A few weeks ago, this asteroid came really close to hitting Earth.On March 3rd, 2009 at 1:40PM GMT, just a mere month after we'd finished the Asteroid Hunters segment, an asteroid of up to 165 feet in diameter snuck up on us, coming within approximately 37,000 miles from a direct impact with Earth. That's almost seven times closer than the distance to the Moon and about twice the distance of some communications satellites that orbit the earth.

Called “2009 DD45”, the asteroid was estimated to be around the same size as the one that exploded in the atmosphere near the Podkamennaya Tunguska River in remote Siberia on June 30th, 1908, flattening 80 million trees across eight hundred square miles of remote forest. Of course, if an asteroid of this size were to hit a city or in an ocean offshore from a populated area, tens of thousands of people would likely die.

Then, just as the last of the night sky observers were completing their collective sighs of relief, on March 17th, 2009 another Tunguska-class asteroid, 2009 FH, passed by about 53,000 miles from Earth. Thankfully, neither of these asteroids actually hit us. But astronomers didn’t even observe 2009 DD45 until 4 days before its closest approach. It's orbit was calculated and it was determined that it would miss the Earth. But it's likely that asteroids of this size are fairly frequently buzzing by the Earth. And until recently, most of them have been undetected.

In 1998, NASA started the Spaceguard Survey which set out to discover 90% of those Near Earth Asteroids (NEAs) 1 km in diameter and larger. An impact by an asteroid this size would likely cause global destruction and an end to much of life as we know it so it’s definitely reassuring that 10 years after its inception, the Spaceguard Survey had found about 80% (CK) of them. But unfortunately, once we’ve found them, there’s still no international concensus or infrastructure in place in how to deflect or destroy them. But the Survey is limited by its mandate to find those mass extinction-sized asteroids as well as by the size and sophistication of the telescopes that are dedicated to searching the skies.

As former Apollo 9 astronaut, Rusty Schweickart said in a recent phone conversation, "in the process of finding the big ones, you also find a bunch of small ones, and the smaller ones are obviously far more numerous than the large ones." But it will take many more resources and new telescopes to continue searching for and tracking the smaller ones. And unfortunately, once we’ve found them, there's still no international consensus or infrastructure in place in how to deflect or destroy them. Raising awareness and building alliances amongst governments and space agencies is Schweikart's current "mission". He founded the B612 Foundation and Association of Space Explorers to tackle these goals on different fronts.

The message that I hope is conveyed with the Asteroid Hunters TV segment is that we are not immune from asteroid impacts here on Earth. Rusty Schweikart puts it best in a portion of his interview that didn’t make it into the final program:

"Well, asteroids and comets are good news and bad news, you know? But for them we wouldn’t be here, and on the other hand, if we don't actually take some action now, at some point we won’t be here anymore, because there's no question that we will be hit by asteroids, and we’ll probably be hit by, we would be hit by comets as well. Unless, we use the technology that we have and the brains that we have in order to protect the Earth from asteroid impacts, and we can do that. We can basically now, with current technology, assure that no asteroid ever hits the Earth again. That can do any serious damage."
-Rusty Schweikart

Here's a little exercise from Rusty that you can do to get a sense of what we know today about exactly what's out there:

• Go to: neo.jpl.nasa.gov/risk
• See two tables, the first table says "Recently Observed Objects" and the table below says "Objects not recently observed." You’ll notice in the bottom table that Apophis is the 4th one listed.
• Click on "Apophis". At the top you see a bunch of boxes, like the diameter at .27 km, or 270 meters.
• Down below that you see 3 lines, those are the 3 potential impacts. The first one is April 13, 2036. Go over to the right on that line you'll see the column "Impact Probability" is 2.3 x 10-5 – click on that. So there is the probability, 1 in 43,000 of that particular impact.
• Now if you go back to the main table you can do the same thing with every single one of those lines.
• Now go to the very top of the page and hit "Discovery Statistics." Scroll down to a blue and red graph "Known Near-Earth Asteroids". This shows the discovery rate beginning back in 1980 going up to almost current time. Notice the knee in that curve in 1998 – that’s when the Spaceguard Survey began.
• Scroll down to table just below the graph and look across that table to the far right side, to see that a a total of 6166 NEOs (of ALL sizes) have been discovered.

