Bristol Astronomical Society Information Leaflet April 2015

Transcription

1 Bristol Astronomical Society Information Leaflet April 2015 Solar Eclipse, Castle Park, Bristol, 20 th March

2 Sunday Monday Tuesday Wednesday 5 Sunrise: 6:38 Sunset: 19:48 Moonrise: 21:03 Moonset: 7:05 12 Sunrise: 6:23 Sunset: 20:00 Moonrise: 2:47 Moonset: 12:14 Virginid meteor shower Moon at Last Quarter: 04:46 19 Sunrise: 6:08 Sunset: 20:12 Moonrise: 6:40 Moonset: 21:17 Mercury at perihelion Observing Calendar April Sunrise: 6:36 Sunset: 19:50 Moonrise: 22:07 Moonset: 7:32 Uranus at solar conjunction 13 Sunrise: 6:20 Sunset: 20:02 Moonrise: 3:28 Moonset: 13:25 20 Sunrise: 6:06 Sunset: 20:13 Moonrise: 7:17 Moonset: 22:30 7 Sunrise: 6:34 Sunset: 19:52 Moonrise: 23:10 Moonset: 8:03 The Moon at aphelion C/2012 F3 (PANSTARRS) at perihelion 14 Sunrise: 6:18 Sunset: 20:03 Moonrise: 4:04 Moonset: 14:41 M51 is well placed (21:21 04:51) 21 Sunrise: 6:03 Sunset: 20:15 Moonrise: 7:59 Moonset: 23:37 1 Sunrise: 6:47 Sunset: 19:42 Moonrise: 16:52 Moonset: 5:31 The Moon at apogee M104 is well placed (23:57-02:26) 8 Sunrise: 6:32 Sunset: 19:53 Moonrise: none Moonset: 8:38 Conjunction between the Moon and Saturn 15 Sunrise: 6:16 Sunset: 20:05 Moonrise: 4:37 Moonset: 16:00 22 Sunrise: 6:01 Sunset: 20:17 Moonrise: 8:46 Moonset: none Thursday Friday Saturday Saturday Observing 2 Sunrise: 6:45 Sunset: 19:43 Moonrise: 17:54 Moonset: 5:54 9 Sunrise: 6:29 Sunset: 19:55 Moonrise: 0:11 Moonset: 9:21 16 Sunrise: 6:14 Sunset: 20:07 Moonrise: 5:07 Moonset: 17:19 The Moon at perihelion 23 Sunrise: 5:59 Sunset: 20:18 Moonrise: 9:39 Moonset: 0:35 Lyrid meteor shower M101 is well placed (21:52-04:27) Observing Calendar April Sunrise: 6:43 Sunset: 19:45 Moonrise: 18:56 Moonset: 6:17 10 Sunrise: 6:27 Sunset: 19:57 Moonrise: 1:08 Moonset: 10:10 Mercury at superior solar conjunction 17 Sunrise: 6:12 Sunset: 20:08 Moonrise: 5:37 Moonset: 18:40 The Moon at perigee M3 is well placed (21:38 04:43) 24 Sunrise: 5:57 Sunset: 20:20 Moonrise: 10:36 Moonset: 1:24 4 Sunrise: 6:40 Sunset: 19:47 Moonrise: 20:00 Moonset: 6:41 Full Moon: 13:07 M94 is well placed (from 21:11) 11 Sunrise: 6:25 Sunset: 19:58 Moonrise: 2:01 Moonset: 11:08 Conjunction between Venus and M45 (20:21 00:05) 18 Sunrise: 6:10 Sunset: 20:10 Moonrise: 6:07 Moonset: 20:00 Venus at perihelion New Moon: 19:58 25 Sunrise: 5:55 Sunset: 20:22 Moonrise: 11:36 Moonset: 2:04 No public observing Stephen Price Jane Clark Nigel Kirkland No public observing John Willis Nigel Kirkland Simon Perks 26 Sunrise: 5:53 Sunset: 20:23 Moonrise: 12:38 Moonset: 2:39 Moon at First Quarter: 00:56 27 Sunrise: 5:51 Sunset: 20:25 Moonrise: 13:40 Moonset: 3:08 28 Sunrise: 5:49 Sunset: 20:27 Moonrise: 14:41 Moonset: 3:34 α Scorpiid meteor shower 29 Sunrise: 5:47 Sunset: 20:28 Moonrise: 15:44 Moonset: 3:58 The Moon at apogee 30 Sunrise: 5:45 Sunset: 20:30 Moonrise: 16:46 Moonset: 4:21 Data from:

