Download April - Bristol Astronomical Society

Society News
RA 180 16’ 54”
DEC -18 DEG 29m
Rise, Transit, Set: 0216 (1216), 0750 (1750), 1324 (2324)
Magnitude +4.60
M51 – Whirlpool Galaxy:
RA 130 29’ 54”
DEC +47 DEG 12m
Rise, Transit, Set: 1929 (0529), 0303 (1303), 1038 (2038)
Magnitude: +8.40.
Bristol Astronomical Society Information Leaflet
All times given are BST. UT + 1 hour
Observatory maintenance
Due to the school holidays the first 2 meetings in April will be maintenance
sessions at the observatory. there is always quite a lot of work to do in the spring
as very little in the way of maintenance is carried out over the winter months. One
of the main tasks is to shift all of the dead hedges that were cut down last year and
to clear the area ready for work to begin on the housing for the 18” telescope.
We would also like to get some cupboards built in the existing observatory to
store the eyepieces and to help to protect the star atlases and observing guides that
have been donated to the society. There is also a need to provide storage for all of
the other stuff such as tea making equipment that is currently just sat around in
the observatory. This will make it a lot tidier and a lot safer when there are a lot
of people in the dome observing. There is also so general tiding up and cleaning
to be done. So please come along and do what you can to help.
Programme of Events for April 2006
All meetings are held at Bristol Grammar School.
7th
Observatory Maintenance
14th Observatory Maintenance
21st Dr Rhys Jones
Planetary Nebulae - 1000 New Discoveries
28th. Club Evening
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/
16
M51. The Whirlpool Galaxy
1
April 2006
Binocular Object
Society News
This months binocular object is the globular cluster
M5. This cluster was discovered by Gottfried Kirch
in 1702. Messier later marked it on his chart for
comet of 1753.
This lovely cluster can be found in the constellation
of Serpens Caput; RA 15h 18.5' Dec +02º 04'. Under
excellent observing conditions from a dark site, M5
should be visible with the naked eye, appearing like
an out of focus star. With small binoculars M5 is
visible as a fuzzy patch to the Northwest of the 6th
magnitude star 5 Serpentis. Large binoculars will
show the bright round core of cluster surrounded by a
hazy outer region.
M5 is one of the best globular clusters for small
telescopes in the northern hemisphere. Larger instruments will show a wealth of
detail.
Faulkes Competition
John Willis has organised a competition to come up with an idea on how you
would use 30 minutes of observing time on the Faulkes telescope. The telescope
is a 2 metre telescope situated on Maui, one of the Hawaiian islands.
The winner of the Competition will get the 30 minutes of observing time to carry
out their chosen project.
A number of members are already involved with a project using the telescope so
there will be plenty of help for the lucky winner.
The entries are as follows.
Fiona Lambert
NGC 7783
Hickson Compact Galaxy 98
Image interacting galaxies.
Learn how to do colour photometry and study astronomical observations.
Compare the image with previous published images to identify changes or general
galaxy progression.
Learn about interactions of galaxy clusters.
Simon Smith
Image Pluto, Charon and it's 2 newly discovered Moons.
Using information from time separated exposures to see how they match with the
current values for the new moons.
John Willis
Image a star field
Learn how to do colour photometry and astrometry on the image
Identify the objects against known catalogue objects
Do colour photometry
Work out the positions & check against the catalogue objects.
Scan again for variability.
Phil Siviter
Pluto:
RA 170 45’ 34”
DEC -15 DEG 51 M 19.53S
Rise, transit, set times: (Honolulu time – UT in brackets) 0140 (1140), 0718
(1718), 1256 (2256)
Magnitude +13.94
M24 – Sagittarius star cloud:
2
15
Constellation of the Month
catalogue, “It is double, each has a bright centre, which are separated 4'35". The
two atmospheres touch each other; the one is even fainter than the other.”
This galaxy was the first one where the spiral structure was discovered, in spring
1845 by Lord Rosse, who made a very careful and accurate painting.
This face on spiral is one of the showpiece objects of the spring sky and is an easy
object to locate as it lies just to the Southwest of eta (η) UMa, the end star in the
handle of “the plough”. At magnitude 8.4, it should be visible in a good pair of
binoculars if the sky is dark. Small telescopes will show it as a nebulous patch
with its companion slightly to the north. Larger instruments are needed to observe
the spiral structure of this object.
