Raise Your Hand if You Think Space is Pristine

It’s Not

We all carry around in our heads this vision of interplanetary space as dark, cold,  lonely, devoid of stuff.  Well, it is. Except for all those planets, moons, rings, comets, and asteroids.  And dust.  And charged particles from the solar wind. Other than all that material, yeah, the space around the planets looks empty. But, it’s not.  Don’t be fooled.  Our solar system is full of stuff and we’re learning more about it all the time.

Some of the “stuff in empty space” comes close to Earth pretty often. There’s nothing mysterious about that.  There are many asteroids orbiting in the solar system, some far away, others in Earth’s neighborhood. It’s no surprise that astronomers spot wandering chunks of rock that sometimes come close to Earth.  Now that we have more cameras looking for such material — cameras and instruments that are sensitive to the faint light these things reflect — we are spotting more of them.  It doesn’t mean there’s MORE of that stuff out there all of a sudden. It’s always been there.  We just haven’t always had the instrumentation to find it.  Now we do, and the sudden prevalence of near-Earth asteroid discoveries simply means that now that we can spot those objects, we ARE spotting them.

Asteroid 2010 ST3 (circled in green) taken by PS1 on the night of September 16 moving against the background field of stars and galaxies. Each image is about 100 arc seconds across. Credit: PS1SC

The University of Hawai’i’s Pan-STARRS PS1 telescope just discovered an orbiting chunk of rock that will come within 4 million miles of our planet in mid-October.  It’s not a huge chunk — not planet-sized or even moon-sized. It’s about 150 feet across — enough to make a prominent entry into our atmosphere. It’s likely it would break up in the atmosphere, but there would still be a blast wave on the surface that would devastate several hundred miles of territory.

Now, this object, called 2010 ST3 is NOT going to enter our atmosphere on this pass.  But, it could (and I stress the word “COULD” because there ARE people who will take this as a sign of the impending apocalypse and start raising all kinds of irrelevant points no matter how carefully one points out that “could” and “will” are not semantically equal) hit Earth in 2098 and cause damage. But, it’s not going to hit this time, even though it is potentially hazardous. It’s one of many, many chunks of solar system that are orbiting out there, part of the system of solar system objects that astronomers are still learning about, counting, charting, categorizing, and warning us about.  Learning about objects like 2010 ST3 is part of planetary science and part of the exploration of our solar system.


  1. It seems to be surprisingly difficult psychologically for people not to feel that if we suddenly know more about a risk, the risk has suddenly increased. And it’s startling how easily “There’s a 99.99% chance this will miss the earth” (say) becomes “This may hit the earth” and is heard as “This will hit the earth”.

    I wish all journalists reporting on statistics or science were required to have at least a basic science qualification and understanding of statistics . . .

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