The Astronomy Thread

They need to make up their fucking minds already. May have survived, could have survived, debris field, zombie comet.


Anyone else fascinated at the forces involved to make something going that fast turn so abruptly? That's if that's the comet and not debris of course.

Tuco_sl said:

get ready for that avatar abe

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SCIENCE BITCH! Love shit like this.

Yeah, that gif is pretty swell.

So, what's the story? Any expectation that we'll be able to see something in a couple of weeks? And by "see something" I mean clearly with the naked eye.

Moogalak_sl said:

What's all the other moving stuff in that gif? Other roids/comets?

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I would imagine a combination of other asteroids, planets etc. and probably a lot of inconsequential dust and interference.

Saying the comet survived would be like saying a car ran through a crusher survived. Yeah, most of its still there, but it sure as hell isn't a car anymore. ISON is dead. It's not like it was going to magically poof.

The sun found out how many licks it took to get to the center of ISON and then did what all humans do: chuck the remnants and viola space garbage!

Abefroman_sl said:

They need to make up their fucking minds already. May have survived, could have survived, debris field, zombie comet.


Anyone else fascinated at the forces involved to make something going that fast turn so abruptly? That's if that's the comet and not debris of course.

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In a system where Object_01 (a planet or the sun) is millions or billions of times more massive than the Object_02 (the comet), the gravitational force required to alter the trajectory of the minor object doens't change depending on Object_02's mass. The trajectory of a speck of dust or of a comet traveling at the same speed will be altered (almost) in the same way. I say almost because there are other Relativity factors, but for simple orbit calculations they are neglectible

so, talking about the comet or debris is basically the same thing

why this? because inertial force and gravimetrical pull balance out. That's why to escape the gravity of a planet you talk about escapevelocity. That's the speed an object need to reach to never be pulled back to the planet surface. And it's the same for a speck of dust, for a person, a rocket or a comet (in Earth case, 11,2km/second on the surface. For the sun it's 617.7km/second)

The trajectory of a speck of dust or of a comet traveling at the same speed will be altered (almost) in the same way. I say almost because there are other Relativity factors, but for simple orbit calculations they are neglectible

so, talking about the comet or debris is basically the same thing

why this? because inertial force and gravimetrical pull balance out.

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It's kind of a bad example. Especially when we're talking about comets because comets have a tail made up of dust and ice. In space there is no air or anything for the 'tail' to drag against, but it's trailing behind the comet instead of hovering around it. It's because the sun is constantly emitting radiation, known as solar wind, this is applying pressure to the dust and vapor which comprises the comet's tail which blows it away. So a piece of dust orbiting around the sun would just be blown away from it like the comet's tail, not really orbiting around.

But otherwise yeah F = m x a = G x m x m2 / R^2, if you solve for a, you find your motion doesn't depend on your mass at all.

So what you guys are really saying is

Tuco_sl said:

617.7km/second? Shit, the sun is a big mother fucker.

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it depends on the prospective....

in the first picture? yes it is

in the second picture ? not so much

the funny thing is Canis Majoris' escape velocity is less than the Sun's

I want to say that doesn't sound right, but I don't know enough about stars to correct you.

Behemoth star to begin with that is now at the end of its life cycle? So we can expect Canis Majoris to go supernova sometime within the next million years or so?

The scale diagram also helps put in perspective why it is so difficult to find actual Earth sized planets around a distant star.

It's because VY Canis Majoris has an extremely low density. It's a star that's at the end of its life and has swollen up to an extreme size. Something similar will happen to our sun -- it'll puff up multiple times it's current size but it's mass will be (about) the same.

Big Phoenix_sl said:

Exactly. Saturn has slightly lower gravity than we do.

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You mean density? Because Saturn is more massive than Earth and thus has bigger gravitational pull. Escape velocity is 35.6 km/s for example. However the density of Saturn is less than water.