Millennium Star Atlas

Millennium Star Atlas

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Encyclopedia
The Millennium Star Atlas was constructed as a collaboration between
a team at Sky & Telescope
Sky & Telescope
Sky & Telescope is a monthly American magazine covering all aspects of amateur astronomy, including the following:*current events in astronomy and space exploration;*events in the amateur astronomy community;...

 led by Roger Sinnott, and the European Space Agency's
Hipparcos
Hipparcos
Hipparcos was a scientific mission of the European Space Agency , launched in 1989 and operated between 1989 and 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions of celestial objects on the sky...

 project, led by Michael Perryman. It was the first sky atlas to include the
Hipparcos and Tycho Catalogue data, extending earlier undertakings
in terms of completeness and uniformity to a magnitude limit of around
10–11 magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...

. It appeared as a stand-alone
publication, and as three volumes of the 17-volume Hipparcos Catalogue.

The 1548 charts include one million star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...

s from the
Hipparcos and Tycho-1 Catalogues, three times as many as in any
previous all-sky atlas; more than 8000 galaxies
Galaxy
A galaxy is a massive, gravitationally bound system that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component tentatively dubbed dark matter. The word galaxy is derived from the Greek galaxias , literally "milky", a...

 with their
orientation; outlines of many bright and dark nebula
Dark nebula
A dark nebula is a type of interstellar cloud that is so dense that it obscures the light from the background emission or reflection nebula or that it blocks out background stars . The extinction of the light is caused by interstellar dust grains located in the coldest, densest parts of larger...

e; the location of
many open
Open cluster
An open cluster is a group of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way Galaxy, and many more are thought to exist...

 and globular cluster
Globular cluster
A globular cluster is a spherical collection of stars that orbits a galactic core as a satellite. Globular clusters are very tightly bound by gravity, which gives them their spherical shapes and relatively high stellar densities toward their centers. The name of this category of star cluster is...

s; and some 250 of the brightest quasar
Quasar
A quasi-stellar radio source is a very energetic and distant active galactic nucleus. Quasars are extremely luminous and were first identified as being high redshift sources of electromagnetic energy, including radio waves and visible light, that were point-like, similar to stars, rather than...

s.
The non-stellar objects in the atlas are identified by type and designation. The chart scale
is 100 arcsec/mm, matching that at the focus of an 8-inch
f/10 Schmidt-Cassegrain. Star magnitudes are essentially Johnson V
UBV photometric system
UBV photometric system, also called the Johnson system , is a wide band photometric system for classifying stars according to their colors. It is the first known standardized photoelectric photometric system. The letters U, B, and V stand for ultraviolet, blue, and visual magnitudes, which are...

.
Distance labels are given for stars within 200 light-years of the Sun.
Proper motion arrows are given for stars with motions exceeding
0.2 arcsec/yr. Variable stars are indicated by amplitude and
variability type. Many thousands of already known and newly-discovered
double stars are depicted with tick marks indicating separation and
position angle.

Other major celestial atlases since 1997 have also incorporated the Hipparcos
and Tycho Catalogue data. These include Sky Atlas 2000.0 (2nd edition to
8.5 mag), the Cambridge Star Atlas (3rd edition to 6.5 mag), Uranometria 2000.0 (2nd edition to 9.7 mag),
the Bright Star Atlas 2000.0 (to 6.5 mag), and the Pocket Sky Atlas (to 7.6 mag).