Another Low-Flying Space Rock

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Another Low-Flying Space Rock
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By Chuck McPartlin

On Wednesday evening, October 11, an approximately 50-foot across Potentially Hazardous Asteroid named 2012 TC4 made a close flyby of the Earth, passing within about 32,000 miles, or about 13% of the distance to the Moon. Astronomers around the world monitored its passage, as a sort of test run for defending the Earth in some future asteroid encounter.

For Santa Barbara, TC4 was low in the SSE at the end of twilight, and rapidly heading lower, so imaging it was a race between twilight, TC4’s rotational aspect, its altitude above the horizon, and atmospheric extinction, the dimming caused by looking through more air near the horizon. But TC4’s window of maximum brightness coincided with its window of visibility for me, and so it was catchable.

Here’s is the video, not speeded up, of TC4 zooming past at around 7:50 PM PDT. It looks like a streak because the video camera was integrating for 256 frames, or about 8.5 seconds, to capture enough photons from the asteroid. For a sense of scale, the entire frame is just a bit smaller than the Full Moon.

Relative to us, 2012 TC4 was going about 4.7 miles per second, which is actually rather slow, and it was close enough to us that the Earth was substantially altering its orbit as it cruised by.

The asteroid has a relatively fast rotational period estimated to be a bit over 12 minutes, and it varies by about 1 magnitude (2.5 x) in brightness over that period, so it is probably elongated rather than spherical in shape. Indeed, when I last saw TC4 at about 8:16 PM PDT, it was barely detectable.

There are probably lots of new articles and radar images of 2012 TC4 coming out today, but below are some good information sources as of Wednesday evening.

References for a Cloudy Evening

Hasta nebula!

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Resident Oct 15, 2017 08:51 AM
Another Low-Flying Space Rock

For more information about asteroids that might hit the earth and what we can do about it. check out the non-profit B612 Foundation. <https://b612foundation.org/>

FondofSB Oct 14, 2017 08:04 PM
Another Low-Flying Space Rock

Thanks Chuck as always! One question : being so close to earth did it also "benefit" from the "sling shot" effect used to accelerate some long ranging spatial probe, and if so , do you have any idea of how much speed it gained ?

macpuzl Oct 14, 2017 11:23 PM
Another Low-Flying Space Rock

Fond - My pleasure. The spacecraft gravity assist from a planetary close encounter is dependent on both the rotation of the larger body and its orbital motion. It is usually meticulously planned to transfer as much momentum as possible from the planet to the spacecraft. In this encounter, 2012 TC4 was travelling retrograde, so opposite our orbital motion, and my guess would be that it was slowed down in addition to having its direction changed slightly. (See the animation on the S&T link.)

a-1511266203 Oct 14, 2017 10:17 AM
Another Low-Flying Space Rock

It is only a matter of time before one of these "rocks" hits earth. It will be interesting to hear who the media will blame! Sales of sunscreen will significantly drop for about 100 years.....or longer. Plus, and end to global warming, but there definitely will be climate change!!! LOL!!!

a-1511266203 Oct 15, 2017 09:13 AM
Another Low-Flying Space Rock

So true the right-wing media will blame President Obama - Foe Shore! And probably a protest on State St. with people carrying slogan signs ("Asteroids Have Rights!") and Aztec dancers (talk about peeps who know a thing or two about sacrifice...whoo doughgee),

a-1511266203 Oct 15, 2017 09:21 AM
Another Low-Flying Space Rock

So true the right-wing media will blame President Obama - Foe Shore! And probably a protest on State St. with people carrying slogan signs ("Asteroids Have Rights!") and Aztec dancers (talk about peeps who know a thing or two about sacrifice...whoo doughgee),

a-1511266203 Oct 14, 2017 10:41 AM
Another Low-Flying Space Rock

You can be sure the right wing media will blame Barack Obama and the left wing media will bring up the extinction of dinosaurs and relive the entire history of evolution.

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