What happened whith the solarsystem when..

[Denis12]

Sirius A is tomorrow our sun .at the same place like our sun of course. What will happening especialy with earth itself? life,weather etc etc. And what will happening when Barnards star is our sun tomorrow? Is here somebody ho can explain this? Thanks.

[cjl]

Are you asking what would happen if our sun was suddenly the same brightness (technically luminosity)/size/mass as those stars?

If it was suddenly the mass and luminosity of Sirius A, then we would fry. It is about 25 times the luminosity of our sun, and would boil the oceans, melt the icecaps, and turn the whole earth into a desert.

If barnard's star was substituted for the sun, the earth would freeze. It only puts out about .04% of the light (in the visual spectrum) that the sun does, resulting in a tremendous drop in tempearture.

[tony873004]

You got that right.


If it was suddenly the mass and luminosity of Sirius A, then we would fry. It is about 25 times the luminosity of our sun, and would boil the oceans, melt the icecaps, and turn the whole earth into a desert.

And that's before the Earth plunged into the Sun from its increased gravity.


If barnard's star was substituted for the sun, the earth would freeze. It only puts out about .04% of the light (in the visual spectrum) that the sun does, resulting in a tremendous drop in tempearture.
And that's before the Earth escaped the Sun and distanced itself thousands of light years from any significant external heat source.

[cjl]

You got that right.

And that's before the Earth plunged into the Sun from its increased gravity.

And that's before the Earth escaped the Sun and distanced itself thousands of light years from any significant external heat source.

Very true - I forgot to account for the effects of the changed mass.

[Jorge]

While we are on the subject,

What if we rewind sol's life by let say 50% of what it is now...?

[Van Rijn]

You mean, if the sun was younger? It would be putting out substantially less light. Given our present atmosphere, the earth would be frozen over.

[Ken G]

That is actually a debated point. As the Earth was not that cold when the Sun actually was half its age, it is possible that differences in the atmosphere helped warm the Earth. But others think maybe the Sun wasn't so dim, and maybe there are other possibilities as well. It's an unsolved mystery, though the atmospheric issues may be the leading idea. Note that if it's true, there may have been a Gaia-esque regulation mechanism at play to keep the Earth temperate all this time.

Oh, and I feel I should correct one point-- if the Sun suddenly had the mass of Sirius, the Earth would not fall into the Sun, it would go into an elliptical orbit that took it closer to, but never into, the Sun. (nitpicky, yes, but a useful insight).

[antoniseb]

if the Sun suddenly had the mass of Sirius, the Earth would not fall into the Sun, it would go into an elliptical orbit that took it closer to, but never into, the Sun.

Yes, and if Barnards star were the center, the Earth and all the other planets, asteroids and comets are already going well above escape velocity for Barnard's Star so it wouldn't just be a long ellipse outbound (we would however never be thousands of light years from another star... five to ten at most. We would not even be close to escaping the galaxy).

Other side notes. 25 times the luminosity would be just right to melt Jovian ice moons (ignoring the new highly elliptical orbits). It might also be enough to remove the bulk of the atmospheres from Venus, Earth & Mars, and melt or vaporize Mercury at perihelion.

The Trojan asterods (and many other asteroids and outer moons) of Jupiter might all turn into comets. The KBOs would also fall into comet-like orbits and spew gas and dust.

Sirius B would have an impact on the particular KBOs that it was near.

[tony873004]

Oh, and I feel I should correct one point-- if the Sun suddenly had the mass of Sirius, the Earth would not fall into the Sun, it would go into an elliptical orbit that took it closer to, but never into, the Sun. (nitpicky, yes, but a useful insight).

We had a homework assignment once in Astronomy class. If Betelegeuse suddenly replaced the Sun, which planets would be engulfed? The teacher was looking for Mercury and Venus and maybe Earth. But I threw it into my simulator and determined that all planets would be engulfed in less than 1 orbit. Betelgeuse is huge and massive.

But I should have checked my facts before guessing it would be the samd for Sirius A. Although more than twice as massive, it's not much bigger than the Sun.

