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ToSeek
2004-Jul-02, 03:52 PM
Death Down Asteroid Alley (http://www.astrobio.net/news/modules.php?op=modload&name=News&file=article&sid= 1053&mode=thread&order=0&thold=0)


Astronomers studying the Tau Ceti system have discovered that it contains ten times as much material in the form of asteroids and comets as our own solar system.

Tau Ceti, only 12 light years away, is the nearest sun-like star and is easily visible without a telescope. It is the first star to be found to have a disk of dust and comets around it similar in size and shape to the disk of comets and asteroids that orbits the Sun.

The astronomers' discovery, being published in Monthly Notices of the Royal Astronomical Society, suggests that even though Tau Ceti is the nearest Sun-like star, any planets that may orbit it would not support life as we know it due to the inevitable large number of devastating collisions. It also suggests that the tranquil space environment around the Earth may be more unusual than previously realized.

Padawan
2004-Jul-02, 06:10 PM
You always manage to find interesting articles! :)

Betenoire
2004-Jul-02, 07:27 PM
That's why he's the Post Doc

Swift
2004-Jul-02, 08:45 PM
It also suggests that the tranquil space environment around the Earth may be more unusual than previously realized.
I'm not an expert, but that seems like a bit of an unreaching extropolation. Are there other examples of system with "too many" comets, or are they drawing a conclusion from one example? IIRC, the theory is that our own solar system went through a period of a high density of asteroids and comets. Could it be that Tau Ceti is just a younger system or is taking longer to get through that period?

Brady Yoon
2004-Jul-03, 12:41 AM
I'm not an expert, but that seems like a bit of an unreaching extropolation. Are there other examples of system with "too many" comets, or are they drawing a conclusion from one example? IIRC, the theory is that our own solar system went through a period of a high density of asteroids and comets. Could it be that Tau Ceti is just a younger system or is taking longer to get through that period?

That's exactly what I was thinking too. I wish I knew how old Tau Ceti was. The results here are mostly biased, because we only know with detail one solar system.

Crimson
2004-Jul-03, 03:24 PM
According to this thread, (http://badastronomy.com/phpBB/viewtopic.php?t=9107) Tau Ceti is twice as old as the Sun. It also has a lower metallicity.

Brady Yoon
2004-Jul-03, 07:36 PM
I think the number of asteroids and comets depends on if the star system has a number of gas giants. Solar systems with no gas giants would have more asteroids because they could easily remain in orbit. Of course, if gas giants have been detected around Tau Ceti, my hypothesis is invalid. :)

tracer
2004-Jul-03, 09:45 PM
According to this thread, (http://badastronomy.com/phpBB/viewtopic.php?t=9107) Tau Ceti is twice as old as the Sun. It also has a lower metallicity.
That low metallicity makes the presence of all those comets and asteroids somewhat puzzling. Where did the comets and asteroids get the carbon, oxygen, iron, etc. necessary for their formation?

Brendan
2004-Jul-03, 10:01 PM
According to this thread, (http://badastronomy.com/phpBB/viewtopic.php?t=9107) Tau Ceti is twice as old as the Sun. It also has a lower metallicity.
That low metallicity makes the presence of all those comets and asteroids somewhat puzzling. Where did the comets and asteroids get the carbon, oxygen, iron, etc. necessary for their formation?

Maybe the star didn't have as much metallicity because less of the asteroids and comets got sent into the star by planets besides the star being older and made of less metal rich stuff. :-?

Brendan

Brady Yoon
2004-Jul-03, 10:08 PM
Maybe the star didn't have as much metallicity because less of the asteroids and comets got sent into the star by planets besides the star being older and made of less metal rich stuff.

I don't know if the asteroids and comets have enough mass to contribute to the metal percentage of the Sun. This is a good hypothesis, though.

sol_g2v
2004-Jul-03, 10:15 PM
There is something odd about this story.

As others have pointed out, Tau Ceti is supposed to be an old star according to various lines of evidence, like low metallicity, slow rotation, no magnetic activity, velocity and direction indicating it comes ftom the thick disk population. How have all these asteroids hung around for so long? And even thought the article says its the first star ever found with a debris disk the same size as the sun, did they just discover this recently? It certainly can't be the first star ever found with a circumstellar disk, as IRAS found one around Vega way back in 1983, and there have lots of others since, like Epsilon Eridani, 55 Cancri, Denebola, Merak, Fomalhaut, etc. Strange that we would take until now to examine the nearest solitary G-type star.

rleyland
2004-Jul-03, 10:52 PM
I think the number of asteroids and comets depends on if the star system has a number of gas giants. Solar systems with no gas giants would have more asteroids because they could easily remain in orbit. Of course, if gas giants have been detected around Tau Ceti, my hypothesis is invalid. :)

Also, why is it "inevitable" that there would be more collisions?

