Download February - Bristol Astronomical Society

Society News
AGM
As was mentioned in last months issue our AGM takes place on the 10th and a
number of the current members of the committee have stated that they will not be
standing for re-election this year. At the AGM all of the committee stand down
and every position is up for grabs. Any fully paid up member of the society who
is over the age of 18 can stand for election to the committee. There are also 2
posts for junior members who can be involved in every thing the committee does
but they are unable to vote at meetings. Nomination forms will be available at
each meeting, please hand any forms to either Tricia Brown of Mike Cowles.
Both the nominee and the person nominating them need to sign the form.
All nominations need to be handed in before the start of the AGM
Bristol Astronomical Society Information Leaflet
Observatory
During the last few months a working party has spent a lot of time trying to sort
out the drive system on the Cyril Swinden (12”) telescope at Failand. This will
mean that the telescope will track more accurately in the future. This work should
hopefully be completed very soon. Thanks to all those involved.
Open Observing Sessions
The regular observing sessions continue on Saturday evenings, weather
permitting. Check the website or call John Willis 0117 965 7975 or Phil Siviter
on 01454 310 262 before going to the observatory if the weather looks suspect.
Other observing sessions will be held during the year for special events or if there
is any object of interest to observe. Look out for further details
Programme of Events for February 2006
All meetings are held at Bristol Grammar School.
Feb 3rd
Club Evening
Feb 10th
AGM
Feb 17th
Club Evening
Feb 24th
Andrew Lound.
The War of the Worlds
Don’t forget to check out the BAS website where you can get all the latest info
about the society. http://www.bristolastrosoc.org.uk/
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M44. Praesepe or Beehive cluster
1
February 2006
Binocular Objects
Constellation of the Month
M44. Praesepe or Beehive cluster
RA 08h 40.1’ Dec +19º 59’.
This famous cluster has been known since prehistoric times. The ancient Greeks
saw this "nebula" as the manger (Phatne) associated with two asses who eat from
it, Asellus Borealis, the Northern Ass (Gamma Cnc) and Asellus Australis, the
Southern Ass (Delta Cnc). Erathosthenes reported that these were the asses on
which the gods Dionysus and Silenus rode into the battle against the Titans, who
were frightened by the animals' braying so that the gods won. As a reward, the
asses were put in sky together with Phatne. Hipparchus included it in his star
catalogue and called it "Little Cloud".
Galileo was the first person to resolve this "nebulous" object, and reported: "The
nebula called Praesepe, which is not one star only, but a mass of more than 40
small stars.". Charles Messier added it to his catalogue on March 4, 1769.
M44 is easily visible to the naked eye from dark sites with little or no light
pollution. If you know exactly where to look it can even be glimpsed from the
light polluted skies of Bristol. If however you are unable to locate it with the
naked eye, it is easily found 1.5º Northwest of Delta (δ) Cancri.
The cluster covers an area
of around 95 arcminutes
and is best seen in
binoculars, or a rich field
telescope. A pair of 10 x 50
binoculars will reveal
around 40 to 50 stars. The
brighter stars of the group
forms a shape very much
like the constellation
Cepheus.
Astronomers have proved
that at least 200 of the 350
stars in M44 are members
of the cluster, and that they
are very similar in age to
the stars in the Hyades. The
two clusters also have the
same
proper motion
leading to speculation that
they had a common origin.
13,500 K. With a distance of 1760 light years and a total luminosity (including
ultraviolet radiation) of 66,000 times that of the sun it is the most luminous star in
its constellation. Aludra has a strong wind streaming from its surface at 500 km/
second. It is losing mass at a rate of a millionth of a solar mass per year (10
million times the rate of the solar wind), it has already lost about a third the mass
of the whole Sun. Satellites have detected the infrared radiation form the cloud it
has generated around itself.
Aludra has a seventh magnitude companion about two minutes of arc away that is
easily visible in a small telescope. They are however, not linked in any way, it is
just a line of sight pairing. The companion star is an A class white dwarf star,
similar to Sirius. It lies at a distance of only 600 light years, much closer than
Aludra.
RA 07h 24’: Dec -29° 18’: Mag 2.45: Distance 1760 LY: Spectral Type B5Ia:
Other designations HR 2827; HD 58350.
2
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Messier objects in Canis Major
M41 (NGC 2287).
