M45. The Pleiades. Bristol Astronomical Society Information Leaflet January 2006

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1 Society News Observatory. This year we are hoping to start work on installing the society s 18 inch telescope at the observatory. This will involve a bit of hard labour and we will need some volunteers to help with the heavy work. The plan is to fix the telescope on to a large block of concrete, around this there will be a further concreted area which the housing will sit on. Planing is underway on the design for the telescope housing. We will need assistance when we are digging in the power supply, we also intend to provide a number of external power points for telescope drives and the proliferation of laptops which have become popular at the Saturday observing sessions. We will let you know when we will need your help. Bristol Astronomical Society Information Leaflet January 2006 AGM. The society will be holding our AGM on February 10th. At the AGM all the members of the current committee stand down and every position on the committee is up for re-election. Some of the current members of the committee do not intend to stand this time round so new members will be needed. The only criteria needed to be a committee member is that you are a fully paid up member of the society you are over 18 years old and you want to help the Bristol Astronomical Society move forward. There are also 2 posts open for junior members, who can be involved in all the decisions but are unable to vote at meetings. Please think about standing, nomination forms will be available at all our meetings from Jan 6th. Nominations need to be handed to the Secretary before the start of the AGM. Programme of Events for January 2006 All meetings are held at Bristol Grammar School. 6th. Jan Club Evening 13th Jan Mike Tabb. John Herschel 20th Jan 27th Jan Club Evening Prof. Mark Birkinshaw. Cluster Radio Ghosts Don t forget to check out the BAS website where you can get all the latest info about the society. M45. The Pleiades 12 1

2 The year ahead Observational opportunities. Below are just a few of the major events happening in the sky this year. Unfortunately for us most of these involve a bit of travelling. The undoubted observational highlight of the year will be the total solar eclipse on March 29th. This event is visible from Turkey, the Eastern Mediterranean and Africa. Greatest eclipse occurs in a remote part of Libya close to the border with Chad. The UK will see a partial eclipse with just a small part of the Sun s disc covered by the Moon. Further details will be published in the March issue. On September 22 nd there is an annular eclipse of the sun visible from Guyana and French Guiana. There are 2 lunar eclipses neither of which is total. There is a Penumbral eclipse on 14 th /15 th of March which is visible form the UK. The eclipse begins at 21:22 on the 14 th and ends at 02:14 on the 15 th. A partial lunar eclipse occurs on September 7 th beginning at 18:05 and ending at 19:38. This will not be a spectacular event as the maximum eclipse only 19% of the moon s disc will be covered. In November there will be a transit of Mercury, unfortunately this event will not be visible from the UK. The transit begins at 19:12 on the 8th and ends at 00:10 on the 9th. The best place to observe this event will be Hawaii. February brings the first chance of the year to catch a glimpse of the elusive Mercury in the south-western sky just after sunset. In August there is a good morning apparition of Mercury in the North-eastern sky. The view will be enhanced on this occasion as both Venus and Saturn will be visible in the same area. Constellation of the Month Just as the Pleiades have individual names, so did the Hyades at one time. In fact, these stars were supposed to be the half-sisters of the Pleiades, and Burnham s Celestial Handbook gives their names. Theta 2 is the brightest of the group, and forms a binary with theta 1. Hind's Variable Nebula (NGC 1555) RA 4h 22m Dec +19º 31 This curious object is located 2º west of epsilon (ε) Tauri, and 2º north of delta (δ) Tauri. This is a reflection nebula which varies in brightness due to the variations in T Tauri. This object is quite faint and requires a large telescope to see it. The society s telescope at Failand should be plenty large enough. To find this object you need to first locate the rather dim variable star T Tauri. The nebulous object just to the west, is Hind's Variable Nebula. Meetings As a society we are very catered for when it comes to speakers. Organising 15 visiting speakers is a very difficult job. I carried out this task for a number of years so I speak from experience. This job is currently being carried out by John Meacham and Tricia, who are doing a great job as I m sure everyone would agree. If you know of anyone who you think maybe suitable to give a talk to the society, or if there is anyone you would like to hear speak please let either John or Tricia know. I understand that the programme of speakers for the 2006/2007 session is well under way. Our club nights are also very successful and we would like to continue this success but we need your help with this. If you can give a short talk of demonstration let one of the committee know and we will sort out a date. 2 11

