“The Southern Cross”
HERMANUS ASTRONOMY CENTRE NEWSLETTER
JULY 2012
Welcome to this month’s newsletter, which we hope you enjoy reading.
The Centre is currently developing a news interest group on astro-photography.
At the monthly meeting on 21 June, Deon Krige, the committee member
responsible for this, gave a verbal overview of the aims of the group and also made
a request for interested members to contact him. He also sent out an e-mail to all
members, the main points of which are paraphrased below.
The overall purpose of the group will be to establish a platform which will enable
members to develop and share knowledge, information, and experience on astrophotography. All levels of expertise will be welcome, and it is not necessary to own
a telescope or advanced photographic equipment.
Activities of the group will include all aspects of both capturing and processing
images. These will include member’s own images, and use of images accessible
online. A dedicated webpage on the Centre’s website will be developed to provide
information and links, and also to allow members final images to be displayed.
If you are interested in finding out more about the group and/or wanting to join it,
please contact Deon at astronomy.hermanus@gmail.com
WHAT’S UP?
The largest and brightest globular cluster, Omega Centauri (NGC 5139), is visible
high in the southern winter sky. Forming an almost equilateral triangle with Alpha
Centauri (the Pointer furthest from the Southern Cross) and Beta Crucis at the top
of the Southern Cross, it is visible to the naked eye as a hazy star about the size of
the full Moon. But even with binoculars, its breathtaking beauty and density,
created by several million stars, is revealed. Originally discovered by Halley in 1677
and listed as a nebula, it was William Herschel, in the 1830s, who recognised it as a
globular cluster. Located 17,000 ly away, it has a diameter of 180 ly. About 12
billion years old, like other globular clusters, its stars are some of the oldest in the
Milky Way, most within the cluster being of a similar age.
LAST MONTH’S ACTIVITIES
Monthly centre meeting On 21 June, Centre member Johan Retief gave an
informative and amusing presentation on pulsars, pulsating stars which behave like
‘lighthouses in the sky’. He described the accidental discovery of regular, rapid
radio signals by Jocelyn Bell in 1967 and the subsequent search to find their origin.
Eventually, small, but fast rotating massive neutron stars, the remnants of
supergiant stars which died in huge supernova explosions, were found to be the
source. In some neutron stars, the emissions from their magnetised iron cores emit
concentrated streams of radio waves which, if in line with Earth, we can detect as
pulsing signals. Over 2,000 pulsars have so far been identified. Johan explained
further that our solar system is probably the result of material liberated during
supernova explosions, and the meeting ended with a viewing of the DVD ‘Our Sun’s
brilliant future’ which explained the end stages of a comparatively small star like
the Sun.
Interest groups
Cosmology On 4 June, 25 members attended the third set of two episodes of
the DVD series ‘Modern Physics for beginners’ presented by Professor Richard
Wolfson. They were ‘Speed c- relative to what?‘(Lecture 5) and ‘Earth and the
ether: a crisis in physics’ Lecture 6).
Beginner’s astronomy 13 people (8 members, 5 visitors) attended the meeting
held on 11 June. In addition to the indoor presentations, limited cloud cover
allowed for star-gazing, particularly of Saturn.
Other activities
Sidewalk astronomy No one attended the session on 15 June, and only four did
so on 16 June. The committee is planning to review the scheduling of these events
during the winter months.
Article in Whale Talk An article by John Saunders titled ‘There are some very
‘weird stars’ out there!’ was published in the June/July issue of Whale Talk
THIS MONTH’S ACTIVITIES
Monthly centre meeting This will take place on 19 July at 7 pm at SANSA. The
topic ‘Optical instrumentation at SALT’ will be presented by Lisa Crause from SAAO
in Cape Town.
Weather permitting, there will be an opportunity for stargazing from the SANSA car
park. An entrance fee of R20 will be charged per person for non-members and R10
for children and students.
Interest group meetings The Cosmology group meets meeting on the first
Monday of the month at 7 pm at SANSA. From April to September, the DVD series
‘Modern Physics for beginners’ presented by Professor Richard Wolfson will be
shown. The DVDs for the meeting on 2 July are ‘Einstein to the rescue’ (Lecture
7) and ‘Uncommon sense: stretching time’ (Lecture 8).
An entrance fee of R20 will be charged per person for non-members and R10 for
children and students. For further information on these meetings, or any of the
group’s activities, please contact Pierre Hugo at pierre@hermanus.co.za
Beginner’s astronomy Meetings take place monthly on the second Monday of
the month at 7 pm at SANSA. The meeting on 9 July will include presentations on
the common theme of the Sun – viewing of the DVD ‘Our sun, the nearest star’ and
a talk by Pierre de Villiers and Johan Retief on how to observe the Sun.
An entrance fee of R20 will be charged per person for non-members and R10 for
children and students. Please contact Pierre de Villiers at
pierredev@hermanus.co.za for further details.
FUTURE ACTIVITEIS
Sidewalk astronomy Details of the next sessions will be circulated when they
have been arranged.
Visits to observatories A date for the Cederberg visit in September/October is
still awaited. Details will follow. The visit to Sutherland on 10-11 November has
been arranged. Details will be sent out later in the year.
2012 MONTHLY MEETING DATES
These take place at 7 pm at SANSA.
19 July
‘Optical instrumentation at SALT‘ by Lisa Crause, SAAO, CT
23 August
‘Topic: TBA Presenter: Case Rijsidjk
20 September ‘Spreading the word: enlarging local interest in astronomy’
by Kechil Kirkham, Chair, ASSA Centre.
18 October
‘The Herschels – a family of astronomers’ by John Saunders
15 November ‘Tracking satellites and astronomical objects’ by Greg
Roberts, amateur astronomer and satellite chaser
14 December. Christmas party
EDUCATION CENTRE AND OBSERVATORY
Overstrand Municipality has kindly agreed that submission of the fynbos and
service infrastructure reports can be postponed until July, providing the leeway
required by the experts for their completion. It is still anticipated that the lease
application will be considered by the full Council at their meeting in late August.
In order to meet the costs of the reports, and any other remaining expenses
incurred as part of the planning process, the ‘Friends of the Observatory’ campaign,
to which members have already generously contributed, is continuing. Both single
donations and small, regular monthly donations are welcome.
Contributions can take the form of cash, cheque or online transfer, The ABSA bank
details are as follows:
Account name – Hermanus Astronomy Centre
Account number – 9230163786
Branch code – 632005.
If you make an online donation, please include the word ‘pledge’, and your name,
unless you wish to remain anonymous.
For further information, please contact John Saunders on 028 314 0543 or at
shearwater@hermans.co.za
ASTRONOMY NEWS FROM STEVE KLEYN
The Voyagers. 22 June: Voyagers 1 and 2 were launched nearly 35 years ago in
1977 when we were just 20 years into the ‘Space Age’. There was no certainty as
to how long they would last or how far they would get. Today, they are still going
strong and are about to leave the comfort of their place of origin; our little world of
Earth in the Solar System, and take the plunge into Deep Space; the realm of
interstellar space.
Voyage 1 is about to cross the boundary of the edge of the heliosphere – the
magnetic field of the Sun blown outwards into a huge bubble by the solar wind.
The heliosphere is what shields us from a large proportion of dangerous high
energy cosmic and gamma ray radiation pouring in from the neighbourhood of the
Milky Way and outer space. A recent rapid increase in this radiation striking the
spacecraft is the signal that they are leaving the heliosphere's protection.
From early 2009 to 2012 there was a slow increase of strikes of about 25%, but
now suddenly, since 7 May 2012, strikes have been increasing at a rate of 5% per
week. This is a sure sign that crossing the frontier into deep space beyond the
heliosphere's protection, 18 billion kms from Earth, is imminent.
When the frontier has been left behind there will be several changes in the
radiation and particles striking the spacecraft. Many energetic particles from the
Sun will no longer be evident and the craft's magnetic field, which has been
controlled by the Sun's up till now, will change direction under the influence of the
unknown magnetism of interstellar space.
Voyager 2 is hot on the heels of Voyager 1, but because of its slower pace, lags a
few billion kilometres behind. These two little spacecraft are going the distance
and have proven to be tough and reliable: a testament to the designers, builders
and controllers. The “Space Age” is nearly 55 years old.
Source; NASA news bulletins and archives.
(For more news from the edge of the solar system, please visit voyager.jpl.nasa.gov )
Some quick facts about the Voyager missions The primary mission was the
exploration of Jupiter and Saturn. After making a string of discoveries there -- such
as active volcanoes on Jupiter's moon Io and the intricacies of Saturn's rings -- the
mission was extended. Voyager 2 went on to explore Uranus and Neptune, and is
still the only spacecraft to have visited those outer planets. The adventurers'
current mission, the Voyager Interstellar Mission (VIM), will explore the outermost
edge of the Sun's domain. And beyond.
Launch: Voyager 2 launched on 20 August 1977, from Cape Canaveral, Florida
aboard a Titan-Centaur rocket. On 5 September, Voyager 1 was launched second,
although on a faster trajectory, also from Cape Canaveral aboard a Titan-Centaur
rocket.
Between them, Voyagers 1 and 2 explored all the giant planets of our outer solar
system, Jupiter, Saturn, Uranus and Neptune; 48 of their moons; and the unique
system of rings and magnetic fields those planets possess.
Closest approach to Jupiter occurred on 5 March 1979 for Voyager 1; 9 July 1979
for Voyager 2.
Closest approach to Saturn occurred on 12 November 1980 for Voyager 1; 25
August 1981 for Voyager 2.
Closest approach to Uranus occurred on 24 January 1986 by Voyager 2.
Closest approach to Neptune occurred on 25 August 1989 by Voyager 2.
The Voyager spacecraft will be the third and fourth human spacecraft to fly beyond
all the planets in our solar system. Pioneers 10 and 11 preceded Voyager in
outstripping the gravitational attraction of the Sun, but on 17 February 1998,
Voyager 1 passed Pioneer 10 to become the most distant human-made object in
space.
Source: NASA news bulletins and editorial.
New Telescopes - big and small The recent breaking news of the awarding of
the SKA contract has swamped the equally exciting news about the new BIGGEST
and SMALLEST telescopes now on the cards.
The biggest The European Southern Observatory (ESO) is to build the largest
optical/infrared telescope in the world. At a meeting in Garching, near Munich, the
ESO Council approved the European Extremely Large Telescope (E-ELT)
Programme, pending confirmation of four so-called ad referendum votes. The EELT will start operations early in the next decade. It will be the biggest eye on the
sky: a huge 39.3 metre segmented-mirror telescope sited on Cerro Armazones in
northern Chile, close to ESO’s Paranal Observatory.
The Optical configuration of the E-ELT
An Artists impression of the E-ELT Observatory. (Note the diminutive sizes of cars and buses
parked around the structure).
The Smallest Scientists from The Ohio State University bucked the trend (of very
big telescopes) last week when they announced having spotted two exoplanets
using the diminutive Kilodegree Extremely Little Telescope (KELT North) in
southern Arizona. (Its twin, KELT South, is in South Africa.)
Astronomer Joshua Pepper (Vanderbilt University) built KELT North as part of his
doctoral dissertation while at Ohio State. The scope sports a lens about as
powerful as a high-end digital camera, says current OSU doctoral student Thomas
Beatty, a member of the team behind the planetary find. The telescope, which
cost less than $75,000 to build, performs automated, wide-field surveys of the
northern sky. It takes in a 26°-square field of view through an off-the-shelf 80mm, f/1.9 lens and CCD camera. The telescope itself could "almost fit in a
shoebox" and reaches only chest height when sitting on its mount, says Beatty.
Credit; Joshua Pepper
Pint-size though it may be, the planets it found are anything but. The more typical
of the two, KELT-2A b, circles the primary star of the binary HD 42176 in the
constellation Auriga, about 417 light-years distant. It's a third again larger than
Jupiter and orbits every 4.1 days.
The KELT team’s second discovery was argued to "reset(s) the bar for weird.”
KELT-1 b is 850 light-years from Earth, in the constellation Andromeda. It’s slightly
larger than Jupiter but 27 times more massive, a superdense ball of metallic
hydrogen just 2 million miles from its star and whipping through its ‘yearly’ orbit in
just 29 hours.
Source: Sky and Telescope 20 June 2012.
DID YOU KNOW?
A brief history of the telescope Part 4 Seeing much more clearly:
technology catches up with design
A massive Herschel
telescope
Edwin Hubble at the
The way a parabolic mirror
100 inch Hooker telescope focuses light at one
Whatever their comparative design strengths and weakness, all early reflecting
telescopes suffered the same underlying technical limitations. It wasn’t until half a
century after Newton built his first telescope that, in 1721, James Hadley, an
English mathematician, having solved many of the problems of making a parabolic
mirror, demonstrated a reflecting telescope with a six inch parabolic mirror that
produced images which competed successfully with the best images produced by
the cumbersome refractors of the day. Newton had known that a deeper parabolic
design was better than a shallower spherical one, but the latter demanded less
technical accuracy in its grinding. Spherical mirrors are unable to bring all the
incoming light from a distant object to a common focus. This so-called spherical
aberration occurs because the reflection of rays striking the outer edges of the
mirror does not converge at the same point as that of rays reaching the central
area.
In contrast, a parabolic mirror, with its steeper sides, is able to focus all incoming
light onto one point, producing a clearer image. The parabolic design does have its
own limitations, but it is a huge improvement on spherical mirrors. Following
Hadley’s achievement, the size of reflecting telescopes grew rapidly, primary mirror
diameter doubling approximately every fifty years.
The first giant reflecting telescope is generally accepted to be that of William
Herschel. Constructed in 1789, one of over 400 which he built himself, it had a 49
inch mirror and a focal length of 40 feet. To avoid the loss of light from a
speculum secondary mirror, he had the primary mounted at an angle to enable him
to observe the image directly. Despite the physical challenges associated with
telescopes of such a scale, in 1845, Lord Rosse built the 72 inch ‘Leviathan of
Parsonstown’ with a focal length of 54 feet.
Despite this literal growth in reflectors, the underlying problems of using speculum
for mirrors persisted. Development of the achromatic refractor lens, made of
several types of glass which, together, counteracted chromatic aberration, led to a
resurgence in the development of refracting telescopes, enabling them to grow
very large as well. Ultimately, the effect of gravity on lenses which, by the end of
the 18th century, reached up to nearly 50 inches in diameter proved to be the force
which prevented construction of refractors any larger than that. Unlike mirrors,
which can be supported from underneath, lenses are supported round their edges,
a requirement which eventually makes additional weight, literally, unsupportable.
Running in parallel with the revival of the refractor were developments in mirrors
which eventually enabled reflecting telescopes to overtake refractors in the size
race. According to Pliny the Elder, the Phoenicians accidentally discovered glass
around 3,500 BC when cooking on sand. Since then, many uses for glass were
found, but it was only in the mid 19th century that the use of glass in mirrors was
perfected. In 1857, Leon Foucault finetuned the process of silvering, the chemical
process of depositing an ultra-thin layer of reflective silver on the surface of a piece
of glass. This achievement created the first optical quality glass mirrors and literally
opened up the skies to astronomers. The silver layer was not only much more
reflective and longer lasting than the finish on speculum, it could be removed and
reapplied without altering the shape of the mirror.
Access to improved mirrors led to a mushrooming in telescope size, and a
concomitant explosion in knowledge and understanding of celestial objects and the
nature of space. Very large silver on glass telescopes like the 60 inch Hale
telescope at Mount Wilson Observatory (1908) and the 100 inch Hooker telescope,
also at Mount Wilson (1917) were built. It was use of the latter which enabled
Hubble to observe the expansion of the universe.
The next great advance in mirror design took another fifty years when, in 1932, the
use of long-lasting aluminium coatings on mirrors was perfected. The 200 inch (5
metre) Hale Reflector at Mount Palomar Observatory, completed in 1948, was the
largest telescope in the world until the Russian 238 inch (6 metre) Bolshoi
telescope was built in the mid 1960’s. However, its size made it physically very
difficult to use. The construction and use of even larger telescopes had to await
the introduction of methods other than the rigidity of glass to hold the correct
shape of the mirror. Advances in mirror design enabled them to be thinner and
lighter, and computerisation has made smaller mounts possible. Computerisation
has also led to the development of adaptive optics, the process which reduces the
effects on optical clarity of the motion of air currents in the atmosphere, further
improving the quality of images.
Catadioptric telescopes are the third type of optical telescope. Developed only
in the mid-20th century, they combine the use of lenses and curved mirrors.
Developed from the Schmidt camera, the inclusion of a convex lens in addition to
the primary mirror addresses an aberration found in parabolic mirrors. While they
prevent spherical aberrations, enabling all reflecting rays to converge at the same
point, their shape creates distortions at the edges. The addition of a lens
counteracts these distortions, making this design particularly useful in achieving a
wide field of view. Combined with the Cassegrain telescope, the SchmidtCassegrain is very popular for amateur use. Large Schmidt telescopes are used for
research involving large areas of sky eg astronomical surveys, comet and asteroid
searches.
Sources: http://en.wikipedia.org, Oxford dictionary of astronomy, Astronomy (Dorling
Kindersley – Eyewitness companions, Fitzgerald, M (20050 Stars of the southern skies (2nd
ed), Fairall, A (2002) Starwatching
For more information on the Hermanus Astronomy Centre and its activities, visit
our website at www.hermanusastronomy.co.za
COMMITTEE MEMBERS
John Saunders (Chairman)
028
Laura Norris (Treasurer)
028
Peter Harvey (Secretary, including membership)
028
Pierre de Villiers (Education centre and observatory))
028
Derek Duckitt (Website editor)
082
Lynette Geldenhuys (Education co-ordinator)
028
Deon Krige (MONET project and astrophotography)
028
Jenny Morris (Newsletter editor)
071
Non-committee members with roles:
Pierre Hugo (Cosmology interest group co-ordinator)
028
Steve Kleyn ( Technical advisor & newsletter astronomy news)
Johan Retief (Monthly sky maps)
028
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