DECEMBER SKY CHARTS. E V E N I N G SKY M ID DECEMB E R at 21 h 0 0 ( SOUTH DOWN)

Transcription

1 DECEMBER SKY CHARTS E V E N I N G SKY M ID DECEMB E R at 21 h 0 0 ( NO RTH DOWN) E V E N I N G SKY M ID DECEMB E R at 21 h 0 0 ( SOUTH DOWN) 1

2 PLEASE NOTE: All events predicted below are as observed from Hermanus, Western Cape, South Africa 2. THE SOLAR SYSTEM PLANET VISIBILITY Mercury Venus Mars Jupiter Saturn Uranus Neptune Pluto Low in the west after sunset Low in the east before sunrise, latterly moving too close to the Sun Visible in the morning Visible in the morning Low in the west after sunset then moving too close to the Sun Visible in the evening Visible in the evening Visible in the evening then moving too close to the Sun Sun & Planets DECEMBER st 31 st Sun Length of day Mercury phase Venus phase Mars phase Jupiter Saturn Uranus Neptune Pluto Ophiuchus to Sagittarius 14h 16m to 14h 24m φ 8 to 7 37% to 61% Sagittarius to Ophiuchus +0.2 to -0.3 φ 10 99% to 100% Libra to Sagittarius -3.9 φ 4 to 5 95% to 93% Virgo to Libra +1.7 to +1.5 Φ 31 to 33 Libra -1.7 to -1.8 φ 15 Sagittarius +0.5 φ 4 Pisces +5.7 to +5.8 φ 2 Aquarius +7.9 Sagittarius Rises: 05h25 05h34 Transits: 12h32 12h46 Sets: 19h40 19h58 Rises: 06h40 04h07 Transits: 13h57 11h09 Sets: 21h13 18h12 Rises: 04h55 05h24 Transits: 11h54 12h37 Sets: 18h53 19h50 Rises: 03h10 02h05 Transits: 09h36 08h50 Sets: 16h02 15h35 Rises: 03h56 02h16 Transits: 10h38 09h02 Sets: 17h19 15h49 Rises: 06h44 05h01 Transits: 13h52 12h09 Sets: 20h59 19h16 Rises: 15h57 13h57 Transits: 21h33 19h34 Sets: 03h14 01h15 Rises: 12h29 10h33 Transits: 18h53 16h57 Sets: 01h21 23h20 Rises: 08h13 06h19 Transits: 15h18 13h24 Sets: 22h23 20h29 Notes to the table above on the next page... 2

3 Phase: In a telescope, the inner planets (Mercury, Venus and Mars) appear to us in phases, depending on the angle of the Sun s illumination, as does the Moon. The angular diameter (φ) is given in arc seconds ( ). This is the apparent size of the object as we see it from Earth. To illustrate this point, consider the average binoculars through which we see about 7º of sky. Therefore, for example, Mars at 19 on 1 st May would cover approximately 1/1300 th of the field of view. : we are accustomed to hearing stars described in terms of magnitude, for example Antares (in Scorpius) at and the planet Jupiter, at magnitude The latter is considerably brighter than Antares as the scale is inverse ; the brighter the object, the lower the number. A good human eye on a clear night can see down to a magnitude of about +6. Transit: When an object crosses the local meridian it is said to transit. The local meridian is an imaginary line from the horizon directly north passing overhead to the horizon directly south. THE MOON Lunar Highlight (information from the 2017 Sky Guide Africa South): GASSENDI Type: Crater with a double peaked central mountain and a system of hills rising from its central floor. Diameter: 114 km Notes: Named for Pierre Gassendi, 17th century astronomer. The rilles in this crater can be seen in modest-sized telescopes. Location: Northern edge of Mare Humorum. Best seen: three days after first Quarter and two days after last Quarter Age: about 3.9 billion years. Eclipses (visible from Southern Africa): No eclipses, solar or lunar, are predicted for this month. METEOR SHOWERS Name December Phoenicids Date & Time of Max 6 December 20h30 to 02h00 Duration Radiant ZHR velocity 3 to 9 December 7º NW of Achernar (α Eri) Observing Prospect 5 22 Unfavourable Geminids 14 December 23h30 to 03h00 4 to 16 December About 3º WNW of Castor (α Gem) Good Puppid-Velids 29 December 22h30 to 03h30 5 December to 7 January About 23º east of Acrux (α Cru) 5 40 Good Guide to the table above: ZHR zenithal hourly rate vel. - velocity in km per second For more details regarding meteor watching, please see the Sky Guide Africa South (SGAS), pages

