The 14th annual guide to astronomical phenomena visible from Ireland during the year ahead (naked-eye, binocular and beyond) By Liam Smyth and John O’Neill € 5 Published by the Irish Astronomical Society, P.O. Box 2547, Dublin 14. e-mail: [email protected] www.irishastrosoc.org Page 1 Foreword Contents 3 Your Night Sky Primer We send greetings to all fellow astronomers and welcome them to this, the fourteenth edition of 5 Sky Diary 2006 Sky-High. 9 The Planets in 2006 This year, while retaining the colour covers, we have increased the number of pages. 10 Variable Stars in 2006 11 The Strange “Days” of Venus and Mercury We thank the contributors of the accredited ar- ticles. Thanks are also due to John Flannery who 13 Eclipses in 2006 did the DTP layout. The Binary orbit diagrams are from BINARY.EXE from J.O’Neill, likewise the sun- 14 Comets in 2006 rise and sunset data is from his SUNRISE.EXE. 15 Meteors Showers in 2006 We are always glad to hear what you liked, or 17 A Minor Challenge – Observing Asteroids what you would like to have included in Sky-High. 20 More about Binaries and Multiple Stars If we have slipped up on any matter of fact, let us know. We can put a correction in future issues. 22 The Year in Space And if you have any problem with understanding the contents or would like more information on 24 Gallery any topic, feel free to contact us at the Society e- mail address [email protected]. This years marks the 1000th anniversary of the brightest supernova in recorded history, the Lupus Up-to-date news of IAS activities and links to Supernova of 1006 which reached magnitude –9! sites of interest on the Internet can be found on our own website at www.irishastrosoc.org. Lets hope this is a good omen for our next su- pernova. Also on the Society website Sky-High Online will highlight some celestial events featured in Sky- Wishing you clear skies for 2006, High, also featured will be unpredictable events Liam Smyth and John O'Neill such as bright comets and bright supernovae. Sky-High 2006 © IAS, 2005 The Irish Astronomical Society Founded in 1937, the Irish Astronomical Society caters for those of all ages and interests in astron- catching the wonders of the night sky from home. omy and space. The Society also has a well stocked library of You don’t have to be an expert to be part of books and journals that members can borrow as our dynamic club. Many of our members are taking well as access to a number of telescopes that can their first steps in the hobby and you are sure to be loaned for a period. receive friendly advice from some of the more ex- perienced amateur astronomers in our group. A number of IAS members have made their own telescope while others possess telescopes ranging Activities include monthly meetings, receiving in size up to a 50cm behemoth! Many are now ex- our bi-monthly magazine Orbit, observing groups, perimenting too with the latest technologies to hit e-mail alert notices of transient astronomical phe- the amateur community such as CCD cameras. nomena such as aurora, and outings to places of astronomical interest. If you are considering purchasing a telescope Members have joined expeditions to observe then we’ll point you in the right direction before several total solar eclipses world wide as well as you take the plunge and part with your hard- Forthcoming meetings of the Irish Astronomical Society: Monday Oct 17th 2005 The Moon: A Brief History by Brian Keane (I.A.S., President) Monday Nov 21st 2005 Einstein’s Astronomical Legacy by Prof. Tom Ray (D.I.A.S.) Monday Dec 19th 2005 Ringworld. Details of the Cassini Mission by Deirdre Kelleghan (I.A.S.) All held in Ely House, 8 Ely Place, Dublin 2. They start at 8pm. All are welcome. Page 2 Your Night Sky Primer As with any hobby, astronomy seems to have it's tive appearance mislead you; it's packed with in- own set of terminology designed to confuse. How- formation and the core of the book features a set ever, with a little patience you'll soon pick up the of constellation charts with many interesting celes- jargon and be well on the way to knowing your way tial objects labelled. around the sky. For more detailed studies, especially with bin- The revolving heavens oculars or a small telescope you will need a more We all know the Heavens don't revolve, it is the detailed map showing all stars to at least sixth other way round, the Earth rotates on its axis. But magnitude. A recent entry is Atlas of the Night Sky it looks otherwise and it is easier to describe things published by Collins for about €30. This shows stars as we see them for our immediate purpose. The to magnitude 7.5 and the positions of many Deep fact that the Earth turns on its axis about every 24 Sky Objects. hours causes the Sun to rise in the east and set in the west, and it is due south at noon. A similar An idea of size or scale situation applies to all the other heavenly bodies If you have seen a picture of a total eclipse of except that since they appear to move relative to the Sun you will have noticed that the black disk of the Sun they are not south every day at noon. the Moon just about covers the bright disk of The Sun. If you were to suspend a one Euro coin about The stars appear to drift west in such a way two and a half metres in front of your eye, it that any particular star is due south four minutes would just about cover the Moon's disk. earlier each day or night. If you multiply four min- utes by 365 you get something close to 24 hours. The Sun is nearly 1.4 million km in diameter, So if a star is south at eight o'clock tonight, it will the be south four minutes earlier tomorrow, and two Moon is 3476 km and the one Euro coin is just over hours earlier in a month. In six months it will be two centimetres in size. Yet they appear nearly south at about eight in the morning. In a year it equal. This is because they all seem to take up the will again be south at eight in the evening. It fol- same amount of the space in front of our eyes. We lows that we see different constellations in differ- may say they have the same angular diameter. In ent seasons, but over a year, we see all that por- this case it is about half a degree (½°). tion of the heavens that can be seen from Ireland. Degrees are further divided into 60 arcminutes Star maps (60') with each arcminute made up of 60 arc- You will need at least one star map. This could seconds (60"). The scale allows us to measure an- be a set of monthly charts such as are included in gles in the sky or apparent size of a celestial ob- many books on astronomy. Phillips' Planisphere is ject. For example, the Full Moon measures an aver- very useful. It comes in various sizes at equivalent age of half a degree, or 30 arcminutes, in diame- cost. It allows you to show the constellations visi- ter. ble at any time of the night, any time in the year. Your closed fist held at arms length is about ten You could get away with using the monthly degrees (10°). Your stretched out hand, i.e. from charts published in newspapers but there are a the tip of your thumb to the tip of your little fin- couple of drawbacks. Each chart is correct for only ger, is about twenty degrees. Between four and one time on a given night, say 10 p.m. If you are observing two hours later you would need the fol- lowing month's chart. These charts also show the A “handy” way to planets visible for a particular month, so they can measure scale in the sky. The tip of your little fin- be confusing unless you tippex them out. When ger at arm’s length cov- learning the constellations check first from the ers ½°; i.e. the apparent monthly notes if there is a bright planet in the width of the Full Moon. A area. good demonstration of the illusion that the Moon Once you can find the constellations you will looks big is that it would enjoy learning more about them. take ten Full Moon’s side- by-side to span the gap A delightful pocket-sized book is Stars - part of between the two the Collins Gem series that is available for about “pointer” stars in the seven Euro in any bookstore. Don't let its diminu- Plough — a distance of Page 3 five outstretched hands or twice as many closed pass through superior conjunction. fists will take you from the horizon to zenith. If you When outer planets are in opposition they are know the Plough you will find that its overall opposite the Sun to us and are on the celestial me- length is rather more than one outstretched hand, ridian (the southern part) at midnight. it is almost 25 degrees. The celestial meridian is an imaginary line that Some familiarity with angular measure is neces- starts at the north point of the horizon, rises di- sary to find your way easily about the sky.