MEETINGS

JULY MEETING

        The July meeting was introduced by John Vale-Taylor.   He mentioned the ongoing threat to what John referred to as our principle observation venue: i.e. Phil Berry’s garden.  Further details follow later in the Newsletter.

        John also mentioned the Astro-barbecue at the end of August on Monday the 29th as already mentioned at the head of the Newsletter and encouraged members to come along.

        Then he introduced the evening’s talk by our own Phil Berry.

Nebulae

by Phil Berry

        Phil said that from the questionnaire handed round some time ago, members had suggested a talk on nebulae and since this is one of his many interests, decided to prepare an illustrated presentation.

        He began by saying that the word nebula means “cloud” because that is what early astronomers saw through their telescopes.  Although as technology advanced these misty objects have become reclassified.         In 1889 astronomer Isaac Roberts astounded the world when he published an image he took of M31 in which dark lines could be resolved, suggesting that some of these clouds were more than just gas and dust.

M31 taken by Isaac Roberts and published in 1889

        Edwin Hubble put the matter to rest when he wrote a famous paper saying that most nebulae are in fact composed of billions of stars, some at great distances from the sun and that we were part of a galaxy we call the Milky Way.

        As the ability to take clearer and sharper images, modern methods resolve stars and dark areas.  Even those taken by today’s amateur astronomers are almost as good.  Phil illustrated this with a number of images of nebulae M80, a globular cluster that showed it to be composed of millions of individual stars at a distance of 28,000 light years.

        The next slide we were shown was of the Pleiades, M45.  We were told that this is an open cluster of middle aged class B stars but the smearing we see is caused by unrelated interstellar dust.  This is known as reflection nebulosity.  The next slide showed in detail how Merope, one of the brightest stars in the Pleiades is tearing apart some of this gas apart.

        An example of an emission nebula is the Rosette Nebula.  Phil said that this nebula is emitting its own light due to ultraviolet radiation from the very hot young stars that make up the cluster in the middle.

        A famous example of a dark nebula is the Horsehead nebula, although this can only be seen because of the ionised hydrogen behind it.  The cloud that appears as the horse’s head is re-radiating some of the light from behind as infra-red radiation giving the contrast.

        M1 is the Crab Nebula resulting from a powerful super-nova witnessed in 1054 when it was so bright that it was even visible in daylight for several weeks.

        We were told that the super-nova resulted when the mass of a companion star was gravitationally drawn into a white dwarf star, which eventually underwent rapid carbon burning and exploded, ejecting the equivalent of 1 solar mass.  It is during this catastrophic release of energy that elements heavier than iron are produced.

        Another example of a nebula is a Ring Nebula such as the famous one in Lyra.  Phil told how they are the result of a star that has used up much of its hydrogen fuel, having been converted into helium.  The star, a bit like our sun, becomes a Red Giant which rather than explode, ejects gases at much lower speeds over a period of time.  As the star evolves, it becomes a very hot white dwarf and it is its radiation that ionizes the ejected material to make it visible from the Earth, and as we are in line with it, it looks like a ring.

        A surprising object is a protoplanetary nebula such as the Red Rectangle Nebula in the constellation of Monoceros.  The image we were shown had been taken by the Hubble Space Telescope, and Phil told members that the strange nebula, looking rather like a huge cross began its life as a star similar to our Sun and is now nearing the end of its life.  The star is ejecting its outer layers at present but after a few thousand years time it will become hotter and the ejected gases will begin to fluoresce, producing a planetary nebula.  The red colour seen at present is suspected to be hydrocarbons forming in the cool outflow from the central star.

        Phil looked again at the Rosette Nebula to look at tiny clumps of very dark matter known as Bok Globules.  Bok was the astronomer in the 1940s who first observed these globules, which contain molecular hydrogen, carbon oxides, helium and silicate dust and it has now been confirmed that stars are being born inside them.

        Phil returned to the interesting story behind Isaac Roberts.  Born in Wales in 1829 he made his fortune in the building industry in Liverpool.  Eventually he was able to pursue his interest in astronomy and solved problems with guiding a telescope so that it would remain steadily tracking a particular point in the night sky, despite the rotation of the Earth.  This enabled him to take long-exposure photographs.

