Society News. Bristol Astronomical Society Information Leaflet February 2011

Transcription

1 Society News AGM This year our AGM will be held on Friday 11th of February. At the AGM the entire committee stand down, and any fully paid up member over the age of 18 is entitled to stand for any position on the committee. There are three named officers, Chairman, Secretary and Treasurer plus a further 9 positions for committee members. There are also two posts for junior members (under 18). If you think that you have something to offer the society and would like to stand for one of the positions on the committee, nomination forms will be available at all our meetings up to the AGM. You can also download one from the documents section of the website. Both the nominee and the person nominating them must sign the form. Bristol Astronomical Society Information Leaflet February 2011 Saturday Observing Sessions The open observing sessions have restarted, the observatory will be open each clear Saturday and anyone, members and non-member are welcome to come along. We hope to have a number of scopes available each evening, we also hope to have someone available to give newcomers to astronomy a quick tour of the sky pointing out the major constellations. Check the observing status on the website on Saturday evening to check whether the session is going ahead or not. If the weather is a bit suspect the decision will not be made until the last minute. Programme of Events for 2011 All meetings are held at Bristol Grammar School, University Road BS8 1SR 4th Feb Club Night - Richard Mansfield 11th Feb AGM 18th Feb Club Night - Mike Cowles 25th Feb The Cosmic Keyhole - how astronomy is unlocking the secrets of the Universe - Will Gater Don t forget to check out the BAS website where you can get all the latest info about the society. Bristol Astronomical Society are a Registered Charity, No NGC 2403 in Camelopardalis 1

2 The The Sun & Sun Moon Sun and Moon Rise and Set times for February 2011 Sun Moon Date Rise Set Rise Set 01 07:49 16:59 06:47 15: :48 17:01 07:13 16: :46 17:03 07:34 17: :44 17:05 07:52 19: :43 17:07 08:08 20: :41 17:08 08:23 21: :39 17:10 08:39 22: :38 17:12 08:55 23: :36 17:14 09: :34 17:16 09:38 00: :32 17:18 10:08 01: :30 17:19 10:47 02: :29 17:21 11:38 03: :27 17:23 12:42 04: :25 17:25 13:57 05: :23 17:27 15:19 06: :21 17:28 16:46 06: :19 17:30 18:14 06: :17 17:32 19:41 07: :15 17:34 21:08 07: :13 17:36 22:35 07: :11 17:38 23:58 08: :09 17:39 08: :07 17:41 01:17 09: :05 17:43 02:28 10: :03 17:45 03:27 11: :01 17:46 04:13 12: :58 17:48 04:49 13:23 2 Camelopardalis & Lynx 23

