MEETINGS

JULY MEETING

The July meeting was introduced by Phil Berry who began by mentioning the forthcoming Astro-barbecue at Greenman Farm. Details follow under Further News and Information” later in the Newsletter.

Our main speaker for the meeting was then introduced.

Introduction to Radio Astronomy

by Steve Jackson from Ashford Astronomical Society.

Steve began his talk by describing his career in radio engineering which included work for the Ministry of Defence, Marconi Instruments and Muirhead Avionics.

He used this background to talk about an important part of astronomy. He told us that many celestial objects radiate at radio as well as optical and other frequencies and some that can only be detected through radio waves.

One important advantage is that radiation at radio frequencies can be “seen” through cloud and in daylight and is not weather dependant.

The disadvantage as far as the amateur is concerned is that it is not something one can do from the back garden and the data collected requires knowledge to make sense of.

Examining the electromagnetic spectrum, Steve explained that Radio was defined as waves from 10 metres down to just millimetres and then showed us various aerial arrays and dishes used in radio astronomy.

In 1931 Karl Jansky of Bell Telephone Laboratories was researching worldwide radio communication and found that there were certain parts of the sky from which he was receiving concentrations of noise that could not be manmade. By observing one of these concentrations Jansky found that it took the time of a sidereal day to reach the same point in the sky and on further investigation discovered that this point was towards the middle of the Milky Way in Sagittarius.

Then in 1937, Reber built a radio reflecting dish to carry out more specific research. More and more interest created the development of bigger and better aerials of which the largest is the Arecibo dish built in a natural valley on Puerto Rico.

Other steerable radio telescopes mentioned were, the huge Ratan 600 telescope in Russia, the Green Bank telescope in West Virginia and the Jodrell Bank radio telescope in Cheshire.

In the challenge to increase sensitivity, Steve introduced us to the concept of interferometery where several receiving aerials are linked together into one huge array with the use of optical fibre communication links and computers. One he introduced us to was “e-Merlin” commissioned by Manchester University and will use seven radio telescopes around the Midlands. There is a good website at: www.e-merlin.ac.uk

Some of arrays are so big that they use telescopes on opposite sides of continents so producing the sensitivity of one Very Large Base Line aerial (VLBA).

There is even a “Do-It-Yourself” portable radio telescope available in the USA and can be seen at www.elexp.com which allows basic investigation.

Following this fascinating introduction to radio astronomy, Steve played a number of recordings of eerie sounds that have been recorded from around the planet Jupiter such as Jovian Whistlers and one of the Jovian Chorus being emitted from plasma waves in the upper atmosphere of the giant planet. He told us that Ashford Astronomical Society is going to have a go at receiving some of these effects next year.

Steve then turned to Pulsars and played the sound detected as they rotate providing they are in-line with earth. One was PSR 032+54 with a pulse rate of 1.4 seconds. PSR 0833-45 is rotating so fast that the pulse rate is 11 times per second and the last one he played for us was rotating so fast at 642 pulses per second that it sounded like one continuous tone. It is incredible to think that a collapsed star can rotate at this fantastic rate!

Steve concluded his talk by mentioning SETI, the Search for Extra Terrestrial Intelligence which looks for any form or sign of unaccountable signals received from outer space and then closed by showing a composite picture of the earth at night taken from earth satellites and revealing the amount of artificial light emitted from communities on the Earth.

The night sky in August

by Brian Mills

After the coffee break Brian Mills, our Director of Observations, introduced the night sky in August which appears in full later in the Newsletter but one piece of news was of the discovery of the largest star ever discovered at 270 times more massive than the Sun. It is in the Magellanic Cloud so can only be seen from the southern hemisphere.

FUTURE MEETINGS

Saturday 28^th August 2010 – There is no meeting of the Society in August, but as mentioned earlier, Michael Harte is generously inviting us to hold an Astro-barbecue at Greenman Farm.

This is well worth putting in your diary.

In the past some of us have taken along telescopes, binoculars and anything else we think would be useful to see the night sky in late August.

Any member of the Society is welcome to bring drink and food to cook on a barbecue and then take advantage of the darkening skies to view whatever is in the sky at that time. See further notes below.

