galactic bulge
(bulge of many stars in the center of the Milky Way)
The galactic bulge is the bulge of stars surrounding the
Milky Way's galactic center. It is challenging to study
from our position within the Milky Way, with extinction due to
clouds in and around the bulge, and the description below is
subject to debate and future correction. The Milky Way bulge is
a bar, the center of which is about 8 kpc from
Earth (the diameter of the starry-region of the Milky Way is
on the order of 30 kpc). Dimension-determinations of the bar vary
between 3-4.5 kpc length, with other dimensions on the order of a
kpc. Some have determined it to be a pseudobulge (a flat bulge,
i.e., little or no projection from the galactic disk). There
is structure within the bulge: for example, it is suggested that
there are two bar structures of different stellar populations, i.e.,
different age and metallicity. The bars cross each other like
an X, though at a small angle, with one bar shorter than the other.
The specific characteristics of the Milky Way bulge are not rare;
other observed spiral galaxies show similar bulge characteristics.
Roughly in the center of the bulge (the galactic center) is the Milky
Way's central supermassive black hole (SMBH), Sag A*, surrounded by a
cluster of millions of stars (a compact stellar nucleus)
within a parsec of the SMBH, a region roughly as wide as
the distance between the Sun and Alpha Centauri.
The term galactic bulge is sometimes used for the bulges of
other galaxies: the term galactic is somewhat ambiguous
regarding whether it refers to galaxies in general or to the
Milky Way in particular: with "the", e.g., the galactic bulge,
typically means that of the Milky Way unless the context shows
otherwise. Also, the Milky Way's is sometimes indicated by
capitalization, i.e., "the Galactic Bulge" or "the Galactic bulge".
(Milky Way)
Further reading:
https://en.wikipedia.org/wiki/Bulge_(astronomy)
https://en.wikipedia.org/wiki/Galactic_center
http://ned.ipac.caltech.edu/level5/March16/Gonzalez/Gonzalez_contents.html
https://ui.adsabs.harvard.edu/abs/2008IAUS..245..323M/abstract
Redshift | Parsecs /Distance | Lightyears /Lookback Years | | |
~0 | 8kpc | 26.0kly | | galactic bulge |
|
Coordinates: | galactic bulge J180000-300000 |
|
Referenced by pages:
bulge
galactic center
heating
Korea Microlensing Telescope Network (KMTNet)
Roman Space Telescope (RST)
Index