Cometary Activity increase - A Cause ?

[gaa_ian (Ian)]

This is an extract from an article on the risk of increased cometary impact due to the passage of the sun through the Galactic plane:

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.

Could we be experiencing the early effects of this already, with the increase in Comet activity we are seeing ATM ?
PANNstars, Lemmon, Ison and now the potential Mars impacting comet.
If I am way off the mark, please do elaborate !

[Ric]

Originally Posted by gaa_ian

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.

Just wondering Ian

What do they class as "the near future"

[renormalised (Carl)]

That's right, Ian, it does bob up and down through the plane of the spiral arms, roughly every 35-40Ma. However, at this moment, the Sun and the Solar System are about 2-5 million years into their journey out of the spiral arm in an upwards direction. We're about 25pc above the plane of the Galaxy and will eventually reach around 200-250pc above the plane in about another 10-15Ma. There's a lag time between passage across the plane and when the comets might come in...around about a million or so years. However, whether comets do reach in as far as the inner Solar System depends on a lot of factors, the most important being whether any comets were scattered into the inner Solar System by a close passage of another star or us passing through a dense nebular on the way through. How many get scattered and where is totally random and really can't be predicted. Only that it's possible that some did make their way in. As for the present activity being accounted for by our previous passage...I would doubt it, but it's not entirely impossible. Some comets might be stragglers from the scattering effects of passing stars or nebs, but it would be impossible to tell. The last time we were in the spiral arms was when the Sun was around 80-100ly away from the Centaurus-Scorpius OB1 Association. If we had made heavy way through the spiral arms and lots of comets were scattered, we could've be in for one very lively sky show!!!!. It would be conceivable that we may have experienced multiple impacts, if we're unlucky. The last time we experienced anything like that was in the Late Eocene-Early Oligocene, when the Solar System would've just passed through the arms on its way downward out of the plane. We had several impacts not long after the passage (e.g. Chesapeake Bay Crater), for instance.

[Suzy]

Good on you Carl, and great to see you back!
This is such an interesting thread, thanks Ian for posting the topic.

[Ric]

Hi Carl

Great to see you back online.

[astroron (Ron)]

Lots of information there Carl
As Suzy said back.
Cheers

[Rob_K]

I feel a bit of critical thinking needs to be applied here. Cardiff Centre of Astrobiology? What is it? This doesn't seem to be one of the major observatories or universities that we get our usual breakthroughs and pronouncements from. Why would an 'astrobiology' research centre in Wales be tracking our movement through the galaxy for?

A quick web search reveals that the CCAB (now the BCAB) has been under the directorship of Professor Chandra Wickramasinghe. He is the person who finds fossils in meteorites (see a recent IIS thread) and is generally regarded as well outside the mainstream.

This doesn't invalidate the science, but for me the big red warning lights are flashing madly.

Cheers -

[gregbradley]

I think these changes occur over millions of years and so if it does occur the time frame would be enormous and certainly not next year.

Greg.

[ZeroID (Brent)]

I think Carl applied the 'critical thinking' very nicely.

[gaa_ian (Ian)]

Awesome, thanks for the replies everyone & for the detailed Analysis Carl.
It is good to discuss these issues, as no doubt Media reports will arise citing this or that as the cause of the seeming abundance of comets.
Especially if one is coming close to Mars as predicted.

[OICURMT]

My 1.5cents worth...

There's most likely a technological component with respect to the "apparent increase in the number of comets"... (i.e. probably no increase at all).

Why do I think so? ... Take a look at the discovery rate of Asteroids... (Old Version) with the advent of better and better equipment, satellites, telescopes, cameras, etc... the number of asteroids have increased tremendously. BTW: Space is "empty"?!?? and take a good look around our neighborhood!

For comets, the discover rate is on the rise, from both amateurs and professionals as bigger, better telescopes with bigger, better cameras take their place in the world looking skyward. The key reason why we know more about them, internet, social media and the print and online media's appetite to grab any news, regardless of its worth...

OIC!

[gaa_ian (Ian)]

I could not let this one go easily & have written an article on my blog AskTheScienceGuru.com
Thanks everyone for your input on this topic !

[snas (Stuart)]

Ian

Love your work up there in Nhulunbuy, I would like to get up there one day.

Anyway, 4 comets in a year. Maybe I'm wrong, but this could be easily explained by the statistics of small numbers, things that don't happen often. When you are looking at things that happen infrequently, it is not unusual to have a period of time in which nothing happens, or to have a sudden spike in numbers. This is a possible reason for so called "cancer clusters" and potentially also for "comet clusters". For example, if something was to happen 10 times a year in Australia, it would not be surprising to see 4 episodes in a single month and then see very few or no episodes for the next few months.

Just my thoughts

Stuart