s theorized kuiper belt and then on to Proxima Centauri proper or at least a more habital orbit.

    The belts are about at the one third and two third parts of the trip.

    I think it was called “Stepping Stones to the Stars.” I’ll have to find my copy of Asimov on Astronomy.

  • LocalFluff

    There are comets all the way (and obviously dry objects like A/2017 U1 that don’t outgas anything even just 0.2 AU from the Sun). 1/3 the way to the nearest star is the limit of the Sun’s gravitational dominance, because the nearest is Alpha Centauri A and B with together twice the mass of the Sun (the Sun’s Hill sphere is larger in other directions). Beyond that comets are more bound to Centauri.

    Little is known, but a rough estimate of the average distance between objects in the Oort cloud is 0.2 AU. That is the same as the density of the planets and moons in the inner Solar system (7 objects within 1.5 AU). And it seems to be the standard presumption among astronomers today that this continues throughout interstellar space in the galactic disk.

    Interstellar space has gotten more and more full of stuff the more astronomers have looked. I guess that hasn’t peaked yet.

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