The Tech Times article NASA Fails To Spot Whale-Sized Asteroid That Skimmed Past Earth says that Asteroid 2017 VL2 passed the Earth within about 120,000 km, or about 1/3 the distance of the Moon on November 9 (2017) but wasn't spotted until November 10 by Mauna Loa observatory in Hawaii. It is estimated to be about 16 to 32 meters in diameter.

Is this below the threshold where there is good data on NEOs that may impact Earth, or in fact is there not yet good data on that?

How safe are we? More specifically, is there in fact little data on potential NEOs in this size range (~30 meters)?

Slight irony in the timing - see the BBC's Asteroid close approach to test warning systems where the similarly sized and well documented 2012 TC4 which passed the Earth two months ago.

As an aside, the much larger 3200 Phaethon will pass much farther from the Earth next week, and is expected to produce excellent radar imaging. See also (Sky and Telescope and Astronomy Now).

AsteroidDay.org shorts:


below: from here.

enter image description here

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    $\begingroup$ Whale sized doesn't sound that big, yet according to the article it could wipe out NYC. I haven't seen the science behind that figure. $\endgroup$ – GdD Dec 11 '17 at 13:36
  • $\begingroup$ @GdD ya, what it lacks in $m$ it makes up for in $v^2$. $\endgroup$ – uhoh Dec 11 '17 at 15:30

There are estimated to be around 1 million Near Earth Objects (NEOs) of around in the same size as 2017 VL2, of which around 1% are known (see Rusty's Planetary Defense 6-part series).

It's only much larger asteroids which are better tracked: we're estimated to know well over 90% of the NEOs larger than 1 km, and are aiming to get up to 90% of the 140 m+ ones over the next few years.

As to how we missed it, remember that in the weeks leading up to 9th November it was roughly in the direction of the Sun (as can be seen from the animated gif in the question), so impossible to see against the daytime sky.

  • $\begingroup$ Thanks for your answer! It sounds like it's not really a case of one slipping through the defenses, but that there really isn't the capability yet to routinely spot these small ones. As far as "remember that... it was roughly in the direction of the Sun", it would be great if you could find a link to where that information comes from. $\endgroup$ – uhoh Dec 10 '17 at 1:17
  • $\begingroup$ @uhoh You can see that it's on the Sunward side of the Earth in the video you posted, with conjunction in late Aug / early September. $\endgroup$ – djr Dec 10 '17 at 12:35
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    $\begingroup$ The animated gif in your question. I'm just eyeballing the Sun-Earth-NEO angle. $\endgroup$ – djr Dec 10 '17 at 12:48

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