1300 times as powerful as the Sun. ‚(Alnath) is very
prominent, and has been transferred from Auriga to
Taurus – which seems illogical, as it belongs much more
naturally to the Auriga pattern. It is 130 light-years from
us, and can equal 470 Suns.
Gemini. The Heavenly Twins, Castor and Pollux, make
up a striking pair. Pollux is the brighter; it is 34 light-years
away as against 53 light-years for Castor, and it is an
orange K-type star, outshining the Sun by over 30 times.
Castor is a fine binary with a revolution period of 420
years; though the separation is less than it used to be a
century ago, it is still a suitable target for small telescopes.
Each component is a spectroscopic binary, and there is a
third member of the system, YY Geminorum, which is an
eclipsing binary.
There are two notable variables in Gemini. ̇is a
typical Cepheid, with a period of 10.15 days; this is almost
twice the period of ‰Cephei itself, and ̇Geminorum
is correspondingly the more luminous, since at its peak
it is well over 5000 times as luminous as the Sun. Ë, or
Propus, is a red semi-regular with an extreme range of
magnitude 3.1 to 3.9, and a rough period of around 233
days; a good comparison star is Ì, which is of the same
spectral type (M3) and the same colour. Also in the Twins
is U Geminorum, the prototype dwarf nova. Stars of this
type are known either as U Geminorum stars or as SS
Cygni stars; it is true that U Geminorum is much the
fainter of the two, since its ‘rest’ magnitude is only 14.9
and it never reaches magnitude 8. The average interval
between outbursts is just over 100 days.
M35 is a very conspicuous cluster close to Ëand Ì. It
is 2850 light-years away, and was discovered by de
Chéseaux in 1746; Messier called it ‘a cluster of very
small stars’. It is worth seeking out NGC2392, the Eskimo
Nebula, which is a planetary lying between Îand Ï; the
central star is of the tenth magnitude. The Eskimo is
decidedly elusive, but photographs taken with largerSTAR MAP 17
The Pleiades clusterin
Taurus, photographed by
Bernard Abrams using a
25-cm (10-inch) reflector.
Known since ancient times,
Messier included them as 45.BRIGHTEST STARS
No. Star R.A. Dec. Mag. Spectrum Proper name
hm s ° ‘ “
87 · 04 35 55 16 30 33 0.85 K5 Aldebaran
112 ‚ 05 26 17 28 36 27 1.65 B7 Al Nath
25 Ë 03 47 29 24 06 18 2.87 B7 Alcyone
123 ̇ 05 37 39 21 08 33 3.00 B2 Alheka
35 Ï 04 00 41 12 29 15 3.4 (max) B3
78 ı^2042840 15 52 15 3.42 A7Also above magnitude 4.3: Â(Ain) (3.54), Ô(3.60), 27 (Atlas) (3.63), Á(Hyadum Primus) (3.63),
17 (Electra) (3.70), Í(3.74), ‰(3.76), ı^1 (3.85), 20 (Maia) (3.88), Ó(3.91), 5 (4.11), 23 (Merope)
(4.18), Î(4.22), 88 (4.25), 90 (4.27), 10 (4.28), Ì(4.29), ̆(4.29), 19 (Taygete) (4.30), Ù(4.28),
‰^3 (4.30). ‚(Al Nath) was formerly included in Auriga, as ÁAurigæ.
VARIABLES
Star R.A. Dec. Range Type Period Spectrum
hm °‘(mags) (d)
Ï 04 00.7 12 29 3.3–3.8 Algol 3.95 BA
BU (Pleione) 03 49.2 24 08 4.8–5.5 Irregular – Bp
T0 4 22.0 19 32 8.4–13.5 T Tauri – G–K
SU 05 49.1 19 04 9.0–16.0 R Coronæ – G0p
DOUBLES
Star R.A. Dec. P.A. Sep. Mags
hm ° ‘ ° “
ı 04 28.7 15 32 346 337.4 3.4, 3.8 Naked-eye
Û 04 39.3 15 55 193 431.2 4.7, 5.1 Naked-eye
K 67 04 25.4 22 18 173 339 4.2, 5.3 Naked-eye
CLUSTERS AND NEBULAE
M NGC R.A. Dec. Mag. Dimensions Type
hm °‘ ‘
1 1952 05 34.5 22 01 10 6.4 Supernova
remnant (Crab)
45 1432/5 03 47.0 24 07 3 110 Open cluster
(Pleiades)
04 27 16 00 1 330 Open cluster
(Hyades)TAURUS
BRIGHTEST STARS
No. Star R.A. Dec. Mag. Spectrum Proper name
hm s ° ‘ “
78 ‚ 07 45 19 28 01 34 1.14 K0 Pollux
66 · 07 34 36 31 53 18 1.58 A0 Castor
24 Á 06 37 43 16 23 57 1.93 A0 Alhena
13 Ì 06 22 58 22 30 49 2.88 M3 Tejat
27 Â 06 43 56 25 07 52 2.98 G8 Mebsuta
7 Ë 06 14 53 22 30 24 3.1 (max) M3 Propus
31 Í 06 45 17 12 53 44 3.36 F5 AlzirrAlso above magnitude 4.3: ‰(Wasat) (3.53), Î(3.57), Ï(3.58), ı(3.60), ̇(Mekbuda) (3.7 max),
È(3.79), ̆(4.06), Ó(4.15), 1 (4.16), Ú(4.18), Û(4.28).
VARIABLES
Star R.A. Dec. Range Type Period Spectrum
hm °’(mags) (d)
Ë 06 14.9 22 30 3.1–3.9 Semi-regular 233 M
̇ 07 04.1 20 34 3.7–4.1 Cepheid 10.15 F–G
DOUBLES
Star R.A. Dec. P.A. Sep. Mags
hm ° ’ ° “
Ë 06 14.9 22 30 266 1.4 3v, 8.8 Binary, 470y
· 07 34.6 31 53
AB 088 2.5 1.9, 2.9 Binary 420y
AC 164 72.5 8.8
CLUSTERS AND NEBULAE
M NGC R.A. Dec. Mag. Dimensions Type
hm ° ’ ’
35 2168 06 08.9 24 20 5 28 Open cluster
2392 07 29.2 20 55 10 13” 44” Planetary
nebula
(Eskimo
Nebula)GEMINItelescopes show its curious ‘face’. Like all planetaries it is
expanding, and has now reached a diameter of more than
half a light-year. It was William Herschel who first called
these objects ‘planetary nebulae’, because he thought that
their disks made them look like planets – but the name
could hardly be less appropriate.Gb Atl of Univ Phil'03stp 17/4/03 11:31 am Page 251