Could a star not have planets ?

[Revolution 11]

How do you get a planet the size of jupiter in an orbit the size of mercury's? Exo-planet statistics show a large number of planets in this regime.

Planet detection methods are in their infancy and most exoplanets are discovered by gravitational wobbles in the star's orbit. This produces a clear bias towards large planets close to the star. Hence, the majority of exoplanets are hot, massive gas giants. (why they are not rock-based, idk)

 

[DrPizza]

Planets like those found in our solar system are made up of a lot of elements other than hydrogen, helium, and perhaps a little lithium and boron. Our planets were born from the destruction of a previously existing star. During that star's supernova, elements higher in atomic number than iron were formed.

So, in an area of space still dominated by hydrogen, I really don't see how many familiar types of planets are going to form.

 

[DominionSeraph]

Unless, of course, the 2 stars are orbiting each other, or in the case of 1 star is orbiting the other star, there would most certainly be some stranger orbits as the center of gravity of the system would constantly be shifting on those two cases.

...

Stars under acceleration?

 

[jimbo75]

How do you get a planet the size of jupiter in an orbit the size of mercury's? Exo-planet statistics show a large number of planets in this regime.

They migrate inwards.

 

[shortylickens]

Theoretically, anything is possible. There could be billions of planets just in our Milky Way. There could be no other planets.
There could be penta star systems with a hundred planets. Etc.

But, based on what we know about statistics, the universe is too vast for us to make assumptions based on the limited data we have.

 

[DrPizza]

http://www.nowykurier.com/toys/gravity/gravity.html

Have fun.

 

[DrPizza]

But, based on what we know about statistics, the universe is too vast for us to make assumptions based on the limited data we have.

What do you mean by that??

 

[pw38]

What do you mean by that??

Meaning the data set is too small to render any absolute (or even loose in this case) conclusion. The universe is just too big, the variables too many.

 

[DrPizza]

I don't agree with that. One conclusion we can reach is:
There are a shitload of stars with planets.

"The variables too many."
What variables? The "variables" which affect the formation of stars, such as the universal gravitational constant are just that - constants. It's not like there's a completely different set of laws of physics in the next galaxy over. Or, at least, I think the evidence points to the laws of physics being the same.

 

[ArisVer]

I don't agree with that. One conclusion we can reach is:
There are a shitload of stars with planets.

"The variables too many."
What variables? The "variables" which affect the formation of stars, such as the universal gravitational constant are just that - constants. It's not like there's a completely different set of laws of physics in the next galaxy over. Or, at least, I think the evidence points to the laws of physics being the same.

"There are a shitload of stars with planets". No comment.

Even though i doubt it, there could be different physics and chemical laws in different solar systems.

Nobody has been there to let us know.

 

[pw38]

I don't agree with that. One conclusion we can reach is:
There are a shitload of stars with planets.

"The variables too many."
What variables? The "variables" which affect the formation of stars, such as the universal gravitational constant are just that - constants. It's not like there's a completely different set of laws of physics in the next galaxy over. Or, at least, I think the evidence points to the laws of physics being the same.

How do you know there are a shitload of stars with planets? Because of the measly amount we've discovered so far? What makes you think we can extrapolate anything based on such limited evidence? I'm not arguing there aren't necessarily a "shit load" of stars with planets (depends on what you define as a "shit load" first, still I hope there are, it makes the universe a more interesting place) only that it's a bit naive to deduce that because our searches so far have produced a few stars with planets it's inevitable this has to be the case. Odds are you might be correct, I just don't agree with the assumptive reasoning.

Also, I didn't say there are different ways to form stars, just that there are a wide array of situations that might preclude them from forming planets. We just don't really know yet.

 

[Gibsons]

Recent estimates put the Milky Way at 50 billion planets. That's 20.6 Shitloads or 12.5 Courics.

It's in USA Today, so it has to be right.

