Astronomy

[deleted-318560]

Hi

I was wondering that if the Sun was twice as large (a science class question) would the Sun's gravitational pull double causing all planets to be drawn in. If the planets were drawn into the Sun, what would happen then (eg. to the Sun and Solar System)?

Thank you

Michaela
New Zealand

[deleted-315590]

Hey Michael,
I think you put this in the wrong category you might get an answer but not a very accurate one. Good question though!!
let me know if you get an answer.

[SciB]

Hi Michaela,

When you ask what if the sun were 'twice as large' are you thinking about twice the diameter or twice the volume? There's a big difference. Doubling the diameter increases the volume by 8 times. If the sun were 8 times as massive as it is now, its gravitational pull would be 8 times as great. I don't know if this increase in gravity would be able to change the orbits of the planets enough to eventually pull them into the sun. Gravitational pull increases as the square of the distance between the objects decreases, so the closer planets like Mercury, Venus and Earth would be pulled more than more distant ones like Neptune and Uranus.

I'm not an astrophysicist but I do know that if you increase the force on an object, the earth in this case, it will move faster. In other words, I predict that if the sun were 8 times as massive, the period of the earth's orbit would decrease from one year to something less. Whether or not the orbit would decay so that the earth would be pulled into the sun, I don't know. Maybe it would be like the slingshot effect that rocket scientists use to send a space craft out into space by having it speed past a planet so that the gravity increases its speed. http://www.scientificamerican.com/artic ... ngshot-ef/

Try posting on the physical sciences forum as was suggested by the previous expert. There should be experts there who are more knowledgeable about physics than we are.

Good question! Let us know what you find out.

Sybee