M63. (NCG 5055) The Sunflower Galaxy. Spiral Galaxy
RA 13h 15.8': Dec +42° 02'
M63 was the first Deep Sky object discovered by Pierre Méchain, who found it
on June 14, 1779. On the same day, Charles Messier included it in his catalogue.
Small telescopes will only show the very bright centre of the galaxy. medium to
large instruments should reveal some of the fainter outer spiral structure.
M94 (NGC 4736) Spiral Galaxy
RA 12h 50.9': Dec +41° 07'
M94 was another of the galaxies discovered by Pierre Méchain. He located this
on on March 22nd 1781. It can be found about 3° Northwest of Alpha (α) CVn. It
is a compact galaxy with a bright centre that shows up well in small telescopes.
larger instruments are required to see the outer regions of this face on spiral.
M106 (NGC 4258) Spiral Galaxy
RA 12h 19.0': Dec +47° 18'
M106 was discovered by Pierre Méchain in 1781 was not included in the original
catalogue produced by Messier. It was officially added to the Messier list in 1947
by Helen Sawyer Hogg along with M105 and M107. The galaxy looks as if it has
undergone massive upheaval leading to rich star forming regions in the spiral
arms which seem to have been stretched along the plane of the galaxy.
With a small telescope the galaxy appears as a bright oval with a short tail. Larger
telescopes will reveal the S shaped spiral arms.
14
The Moon
Moon Rise & Set
times for
April 2006.
Phases of the Moon
Phase
Date
Time
First Quarter
5th
13:01
Full Moon
13th
17:40
Last Quarter
21st
04:28
New Moon
27th
20:44
01
08
02
09
03
10
15
17
22
29
23
30
24
04
11
18
25
05
12
19
26
06
13
20
27
07
14
21
28
3
Day Rise
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
29
30
07:42
08:08
08:45
09:34
10:37
11:47
13:01
14:14
15:26
16:36
17:46
18:56
20:08
21:24
22:42
00:02
01:17
02:22
03:11
03:47
04:11
04:30
04:45
04:58
05:11
05:25
05:43
06:06
06:38
Set
00:29
01:50
02:58
03:49
04:26
04:52
05:10
05:24
05:36
05:46
05:55
06:06
06:17
06:32
06:51
07:19
07:59
08:56
10:10
11:35
13:04
14:33
16:01
17:29
18:57
20:27
22:57
23:23
The Moon
This month we look at a large section of the Moon centred around the Mare
Serenitatis (Sea of Serenity). The area is just to the Northeast of the moon’s
centre and is best seen a few days before first or last quarter. There is a vast
amount to see in the area whatever type of instrument you use.
The area is dominated by the almost circular Mare which covers an area of around
300,000 square kilometres. The Western side of the Mare is dominated by the
large mountain ranges of the Montes Apenninus and Montes Caucasus.
Also on the western side of the Mare you will find the infamous crater Linné;
Latitude 27.7° North Longitude 11.8° East. The crater was discovered by Riccioli
during the seventeenth century. During the nineteenth century Lohrman, Madler,
and Schmidt all observed it as a crater. Schmidt drew it as a crater in eight of
eleven drawings he made between 1840 and 1843. In 1866, however, he made the
spectacular announcement that the crater no longer remained and that only the
bright mound was observable, this was also confirmed by numerous other
observers during 1867.
In the eastern half of the Mare, running North to South is the 134 km (79 mile)
long wrinkle ridge known as the Dorsa Smirnov. This is a very prominent feature
and can be seen with large binoculars or a small telescope. Midway along the
ridge is the small crater Very; a bowl shaped crater with high walls and a rounded
floor. At just 5 km (3 miles) wide, a telescope of at least 4 inch diameter is
required to see this object.
Aristoteles; Latitude 50.2° North, Longitude 17.4° East, is a large, 90 km (53
mile) wide, crater, with very high terraced walls. The extensive floor is flat with
a few hills, rilles and small craterlets. There are also 2 small mountains that are
situated just off-centre of the crater. The outer slopes are steep and tormented
supporting Mitchell to the East.
