This Is The Asteroid That Didn’t Hit Us

All right, sure – there are a lot of asteroids that don’t hit us. And of course quite a few that do… Earth is impacted by around 100 tons of space debris every day (although that oft-stated estimate is still being researched.) But on March 10, 2015, a 12–28 meter asteroid dubbed 2015 ET cosmically “just missed us,” zipping past Earth at 0.3 lunar distances – 115,200 kilometers, or 71, 580 miles.*

The video above shows the passage of 2015 ET across the sky on the night of March 11–12, tracked on camera from the Crni Vrh Observatory in Slovenia. It’s a time-lapse video (the time is noted along the bottom) so the effect is really neat to watch the asteroid “racing along” in front of the stars… but then, it was traveling a relative 12.4 km/second!

UPDATE 3/14: As it turns out the object in the video above is not 2015 ET; it is a still-undesignated NEO. (My original source had noted this incorrectly as well.) Regardless, it was an almost equally close pass not 24 hours after 2015 ET’s! Double tap. (ht to Gerald in the comments.) UPDATE #2: The designation for the object above is now 2015 EO6.

The description on the video reads:

The asteroid starts as tiny dot just below the centre of the right image and drifts gradually downwards. Due to a software glitch a correction which was meant to bring it back to the centre was not applied and the asteroid was subsequently lost. Nevertheless, the telescope kept tracking at the rate of the asteroid movement, just to illustrate the effect of sky motion. Towards the end, when the asteroid would be too faint again, the clouds rolled in and the observations were terminated. (Source: YouTube)

This subway-car-sized space rock didn’t impact Earth (obviously) on this trip around the Sun and won’t on any of its more distant passes during its 2.9-year orbit in the foreseeable future. And even if it had, it wouldn’t have been the end of the world – but we certainly would have known about it, especially if it had been over a populated area. Based on its size, even without knowing composition, I’m making an uneducated guess of a Chelyabinsk-sized impact event. That didn’t happen.

Learn more about 2015 ET’s parameters here, and see more night sky videos from the Crni Vrh Observatory here.

*Technically the time of closest approach for 2015 ET was 16:42 UTC on March 10.

11 Replies to “This Is The Asteroid That Didn’t Hit Us”

  1. The caption on the video identifies the object as “WEBF312.” Object WEBF312 is NOT asteroid 2015 ET, and has not yet been officially cataloged by the IAU Minor Planet Center. Asteroid 2015 ET did in fact pass within 0.3 LD of the Earth, but that was on March 10, at 16:42 UT, but the asteroid depicted in this video is NOT 2015 ET.

      1. No idea, i just checked and saw it being recently updated, which would be easy to miss. But WEBF312 seems to be a different object, right ?

      2. I’m wondering if WEBF312 was a temporary designation for 2015 ET, since no other close NEO is listed in that time frame (and <100k km is definitely a close approach.)

      3. The temporary designation initially assigned to 2015 ET was WE086B0. Different object. WEBF312 is still uncatalogued because after its close approach it was on the day side of Earth, and is now only about 10 degrees from the Sun. So there have been no additional confirmation observations.

  2. I remember a few years ago they discovered a NEA that was another “close call”. Problem is, they discovered it 4 days AFTER it crossed earth’s path. Anyone else remember that story?

    1. Many of these close call asteroids are discovered after closest approach. They approach the Earth from inside the Earth’s orbit and so in daylight, the daylight side. No one sees them. That’s why we need a dedicated scope. At Ames, I submitted a proposal to place a scope on ISS which could scan around the Sun for NEAs while on the dayside of its Earth orbit.

      After they pass Earth, they are now outside our orbit and enter into night side view. They are discovered and their orbits are traced and a close approach had often already happened.

      Yeah, I don’t know about this one but heck, does anyone else have a hard time seeing the asteroid among the star field?

      1. 4 Days after!..Wow! Thanks for those wonderful words of comfort, I am sure we will all sleep better now 🙂

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