Comet Strikes Increase as We Pass Through the Galactic Plane

There are just so many ways the Universe is out to get us. Astronomers have already considered the threat from our Sun’s orbit around the center of the Milky Way. When our Sun rises up out of flat plane of the Milky Way, it appears we might be less protected from intergalactic radiation and cosmic rays. Well, it looks like passing through the middle of the galactic plane might have its own share of risks: an increased number of comets might be hurled towards the Earth because of gravitational interaction with the densest parts of our galaxy.

Researchers at the Cardiff Centre of Astrobiology have built a computer model of the Solar System’s journey around the Milky Way. Instead of making a perfectly flat orbit around the galaxy’s centre, it actually bounces up and down. At times it can rise right up out of the galactic plane – getting 100 light years above – and then dip down below it. They calculated that we pass through the plane every 35 to 40 million years.

And this time period seems to match dangerous periods of impacts on Earth. According to the number and age of craters on Earth, we seem to suffer increased impacts every 36 million years. Uh oh, that’s a match.

In fact, one of these high points of comet activity would have been 65 million years – the same time that an asteroid strike wiped out the dinosaurs.

And here’s the bad news. According to their calculations, the Solar System will be passing through the galactic plane in the near future, and should see an increased risk of impact. Our risk of impact could increase 10-fold.

There might be a silver lining to the bounce, though. The impacts might have helped life spread across the galaxy.

While the “bounce” effect may have been bad news for dinosaurs, it may also have helped life to spread. The scientists suggest the impact may have thrown debris containing micro-organisms out into space and across the universe.

Centre director Professor Chandra Wickramasinghe said: “This is a seminal paper which places the comet-life interaction on a firm basis, and shows a mechanism by which life can be dispersed on a galactic scale.”

Here’s more info on the story from Bad Astronomy.

Original Source: Cardiff News Release

17 Replies to “Comet Strikes Increase as We Pass Through the Galactic Plane”

  1. IN COMMING!!!!!!! RUN FOR COVER!! hahaha.

    So if the last one was 65 million years ago, and they happen about every 35-40 million years, arn’t we over due for one by about 37 million years? Are we now about the time of the second 37 million year mark to have one?

    Dang, should of ordered the pizza and beer!

    I think their watching out for these neo’s already. Not sure just what their going to do if one of those 6 mile neo’s comes our way, but their watching for them. Hopefully by the time one does come our way, will have learned how to rebuild a death ray canon like Nikola Tesla made in the early 1908.

    Look up:


  2. I believe that the comet shower hypothesis better explains the extinction of the dinosaurs better than the asteroid shower theory. I had a publisher interested in a book on comet showers. This is not to say that an asteroid did not strike the Earth. A sea drill in the Pacific showed a stony asteroid fragment. Robert Rochia of the French Atomic Energy Commission did the work in 2000 off Japan. He believed it was a mile wide.
    That is a different type of asteroid than the recent theory on asteroid showers. It also does not rule out another asteroid hitting us too.
    There is a double crater in Russia, but I believe this happened from a binary asteroid. Again, this may be related to the comet shower.
    Utah has Upheaval Dome. There is Eagles Butte in Alberta. These are 65 million year old craters. We also have the Boyish crater in Russia. Another crater is the Silver Pit Crater in the English Channel. Venus also has a twin of the main dinosaur crater just as old and as big.
    In the K-T boundary, there are signs of Tunguska Events from comets. It means comets played a role. Now, we do not have enough data to match all of these up to a comet shower, but there are many holes in the ground at the right time.
    There are also Permian craters. We do not have it confirmed, but there is probably a larger crater under the ice in Antarctica. There may be one off Australia. Both of these line up with the Siberian basalt flats. Rocheouart is another crater that dates back from that time. Add in St. Martin’s Crater in Canada. We also have the Obolon Crater in the Ukraine and the Red Wing Crater in North Dakota.
    The Sudbury impact came when the Earth was in this unlucky position, but it has no other evidence that has survived. At least there is none that I am aware of, and I am happy to be corrected.
    The Devonian did have impacts but the Earth was not in a position for this. A star still may have traveled through the Öort Cloud and caused this. Tau Ceti has 12 times the dust it should with a red dwarf within a light year of it.
    There is a crater in Nevada, another in Australia, and a third in Germany. There is a fourth crater in Sweden called Siljan. We also have a crater chain from this epoch in the Midwest with a crater every six miles in almost a straight line from Missouri, Illinois, and Kansas. A comet probably broke up and did this. There is some evidence of an ocean impact from this time as well.
    The Eocene had a comet that created Chesapeake Bay and a piece hit off the Palisades off New Jersey. There is another in Russia. Again, Earth was in the plain of the galaxy in a spiral arm. There is also another from this period.
    There is some evidence for the Triassic to have ended with a smaller comet shower. The same thing happened in the Jurassic.
    Be aware that there were other signs of stress with life at these times. Should the Earth have passed through a molecular cloud, it would also have effects on the climate, but the answer is probably more complex than this.