3 The Sun Sun s Position at Midday 15th April 2015 The Moon April 11th and 28th: Two Great Lunar Craters This are two good nights to observe two of the greatest craters on the Moon, Tycho and Copernicus, as the terminator is nearby. Tycho is towards the bottom of Moon in a densely cratered area called the Southern Lunar Highlands. It is a relatively young crater which is about 108 million years old. It is interesting in that it is thought to have been formed by the impact of one of the remnants of an asteroid that gave rise to the asteroid Baptistina. Another asteroid originating from the same breakup may well have caused the Chicxulub crater 65 million years ago. It has a diameter of 85 km and is nearly 5 km deep. At full Moon - seen in the image below - the rays of material that were ejected when it was formed can be see arcing across the surface. Copernicus is about 800 million years old and lies in the eastern Oceanus Procellarum beyond the end of the Apennine Mountains. It is 93 km wide and nearly 4 km deep and is a classic "terraced" crater. Both can be seen with binoculars. Solar Events for 2015 Tycho and Copernicus Full Moon showing Tycho's rays 4 5

4 The Moon The Planets (1 st, 15 th & 30 th at 00:00) Plato and the Alpine Valley. Craterlets are seen on the floor of Plato and the rille along the centre of the Alpine valley is clearly visible Apr 1 st Mercury Venus Mars Jupiter Saturn Uranus Neptune RA 0 h 9 m 2 h 58 m 1 h 52 m 9 h 1 m 16 h 12 m 1 h 0 m s 22 h 41 m Dec -1 5' ' 17 55' ' 5 46' -9 4' Range Mag Const Pisces Aries Aries Cancer Scorpius Pisces Aquarius Transit 12:45 15:33 14:26 21:32 04:46 13:32 11:14 Rises 06:49 07:57 07:27 13:57 00:28 07:05 06:01 Sets 18:43 23:11 21:25 05:11 09:03 20:00 16:26 Apr 15 th Mercury Venus Mars Jupiter Saturn Uranus Neptune RA 1 h 51 m 4 h 6 m 2 h 32 m 9 h 1 m 16 h 10 m 1 h 3 m 22 h 43 m Dec 11 26' 22 32' 14 59' 17 54' ' 6 4' -8 54' Range Mag Const Aries Taurus Aries Cancer Scorpius Pisces Aquarius Transit 13:33 15:46 14:11 20:37 03:48 12:40 10:20 Rises 06:32 07:39 06:52 13:02 23:26 06:11 05:07 Sets 20:37 23:53 21:29 04:16 08:06 19:10 15:34 Apr 30 th Mercury Venus Mars Jupiter Saturn Uranus Neptune RA 3 h 42 m 5 h 20 m 3 h 15 m 9 h 4 m 16 h 6 m 1 h 6 m 22 h 44 m Dec 22 3' 25 27' 18 16' 17 42' ' 6 23' -8 46' Range Mag Const Taurus Taurus Aries Cancer Scorpius Pisces Aquarius Transit 14:23 16:01 13:55 19:41 02:46 11:44 09:23 Rises 06:20 07:33 06:17 12:07 22:22 05:13 04:09 Sets 22:28 00:27 21:33 03:18 07:05 18:15 14:

