The Death of Nemesis: The Sun's Distant, Dark Companion

[yevaud]

The Death of Nemesis: The Sun's Distant, Dark Companion
The data that once suggested the Sun is orbited by a distant dark companion now raises even more questions

Over the last 500 million years or so, life on Earth has been threatened on many occasions; the fossil record is littered with extinction events. What's curious about these events is that they seem to occur with alarming regularity.

The periodicity is a matter of some controversy among paleobiologists but there is a growing consensus that something of enormous destructive power happens every 26 or 27 million years. The question is what?

In this blog, we've looked at various ideas such as the Sun's passage through the various spiral arms of the Milky Way galaxy (it turns out that this can't explain the extinctions because the motion doesn't have had the right periodicity).

But another idea first put forward in the 1980s is that the Sun has a distant dark companion called Nemesis that sweeps through the Oort cloud every 27 million years or so, sending a deadly shower of comets our way. It's this icy shower of death that causes the extinctions, or so the thinking goes.

Today, Adrian Melott at the University of Kansas and Richard Bambach at the Smithsonian Institute in Washington DC re-examine the paleo-record to see if they can get a more accurate estimate of the orbit of Nemesis.

Their work throws up a surprise.

Full Article

 

[SteveCNC]

interesting article , I wonder what an event could be that could have a cycle with that much regularity . Maybe our solar system passes under the business end of a pulsar . It would seem to me that for a regular event to occur I would think it would have something to do with our position passing through something bad , not something throwing stuff our way cause I don't think that could be regular enough to have objects in the right place to throw them at and hit us from the ort cloud . Maybe that's how often we have a full planetary alignment while at our closest possible locations and it causes stress that blows yellowstone or many other volcanoes .

 

[ZenGalacticore]

Yes, very interesting. But how often doess the Sun come near enough to other stars to cause a noticeable perturbation in anything orbiting the Sun?

Second question: How far would a brown dwarf, say, have to be out in an irregular, comet-like orbit to orbit the Sun every 26 million, or perhaps every 13 or 14 million years? Half a light-year, maybe? A light-year?

What I'm saying is, that Alpha Centauri A ,B, and Proxima are roughly 4.2 lys away. Does their proximity have any effect on our system? How close has the Sun come to other stars in the last 500 million years? And how do they know? I assume they run the motions back in computer models, extrapolating, just like they can run them forward?

Questions, questions, and more questions!

I don't think that Nemesis is that far-fetched, btw. After all, most star systems are binary or trinary. And even many of the solitary star-systems we've studied have planets much more massive than Jupiter. (Obviously, those are mostly the only ones we can detect, as yet, but still.)

IOWs, if many solitary Sun-like stars can have Jovians 5 or 6 or more times more massive than our Jupiter, then it stands to reason that the Sun may have a giant brown dwarf (is that an oxymoron, like 'jumbo shrimp'?) companion orbiting every several million years.

 

[yevaud]

Questions, questions, and more questions!

Precisely why I posted this. The paper rather discounts the possibility of Nemesis on the one hand (I must suppose their ballistics are good enough to be correct as to a theoretical Nemesis' orbit not matching the extinction events). But on the other, there's still that all-too-real pesky extinction event periodicity, which must mean something is causing it.

So what is it? Are they incorrect about a dwarf companion's orbit / periodicity? Is there another principal cause?

 

[robnissen]

Questions, questions, and more questions!

But on the other, there's still that all-too-real pesky extinction event periodicity, which must mean something is causing it.

Not necessarily. Humans love to find patterns and give the patterns meaning. That's why the stock market goes up when the AFC wins the Super Bowl (or vice versa, I don't recall.)

Here, even over a span of 500,000,000 years, that is only 19 data points (at 27,000,000 years per data point). That is not near enough to make broad claims that something more than random chance is going on. Now, of course there may be a causation for this correlation, but there is not enough data to say with any large degree of certainity that "something is causing it."

 

[crazyeddie]

The Nemesis theory is exciting to think about, but I believe it's rather unlikely. There is no known binary system that contains stars with such long orbital periods as would be required if Nemesis were a real object, which means it would be avery unique thing, indeed. The sun would have a very difficult time hanging on to a companion with such a wide orbit. If it were a red dwarf star, one of the many previous sky surveys should have found it by now. If it is a brown dwarf, then that would explain why it hasn't been found yet, but the WISE spacecraft, launched last year, should be able to detect the infrared energy any such body would emit. We won't have the results of it's mission ready until 2013, from what I've read. Until then, it's an intriguing possibility.