RA 06h 46.0’: Dec -20° 44’
M41 is an open cluster, it can be found about 4° south of Sirius. The cluster
contains about 100 stars, including several red giants. The brightest of these is a
magnitude 6.9, K class star situated near the south-eastern edge of the cluster. The
stars are scattered over an area of 38 arcminutes diameter.
Binoculars will show the cluster as quite a large
faint fuzzy patch. Telescopes should reveal
around 30 stars. The brighter stars are all red
giants and are around magnitude 7 to 8. There
are also a number of magnitude 8 and 9 blue
stars.
Although it was first recorded by Giovanni
Batista Hodierna around 1654, it was probably
quite well known to ancient astronomers.
Charles Messier, was one of many people who
later rediscovered the cluster. He added it to his
famous catalogue on January 16, 1765
Constellation of the Month
The Sun
Mirzam is a very hot, blue; B class giant star with a surface temperature of 22,000
K. Although Mirzam appears relatively dim when compared to Sirius, it is in
reality by far the brighter of the two. Its visual magnitude of +1.98 is the result of
its much greater distance of 500 light-years, 60 times more distant than Sirius. If
Mirzam were at the same distance as Sirius; 8.6 light-years, it would be almost 15
times brighter than Venus at its brightest
RA 06h 22’: Dec -17° 57’: Mag 1.98: distance 500 LY: Spectral Type B1II-III:
Other designations Mirzam; Mirza; HR 2294; HD 44743
Eta (η) CMa Aludra
Aludra is a bright blue-white B class supergiant with a surface temperature of
Sometime during 2006 the Sun is expected to reach Sun Rise & Set times
“solar minimum”, when it is at it’s least active stage of
for
it’s 11 year cycle. At this time very few sunspots are
February 200.
visible. Unlike a lot of astronomical phenomenon there
is no definite date for solar minimum.
Day
Rise
Set
The 11 year sunspot cycle is related to a 22 year cycle
07:45 16:59
for the reversal of the Sun's magnetic field. In 1848 01
02
07:44 17:01
Johann Rudolf Wolf devised a method of counting
03
07:42 17:03
sunspots on the solar disk called the Wolf number.
04
07:41 17:04
Today the Wolf number, taken as the average number
05
07:39 17:06
observed from a number of observing sites, is used to
06
07:37 17:08
keep track of the solar cycle. While the sunspot cycle
07:36 17:10
has been relatively stable this century, there have been 07
07:34 17:11
much greater variations in the past. From 1645 to 1715, 08
09
07:32 17:13
there were very few sunspots on the Sun, this period is
10
07:31 17:15
known as the Maunder minimum.
11
07:29 17:17
12
07:27 17:19
13
07:25 17:20
14
07:23 17:22
15
07:21 17:24
16
07:19 17:26
17
07:18 17:28
18
07:16 17:29
19
07:14 17:31
20
07:12 17:33
21
07:10 17:35
22
07:08 17:37
Average number of sunspots between 1900 and 1990
23
07:06 17:38
24
07:04 17:40
25
07:02 17:42
During the 22 year solar cycle, the migration of
26
07:00 17:44
sunspots in latitude has a ``butterfly pattern.''
27
06:57 17:45
28
06:55 17:47
Next month on the 29th there is a total eclipse of the
Sun. The eclipse will be visible from Turkey, where a
number of the society;s members are going to observe
this wonderful sight. A partial eclipse will be visible
from Bristol. The society has a few solar viewers for
sale at £2 each.
10
3
Gamma (γ) CMa. Muliphen
Muliphein is a B Class blue-white giant, similar in colour to so many other stars
in this region of the sky. With a surface temperature of 13,600 Kelvin, it radiates
685 times more energy than the Sun. The most curious thing about this star, is its
Gamma designation, it is far from being the constellation's third brightest. It
would seem that Bayer probably designated the stars from top to bottom rather
than the normal brightest to dimmest
RA 07h 03’: Dec -15° 38’: Mag 4.12: Distance 400 LY: Spectral Type B8II:
Other designations Isis; Mirza; HR 2657; HD 53244
Delta (δ) CMa. Wezen
Wezen is an F class, yellow supergiant with a temperature of 6200° K, not much
more than our Sun. From its luminosity and temperature, it is estimated that the
star has a radius of 195 times that of the Sun, which makes the star almost as big
as the Earth's orbit. Despite its distance of 1800 light-years, Wezen is so large that
its disk can be measured, which gives a diameter of just over 200 times that of the
Sun.
