Phobos
/Volume 33
/Number 7
/October 2006
Contents1) Meetings.
2) Society News.
3) Guest Speaker.
4) Sky Diary.
7) Autumn Variables..
9) Keeping Abreast.
16) Solar Eclipse. / Ken Willoughby
Ken Willoughby.
Professor David W. Allen.
Derek Hufton.
Melvyn Taylor.
Clive Down.
Melvyn Taylor.
Meetings
October Meetings3rd.
5th. (Thurs.)
10th.
16th. (Mon.)
17th.
24th.
31st. / Members Night.
Committee meeting.
'The Chemistry of Interstellar Dust.'
Professor David W. Allen.
Visit: 7:00pm-9:00pm.
Castleford Ranger Guides.
The Open University SXR208 Astronomy Course.
Kevin read.
The November Sky.
Ken Willoughby.
Open Night. 7:30pm-10:00pm.
SOCIETY NEWS. KEN WILLOUGHBY.
September has been an eventful month with speakers. Firstly Sir Arnold Wolfendale came and talked about 'The Search for Intelligent Life' and secondly Professor Mark Bailey from Armagh (both at short notice.) Arnold suggested we contacted Patrick with a view to holding an annual 'Patrick Moore Lecture' where we would invite top speakers from all over the World. Patrick was 'over the Moon' at this and the first of these was on September 26th by Mark Bailey entitled 'New Results and Problems of Cometary Origin.' People are already being contacted for next year so watch this space..
LEEDS ASTROMEET 2006.
Date: Saturday, 11th November 2006, Doors open 9.00 am.
First speaker 10.00 am. Last speaker 5.10 pm.
Tickets on door: £10.00
Venue: The Clothworkers Centenary Concert Hall and Foyer, School of Music,
Leeds University (a 300 seat auditorium)
(see venue at http://webprod2.leeds.ac.uk/campusmap/detail.asp?ID=13)
(or a map at http://www.universallyleeds.co.uk//maps/campusmap.pdf)
Speakers: Tom Boles (BAA)
"Type I Supernovae - the new stars of Cosmology"
Professor John Brown (Astronomer Royal for Scotland)
"The Uncertain Universe - Magic of the Cosmos"
Dr Allan Chapman (Oxford University)
"Mary Somerville and the Lady Astronomer"
Dr Simon Green (Open University)
"Stardust - a new view of Comets"
Nik Szymanek (BAA)
"Photographing the Night Sky"
Trade stalls already confirmed include:
Earth and Sky Books, Aurora Books, Chris Marriott's Skymap, Cape Instruments
Green Witch Telescopes, Opticstar Ltd, British Astronomical Association
Stockport Binocular and Telescope Centre, Astronomica
Further details can be found on the the Leeds Astronomical Society website: http://www.leedsastronomy.org.uk
TUESDAY OCTOBER 12TH.
'WE LIVE IN A DUSTY.UNIVERSE!'
PROFESSOR DAVID W. ALLEN.
Following a PhD degree at Keele, and a research fellowship at Cambridge, David came to live in Dronfield in 1969, when he started work as a lecturer in Chemistry at the then Sheffield College of Technology, which shortly afterwards became Sheffield Polytechnic, one of the first of the new ‘Polytechnic’ institutions and which eventually became Sheffield Hallam University in the early 90’s.
He retired as Professor and Head of Chemistry in 2002, but is still active in the University as an Emeritus Professor, helping out with the work of a research group and writing and editing books and other publications. He now has the time to pursue interests in chemical aspects of astronomy and a bit of scientific journalism.
Sky Diary: October 2006. Derek Hufton.
Monthly Highlights:
October is a very quiet month for planet watchers. Jupiter is quite low in the west-southwest at dusk, and Mercury puts in an appearance there even lower, requiring binoculars to find. The only planet easily visible is Saturn, which is high in the southeast before dawn. The reliable Orionids meteor shower peaks this month and is favourably placed due to a New Moon at maximum activity.
Dates & Time:
Sunday 1st October is the 274th day of the year and it is also number 2454009 in the Julian Calendar.