        In 1890 Roberts moved to Crowborough in East Sussex where he built an observatory onto the side of his house which was called “Starfield”.  The dome housed his 20-inch reflecting telescope.  Sadly, neither the house nor the dome are there any longer yet Phil did find a photograph of the site, still called Starfield but now a modern housing development.

Isaac Roberts home and observatory at “Starfield” in Crowborough

        We were shown two remarkable photographs taken by Roberts; one of the Great Andromeda Nebula taken in 1888, and one of the Veil Nebula taken shortly afterwards.  Both attracted the attention of the scientific world of the time.

        During Phil’s research for his talk he found that Isaac Roberts employed an assistant, W. S. Franks, an astronomer and accomplished photographer.  After Roberts’ death Franks remained at Starfield and writes that Roberts’ wife removed all 2,800 negatives although it appears that most of them had been taken by Franks under Roberts’ supervision.

        Phil ended by referring to future developments and mentioned the European VLT, Very Large Telescope array, consisting of four telescopes linked and synchronised electronically making it the largest Earth bound telescope.

        His final slide was of the immediate area around Betelgeuse in Orion.  A blanking disk was used to remove the contrast with the bright star itself which is so large that it is over four times as big as the Earth’s orbit around the Sun.  The image revealed a fainter nebula in turmoil around Betelgeuse.

        The talk was an excellent explanation of nebulae and was given despite Phil suffering near loss of voice.

        Note  Images of many of the nebulae can be found in the book “Universe – A Journey to the Edge of the Cosmos” by Nicholas Cheetham.  A copy has been kindly donated to the Society’s library by John Wayte.

UNUSUAL NOTES FROM THE SCIENTIFIC WORLD

        John Wayte has been looking at more weird stories in the world of science.

        He had found a report that the coolest star known is a Dwarf Brown star 75 light years away from us with a temperature of just 100o Celsius!

        The most accurate atomic clock to date has an accuracy of 1 part in 1017 or a second in 3 billion years.  Yet scientists are at present working on an even more accurate clock which has an accuracy of 4 parts in 1019, that is 1 second in 80 billion years and as John said, it is interesting to consider that the universe has only been around for 13.7 billion years.

        Oh; - and polar bears have been found through DNA research to be related to just one brown bear living at one time in Ireland…

FUTURE  MEETINGS

        Wednesday 21st September 2011 – Bob Seaney will be giving a talk about “The Multi-Universe”, a subject we may well have heard of yet know little.  Bob’s talks are always worth following.

        Wednesday 19th October 2011 – Our Director of Observations gives a talk about “Registax”, the free star programme available on the Internet.

        Wednesday 6th November 2011 – David Mannion talks to us about “Galileo and 400 Years of Telescopic Astronomy”.  David has three degrees in Astronomy and has been a teacher for 24 years.  He is also co-writer of a book of the same title as his talk to us tonight.

OTHER NOTES AND INFORMATION

LIGHT POLLUTION AVERTED?

        Our main venue for night sky observations has been Phil Berry’s garden and a few years ago a threat to his clear night sky was made by the planning application for flood lighting at an nearby adjacent tennis club.         Phil told the July meeting that planning permission had been applied for again and it gone to a judicial review.  The application had been rejected but as he said; they then had 19 days to appeal from the 7th of July.         We wait to hear the outcome…

SKY NOTES FOR AUGUST

Planets

Mercury is an evening object but is too low for observations to be made. It passes through an inferior conjunction on the 17th and then appears to the west of the Sun to become a morning object.  This coming apparition in late August/early September will provide the best early morning views of the planet this year for UK observers. The diagram shows the position of Mercury relative to the horizon. Don’t forget you should never sweep for Mercury with optical aid if the Sun is above the horizon.

Venus suffers a superior conjunction on the 16th of this month and is therefore invisible to us. It should reappear in the evening skies for us in the UK towards the end of November.

Mars at magnitude +1.4 is a morning object in Taurus rising at around 0230 by mid month.

Jupiter is only just a morning object rising at 0045 hrs BST in the middle of the month. By the months end it rises about fifteen minutes before midnight (BST) and at magnitude -2.5 it will be unmistakable just below the small constellations of Triangulum and Aries.

