Dark Matter

Woden

Howdy astrophysics problem sheet due in on friday. One fo the questions is related to dark matter along the lines of estimate the amount of dark matter in the solar system and compare it to the amount of non-dark matter present. Nice question fairly simple.

Just have a couple of questions about the assumptions i wish to make and whether you think they are valid.

the amount of non-dark matter in the solar system is given by the sun which takes up about 99.8% of the solar systems mass. so the mass of the solar system is in the order of 10^30 kg i think

now for the estimate of the dark matter. i was going to use the estimate for the dark matter in the galaxy and just consider the solar system a small version of the galaxy and use that.

For example the amount of luminous matter in the galaxy is considered to be 10-15% So i was going to assume that in the solar system about 85% of the mass must be dark matter just like for the galaxy

Does this seem reasonable?

cheers

data

Capt'n Midnight

In a word NO.

Dark matter is what attracts Galaxies (or is it clusters) to each other.

If there was that much dark matter locally it would have been deteced a long time ago - eg: shortly after the implications of newtowns announcement of the inverse square law were understood...

Woden

i need some type of estimation for the amount of dark matter in the solar system.

are you referring to the fact that it is thought that the dark matter sits in a halo around the galaxy and that is what is attracting us to other galaxies.

Would you assume that the mass of dark matter in the solar system is negligble?

albertw

Originally posted by Dataisgod
i need some type of estimation for the amount of dark matter in the solar system.

are you referring to the fact that it is thought that the dark matter sits in a halo around the galaxy and that is what is attracting us to other galaxies.

Though its not strictly confied to the galactic halo. Some High Velocity HI Clouds are known to lie beyond the halo and they have been calculated to require dark matter.

Would you assume that the mass of dark matter in the solar system is negligble?

It would be negligible I imagine. The planets move as expected without any requirment for dark matter in the calculations.

However there may be some:
http://www.arxiv.org/PS_cache/astro-ph/pdf/0211/0211067.pdf
Mirror matter in the Solar system:
New evidence for mirror matter from Eros

http://www.arxiv.org/PS_cache/astro-ph/pdf/9806/9806165.pdf
A New Solar System Population of WIMP Dark Matter

The amount of matter taken up by neutrinos is also fairly debatable, since the mass of the neutrino is still not certain. And complicated even further by neutrino oscillation. Just mentioning that as it was suggested as a solution to dark matter a while ago.

hth,

Cheers,
~Al
--
www.irishastronomy.org

Woden

hi thanks for the replies and info i was pointed to a formula in the notes which allows the amount to be determined based a a spherically symetric solar system. It works out about 10^18 kg 12 orders of magnitude less then that of the sun and about 10000 times less mass then that of pluto so yes its fairly negligble

cheers

data