RA 07h 08’: Dec -26° 23’: Mag 1.84: Distance 1800 LY: Spectral Type F8Ia:
Other designations Alwazn; Wesen; Al Wazor; HR 2693; HD 54605
Epsilon (ε) CMa. Adara
At magnitude 1.5, Adhara is the second brightest star in the constellation. It is
also one of the hottest stars, with a surface temperature of 20,000° K, which gives
it a sparkling bluish colour. From its distance of 425 light years, its luminosity has
been calculated to be 3700 times that of the Sun.
RA 06h 58’: Dec -28° 58’: Mag 1.50: Distance 425 LY: Spectral Type B2II:
Other designations HR 2618; HD 52089
The Moon
Phases of the Moon
Phase
Date
Time
First Quarter
5th
06:29
Full Moon
13th
04:44
Last Quarter
21st
07:17
New Moon
28th
00:31
Moon Rise & Set
times for
February 2006.
1
8
15
22
2
9
16
23
3
10
17
24
4
11
18
25
5
12
19
26
6
13
20
27
7
14
21
28
4
Constellation of the Month
Day
Rise
Set
01
02
03
04
05
06
07
08
09
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
09:17
09:30
09:43
09:58
10:16
10:40
11:12
11:56
12:53
14:00
15:12
16:26
17:38
18:49
19:58
21:07
22:18
23:31
21:12
22:39
00:48
02:07
03:26
04:38
05:35
06:16
06:44
07:05
07:21
00:03
01:27
02:50
04:07
05:15
06:10
06:50
07:18
07:39
07:55
08:07
08:18
08:27
08:37
08:48
09:01
09:19
09:43
10:19
11:12
12:25
13:54
15:29
17:05
18:37
Canis Major
Abbreviation: CMa
Genitive: Canis Majoris
Translation: The Greater Dog
Mythology
There are a number of dog’s that Canis Major is said to represent including
Laelaps, Acteon's hound; the hound of Procris, Diana's nymph; or the one given
by Aurora to Cephalus, so famed for its speed that Zeus elevated it to the sky. It is
however most commonly known as, the largest of Orion's hunting dogs. Canis
Minor represents a second smaller dog.
Alpha (α) CMa Sirius
Sirius; at magnitude -1.47, is the brightest star in the night sky. It is a brilliant
white, A class, hydrogen burning dwarf with a surface temperature of 9880 K.
Sirius is fairly close at just 8.6 light years which is part of the reason it is so
bright. It is also 26 times more luminous than than the Sun. Sirius has a
magnitude 8.44 companion, Sirius B, which is a blue-white dwarf star, which is
about the same size as the Earth. The star is much hotter than Sirius A, with a
surface temperature of 24,800° K.
RA 06h 45’: Dec -16° 42’: Mag -1.46: Distance 8.6 LY: Spectral Type A1Vm:
Other designations Canicula; Dog Star; Aschere; HR 2491; HD 48915.
Beta (β) CMa. Murzim
9
The Solar System
The Moon
Mercury will undergo its best evening apparition of the year. It should be visible
from around the 12th but will be at its best after the 20th. Mercury reaches
greatest eastern elongation on the 24th when it will be 18° from the Sun. it is at its
brightest on the 11th when it will be at magnitude –1.1 and will gradually fade to
+0.5 by the end of the month. Mercury will pass very close to Uranus on 14th.
This months featured object is the crater Agrippa; Longitude: 10.5° East,
Latitude: 4.1° North. The 48 km (28 mile) wide crater has a fairly flat floor with a
large mountain at its centre. There are hills and a lot of debris on the western side
side of the crater. There are also a number of Rilles and craterlets within the
crater.
The walls are terraced, and support Agrippa H on the Northern side and are
damaged on the South-western edge. The steep outer slopes support Agrippa F
and Tempel to the East.
The crater was named by Riccioli to honour the 1st century Greek Astronomer
Agrippa.
To the south of Agrippa; Longitude: 10.2° East, Latitude: 1.8° North, lies Godin;
a 36 km (21 mile) crater. The steep outer slopes support Godin A to the Northwest
Godin B to the South and Godin G to the East. The crater floor is very rugged
with a large central mountain and a number of small hills.
To the West of Agrippa, Longitude: 3.6° East, Latitude: 4.2° North you will find
the 27 km (16 mile) wide crater, Triesnecker. The crater has steep outer slopes
supporting 3 hills to the North and Rimae Triesnecker to the East. The high crater
walls are terraced. The floor is fairly flat with a large central mountain with a
craterlet at the summit.