Wednesday 15^th September 2010 – Details to follow

Wednesday 20^th October 2010 – Ian King is giving a talk with the intriguing title; “How Not to Build a Telescope”

Wednesday 17^th November 2010 – Our own Trevor Grey will be giving a talk entitled “It Is Rocket Science”

Wednesday 15^th December 2010 – Brian Mills gives a very appropriate talk about “The Star of Bethlehem”.

OTHER NEWS AND INFORMATION

ASTRO-BARBECUE

Our host for this year’s Astro-barbecue, Michael Harte, suggests that members aim to arrive from about 1900.

All members are invited and those with telescopes or binoculars are invited to bring them along, although it is an evening to just come and enjoy. Michael provides the barbecue facilities and all guests need to bring is food to cook and their own drink. Michael does suggest bringing some warm clothing as it is the end of August.

It has been a fabulous event in the past and is well worth the opportunity to socialise and perhaps spend some time using the telescopes that will be there.

Greenman Farm is situated on the B2099 past Wadhurst railway station and about 200 yards west of the railway bridge over the road. For those with SatNavs the Post Code is TN5 6LE.

SKY NOTES FOR AUGUST

Planets

Mercury reaches its greatest elongation east of the Sun on the 7^th of the month but is poorly positioned for us in the UK for this apparition. The problem is that at this time of year in the late evening the ecliptic lies almost parallel to, and not far above, the horizon. As the ecliptic is the plane in which we generally see the planets, then it becomes clear that they will never be high in the sky at this time.

Venus is still a brilliant evening object at magnitude -4.2. It continues to move east of the Sun until the 20^th of the month when although it will reach its greatest eastern elongation it will set only an hour after the Sun because of the position of the ecliptic as detailed above.

Mars at magnitude +1.5 is effectively no longer observable setting as it does an hour after the Sun.

Jupiter rises by 22.00 at mid month and shines at magnitude -2.8 in the constellation of Pisces as it approaches opposition on September 21^st. The diagram shows the planet relevant to the eastern horizon on the night of Perseid maximum. Uranus is nearby but will be a binocular object at magnitude 5.7.

Saturn is also lost to us in the glow of twilight, setting an hour after the Sun.

Lunar Occultations

Sadly, once again, there are very few events for reasonably bright stars that occur before midnight.

DD = disappearance at the dark limb whilst RD = reappearance at the dark limb.

Times are in BST.

Aug	Time	Star	Mag.	Ph	PA °
20^th	21.01	SAO 187679	7.4	DD	125
21^st	23.10	SAO 163171	7.7	DD	79
22^nd	23.07	SAO 163886	7.6	DD	142
25^th	21.39	SAO 146412	6.2	RD	276
26^th	21.31	SAO 128329	7.4	RD	253
28^th *	22.43	SAO 92310	6.9	RD	272

* Event occurs on the night of the WAS BBQ

The next diagram describes what is meant by the phrase “disappearance at the dark limb”.

As well as being carried across the sky from east to west with all the other heavenly bodies, the Moon has its own proper motion that causes it to appear to move gradually from west to east. This is not apparent to the naked eye, but it becomes more obvious if you observe the Moon when it is close to a star, especially when that star is then covered up or “occulted” by the Moon. If this happens between “new” and “full” (waxing) then almost always the star’s light is extinguished by the dark or unlit portion of the Moon. This is a dark limb disappearance (DD). The star reappears later on the bright limb but will be unseen due to the overwhelming lunar brightness.

A reappearance at the dark limb (RD) occurs in the majority of cases when the Moon is waning (between “full” and “new”). The Moon will pass in front of the star and occult it with the sunlit portion - the bright limb - but this will not be visible because the Moon will drown out the light of the star. However, it will be possible to see the star reappear from behind the unlit portion a while later as shown in the diagram. Remember that the Moon moves eastwards by an amount equal to its own diameter in approximately one hour.

Phases of the Moon for August

Last ¼	New	First ¼	Full
3^rd	10^th	16^th	24^th

ISS

During the first part of August the ISS is only visible in the early hours of the morning. Later in the month there are relatively few passes that occur before midnight so I have included some that are fainter than I would normally do. The details of all passes can be found at www.heavens-above.com Please remember that the times shown below are for when the ISS is at its maximum elevation, so you should be able to see it for a few minutes before and after these times. Times are all BST.

