Society News. Bristol Astronomical Society Information Leaflet May 2007

Transcription

1 Society News Eclipse Magazine The first issue of the society s other magazine, Eclipse, was published at the end of March and proved a great success. Thanks to all those that contributed to this issue and helped get it out so soon after I took over as editor. I hope to get the next issue out at the end of June but as always this is dependant on getting the material to put into it. I have some material already but I do need more. If you have managed any observing recently please let me have any pictures or reports of what you observed. Bristol Astronomical Society Information Leaflet May 2007 All Times are BST (UT + 1hr) unless otherwise stated Observatory Visits We have recently had a couple of groups visit the observatory, on Monday 26th April, Roger Steer and I took a group from Weston Super Mare Amateur Radio Club along to have a look through the telescope, we stared with Venus and this was not very impressive a boiling blob however once we swung the telescope around to Saturn we had a few more Wows. The same was true for the second group, A Level students from Clevedon School, who were also impressed by Saturn. On that evening, Wednesday 4th April, we also had a look at M42. If you would like to take a group of people, or even family members, along to the observatory and would like some help please contact either Mike Cowles or john Meacham. Observatory We recently had to carry out a small repair to the shutters on the observatory, this was due to wear and tear. Thanks to those involved. Programme of Events for May 2007 All meetings are held at Bristol Grammar School. 4th. May Prof Mark Birkinshaw. ALMA & The SKA. Radio Astronomy after th May Club Evening 18th May Andrew Lound. Mars Odyssey 25th May Club Evening Don t forget to check out the BAS website where you can get all the latest info about the society Globular Cluster M5 in Serpens Caput 1

2 Events this month May 02 Full Moon May 03 Mercury at superior conjunction May 05 Eta Aquarids maximum (visible from April 24 - May 20) May 08 Mercury at perihelion at a distance of A.U. May 10 Last quarter Moon May 13 2nd max. alpha Scorpiid meteors May 13 Moon 3.2 degrees north of Mars May 17 Moon 3.4 degrees north of Mercury May 18 New Moon May 19 Moon 2.5 degrees north of Venus May 22 Occultation of Saturn by the moon May 23 1st quarter Moon May 25 Neptune at it s first stationary point, followed by retrograde motion May 31 4 Vesta at opposition in Ophiuchus Anniversaries this month May 04 40th anniversary of the start of Lunar Orbiter 4 May 13 25th anniversary of the start of mission to the Salyut 7 space station May 14 Anniversary of the birth of Gabriel Fahrenheit ( ) in Danzig, Germany. Best known for his introduction of mercury in thermometers, and the temperature scale named after him. May 15 10th anniversary of the start of STS-84 Atlantis to Mir May 24 45th anniversary of Aurora 7 with Astronaut Scott Carpenter making 3 orbits of the Earth Anniversary of the first official telegraph message "What hath God wrought?" being sent from Washington to Baltimore in 1884 by Samuel Morse. May 26 Anniversary of the birth of Sally Ride (1951) the first American woman to go into space on the shuttle Challenger STS-7 in 1983 Constellation of the Month will reveal approximately 20 to 25 stars. Larger telescopes may reveal some of the nebulosity and the addition of an OIII filter should help. Stars in Serpens Serpens is a long straggling constellation with very few bright stars. The brightest star is alpha (α) Serpentis which has the proper name, Unukalhai which is from the Arabic phrase meaning neck of the snake. Unukalhai is a magnitude +2.65, K-class (K2), orange giant star with a diameter over 15 times that of our sun. The head of the serpent is formed by a triangle of stars, beta (β), gamma (γ) and chi (χ). Beta is a multiple star, the primary component, Beta Ser A, is a white A-class (A3), magnitude dwarf star. It has two companions, a magnitude +9.9 (B), at a distance of 31 arcseconds, and a magnitude (C), at a distance of 201 arcseconds. The star is a member of the Ursa Major Moving Group. Beta is known to the Chinese as Chow, from the Mandarin Zhōu, referring to the Zhou Dynasty. Gamma has the proper name Ainalhai, from the Arabic phrase meaning eye of the serpent. It is a yellow-white F-class (F6) dwarf star of magnitude The star is similar to our sun. Gamma is sometimes shown as having two companions, both 10th magnitude, but these stars are just optical neighbours. Chi is a white A-class (A0) dwarf star that is slightly variable. Its mean apparent magnitude is It varies by 0.03 magnitudes, (much too small a variation to be noticed by the human eye) with a period of days. Chi is classified as an Alpha2 Canum Venaticorum type variable.. R Serpentis is a Mira type variable star which can be found about 1.2 degrees east-southeast of Beta Serpentis. with a period of 356 days. At it s brightest R Ser it is just visible to the naked eye at magnitude +5.7 while at its dimmest it can be as faint as The Sky Catalogue 2000 lists its average maximum magnitude as Like all Mira stars, R Serpentis is a deeply red star. Objects in Serpens Object NGC Type Mag RA Dec M Globular cluster h 19.0m ' M Open Cluster h 18.8m ' R Ser Variable Star h 5.71m ' 2 11

