Category Archives: asteroid

asteroid, astronomy

Raise Your Hand if You Think Space is Pristine

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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.

asteroid, comet, impact site, impacts, NASA, near-earth asteroids, NEOs

Watch Out!

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Things that Go Bump in the Solar System

Jupiter got whacked last week, as most of you probably know. One question that I saw reiterated across many blogs and boards (mostly by people who have no idea how astronomy observations work) was along the lines of “Why didn’t the astronomers with all those big telescopes see this coming?”

As in so many areas of life, I have to respond that “it’s not the size that matters, it’s what you do with it.”  A big telescope all by itself doesn’t help you routinely find stuff getting ready to blast into Jupiter (or other planets).  In fact, a small one by itself won’t do it either — no matter how big the impactor is.  Both have to be pointed properly at the right place and right time, and they have to be able to “see” the objects.  If the object is too small — as the impactor at Jupiter was — you won’t have a chance of seeing it (from Earth, anyway) no matter how big your telescope is.  Each telescope and its instruments have limits to their resolution (essentially the size of objects they can detect — if something’s too small to detect, a given system just won’t be able to “see” it). Also, there’s the whole issue of scheduling — the big telescopes and the smaller ones operated by dedicated amateurs usually are taken up well in advance with planned observations. That’s not to say that they can’t be pointed at something once we find out about it — that’s called a “target of opportunity” and most facilities have allowances for such events in their schedules.  The catch is — you can’t observe the object or even until you know about it — or, if it’s big enough for you to see — until it wanders across your field of view as you’re studying something else. That’s just common sense.

Many comets and asteroids and asteroid debris that make up the “impactor class” are found by people and instruments who routinely scan the sky looking for such things. But, there’s a limit to how much sky one can scan each night, and observers are limited to the skies they can see from their sites. If there’s a comet beyond the horizon — well, it doesn’t get discovered that night by the observers who can’t see it.  Eventually the larger objects are found and observed over enough time that astronomers can calculate their distances and orbits. These are things that are larger than a kilometer or so in radius.

What about the small stuff? Well, it’s really, really tough to see, even with (and despite having) a large aperture telescope.  Yes, there are projects like Spacewatch, which explores populations of small objects in the solar system 20 nights per month (roughly), but those are not likely to be able to just look right out there and easily spot things as small as the projectile that bruised Jupiter.

Incoming objects fascinate (and scare) people, even if the chance of an impact on Earth is quite small most of the time. Yet, the big questions always come up: what if something’s headed for Earth? How will we find out about it?  How close will it get? Will we find out too late? What do we do?  Spacewatch and others do keep watch on Earth-approaching objects — if they are large enough to spot. Once something is discovered and charted, its orbit is plotted — which is not a one-time thing — orbits continually change as objects are perturbed by the gravitational influences of the planets they pass near. Also, it takes many observations over a period of time to accurately calculate an orbit — which then gives us a good handle on how close (or even if) it will come to Earth or another world.

With Spacewatch and other observation programs, we do have an early warning system of sorts.  And, if you’re interested in knowing what IS being tracked, there’s a new Web site to help you do that. NASA has just opened Asteroid Watch up for business. It’s a centralized Web resource for information on near-Earth objects. The site also contains links for anyone interested in such objects to sign up for NASA’s new asteroid widget and a Twitter account.  So, go check it out — and learn more about comets and asteroids that are being tracked and studied.