Aug	Mag	Time	Alt°	Az.
25^th	-1.5	21.58	18	SSW
26^th	-2.0	20.52	18	SE
26^th	-1.6	22.25	21	WSW
27^th	-3.0	21.18	38	SSE
28^th*	-2.0	20.10	20	SE
28^th*	-3.7	21.45	73	SSE
29^th	-3.1	20.37	42	SSE
29^th	-3.2	22.12	63	WNW
30^th	-3.7	21.04	77	SSE
30^th	-1.5	22.37	26	W
31^st	-3.6	21.30	79	N

*Events occur during the WAS BBQ

Iridium Flares

The flares that I’ve listed are magnitude -4 or brighter although there are a lot more that are fainter, occur at lower altitudes or after midnight. I’ve included a fainter event on the 12^th because this is the night of Perseid maximum, and also a few others that are quite low down but are very bright to compensate. If you wish to see a complete list, or obtain timings for somewhere other than Wadhurst, go to www.heavens-above.com

Remember that when one of these events is due it is often possible to see the satellite in advance of the “flare”, although of course it will be much fainter at that time. Times are all BST.

Aug	Time	Mag	Alt°	Az.
2^nd	23.06	-6	18	W
4^th	22.49	-6	16	W
5^th	23.15	-6	11	WNW
7^th	23.52	-7	34	WSW
9^th	21.32	-6	20	NNW
10^th	23.43	-6	30	WSW
12^th	21.00	-4	29	NNW
12^th	23.37	-7	28	WSW
12^th	23.40	-2	27	WSW
13^th	23.34	-5	27	WSW
15^th	23.32	-7	24	WSW
16^th	20.40	-4	34	NNW
17^th	23.28	-7	21	WSW
20^th	23.28	-5	16	W
21^st	23.33	-6	13	W
22^nd	23.35	-6	12	W
29^th	21.44	-6	13	N
31^st	21.25	-6	19	N

The Night Sky in August

Just a reminder that when I talk about what is visible each month I take mid-month at 22.00hrs as an arbitrary date and time. The view will be the same at 23.00 on the 1^st of the month and at 21.00 on the 30^th of the month.

In the north Ursa Major is still sinking towards the horizon whilst Cassiopeia and Cepheus are climbing. Now is a good time to look for the head of Draco as it lies close to the zenith. The bright star Capella (in Auriga) is easily visible just above the northern horizon as is the whole of Perseus.

In the east the square of Pegasus has risen (although with one corner pointing toward the horizon it looks more like a diamond) and from its leftmost corner Andromeda stretches towards Perseus. The bright star Deneb lies above Pegasus and is almost due east. Below the square, Pisces is rising along with Jupiter and Uranus which both lie within its borders.

Looking south, Sagittarius is low down whilst slightly west of it is the bright star Antares in Scorpio. The faint constellations of Ophiuchus and Serpens take up a large part of the southerly aspect at this time although Aquila is approaching the meridian along with the small but recognisable groups of Delphinus and Sagitta. The bright star Vega in Lyra is almost overhead.

In the west Virgo and Leo are setting but Arcturus in Bootes (due west) and Corona Borealis are still prominent whilst just east of them lies Hercules.

Meteors

The Perseid meteor shower reaches its maximum on the night of August 12^th/13^th although it does not end until the 20^th. On the night of maximum the ZHR (zenithal hourly rate) is predicted to be around 80 to 100 whilst the nights either side of this should also see a reasonable display particularly as the Moon is out of the way this year. The meteors are often bright and fast with a fair proportion leaving ionised trains behind. The position of the radiant is shown (it does move during the shower) in the diagram although it is rare to see meteors very close to it. On occasions I have seen meteors disappear over the opposite (southern) horizon, so they could appear pretty much anywhere. I find the best position is to lie - standing is too painful on the neck - facing roughly north on a sun bed with the head raised slightly.

Brian Mills

DEFINITIONS OF TERMS USED IN ASTRONOMY

For the last few months we have looked at some definitions of terms we use in astronomy, and this month I’ve included a few more.

Zenith

This refers to the point in the sky that lies exactly overhead.

Zenithal Hourly Rate (ZHR)

This refers to the number of meteors that would be seen if the radiant lay at the zenith. If this were the case then no meteors would go unseen below the horizon and there would be almost no reduction in events due of extinction by the Earth’s atmosphere.

Extinction

This is an effect of observing through the Earth’s atmosphere where particles in the air reduce the amount of light reaching the observer. The diagram shows how this is more apparent when viewing near the horizon because of the increased thickness of atmosphere that it is necessary to look through to view an object in direction “B” compared to direction “A” (overhead).