Rusty concludes that, "…what we really care about is not only the things that large, we care about things that can hurt us. Things that can hurt us go down to 40 to 45 meters or so. Instead of there being 940 of them, there are more like 600,000 of them. So the new charge for NASA, which they have so far ignored, is to find 90% of the objects 140 meters and larger by 2020. You can't reasonably set a goal to find everything down to 40 meters because it's just beyond the capability of telescopes and the money available. So NASA, working with Congress, set the goal at 140 meters. Now nevertheless, when you are looking for 140 meter objects, it’s going to take bigger telescopes than the ones to find a kilometer. Therefore we are going to find many many smaller objects as well. So 10 to 15 years from now, instead of that number on the far right hand column being 6000, it will be 1 million."

Watch the Asteroid Hunters television story online.

Saturn's moon Epimetheus from the Cassini spacecraft.
Credit: Cassini Imaging Team, SSI, JPL, ESA, NASA
and APOD.

On the bus in Denali National Park a few years ago, I found myself sitting next a couple from the East Bay. If you’ve ever been on the Denali bus, you know that it’s a long ride and it was just a matter of time before we struck up a conversation. As often happens, we wound up talking about work and then about astronomy research. Both of them were very interested in the field but were unsure of where to find good information on the web. At the time, I hadn’t really thought about that and wasn’t much help.

Now that I’m writing for QUEST, I am much better suited to answer them. I spend a lot of time surfing the web for images and links to websites to provide the full details for readers who want to follow up on my posts. Over the course of a year or so, I’ve discovered quite a few resources and have settled on a few favorites. Of course, being a Berkeley and Cornell grad, I have a few biases…

First of all, it is common for a university astronomy department to organize a public outreach campaign. I won’t bother with the obvious disclaimers and instead will just say that two of my favorites are “Ask an Astronomer” at Cornell University and the Berkeley Center for Cosmological Physics.

These two sites are quite different. As the name implies, the Cornell site encourages questions and suggestions from readers. The content of the site is therefore governed by the public, covering a wide variety of topics in fairly brief, straightforward language. The Berkeley site is much more structured. They cover the history of cosmology and outline the history of our universe with all the appropriate links (scroll down to see the links). This provides a very detailed and organized explanation of a specific field of astronomy.

In addition to universities, there are quite a few NASA missions that maintain excellent public relations. Almost everyone knows the Hubble Space Telescope and Mars Rovers. Both sites are updated almost daily with galleries, discoveries, and recent news. NASA also has several other large missions at other wavelengths that are probably not as well known. Three examples are the Chandra X-ray observatory, the WMAP mission, and the Spitzer infrared observatory. Like the Hubble and Rover sites, these space-based observatories perform ground-breaking science and do an excellent job explaining their discoveries to the public.

Besides QUEST, there are also quite a few other excellent blogs out there. Each site has a different approach and finds its own balance between astronomy coverage, opinion, and discussion of general science. One of the most popular is the Bad Astro site–we even have a link on the right hand side of the QUEST blog web page. You can also check out About.com's top ten space and astronomy blogs.

Of course, one obvious place to learn about astronomy is from journalists. Two websites that do a very good job of covering the field are Space.com and New Scientist (some content requires subscription).

Finally, if you enjoy beautiful images of the sky, a great place to look is the “Astronomy Picture of the Day." This is where I got my image for today. If you look tomorrow you’re guaranteed to find something just as exciting!

Kyle S. Dawson is engaged in post-doctorate studies of distant supernovae and development of a proposed space-based telescope at Lawrence Berkeley National Laboratory.

latitude: 37.8768, longitude: -122.251