3 Constellation of the Month Serpens Abbreviation Ser Genitive Serpentis The constellation of Serpens is split into two sections Serpens Caput (the serpents head) and Serpens Cauda (the serpents tail). Separating the two sections is the constellation of Ophiuchus (the Serpent Bearer). Serpens Caput lies to the west of Ophiuchus and is the brighter part of the constellation while Serpens Cauda lies to the east. This month we will concentrate on the western section Serpens Caput. Mythology Serpens is a constellation that is connected physically with Ophiuchus, the serpent bearer. Serpens is best known in relation to the healer Aexculapius, represented by Ophiuchus. The power of medicine is represented by the serpents venom which can kill or cure depending on how it is used. Objects on Serpens There are two Messier objects in Serpens, one in each section, M5 is a lovely globular cluster that can be found approximately midway along a line drawn between Arcturus; alpha (α) Boötis and Antares; alpha (α) Scorpii, around 20 arcminutes northwest of the star 5 Serpentis. M5 is easily visible as small hazy patch in binoculars, and as a small round nebula, which is slightly brighter toward the centre through a small telescope. With medium sized instruments, the brighter stars, which form curved patterns extending from the central region start to become be resolved. Larger instruments will reveal a spectacular sight with thousands of stars, extending to over 15 arcminutes in diameter. M5 has a slightly elliptical shape. Due to the number of red giant stars found in M5, it is thought to be one of the oldest globular clusters in our galaxy, around 13 billion years old. Although the second messier is in the tail section of the serpent it is still worth a mention this month. M16 is an open cluster, embedded within an immense nebula known as the Eagle Nebula, the Ghost Nebula or my personal favourite The Star Queen Nebula coined by Robert Burnham Jr. When Messier observed M16 in 1764 he described it as a A cluster of small stars, enmeshed in a faint glow, near the tail of Serpens. M16 lies close to the boarders with Scutum and Sagittarius and is located around 2.5 degrees northwest of gamma (γ) Scuti or just under 3 degrees north of the Swan nebula M17 in Sagittarius. The star cluster is easily visible as a hazy patch in binoculars, large binoculars or a small telescope 10 The Sun Back to Basics Last month we looked at very basic solar observing. This month we ll look at more advanced ways of looking at the Sun using a pair binoculars or telescope to project a much larger image, providing you with much more detail in the image. The principle is much the same as pinhole projection, this time however you will use your telescope or binoculars to produce the image which will be projected on to a sheet of white card positioned a little way behind the eyepiece. (Never look at the Sun through and optical equipment as this will cause permanent damage to your eyes). The picture on the left shows the basic setup, the piece of card over the end of the telescope is there to provide a bit of extra shade giving the image more contrast against the background. This is the basic method used by most solar observers with a few refinements, such as projection boxes on the end to give even more contrast. With this sort of set up even a small telescope will show you a fair amount of detail on the Sun. The image on the right was taken by Roger Steer and shows the sort of image you can get. Have a go at projecting the Sun but take care. 3 Day Sun Rise & Set times for May 2007 Rise 05:42 05:41 05:39 05:37 05:35 05:33 05:32 05:30 05:28 05:27 05:25 05:23 05:22 05:20 05:19 05:17 05:16 05:15 05:13 05:12 05:11 05:09 05:08 05:07 05:06 05:05 04:04 04:03 04:02 05:01 05:00 Set

