Big Think Interview With Edward Sion | Big Think

Big Think Interview With Edward Sion

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A conversation with the astronomer and astrophysicist at Villanova University.

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Edward M. Sion:

Edward M. Sion is a Professor of Astronomy and Astrophysics at Villanova University. He received a B.A. in Astronomy from the University of Kansas in 1968, an M.A. in Astronomy from the University of Kansas in 1969, and a PhD in Astronomy from the University of Pennsylvania in 1975. His primary research interests include the formation and evolution of white dwarf stars, the physics and evolution of cataclysmic variable stars, and theoretical studies of accretion physics.

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TRANSCRIPT:

Ed Sion: Edward Sion, Professor of Astronomy and Astrophysics at Villanova University.

Question: What hazards exist in outer space that could pose a grave threat to Earth?

Ed Sion: Well one of the scenarios is the one regarding what our press release was about, concerning T Pyxidis. But I think that most scenarios now, for example, trying to account for the mass extinctions that have occurred throughout geological history that the, for example, the gamma ray burst. A burst of gamma rays from a very massive star that collapses on itself with a prompt formation of a black hole, and then with gamma ray jets that, if they’re oriented just right, the gamma ray burst will be directed at Earth. These could be potentially devastating, the gamma ray bursts.

In addition to that, there is a lot of debris in our solar system that was part of the fundamental building blocks of the solar system. Primordial matter is what we call it. Pristine chemical composition. There’s been no chemical alteration. The comets are good examples of that. And some of the asteroids are pretty primitive, that is they have a composition that is very pristine and primordial. It has been altered by geological evolution. That is, they haven’t been incorporated in large bodies that undergo geological evolution. So, these are the basic building blocks. Well, these building blocks, they’re out there and of course they can potentially collide with the planets, including Earth. And in fact this is how we think the moon originated.

The most widely held theory for the origin of the moon is the giant impacter theory where billions of years ago, after Earth had developed an iron core, after it had what we call it differentiation, where the heavy elements sink to the center of a newly formed planet and the lighter elements float to the surface because of their different density, that Earth once it differentiated early in the history of the solar system when collisions with other bodies was more frequent, earth was struck by a Mars-sized intruder body. That then liquefied a large portion of the Earth’s mantel at the collision site and ejected this liquid rock out into space. This liquid rock then cooled and solidified and then reassembled itself by gravity and that’s what we have now, according to this theory as the present day moon. It eventually then suffered other collisions, the moon suffered other collisions. That gives us the Man in the Moon appearance. The lunar seas, for example, those blue patches are actually gigantic impact basins that have been flooded with lava, with liquid rock during lunar volcanism, during volcanic activity in lunar history.

So, these collisions happened much more frequently in the past, but that doesn’t rule out that they can’t happen now. So, I think it’s an area that is really deserving of a lot of exploration as is being done now.

Question: How do you rate the danger of an asteroid or comet impact happening within our lifetimes?

Ed Sion: Well, within the human lifespan, it’s a very, very low probability. But on the other hand, one cannot rule it out. There are three families of asteroids that actually have the potential of colliding with Earth, the Amore Asteroids, the Apollo Asteroids, and the Aten Asteroids.

The Apollo Asteroids actually have orbits that are internal to Earth’s orbit and they’re perhaps the most likely, the Apollo Asteroids. And they are being monitored very carefully by telescopic patrol observatories that have been set up. And if one of the Apollo Asteroids were to enter into collision course with Earth, hopefully we’d have enough warning, but we do in fact have the technology now and in the future to intercept and possibly deflect such a body.

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