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THE MILLENNIUM ATLAS

R.W. Sinnott

Sky Publishing Corp., P.O. Box 9111, Belmont, MA 02178, USA

Use of the Tycho data would provide more than one ABSTRACT

million , three times as many as are plotted in

Uranometria 2000.0, and place our atlas on a thor-

Derived from Hipparcos and Tycho observations, the

oughly mo dern fo oting. In addition, the charts could

Millennium Star Atlas is a set of 1548 charts covering

present some of the highly re ned results of the Hip-

the entire sky to ab out magnitude 11. It stands apart

parcos mission.

from all previous printed atlases in completeness to

magnitude 10 and in uniformity around the sky. The

generous chart scale has made p ossible a number of

2. STELLAR CONTENT

innovations never b efore seen in a star atlas: ar-

rows on high-prop er-motion stars, double-star ticks

conveying separation and p ostion angle for a sp e-

A preliminary scan through the 1 058 332 Tycho stars

ci c mo dern ep o ch, distance lab els for nearby stars,

revealed many thousands lying within 30 arcsec of a

and variable stars co ded by amplitude, p erio d, and

brighter companion. Because such pairs would ap-

typ e. Among the nonstellar ob jects plotted, more

p ear nearly concentric on the charts, they have b een

than 8000 are shown with asp ect ratio and

plotted as single dots augmented in size for the com-

orientation.

bined brightness. This pro cedure reduced the total

numb er of stars plotted to 1 041 728.

At the same time, these Tycho companions were

Key words: star charts, celestial atlases.

cross-checked against the list of double and multiple

stars sp eci cally targeted by Hipparcos. This allowed

a total of 22 192 tick marks to b e added to stars in

1. INTRODUCTION

the atlas to indicate companions lying between 0.1

and 30 arcsec from their primary stars.

In 1992, when software was develop ed by the author

Some 9200 variable stars are identi ed and character-

to generate star charts for Sky & Telescop e, the mag-

ized by amplitude, p erio d if applicable, and broad

azine's editorial sta b egan discussing the p ossibility

typ e. Among these are 5100 stars whose variability

of a comprehensive new star atlas. A set of plotted

was discovered by Hipparcos. For 6500 stars with

sky maps can have many features that are missing

prop er motions exceeding 0.2 arcsec/yr, arrows show

from photographic charts. These include a precise

the amount and direction of motion in 1000 .

co ordinate grid, b etter di erentiation of star mag-

Distance lab els are given for 10 260 Hipparcos stars

nitudes, numerous lab els, characteristics of variable

lying within 61.3 200 light-years of the sun.

and double stars, and nonstellar ob jects much fainter

than the magnitude cuto for stars.

The idea of a collab oration with the Europ ean Space

3. NONSTELLAR CONTENT

Agency was rst broached in early 1995, and this

led to a signed agreement in February 1996, more

than a b efore the general release of results from

The atlas plots 900 op en and globular clusters, 400

the Hipparcos mission ESA 1997. For atlas pur-

bright and dark nebulae, 500 planetary nebulae, 250

p oses the prime attraction was the Tycho data, which

quasars and BL Lacertae ob jects, and 675

would ensure a completeness for stars to ab out mag-

clusters. For 8000 individual galaxies, a ma jor goal

nitude 10 over the entire sky. Other celestial cartog-

was to show the correct orientation on the sky. Po-

raphers have not b een so fortunate. Becvar 1964

sition angles for two-thirds of these galaxies were

and Tirion 1981 had to rely on mid-20th century as-

found in the Lyon-Meudon Extragalactic Database

trometric star catalogues whose compilers had made

LEDA, as supplied by the LEDA team at the

no claims of completeness to a particular magni-

CRAL-Observatoire de Lyon France; the rest were

tude limit. Recognizing this shortcoming, Tirion etal

measured sp eci cally for this atlas from published

1987 decided to base their Uranometria 2000.0 on

images and photographs.

the 19th-century visual catalogues of F.W.A. Arge-

We encountered many surprises as the raw charts lander and colleagues: the Bonner

came out of the computer. For example, Tycho had and its southern-sky counterparts.

80

provided accurate p ositions for the brightest stars in

a number of op en clusters. Sometimes these stars

formed a clump that was clearly o set from the

dashed circle that was plotted from the cluster's cata-

logue p osition. As data compilers know, some of the

brightest and most familiar nonstellar ob jects have

the p o orest tabulated p ositions. We corrected such

anomalies whenever they were noticed.

4. OVERVIEW



The atlas contains 1548 charts, eachcovering a 5:4



by 7:4 region of the sky. The co ordinate grid is

that of the International Celestial Reference System,

consistent with equinox J2000.0, while star p ositions

and double-star con gurations are shown for

J1991.25. All stars are sized by V magnitude, as

derived from the Tycho B and V measurements.

T T

The atlas is b eing issued in twoversions at slightly

di erent scales. The three-volume stand-alone edi-

tion Sinnott & Perryman 1997 has a chart scale of

100 arcsec/mm. That app earing as Volumes 14{16

of the Hipparcos and Tycho Catalogues ESA 1997

has a scale of 88 arcsec/mm. Both are printed with

black stars against a white sky.

ACKNOWLEDGMENTS

This atlas would not have b een p ossible without the

close involvement of Europ ean astronomers work-

ing with the Hipparcos data. The atlas's coauthor,

M.A.C. Perryman, showed particular imagination in

helping to de ne the atlas's features; he also orches-

trated the interactions b etween R.W. Sinnott and H.

Schrijver, E. Hg, and V.V. Makarov.

At Sky Publishing Corp., E.T. Mentall researched the

p osition angles of galaxies and drafted all outlines of

large nebulae. He and I. Joson scrutinized the charts

to remove lab eling ambiguities. L.J. Robinson was

the chief technical consultant, while master illustra-

tor G. Dinderman oversaw the clarity of presentation.

S. MacGillivraywas pro ject manager under the rm's

president, R.T. Fienb erg.

Many others who played key roles are acknowledged

in the Atlas's Intro duction.

REFERENCES

Becvar, A., 1964, Atlas eclipticalis, Czeckoslovak

Academy of Sciences

ESA, 1997, Hipparcos and Tycho Catalogues, ESA

SP{1200

Sinnott, R.W., Perryman, M.A.C., 1997, Millennium

star atlas, Sky Publishing, in press

Tirion, W., 1981, Sky atlas 2000.0, Sky Publishing

Tirion, W., Rappap ort, B., Lovi, G., 1987, Uranome- tria 2000.0, Willmann-Bell