3 Constellation of the Month Epsilon (ε) Tauri Ain Ain is the only star in the Hyades cluster that has been given a proper name. It is a G class yellow/orange star with a surface temperature of 4925 K. RA 04h : Dec : Mag 3.53: Distance 155 LY: Spectral Type G9.5IIICN0.5: Other designations Oculus Boreus; HR 1409; HD Deep Sky Objects in Taurus: Taurus is home to two well known Messier objects: the Crab Nebula (M1) and the Pleiades (M45). There is also another open cluster, The Hyades, and a curious object known as Hind's Variable Nebula". M1. (NGC 1952) Supernova Remnant. RA 05h 34.5m: Dec Just Northwest of zeta (ζ) Tauri is the first of Messier's objects: M1, the Crab Nebula; the remnant of a supernova, recorded in July of 1054 by Chinese and Japanese astronomers. The star must have been a wonderful sight, shining at a magnitude of about -5, it was even bright enough to be seen during the day for nearly a month. The star that exploded, producing the nebula, is now an optical pulsar. Even now, nearly a thousand years later, the nebula is hurtling through space at roughly a thousand kilometres per second. And it continues to grow; the nebula is now over thirteen light years in diameter. M1 is quite a difficult object to locate from light polluted areas. From dark sites the patch of nebulosity shows up quite well and looks vaguely S shaped. M45. The Pleiades RA 03h 47.0m: Dec This open cluster contains as many as 500 stars in an area of space just 13 light years in diameter. It lies at a distance of about 415 lightyears The seven brightest members are collectively known as The Pleiades or Seven Sisters", they are Alcyone, Electra, Maia, Merope, Taygeta, Celaeno, and Asterope. This beautiful cluster is best seen in binoculars or low power rich field telescopes. (see binocular objects page 12 for further details). The Hyades This open cluster of about two hundred stars is only 150 light years away, and considered to be about 600 million years old. It is shaped like a "V", just to the west of Aldebaran. Day Sun Rise & Set for Jan Rise 08:12 08:10 08:10 08:09 08:09 08:08 08:07 08:07 08:06 08:05 08:04 08:04 08:03 08:02 08:01 08:00 07:58 07:57 07:56 07:55 07:54 07:52 07:51 07:50 07:48 07:47 Set 16:12 16:13 16:14 16:15 16:17 16:18 16:19 16:20 16:22 16:23 16:24 16:26 16:27 16:29 16:30 16:32 16:33 16:35 16:37 16:38 16:40 16:42 16:43 16:45 16:47 16:48 16:50 16:52 16:54 16:55 16:57 The Sun & Moon Moon Rise & Set for Jan Day Rise 09:54 10:23 10:43 10:58 11:12 11:24 11:37 11:53 12:12 12:38 13:13 14:01 15:02 16:11 17:25 18:38 19:50 20:59 22:08 23:18 00:30 01:46 03:05 04:28 05:47 06:55 07:46 08:20 08:45 09:02 Set 17:37 19:11 20:42 22:10 23:34 00:56 02:18 03:40 05:00 06:15 07:20 08:10 08:47 09:13 09:33 09:47 09:59 10:09 10:19 10:30 10:41 10:56 11:17 11:46 12:30 13:35 14:59 16:34 18:10 19:43 Phase First Quarter Full Moon Last Quarter New Moon Phases of the Moon Date 6th 14th 22nd 29th Daily phase of the Moon at midnight 10 3