Eudoxus; Latitude 44.3° North Longitude 16.3° East, is a 70 km (41 mile) wide
crater with very high walls with terraces. The very steep and tormented outer
slopes support Eudoxus B to the North and Eudoxus A and G to the North-East.
The floor of the crater is very uneven with hills and central mountains.
Hercules; Latitude 46.7° North, Longitude 39.1° East, is a 71 km (42 mile) wide
crater with high terraced walls supporting Hercules E to the Southwest of the
crater. The steep slopes support Hercules D to the South-East. The floor is fairly
flat floor with the 13 km (8 mile) bowl shaped crater; Hercules G; lying in the
Southeast of the crater. There are also a number of small hills and some dark
areas within the crater.
Posidonius; Latitude 31.8° North, Longitude 29.9° East is a 99 km (58 mile) wide
crater with fairly high walls. The steep outer slopes support the trio of small
craters Posidonius O, I and B on the northern slopes. The floor of the crater is
4
Constellation of the Month
M3 (NGC 5272) Globular cluster
RA 13h 42.2': Dec +28° 23'
M3 is one of the most outstanding globular clusters, containing an estimated half
million stars. It was discovered by Charles Messier on May 3rd, 1764, and first
resolved into stars and recognised as cluster by William Herschel around 1784.
With a visual magnitude of around 6.2, M3 is just below the limit of naked eye
visibility, however it easily seen with binoculars. In a pair of 10 x 50’s it appears
as a hazy patch. A small telescope will reveal its bright compact core within a
hazy glow, which fades towards the outer edges. Medium sized instruments will
resolve outer two thirds, with a background glow formed by the unresolved stars.
Large telescopes will resolve all but the very centre of the cluster.
M51. (NGC 5194) The Whirlpool Galaxy. Spiral Galaxy
RA 13h 29.9': Dec +47° 12'
The famous Whirlpool galaxy M51 was discovered by Charles Messier on
October 13, 1773, while he was observing a comet. He described it as a "very
faint nebula, without stars" which is difficult to see. Its companion, NGC 5195,
was discovered in 1781 by Pierre Méchain, and is mentioned in Messier's 1784
13
Constellation of the Month
Type A0pSiEuHg: Other Designations HR 4915, HD 112413.
Beta (β) CVn Chara
Chara and Cor Caroli represent the "southern dog," the "northern dog" is
represented by a small group of stars to the Northeast of Cor Caroli. Chara was
originally the name for the southern dog itself, with the northern called
"Asterion". But with the brighter of the stars that make the southern dog called
"Cor Caroli,” Beta CVn got the name to itself.
Chara is very similar to the Sun, at a distance of 27 light years it gives us a good
indication of what the Sun would look like from a planet orbiting one of our near
neighbours. It is a G class star with a temperature of 5860 K, with a mass and
radius almost identical to our sun, however it is 25 percent more luminous. Since
main sequence stars brighten as they age, it is thought that Chara may be one or
two billion years older than the Sun.
The Moon
fairly flat with numerous craterlets including Posidonius A and C. There is also a
a ridge running down the eastern side of the crater known as Rimae Posidonius.
Aristllius; Latitude: 33.9° North, Longitude 1.2° East is a 56 km (33 mile) which
is the centre of a small ray system. The crater walls are fairly high with a number
of terraces. The outer slopes are very steep and rugged. The floor is flat with 3
central mountains 900 m high.
The Montes Caucasus run along the North-western edge of the Mare Serenitatis
for 536 Km (315 miles) to Eudoxus. These mountainous peaks rise to over
3650m (11100 ft) above the floor of the Mare.
Aristoteles
Hercules
Star Data: RA 12h 33': Dec +41° 21': Magnitude 4.26: Distance 27 LY: Spectral
Type G0V: Other Designations HR 4785, HD 109358.
Y CVn La Superba
This star is a semi-regular variable red supergiant which varies between 5.2 to 6.6
in 157 days. It is among the brightest of the "carbon stars," classified as a C7
supergiant; it is also one of the reddest stars in the sky and one of the coolest of
naked eye stars, with a surface temperature of just 2200 K. Carbon stars were
originally classed as warmer "R" and cooler "N," and are now combined into
class "C." Most red giants are richer in oxygen than carbon: carbon stars however
have these ratios reversed.
