Comments on: We are totally doomed

By: Omega Centauri

Omega Centauri — Mon, 15 Mar 2010 18:34:02 +0000

I don’t have any real numbers, but shouldn’t the orbital perturbations be because of the tidal effect. This should scale as the derivative of the gravitational force, which would imply an inverse R cubed effect. Five to the third overwhelms the factor of ten mass ratio. But of course the length of the encounter matters as well. I suspect that an encounter whose characteristic time is longer than the orbital period of cloud objects wouldn’t be very effective as it the tidal acelerations on a given object could then cancel out. So perhaps these far encounters might not be all that effective.

But, there must have been some who did research projects on the issue, so it ought to be answerable.

By: andy

andy — Mon, 15 Mar 2010 12:07:58 +0000

Greg Laden: sure I am not disagreeing that some stars have come a lot closer than Algol did in the past 7 million years, the question is how much they would perturb the Oort cloud. Most of the "close calls" are from low-mass stars that didn't hang around very long, unlike the slow-moving and massive Algol system. Unfortunately the paper does not appear to calculate relative sizes of perturbations, but the encounter parameters do not seem to differ too much from this one - it is striking to see how much more significant the Algol encounter is compared to closer but faster and less massive stars.

By: Somnolent Aphid

Somnolent Aphid — Sun, 14 Mar 2010 20:53:08 +0000

If is doesn’t happen in 2012 then it must be a hoax.

By: VRWC

VRWC — Sun, 14 Mar 2010 18:38:15 +0000

Tell Al Gore. He will find a new pastime.

By: Douglas Watts

Douglas Watts — Sun, 14 Mar 2010 18:32:40 +0000

Guess I picked the wrong geologic epoch to quit sniffing glue.

By: Greg Laden

Greg Laden — Sun, 14 Mar 2010 17:22:15 +0000

Andy, you may be half right and half wrong. These are new numbers based on a new study that is not entirely contradictory to the older studies, but is different. One of those differences contradicts your assertion that the last close call would have been 7.5 mya. Check back through the link for that, I’m not following the details myself that closely.

By: andy

andy — Sun, 14 Mar 2010 17:08:53 +0000

Well the Gliese 710 encounter has been known for a while, and the miss distances estimated there don’t seem too far off the values previously quoted.

In terms of how much this will perturb the Oort cloud, the last event of comparable severity was the Algol triple system passing at a distance of roughly 2.4 parsecs about 7 million years ago. The larger distance compared to Gliese 710 is compensated by the higher mass of the Algol system (totalling about 6 solar masses, as opposed to 0.5 solar masses for Gliese 710) and the longer duration of the encounter.

Given life on Earth is still here, it is fairly obvious that the passage of the Algol system didn’t wipe out everything in a blaze of cometary fury.

By: MadScientist

MadScientist — Sun, 14 Mar 2010 16:55:26 +0000

@Paul S.: Oort cloud is named after Jan Oort – he was Dutch.

By: daedalus2u

daedalus2u — Sun, 14 Mar 2010 16:19:16 +0000

Actually this will be a good opportunity (provided it doesn’t come too close to the Sun, close enough to disrupt the orbits of things inside Jupiter’s orbit).

A shower of comets coming into the inner solar system will be an oportunity to put them into capture orbits around Earth, Mars and Venus.

Mars will then be pretty easy to terraform, Venus somewhat more difficult. The limiting factor on Venus is getting enough hydrogen to provide enought water. The CO2 atmosphere can be pumped underground. Once Venus cools and has enough water, the CO2 will be trapped as carbonates.

By: Deen

Deen — Sun, 14 Mar 2010 16:17:00 +0000

@Paul S: unfortunately not: http://www.telegraph.co.uk/science/space/7429335/Search-on-for-Death-Star-that-throws-out-deadly-comets.html