Calculating Bennu’s future

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In order to better constrain Bennu’s future fly-bys of the Earth, including the possibility that it could impact the planet, scientists will be using the data sent from OSIRIS-REx to better understand its orbit, its composition, its surface make-up, and its thermal properties, all factors that can influence its future path in space.

This is really important, as Bennu has a good chance of hitting the Earth in the future.

About a third of a mile, or half a kilometer, wide, Bennu is large enough to reach Earth’s surface; many smaller space objects, in contrast, burn up in our atmosphere. If it impacted Earth, Bennu would cause widespread damage. Asteroid experts at the Center for Near-Earth Object Studies (CNEOS) at NASA’s Jet Propulsion Laboratory in Pasadena, California, project that Bennu will come close enough to Earth over the next century to pose a 1 in 2,700 chance of impacting it between 2175 and 2196. Put another way, those odds mean there is a 99.963 percent chance the asteroid will miss the Earth. Even so, astronomers want to know exactly where Bennu is located at all times.

The article provides a good overview of the difficulty of properly calculating Bennu’s orbit into the future, and how the data from OSIRIS-REx will help make those calculations more precise.



  • Orion314

    Reminds me of the old astronomers’ joke , who , one night , after his presentation to the locals was asked by a nervous and worried lady “How long did you say our sun will last?” to which he replied ‘ Oh about 10 billion years or so.”
    The lady let out a big sigh of relief and replied ” Thank GOODNESS ! I thought you said 10 million years”

  • mpthompson

    If a transponder were placed by a spacecraft onto Bennu, could that help scientist determine the current position and future orbits with greater precision? The article states that the scientist can currently track Bennu’s position at any given time down to a few kilometers. That doesn’t sound terribly precise considering how sensitive future orbital predictions depend on the exact path during close encounters with other large bodies such as the Earth and the Moon.

    Perhaps we need some sort of GPS-like system that spans the inner solar system with solar powered transponders that can last for centuries to tag Earth-crossing asteroids with.

  • Chris

    MPThompson – I delayed and you beat me to the punch.
    Can OSIRIS-REx be that transponder by parking it in an orbit close to Bennu? Ie make it a permanent hitchhiker in the Bennu gravity? Or is that gravity too weak.

  • Edward

    I am surprised that the article detailed the Yarkovsky effect. This may be the first article that I have seen that even mentioned it.

    mpthompson (and Chris) asked: “If a transponder were placed by a spacecraft onto Bennu, could that help scientist determine the current position and future orbits with greater precision?

    From the article:

    The OSIRIS-REx spacecraft will use its suite of instruments to transmit radio tracking signals and capture optical images of Bennu that will help NASA scientists determine its precise position in the solar system and its exact orbital path. Combined with existing, ground-based observations, the space measurements will help clarify how Bennu’s orbit is changing over time. … After the OSIRIS-REx mission, Chesley said, NASA’s trajectory projections for Bennu will be about 60 times better than they are now

    One problem that astronomers may be having is that Bennu is probably smaller than their telescope’s pixels, making it difficult to be sure where it really is in any given measurement.

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