The star is coming to the end of its life, the by-products of nuclear fusion, in this
case, carbon, from the nuclear "burning" of helium, rise to the surface before
escaping into space. Absorption by these carbon molecules give the star a
remarkable spectrum, a combination of them cutting out blue and violet light and
making the star quite red. It was the beauty of the stars spectrum that caused
Father Angelo Secchi, to give the star its name "La Superba".
See chart on page 11.
Eudoxus
Montes Caucasus
Posidonius
Mare Serenitatis
Linné
Very
Montes Apenninus
Dorsa Smirnov
Star Data: 12h 45': Dec +45° 26': Magnitude 4.70 to 8.00: Distance 710 LY:
Spectral Type C7: Other Designations
Messier Objects in Canes Venatici
12
5
The Solar System
Constellation of the Month
Mercury is too far south for observation this month for observers in the UK.
However if you are heading south, this is the best morning apparition this year for
southern observers.
Canes Venatici
Venus at magnitude -4.2 is unmistakable low in the eastern sky just before
sunrise. On the morning of the 24th the waning crescent Moon will be close to
Venus providing an excellent opportunity some astrophotography.
Mythology
Canes Venatici represents
Chara and Asterion the hunting
dogs of Bootës, the herdsman.
Bootës is also known as the
Bear keeper, it is in this role
that the dogs are employed to
assist him to keep a watch on
the neighbouring bears, Ursa
Major and Ursa Minor.
Canes Venatici first appeared
Firmamentum Sobiescianum
sive Uranographia published
in 1790. This great star atlas by
Johannes Hevelius contained
very accurate positions for
1564 stars. It also included 7
entirely new constellations,
Canes Venatici, Lacerta, Leo
Minor, Lynx Scutum, Sextans
and Vulpecula.
Mars is still visible in the western sky throughout the month.at the beginning of
the month the red planet will set at around 02:20 and by the end at around 01:30.
During the month the apparent magnitude will fade from +1.2 to +1.5 as the
planet moves further away from us. The apparent diameter is just 5 arcseconds,
making it difficult to see any detail. Mars moves from Taurus into Gemini on the
14th. On the 17th and 18th Mars will be less than 1° north of the open cluster,
M35.
Jupiter is now visible for most of the night it rises at around 22:30 at the start of
the month and by 20;30 at the end. It is currently moving in a retrograde motion
through the constellation of Libra, passing close to Alpha (α) Librae at the end of
the month. Jupiter is probably the most rewarding planet for observers as it
provides an ever-changing wealth of detail on it’s disc.
Below is a list of visible transits of Jupiter’s Great Red Spot (GRS) during April:
3rd 02:57, 22:48; 5th 04:35; 6th 00:26; 7th 06:13; 8th 02:04; 10th 03:42, 23:33;
12th 05:20; 13th 01:11; 15th 02:49, 22:40; 17th 04:27; 18th 00:18; 20th 01:56,
21:47; 22nd 03:34, 23:25; 24th 05:12; 25th 01:03; 27th 02:41, 22:32; 29th
04:19; 30th 00:10.
The 4 largest of Jupiter's moons are involved in in various events as they orbit the
giant plant, such a eclipses, occultation's, transits and shadow transits. The table
below lists some of these events. More comprehensive lists of events can be
found in monthly magazines and the BAA handbook.
Date
Satellite
Event
Start
End
3rd
Europa
Eclipse
00:27
04:22
9th
Ganymede
Eclipse
00:34
02:29
15th/16th
Io
Shadow Transit
23:37
01:47
16th
Io
Transit
00:04
02:12
26th
Europa
Shadow Transit
02:20
04:53
26th
Europa
Transit
02:47
05:15
6
Abbreviation: CVn Genitive: Canum Venaticorum
Names Stars in Canes Venatici
Alpha (α) CVn Cor Caroli
Cor Caroli, which means "Charles' Heart" in honour of England's King Charles II,
is the brightest star of the modern constellation Canes Venatici, the Hunting
Dogs. Alpha CVn is a double star with components of 3rd (alpha 2) and 5th (Alpha
1) magnitude. The brighter star is a white, A class, star with a surface temperature
of 9500 K, it also possesses one of the strongest known magnetic fields among
the "main sequence" stars, over 1500 times stronger than ours Sun’s own
magnetic field. The star also has a weird chemical composition in which elements
such as silicon, mercury, and rarer elements such as europium are locally
enormously enhanced.
