[AZ-Observing] Re: 2015 TB145
- From: L Knauth <Knauth@xxxxxxx>
- To: "az-observing@xxxxxxxxxxxxx" <az-observing@xxxxxxxxxxxxx>
- Date: Sun, 1 Nov 2015 04:47:21 +0000
Very informative! Thanks!!
Paul Knauth
________________________________________
From: az-observing-bounce@xxxxxxxxxxxxx [az-observing-bounce@xxxxxxxxxxxxx] on
behalf of Brian Skiff [bas@xxxxxxxxxx]
Sent: Saturday, October 31, 2015 9:17 PM
To: az-observing@xxxxxxxxxxxxx
Cc: bas@xxxxxxxxxx
Subject: [AZ-Observing] Re: 2015 TB145
On Sat, 2015-10-31 at 20:21 -0400, Paul Lind wrote:
Michael,
Very nice job. I know that probability says not to worry; however I think
it's scary that a large rock like this was only discovered three weeks before
closest approach!
It is perhaps worth bearing in mind a couple of
things re Paul's quite reasonable comment.
We now know enough about the statistics of the
close-approachers that we can say that within the
sphere out to the radius of the Moon, there are _always_
one or two mostly quite small objects passing through.
They are often simply not discovered, or are
discovered on their way out, having come in from the
daytime side. These of course don't make the news,
and a modest problem is that they often don't get
followed-up well enough to establish more than a
rough orbit. Amateurs have done excellent service,
not incidentally, in doing this follow-up to the
limits of their telescopes. And this sort of thing
is set to improve in the coming few years both on the
amateur and the professional side.
Another thing to consider is that an object
like TB145, discovered three weeks out, would allow
evacuation of a big city, say, if the impact prediction
could be made that well. (I think it now can --- this
thing that's coming in at the end of November is
well-enough tracked to know the impact location
within a few kilometers radius in the ocean somewhere
south of Sri Lanka.) Could you evacuate metro Phoenix
that fast? Just imagine your twice-daily rush-hour
that already happens at least six days a week, but going
full time for a few days. So, yes. Could you evacuate a
middle-sized country, say France (not much bigger than
Arizona, but with a lot more people) in a month? Probably.
A big object that would necessitate such a thing would
(on average) be detected a lot further out time-wise.
So things are not as bad as they seem --- either scenario
would be catastrophic, and knock everything else off
the headlines, certainly, but we wouldn't just be
proverbial sitting ducks only able to watch the thing
come in. You get the heck out of the way! Similar sort
of thing for the more likely ocean impact, where you
have to ponder tsunami-type waves on a colossal scale.
All the foregoing is not original to me ---
people have been thinking along these lines for a long time.
\Brian
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