Is Sun a binary system?

Erik
Erik
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RE: RE: @Bikeman: In this

Quote:
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@Bikeman: In this article it states "part of the WISE mission is to search for brown dwarfs, and NASA expects it could find one thousand of the dim stellar objects within 25 light years of our solar system." Why do you believe that WISE would not be able to find any?

I can't remember where I got that idea but it is rubbish: You are right, WISE would have a very good chance to catch even a brown dwarf "Sun b".

No worries. I get the occasional mental "turned around" on occasion.

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As for the discussion about the seriousness of the "Nemesis" hypothesis:

I think this article might be informative: (http://www.astrobio.net/exclusive/3427/getting-wise-about-nemesis

It does list some "real" scientists who are willing to consider the possibility of a companion red of brown dwarf to our sun. E.g. the article cites that Richard Muller proposes a "Nemesis" at a distance of ca 1.5 ly from the sun and still gravitationally bound to it, while another scientist, John Matese, suggests a distance of just 1/3 ly.

Looking back, many scientists seem to regret that the speculative companion star of the sun is now so closely linked to the idea of a "bringer of mass extinction", and have even suggested to give it (if it exists :-) !) a less emotional name: "Tyche", to take this doomsday aura off this proposed object.

CU
HB

I'm leaning toward "Fama", the Roman goddess version of Greek "Osaa/Pheme". Goddess of rumor, report and gossip. :D As you say, "if it exists". It would be very interesting if proved true, particularly to have a star closer than Proxima Centauri's 4 or so light years away.

tullio
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NASA says that the NEOWISE

NASA says that the NEOWISE mission has discovered 134 Near Earth Objects previously unknown, I thing they are far more dangerous than any Nemesis star.
Tullio

Matt Giwer
Matt Giwer
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RE: Matt Giwer: What is so

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Matt Giwer:
What is so curious about a brown dwarf, which crosses the asteroid belts at the outer border of our solar system deflecting asteroids and comets by its gravitational power?

The asteroid belt is between Mars and Jupiter which is not the outer edge.

The issue is the imagined periodicity of 26 million years as I described.

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And who tells us that your calculation concerning the possible orbit of NEMESIS is right ?

You may redo the calculation if you wish. It is as old as Newton and is his main claim to fame. There is no magic. Orbital mechanics is the same for everything.

Matt Giwer
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RE: NASA says that the

Quote:
NASA says that the NEOWISE mission has discovered 134 Near Earth Objects previously unknown, I thing they are far more dangerous than any Nemesis star.
Tullio

You might want to drop in on the orbit@home project.
http://orbit.psi.edu/
As I read it their primary goal is to get an idea of the order of magnitude of the number, density and size of NEOs. Fact is if an impactor is discovered tomorrow even Bruce Willis can't save us. But with this data we could get some design parameters for a future response. If, very big if, nukes can help this can give the size needed. Seeing their orbits we get the delta V needed to get the nuke to match orbit. And with both we get the size and fuel requirements.

Very simplistic explanation but it is necessary information we do not have. The project is still not in the production phase so you can just sign up and join the discussion. They will send enough old WUs to qualify you to participate.

Matt Giwer
Matt Giwer
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I looked into this a bit

I looked into this a bit further.

Extinct Mammals, an encyclopedia of species that have disappeared in human history, Ross Piper, Greenwood Press, 2009, ISBN: 978-0-313-43987-4

He posits we are now in the midst of the 7th major extinction event. In the introduction he recounts the six and only six recognized extinction events in the last 490 million years. These are the six recognized today. Obviously they have no 26Myr periodicity -- 490/6 26 -- nor any kind of periodicity.

tullio
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Asteroid CQ1 2011 made a

Asteroid CQ1 2011 made a close pass (5480 km) over the Pacific Ocean on February 4. It was the closest approach ever recorded for a non impacting object. Its diameter was about one meter.
Tullio

Matt Giwer
Matt Giwer
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RE: Asteroid CQ1 2011 made

Quote:
Asteroid CQ1 2011 made a close pass (5480 km) over the Pacific Ocean on February 4. It was the closest approach ever recorded for a non impacting object. Its diameter was about one meter.
Tullio

Which is obviously more an attribute of being able to detect rather than a close approach. We are not looking at the entire night sky every night. In fact there is some telescope coming on line that will look at a rather small fraction every three nights.

It is interesting that as soon as some people started looking they started finding things. Not like one a month, in perspective not as fast as finding planets around other stars, but still enough to push for funding.

There are obviously more than a few coming close. But as I have observed things that regularly pass close have had millions of chances to hit us so are not likely prospects. So it is the longest period objects that have the greatest chance of hitting us but the longer the period the fewer chances.

I don't remember where I came across it but there is a compilation of the objects that are known some where on the web. But clearly the rate of discovery indicates we have no idea of the statistics on their number and size.

Rod
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Potential Dangerous Asteroids

Potential Dangerous Asteroids (PHA's)

There are some who can live without wild things and some who cannot. - Aldo Leopold

Matt Giwer
Matt Giwer
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RE: Potential Dangerous

Yes. The closest of the close http://www.minorplanetcenter.org/iau/lists/PHACloseApp.html is Apophis at 0.0002378 AU. The earth's radius is 0.00004347 AU. That gives a target area of 0.00000000593 sq AUs. Apophis can pass any place through a cross-section of 0.00000017756 sq AUs resulting in 1 chance in 30 of hitting. The next closest is about 50 times less likely or 1 in 1500.

Of course the next step is a risk assessment. What is the chance of something taking out a major city? The surface area of the earth is about 200 million square miles. Divide the area of a big city, say 100 sq mi. by that number to get a potential damage of 1 in 2 million. Of course being within a 100 of such an impact is probably lethal so that isn't the entire answer but one should guard against piling on consequent disasters else one can quickly get to life on earth.

On the other hand there are nearly 1200 potentials on the PHA list so those numbers are not a unlikely as they seem.

The other side of it is that the closer they pass the more earth perturbs their orbit so if there were a "perfect" knowledge now it will rapidly become imperfect. Which gets us back to getting a handle on the statistics of what we do know. Let their orbits be perturbed by a close pass the overall statistics should remain about the same over a longer period than we need worry about. By that I mean in a century or three our only problem with them should be adjudicating conflicting mining claims.

mikey
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RE: The other side of it is

Quote:
The other side of it is that the closer they pass the more earth perturbs their orbit so if there were a "perfect" knowledge now it will rapidly become imperfect. Which gets us back to getting a handle on the statistics of what we do know. Let their orbits be perturbed by a close pass the overall statistics should remain about the same over a longer period than we need worry about. By that I mean in a century or three our only problem with them should be adjudicating conflicting mining claims.

And of course any change in the PHA's orbit could cause it to collide with something else long before it returns to our little neck of the Universe.

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