Star data: RA 12h 56': Dec +38° 19': Magnitude 2.90: Distance 97 LY: Spectral
11
Path of Comet 73P/Schwassmann-Wachmann
The Solar System
Saturn is can be found in the constellation of Cancer not far from M44 and is
visible for most of the night. The ringed planed reaches its second stationary point
on the 5th from then on it resumes its normal direct motion with respect to the
background stars. Saturn is without doubt my favourite astronomical object, it is a
beautiful sight even through a small telescope and always gets a “wow” when
someone sees it for the first time. If you have never seen Saturn through a
telescope go along to one of the open observing sessions held every clear
Saturday at the society’s observatory and have a look , you will not be
disappointed.
Uranus lies in the constellation of Aquarius but is too close to the Sun for
observation this month.
Neptune is currently in the constellation of Capricornus an may be glimpsed at
the end of the month very low in the eastern sky just before dawn.
Pluto can be found in the constellation of Serpens Cauda. It rises in the early
hours but will require a large telescope, a good southeastern horizon and a very
good star chart to pick out this 14th magnitude member of our planetary family
Meteors
The Lyrids
The Lyrid meteor shower is active from April 16th to 25th with the maximum
occurring on the evening of April 22nd. The radiant of the shower at the time of
the peak will be RA 18h 04m, Dec +34°, which is in Hercules just over the LyraHercules boarder.
The source of the Lyrid meteor shower is Comet Thatcher (C/1861 G1). Every
year during April the Earth passes through the dust and debris left behind by
comet Thatcher. Lyrid’s are medium to fast meteors with the particles hitting the
atmosphere with a relative velocity of 49 km/s (110,000 mph) and can sometimes
be very bright
Comets
Comet 73P Schwassmann-Wachmann is an interesting object as it is a comet that
has broken into a number of pieces. The comet is predicted to brighten as the
month progresses. It will start the month at 11.8 in the constellation of Boötes
close to Arcturus. It rapidly moves through Corona Borealis passing very close to
Alpha ()α CrB on the 21st. It will end the month in the constellation of Hercules
close to Zeta (ζ) Her; when it is predicted to be around magnitude 8.
10
7
The Sky This Month
As the nights rapidly get shorter and the switching to
British Summer Time at the end of last month, you will
have to wait much longer for the sky to get dark. The
bright constellations of winter have now set in the west
and the southern sky is dominated by the constellation
of Leo. There are a couple of nice galaxies M65 and
M66 just to the south of Theta (θ) Leonis, that should be
visible in binoculars on very good nights from a dark
site.
To the east of Leo you will find the faint constellation
of Coma Berenices. To the south of Coma lies Virgo,
this area of the sky is home to a large cluster of galaxies
known as the Coma/Virgo cluster and is a very popular
area for deep sky observers. (see March issue for further
details).
High overhead is Ursa Major with the familiar shape of
the “plough” standing out among the fainter stars of the
Great Bear. This area is also rich in deep sky objects
including a number from the Messier catalogue. The
best known are M81 and M82 a nice pair of galaxies
that are visible in binoculars. M97; the Owl Nebula cab
be found about 2.5° Southeast of beta (β) UMa. This is
a large cloud of glowing gas that emits its light strongly
in the green of double ionised oxygen and the use of an
OIII filter will enhance views of this and many other
planetary nebulae.
To the East you will find Bootés and the lovely circlet
of stars that make up the tiny constellation of Corona
Borealis.
Lower down in the East is Hercules which is home to
the northern hemisphere’s best globular cluster M13
which lies on the western side of the Keystone asterism
between eta (η) and zeta (ζ) Her. There is another
globular cluster in Hercules that is often over looked,
M92 lies approximately midway between eta (η) and
iota (ι) Her in the northern part of the constellation. at
magnitude +6.5 it is quite easy with binoculars in a dark
sky.
8
01 Apr 01:00 UT
16 Apr 00:00 UT
30 Apr 23:00 UT
Chart Produced by
Chris Peat
http://www.heavens-above.co
om
9
Path of fragments B & C of Comet 73P/Schwassmann-Wachmann
Canes Venatici