5 The Planets Mercury Mercury passes behind the Sun (superior conjunction) on the 10th of April, so cannot be seen until later in the month. By the 19th, shining at magnitude -1.4, it should become visible very low in the west-northwest about 45 minutes after the Sun has set. It will gradually rise higher in the sky until the 7th of May when it reaches its greatest elongation east of ~22 degrees. April 19th: A great observing challenge! Mars, Mercury and a very thin crescent Moon: After sunset, and given a clear sky and low western horizon, you may be able to see a very thin crescent Moon forming an almost equilateral triangle with Mars (at magnitude 1.4) and Mercury (at magnitude -1.4). Their separations are between 4 and 5 degrees. The Moon will just under one day old and this is essentially the soonest after New Moon that it is possible to be observed. Binoculars or a small telescope with a low power eyepiece may well be needed. Venus Venus is shining brightly at magnitude ~-4 all month and rises higher in the western sky after sunset as the month progresses. It starts the month in Aries, but climbs up into Taurus on April 7th, lying just to the east of the Pleaides cluster on the 13th. A telescope will show its angular size increasing from 14 to 16 arc seconds whilst it illuminated phase shrinks from 78% to 68%. The Planets Mars Mars,having graced our evening skies for many months is now finally sinking down into the Sun's glare. It will lie close to, far brighter, Mercury around the 19th to 24th April. With an angular size of just 4 arc seconds, no details will be seen on its, near fully illuminated, salmon pink surface. Jupiter Jupiter is now two months past opposition but this is still a good month to observe it - high in the south-western sky during the evening. Its brightness falls slightly from magnitude -2.3 to -2.1 whilst its angular size drops from 41.5 to 38 arc seconds. Jupiter spends the month in Cancer, hardly moving as it ends its retrograde motion westwards on the 11th of the month and slowly begins its eastwards progress towards Leo. With a small telescope one should be easily able to see the equatorial bands in the atmosphere, sometimes the Great Red Spot and up to four of the Gallilean moons as they weave their way around it. April: Look for the Great Red Spot on Jupiter: This list gives some of the best evening times during April to observe the Great Red Spot which should then lie on the central meridian of the planet. 1st 20:19 18th 19:24 3rd 21:58 20th 21:03 April 21st: Venus, the Moon and the Hyades Cluster: An hour after sunset Venus will be seen in the west with the waxing crescent Moon just above the star Aldebaran which lies between us and the Hyades cluster in Taurus. April 11th to 13th: 45 minutes after sunset - Venus close to the Pleiades Cluster: After sunset and as darkness falls, Venus will be seen just to the left of the Pleaides Cluster in Taurus. 8 6th 19:28 22nd 22:42 8th 21:06 25th 20:12 10th 22:45 27th 21:51 13th 20:15 30th 19:21 15th 21:54 9

6 The Planets The Sky This Month Saturn Saturn now rises in the evening, earlier each night so that by month's end it rises about 22:22 BST. Shining at magnitude +0.3 and brightening to +0.1 during the month it lies in Scorpius very close to the left hand star of the 'fan' that marks its head. Its diameter increases from 17.8 to 18.4 arc seconds as April progresses. It will be due south in the early hours of the morning at an elevation of ~22 degrees. The beautiful ring system has now opened out to ~25 degrees - virtually as open as they ever become. Its elevation never gets above ~22 degrees and so the atmosphere will hinder our view of this most beautiful planet. Saturn imaged by the Hubble Space Telescope in October 1998 Uranus Uranus reaches solar conjunction on April 6th and is therefore unsuitably placed for observation throughout April. Neptune Neptune, mag. +8.0, reached solar conjunction at the end of February but remains unsuitably placed for observation from northern temperate latitudes during April. The outermost planet of all is currently located in the faint constellation of Aquarius. On April 14th, large asteroid Vesta passes 2.7 degrees south of Neptune. Planetary info source: & 10 This map shows the constellations seen in the south in mid-evening. The constellation Gemini is now setting towards the south-west and Leo holds pride of place in the south with its bright star Regulus. Between Gemini and Leo lies Cancer. It is well worth observing with binoculars to see the Beehive Cluster at its heart. Below Gemini is the tiny constellation of Canis Minor whose only bright star is Procyon. Rising in the south-east is the constellation Virgo whose brightest star is Spica. Though Virgo has few bright stars it is in the direction of a great cluster of galaxies - the Virgo Cluster - which lies at the centre of the supercluster of which our local group of galaxies is an outlying member. The constellation Ursa Major is high in the northern sky during the evening this month and contains many interesting objects. 11 Sky This Month :

