Where was the supernova that created the Solar System?

[Baby Astronaut]

1. your said (the supernova matter thrown out) "It will slow because there is some friction in space." Are you saying relative to the stars in the Milky Way it will slow?

 

2. I am traveling to a near by star in my space ship. I am almost half way there traveling at .99 relativistic speed with two light years to go. I shut down my propulsion system. Relative to my destination star, will my speed slow down?

I will attempt to answer these best as I can. Someone will likely correct me if I'm wrong (decent chance of both).

 

1. Subatomic particles pop in and out of existence in space, besides other factors. Space is not a vacuum as is widely believed.

 

Quantum theory sets limits for the best possible quality of vacuum, predicting that no volume of space can be perfectly empty. [source: Wikipedia]

 

2. Not quite sure, but my guess is the closer to your destination, the less space "friction" you might encounter.

 

Again, I'm not studied enough on these details make accurate judgments.

[Klaynos]

Please bear with me as this is making my head hurt. I will try to ask a simple question that has a yes or no answer. I really am not trying to be a pain. Klaynos is not the only one with much more physics knowledge then me so any one that can answer in layman terms please chime in.

 

I'd rather you asked questions and understood than not

 

Since the Milky Way stars are fairly constant in the short term I will use them as a reference point. Lets try to ignore gravity for this question.

 

So, the frame we've selected is the rest frame of the Milky Way...

 

1. your said (the supernova matter thrown out) "It will slow because there is some friction in space." Are you saying relative to the stars in the Milky Way it will slow?

 

Possibly, the star will probably start out with a velocity that is not zero in the Milky way rest frame, as the probability is that the star forming region is at rest (with the milky way). An easier way of looking at this imo is to use the rest frame of the star forming region, which is where I'd assume the initial velocity mentioned above is measured from, and in that frame it will slow because the majority of matter 'locally' is pretty much at rest with that frame, or at least moving slwoer in that frame than the star.

 

2. I am traveling to a near by star in my space ship. I am almost half way there traveling at .99 relativistic speed with two light years to go. I shut down my propulsion system. Relative to my destination star, will my speed slow down?

 

.99c relative to the star I assume?

 

Yes your speed will slow down relative to the star. Space is full of dust, this dust will not be moving at .99c in the same direction as you and will there for hit the front of the ship slowing it down. there will also be some photon pressure from the star, as photons have momentum, this will be negligible at that distance though.

[padren]

Over the 5 billion years (or 1.6E17 seconds) that our sun has been around, this object can have moved away approximately 1.6E17 * 500 km = 7.9E19 km away, if it would have had a constant linear velocity. That's the equivalent of over 8 million light years.

 

I also know that the escape velocity for the milky way is 1000 km/s (approx.) so the object is likely to be still around somewhere in the galaxy. I just wanted to point out that it can be practically anywhere if we started off with a phenomenon ("kick") like I just mentioned.

 

Just a thought: Since most stars pre-supernova are in orbit around the galactic hub, isn't there also a good chance that a 500km/s shift in velocity has sent it into a decaying (or decayed) orbit or, spiraling out to eventually leave the galaxy?

 

I am not sure the odds are of it actually leaving or falling into the center in 30 orbits, I imagine it could also throw it's orbit into a radical path, slingshoting the core in one and ending up in a wide elliptical orbit... though I've never heard of this phenomenon being observed so it's just a a thought.

 

Is this possibility very probable?

[CaptainPanic]

That brings up a question I have had for awhile. So, while we have all these great minds together:

Will this speed (in relationship to it's starting point) be maintained? Or will it eventually come to rest in it's current location. It seems the frame it is in would require sustained power to maintain speed from an observers prospective. So would E=MC^2 eventually bring it to rest in its current location?

 

If you are in a gravity field (centered around the center of the galaxy) then it costs energy to move away from the center. Since any possible straight line eventually will move away from the center, the object will certainly be losing energy (kinetic energy) as it moves away.

 

It's like rockets that we shoot into space. With enough speed to get into orbit, you'll stay there (in orbit). The higher the initial velocity, the higher the orbit.

 

Therefore, it is likely that objects at the peaceful edge of the galaxy (where we find ourselves) will be relatively calm compared to the center of the galaxy. That is regarding the amount of stars and heavy objects and also the velocity that these have.

 

In other words, the most likely case is that the heavy objects have found higher orbits. I'm not sure if many stars have elliptical orbits through the galaxy (like some asteroids or other space rocks have in our solar system).

 

[Or would after reaching relativistic speed in your space ship, would you have to maintain power to maintain speed (relative to your starting point)?

 

Edit - This does pertain to the OP since it could explain the distribution of heavy elements.]

If you have speeds of a significant fraction of c (light speed, 2.99E8 m/s), then you are going so much faster than the escape velocity of the galaxy (as previously mentioned: approx. 1000 km/s) that you might as well ignore the differences in velocity as you pass the heavy objects. Only at extreme close proximity to extremely heavy objects will you encounter problems.

 

Just a thought: Since most stars pre-supernova are in orbit around the galactic hub, isn't there also a good chance that a 500km/s shift in velocity has sent it into a decaying (or decayed) orbit or, spiraling out to eventually leave the galaxy?

 

I am not sure the odds are of it actually leaving or falling into the center in 30 orbits, I imagine it could also throw it's orbit into a radical path, slingshoting the core in one and ending up in a wide elliptical orbit... though I've never heard of this phenomenon being observed so it's just a a thought.

 

Is this possibility very probable?

I think others mentioned that for most stars, only the position is known, but not the velocity or direction. There is another thread (also active right now) deals with mapping the universe in real time.

Since we don't know the velocity and direction of most stars/objects in space, we should conclude that we cannot answer the last question with measurements. But since the escape velocity of the galaxy is not approaching c, it should be possible to permanently leave the galaxy.