4 The Moon There has been a lot of correspondence on the Yahoo group recently about observing a feature on the Moon. John Meacham gave a short talk on observing this X shaped object back in March. Eddie Carpenter has found lots of references and pictures in various books on the Moon. The BAA Lunar Section are asking for observations of this phenomenon. The idea is to record the earliest observation of this illuminated X against the dark section of the Moon. This occurs because the X is formed by the high ridges of a number of craters which as they are lower will still be in shadow. While the X can be easily seen against a lit background after first quarter, you must observe at a specific time to catch it against a dark back ground. Your observation must take place when the colongitude of the lunar terminator lies between to 359 degrees. This month on the 24th at 00:00 UT the colongitude will be degrees making the best time to observe between 02:00 and 03:00. During this time the Moon will be between 7.9 and 8.2 days old. 4 Moon Rise & Set times for May Day Rise 20:00 21:13 22:26 23:37 00:40 01:30 02:08 02:35 02:55 03:12 03:26 03:39 03:53 04:09 04:31 05:00 05:43 06:43 07:57 09:18 10:38 11:55 13:08 14:19 15:28 16:37 17:48 19:00 20:14 21:26 Set 04:58 05:12 05:30 05:55 06:29 07:18 08:20 09:35 10:56 12:19 13:43 15:08 16:35 18:05 19:39 21:13 22:42 23:56 00:50 01:26 01:51 02:09 02:22 02:34 02:44 02:54 03:05 03:19 03:35 03:58 The Solar System Below is a table giving timings for some of these events this month. most monthly astronomical magazines give a much fuller list of such events. Date Satellite Type Start End May 05 Io Transit 01:30 02:41 May 22 Europa S/Transit 01:27 03:58 May 26 Ganymede Transit 02:01 04:02 May 29 Io Transit 01:10 03:21 Saturn is currently resident in in the constellation of Leo and is visible high in the southwest in the evening. On a couple of recent group visits to the observatory Saturn has proved to be as popular as ever with our visitors. On the 22nd Saturn is one again occulted by the Moon. On this occasion the whole of the event will be visible form the Bristol area. As the Sun does not set until just after 21:00 the event will begin in daylight so the disappearance may be difficult to observe. Saturn will disappear at the dark limb at approximately 20h 09m at position angle (PA) 144º and reappear at the bright limb at around 21:15 at PA 281º Disappearance of Saturn Uranus may just be visible in the eastern sky just before sunrise at the end of the month Neptune rises about 1 hour before Uranus so should be visible very low in the eastern sky from around the 20th. No detail will be visible with either Uranus or Neptune so it s a case of Yes I ve seen them type of observation. 9 Reappearance of Saturn

