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Society News On the evening of the 19th of August we held our second annual summer picnic at the national Trust’s Tyntesfield Estate. The evening started with a quiz, those attending split in to groups of four to six people to answer a series of astronomy related questions set by Tricia. Drinks were served while we were answering the questions, some of which were quite tricky. The winning team will be announced as soon as Tricia has had time to go through the answer sheets. After the question papers were collected it was time for the food, which as always was excellent with plenty of choice. The puddings were especially good After everyone had had enough to eat the plan had been that we would do some observing, however the weather had other plans. Other than small, short breaks in the clouds, the sky was completely obscured. People started to pack up and leave at around 11pm, all in all despite the poor weather the evening was a great success. BristolAstronomicalSocietyInformationLea let All times are BST (UT +1hr) unless stated otherwise Astronomy Course Rodney Hillier’s long running astronomy course begins again on October 17th, it will be held in Room J16 above the 6th form common room. Further details will be published in next months’ issue. Observatory We have now been given the go ahead to install the 18” telescope at Failand, we now need people to help carry out the work needed. If you are willing to help please contact John Willis. Programme of Events for September 2011 All meetings are held at Bristol Grammar School, University Road BS8 1SR 2nd Sep Club Night - Eddie Carpenter 9th Sep Observatory Maintenance & Observing (if clear) 16th Sep Club Night - John Willis 23rd Sep Observatory Maintenance & Observing (if clear) 30th Sep Club Night - Roger Steer 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/ Sunspots 16/08/11 - Image from SOHO Bristol Astronomical Society are a Registered Charity, No. 299649 24 September2011 1 The The Sun & Moon Sun Sun and Moon Rise and Set times for September 2011 Sun Moon Date Rise Set Rise 01 06:22 19:57 11:05 02 06:24 19:55 12:29 03 06:25 19:53 13:47 04 06:27 19:51 14:57 05 06:29 19:49 15:55 06 06:30 19:46 16:42 07 06:32 19:44 17:18 08 06:33 19:42 17:46 09 06:35 19:39 18:09 10 06:37 19:37 18:29 11 06:38 19:35 18:47 12 06:40 19:33 19:04 13 06:41 19:30 19:21 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 06:43 06:45 06:46 06:48 06:49 06:51 06:53 06:54 06:56 06:57 06:59 07:01 07:02 07:04 07:05 07:07 07:09 19:28 19:26 19:23 19:21 19:19 19:16 19:14 19:12 19:10 19:07 19:05 19:03 19:00 18:58 18:56 18:54 18:51 2 19:40 20:01 20:26 20:56 21:34 22:21 23:18 00:24 01:38 02:56 04:18 05:42 07:08 08:35 10:02 11:26 Failand Open Observing Rota September 2011 Month Day Set 20:55 21:28 22:08 22:57 23:57 Opener Email Assistant Terry Blake [email protected] Roger Sykes Sep 3rd Sep 10th Terry Flower [email protected] James Nelis Sep 17th Terry Blake [email protected] Dave Smales Sep 24th Roger Sykes [email protected] Alison Camacho All welcome 01:03 02:13 03:24 04:34 05:43 06:51 07:57 09:04 10:10 11:16 12:20 13:22 14:18 15:08 15:50 16:25 16:54 17:19 17:43 18:05 18:29 18:55 19:26 20:04 Including Family, Friends, Neighbours, with or without telescopes binoculars etc. No Astronomical knowledge or skill required. Please: Contact the opener by email if you want to bring more than 4 visitors or to ask if it appropriate to run an activity on the night. Use the status message on www.bristolastrosoc.org.uk to check if the session is running. Email [email protected] if you want to join the rota. See the charts on open observing page on the website to see what objects are visible that weekend. 