4 The Solar System Mercury is at superior conjunction on the 26 th and is therefore not observable this month. Venus starts the month as an evening object and after passing through inferior conjunction at around midnight of the 13 th, ends the month as a morning object. Inferior conjunction occurs when an object passes between the Earth and the Sun. Of the major planets this can only occur with Mercury and Venus. The last time this happened with Venus we were treated to a very rare transit when the planet crossed the face of the Sun. On this occasion Venus will pass 5.5 to the North of the Sun s disc. On the first of the month Venus will set about 2 hours after the Sun but will rapidly move in towards the Sun making observation more difficult. With a telescope the planet will show a lovely fine crescent shape. Mars is well past its best and is rapidly fading, by the end of the month it will be magnitude The apparent diameter is now just 8 arcseconds. The red planet can be found in the constellation of Aries. Jupiter is a morning object in the constellation of Libra. The giant planet rises about 4 hours before the sun at the beginning of the month increasing to around 5 hours by the end of the month. Jupiter s apparent diameter increases from 33 to 36 arcseconds as the month progresses. Despite Jupiter's low altitude it is still worth a look if you are out observing in the early hours of the morning. Even small telescopes should show the main cloud belts crossing the planets disc and the 4 largest satellites, Io, Europa, Ganymede and Callisto. Saturn reaches opposition on the 27 th it can be found in the constellation of Cancer very close to the open cluster M44 (Praesepe or Beehive cluster). The planet crosses the cluster during the second half of the month. Even small telescopes will show the ring system that Saturn is famous for. Larger instruments will reveal the structure of the ring system showing the Cassini division; the gap between the A and B rings and also the Encke division; a gap within the A ring. Uranus may be glimpsed at the start of the month low in the west after sunset. Neptune is too close to the Sun to be observed this month. Minor Planets. 4 Vesta reaches opposition on the 6th in the constellation of Gemini. Vesta is 4 Constellation of the Month Taurus Abbreviation: Tau: Genitive: Tauri Mythology To the ancient Greeks, the Bull was seen as Zeus in disguise. Zeus fell in love with Europa, the daughter of Agenor, the King of Phoenica. One day while she was playing by the waters edge, she caught sight of a majestic white bull grazing amongst her fathers herd. When she approached the bull, it knelt down and let her get on it's back. Once she was on, it sprang to it's feet and took off to across the sea to Crete where Zeus made her his mistress Stars In Taurus Alpha (α) Tau Aldebaran. Arabic for The Follower (of the Pleiades) Aldebaran is the 13th brightest star in the sky. This K class red giant, has a surface temperature of 3400 K and a diameter of around 40 times greater than that of the sun. Although Aldebaran seem to be part of the Hyades it is in fact a foreground star lying at just under half the distance of the cluster. RA 04h : Dec : Mag 0.85: Distance 68 LY: Spectral Type K5+III: Other designations Cor Tauri; Parilicium; HR 1457; HD Beta (b) Tauri. Elnath. Arabic for the Butting One. Elnath is a hot B class giant star with a surface temperature of 13,600 Kelvin. It is a "mercury-manganese" star, the manganese abundance is about 25 times greater than that of a normal star. the calcium and magnesium abundance reduced and only an eighth solar. RA 05h : Dec : Mag 1.65: Distance 130 LY: Spectral Type BBB: Other designations Alnath; Elnath; HR 1791 HD Gamma (γ) Tauri Hyadum 1 RA 04h : Dec : Mag 3.65: Distance LY: Spectral Type K0-IIIabCN1: Other designations HR 1346; HD Delta (δ)tauri Hyadum 2 Delta is a K class orange giant that is in the Helium burning stage of it life.the star has a precisely measured surface temperature of 4965 K. RA 04h : Dec : Mag 3.76: Distance 153 LY: Spectral Type K0-IIICN0.5: Other designations HR 1373; HD