3 Constellation of the Month pair are separated by 2.7 arcseconds (PA 229 ). When you at these stars, what colours do you think are? Some reports say that the primary looks green others that it appears white with the secondary being blue or lilac. The primary star is a spectroscopic binary, the two visual components are sometimes referred to as A and C or AB and C. There is fourth component 88 arcseconds away at PA 212, which is around magnitude Lyncis is a triple star with components of magnitude (A) +5.4, (B) +6.0 and (C) Components A and B are both blue/white A-class stars separated by just 1.8 arcseconds (PA 70 ). A and C are separated by 8.5 arcseconds (PA 308 ). Small instruments should split the A and C pair while larger telescopes will be needed to split the A-B pair. 19 Lyncis is another multiple star the primary (A) is another spectroscopic binary, magnitude It s magnitude +6.5, visual companion (C) lies 15 arcseconds away at PA 315. Both A and C components are B-class stars. Objects in Lynx Object NGC Type Mag RA Dec Intergalactic 2419 Globular Cluster h 38.1m ' Wanderer UFO Galaxy 2683 Spiral Galaxy h 52.7m ' 12 Lyncis Multiple Star +5.4 & +6.0 & h 46.2m ' 19 Lyncis Multiple Star +5.6 & h 22.8m ' 38 Lyncis Multiple Star +3.8 & h 18.8m ' The Sun & Moon The Sun Due to the cloud cover we saw nothing of last months partial solar eclipse here in the Bristol area but there is plenty of activity that is visible on the Sun (when the weather allows). Sunspots are easy to see using even the smallest telescope or even binoculars by projecting an image of the Sun on to a piece of shaded card or paper. 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 white background. If you are using binoculars please remember to keep the side you are not using covered. It is important to remember that you should never look directly at the Sun with any optical equipment as this will cause permanent damage to your eyes. The society has a Hydrogen Alpha solar telescope which is great for looking at solar prominences, large jets of material ejected from the surface of the Sun. Prominences are most easily seen around the edge of the Sun as can be seen in the image (left). The society s solar observers provide regular reports via the society s Yahoo Group mailbox when there are any sunspots visible. To join our Yahoo group visit and follow the link to join. During the summer months we hold regular solar observing sessions at the National Trust estate at Tyntesfield and any members are welcome to come along to help out and of course, have a look through the telescopes. Take the opportunity to observe these constellations while they are high in the sky and if you record any of your observations please pass copies on to John Meacham (Dir of Observations) and myself for publication in Eclipse. The Moon 3rd 02:31 11th 07:18 18th 08:36 24th 23:26 This month we look at the walled plain, Grimaldi, a walled plain is a feature that is too big to be a crater and a too small to be a Mare (Sea). Grimaldi lies to the southwest of the Oceanus Procellarum, close to the western limb of the Moon. Due to the foreshortening effect of being close to the lunar limb it appears elliptical, it is in fact circular with a diameter of 222 km (134 miles). Grimaldi has an extremely dark floor making it easy to identify. On the northern rim of the plain lies the small 22km diameter crater Grimaldi B which has damaged the out- 22 3

4 The Sun & Moon er wall of the plain. Although the walls have been has been heavily damaged and eroded by later impacts there are still a few peaks that rise to over 2 km. The outer slopes are steep and riddled with many small craterlets including Grimaldi K, L, M, N and P to the South and D, Grimaldi E & Q to the Northeast. To the Southeast of the plain you will find Rimae Grimaldi. For those with larger instruments there are a number of small craterlets on the floor of the plain you might be able to pick out. Grimaldi Lat 5.2 South Lon 68.6 West. The best time to see Grimaldi is either 6 days after First Quarter (17th ) or 5 days after Last Quarter (1st Mar). Minimal Instrument: 10x binoculars. 4 Grimaldi B Constellation of the Month Lynx Abbreviation: Lyn - Genitive: Lyncis Lynx is a fairly modern constellation, introduced by Johannes Hevelius in his 1690 catalogue, which was published three years after his death. Lynx lies in a sparse region of the northern sky and is bounded by Camelopardalis to the north, Auriga to the east, Gemini and Cancer to the south and Leo Minor and the Ursa Major to the west. Objects in Lynx The constellation of Lynx contains no Messier objects but there are a few NGC objects that are worth a look. NGC 2419 is a globular cluster that lies at a distance of over 300,000 lightyears from both the Earth and the galactic centre, one of the most remote in the galaxy. At magnitude it is visible in medium sized telescopes. It was once thought that the cluster was not linked to the Milky Way which led to its alternative of the Intergalactic Wanderer. The cluster can be found approximately 4 degrees north of omicron (ο) Geminorum. NGC 2683 is a spiral galaxy (Sb Type) which we see almost edge on. The galaxy lies in the southern half of the constellation close to the border with Cancer, just over 4 degrees north of iota (ι) Cancri. NGC 2683 has an apparent diameter of 9.3 x 2.2 arcminutes and is magnitude Medium to large instruments are required to see this object. NGC 2683 is also known as the UFO galaxy. Stars in Lynx Lynx is another faint constellation, just one of its stars was prominent enough to have been given a proper name, Alsciaukat; (31 Lyncis), which come from an Arabic phrase and refers to a Thorn. Alsciaukat is a magnitude K-class (K7) orange giant which lies about 2/3 of the way from Castor (α Geminorum) to Tabitha (ι Ursa Majoris). Alpha (α) Lyncis lies at the eastern end of the constellation, it is the only star in Lynx to carry a Bayer letter. Alpha is another K-class (K5) orange giant with an apparent magnitude of Approximately 3 degrees north of alpha lies 38 Lyncis, a nice visual double star for small telescopes. The primary is a magnitude A-class (A3) dwarf star, its companion is, also an A-class (A4) star but much fainter at magnitude +6.6, the 21

