Spiral Galaxy NGC 1512: The Inner Rings
Explanation:
Most galaxies don't have any rings -- why does this galaxy have two?
To begin, the bright band near
NGC 1512's center is a
nuclear ring,
a ring that surrounds the galaxy center and glows brightly with recently
formed stars.
Most stars and accompanying gas and
dust,
however, orbit the galactic center in a ring much further out --
here seen near the image edge.
This ring is called,
counter-intuitively, the inner ring.
If you look closely, you will see this
the inner ring connects ends of a diffuse
central bar
that runs horizontally across the galaxy.
These ring structures are thought to be caused by
NGC 1512's
own asymmetries in a drawn-out process called
secular evolution.
The gravity of these galaxy asymmetries, including the bar of stars,
cause gas and dust to fall from the inner ring to the nuclear ring,
enhancing this ring's rate of
star formation.
Some spiral galaxies
also have a third ring -- an outer ring that
circles the galaxy even further out.
Authors & editors:
Robert Nemiroff
(MTU) &
Jerry Bonnell
(USRA)
NASA Web Site Statements, Warnings,
and Disclaimers
NASA Official: Jay Norris.
Specific
rights apply.
A service of:
LHEA at
NASA /
GSFC
& Michigan Tech. U.