23 The Sun & Moon The Autumn Equinox occurs on the 23rd of this month. At 10.05 the Sun will cross the celestial equator heading south. This marks the end of the northern hemisphere summer and the start of autumn. Equinox mean equal night and at this time of the year the length of day and night are approximately the same length. The Sun Observers of the Sun have had plenty to look at over the past few months with lots of active regions visible. The image on the right was taken by the SOHO satellite on the 16th August and shows the large sunspot group 1271 just appearing round the eastern limb. To get the latest news and images of our nearest star check out the SOHO website at:- http://sohowww.nascom.nasa.gov Pegasus The Moon 27th 12:09 4th 18:39 12th 07:04 The Seven Day Old (First Quarter) Moon The First Quarter Moon is one of the most spectacular lunar phases, in the northern half of the moon the following interesting features are visible on or near the terminator, the Alpine Valley, the Lunar Alps, Aristillus, Archimedes and the Apennine Mountains. The Alpine Valley (Vallis Alpes) is one of the most popular features on the moon, this 166km long scar runs in an east-northeast direction from the edge of the Mare Imbrium and slices through the Lunar Alps. The Lunar Alps (Montes Alpes) form part of the north-western rim of the Mare Imbrium, the range is around 260 km in length and contains some stunning peaks. Two of the most notable peaks are Mons Blanc which rises to 3.6km in height and Mons Piton which reaches 2.3km in height. 22 3 20th 14:39 The Sun & Moon Aristillus is a 50km wide crater with a central peak which is over 900m high. Archimedes is 85km in diameter, its inner walls are terraced and the floor is flat with no central peak. The Apennine Mountains (Montes Apenninus) run for almost 1000km around the south-western rim of the Mare Imbrium. Like the Lunar alps it has some notable peaks including Mons Huygens which at 5.4km in height is listed as the highest mountain on the Moon. Mons Bradley 4.2km and Mons Hadley 3.5km. In the southern half of the Moon you will find Ptolemaeus, Alphonsus, Arzachel, in a line running from north to south. Ptolemaeus is the largest with a diameter of 158km, it has high walls and a flat floor riddles with craterlets. Alphonsus is the next in size with a diameter of 121km. Its high walls are terraced and the crater floor is fairly flat with a central peak. The last of the trio is Arzachel, which with a diameter of 100km is the smallest. Arzachel has high terraced internal walls and a central peak which rises to over 1.5km. Constellation of the Month AG Pegasi is a Z Andromedae type variable, a group of symbiotic stars which exchange of mass between the two components which causes the variations in brightness. The star brightened by about 3 magnitudes from 9th to 6th magnitude over a 20 year period (1850 –1870) then very slowly faded back to 9th magnitude by 1960. AG Peg can be found around 3 degrees north-northwest of epsilon Pegasi. The chart on the right is produced by the AAVSO . As the Sun rises the high points of mountains and crater walls are illuminated while the surrounding area is still in shadow providing you with some spectacular sights. First Quarter occurs on the 4th of the month at around 18:30 so get out that evening and have a look at our nearest neighbour during this lovely phase. Objects in Pegasus Object M15 Stephan’s Quintet AG Pegasi R Pegasi 4 NGC Type Mag 7078 Globular Cluster +6.0 7331 Spiral Galaxy +9.5 7317 7320 Galaxy Group RA Dec 21h 30.0m +12° 10' 22h 37m +34° 25' +12.6 to +13.6 22h 35.9m +33° 57' Variable Star +6.0 to +9.4 21h 51.0m +12° 38' Variable Star +6.9 to +13.8 22h 06.6m +10° 33' 21 The Planets Constellation of the Month in the constellation of Pegasus. This small group of five galaxies lies just to the south on NGC 7331. The group is very popular with imagers but can be difficult to spot visually. Stars in Pegasus Alpha (α) Pegasi has the proper name Markab which comes from an Arabic phrase meaning "the horse's shoulder". Markab lies at the south-western corner of the square of Pegasus. The star is a hot