5 Constellation of the Month Stock 23 is an open cluster that is visible in binoculars and small telescopes, it lies close to the border with Cassiopeia around 10 degrees northwest of alpha Persei. Binoculars will show the cluster as a small tight group of stars. A telescope will reveal a keystone shaped group of four 6th magnitude stars at the centre surrounded by a further 20 to 25 fainter stars. Stars in Camelopardalis The constellation s brightest member is beta (β) Cam, a magnitude +4.03, G-class (G0), yellow supergiant. Beta is a multiple star, the secondary, which is itself double, lies just over an arcminute away at position angle 208º. It is a magnitude +9, A-class star, its companion is an F-class star which is around magnitude +11. Alpha (α) Camelopardalis ranks as only the third brightest star in the constellation at magnitude It is a rare blue-white O-class (O9.5) supergiant, that appears faint to us due to its distance of over 3000 light-years. It was once thought that alpha Cam was a member of NGC 1502 that had ejected by either interactions within the cluster or by the explosion of a nearby star. Recent observations now cast doubt on that theory. Gamma (γ) Cam, the northernmost of the brighter stars, is a white A-class (A2) subgiant with an apparent magnitude of Z Cam is a Dwarf Nova type variable similar to U Geminorum but with more frequent outbursts. Outbursts occur approximately couple of weeks, when the star can brighten to magnitude When the star is not in outburst it is normally magnitude +14. Like all stars of this type, Z Cam is a very close binary system where matter is transferred from one star to the other. It is this transfer of material which is the cause of the dramatic brightening in this type of variable star. Objects in Camelopardalis Object NGC Type Mag RA Dec 1502 Open Cluster h 07.7m ' 2403 Spiral Galaxy h 36.9m ' Stock 23 Open Cluster h 16.3m ' Z Cam Variable Star h 25.2m ' 20 The Planets Mercury 01 19h 50m ' % 5.1" 07:17 11:19 15: h 23m ' % 4.8" 07:24 11:57 16: h 53m ' % 5.0" 07:16 12:33 17:50 Mercury is at superior conjunction with the Sun on the 25th and is not visible from the UK this month. Venus 01 17h 43m ' % 20" 05:00 09:11 13: h 52m ' % 17" 05:15 09:24 13: h 56m ' % 16" 05:20 09:38 13:5 Venus remains a stunning object low in the south-eastern sky in the hours before sunrise. As the month progress the planet s brightness drops very slightly from magnitude 4.26 to 4.11, the gibbous phase increases by 10% from 61% to 71% of the disc is illuminated. Mars 01 21h 04m ' % 3.9" 08:00 12:28 16: h 47m ' % 4.0" 07:28 12:16 17: h 27m ' % 4.0" 06:57 12:05 17:12 Mars is in conjunction with the Sun on the 4th and is therefore not visible this month. Jupiter 01 00h 08m ' % 36" 09:31 15:33 21: h 19m ' % 35" 08:41 14:48 20: h 29m ' % 34" 07:55 14:08 20:21 Jupiter can be found in the south-western sky in the early evening. The giant planet sets just a couple of hours after the Sun by the end of the month. Jupiter moves from Pisces across the border in to neighbouring Cetus towards the end of the month. The following is a list of times when the Great Red Spot (GRS) cross- 5