Edited January 9, 2009 by CaptainPanic

[Sisyphus]

In case it isn't clear, when people say you'll "slow down," it's more accurate to say that you'll accelerate to a closer reference frame to the average in the Milky Way. And you'll do this because of collisions with objects and gravitational influences, not because there is some inherent tendency to make objects move at the same velocity. There is not inherently a force needed to "maintain velocity," since every object is already at rest in its own reference frame. And it is meaningless to say that an object has a certain velocity without also specifying the reference frame in which it has that velocity.

 

...just so we're clear.

[CaptainPanic]

Umm... I prefer to use the center of the galaxy as a reference point, and then draw a x, y, z line through that... would that be a problem? The whole changing reference frame thing is a bit beyond me... but I am aware that the center of the galaxy is not at the position where we observe it, since it took thousands of years for the light to reach us. Still, in this discussion, the "center of the galaxy" seems like the logical point from where we'll define things like direction and velocity. Or is there a reason not to do this?

 

I found an interesting article regarding "Runaway stars" that have been found by Hubble:

http://www.redorbit.com/news/space/1619375/hubble_finds_runaway_stars_going_ballistic/index.html

These stars don't have the enormous speed of 500 km/s, but in stead "merely" travel at >180,000 kilometers an hour (50 km/s)... still, that's pretty fast... By the way, Earth rotates around the sun at about 30 km/s... which is also pretty fast

 

distance from the sun: 0.15E12 m.

Orbit: 2*pi*0.15E12 m

Velocity: 2*pi*0.15E12/(365*24*3600) = 30E3 m/s, or 30 km/s.

[Klaynos]

We probably don't want to use x,y,z coords then, it'll be easier if we go for z, r, theta. And if we allow the frame to rotate with the average rotational frequency of the galaxy...

[CaptainPanic]

We probably don't want to use x,y,z coords then, it'll be easier if we go for z, r, theta. And if we allow the frame to rotate with the average rotational frequency of the galaxy...

 

Umm, yeah That would be more useful than x, y and z.

I guess you mean polar coordinates? I learned different letters, but the idea is, of course, the same.

 

What's the "average rotational frequency of the galaxy"??

Stars close to the center can orbit in less than 16 years:

 

One particular star, known as S2, orbits the Milky Way's centre so fast that it completed one full revolution within the 16-year period of the study.(Source)

Of course, we (earth, and our sun) take a bit longer.

[Klaynos]

Umm, yeah That would be more useful than x, y and z.

I guess you mean polar coordinates? I learned different letters, but the idea is, of course, the same.

 

Yeah, sorry I should have defined them, am a tad tired atm...

 

What's the "average rotational frequency of the galaxy"??

Stars close to the center can orbit in less than 16 years:

 

Again my poor wording, have the frame rotating with the average at your radius. So if you look inwards (or outwards) on average the stars are stationary.

 

Of course, we (earth, and our sun) take a bit longer.

[NowThatWeKnow]

In case it isn't clear, when people say you'll "slow down," it's more accurate to say that you'll accelerate to a closer reference frame to the average in the Milky Way. And you'll do this because of collisions with objects and gravitational influences, not because there is some inherent tendency to make objects move at the same velocity. There is not inherently a force needed to "maintain velocity," since every object is already at rest in its own reference frame. And it is meaningless to say that an object has a certain velocity without also specifying the reference frame in which it has that velocity.

 

...just so we're clear.

 

Thank you, I can relate to what you say. One thing that is puzzling is the uniformity of the expansion of the universe since you say "...not because there is some inherent tendency to make objects move at the same velocity." I take that as saying things would be all over the place (without gravity) yet we observe Hubble's law at work. It is hard for me to ditch the view of a fabric of space to synchronize it all.

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Merged post follows:

Consecutive posts merged

After looking up some statistics we can look at heavy element planets from a different angle. Just a thought and not a theory.

 

There are at least 200 billion stars in the Milky Way and probably many more.

 

The latest figures used in the drake equation says there could be heavy element planets around 60% of the stars, maybe more. That says 120,000,000,000 stars have planets

 

The universe is a little over 13 billion years old but stars and supernovae were not present in the very beginning.

 

We observe about 2 supernovae every 100 years in the Milky Way. That would be about 260,000,000 in 13 billion years.

 

That would come up with one supernova for every 461 stars with heavy element planets.

 

The question is would one supernova provide enough heavy elements to support that number of solar systems with planets? If not, it had to come from somewhere else.

Edited January 9, 2009 by NowThatWeKnow
Consecutive post/s merged.

[CaptainPanic]

Again my poor wording, have the frame rotating with the average at your radius. So if you look inwards (or outwards) on average the stars are stationary.

If you look inwards, the stars in our galaxy "overtake" us. Same like the planets Mercury and Venus - they orbit the sun much faster than us. Mars and the giant planets are slower. None of them seem stationary. And it's the same thing for stars in the galaxy. They just seem stationary for observers because (as was previously mentioned) the majority of stars don't orbit so fast. So, in a human life it all seems stationary, but in a different time frame, like millions of years, the inner stars orbit faster than us. The ones further from the center than us orbit slower than us.

And then there are the random movements that should be taken into account. What I described goes for the average speeds.

[Jacques]

The ones further from the center than us orbit slower than us.

Not exactly true. Look at Galaxy rotation curve

Further than a certain distance from the center the rotation curve is constant.

[CaptainPanic]

Not exactly true. Look at Galaxy rotation curve

Further than a certain distance from the center the rotation curve is constant.

 

That is just odd! Thanks for the link, it's very interesting

 

And wikipedia seems to suggest that the phenomenon is not even understood very well. (I translate any proof of dark matter as "not yet completely understood").