 

[Couerl]

I agree with Eddie that it's unlikely. Even at 27 Ma years the points do not line up exactly. They are regular extinction events with a +/- of several million years and varying intensity in most cases which, to me at least suggests a more localized pattern. It could be something as relatively simple as the sun doing its own version of a solar hiccup or perhaps the earth itself is on a kind of volcanic clock, or a combination of events. Although the article points to the notion that the next event is 16 million years away, La Garita was 27 million years ago and was the largest bang since Chicxulub. Interestingly, it didn't seem to cause a pronounced world-wide extinction which, possibly means that the fossil data is still not adequately documented (I.E. That graph ain't all that accurate yet). It's my guess that the three largest events were asteroids and the smaller one's perhaps volcanic and that climate change itself without catastrophic events over the last billion or so years played a more significant role than what we give it credit for..

 

[MeteorWayne]

To me as well, with the fragmented and incomplete fossil record, trying to assaign a percentage to extinction events is just silly. And how do you define it? Species, heck we haven't even a complete count of the species that exist now. Genus? Family? what makes any one measure better or more accurate than another?

I note the graph just says "percentage" but of course there's no detail on how that percentage was calculated....

 

[yevaud]

Beats me; I just post the things for discussion.

 

[MeteorWayne]

Hey, no problem with that. Discussion is good!

 

[yevaud]

Absolutely, or we wouldn't be here.

 

[OleNewt]

Given "Sun, Jupiter, and everything else", and given that pretty much nothing orbits in a matching manner to anything else (ie, moving like a clock hand), there's gotta be some wild gravitational swings when significant members not only align themselves but also draw closer to belt/kuiper/oort objects. Are they close enough together to affect dramatic shifts?

 

[yevaud]

Ah. "Syzygy." No, the effects of those are minuscule.

 

[MeteorWayne]

Given "Sun, Jupiter, and everything else", and given that pretty much nothing orbits in a matching manner to anything else (ie, moving like a clock hand), there's gotta be some wild gravitational swings when significant members not only align themselves but also draw closer to belt/kuiper/oort objects. Are they close enough together to affect dramatic shifts?

Planets orbiting in line like the hands of a clock is impossible; Mr. Newton and Mr. Kepler made sure of that with the laws they discovered and documented. The further a planet is from the star, the slower it moves along it's orbit, so they can't stay in line.

Now the gravity does cause all kind of havoc when the periods of planets are in whole number ratios. For example, the asteroid belt is roughly bordered by the 4:1 and 2:1 ratios with Jupiter. IOW, 4 orbits of the asteroid to 1 of Jupiter on the inner edge, and 2 orbits of the asteroid to 1 of Jupiter at the outer edge. And there are several gaps within the belt at other ratios, such as 3:1, 5:2, and 7:3. Objects at resonances get a kick every time at the same place in the orbit and are ejected from that orbit, either outward or inward.

By the same method, the Kuiper belt is roughly defined by the 3:2 and 2:1 ratios with Neptune. The Plutinos (like Pluto) in fact have the exact 3:2 resonance with Neptune and orbit exactly twice for each 2 orbits of Neptune, while there is a population of what are called twotinos near the outer edge. In between is generally stable, so is where most of the KBO's reside.

It is thought in fact, that Uranus and Neptune began their life much closer to the sun (possibly even inside of Satur's orbit) and were moved to their current location from resonances with Jupiter and Saturn. As they migrated outward, they stirred up the proto Kuiper Belt and about 99% of the objects were ejected leaving the more tinly populated current belt.

 

[Woggles]

What I like to know is how accurate the numbers are. Is there a +,-. And can a geological record really be read accurate or is it more like an intellectual guess?

I basis these questions from this article I found.

http://www.wired.com/wiredscience/2010/ ... es+2%29%29

Quote “Other astronomers think Nemesis is still out there, however. Richard A. Muller of the University of California at Berkeley, one of the authors of the 1984 paper proposing the dark star and the author of a popular book called Nemesis: The Death Star, thinks Melott is “coming to too strong a conclusion.”
“I would agree with most of what he says, but I think he is overestimating the accuracy of the geologic timescale,” he said. The geological record gives only an approximate sense of when major extinctions happened. “You get them in the right order, but it’s really difficult to get an actual date,” he said. In light of that uncertainty, “I would say the Nemesis hypothesis is still alive.”

 

[yevaud]

:lol:

Wayne, we once had long discussions here of resonances and Kirkwood Gaps, when debating the "EPH" (Exploding Planet Hypothesis).