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The Past | The Previous

The Nemesis Scenario

I'd never heard of this before, but (even if no one sounds too confident about it existing) it sure is cool:

Nemesis is a hypothetical red dwarf star or brown dwarf, orbiting the Sun at a distance of about 50,000 to 100,000 AU, somewhat beyond the Oort cloud. This star was originally postulated to exist as part of a hypothesis to explain a perceived cycle of mass extinctions in the geological record.

In 1984 paleontologists David Raup and Jack Sepkoski published a paper claiming that they had identified a statistical periodicity in extinction rates over the last 250 million years using various forms of time series analysis.[1] They focused on the extinction intensity of fossil families of marine vertebrates, invertebrates, and protozoans, identifying 12 extinction events over the time period in question. The average time interval between extinction events was determined as 26 million years. At the time, two of the identified extinction events (Cretaceous-Tertiary and Late Eocene) could be shown to coincide with large impact events. Although Raup and Sepkoski could not identify the cause of their supposed periodicity, they suggested that there might be a non-terrestrial connection. The challenge to propose a mechanism was quickly addressed by several teams of astronomers.

Two teams of astronomers, Whitmire and Jackson, and Davis, Hut, and Muller, independently published similar hypotheses to explain Raup and Sepkoski's extinction periodicity in the same issue of the journal Nature.[2][3] This hypothesis proposes that the sun may have an as yet undetected companion star in a highly elliptical orbit that periodically disturbs comets in the Oort cloud, causing a large increase in the number of comets visiting the inner solar system with a consequential increase in impact events on Earth. This became known as the Nemesis (or, more colorfully, Death Star) hypothesis.

If it does exist, the exact nature of Nemesis is uncertain. Richard A. Muller suggests that the most likely object is a red dwarf with magnitude between 7 and 12,[4] while Daniel P. Whitmire and Albert A. Jackson argue for a brown dwarf. If a red dwarf, it would undoubtedly already exist in star catalogs, but its true nature would only be detectable by measuring its parallax; due to orbiting the Sun it would have a very low proper motion and would escape detection by proper motion surveys that have found stars like the 9th magnitude Barnard's star.

The last major extinction event was about 5 million years ago, so Muller posits that Nemesis is likely 1-1.5 light years away at present, and even has ideas of what area of the sky it might be in (supported by Yarris, 1987), near Hydra, based on a hypothetical orbit derived from original apogees of a number of atypical long-period comets that describe an orbital arc meeting the specifications of Muller's hypothesis.


The idea of periodic extinction rates is pretty neat, at least from No Chance It'll Happen Tomorrow point of view (although, maybe 2012, if we're all real lucky), and the whole idea of a giant, unproven, hidden star, only makes it slightly better. It's a kind of mad science, the type of thing that results in bad, bad Hollywood films.

Link.

(crossposted)

Comments

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drjon
Sep. 22nd, 2009 12:15 pm (UTC)
Nemesis is cool.

Other cool things are Theia, which possibly impacted Earth to throw out the Moon (or, if you feel classical, Selene or Luna), and Phaeton, which probably didn't disintegrate to form the Ceres belt (which is a reasonable name for the Asteroid Belt, now it's a planet).

Edited at 2009-09-22 12:15 pm (UTC)
benpeek
Sep. 22nd, 2009 12:19 pm (UTC)
aw. kind've a shame the second is out of vogue.
drjon
Sep. 22nd, 2009 12:32 pm (UTC)
I love the Kook names for Phaeton: Tiamat, Astra, Maldek... lovely!
darinbradley
Sep. 22nd, 2009 01:01 pm (UTC)
Hadn't heard of this—nice find, dude.
benpeek
Sep. 24th, 2009 01:16 am (UTC)
thanks, man. researching end of the world scenarios is kind've fun.
(Anonymous)
Sep. 24th, 2009 12:48 pm (UTC)
Saw some photos of those dust storms down in your neck of the woods. Speaking of apocalypse—those things are terribly beautiful.
darinbradley
Sep. 24th, 2009 12:49 pm (UTC)
Crap, sorry—that was me.
benpeek
Sep. 24th, 2009 03:36 pm (UTC)
yeah, they were real cool.

except for when i had to clean the dust away today. that kind've sucked.
darinbradley
Sep. 25th, 2009 01:15 pm (UTC)
Yeah, no doubt. I lived in West Texas for a year, and the dust storms would come through there so heavily that the dirt would gather like red snowdrifts against the buildings. Even with wet towels against the windows and the doorjamb, it still smelled like a grave in that apartment.

Hope it all clears out quickly.
ashamel
Sep. 22nd, 2009 10:39 pm (UTC)
Does it cause dust?
benpeek
Sep. 24th, 2009 01:17 am (UTC)
one can only hope
robertfwexler
Sep. 25th, 2009 11:31 pm (UTC)
I read Muller's book, Nemesis: The Death Star, back when it came out and I'd forgotten all about it. I'm sure it's been a dull worry, adding to my dystopian outlook.
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