 

[Tom]

I don't agree with that. One conclusion we can reach is:
There are a shitload of stars with planets.

"The variables too many."
What variables? The "variables" which affect the formation of stars, such as the universal gravitational constant are just that - constants. It's not like there's a completely different set of laws of physics in the next galaxy over. Or, at least, I think the evidence points to the laws of physics being the same.

That's kind of the reason I started this thread. We know some stars have planets, we do not know if there are any stars without planets.

So instead of starting from an assumption we have to prove other planets exist, it seems to me we ought to be trying to prove there are stars without planets.

If it's even possible.

 

[Biftheunderstudy]

That's kind of the reason I started this thread. We know some stars have planets, we do not know if there are any stars without planets.

So instead of starting from an assumption we have to prove other planets exist, it seems to me we ought to be trying to prove there are stars without planets.

If it's even possible.

Because a non-detection is not possible given the circumstances. All we can do is look at as many stars as we can and try to detect planets around them, then make a statistical argument based on the sensitivity of the observations.

 

[Biftheunderstudy]

They migrate inwards.

That seems like the most likely solution, though it's proven difficult to do through modelling. A couple of the graduate students in my office are working on planet formation, one of them on the migration problem.

 

[Biftheunderstudy]

Planet detection methods are in their infancy and most exoplanets are discovered by gravitational wobbles in the star's orbit. This produces a clear bias towards large planets close to the star. Hence, the majority of exoplanets are hot, massive gas giants. (why they are not rock-based, idk)

This is indeed a strong bias. However, the Kepler mission uses planetary transit events to find planets. There are also a number of direct detections. The number of exoplanets has risen dramatically in the past year or so, more statistics should shed some light on this field.

 

[Biftheunderstudy]

They already know that small dust size particles do tend to clump together in low/zero G.
There's video of an astronaught with a bag of something( i don't remember what was in it), but it is full of small particles and they start clumping together with no external actions.
I saw it on The Universe or something. If I find the video I'll post it.

This is still an active area of research. Yes you can clump dust together, but it becomes inefficient once the clumps get larger. It's not clear how the dust accretion model works before the clump size is about 10m in size. After 10m or so (I think), our accretion models can take over and you can grow a planetessimal.

The other primary theory is gravitational instability, leading to forming a large planet directly.

 

[DrPizza]

"There are a shitload of stars with planets". No comment.

Even though i doubt it, there could be different physics and chemical laws in different solar systems.

Nobody has been there to let us know.

We haven't been there, but we can observe there. i.e. all that starlight you see - we can see the hydrogen spectrum, helium spectrum, etc., to an incredible degree of precision (as well as see the degree of red shift or blue shift.) Are you suggesting that the laws of quantum mechanics which govern the frequencies of light that we observe are identical in other galaxies, but that something else is different? At the root of all chemical processes are physical processes. Chemistry is ruled by the laws of physics; in this sense, physics is the fundamental science upon which the other sciences are based. And, there are enough varied types of observations - things at a distance that match our theories of how they should look at that distance, that there's every reason to suspect that the physical laws are the same. Big example: matter vs. antimatter. We haven't been to other galaxies, yet we know that the visible galaxies are composed primarily of regular matter, not antimatter. I know of no theories that haven't been disproven that some of the galaxies are matter and some are antimatter, and that there isn't really this horrible imbalance in the universe.

As far as planets, we've only just begun to look. And, everywhere we look, we seem to be finding planets. But, (I'm not 100% certain of this), I think they're looking at stars that are more likely to have planets - stars rich in metals. Since someone wanted to know if there were stars without planets, the logical place to look would be planets formed in regions without metals or other materials that would necessarily have to have been formed in a supernova. i.e. areas that are primarily hydrogen and maybe a little helium, lithium, and beryllium.

edit: on that note, a lot of the stars that we're "looking" at, existed billions of years ago and are no longer in existence. So, for the sake of this thread, do we assume the present tense to mean present observation? Because, it's possible (but improbable) that there's an alien species that just hates planets and 5 minutes ago, just destroyed the last planets in the universe outside of our own solar system. Thus, the answer could be zero, despite our discoveries of other planets. We can't ascertain their present condition.

