Double Nucleus of the Andromeda Galaxy, M31
- [Right] HST View of Andromeda's Galactic Nucleus
- A NASA's Hubble Space Telescope image of a "double nucleus" in
the giant spiral galaxy in Andromeda, M31.
Each of the two light-peaks contains a few million densely packed
stars. The brighter object is the "classic'' nucleus as studied
from the ground. However, HST reveals that the true center of the
galaxy is really the dimmer component.
One possible explanation is that the brighter cluster is the
leftover remnant of a galaxy cannibalized by M31. Another idea
is that the true center of the galaxy has been divided in two by
deep dust absorption across the middle, creating the illusion of
This green-light image was taken with HST's Wide Field and
Planetary Camera (WF/PC), in high resolution mode, on July 6,
1991. The two peaks are separated by 5 light years, The Hubble
image is 40 light years across.
- [Center] Ground View of Andromeda Galaxy Core
- The nucleus is at the center of the bulge of M31, a smooth system
of old stars. The bulge is apparent as the bright center of M31
in standard pictures of the galaxy. Individual points of light
are globular star clusters each containing several hundred
thousand stars. This ground-based telescopic image does not
resolve the double nature of the nucleus.
The background of the present picture is dark only because the
contrast has been adjusted to show the full detail in the
nucleus, which is much brighter than the surrounding bulge.
- [Left] Ground View of Andromeda Galaxy
- One of the closest neighbors to our own Milky Way galaxy, M31
dominates the Local Group, a small
group of galaxies of which our own Milky Way
is a member. M31 can be seen with the naked eye as a spindle-shaped
"cloud" the width of the full moon.
Credit: T. R. Lauer (NOAO), NASA
A magnification of the double nucleus of M31.
The HST has investigated globular cluster G1,
the most luminous globular of the Andromeda galaxy, and the whole
Last Modification: January 31, 2001