6 The Planets Constellation of the Month This month we take a look at two of the lesser known northern constellations Camelopardalis and Lynx. Camelopardalis Abbreviation - Cam. Genitive - Camelopardalis es the central meridian of Jupiter, that are visible from the UK. February 1 st 19:45; 3 rd : 21:25; 6 th 18:56; 8 th 20:35; 11 th 18:06; 13 th 19:45; 18 th 18:56; 25 th 19:45. The table below shows a few of the events involving the Galilean Moons these can be seen with small telescopes. A full list of event can be found in monthly magazines. Date Event Start End 02/02 Transit of Io 20:17 22:37 04/02 Occultation of Ganymede 18:18 21:38 07/02 Europa Shadow Transit 16:43 19:31 15/02 Ganymede Shadow Transit 16:42 19:46 18/02 Io Transit 18:51 21:11 26/02 Occultation of Io 18:02 20:21 Saturn 01/02 13h 06m ' % 18" 22:48 04:29 10:10 14/15 13h 05m ' % 19" 21:55 06:37 09:18 27/28 13h 08m ' % 19" 21:05 02:48 08:31 Saturn can be found in rising the eastern sky before midnight, the ringed planet is moving in a retrograde direction through Virgo. The rings are slowly opening out, and are tilted at an angle of around 10 degrees, the northern (top) edge towards us. The picture (right) shows the planet at 02:00 on the 27th of the month. 6 Camelopardalis (the Giraffe) is a large modern constellation which covers an area of 757 square degrees of the northern sky (18th largest). From the latitude of Bristol the constellation is circumpolar The constellation was created by the Dutch cartographer Petrus Plancius and first appeared on a globe in Camelopardalis is a faint constellation, none of its stars are brighter than fourth magnitude and none carry a proper name, only three are bright enough for Johannes Bayer to have assigned them a Bayer letter in his Uranometria published in Objects in Camelopardalis There are no objects from Charles Messier s catalogue within the boundaries of Camelopardalis and just a few from New General Catalogue (NGC) that may be of interest to deep sky observers. NGC 1502 is a small open cluster containing around 45 stars the brightest of these being magnitude +7. The cluster is located around ten degrees west of beta (β) Cam and is a quite a nice cluster for small telescopes. Probably the best object in the constellation can be found running in an almost straight line in a north-westerly direction from NGC1502. Kemble s Cascade is an unrelated string of 15 to 25 stars ranging in brightness from the 5th to the 9th magnitude, spread over an area of 2.5. This asterism is best seen with binoculars and the number of stars you will see is dependant on the size of the binoculars you use. It is named after its discoverer, Father Lucian Kemble, who described it as a beautiful cascade of faint stars tumbling from the Northwest down to the open cluster NGC NGC 2403 is face on spiral galaxy which can be found around six degrees to the northwest of omicron (ο) Ursae Majoris. The galaxy is similar in appearance to M33, it has an integrated magnitude of +8.5 with a bright core. It is a member of the M81 group of galaxies. NGC 2403 is noted for its exceptionally bright HII regions and high rate of star formation. 19

7 The Planets The Sky looking East around midnight mid February 2011 Uranus 01 23h 53m ' % 3.4" 09:22 15:18 21: h 56m ' % 3.4" 08:28 14:25 20: h 58m ' % 3.4" 07:38 13:37 19:35 Uranus can be found in the constellation of Pisces around 4 degrees southwest of lambda (λ) Piscium. The chart on page 6 shows the position of the planet around 18:30 on the 15th, you will need binoculars or a small telescope to see Uranus. Neptune 01 21h 59m ' % 2.2" 08:27 13:25 18: h 01m ' % 2.2" 07:33 12:32 17: h 03m ' % 2.2" 06:39 11:39 16:38 Neptune will be in conjunction with the Sun on 17th so will not be visible this month. 18 7

