close to the pole as Polaris is at present. The pole will
then pass through Hercules, returning to Draco and again
passing close to Thuban.
Though Thuban has been given the Greek letter ·,
it is not the brightest star in the constellation; it is
well over a magnitude fainter than Á. William Herschel
believed that it had faded in historic times, and certainly
both Tycho Brahe and Bayer ranked Thuban as of the
second magnitude but, all in all, it is not likely that there
has been any real change. The distance is 230 light-years,
and the luminosity 150 times that of the Sun.
The most interesting nebular object in Draco is
NGC6543 (C6), which lies almost midway between ‰and
̇. It is a small but fairly bright planetary nebula, with a
central star of magnitude 9.6. With a small telescope it has
been described as looking like ‘a luminous disk, resem-
bling a star out of focus’, and many observers have
claimed that it shows a bluish colour. It was the first nebu-
lar object to be examined spectroscopically – by William
Huggins in 1864. At once Huggins saw that the spectrum
was of the emission type, so that it could not possibly be
made up of stars. The real diameter is about one-third of a
light-year; the central star is particularly hot, with a sur-
face temperature of around 35,000 degrees C. The distance
has been given as 3200 light-years.
Draco is one of the original constellations. In myth-
ology it has been said to honour the dragon which guarded
the golden apples in the Garden of the Hesperides, though
it has also been said to represent the dragon which was
killed by the hero Cadmus before the founding of the city
of Boeotia.
Draco is also one of the largest of the constellations;
it covers 1083 square degrees of the sky, and there are
not very many constellations larger than that. And though
Draco contains no brilliant stars, it is easy enough to iden-
tify. From Britain and similar northern latitudes it is, of
course, circumpolar.STAR MAP 2
NGC 6543 (C6), the
Cat’s Eye Nebula.This is a
complex planetary nebula,
with intricate structures
including concentric gas
shells, jets of high-speed
gas, and unusual shock-
induced knots of gas.
The nebula is about 1000
years old, and represents
a dying star. It could even
be a double-star system.
It lies in Draco, and is
3000 light-years away.BRIGHTEST STARS
No. Star R.A. Dec. Mag. Spectrum Proper name
hm s ° ‘ “
1 · 02 31 50 89 15 51 1.99 K0 Polaris
7 ‚ 14 50 42 74 09 19 2.08 K4 Kocab
13 Á 15 20 44 71 50 02 3.05 A3 Pherkad MajorAlso above mag. 4.3: Â(4.23), 5 (4.25). The other stars of the ‘Little Dipper’ are ̇(Alifa) (4.32), ‰(Yildun) (4.36)
and Ë(Alasco) (4.95).
DOUBLE
Star R.A. Dec. P.A. Sep. Mags
hm °’ ° “
· 02 31.8 89 16 218 18.4 2.0, 9.0BRIGHTEST STARS
No. Star R.A. Dec. Mag. Spectrum Proper name
hm s ° ‘ “
33 Á 17 56 36 51 29 20 2.23 K5 Eltamin
14 Ë 16 23 59 61 30 50 2.74 G8 Aldhibain
23 ‚ 17 30 26 52 18 05 2.79 G2 Alwaid
57 ‰ 19 12 33 67 39 41 3.07 G9 Taïs
22 ̇ 17 08 47 65 42 53 3.17 B6 Aldhibah
12 È 15 24 56 58 57 58 3.29 K2 Edasich
Also above mag. 4.3: ̄(3.57), ·(Thuban) (3.65), Í(Tuza) (3.75), Â(Tyl) (3.83), Ï(Giansar) (3.84), Î(3.87), ı(4.01)
and Ê(4.22)
VARIABLES
Star R.A. Dec. Range Type Period Spectrum
hm °’ (mags) (d)
RY 12 56.4 66 00 5.6–8.0 Semi-reg. 173 N
DOUBLES
Star R.A. Dec. P.A. Sep. Mags
hm °’ ° “
Ë 16 24.0 61 31 142 5.2 2.7, 8.7
Ó 17 32.2 55 11 312 61.9 4.9, 4.9 Binocular pair
„ 17 41.9 72 09 015 30.3 4.9, 6.1
 19 48.2 70 16 016 3.1 3.8, 7.4
CLUSTERS AND NEBULAE
MCNGC R.A. Dec. Mag. Dimensions Type
hm ° ’ “
6 6543 7 58.7 66 38 8.8 18 350 Planetary
nebulaURSA MINORDRACOGa Atl of Univ Phil'03stp 2/4/03 7:36 pm Page 221