B-class (B9) dwarf which, at magnitude +2.49 ranks as the third brightest star in the constellation. Beta (β) Pegasi has the proper name Scheat from the Arabic for ‘foreleg’. Beta is an M-class (M2.5) red giant that is classed as a semi-regular variable, it ranges in brightness from +2.1 to +3.0. Scheat marks the north-western corner of the ‘Square’. Mercury Date 01 15 30 RA Dec Mag 09h 32m +14° 05' +0.03 10h 54m +08° 55' -1.24 12h 54m -02° 28' -1.44 Phase Dia 39% 7.6" 90% 5.4" 100% 4.8" Rise 04:44 05:32 07:12 Transit 12:01 12:24 13:06 Set 19:18 19:15 18:59 Mercury reaches greatest western elongation on September 3rd when it will be 18 degrees from the Sun. The innermost planet will be visible in the eastern sky before sunrise until the middle of the month. The planet rapidly moves in towards the Sun and it passes through superior conjunction on the 28th. Mercury is at its brightest around mid-month when it will be magnitude –1.2. The chart below shows the position of Mercury at 05:30 on morning of September 3rd. Gamma (γ) Pegasi lies at the south-eastern corner of the ‘Square of Pegasus’, the star has the proper name Algenib; Arabic for ’the side’. Gamma is a magnitude +2.83 B-class (B2) hot white star. Epsilon (ε) Pegasi has the proper name Enif, meaning ‘the nose’. Enif is a Kclass (K2) orange super-giant which shines at magnitude +2.39. Zeta (ζ) Pegasi is a magnitude +3.40 B-class (B8) dwarf Eta (η) Pegasi has the proper name Matar which comes from an Arabic phrase meaning ‘fortunate rain’. Eta is a double star (possibly quadruple), the brighter of the two is a G-class (G2) giant which shines at +2.9. Its companion is an A-class (A5) dwarf star. There are a couple of well known variable stars in Pegasus, R Pegasi and AG Pegasi. R Pegasi is a long period Mira type variable which ranges in brightness from +6.9 to 13.8 over a period of 378 days. Venus Date 01 15 30 RA Dec Mag Phase Dia 11h 01m +07° 47' -3.92 100% 9.7" 12h 05m +00° 49' -3.91 99% 9.8" 13h 13m -06° 46' -3.90 98% 10.0" Rise 06:44 07:28 08:15 Transit 13:28 13:37 13:46 Set 20:12 19:45 19:16 Venus is recovering from last month’s superior conjunction and is not visible this month. Mars Date 01 15 30 20 RA Dec Mag 07h 20m +22° 50' +1.39 07h 58m +21° 34' +1.36 08h 36m +19° 44' +1.30 Phase Dia 93% 4.7" 93% 4.9" 92% 5.1" 5 Rise 01:40 01:31 01:22 Transit 09:52 09:34 09:13 Set 18:03 17:36 17:03 The Planets Constellation of the Month Mars is visible in the early hours of the morning, the planet begins the month in the constellation of Gemini just under 1 degree north of delta (δ) Geminorum. The red planet moves fairly rapidly against the background stars and crosses the border into Cancer on the 16th ending the month less that a degree from the lovely open cluster M44, the Beehive cluster. The chart below shows the position of Mars at 04:00 on September 30th. Pegasus Abbreviation: Peg, Genitive: Pegasi Pegasus is one of the 48 classical constellations named in Ptolemy's Almagest. It is the seventh largest constellation covering an area of 1121 square degrees of the sky. The most recognisable part of the constellation is the asterism known as the ‘Square of Pegasus’ which is formed by the stars alpha, beta and gamma Pegasi and alpha Andromedae (which was previously known as delta Pegasi). Mythology In Greek mythology, Pegasus is the winged horse that sprang from the body of Medusa when Perseus cut of her head. Jupiter Date RA Dec Mag Phase Dia Rise Transit Set 01/02 02h 32m +13° 32' -2.65 99% 45" 21:46 04:59 12:13 15/15 02h 31m +12° 22' -2.75 99% 47" 20:50 04:03 11:15 29/30 02h 27m +12° 59' -2.83 100% 48" 19:53 03:04 10:14 Jupiter rises in the early evening and is visible for most of the night. The giant planet is currently moving in a retrograde direction (east to west) through Aries. During the month Jupiter brightens slightly from magnitude –2.6 to –2.8. The chart on page 7 shows the position of Jupiter at midnight