BRIGHTEST STARS
No. Star R.A. Dec. Mag. Spectrum Proper name
hm s ° ‘ “
16 · 14 15 40 19 10 57 0.04 K2 Arcturus
36 Â 14 44 59 27 04 27 2.37 K0 Izar
8 Ë 13 54 41 18 23 51 2.68 G0
27 Á 14 32 05 38 13 30 3.03 A7 Seginus
49 ‰ 15 15 30 33 18 53 3.47 G8 Alkalurops
42 ‚ 15 01 57 40 23 26 3.50 G8 Nekkar
Also above magnitude 4.3; Ú(3.58), ̇(3.78), ı(4.05), ̆(4.06), Ï(4.18).
VARIABLES
Star R.A. Dec. Range Type Period Spectrum
hm °’ (mags) (d)
R1 4 37.2 26 44 6.2–13.1 Mira 223 M
W1 4 43.4 26 32 4.7–5.4 Semi-regular 450 M
DOUBLES
Star R.A. Dec. P.A. Sep. Mags
hm °’ ° “
K1 4 13.5 51 47 236 13.4 4.6, 6.6
È 14 16.2 51 22 033 38.5 4.9, 7.5
14 40.7 16 25 108 5.6 4.9, 5.8
Ì 15 24.5 37 23 171 108.3 4.3, 7.0
 14 45.0 27 04 339 2.8 2.5, 4.9BRIGHTEST STARS
No. Star R.A. Dec. Mag. Spectrum Proper name
hm s ° ‘ “
5 · 15 34 41 26 42 53 2.23 A0 Alphekka
The ‘crown’ is made up of ·together with Â(4.15), ‰(4.63), Á(3.84), ‚(3.68) and ı(4.14).
VARIABLES
Star R.A. Dec. Range Type Period Spectrum
hm °’ (mags) (d)
R1 5 48.6 28 09 5.7–15 R Coronae – F8p
S1 5 21.4 31 22 5.8–14.1 Mira 360 M
T1 5 59.5 25 55 2.0–10.8 Recurrent – MQ
nova
DOUBLE
Star R.A. Dec. P.A. Sep. Mags
hm °’ ° “
Ë 15 23.2 30 17 030 1.0 5.8, 5.9
̇ 15 39.4 36 38 305 6.3 5.1, 6.0
Û 16 14.7 33 52 234 7.0 5.6, 6.6 Binary, 1000y.The brightest star in this vast, dim cluster is ‚; R.A. 13h 11m 52s, dec. 27° 52’ 41”, mag. 4.26.
Then come ·(Diadem) (4.32) and Á(4.35).
CLUSTERS AND NEBULAE
M NGC R.A. Dec. Mag. Dimensions Type
hm °’ ’
53 5024 13 12.9 18 10 7.7 12.6 Globular cluster
64 4826 12 56.7 21 41 8.5 9.3 5.4 Sb (Black-Eye)
galaxy
88 4501 12 32.0 14 25 9.5 6.9 3.9 SBb galaxy
98 4192 12 13.8 14 54 10.1 9.5 3.2 Sb galaxy
99 4254 12 18.8 14 25 9.8 5.4 4.8 Sc galaxy
100 4321 12 22.9 15 49 9.4 6.9 6.2 Sc galaxyBOÖTESCORONA BOREALISCOMA BERENICESËCoronae is a close binary, with an average separation
of 1 second of arc and components of magnitudes 5.6 and
5.9; it is a binary with a period of 41.6 years, and is a
useful test object for telescopes of around 13-centimetre
(5-inch) aperture. There are optical companions at 58
seconds of arc (magnitude 12.5) and 215 seconds of arc
(magnitude 10.0). ̇and Ûare both easy doubles, while
‚is a spectroscopic binary, and is also a magnetic variable
of the same type as Cor Caroli.
Inside the bowl of the Crown lies the celebrated
variable R Coronae, which periodically veils itself behind
clouds of soot in its atmosphere. Usually it is on the brink
of naked-eye visibility, but it shows sudden, unpredictable
drops to minimum. At its faintest it fades below magnitude
15, so that it passes well out of the range of small tele-
scopes; on the other hand there may be long periods when
the light remains almost steady, as happened between
1924 and 1934. It is much the brightest member of its
class, and of the rest only RY Sagittarii approaches naked-
eye visibility.
R Coronae is a splendid target for binocular observers.
Generally, binoculars will show two stars in the bowl,
Rand a star (M) of magnitude 6.6. If you examine the area
with a low power and see only one star instead of two,
you may be sure that R Coronae has ‘taken a dive’.
Outside the bowl, near Â, is the Blaze Star, T Coronae,
which is normally of around the tenth magnitude, but
has shown two outbursts during the past century and a
half; in 1866, when it reached magnitude 2.2 (equal to
Alphekka), and again in 1946, when the maximum mag-
nitude was about 3. On neither occasion did it remain a
naked-eye object for more than a week. But it is worth
keeping a watch on it, though if these sudden outbursts
have any periodicity there is not likely to be another until
around 2026.
Spectroscopic examination has shown that T Coronae
is in fact, a binary, made up of a hot B-type star together
with a cool red giant. It is the B-star which is the site of
the outbursts, while the red giant seems to be irregularly
variable over a range of about a magnitude, causing the
much smaller fluctuations observed when the star is at
minimum. Other recurrent novae are known, but only the
Blaze Star seems to be capable of becoming really promi-
nent. Also in the constellation is S Coronae, a normal Mira
variable which rises to the verge of naked-eye visibility
when it is at its maximum.
Mythologically, Corona is said to represent a crown
given by the wine-god Bacchus to Ariadne, daughter of
King Minos of Crete.
Coma Berenicesis not an original constellation – it was
added to the sky by Tycho Brahe in 1690 – but there is a
legend attached to it. When the King of Egypt set out upon
a dangerous military expedition, his wife Berenice vowed
that if he returned safely she would cut off her lovely hair
and place it in the Temple of Venus. The king returned;
Berenice kept her promise, and Jupiter placed the shining
tresses in the sky.
Coma gives the impression of a vast, dim cluster. It
abounds in galaxies, of which five are in Messier’s list. Of
these, the most notable is M64, which is known as the
Black-Eye Galaxy because of a dark region in it north of
the centre – though this feature cannot be seen with any
telescope below around 25-centimetre (10-inch) aperture.
There is also a globular cluster, M53, close to ·Comae
which is an easy telescopic object. ‚Comae and its neigh-
bour 41 act as good guides to the globular cluster M3,
which lies just across the border of Canes Venatici and is
described with Star Map 1.STAR MAP 4
R Coronaeis a splendid
target for binocular observers.
It is found within the bowl of
Corona Borealis. If only one
star is visible there, it is M
with a magnitude of 6.6, and
R Coronae has taken one of
its periodic ‘dives’.RAlphekkaȉ
Á
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