5 Binocular Objects M45. The Pleiades The Pleiades (M45) is one of the most stunning binocular objects in the night sky. Most people can see six of the stars in this naked eye open cluster, although, as one of its names suggests, seven stars should be visible. The Seven Sisters are (from brightest to dimmest): Alcyone 2.58, Electra 3.72, Maia 3.87, Merope 4.14, Taygeta 4.30, Celaeno 5.54, and Asterope Pleione 5.09, and Atlas 3.63 just east of Alcyone, represent the sister s parents. The cluster is centred on RA 03h 47.0m: Dec and is best seen in binoculars or rich field telescopes. The whole cluster will fit comfortably into the field of a pair of 10 x 50 binoculars. Try making a sketch of the numerous stars that fill the field view. The brightest members are B class young hot blue stars and are still embedded in the clouds of gas and dust from which they were formed. From a dark site, larger telescopes should show some of the nebulosity the cluster is embedded in, particularly around Merope. The cluster contains as many as 500 stars in an area of space just 13 light years in diameter, and lies at a distance of about 415 lightyears. As the Pleiades have been known for thousands of years, it s inclusion in Messier s catalogue of objects that could be mistaken for comets, is rather difficult to understand. the brightest of the minor planets and at opposition is just below naked eye visibility at magnitude +6,2. It should be an easy object in binoculars. Position of Vesta throughout the month 05/01 RA 07h 08.0m Dec /05 RA 06h 56.9m Dec +23º /01 RA 06h 46.8m Dec +24º 10.6 The Solar System Meteors. The Quadrantid meteor shower reaches its maximum on Jan 3 rd at 17:00. The expected rate for the peak is around 80 per hour. The radiant, which lies in the northern part of the constellation of Bootes (RA 15h 28m Dec +50 ), will be sinking towards the north-western horizon during the evening. However as the radiant circumpolar as seen from the UK the altitude starts to increase again after about 21:00 (see table below). The 4 day old waxing crescent Moon should not interfere too much, as it sets around 20:30. The Quadrantids are fairly slow meteors, averaging around 42 km/s. the brighter meteors are sometimes strongly coloured often blue or green 8 Time Altitude Time Altitude 17: : : : : : : : : : : :

6 The Sky This Month On a late January evening the southern sky is dominated by the magnificent constellation of Orion. Orion is one of the most easily recognisable constellations in the sky. It is also very useful as a signpost to other constellations. An imaginary line drawn through the three belt stars, and extended to the Southeast will lead you to the constellation of Canis Major. Alpha (α) Canis Majoris, Sirius; is the brightest star in the night sky. Extending the same line to the Northwest leads you to Taurus (this months, featured constellation see pages 9-11). A line drawn from Rigel through Betelgeuse leads you to Gemini. Just North of Eta (η) Geminii, at the foot of Castor you will find a nice open cluster that easily visible in binoculars. M35 is a cluster of around 150 stars in an area 28 arcminutes across. At magnitude 5.1 it should be visible with the naked eye from a dark location. Below the belt stars lies the showpiece of the winter sky, M42, the Orion Nebula. The Nebula is visible to naked eye as a fuzzy star. Binoculars improve the view a little, but when viewed through a telescope the beauty of this huge cloud of gas and dust is revelled. Very young stars that are forming within the gas cloud illuminate the nebula. Overhead you will find Auriga; home to another three lovely open clusters, M36, M37 and M38; all three are visible in binoculars (see last months issue for further details). Over in the East you will find Leo, an easy constellation to locate as most of the stars that make up the outline of the lion are fairly bright. There are a couple of Messier objects to look at in Leo; M65 and M66 both of these are spiral galaxies. Between the Leo and Gemini lies the constellation of Cancer, which is currently home to Saturn. During the second half of the month, Saturn will pass very close to the open cluster, M44 (Praesepe or Beehive cluster). M44 is an easy naked eye object, however this best viewed with binoculars. 01 Jan 01:00 UT 16 Jan 00:00 UT 30 Jan 23:00 UT Chart Produced by Chris Peat com 6 7

7 Saturn The chart below shows the position of Saturn as it passes in front of M44 4 Vesta The chart below shows the position of Vesta on the 6th. The minor planet will be just below naked eye visiblity at magnitude /01 RA 07h 08.0m Dec /05 RA 06h 56.9m Dec +23º /01 RA 06h 46.8m Dec +24º 10.6

8 Taurus