Saturn is still just visible low down in the west-south-west after sunset, but this will be your last chance to see it before it passes through a superior conjunction on October 13th. After that it becomes a morning object in mid to late October.

Lunar Occultations

In the table below I’ve only listed events for stars down to magnitude 7.0 that occur before midnight although there are others that are either of fainter stars or occur at more unsociable hours. DD = disappearance at the dark limb and RD = reappearance at the dark limb. Times are in BST.  

The three events shown in the table below should be easy to observe in a small telescope. Following on from our success in timing the 8th June graze occultation, all of these and would be ideal to use as practice in preparation for future graze expeditions. If possible I would like to assemble a few observers who are free on either of those evenings (or possibly all) to observe from somewhere around the Wadhurst area when we will attempt to time the disappearances as accurately as possible using either MSF time signals or stopwatches. Please let me know via the e-mail address at the end of this newsletter if you are interested and we can organise a communications “tree” to keep you up to date about location and viability due to weather. The Society has some telescopes that can be made available if you don’t have one of your own. If you want to come along and just watch the event without timing it, then that‘s also OK. The Society is looking at buying some electronic stop watches for timing such events that can be used by members.

Aug.

Time

Star

Mag.

Ph

PA °

5th

2051

SAO 158306

6.3

DD

70

9th

2119

4 Sagittarii

4.7

DD

122

11th

2148

57 Sagittarii

5.9

DD

104

The diagrams above show the position of the stars in question (large black dots) just before they disappear behind the dark portion of the Moon. The grey background is the path of the Moon and any small black dots are surrounding stars. The prediction software suggests the minimum aperture for the 3 events are 90mm, 40mm and 70mm respectively.

Phases of the Moon for August

First ¼

Full

Last ¼

New

6th

13th

21st

29th

ISS

Below are details of the passes of the ISS that occur before midnight as seen from Wadhurst and are magnitude -3.0 or brighter. The details of all passes including those visible from other areas can be found at:

www.heavens-above.com

Please remember that the times and directions shown below are for when the ISS is at its maximum elevation, so you should go and look a few minutes before. Times are in BST.

Aug.

Mag

Time

Alt°

Az.

15th

-3.5

2247

69

SW

16th

-3.3

2149

52

SSE

17th

-3.5

2227

88

NNW

18th

-3.5

2129

71

SSE

19th

-3.1

2031

47

SSE

19th

-3.4

2207

79

N

20th

-3.5

2108

88

S

20th

-3.3

2244

72

WNW

21st

-3.4

2146

77

N

22nd

-3.4

2048

81

N

22nd

-3.6

2224

81

SSW

23rd

-3.4

2125

83

N

24th

-3.3

2027

77

N

24th

-3.4

2203

62

SSW

25th

-3.5

2105

85

SW

26th

-3.3

2006

80

N

27th

-3.3

2044

68

SSW

Iridium Flares

The flares that I’ve listed are magnitude -4 or brighter although there are a lot more that are fainter, occur after midnight or at a lower altitude. 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 sometimes possible to see the satellite in advance of the “flare”, although of course it will be much fainter at that time.  Times are in BST.

Just a word of warning that these predictions are liable to change. There was originally going to be a bright (brighter than -4) flare on the night of the BBQ, but that has now disappeared from the predictions and I note that there are other changes in magnitude data.

Aug.

Time

Mag

Alt°

Az.

3rd

2212

-4

46

NE

4th

2206

-4

46

NE

6th

2318

-5

13

NNE

9th

2146

-5

54

ENE

10th

2140

-8

55

ENE

10th

2304

-4

19

NNE

10th

2304

-6

20

NNE

14th

2250

-7

26

NE

16th

2113

-8

62

ENE

17th

2107

-8

63

ENE

18th

2235

-7

32

NE

23rd

2040

-8

69

E

23rd

2215

-5

39

ENE

24th

2035

-4

70

E

26th

2027

-6

71

ESE

28th

2154

-4

45

ENE

30th

2006

-6

72

SE

The Night Sky in August (Written for 2200 BST mid month)

In the north, the plough is heading towards the horizon and both “Bears” lie to the west of the meridian. If the plough is sinking then Casseopeia and Perseus must be rising along with the (just) circumpolar Capella.