on 16th September. Saturn Date 01 15 30 RA Dec Mag 12h 54m -03° 50' +0.89 12h 04m -04° 27' +0.84 13h 11m -05° 08' +0.77 Phase 100% 100% 100% Dia 16" 16" 16" Rise 09:45 08:58 08:09 Transit 15:28 14:38 13:46 Saturn sets in the early evening and is not visible from the UK this month. Set 21:11 20:19 19:23 When the horse was drinking from a well Bellerophon, the Corinthian hero captured it using a golden bridle given to him by Athena. He was later presented Pegasus as a reward for killing Chimera. However when he attempted to mount the horse it threw him off and rose to the heavens, where it became the constellation we know today. Objects in Pegasus There is just one object from Charles Messier’s catalogue in Pegasus, M15. This lovely example of a globular cluster can be found approximately 4 degrees west-northwest of the double star epsilon (ε) Pegasi. M15 shines at magnitude +6.0 and is an easy object to locate in binoculars. Through a telescope the outer regions can easily be resolved into individual stars. This image of M15 is from a drawing by Chris Lee. There are plenty of galaxies that lie within the boundaries of Pegasus but most are faint. The brightest of these is NGC 7331 which can be found approximately 4 degrees north of eta (η) Pegasi. You will need a reasonable sized telescope to locate this magnitude +9.5 spiral galaxy, which appears as an elongated faint patch which is slightly brighter in the centre. Probably one of the best known galaxy groups in the sky ‘Stephan’s Quintet’ lies 6 19 Thelooking Sky looking East around midnight mid 2011 2011 The Sky west around midnight mid September The Planets Uranus Date 01/02 15/16 29/30 RA Dec Mag 00h 13m +00° 37' +5.73 00h 11m +00° 24' +5.72 00h 09m +00° 11' +5.72 Phase Dia 100% 3.7" 100% 3.7" 100% 3.7" Rise 20:34 19:38 18:42 Transit 02:40 01:43 00:46 Set 08:46 07:48 06:50 Uranus reaches opposition on the 26th in the constellation of Pisces. Although the planet is technically a naked-eye object in reality you will need at least a pair of binoculars to spot it. Uranus can be found around 7 degrees south of omega (ω) Piscium. The chart on page 8 shows the location of the planet and the chart below shows a closer view with the field of view of 10x50 and 7x30 binoculars marked on the chart. Neptune Date 01/02 15/16 29/30 RA Dec Mag 22h 05m -12° 18' +7.82 22h 04m -12° 26' +7.83 22h 03m -12° 33' +7.84 Phase Dia 100% 2.4" 100% 2.3" 100% 2.3" Rise 19:33 18:37 17:42 Transit 00:33 23:37 22:40 Set 05:33 04:36 03:39 Neptune can be found in the constellation of Aquarius just under 1.5 degrees northwest of iota (ι) Aquarii. At magnitude +7.8 Neptune should be visible with binoculars. The chart on page 8 shows the position of Neptune at midnight on the 16th. 18 7 Ceres Date 01/02 15/16 29/30 RA 00h 12m 00h 02m 23h 50m Dec -15° 46' -17° 09' -18° 07' Mag Dia +7.23 0.65" +7.19 0.66" +7.22 0.65" Rise 21:59 21:01 20:01 Transit 02:39 01:34 00:27 Set 07:20 06:06 04:54 Minor planet 1 Ceres reaches opposition on September 16th in the constellation Cetus. At the time of opposition Ceres will be magnitude 7.2 so should be visible in binoculars and small telescopes. Check out the area a few nights before the date of opposition and mark the positions of the stars in the field of view, then check the field on the 16th and the ‘star’ that has moved will be Ceres. The charts show the position of Ceres at midnight on the 16th. 8 Thelooking Sky looking around midnight mid 2011 2011 The Sky NorthNorth around midnight mid September The Sky this Month 17 The looking Sky looking West around midnight mid 2011 2011 The Sky East around midnight mid September The Sky this Month As we move into the autumn season, the longer nights become more noticeable, allowing observing to take place at a more sociable time. This month, low in the southern sky you will find a faint group of constellations which are collectively known as ‘The Water’. The members of this group