[Ken G]

Yeah, Sirius is not that big, or massive, that it could suck in the Earth. But you are probably right about Betelgeuse-- chances are your teacher was only thinking about the radius of the Earth's present circular orbit, not self-consistently replacing it with the elliptical orbit it would have around Betelgeuse.

[korjik]

You got that right.

And that's before the Earth plunged into the Sun from its increased gravity.

And that's before the Earth escaped the Sun and distanced itself thousands of light years from any significant external heat source.

The earth wouldnt plunge into Sirius A. It would end up on an elliptical orbit with the perhelion (is that spelled right?) much closer to the primary. This is assuming that Sirius A isnt just big enough that the close approach isnt in the star.

I think the relation is perhelion is a function of sqrt(mass) in this case. This comes from the fact that angular momentum must be conserved.

[antoniseb]

I threw it into my simulator and determined that all planets would be engulfed in less than 1 orbit. Betelgeuse is huge and massive.

The outer part of Betelgeuse is so thin that it would take many years for most of the planets to have their orbits substantially affected or be evaporated by the plunge.

[tony873004]

The outer part of Betelgeuse is so thin that it would take many years for most of the planets to have their orbits substantially affected or be evaporated by the plunge.
Their orbits would be substantially changed just from the extra mass of Betlegeuse.

But you're right. The tenous outer layers, many magnitudes thinner than Earth's atmosphere, present an interesting situation. After plunging into Betlegeuse, the planets would continue on their trajectories and exit the star. And Venus may continue to orbit the core from within the star for quite some time.

How might this affect life on Earth? Could some life survive the plunges beneath Betlegeuses photosphere? Its so thin that heat transfer wouldn't be that great through conduction. And Betlegeuse is a red star, so cooler than the Sun per square meter of surface. Might being engulfed in a star lead to an ice age?

[tony873004]

...This is assuming that Sirius A isnt just big enough that the close approach isnt in the star...
It isn't. You and Ken are right. It would would go into an elliptical orbit bringing it much closer to, but not into the star. It's orbit would be both Venus and Mars crossing.

[cjl]

Their orbits would be substantially changed just from the extra mass of Betlegeuse.

But you're right. The tenous outer layers, many magnitudes thinner than Earth's atmosphere, present an interesting situation. After plunging into Betlegeuse, the planets would continue on their trajectories and exit the star. And Venus may continue to orbit the core from within the star for quite some time.

How might this affect life on Earth? Could some life survive the plunges beneath Betlegeuses photosphere? Its so thin that heat transfer wouldn't be that great through conduction. And Betlegeuse is a red star, so cooler than the Sun per square meter of surface. Might being engulfed in a star lead to an ice age?
Based on the fact that it would be emitting phenomenal amounts of infrared, many times more than our sun, it should still fry us quite easily.

[Ken G]

And Betlegeuse is a red star, so cooler than the Sun per square meter of surface. Might being engulfed in a star lead to an ice age?
But it is still extremely hot, compared to what we like on Earth. The oceans would boil off, as would the atmosphere, etc. You are forgetting that it would fill the sky.

[tony873004]

That would be an awesome sight.

Thinking about it, its red color means it's cooler per square meter of photosphere than the Sun, but its photosphere is much larger. And its luminosity is 9400 times that of the Sun.

I was hoping for icebergs under a red-tinted sky, but instead red boiling oceans seems more likely. I guess I'll cancel my vacation plans to go there :)

[Jorge]

You mean, if the sun was younger? It would be putting out substantially less light. Given our present atmosphere, the earth would be frozen over.

Yep thats waht i ment, if a planet like dirt today was around a sol like star but mutch yougher could we survive or not.

freezing means thats probebly a nono unless the planet hat a hotter temp ealier on.

[Denis12]

And what happens when Betelgeuze is at the place of the sun? It will be a little bit warm. Is that true?

[cjl]

Considering we'd be inside the star, yes it'd be a bit warm

[Jorge]

Considering we'd be inside the star, yes it'd be a bit warm

And how would you know ;) ever been a star... i ments inside a star :lol:

for all we know we might freeze to death, the hot stuff is only a tin layer at the surface :shifty:

(oh yeah, i was joking here)