7 The Sky This Month The Sky This Month Gemini Gemini - The Twins - lies up and to the left of Orion and is in the south-west during early evenings this month. It contains two bright stars Castor and Pollux of 1.9 and 1.1 magnitudes respectivly. Castor is a close double having a separation of ~ 3.6 arc seconds making it a fine test of the quality of a small telescope - providing the atmospheric seeing is good! In fact the Castor system has 6 stars - each of the two seen in the telescope is a double star, and there is a third, 9th magnitude, companion star 73 arc-seconds away which is also a double star! Pollux is a red giant star of spectral class K0. M35 is an open star cluster comprising several hundred stars around a hundred of which are brighter than magnitude 13 and so will be seen under dark skies with a relatively small telescope. It is easily spotted with binoculars close to the "foot" of the upper right twin. A small telescope at low power using a wide field eyepiece will show it at its best. Those using larger telescopes - say 8 to 10 inches - will spot a smaller compact cluster NGC 2158 close by. NGC 2158 is four times more distant that M35 and ten times older, so the hotter blue stars will have reached the end of their lives leaving only the longer-lived yellow stars like our Sun to dominate its light. To the lower right of the constellation lies the Planetary Nebula NGC2392. As the Hubble Space Telescope image shows, it resembles a head surrounded by the fur collar of a parka hood - hence its other name The Eskimo Nebula. The white dwarf remnant is seen at the centre of the "head". The Nebula was discovered by William Herschel in It lies about 5000 light years away from us

8 Observing Notes 1 April 23:00 15 April 22:00 30 April 21:

9 The Sky This Month The Sky This Month Leo The constellation Leo is now in the south-eastern sky in the evening. One of the few constellations that genuinely resembles its name, it looks likes one of the Lions in Trafalgar Square, with its main and head forming an arc (called the Sickle) to the upper right, with Regulus in the position of its right knee. Regulus is a blue-white star, five times bigger than the sun at a distance of 90 light years. It shines at magnitude 1.4. Algieba, which forms the base of the neck, is the second brightest star in Leo at magnitude 1.9. With a telescope it resolves into one of the most magnificent double stars in the sky - a pair of golden yellow stars! They orbit their common centre of gravity every 600 years. This lovely pair of orange giants are 170 light years away. Leo also hosts two pairs of Messier galaxies which lie beneath its belly. The first pair lie about 9 degrees to the west of Regulus and comprise M95 (to the east) and M96. They are almost exactly at the same declination as Regulus so, using an equatorial mount, centre on Regulus, lock the declination axis and sweep towards the west 9 degrees. They are both close to 9th magnitude and may bee seen together with a telescope at low power or individually at higher powers. M65 is a type Sa spiral lying at a distance of 35 million light years and M66, considerably bigger than M65, is of type Sb. Type Sa spirals have large nuclei and very tightly wound spiral arms whilst as one moves through type Sb to Sc, the nucleus becomes smaller and the arms more open. The second pair of galaxies, M95 and M96, lie a further 7 degrees to the west between the stars Upsilon and Iota Leonis. M95 is a barred spiral of type Sb. It lies at a distance of 38 million light years and is magnitude 9.7. M96, a type Sa galaxy, is slightly further away at 41 million light years, but a little brighter with a magnitude of 9.2. Both are members of the Leo I group of galaxies and are visible together with a telescope at low power

10 The Sky Looking Overhead at Midnight mid-april 2015 The Sky Looking North at Midnight mid-april

11 The Sky Looking East at Midnight mid-april 2015 The Sky Looking West at Midnight mid-april

12 The Sky Looking South at Midnight mid-april 2015 Messier of the Month M97 Messier 97 (Owl Nebula) Planetary Nebula M97 (NGC 3587), type 3a, in Ursa Major Dicovered by Pierre Méchain in The Owl Nebula Messier 97 (M97, NGC 3587) is one of the fainter objects in Messier's catalog. It is one of the four planetary nebulae in that catalog, and situated in constellation Ursa Major. Admiral William H. Smyth first classified it as planetary nebulae in William Huggins recognized its nature as a gaseous nebula from the observation of its spectrum, where he discovered two spectral lines. As often for planetary nebulae, the Owl is significantly brighter visually (than photographically, as most light is emitted in one green spectral line. Its distance is uncertain; the Sky Catalog 2000 has 1,300 light years (400 pc). M97 is one of the more complex planetary nebulae. Its appearance has been interpreted as that of a cylindrical torus shell (or globe without poles), viewed oblique, so that the projected matter-poor ends of the cylinder correspond to the owl's eyes. This shell is enveloped by a fainter nebula of lower ionization. The mass of the nebula has been estimated to amount 0.15 solar masses, while the 16 mag central star is believed to be of about 0.7 solar masses. RA Dec Brightness Dimension 11 : 14.8 (h:m) +55 : 01 (deg:m) 9.9 (mag) 3.4x3.3 (arc

