PX158 - J3 - weighing galaxies


- the orbital velocities appear constant right out to the limit of observations
- most of the mass is "unseen", known as "dark matter"
- stars are on circular orbits, balance force from gravity with centripetal force:
- eg: mass interior to the orbit of the sun in milky way:
,
- stars at the edge of the galaxy show similar velocities, giving
-
this is far in excess of all baryonic matter
-
there lies a supermassive blackhole (SMBH) in the centre of most galaxies
-
eg:
shows at -
in
, SMBH was observed in radio spectrum