5 The Solar System Mercury will be visible in the western sky for most of this month and on into June. This is the most favourable evening apparition of Mercury this year so take this opportunity to catch a glimpse of this elusive little planet. Venus continues to be a brilliant object in the western sky in the early evening. As it starts heading in towards the sun its angular size increases while the phase decreases. At the beginning of the month Venus will have an apparent diameter of 17 arcseconds and be around 68% illuminated, by the end of the month the apparent diameter will have risen to 22 arcseconds while the phase will be around 55% illuminated. The Moon The X can be found almost on the centre line of the Moon in the southern highlands between the craters La Caille, Purbach and Blanchinus. Do try to have a look for this phenomena and let John Meacham have copy of your observations for the BAA survey. Please also lets us have a copy for Eclipse. Mars will be visible low in the eastern sky during the latter part of the month. As the angular diameter of just 5.4 arcseconds no detail will be visible on the disc, however you maybe able to make out the fact that Mars is showing a Gibbous phase with the disc just over 90% illuminated. Blanchinus La Caille Purbach Jupiter rises just as it gets dark at around The giant planet lies in the southern part of Ophiuchus and at magnitude 2.5 is an easy object locate. Jupiter is a fascinating world with so much to see. There is a wealth of detail in the cloud belts and the Great Red Spot (GRS) is always a favourite with observers. Below is a list of approximate times when the GRS crosses the planet s meridian 1st 03:38, 23:29; 3rd 05:16; 4th 01:07; 6th 01:45; 8th 04:23; 9th 00:14; 11th 01:52; 13th 03:30, 23:21; 16th 00:59; 18th 02:37; 20th 04:15; 21st 00:06; 23rd 01:44, 25th 03:22, 23:13; 28th 00:51; 30th 02:29. The four large Galilean moons are also interesting to observe as they move around their parent planet disappearing and reappearing again. There are four types of event that can occur during and orbit; Eclipse; The concealment of one celestial body by another, a phenomenon seen in solar eclipses, lunar eclipses, and eclipsing binary stars and the moons of other planets. Occultation; The blocking of light from one astronomical object, such as a star or asteroid, moon, by another object, such as the Moon, or planet that passes in front of it. Shadow Transit; The passage of the shadow of a moon, cast by the Sun, across the face a planet. Transit; The passage of a smaller astronomical object across the face of a larger one, as in a transit of Venus or Mercury across the Sun, or the transit of a moon across its parent planet. 8 Comment from our director of observations; John Meacham I believe this is a nice exercise for our people to gain more familiarity with the Moon and try to see the X in lunar broad daylight, which is very easy to find. The Hatfield chart 13a, shows the X shape quite clearly, in the gap between La Caille, Purbach & Blanchinus. There is a copy of the Hatfield Photographic Atlas of the Moon in the BAS library. Below are a few of the pictures located by Eddie Carpenter. Pickering "The Moon" 1904 photo 8A taken 1 day after 1st quarter, a few hours too late Goodacre "The Moon" 1931 p.166 refers to landslides best seen at sunset. I have a genuine photo taken one day after 3rd quarter on September 16th 1870 by Rutherford, but again it is a few hours too late Serviss "The Moon" 1908, p.90, plate 7, a photo taken on July 2nd 1903, age of moon 7.24 days, by James Wallace using the 12in refractor. It just shows 90% of the X against a black background. 5

6 The Sky This Month Gemini the last of the bright winter constellations is slowly sinking in west during the evening. Sitting above Gemini you will find Leo with Saturn currently residing within it s boundaries. High overhead you will find Ursa Major and it s well known asterism the Plough, or as it is becoming more often called the Saucepan. This months featured constellation is Serpens which is split into two sections one either side of Ophiuchus. The western part, Serpens Caput can be found in the southeast around midnight. To the south you will find the constellation of Virgo a favourite area of the sky for deep sky observers. Here you will find the Virgo cluster of galaxies the nearest large cluster to the milky way. The cluster contains over 200 members. To the North of Virgo lies the faint constellation of Coma Berenices which also contains a number of galaxies. Coma can be difficult to locate as it does not contain any stars brighter than 5th magnitude. Between Coma and Serpens Caput lies Boötes, a kite shaped constellation with the bright 1st magnitude orange star, Arcturus, α Boötes at its base (see last month s basil for details). Northeast of Boötes lies the familiar shape of Hercules, with the keystone asterim at its centre. The keystone is made up of the stars Epsilon (ε), Zeta (ζ), Eta (η) and Pi (π). Lying about 1/3 of the of the way between Eta (η) and Zeta (ζ) you will find M13, which is without doubt the finest example of a globular cluster that is visible in the northern hemisphere. While in this area don t miss M92 another lovely globular in Hercules. Between Boötes and Hercules lies Corona Borealis. Within this small circlet of stars lies the prototype of the R Coronae Borealis type of variable stars. At irregular periods these stars fade dramatically in the case of R CrB from 6th magnitude down to 14th magnitude. Rising in the east just before midnight are the stars of the Summer Triangle, Vega, Deneb and Altair. 01 May 01:00 16 May 00:00 30 May 23:00 Chart Produced by Chris Peat 6 7

7 Observing chart for R Serpentis Position of Jupiter May 2007

8 Serpens

9 Looking South around midnight mid May 2007 Looking North around midnight mid May 2007

10 Looking West around midnight mid May 2007 Looking East around midnight mid May 2007