The Sun:
Rotation number 2049 of Carrington’s series begin on October 18.55 respectively. During the month the Sun’s axis of rotation is tilted to the east of the vertical some 26.0o at the start of the month and by month end it will be 24.5o to the east. The Sun’s disk is also tilted away from us by 6.4o at the start of the month ending the month tilting away from us by 4.4o – crucial data for you sunspot plotters!
The Moon:
In the Farmers Almanac, the October Full Moon is called the Hunter’s Moon. In other places it is also referred to as the Blood Moon. However, as the definition of the Harvest Moon is the full Moon closest to the September Equinox, the title this year goes to the October Full Moon, occurring 14 days after the equinox – confusing or what? The waning crescent Moon appears a few degrees to the upper left of Saturn at dawn on the 16th. Back in the evening sky, on the 24th the thin waxing crescent lies very low in the southwest, well to the left of Mercury and Jupiter. The next night it is a little higher and farther left of the two planets – but only 4o left of 1st-magnitude Antares.
The Moon's Phases are: New 22d 05h 14m 1st Qtr 29d 21h 25m Full 07d 03h 13m Last Qtr 14d 00h 26m
The Moon is at Perigee (closest approach to the Earth) on October 6th at 14h when its apparent diameter will be 33’ 26”. Apogee (furthest approach) occurs on October 19th at 10h with apparent diameter of 29' 26".
The maximum Libration points of the Moon’s ‘wobble’ occur on October 12th and 27th, the main extra tilt being visible at Position Angles 229o and 42o respectively. This means that you get a chance to ‘peep round the edge’ of the lunar limb even more on these dates. Remember that Position Angle is measured from North through East on the face of the Moon (North=0o, East=90o, South=180o, West=270o) and it tells you where to concentrate your telescope.
Mercury:
Reaches its greatest elongation of 25o from the Sun on the 16th, shining at magnitude –0.1. This elongation will be happening very low in the sky at twilight. On the 17th, about 30 minutes after sunset, you’ll find Mercury just 4o below Jupiter. The two planets are in conjunction in Right Ascension on the 25th and 28th, with Mercury lower left of Jupiter on both dates. Their very low altitude will make them difficult to spot..
Venus:
Is in conjunction with the Sun on the 27th. Early in the month you might still catch Venus barely above the eastern horizon before sunrise; then it’s gone.
Mars:
Is in conjunction with the Sun on the 23rd and is therefore not visible this month.
Jupiter:
Is still easily visible as the month commences, shining at magnitude –1.8. It is located low in the west-southwest in early twilight. By the end of the month it will be so low that you’ll probably need binoculars to locate it.
Saturn:
Rises in the northeast at around 3am, shining at magnitude +0.5, at the start of the month. By the end of the month the planet rises just after midnight. The best time for observing will be just before dawn, when Saturn is high in the sky and is much more likely to show a steady and sharp image. The rings are now tilted by only 13o.
Uranus and Neptune:
Are both well up by mid-evening, in the southeast and south respectively. Uranus will be shining at magnitude +5.8 with Neptune somewhat dimmer at +7.9. Check out the Sky & Telescope website (http://skytonight.com/observing/objects/planets/3311356.html) or the BAA Handbook for finder charts.
Meteor Showers:
The major shower active this month are the Piscids, Orionids and Taurids. The Piscids is another multiple-radiant ecliptic complex with low rates. The Orionids, associated with Comet Halley, usually has fast meteors with a high proportion of persistent trains. The shower has a flat maximum with several sub peaks and is favourable this year. By contrast the Taurids has slow meteors, often bright, but not the rich fireball source suggested in some books. It starts activity this month, although doesn’t peak until early November. Full details as follows:
ß RADIANT à Moon
Shower Limits Maximum ZHR RA Dec at Maxm.
Piscids Sep-Oct Oct 13 ? 01h 44m +14o 21 days
Orionids Oct 16-27 Oct 20 25 06h 24m +15o 28 days
Taurids Oct 20-Nov 30 Nov 3 10 03h 44m +14o 13 days 03h 44m +22o
Looking South from the observatory @ 22:00h on October 15th.
A Selection of Autumnal Variables. Melvyn Taylor.
Stars from magnitude 2 to 10.
Eta Aquilae:
Discovered by Edward Pigott (York) in 1874 this easily found Cepheid variable lies under Altair and changes from mag. 3.5 to 4.4 every 7.17days. Comparison stars beta Aql mag. 3.21 and iota Aql at mag. 4.36 are very useful. This young, large star changes its temperature and surface area with regularity.