To the Southeast of Triesnecker; Longitude: 4.9° East, Latitude: 0.0° North lies
the wrecked crater Rhaeticus. The crater has diameter of 51 km (30 miles) with a
pretty flat floor with small central mountain and a few hills and craterlets.
The best time to observe these objects 6 days after New Moon, Feb 4th or 5 days
Venus is a brilliant object in south-eastern predawn sky. Venus is at is brightest
on the 17th when it will reach magnitude –4.6. At this time Venus will show a
thin crescent phase when viewed through a telescope. The phase increases as the
month progresses.
Mars is still visible in the western sky during the evening. During the month the
planet fades by half a magnitude from +0.2 to +0.7 as its distance form the Earth
increases. Mars can be found in the constellation of Aries at the start of the month
moving into Taurus at the end of the first week.
Jupiter is very prominent in the morning sky in the constellation of Libra. Jupiter
is such a dynamic planet there is always a wealth of detail on the planets disk.
Even small telescopes will reveal the main cloud belts running parallel with
Jupiter’s equator. Jupiter's most famous feature is the Great Red Spot (GRS). It
was given its name sometime around 1878 when it was brick red. In recent years
it has generally been much less conspicuous. The Red Spot is a vast, storm,
spinning like a cyclone, but unlike low-pressure cyclones on Earth, the GRS
rotates anticlockwise in Jupiter's southern hemisphere, showing that it is a highpressure system. Below is a list of the times when the GRS crosses the central
meridian of Jupiter.
February 2nd, 2:31, 4th, 4:09, 6th, 5:48, 8th, 7:26, 9th, 3:17, 11th, 4:56, 13th,
6:34, 14th, 02:25, 16th, 04:04, 18th, 05:42, 19, 01:33, 20th, 07:20, 21st, 03:11,
23rd, 04:50, 25th, 06:28, 26th, 02:19, 28th, 03:57,
Triesnecker
Agrippa
Saturn can currently be found in the constellation of Cancer just to the south of
M44 the Beehive cluster.
Uranus is badly placed for observation this month.
Godin
Rhaeticus
Neptune reaches solar conjunction on the 6th and is therefore unobservable this
month.
8
Delambre
5
The Sky This Month
01 Feb 01:00 UT
16 Feb 00:00 UT
During the early evening the southern sky is dominated 28 Feb 23:00 UT
by the bright winter constellations of Orion and Taurus.
M42; The Orion Nebula is one of my favourite objects
in the winter sky. It is easily visible to the naked eye,
below the “belt stars” of Orion. Binoculars will show
quite a lot of detail , but it is with a telescope that the
real beauty of this cloud of dust and gas, which is the
birthplace of stars, is revealed.
By midnight these will well down in the western sky
and the spring constellations of Leo and Cancer will
take centre stage. Cancer is quite a faint constellation,
and can be difficult to locate, however, Saturn is
currently located in Cancer, close to M44, which should
help with identification. M44 is this months featured
binocular object for further details see page 2.
Leo is an easily identifiable constellation and is home to
5 Messier objects, 4 of which, M65, M66, M95 and
M96 are spiral galaxies, the other, M105 is an elliptical
galaxy.
The familiar asterim of the plough, part of Ursa Major is
high in the Northeast around midnight. Mizar; Zeta (ζ)
UMa; the second star from the end of the handle of the
plough has a naked eye companion Alcor; 12
arcminutes to the Northeast. In 1650 Mizar became the
first binary star (two stars orbiting each other) to be
discovered, the two components being separated by 14
arcseconds. Since then it has been discovered that each
of the components is itself a double star. Alcor orbits
this quadruple group of stars once every 750,000 years.
Ursa Major also has a number of messier objects within
its boundaries. M40 which is one of the oddities in
Messier’s list, it is just a double star. M97 the Owl
nebula, is a planetary nebula, the others are all galaxies.
M81 is a very nice spiral galaxy, its close neighbour
M82 is an irregular galaxy, M101, M108 and M109 are
all spirals.
The long straggling constellation of Hydra can be seen Chart Produced by
Chris Peat
rising from the Southeast horizon toward Canis Minor.
http://www.heavens-above.co
om
6
7
Mercury
M44 The Beehive Cluster
Canis Major