13 Double Star of the Month Algieba One of the finest double stars in the spring sky indeed, in all the heavens is gamma Leonis. Its proper name, Algieba, comes from the Arabic Al Jabbah (The Lion s Mane). Discovered by William Herschel in 1782, Algieba is comprised of magnitude 2.4 and 3.6 stars currently separated by 4.6 arc-seconds. They form a slowly widening binary system with an orbital period estimated at between 5 and 6 centuries. Algieba is easily located - it s the brightest star (after Regulus) in the Sickle of Leo. The pair is marginally resolved in small-aperture telescopes with medium power. On an evening of steady seeing, Algieba may be split with a 3- inch reflector at 60X. A clean split, however, requires a magnification of 100X or more. Comet Lovejoy C/2014 Q2 Comet Lovejoy continues on its northern path during April as heads towards Polaris and the North Celestial Pole. At peak it was far brighter that originally expected and bright enough to be seen with the naked eye. The good news is that although Lovejoy has now faded and not as impressive as previous, it remains within the range of binoculars and small scopes. Lovejoy spends all of April in Cassiopeia. At the start of the month it's positioned just north of the famous "W" asterism of the constellations brightest stars. It then continues to move northwards through the barren patch of sky towards Cepheus. During this time, there are many nearby fainter stars that can be easily seen in binoculars for star hopping purposes. Lovejoy is expected to fade from +6.5 to +8.2 during April. What makes Algieba so visually striking are its rich golden-yellow hues, indicative of its K0 and G7 spectra. Some observers note a slight greenish tinge to the companion

14 Lyrid Meteor Shower (16 26 April) The 2015 annual Lyrids meteor shower peaks on April 22nd and this year's event promises to be a good one as the four-day-old waxing crescent Moon (21% illuminated) will not interfere. The Lyrids are not one of the strongest annual displays and the peak period is short but up to 20 meteors per hours can be seen. The Lyrids radiant is located inside Hercules very near to the border with Lyra and only 6 degrees from the fifth brightest star in the sky, Vega. Unlike sporadic meteors that originate from anywhere in the sky, periodic shower meteors can always be traced back to the same region the radiant point of the meteor shower. It s best to scan a large area surrounding the radiant without directly looking at it. The shower activity lasts from April 16th to April 26th with the best time to observe around midnight on the evening of April 22nd / 23rd. BAS Open Observing Saturday Observing at the Failand Observatory Members open the Society's Observatory at Failand for the General Public on many clear Saturday Nights. We welcome visitors including family, friends, neighbours with or without telescopes and binoculars etc. No astronomical knowledge or skill is required except interest in what you may be about to observe! For further information on how to attend, including details and information on where to find us please saturday.observing@bristolastrosoc.org.uk. Use the status message on to check if the session is running. Date BAS Members 4 Apr No public observing 11 Apr Stephen Price Jane Clark Nigel Kirkland 18 Apr No public observing 25 Apr John Willis Nigel Kirkland Simon Perks 26 Observing at Tyntesfield & Other Events The Bristol Astronomical Society provides equipment and expertise for Star Parties and Solar Observing run by The National Trust, Tyntesfield. These take place (weather permitting) regularly during the year. Bristol Astronomical Society also regularly organises other star gazing events around the City. Check for more details and how to attend. 27

15 Society News Programme of Events (At Bristol Grammar School, University Road BS8 1SR) 10th Apr Andrew Wilson My first steps into astro-spectroscopy 17th Apr Spring Social Bring & buy sale, small buffet & astro. chit-chat 24th Apr David Woods Portable Imaging Systems 1st May Andrew Lound A Mars Odyssey BAS Committee Members in 2015 Chairman Deputy Chairman Treasurer Secretary Observations Director Observatory Director Speaker Secretary Tyntesfield Observing Director Committee Member Committee Member Committee Member Richard Mansfield Pete Quinn Simon Perks Sari Vanska Dr Jane Clark Dr Stephen Price Fiona Lambert Dr Alan McCarthy Dr John Bishop Dr Andrew Mclean Trevor Taylor Bristol Astronomical Society Registered Charity No