Earth- sun size

kaplumbaga | 19:20 Wed 14th Feb 2007 | How it Works

11 Answers

What would happen if the Sun were smaller than the Earth?

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McNoodle

It would rotate around us - if it was small enough to be affected by our gravity, and if you removed all the other planets.

McNoodle

...I think...

fo3nix

That depends. Are you thinking that the Earth and other planets may spin off?

Gravity is due to the mass of the object, not its physical size. So, this means that density is important -- an object can have a high density if it has a high mass in a compact volume. If you have another object with the same mass but a bigger size (or volume in 3 dimensions), then it'll have a lower density.

If the Sun suddenly lost a lot of its density (and was less dense than Earth), then it would no longer continue to rotate around the Sun. What would actually happen is very complicated to model exactly, but essentially Jupiter is the next massive object near us, so we will be attracted to that slightly. Other objects such as Mars and Venus will also have some effect.

McNoodle

...correction - if it was to become less dense than us - possibly due to it's size - it would rotate around us, if you took all the other planets out of the equation. Otherwise, as fo3nix says, a very complicated model to demonstrate.

Hammer Head

'its size' not 'it's size'.

Clanad

To further support fo3nix's theory, it's known that only stars, such as our sun, that have high iron content are able to accrete planetary systems from the primoidal gas disk from which the star formed in the first place.

"Astronomers have noted that only 5 percent of stars have planets, but that's not a very precise assessment," said Debra Fischer, a research astronomer at the University of California, Berkeley. "We now know that stars which are abundant in heavy metals are five times more likely to harbor orbiting planets than are stars deficient in metals. If you look at the metal-rich stars, 20 percent have planets. That's stunning."

"The metals are the seeds from which planets form," added colleague Jeff Valenti, an assistant astronomer at the Space Telescope Science Institute (STScI) in Baltimore, Md.

The problem with the Jupiter scenario is, however, due to it's low density. Although it's the most massive planet it is less dense than Earth. In fact, due to its composition, it's thought to be a failed star... that is, it didn't reach the critical density needed to trigger fusion and make our Sun system binary in nature (thankfully advantageous to us, no?)...