 

[Biftheunderstudy]

Well, to resolve a star it has to be "close". Meaning, the light is at most only a few thousand years old.

The 50 billion planets in our galaxy estimate comes from a somewhat naive extrapolation of the Kepler data. All they did was multiply the percentage of stars in the Kepler survey with planets by the total number of stars in the galaxy...

Still, a lot of planets.

 

[ArisVer]

Are you suggesting that the laws of quantum mechanics which govern the frequencies of light that we observe are identical in other galaxies, but that something else is different?

I believe that the physics laws will be identical. There could be differences depending on the size and age of other stars and their surroundings. Stars and planets may have different chemical structures and unknown chemical elements.

Based on simple probabilities i cannot rule out the possibilities that there could be stars without planets. It is not a scientific fact, but a mathematical fact.

I must say that i am not familiar enough with the terms nova, supernova, pulsar etc., meaning that i do not understand/remember the terms well enough, even though i read their basic dictionary meanings. I do have a strong opinion on how the stars and planets were made, but with some really blank points, like, "which was made first? the stars or the planets?"

 

[DrPizza]

If you go back in time far enough, the only elements that existed in the universe were hydrogen, helium, lithium, and I think beryllium. Predominantly hydrogen though. Stars would of course form first, simply based on our definition of what a planet is. The other elements were formed by fusion in stars. As far as "unknown elements" - there is, I suppose, a slight possibility. The periodic table contains a fairly significant number of elements which do not exist naturally. Or rather, if they're created naturally (supernova explosions, etc.), their half life is so extremely short that within a short time, they cease to exist. However, there is that slight possibility - it's theorized that around atomic number 125 (someplace around there; 122? I can't remember) there's an island of stability where those elements may exist for a little longer. I think the hypothesis predicts hours. Most recently, the manmade elements 113 and 115 have been discovered (with enough evidence to satisfy the IUPAC.) I think that there have been claims of ununoctium (element 118) being created - on the order of less than a handful of atoms of that element have ever existed on this planet. So, they're getting closer to this island of stability.

 

[ArisVer]

Based on simple probabilities i cannot rule out the possibilities that there could be stars without planets. It is not a scientific fact, but a mathematical fact.

Keep in mind that english is not my primary language, and i make quite a few mistakes. I also make them in my native language (greek) even though i am better at that.
To correct myself, mathematics is maybe the most pure scientific 'language' as it based only on numbers. I wanted to say that it is not a proven fact, just a mathematical fact of 1/infinity.

Dr. Pizza, if i can take you a few steps further back in time, when 'nothing' existed, my question is clear. You take it as a fact that the first elements were gases maybe based on the formation of stars.

Also, a planet is a body in space that is not a star. That includes asteroids and satellites. It is closer to the astrological definition of a planet and in contrast to a vocabulary definition that 'a planet orbits a sun'.
According to an oxford dictionary i have seen, 'the sun shines the sky during the day'. To make this simplified, the sun (a star) shines ALL the time.

 

[Tom]

a little off-topic..remember the "ether" theory of cosmology fromthe 19th century ?

What's different about 'dark energy' theory ?

 

[silverpig]

a little off-topic..remember the "ether" theory of cosmology fromthe 19th century ?

What's different about 'dark energy' theory ?

Attempts to measure dark energy have shown that it makes up ~70% of the universe and no experiment to date has disagreed with this. Granted, there is only the Hubble supernova data and the WMAP data to do this (AFAIK), but still.

Then there's the Michelson interferometer experiment which showed that there is no ether on essentially the first try.

 

[Revolution 11]

One of a planet's main requirements is a stable orbit around a star. So there can be no planets without a parent star. It'd just be a asteroid or something.