Looking east we see that Pegasus and Andromeda are fully on view as are some of the smaller constellations that surround the winged horse. These include Aries and Triangulum to the east, Lacerta to the north and Equuleus to the west. Below Pegasus lies Aquarius, which despite being a Zodiacal constellation is composed of faint stars that lack any obvious shape.

To the south we find the “Teapot” asterism that makes up part of Sagittarius, and a little to the west, on the meridian, is Antares, the brightest star in Scorpio - decidedly reddish in hue.

Still on the meridian but close to the overhead point we find the bright star Vega, one of the members of the summer triangle. Vega’s proximity to the zenith is a reminder that the Perseid meteor shower maximum is upon us.

In the west the bright star Arcturus is still prominent along with Corona Borealis and Hercules although this part of the sky is largely dominated by the faint and shapeless constellations of Serpens and Ophiuchus.

Meteor Showers

The Perseids.  

Regarded as one of the premier showers of the year, the Perseids in 2011 are somewhat hampered by the intervention of the Moon being full on the night of maximum. The shower is active from July 23rd until August 20th although at the two extremes rates are expected to be low. Activity should rise gradually to a peak (ZHR = 80) centred around 0500 BST on the morning of the 13th so watches from nightfall on the 12th should prove worthwhile although the fainter meteors will be lost to moonlight. Position yourself looking north with the Moon obscured by a building or tree if possible and try not to observe whilst standing - lying on a sun-lounger or similar with the head end raised slightly is far more comfortable. These are fast meteors that are often bright and regularly leave ionised trains behind them. When I observed this shower from an unobstructed site in Cornwall in 1999 they appeared in most areas of the sky and some even reached right across to the southern horizon. Wherever they appear you can easily tell if they belong to the shower by tracing them back to the area close to Perseus as shown in the diagram, where I have added three hypothetical meteors to demonstrate this.

If you project them back towards their origin and it is nowhere near the radiant then they are “sporadic” meteors and do not belong to this shower.  During the course of all showers the radiant drifts due to the Earth moving in its orbit around the Sun although to the casual observer the effect of this will be negligible.

Next year looks considerably better for the Perseids with respect to the Moon as during the early hours of the 13th a very thin waning crescent doesn’t rise until 0130 BST so its affect on proceedings should be limited.

Astro BBQ

There are several events that occur on the night of the BBQ that I have listed here as they do not appear in the tables above because of limitations on magnitude etc. There are no occultations as the Moon is new on the 29th.

Iridium Flare

Aug.

Time

Mag

Alt°

Az.

29th

2148

-3

44

NE (67°)

ISS

Aug.

Time

Mag

Alt°

Az.

29th

2053

-2.2

33

SSE

Starts at 2051 in the west  at altitude 10°

Ends at 2056 in the SSE at altitude 13°

57 Leonis - The Star That Blinked (Update)

You may remember that in the last newsletter I described our attempts at observing a graze occultation and the methods we used to time and record it. I have evaluated the results by plotting the location of observers against time to give the limb profile as shown in the diagram. The red dots are the events that we recorded - either disappearance or reappearance. You can see that if we had had more observers we would have had more red dots and so been able to draw the profile more accurately - particularly the larger of the two mountains which is something of a “best guess”. The observers that we had were spread over a distance of just over half a kilometre (.56 to be precise), but in future having gained more experience we will place them further apart to try and cover a larger portion of the lunar limb.

Once the results have been refined further they will be sent to Japan for them to be amalgamated with any others from that night in an attempt to provide a more accurate profile of that particular small section of the Moon.

The accurate timings of a graze occultation can be used for a variety of scientific purposes, a few of which are given here:-

·          They provide data for limb profiles to predict the appearance of Baily’s Beads during total solar eclipses. This permits calculations about the size of the Sun to be made to see if it is varying.

·          They can be used to measure the Earth’s rotation and whether it is slowing down.

·          They can provide more accurate data to enhance stellar positions.