8 The Sky this Month High overhead, around midnight you will find one of our featured constellations, Lynx; this faint group of stars can be difficult to locate from light polluted areas. To the southeast of Lynx is another faint constellation, Leo Minor. The brightest star in the constellation at magnitude is 46 LMi. Only one star in Leo Minor has a Bayer letter, oddly enough its beta LMi not alpha LMi. R Leonis Minoris is long-period Mira type variable star which varies in brightness between magnitude +6.3 and over a period of 372 days. Like all Mira type variables R LMi is a red giant star nearing the end of its life. To the north of Lynx lies our other featured constellation Camelopardalis, this is another faint group of stars and like Lynx and Leo Minor it is a fairly new constellation, first appearing in the 1600 s. Around midnight the northern sky is dominated by the constellations of Cepheus and Cassiopeia. There are a couple of interesting variables in these constellations which are periodically check by members of the society. Delta (δ) Cephei is the prototype for the Cepheid Variables (used in measuring the scale of the universe), it lies in southwest corner of the Crooked House shape. Delta varies in brightness from magnitude +3.6 to +4.3 every 5.36 days, it also varies in spectral type from about F5 to G3. Gamma (γ) Cassiopeiae varies in brightness at irregular intervals between magnitude and As gamma Cas is a naked-eye object throughout its brightness range and its circumpolar, therefore its visible throughout the year, its an excellent star to begin your variable star observing. There are two of Messier s open clusters in Cassiopeia, M52 and M103. M52 is one of the brighter open clusters in the sky with an The Sky looking North around midnight mid February

9 The Sky looking West around midnight mid February 2011 The Sky this Month overall magnitude of The cluster can be found near the western edge of Cassiopeia close to the border with Cepheus. M103 lies a little over 1 degree northeast of delta (δ) Cas, with an overall magnitude of +7.4, it is well within reach of binocular observers. West of Cassiopeia lies the Y shaped constellation of Perseus, lying between these two constellations you will find the lovely Double Cluster NGC869 and NGC884. This pair of open clusters are easy to observe with binoculars or a small telescope. There are a couple of Messier objects in Perseus, the open cluster, M34 and the planetary nebula M76 which is also known as the Little Dumbbell. Beta Persei, Algol, is a famous variable star, which varies in brightness due to the larger, brighter star being eclipsed by a smaller fainter companion. The eclipses occur like clockwork every two days, 20 hours and 49 minutes when the star dips from magnitude +2.1 to magnitude To the south of Perseus you will find the irregular pentagon shape of Auriga, home to three of Messier s open clusters, M36, M37 and M38. All three clusters are visible with binoculars and small telescope. Epsilon (ε) Aurigae lies at the apex of a triangle of stars which lie just below Capella, known as the Kids, the other two stars are Hoedus I and II. Epsilon is a very unusual variable star, it is an eclipsing binary which has the longest period of any known binary system, 27.1 years. Each eclipse last over two years with the star, an F-class (F0) giant, fading from its normal level of magnitude of +3.0 to around magnitude Mid-eclipse occurred in August last year, we no nothing about the eclipsing object which is thought to be a large disc of gas and dust that passes between us and the star. To the west of Auriga and linked to it by beta (β) Tauri the star which marks the south-eastern corner of the familiar pentagon shape of Auriga, you will find the 16 9