are Cetus, Capricornus, Aquarius and Pisces and all have a mythological connection with water. Capricornus lies furthest west and is therefore the first of the four to rise in the evening, there is just one Messier object in Capricornus the globular cluster M30. The cluster is visible in binoculars and small telescopes. M30 lies a little over 3 degrees east of zeta (ζ) Capricorni. Lying to the east Capricorn is Aquarius currently home to the planet Neptune. Aquarius is also home to three objects from Charles Messier’s catalogue plus a couple of NGC objects you might like to try to locate. M2 is one of the finest globular clusters visible from the UK. With an apparent magnitude of +6.4 and a diameter of 13 arcminutes, it is an easy binocular object. M2 can be found about 4.5 degrees north of beta (β) Aquarii. M72 is another globular cluster, it is much fainter at magnitude +9.3 and with a diameter of 6 arcseconds its much trickier for observers with small instruments. M72 can be found just over 3 degrees southeast of epsilon (ε) Aquarii. M73 is the last of the Messier objects, it is one of the oddities in the catalogue, it is a Y shaped asterism formed by 4 unrelated stars. M73 can be found 1.5 degrees east of M72. The NGC objects are both planetary nebulae, NGC7009 is known as the ‘Saturn Nebula’ it is the easiest of the pair to locate with a small telescope. The nebula measures 44 x 26 arcseconds and has an over magnitude of +8.3, it can be found around 5 degrees east-southeast of epsilon (ε) Aquarii. The Helix Nebula; NGC 7293 is a more challenging object despite being listed as the brighter of the two at magnitude +7.3. NGC 7293 lies around 1.5 degrees west of upsilon (υ) Aquarii. Pisces lies to the northeast of Aquarius, the most obvious part of the constellation is the asterism known as the ‘Circlet of Pisces’ which lies at its western end. The planet Uranus can currently be found with the constellation. There is just one Messier object in Pisces, M74. This lovely face-on spiral galaxy can be found at the eastern end of Pisces around 1.5 degrees east-northeast of eta (η) Piscium. M74 has an apparent magnitude of +9.4 and due to its low surface brightness it is one of the more difficult Messier objects to locate. Below Pisces you will find Cetus, home to the well known variable star Mira; omicron (ο) Ceti. Mira is the type star of a class of long period variables whose 16 9 brightness varies due to pulsation in the star. Mira is normally around magnitude +9, however when it brightens it can reach magnitude +2. Mira is visible with binoculars throughout its brightness range, the next maximum is due between 21st and 30th of this month. Mira is visible to the naked eye for around 6 weeks before and 3 months after maximum. You can find Mira at RA 02h 19.3m Dec -02° 59'. There is just one Messier object in Cetus, M77. This face on spiral galaxy can be found just over 1 degree southeast of delta (δ) Ceti. M77 has an apparent diameter of 8 arcminutes and an overall magnitude of +8.9. High in the southern sky you will find this months featured constellation Pegasus (see pages 19 to 22) Running in a north-easterly direction from Pegasus you will find the constellation of Andromeda. Approximately midway along this line of stars you will find our closest large galactic neighbour M31, the Andromeda Galaxy. M31 can be seen with the naked-eye from a dark location and is a very easy object to locate with binoculars. The galaxy has a couple of close neighbours of it’s own M32 and M110. You will need a telescope to spot these two companion galaxies. To the East of Andromeda you will find the small constellation of Triangulum, home to another of our galactic neighbours, M33. Like M31 this is a large spiral galaxy similar to our own Milky Way. M33 is a much more challenging object due to it’s low surface brightness and requires dark skies and very good seeing conditions. If you follow the