There aren’t many hobbies like Astronomy that provide the participant with the chance to do something that has real scientific value. Also, there are only certain sections of Astronomy that provide that opportunity and the graze occultation is one of them.  If you are at all interested then I urge to take part in the total occultations that appear in the list above and use them as a “dummy run” for future grazes.

Brian Mills

DEFINITIONS OF TERMS USED IN ASTRONOMY

Baily’s Beads

As we’ve already said, the Moon’s topography is not smooth but is rough and undulating because of all the lunar features.  During a total solar eclipse when the Moon has almost completely covered the Sun, the last rays of sunlight shine through the lunar valleys just before totality.  These appear as numerous individual spots of light and vary depending on the exact presentation of the Moon towards the Earth at that time. They are named after the English astronomer, Francis Baily, who successfully described their cause after observing the annular eclipse of 1836.  If you watch a total solar eclipse from the edge of the path of totality you will see many more Baily’s Beads type of events.

Diamond Ring

The diamond ring effect occurs when sunlight shines through the very last valley on the Moon before totality begins - it is effectively the last Baily’s Bead.  As totality finishes you will see the diamond ring and Baily’s Beads on the opposite side of the Sun

Brian Mills

NASA’S SPACE PLACE

New GOES-R to Give More Tornado Warning Time

by Dauna Coulter and Dr. Tony Phillips

So far this spring, more than 1,400 tornadoes have struck the U.S.   Some of them have cut jaw-dropping trails of destruction across the countryside and, tragically, across inhabited communities, too.  Hundreds of lives have been lost in the onslaught.

Throughout the season, the National Weather Service has routinely issued tornado alerts. In the case of the Alabama tornadoes of April 27th, forecasters warned of severe weather five full days before the twisters struck.  Because they couldn’t say precisely where the twisters would strike, however, many of their warnings went unheeded. 

“If people get a hurricane warning, they often evacuate the area,” notes NOAA's Steve Goodman. “But we react differently to tornado warnings.”

Perhaps it’s because tornadoes are smaller than hurricanes, and the odds of a direct hit seem so remote.  Recent pictures from Tuscaloosa, Alabama, and Joplin, Missouri, however, show the perils of playing those odds.  Goodman believes that more precise warnings could save lives.

To fine-tune tornado warnings, NOAA will soon launch the first in a series of next-generation weather satellites – GOES-R (Geostationary Operational Environmental Satellites-R series). The spacecraft is brimming with advanced sensors for measuring key ingredients of severe weather including winds, cloud growth, and lightning.

“GOES-R will be the first geostationary spacecraft to carry a lightning sensor,” says Goodman, the GOES-R Program Senior Scientist. “Studies show that sudden changes in the total lightning activity correlate with storm intensity—and with tornadoes.”

The lightning mapper will detect and map not only cloud-to-ground lightning, but also bolts within and between clouds. The kind of cloud-to-ground lightning we see from our front yards accounts for only 15-20 percent of total lightning. To get a clear idea of a storm's intensity, meteorologists need to know about all the lightning—a view GOES-R can provide.

All by itself, the lightning mapper will provide 7 minutes more lead time in tornado warnings, according to Goodman. GOES-R’s state-of-the-art instruments will also improve long-range forecasts.

“The satellite's Advanced Baseline Imager (ABI), for instance, will provide a much clearer picture of clouds,” says NOAA research meteorologist Tim Schmit.  Compared to lesser instruments already in orbit, ABI can better detect super-cold “overshooting tops,” evidence of enormous energy and upward velocity that correlate with subsequent severe weather.

“Accurate advanced notice of high-risk tornadic conditions can cue officials to close schools and businesses even before tornadoes are actually detected,” says Schmit.

Forecasters doubt tornadoes can ever be predicted with 100% accuracy. The twisters are just too capricious.  GOES-R, however, is a step in the right direction.

Find out more about GOES-R’s unprecedented capabilities at:

http://www.goes-r.gov

Young people can learn more about tornadoes and all kinds of other weather at:

http://scijinks.gov

Caption:

This GOES image shows the storms that spurred the intense April 27 tornado outbreak in the southern U.S. Animation showing the development of weather can be seen at:

http://earthobservatory.nasa.gov/NaturalHazards/view.php?id=50347

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

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 2011 Newsletter should be with the Editor by August 28th 2011