RZ Cassiopeiae:
An eclipsing binary in a binocular field of iota Cas varying from mag. 6.2 to 7.7 in the orbital period of the system, 1.195 days. The total duration of an eclipse is 4.8h. The star is predicted to be faint at one of its primary minima on Oct 02d at 20.8h (UT). Over long intervals the period of the system changes by about 15 minutes.
Mira (omicron Ceti):
This infamous variable probably first recorded to be changing by Fabricius in 1596 lies 420 light years away. During October the star is nearing a minimum about mag. 9 to 10. Its extreme mag. range is 2.0 to 10.1 in a period of 329 days. This is a huge star having its disc imaged at 0.048 arc seconds, corresponding to a diameter of around 6 astronomical units (450 million kilometres). Not far from delta Ceti.
AF Cygni:
The star is a typical semi-regular giant star which has been catalogued varying from mag. 6.4 to 8.4 with a mean period of 94d. Interest in these type stars is that the period is often poorly expressed and it may vary slowly, become irregular or may show at a constant brightness. It is probably best found by its location near delta Cyg.
RY Draconis:
A typical semi-regular variable star that is circumpolar and relatively easy to find being in a triangle of bright stars labelled 7 , 8 and 9 Draconis. The overall changes are from mag. 6 to 8 with a dubious period of 172 days. All that is required is a small binocular and clear skies!
AG Draconis:
A star in outburst at present and around magnitude 8.5 or thereabouts; at its quiet times visual mag. 10.0. It is an unusual eruptive binary object (known as a symbiotic) with a recent active phase when it was in outburst for 5 years from 1981. Being circumpolar from the UK at declination 67* the star is in a relatively bland area between the brighter stars of the Little Bear and the curving Dragon.
UW Herculis:
Easily found near pi and rho Her (the left/east shoulder of the Giant) using a binocular this semi-regular variable has recently livened and is showing its period of about 100d with a brightness factor change of about 2.3 (mag. 7.8 - 8.7).
alpha Herculis (Rasalgethi):
One of the largest stars known but W.Herschel did not know that when he discovered its variability in 1795. It is a semi-regular, reddish, looking naked-eye star that shows slow brightness changes. There are 3 stars that show the combined light some 380 light years away. It is about mag. 3.3 at present.
Sheliak (beta Lyrae):
One of the most observed and researched stars in the sky. John Goodricke discovered the changes from York (1784) and his explanation was that one star was being eclipsed by another in co-orbit. With the naked-eye the changes are from mag. 3.3 to 4.3, the star having deeper fades every 12.94d. In between there is a lesser dip to mag. 3.8. Sheliak has a luminosity 2600 times that of our Sun, it is 900 light years away. Gamma Lyr is mag.3.23 and kappa Lyr 4.34 - convenient comparisons.
X Ophiuchi:
Dscovered by the Rev'd T. Espin in 1886 this long period variable (6.6 to 8.8, period 329d) is similar in nature to Mira and frankly not easy to find. But once found its location is easily remembered since it is adjacent a small triangle of bright stars with a mag. 5.4 star to its west in the same small field of view.
GO Pegasi:
A few degrees from alpha Pegasi (Markab) this "red" looking star changes from about mag. 7 to 8. The star is in a class of evolved giant stars with no charted periodicity in its light variations.
Algol (beta Persei):
Ane of the most famous stars stars in the sky with an intriguing name. The name has been translated as the Demon Star associated with the eye of the Gorgon, Medusa, within the mythology tales of the hero Perseus. It is likely that Montanari first recorded the star's variability in 1667 yet John Goodricke in 1782 investigated a continuous series of its changes and came to the explanation of these as an eclipse in a system of stars. This is the first eclipsing binary star recorded and it provides a long base-line for understanding period changes and how stars in close proximity interact. The distance between the main stars is only 0.07 astronomical units (26 times Earth to Moon). The star is predicted to be faint at a primary minimum on Oct 19 at 22.4h and at other intervals of its period 2.867d. It changes from mag. 2.1 to 3.4. A host of bright comparison stars are nearby but rho Persei, the nearest is also a variable so it is wise not to use this.