Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Dave Lev on 19/04/2018 08:33:03

Title: Why might stars and planets be ejected from the Milky Way galaxy disc?
Post by: Dave Lev on 19/04/2018 08:33:03
Why stars and planets are ejected out from the Milky Way galaxy disc?

Please see the following:

phys.org/news/2012-03-runaway-planets-fraction.html

"Seven years ago, astronomers boggled when they found the first runaway star flying out of our Galaxy at a speed of 1.5 million miles per hour."

"New research shows that the answer is yes. Not only do runaway planets exist, but some of them zoom through space at a few percent of the speed of light - up to 30 million miles per hour."
Title: Re: Why might stars and planets be ejected from the Milky Way galaxy disc?
Post by: Petrochemicals on 19/04/2018 21:04:47
Betelgeuse , the brightest star in the sky, is a runaway edjected star.

https://en.m.wikipedia.org/wiki/Betelgeuse

Gravitational attraction is one reason, similar to when hale bopp realighned its orbit and period when it passed jupiter on the way out of the solar system.
Title: Re: Why might stars and planets be ejected from the Milky Way galaxy disc?
Post by: wolfekeeper on 19/04/2018 23:46:37
Off hand I would say it's probably the slingshot effect:

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

If you have two bodies in high speed orbits around each other, ideally two black holes, or two neutron stars, they can be travelling at a significant fraction of the speed of light in their orbits. If a third body falls in, a star or a planet, they can be gravitationally accelerated to extremely high speed without tidal forces tearing them apart and flung off in pretty much any direction, mainly depending on the plane of the binary objects.
Title: Re: Why might stars and planets be ejected from the Milky Way galaxy disc?
Post by: Dave Lev on 20/04/2018 13:18:37
Thanks
Title: Re: Why might stars and planets be ejected from the Milky Way galaxy disc?
Post by: Petrochemicals on 20/04/2018 17:29:51
You wetted myappetite dave. It seems that they where supprised by the very speed of edjection. Even though this could be done by slingshot by some gravitational atrangement, it seems that they think it unlikely. A supernova explosion is what i read as the most likely
Title: Re: Why might stars and planets be ejected from the Milky Way galaxy disc?
Post by: jeffreyH on 21/04/2018 11:58:43
Don't say Betelgeuse three times otherwise it goes supernova.
Title: Re: Why might stars and planets be ejected from the Milky Way galaxy disc?
Post by: evan_au on 22/04/2018 06:08:37
It is thought that an asymmetric supernova could kick the resulting neutron star or black hole out of the galactic plane.

This does not require close proximity to 2 other bodies, which would be moderately rare given the vastness of space.
Title: Re: Why might stars and planets be ejected from the Milky Way galaxy disc?
Post by: Dave Lev on 23/06/2018 09:11:21
Thanks

However, why dark matter can't hold the stars at the Disc???
Actually, as we increase the orbital radius, we also increase the orbital sphere. This by definition increases the effective total dark matter for that orbit.
Hence, if there was dark matter, it had to keep the stars in the disc at almost any radius.
So, could it be that the ejection of stars from the disc is an indication that there is no dark matter in the galaxy?