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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