line of stars that forms the body of Andromeda it will lead you to the constellation of Perseus. Beta (β) Persei; Algol is an Eclipsing Binary type variable which is normally magnitude +2.1, but during an eclipse the star dims to 10 Thelooking Sky looking around midnight mid 2011 2011 The Sky SouthSouth around midnight mid September The Sky this Month 15 The Sky looking Overhead around midnight mid September 2011 The Sky this Month magnitude +3.4. This happens every two days, 20 hours and 49 minutes. Good comparison stars are α Andromedae +2.06 and κ Persei +3.78. You can find the date and time of the minima of Algol from the Sky & Telescope website at http://www.skyandtelescope.com/observing/objects/variablestars/Minima_of_Algol.html There are a couple of Messier object in Perseus, M34 is an open cluster which lies approximately midway between κ Persei and γ Andromedae. M76 is a planetary nebula which is also known as the ‘Little Dumbbell’. M76 can be found around one degree north of phi (φ) Andromedae. To the north of Perseus lies the ‘W’ shape of Cassiopeia. The centre star of the ‘W’, is gamma (γ) Cassiopeiae, this is a naked-eye variable, which ranges in brightness at irregular intervals between magnitude +2.20 and +3.40. There is just one Messier object in Cassiopeia, the open cluster M103, which can be found close to delta (δ) Cassiopeiae. Between Perseus and Cassiopeia, lies the famous ‘Double Cluster’ h and chi (χ) Persei also know as NGC 884 and NCG 896. The double cluster is a lovely sight in binoculars. Below Perseus you will find Auriga. The bright yellow star Capella; alpha (α) Aurigae; makes the constellation easy to identify. There are three Messier objects in Auriga, all open clusters M36, M37 and M38. All three clusters are visible as hazy patches in binoculars and small telescopes will reveal the individual stars. Around midnight the northern part sky is fairly blank, Ursa Major and its well known asterism ‘The Plough’ is likely to be the only recognisable constellation in the lower part of the sky. Polaris, the pole star lies midway between the horizon and the zenith and marks the tip of the tail of Ursa Minor. High overhead you will find one of the signature constellations of the summer sky, Cygnus. The tail of the swan (northern end) is marked by the constellation’s brightest star Deneb; alpha (α) Cygni, one of the trio stars that form the ‘Summer Triangle’, the other two are Vega; α Lyrae and Altair α Aquilae. The star at the southern end of Cygnus, marking the swan’s beak, is the well known double star Albireo, β Cygni. The contrasting colours of yellow/orange and blue /green make this one of the most pleasing double stars in the sky. Cygnus seems to be flying south along the Milky Way and scanning this area of the sky with binoculars can occupy you for many hours on a warm autumn night. To the west of Cygnus lies the small constellation of Lyra which is home to one of the finest examples of a planetary nebula in the sky, M57, the Ring Nebula. M57 can be found midway between beta (β) and gamma (γ) Lyrae. 14 11 The Sky This Month To the east of Cygnus you will find the ‘crooked house’ shaped constellation of Cepheus. At the south-eastern 01 Sep 01:00 16 Sep 00:00 30 Sep 23:00 corner lies a small triangle of stars, zeta (ζ), epsilon (ε) and delta (δ). Delta Cephei is the prototype of the Cepheid class of variable stars. Delta varies between magnitude +3.5 and + 4.4 every 5 days 8 hours 48 minutes. The stars epsilon +4.19 and zeta + 3.35 are good comparison stars. Delta is also a binary star, its companion is a magnitude +6.3 blue star, the pair are separated by 41 arcseconds . The constellation of Hercules lies in the western sky, it is home to a couple of the best globular clusters in the northern hemisphere, M13 which lies between eta (η) and zeta (ζ) Her and M92 north of pi (π) Her. Chart Produced by Chris Peat http://www.heavens-above.coom 12 13