  3. Oh, we are going to have another comet shower if you want to wait 500,000 years. The Earth will enter a molecular cloud. It will shrink the heliosphere, severiring the connection with the Interplanetary Magnetic Field. Dust will drift into the atmosphere, changing the chemistry.
    Some of you may not want to wait that long, so expect one when a red dwarf named Gilese 710 enters Oort Cloud in 27,000 light-years. Bernard’s Star will get 1.1 light years from us sooner but may not cause a comet shower.

  4. Interesting that this is coming out now, since it is hardly new information. The fact that comet activity is correlated to galactic plane crossing has been well documented in the literature for several years. It also correlates to ice age epochs. See Gies & Helsel, ApJ, 2005, for an excellent analysis of this idea.

  5. Was the effect of the dark matter “halo” considered in the calculation? This might produce a different period for the “bobbing” or eliminate it altogether. If the sun were “bobbing”, wouldn’t this imply that many (or even all) other stars were also “bobbing”? By analogy with coupled harmonic oscillators, this could lead to a regular distribution of steller masses centered on the galactic plane. Has such a relation been observed? Why doesn’t the Sag A debris field “bob” too? Can the existence of large scale galactic structures, which have endured over billions of years, be reconciled with “bobbing” stars?

  6. As to those ages not marked by the signatures of encounters through the more populated areas of the galaxy, some encounters may be more dangerous than others, characterized by less density of “object” from mole cloud to red giant to “dumb luck.”

    It’s an engaging theory, but as I’ve pointed out to the folks at Cardiff, its not original. This idea is at least as old as the discovery of the K-T Boundary and has been put forth as one way to explain periodic extinctions for more than twenty years.

  7. So, the Solar System “bobs” up and down the galactic plan, crossing it once every 35-40 million years. This sound like it is ORBITING something, at a distance of 100 lights years. Whoa. It’s gotta be BIG. Or at least massive. I wonder what it is?

  8. We are 67 light-years north of the galactic plane. Unless the Earth goes into warp drive, we will not be in the galactic plain any time soon. In fact, the Earth is moving at 20 kilometers a second. This is 12.5 miles per second, or 45,000 miles per hour.

  9. So when can we expect some extra activity. Does anyone else hear that frequency, even with my ears closed, is it the sun? or galaxy core getting louder, resinking our galaxcy to the same frequncy?

  10. Msybe a little late to post this but …
    So suppose a comet hits us 2012. It will spit up a gaint dust cloud, and blocks the sun.

    1) We have technology that can make artificial light to grow food
    2) It’s going into winter anyway and it should (hopefully), correct me if I’m wrong, clear by spring?

    And Waylander 348, what do you mean when you say “north” of the galactic plain?

  11. Just as the earth orbits the sun, the sun oribits the center of the milky way. Just as the earth moves periodically higher and lower (north and south) in it’s orbit around the sun, so does the sun in it’s orbit around the galactic center. The Sun (and hence, the earth) is now quite far North of the galactic plane in our orbit around the galactic center. If you are waiting for a crossing of the galactic plane, you have a few million years to wait.

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