Meridian

This refers to the great circle that passes through the north point (on the horizon), the north celestial pole, the zenith and the south point (on the horizon). The Prime Meridian, better known as the Greenwich Meridian is at longitude 0°.

Culmination

An astronomical body is said to culminate when it crosses an observers meridian at which time it will have reached it’s highest point above the horizon.

Brian Mills

NASA’S SPACE PLACE

The Sun Can Still Remind Us Who’s Boss

by Dr. Tony Phillips

Grab your cell phone and take a good long look.  It's indispensible, right?  It tells time, surfs the web, keeps track of your appointments and, by the way, also makes phone calls. Modern people can hardly live without one.

One good solar flare could knock it all out.

“In the 21st century, we’re increasingly dependent on technology,” points out Tom Bogdan, director of NOAA's Space Weather Prediction Center in Boulder, Colorado. “This makes solar activity an important part of our daily lives.”

Indeed, bad space weather can knock out power systems, telecommunications, financial and emergency services—basically, anything that needs electronics to work. That’s why NOAA is building a new fleet of “space weather stations,” the GOES-R satellites.

“GOES-R will bring our existing fleet of weather satellites into the 21st century,” says Bogdan.  “They're designed to monitor not only Earth weather, but space weather as well.”

NOAA's existing fleet of Geostationary Operational Environmental Satellites (GOES) already includes some space weather capabilities: solar ultraviolet and X-ray telescopes, a magnetometer and energetic particle sensors.  GOES-R will improve upon these instruments and add important new sensors to the mix.

One of Bogdan’s favorites is a particle detector named “MPS-Low,” which specializes in sensing low-energy (30 ev – 30 keV) particles from the sun.

Who cares about low-energy particles? It turns out they can be as troublesome as their high-energy counterparts. Protons and other atomic nuclei accelerated to the highest energies by solar flares can penetrate a satellite’s exterior surface, causing all kinds of problems when they reach internal electronics. Low-energy particles, particularly electrons, can’t penetrate so deeply. Instead, they do their damage on the outside.

As Bogdan explains, “Low-energy particles can build up on the surfaces of spacecraft, creating a mist of charge. As voltages increase, sparks and arcs can zap electronics—or emit radio pulses that can be misinterpreted by onboard computers as a command.”

The Galaxy 15 communications satellite stopped working during a solar wind storm in April 2010, and many researchers believe low-energy particles are to blame. GOES-R will be able to monitor this population of particles and alert operators when it’s time to shut down sensitive systems.

“This is something new GOES-R will do for us,” says Bogdan.

The GOES-R magnetometer is also a step ahead. It will sample our planet’s magnetic field four times faster than its predecessors, sensing vibrations that previous GOES satellites might have missed. Among other things, this will help forecasters anticipate the buildup of geomagnetic storms.

And then there are the pictures. GOES–R will beam back striking images of the sun at X-ray and extreme UV wavelengths. These are parts of the electromagnetic spectrum where solar flares and other eruptions make themselves known with bright flashes of high-energy radiation. GOES-R will pinpoint the flashes and identify their sources, allowing forecasters to quickly assess whether or not Earth is in the “line of fire.”

They might also be able to answer the question, Is my cell phone about to stop working?

The first GOES-R satellite is scheduled for launch in 2015. Check www.goes-r.gov for updates. Space weather comes down to Earth in the clear and fun explanation for young people on SciJinks http://scijinks.gov/space-weather-and-us.

This article was provided by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

Caption:

In spite of Earth’s protective magnetosphere, solar storms can wreak havoc with Earth satellites and other expensive electronics on the ground.

CONTACTS

Chairman John Vale-Taylor

pjvalet1@btinternet.com

Secretary & Events Phil Berry 01892 783544

phil.berry@tiscali.co.uk

Treasurer Mike Wyles 01892 542863

mike31@madasafish.com

Editor Geoff Rathbone 01959 524727

geoff@rathbone007.fsnet.co.uk

Director of Observations Brian Mills 01732 832691

Brian@wkrcc.co.uk

Wadhurst Astronomical Society website:

www.wadhurst.info/was/

SAGAS web-site www.sagasonline.org.uk

Any material for inclusion in the September 2010 Newsletter should be with the Editor by August 28^th 2010