One of the theories of Solar System formation, is that gravitational disturbances from the motion of large planets causes such collisions.

No gas giants .. less collisions.

The original article is pretty fluffy.

cheers,
Robert.

Excelsior
2004-Jul-04, 06:49 AM
Well some form of primitive life could still survive on planets orbiting Tau Ceti.

Padawan
2004-Jul-04, 07:51 AM
I think the number of asteroids and comets depends on if the star system has a number of gas giants. Solar systems with no gas giants would have more asteroids because they could easily remain in orbit. Of course, if gas giants have been detected around Tau Ceti, my hypothesis is invalid. :)


Interesting :),

However, if there won't be any as giants, then would there really be anything that would actually pull the comets and asteroids towards the inner parts of the system?

Padawan
2004-Jul-04, 07:55 AM
Reading Brady Yoon's post, something came into my mind,


These discs of comets, asteroids and debris, would they be more common in systems with low masses? i'd expect fewer of those in massive star systems, because their mass would probably have been added to the star's during the formation of the star....or would the discs be as many in low mass systems, only further away from the main star?



:-k

Brady Yoon
2004-Jul-04, 08:28 AM
These discs of comets, asteroids and debris, would they be more common in systems with low masses? i'd expect fewer of those in massive star systems, because their mass would probably have been added to the star's during the formation of the star....or would the discs be as many in low mass systems, only further away from the main star?

Hmm...I don't exactly understand what you mean there. I wouldn't see how the mass of the star would affect the amount of asteroids and comets that the star system has when it was created. I see it as strictly the amount of heavy metals.


Also, why is it "inevitable" that there would be more collisions?

One of the theories of Solar System formation, is that gravitational disturbances from the motion of large planets causes such collisions.

No gas giants .. less collisions.

The original article is pretty fluffy.

cheers,
Robert.

I said the number of asteroids and comets, not the amount of collisions. There would be more collisions, I guess, but that would decrease the amount of asteroids and comets, by impact and gravitational slingshots that send them into deep space.

Maybe the Tau Ceti system has either very small terrestrial planets or no large planets at all, so this mechanism couldn't have taken place... :-k

Crimson
2004-Jul-05, 09:34 PM
Why Intelligent Life Needs Giant Planets (http://KenCroswell.com/whyintelligentlifeneedsgiantplanets.html).

ToSeek
2004-Jul-06, 04:19 PM
Tranquil environment around Earth may be unusual (http://www.spaceflightnow.com/news/n0407/05tauceti/)


"We will have to look for stars which are even more like the Sun, in other words, ones which have only a small number of comets and asteroids. It may be that hostile systems like Tau Ceti are just as common as suitable ones like the Sun."

rleyland
2004-Jul-06, 11:45 PM
Also, why is it "inevitable" that there would be more collisions?

One of the theories of Solar System formation, is that gravitational disturbances from the motion of large planets causes such collisions.

No gas giants .. less collisions.

The original article is pretty fluffy.

cheers,
Robert.

I said the number of asteroids and comets, not the amount of collisions. There would be more collisions, I guess, but that would decrease the amount of asteroids and comets, by impact and gravitational slingshots that send them into deep space.

Maybe the Tau Ceti system has either very small terrestrial planets or no large planets at all, so this mechanism couldn't have taken place... :-k


It doesn't make sense though. Having more asteroids/comets doesn't automatically mean that there will be more collisions. If there were collisions, then the system would have cleaned itself out. That would be even more likely if the Tau Ceti system (as suggested by others) is older than ours.

Our solar system had lots of collisions early on, presumably due to interactions with the big planets. Little planets (like Saturn's moons) could well have a shepherding effect, and keep the system relatively stable.

I'd hazard a guess, that the existance of large numbers of asteroids/comets implies that there are less collisions.

cheers,
Robert.

PS. now when something does mess it up, it could get pretty hairy for our putative lifeforms ...

eburacum45
2004-Jul-07, 06:58 AM
I would like to see this old, dusty solar system in detail before declaring it uninhabitable; if there are several smaller planets, they might have cleared gaps for themselves in the dust belt.

Anyway, I would like to compare it to our version;
http://www.orionsarm.com/worlds/Tau_Ceti.html