Another newly discovered LARGE NEO

[beskeptical]

Quite a while back someone posted they believed all the really large NEOs had been found and the new discoveries were all small. I saw a new NEO listed not too long ago that was over a kilometer wide and thought of the post but couldn't remember who had said it. Now here's another new discovery of an NEO greater than a kilometer wide.

2009 MC9, first observed 06/30/09, size: 1.2km.

We are not yet safe from impacts that could sneak up on us.

[01101001]

Quite a while back someone posted they believed all the really large NEOs had been found and the new discoveries were all small.

Back in 2003 we turned the corner.

Spaceref.com: NEO News: Spaceguard Progress (May 2004)

[...] there are estimated to be a total of 1100 +/- 100 NEAs larger than 1 km. Thus at the end of 2003 we had found 63 percent of these NEAs.

Recently there appears to have been a modest slow-down in the discovery rate of NEAs larger than 1 km, perhaps reflecting the fact that we have already discovered nearly 2/3 of this population group. For the most recent three complete years (2001, 2002, and 2003), the numbers discovered are: 89, 95, and 67, respectively.

I wonder what the rates are now. I'd expect that in the intervening years the rates have continued to drop, but that it will be some time before we conclude the last big one is found.

Edit: Much more recently, 90% are estimated found.

Planetary Society Blog: Planetary Defense Conference: Interesting Tidbits (April 30, 2009)

Scientists think about 90% of NEOs larger than 1 km have been discovered now. A NEO of this size would cause regional or global disaster if it impacted. Consistent with finding 90%, the discovery rate of these large NEOs has actually dropped in the last few years as there are fewer and fewer to discover. Of the 6000 NEOs, about 80 are comets.

Oh. NEOs. If we're counting NEOs (and not NEAs as I was thinking) then it will be a very long time until we find the last one.

[beskeptical]

Objects as opposed to asteroids? Are you thinking because asteroids are all on shorter orbital periods while comets can come in from so far away?

The subject came up originally when I said something about how many newly discovered objects were still being found. Since then I've been checking fairly regularly. I may have missed some but it seems I recall only 2 new discoveries in the past year that were > 1km. But I think that is more than enough to make a potential impact from an object we have little or even no warning about still a considerable risk. I'm less worried about a long orbit comet because we'd more than likely see it coming a long way out.

[01101001]

I'm less worried about a long orbit comet because we'd more than likely see it coming a long way out.

I prefer to worry more about the comets.

Hayden Planetarium: from From Natural History Magazine, September 1997 by Neil deGrasse-Tyson

In this game of gravity, by far the most dangerous breed of impactor is the long-period comet, which, by convention, are those with periods greater than two hundred years. Representing about one fourth of Earth's total risk of impacts, they fall toward the inner solar system from great distances and achieve speeds in excess of 100,000 miles per hour by the time they reach Earth. Long-period comets thus achieve a much higher impact energy for their size than your run-of-the-mill asteroid. More importantly, they are too dim over most of their orbit to be reliably tracked. By the time a long-period comet is discovered to be heading our way, we might have anywhere from several months to two years to fund, design, build, launch, and intercept it. For example, in 1996, comet Hyakutake was discovered only four months before its closest approach to the Sun because its orbit was tipped strongly out of the plane of our solar system and nobody was looking. While en route, it came within 10 million miles of Earth (a narrow miss) and made for spectacular nighttime viewing.

Booga-booga!