Could a star not have planets ?

[Sunny129]

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.

its easy to argue that by definition, an object cannot be called a planet if it does not orbit a parent star. but that's not really what the OP was asking - the OP was asking if a star can be without planets, not if a planet can be without star(s).

regardless, i'll entertain your conjecture...but you'll see that we're arguing semantics and technicalities. planets can be gravitationally "flung" from their stable orbits around a star, just as Kuiper Belt objects and Oort Cloud objects (comets, meteors, asteroids, etc.) can be disturbed from their very distant, slow, and stable orbits about the solar system. likewise, asteroids from the asteroid belt between Mars and Jupiter can occasionally be pulled out of the asteroid belt by gravitational interaction with a planet. so does that mean that a planet that once orbited a star but was flung from the parent star's system in some sort of gravitational interaction and now wanders the galaxy alone is no longer a planet? we know such objects exist, but how do we categorize them?

 

[Howard]

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.

Also equivalent to 3.7 Graces.

 

[pw38]

its easy to argue that by definition, an object cannot be called a planet if it does not orbit a parent star. but that's not really what the OP was asking - the OP was asking if a star can be without planets, not if a planet can be without star(s).

regardless, i'll entertain your conjecture...but you'll see that we're arguing semantics and technicalities. planets can be gravitationally "flung" from their stable orbits around a star, just as Kuiper Belt objects and Oort Cloud objects (comets, meteors, asteroids, etc.) can be disturbed from their very distant, slow, and stable orbits about the solar system. likewise, asteroids from the asteroid belt between Mars and Jupiter can occasionally be pulled out of the asteroid belt by gravitational interaction with a planet. so does that mean that a planet that once orbited a star but was flung from the parent star's system in some sort of gravitational interaction and now wanders the galaxy alone is no longer a planet? we know such objects exist, but how do we categorize them?

There had to be a star there for your planet to be flung into space from so he's right even though the topic wasn't about what he answered with.

 

[Sunny129]

There had to be a star there for your planet to be flung into space from so he's right even though the topic wasn't about what he answered with.

is he? of everything i've seen/read about these "rogue" planets (which admittedly isn't much b/c despite knowing of their existence, we've only actually discovered and detected a handful of them, maybe fewer), scientists still seem to refer to them as planets. besides, calling it an asteroid b/c it no longer orbits a star and wanders free doesn't exactly make sense either b/c asteroids, like planets, are a result of star formation...and asteroids, like planets, are born orbiting a star. so if an asteroid that once orbited a star but was gravitationally "flung" out of the solar system and now wanders free is still referred to as an asteroid, then perhaps that's why we still see scientists refer to rogue planets as planets...for now anyways, until they find a better way to classify these objects.

on an interesting note, its estimated that there are twice as many "Jupiter" size/mass rogue planets wandering the galaxy than there are stars in the galaxy. also, some of these rogue planets did in fact form in free space (and not around a star initially). the IAU has suggested calling these objects sub-brown dwarfs since they don't exactly comply with planetary requirements. just some food for thought...

 

[pw38]

Well, there's a difference between a failed star and a Jupiter size planet. These sub-stellar objects for whatever reason weren't able to achieve nuclear fusion whereas Jupiter amassed itself in formation around a true star. There's a distinct difference. They aren't a "planet" anymore than Jupiter is a failed star.

 

[Revolution 11]

Sunny129, I wasn't trying to answer the OP but instead to show that there is no "chicken or egg" argument concerning planets and stars. The International Astronomical Union states that for the solar system, a planet must orbit the Sun, among other requirements.

I am not insisting that this is the definition for all planetary bodies. This does not apply to outside our system of course.

There are some scientists that don't believe in the IAU definition. I myself have problems with the dwarf planet label. A dwarf star is still a star but a dwarf planet is not a planet according to the IAU.

The IAU definitions are not perfect, but I don't see a better alternative yet.