10 The Sky this Month bright constellation of Taurus. Taurus is home to a couple of Messier objects, M1 and M45. M1, the Crab Nebula is one of the most famous deep-sky objects in the sky. This glowing cloud of material is the remnant of supernova explosion observed by Chinese astronomers in M1 can be found just to the northwest of zeta (ζ) Tauri which marks the tip of the southern horn of the bull. You will need a fairly large telescope to see this object. M45, the Pleiades is a naked-eye cluster of young hot stars which are stunning sight in binoculars. To the southwest of Taurus you will find Orion, for me the defining constellation of winter. The outstanding object in Orion is without doubt Orion Nebula, M42, this huge cloud of gas and dust is easily visible with the naked-eye below the belt stars. Binoculars will reveal the bright central part of the nebula and the hot young stars at its centre which illuminates the gas. Large telescopes will reveal a wealth of detail in this stellar nursery. The view of M42 through the society s 18inch reflector is absolutely stunning, the nebula appears almost 3D. There are a couple of other Messier objects in Orion, M43 which is part of the Orion nebula and lies just above M42 and M78, a reflection nebula which lies just north of zeta (ζ) Orionis. To the southeast of Orion you will find the small constellation of Canis Major which is home to the brightest star in the sky Sirius. To the northeast of Orion you will find Gemini, the constellation s two brightest stars, Castor (α Gem) and Pollux (β Gem) mark the heads of the celestial twins. Lying at the feet of Castor you will find the bright open cluster M35, this cluster should be visible to the naked-eye from a very dark location and is a wonderful sight in binoculars. High in the southern sky during February you will find the faint constellation of Cancer, from light polluted areas it can difficult to see the stars that form Cancer as the brightest star (beta Cancri) is just magnitude There are a couple of Messier objects in Cancer, M44 and M67 both open clusters. M44, also known as Praesepe or the Beehive cluster is visible with the naked-eye from a dark site and is a spectacular sight in binoculars and small telescopes. M67 is one of the oldest known open clusters at around at 3.2 billion years, it lies just to the west of alpha (α) Cnc. Lying below Cancer and meandering towards the south-eastern horizon is the constellation The Sky looking South around midnight mid February

11 The Sky looking Overhead around midnight mid February 2011 The Sky this Month of Hydra. There are three Messier objects in Hydra, M48 is an open cluster which lies at the western end of Hydra right on the border with Monoceros. M68 is a very nice globular cluster which also lies at the western end of the constellation, just to the west of gamma (γ) Hydrae. The last of the Messier objects is M83, a lovely face-on spiral galaxy located to the south of gamma Hydrae close to the border with Centaurus. In the south-eastern sky you will find the large constellation of Leo. There are a number of galaxies which lie within the constellation s boundaries including five Messier objects, M65, M66, M95, M96 and M105. M65 and M66 along with NGC 3628 form a conspicuous triplet of galaxies which can be found about mid-way between theta (θ) and iota (ι) Leonis. M95, M96 and M105 form another group which can be found towards the western end of Leo just to the south of 52 Leonis. You will need a telescope to observe these objects. In the eastern sky the constellations of spring are beginning to rise at a reasonable hour. The galaxy rich area of Virgo and Coma Berenices can be found low in the south-eastern sky around midnight. There are enough galaxies in this region to keep any deep-sky observer happy, literally hundreds of galaxies that are visible in amateur telescopes. Virgo is currently home to Saturn. Further around to the east you will find the Kite shaped constellation of Boötes with the bright orange, Arcturus marking the base of the kite. At magnitude

12 The Sky This Month Arcturus is the brightest star in the northern half of the sky and the fourth brightest in the sky. High in the north-eastern sky you will find Ursa Major, it s seven brightest stars forming the well known asterism, the Plough or the Saucepan as it is more commonly called. There are quite a few deep-sky objects in Ursa Major, with seven making it to the final Messier list. M40 is an odd object as it is just a double star which is also known as Winnecke 4. The galaxy pair M81 (spiral galaxy) and M82 (irregular galaxy) are a lovely sight through a telescope. To locate this pair of galaxies, draw a line from gamma (γ) UMa diagonally across the bowl of the plough to alpha (α) UMa and extend it by the same distance. The galaxies should be visible in the same field. 01 Feb 01:00 15 Feb 00:00 28 Feb 23:00 M97 is a faint planetary nebula which is also known as the Owl nebula. It lies just to the southeast of beta (β) UMa. You will need a medium to large telescope to spot this object. M101, M108 and M109 are all spiral galaxies. M101 lies north of eta (η) close to the border with Boötes. M108 lies between M97 and beta (β) UMa and M109 can be found just to the east of gamma (γ) UMa. M102 is thought to be a duplicate observation of M101, however another view is that it is NGC 5866 a Lenticular galaxy in Draco. Messier's description of the object seems to be a good match, and together with the position he later added by hand in his personal copy of the catalogue, it seems a more likely candidate. Chart Produced by Chris Peat