The World Didn’t End

Asteroid Flys By, Earth is Still Here

This image of Asteroid 2011 MD was shot by Marco Langbroek five hours before the closest approach, using a "remote" telescope, the 0.61-meter F/10 Cassegrain of Sierra Stars Observatory (G68) in California. The CCD image is a 30-second exposure. The fast moving asteroid has tracked a clear bright trail on the image during these 30 seconds. Field center is approximately RA 15h35m57s, dec. +19.441 degrees. Image from 08:32:00 to 08:32:30 UTC (June 27th 2011).

While you were doing your daily thing a little while ago, a little chunk of rock flew by our planet at a distance of 12,000 kilometers (7,500 miles).  It was Asteroid 2011 MD, an Earth-grazing object that is about ten meters (about 30 feet) wide and tumbling through space on its way over our atmosphere and through our flock of artificial satellites.

As NASA scientists predicted, the rock didn’t pose any danger to the planet. But, this is yet another reminder that we live in a solar system populated with stuff that also orbits the Sun, stuff that we don’t always see until the last minute. And, every so often, we do spot something that comes uncomfortably close to our planet. This is perfectly normal in solar system asteroid populations and their orbital dynamics, and is usually nothing to worry about. Until it is.

So far, we’ve been lucky, but let’s put this into perspective. The last really huge bash into our planet made life miserable for the dinosaurs some 65 million years ago, but it wasn’t made by a ten-meter-wide rock. That object was more like 10 kilometers (16 miles) across. Meteor Crater in Arizona was dug out by something about 50 meters (about 150 feet) across, and that impact probably made life miserable for whatever animals (woolly mammoths, maybe) that happened to be ranging around that formerly grassy and temperate plain on that fateful day some 50,000 years ago.

A lot has been made about the fact that we need some sort of “asteroid early warning system” to keep us apprised of such close flybys. We seem to have one now, since this one was discovered on June 22, 2011. But, I think what the community really wants is better detectors to find these things earlier. The little rocks,which are harder to spot, aren’t quite so much a danger as the big rocks — which we should be able to spot sooner than a few days before they get close enough.

What should we do with that information? Just what we do now. We note the approach, the speed at which the object is traveling, and its size and rotation rate, and astronomers around the world (both amateur and professional) arrange to get images of the thing. In fact, for this one, images and movies are already starting to stream in to places like More will show up as astronomers track its passage.

What if a newly discovered rock is bigger than these little guys, and headed straight for us? Well, that’s the scenario that worries scientists and makes the press salivate and write about each asteroid as if it were “the” one. Such a press frenzy for every little rock chunk  is not scientific, but it does sell click-throughs and page views. Believe me, if the big one were on the way, it’d be hard to keep scientists quiet about it, and I can just imagine the über-frenzy the press would lapse into.

Not only would scientists want to study it all the way in (I mean, come on — the opportunity to study an asteroid both visually and spectroscopically as it plunges through our atmosphere is at once an interesting scientific study and a sociological phenomenon), but every politico, evangelist, and wannabe commentator would have their own take on what it “means”. I don’t know about you, but I’d far rather see rational scientific discussion rather than uninformed ranting… but perhaps I’m damning the pundits unfairly ahead of time.


In the meantime, we should embrace the science that’s being done on the little guys that rush past. Each one tells us a bit more about our near-Earth orbital environment, and sometimes we even learn more about the kinds of debris chunks that flash past in the night.

What’s That Bright Thing Out There?

A Star?  A Planet?  What?

Back when I used to work at the planetarium, we’d get phone calls from people — or they’d walk up to the console after a star talk and show — asking about a bright object they saw in the sky one night. Usually, the “thing” turned out to be a planet (if it wasn’t moving during the course of several minutes), or if it wasn’t that — then we’d have a chat about airplanes, helicopters, etc.  They never got confused by the Moon, although there were always questions about things they thought they saw ON the Moon’s surface whilst gazing through binoculars or a telescope.

This was in the days before the International Space Station, but there were still plenty of other satellites — “space birds” — to be seen, and we’d talk about those, too, because people would see them and wonder “Just what is THAT?” Nowadays, we can go online and find a whole listing of space bird sighting opportunities, plus predictions for ISS passes, and using that information, be ready to spot something besides a planet, high-flying jet, or flock of birds.

The view of Spica and Saturn to the west-southwest around 10 p.m. from latitude 40 degrees northin late June, 2011. Click to embiggen. Done using Stellarium.

People are always surprised when I tell them that they can see the ISS from their backyards. No doubt many people HAVE seen ISS and didn’t know that’s what they were looking at.  There’s something pretty cool about stepping outside at the right time (and you can find out when and where in the sky it will next appear over YOUR house by going to’s “Flybys” page and plugging in your zip code (if you’re in the U.S. or Canada), or here at

For folks in the northern hemisphere, these summery nights are great times to get out and check out the stars and planets (and flyover spacecraft). Actually, southern hemisphere viewers should bundle up warmly (if it’s cold in the evenings in your locale), and check out the sky, too.

I’ve given you some links to check out possible ISS and satellite passes, and if you need a star chart, check out the website at or go here to for either a northern or southern hemisphere star chart).  These nights, Saturn is in the west-southwest after sunset.  That’s definitely a planet. It’s not far from the bright star Spica, and if you look at it through binoculars, you should be able to make out the star Porrima, right next to it.

There’s a lot of stuff out there to find in the sky. Sometimes it’s natural… sometimes it’s a human construct passing by. Whatever it is, get out there and check it out!  The skies provide free entertainment and have for as long as people have been looking up!