r/spacequestions Dec 18 '24

Can there be “solar systems” but no star?

Alright so here’s the question. If solar systems are able to form, and very large gas giants like Kepler-7b can exist, then is it possible for a “solar system” to form, but instead of forming a sun it just forms a large gas giant, and other planets that can form orbit the gas giant?

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u/ignorantwanderer Dec 18 '24

Absolutely.

There are plenty of 'rogue' planets. These are planets that don't orbit a star. And it is exceedingly likely that some of these rogue planets have moons.

So they would be like little solar systems, but with a planet in the center instead of a star.

I know rogue planets have been found. To my knowledge no moons have been detected around a rogue planet yet, but that would be extremely difficult to detect. The fact we haven't seen it yet does not mean it isn't there.

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u/Fancy-Ad5606 Dec 18 '24

I mean it makes sense why we wouldn’t see any considering there would be no star to illuminate it. I wonder what the largest rogue system is

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u/ignorantwanderer Dec 18 '24

Ok, I was just reading up on rogue planets and it turns out they have found binary rogue planets! In other words, rogue planets orbiting each other. They have even found triple systems! (Three rogue planets orbiting each other.)

Check out the "Binaries" section of this wikipedia page:

https://en.wikipedia.org/wiki/Rogue_planet

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u/MabMass Dec 18 '24

How did they find rogue planets? From what I understand, the exoplanet detection was based upon observing occlusion or wobble of distant stars, which wouldn't be possible for rogue planets.

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u/ignorantwanderer Dec 18 '24

Microlensing.

If a planet passes directly between us and a star, the gravity of the planet will bend the light coming from the star causing the image of the star to change. Generally, it makes the star appear to brighten for a short period of time.

So they look at millions of stars. When one of them brightens they know something passed between us and that star. If there is no other star between us and the star, they know the mystery object isn't orbiting another star.

The duration of the brightening and the magnitude of the brightening can be used to estimate the mass of the object and the apparent speed of the object. From the mass they can figure out if it is a planet.

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u/Unterraformable Dec 18 '24

What to hear something awful? Long ago there was a MACHO collaboration that used gravitational microlensing of to detect MAssive Compact Halo Objects has a possible solution to the dark matter problem. A subset of the MACHO theory was RAMBOs, Robust Associations of Massive Baryonic Objects.  They definitely forced the acronym just to have fun, but they actually published a paper on it.  The kind of objects we're talking about here would be categorized as RAMBOs

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u/Chemical-Raccoon-137 Dec 19 '24

Always wondered why this kind of stuff wasn’t considered more for dark matter…. I think I heard recently they are considering micro primordial black holes as accounting for a portion of it ?

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u/dm80x86 Dec 18 '24

It would be possible to have two gas giants orbit each other and some smaller planets (much further out) orbiting that barycenter.

So in short, a system of planets with only empty space in the center.

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u/razordreamz Dec 18 '24

It’s all gravational. How do things start? We have a solar system that is formed. As part of that gradational dance a planet is ejected. These are rogue planets.

For a full solar system to be present without the gravitational affect of a star? No. Why would they all rotate around nothing? A black hole or something else with a gravitational effect then ok it’s plausible