4 3. HIGHLIGHTS FROM THE SKY GUIDE Date Time Item 1 Comet 14P/Wolf at perihelion (2.74 AU, 8.8 years) 3 17h47 Full moon Mercury stationary 4 Moon at perigee ( km) 5 Moon furthest north (+20.0º) 7 Moon near the Beehive Cluster (M44) 9 00h19 Moon near Regulus (1º 27 ) 10 09h51 Last quarter Moon Comet 139P/Väisälä-Oterma at perihelion (3.41 AU, 9.6 years) 12 Mercury at perihelion 13 Moon near Mars Mercury in inferior conjunction 14 Moon near 7.3 magnitude Vesta (24.6 ) Moon near Jupiter Geminid meteor shower peaks (see METEOR SHOWERS above) 15 Venus near Mercury 17 Moon near Venus and Mercury 18 08h30 New Moon Moon near Saturn Comet P/2010 D1 (WISE) at perihelion (2.69 AU, 8.5 years) Moon furthest south (-20.1º) and at apogee ( km) 21 18h28 Summer solstice Saturn in conjunction with Sun Ceres stationary Comet P/2009 S2 (McNaught) at perihelion (2.21 AU, 8.5 years) 22 Mercury greatest latitude north 23 Mercury stationary 24 Moon near Neptune Pallas stationary 25 Venus and Saturn in conjunction (68 apart) [and 3.4º from the Sun!] 26 11h20 First quarter Moon 27 23h40 Moon near Uranus (3.5º apart) 29 Jupiter multiple transit: Europa and Ganymede, Europa shadow transit Puppid meteor show peaks (see METEOR SHOWERS above) 30 20h53 Moon occults magnitude Hyadum II (δ1 Tauri) 31 03h41 Moon 1.5º north of magnitude Aldebaran (α Tauri) 4. STARGAZING SUGGESTED OBSERVATION DAYS FOR DECEMBER: Unless specifically targeting the moon, I suggest the most convenient dates to plan evening stargazing in December are 7th (moonrise 23h21) to 20 th (moonset 21h24). The next club stargazing evening is planned for January More information regarding venue, etc., will be posted in due course to members addresses and on our website 4

5 DEEP SKY HIGHLIGHT (from the Sky Guide Africa South) 47 Tuc (NGC 104) (magnitude 4.00) (See page 1. South down chart just west of the Small Magellanic Cloud) From the 2017 Sky Guide 47 Tuc is possibly the most impressive of all globular clusters. Binoculars show a perfectly round, small knot of stars surrounded by a soft halo at least 15 across. A telescope shows the nucleus as a brilliant button of unresolved starlight surrounded by a dazzling halo at least half a degree across, richly peppered with stars. American astronomer Brian Skiff describes the outer region as containing wedges of ill-defined blank areas and arms of stars. NGC 104 is one of the most massive of globular clusters containing some solar masses. It lies about light years distant. From Ian Ridpath s Star Tales : Genitive: Tucanae Abbreviation: Tuc Size ranking: 48th Origin: The 12 southern constellations of Keyser and de Houtman One of the 12 southern constellations devised by the Dutch navigators Pieter Dirkszoon Keyser and Frederick de Houtman at the end of the 16th century. It represents the South American bird with a huge bill. The Dutchman Petrus Plancius gave it the name Toucan when he first depicted it on a globe in 1598, and Johann Bayer followed suit on his atlas of But de Houtman, in his catalogue of 1603, called it Den Indiaenschen Exster, op Indies Lang ghenaemt ( the Indian magpie, named Lang in the Indies, the word lang referring to the bird s long beak). De Houtman was apparently describing not a toucan but the hornbill, a similarly endowed bird that is native to the East Indies and Malaysia. This suggests that the original inventor of Tucana was in fact Keyser, who had visited South America before his voyage to the East Indies and could have seen the bird there. In some depictions which used de Houtman s catalogue as a source, such as Willem Janszoon Blaeu s globe of 1603, the bird was shown as a hornbill rather than a toucan, complete with casque above its bill, but the original identification as a toucan won out. Tucana s brightest star, Alpha Tucanae, marking the tip of the bird s beak, is of only third magnitude, but the constellation is distinguished by two features of particular interest: firstly, the globular star cluster 47 Tucanae, rated the second-best such object in the entire sky, so bright that it was labelled in the same way as a star; and the Small Magellanic Cloud, the smaller and fainter of the two companion galaxies of our Milky Way. These features were originally part of Hydrus but were transferred to Tucana when the French astronomer Nicolas Louis de Lacaille reorganized this part of the southern heavens in the 1750s. Incidentally, 47 Tucanae is not a Flamsteed number; it comes from its listing in Johann Bode s catalogue called Allgemeine Beschreibung und Nachweisung der Gestirne, published in 1801 to accompany his Uranographia star atlas. It was first recorded as a star by Keyser and de Houtman. Bayer showed it on his southern star chart of 1603 within one of the coils of Hydrus, beneath the claw of the toucan, but its nebulous nature was first noted by Lacaille a century and a half later. None of the stars of Tucana is named, and there are no legends associated with it. Ian Ridpath. All rights reserved 5

6 Please keep in touch... Don t forget to have a look at our excellent website, edited by Derek Duckitt. Also... ASSA website ASSA Deep-Sky Section Whatsapp chat group: [ ] Official Big 5 of the African Sky web page Official Big 5 Facebook group ASSA Deep-Sky Section mailing list Contact ASSA Get in touch with officers of the Society - we're real people with a passion for astronomy, so contact us and let's talk! You can find us on Facebook, Twitter, the ASSA_Info mailing list and the ASSA_Discussion mailing list. Grateful thanks to the following, without whom this publication just would not be the same: ASSA Sky Guide Africa South 2017 Stellarium Ian Ridpath Compiled by Peter Harvey petermh@hermanus.co.za Tel: