OCTOBER NEWSLETTER 2006
INDEX: MEETINGS, OTHER NEWS, CONTACTS
COMMITTEE
MEETING
Members
of the Society's Committee are respectfully reminded that there will be a meeting
of the Committee on Monday October 9th 2006 at the Abergavenny Arms, Frant,
beginning at 2000.
As always, any members of the Society are very welcome to come along and join us for a chat and a drink. The meetings usually last about an hour.
SEPTEMBER
MEETING
After
briefly talking about our own Sun and describing it as a "G" type
dwarf star, Konrad Malin-Smith compared it with a White Dwarf whose mass is
rather similar to our Sun's mass but whose size is about that of the Earth.
He
pointed out the position of White Dwarfs on the Hertzsprung-Russell diagram
where they leave the main sequence stars because of their much higher
temperature and low luminosity. To
illustrate this, Konrad projected a photograph of Sirius, the Dog Star in Canis
Major. This is the brightest star in the night sky at magnitude
-1.47 although its position varies very slightly over time. Then we were shown a highly magnified photograph of the same
star and barely visible was a companion, Sirius B affectionately known as
"The Pup", with a magnitude of +8.44.
Over
150 years ago a German mathematician, Frederick Bessel used the orbit of the
Earth to measure the parallax of the star Cygni 61 and so was able to measure
its distance. He used his method of
precise measurement in 1844 to detect the slight movement of Sirius A and this
led to the discovery by Alvan Clark of Sirius B in 1862.
Later this faint companion was identified as the first White Dwarf to be
discovered.
Konrad
then used the white star Rigel, the foot of Orion to locate 40 Eridani, also
known as Omicron Eridani. This is a
warm star with a White Dwarf orbiting about it in 248 years and at a distance
similar to that of Uranus from the Sun. In
1925, Arthur Eddington devised a method of blanking out the light from the star
to actually reveal the White Dwarf.
It
was Eddington who suggested that the spectrum of the white dwarf had been
red-shifted by gravity. Up until now red shift had been associated only with
receding stars but Albert Einstein developed a new theory.
The density of the white dwarf is calculated to be about 20 tons per
cubic inch and Einstein proposed that the gravity also causes the red shift,
known as the Einstein Shift.
With
the use of an overhead projector, Konrad explained that Electron Degeneracy
Pressure is a force such that two electrons cannot occupy the same quantum state
at the same time in the same area. This
force sets a limit to the amount of matter that can be squeezed together. This factor is important because it prevents the White Dwarf
collapsing further.
An
interesting fact that Konrad mentioned is that White Dwarfs have been around
from the very early stages of the Universe and none have yet died completely.
We
looked at the precursor to the White Dwarf in the form of a helical nebula where
hydrogen had been thrown off a massive star and looking rather like a circle of
pink cloud when viewed end-on. We
see a number of such rings because of our relative position as viewed from the
Earth.
At
the centre of this ring of gas is a central star that has shed its outer layer
of hydrogen and now has a temperature of 100,000 degrees and is producing heavy
radiation. This star will
eventually become a white dwarf.
The
example we looked at was in M4 close to Antares.
M4 is a cluster consisting of about 150,000 stars with 40,000 very old
white dwarf stars. Because they are
in a cluster they are all at the same distance from us and thus can be compared
with each other with this in mind.
One
night whilst observing Cygnus, Konrad saw a bright object, which was a Nova just
occurring and fortunately had his camera with him at the time.
This Nova was visible for the next 80 days.
Konrad
now explained how a Nova occurs when a White Dwarf orbits a red star, sucking
off the hydrogen, forming a disk before falling into the dwarf.
The example of a pair we were shown orbited each other in just 41/2 days
with a distance between the pair of just a few thousand miles.
When the layer of hydrogen on the dwarf reaches about 10 miles in
thickness, the layer becomes unstable and is blown off, resulting in a nuclear
reaction, which results in the brightening we see as a Nova.
Finally
Konrad talked of an event witnessed in the central bright area of M31, the
Andromeda Galaxy in 1865 when an obvious bright spot was observed.
At first astronomers thought it was something within our own galaxy, but
then it was realised that it was in fact a Super Nova taking place 2.9 million
light years away!
Once again Konrad Malin-Smith had left us with plenty to think about but had presented his subject in a clear but entertaining way. His equations can be found here and here.
OCTOBER
MEETING
The
next Society meeting is on Wednesday 18th October 2006 when Jerry Workman will
be paying us another visit and this time talks about the latest news from Mars.
As usual, the meeting will be held in the Upper Room of the Methodist Church, the High Street, Wadhurst, opposite Uplands College. The meeting commences at 1930.
FUTURE MEETINGS
Wednesday 15th November 2006. David Rooney, who is the Deputy Horologist at Greenwich Museum, is to give us a talk called "A Brief History of GMT". The new Time Galleries opened last February as part of the improvements to the Museum.
Wednesday
13th December 2006. Note that
this will be second Wednesday of the month.
Phil Berry, a member of the Society is giving a talk he calls "The
Trials and Tribulations of an Amateur Astronomer".
This will be followed by mince pies and beverages!
Wednesday
17th January 2006 The talk is
given by Bob Seaney, one of our Society members and the title of his talk is
"The Astronomical Art of Chesley Bonestell - Destination Moon (1953)
Highlights"
This will be followed by the Society's Annual General Meeting which takes place in January for the first time.
OCTOBER
NIGHT SKY
The
nights are getting longer now and early on the morning of Sunday 22nd of October
the clocks go back giving the astronomer a whole hour earlier to begin
observing, although the only notable planet at present is Saturn, which can be
seen just before sunrise. Because
of our relative positions in the Earth's and Saturn's orbits, we are now looking
down onto the northern latitudes of the planet, which we haven't been able to do
for some years. The rings are now
beginning to close as we view them but they don't completely close until early
in 2009.
Venus,
Mars and Mercury are hidden behind the Sun this month and Jupiter is now lost in
the light of the evening sky.
Neptune
now has a magnitude of +7.9 and is amongst the stars of Capricornus, about a
degree northwest of Iota Capricornus, but will need a pair of good binoculars to
see it.
Uranus
is almost due south in Aquarius late evening during the month of October and is
half a degree beneath Lorenzin Lambda (magnitude +3.7) at an altitude above the
horizon of about 30 degrees. Uranus
has an apparent magnitude of +5.8 at present, although right at the beginning of
the month, the moon passes within a degree on the 5th, which will obscure it.
I
see Pluto is now officially identified as a "Dwarf Planet" along with
2003 UB313, the recently discovered "object".
Towards
the end of the month, the Orionid meteor shower takes place, with a peak around
the 20th to 22nd of October as we pass through the debris of the tail of one of
Halley's comets. At this time of
year the Earth is moving in a direction close to the position of Betelgeuse in
the constellation of Orion. The
"Radiant", or apparent origin of the meteors is just above Betelgeuse.
They are fairly bright and there can be up to 15 trails an hour at their
peak.
Many years ago I charted the Orionids, placing the trails as accurately as I could on a copy of a star chart, and most of the meteors obviously radiated from the same origin close to Betelgeuse. I observed them for two hours and had some help, but at the time I thought it was all worthwhile.
REFRACTING
TELESCOPE FOR SALE
Ian
Reeves' refracting telescope is for sale for £150.
Ian brought it to several Society meetings and it is certainly more than
ideal for anyone starting off in astronomy particularly as the nights are
drawing out now and the whole of the winter constellations will soon be there
such as the winter constellation of Orion and its many interesting treasures.
The
telescope is a Konus 120 mm achromatic refracting instrument with a manual
equatorial mount and tripod. Amongst
the accessories are a star-diagonal and a number of eyepieces.
The Instrument comes in its own substantial travelling case.
In
the past, experienced members of the Society referred to the optics as
exceptionally good.
Further information can be obtained from Mavis, Ian Reeves' widow, on 01892 784255 or from Phil Berry on 01892 783544.
NASA SPACE PLACE
Snowstorm
on Pluto
by
Dr. Tony Phillips
There's
a nip in the air. Outside it's beginning to snow, the first fall of winter.
A few delicate flakes tumble from the sky, innocently enough, but this is
no mere flurry.
Soon
the air is choked with snow, falling so fast and hard it seems to pull the sky
down with it. Indeed, that's what happens. Weeks later when the storm finally
ends the entire atmosphere is gone. Every
molecule of air on your planet has frozen and fallen to the ground.
That
was a snowstorm - on Pluto.
Once
every year on Pluto (1 Pluto-year = 248 Earth-years), around the beginning of
winter, it gets so cold that the atmosphere freezes. Air on Pluto is made mainly
of nitrogen with a smattering of methane and other compounds.
When the temperature dips to about 32 K (-240 C), these molecules
crystallize and the atmosphere comes down.
"The
collapse can happen quite suddenly," says Alan Stern of the Southwest
Research Institute. "Snow begins to fall, the surface reflects more
sunlight, forcing quicker cooling, accelerating the snowfall. It can all be over
in a few weeks or months."
Researchers
believe this will happen sometime during the next 10 to 20 years.
Pluto is receding from the warmth of the Sun, carried outward by its 25%
elliptical orbit. Winter is coming.
So
is New Horizons. Stern is lead
scientist for the robotic probe, which left Earth in January bound for Pluto. In 2015 New Horizons will become the first spacecraft to
visit that distant planet (Dwarf Planet - Ed).
The question is, will it arrive before the snowstorm?
"We
hope so," says Stern. The spacecraft is bristling with instruments designed
to study Pluto's atmosphere and surface. "But
we can't study the atmosphere if it's not there." Furthermore, a layer of
snow on the ground ("probably a few centimetres deep," estimates
Stern) could hide the underlying surface from New Horizon's remote sensors.
Stern
isn't too concerned: "Pluto's atmosphere was discovered in 1988 when
astronomers watched the planet pass in front of a distant star-a stellar
occultation." The star, instead of vanishing abruptly at Pluto's solid
edge, faded slowly. Pluto was
"fuzzy;" it had air. "Similar
occultations observed since then (most recently in 2002) reveal no sign of
[impending] collapse," says Stern. On
the contrary, the atmosphere appears to be expanding, puffed up by lingering
heat from Pluto's waning summer.
Nevertheless,
it's a good thing New Horizons is fast, hurtling toward Pluto at 30,000 mph.
Winter. New Horizons. Only one can be first. The
race is on....
Find
out more about the New Horizons mission at http://pluto.jhuapl.edu.
Kids can learn amazing facts about Pluto at http://spaceplace.nasa.gov/en/kids/pluto.
This article was provided by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
Chairman
Tim Bance 01732 832745
Phil Berry 01892 783544 phil.berry@tiscali.co.uk
Treasurer
Mike Wyles 01892 542863
Publicity &
Website Michael Harte 01892 783292
Newsletter Editor Geoff Rathbone
01959 524727
Any material for inclusion in the November Newsletter should be with the Editor by October 28th 2006
