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October 15th
“Hun:ng for super-Earths with the
Next Genera:on Transit Survey”
(Dr Peter Wheatley)
November 5th
Club Night
November 19th
“tba”
(Dr Nigel Bannister)
December 3rd
“Cosmic Sirens: The Dawn of
Gravita:onal Astronomy”
(Prof Sathyaprakash)
MEETINGS: 7:30 for 8pm
Club Nights include a variety of
ac:vi:es, including: observing topics,
monthly sky notes, mul:media,
astronomical chat and observing the
night sky (weather permi?ng).
March 19th
“The Universe in a Nutshell”
a video by Prof Michio Kaku
April 2nd
Club Night
April 16th
“The Sun Revealed”
(Dr Johanna Jarvis)
May 7th
Club Night: AGM
May 21st
“The Search for the Higgs Boson”
(Dr Sinead Farrington)
June 4th
Club Night
June 18th
“Astrobiology:
The Hunt for Life Beyond Earth”
(Dr Lewis Dartnell)
July 2nd
Club Night
July 16th
“Percival Lowell
and the Canals of Mars”
(Dr Ann Bonell)
August 6th
Club Night
August 20th
“The Northern Lights”
David Phillips
September 3rd
Club Night
September 17th
tba
October 1st
Club Night
www.astro.org.uk
MARCH 2013
something wrong with our instruments. We
checked everything, but there was nothing
wrong with them. The third belt persisted
beau:fully, day aNer day, week aNer week, for
four weeks."
Incorpora:ng this new configura:on into their
models of the radia:on belts offers scien:sts
new clues to what causes the changing shapes
of the belts – a region that can some:mes
swell drama:cally in response to incoming
energy from the sun, impac:ng satellites and
spacecraN or pose poten:al threats to
manned space flight.
The radia:on belts, or Van Allen belts, were
discovered with the very first launches of
satellites in 1958 by James Van Allen.
Subsequent missions have observed parts of
Earth’s Third Radiation Belt
the belts – including SAMPEX, which observed
the belts from below – but what causes such
ANer most NASA science spacecraN launches,
dynamic varia:on in the belts has remained
researchers wait pa:ently for months as
something of a mystery. Indeed, seemingly
instruments on board are turned on one at a
similar storms from the sun have at :mes
:me, slowly ramped up to full power, and
caused completely different effects in the
tested to make sure they work at full capacity.
belts, or have some:mes led to no change at
It's a rite of passage for any new satellite in
all.
space, and such a schedule was
in place for the Van Allen Probes
when they launched on August
30, 2012 to study two giant belts
of radia:on that surround Earth.
But a group of scien:sts on the
mission made a case for
changing the plan. They asked
that the Rela:vis:c Electron
Proton Telescope (REPT) be
turned on early – just three days
aNer launch -- in order that its
observa:ons would overlap with
another mission called SAMPEX
(Solar, Anomalous, and
Magnetospheric Par:cle
Explorer), that was soon going to
de-orbit and re-enter Earth's
atmosphere.
It was a lucky decision. Shortly
before REPT turned on, solar
ac:vity on the Sun had sent
energy toward Earth that caused
the radia:on belts to swell. The
REPT instrument worked well
from the moment it was turned
on September 1st. It made
The radia on is shown here in yellow, with green represen ng the
spaces between the belts.
observa:ons of these new
par:cles trapped in the belts,
The Van Allen Probes consist of two iden:cal
recording their high energies, and the belts'
spacecraN with a mission to map out this
increased size.
region with exquisite detail, cataloguing a
Then something happened no one had ever
wide range of energies and par:cles, and
seen before: the par:cles se4led into a new
tracking the zoo of magne:c waves that pulse
configura:on, showing an extra, third belt
through the area, some:mes kicking par:cles
extending out into space. Within mere days of up to such frenzied speeds that they escape
launch, the Van Allen Probes showed scien:sts the belts altogether.
something that would require rewri:ng
"We've had a long run of data from missions
textbooks.
like SAMPEX," says Daniel Baker, who is the
"By the fiNh day REPT was on, we could plot
principal inves:gator for REPT. "But we've
out our observa:ons and watch the forma:on never been in the very throat of the
of a third radia:on belt," says Shri Kanekal, the accelerator opera:ng a few hundred miles
deputy mission scien:st for the Van Allen
above our head, speeding these par:cles up to
Probes. "We started wondering if there was
incredible veloci:es."
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In its first six months in orbit, the instruments on the Van Allen Probes
have worked excep:onally well and scien:sts are excited about a flood
of observa:ons coming in with unprecedented clarity. This is the first
:me scien:sts have been able to gather such a complete set of data
about the belts, with the added bonus of watching from two separate
spacecraN that can be4er show how events sweep across the area.
Baker likes to compare the radia:on belts to the par:cle storage rings
in a par:cle physics accelerator. In accelerators, magne:c fields are
used to hold the par:cles orbi:ng in a circle, while energy waves are
used to buffet the par:cles up to ever faster speeds. In such
accelerators, everything must be carefully tuned to the size and shape
of that ring, and the characteris:cs of those par:cles. The Van Allen
Belts depend on similar fine-tuning. Given that scien:sts see the rings
only in certain places and at certain :mes, they can narrow down just
which par:cles and waves must be causing that geometry. Every new
set of observa:ons helps narrow the field even further.
Brecon Beacons: Interna/onal Dark Sky Reserve
The Brecon Beacons Na:onal
Park has been granted the
pres:gious status of an
interna:onal dark sky reserve.
This makes the site Wales’ 1st
dark sky reserve and only the
5th such site worldwide.
www.breconbeacons.org
Measuring the Universe
ANer nearly a decade of careful observa:ons an interna:onal
team of astronomers has measured the distance to our
neighbouring galaxy, the Large Magellanic Cloud, more
accurately than ever before.
Astronomers survey the scale of the Universe by first measuring
the distances to close-by objects and then using them as
standard candles to pin down distances further and further out
into the cosmos. Up to now finding an accurate distance to the
Large Magellanic Cloud (LMC), one of the nearest galaxies to the
Milky Way, has proved elusive. As stars in this galaxy are used to
fix the distance scale for more remote galaxies, it is crucially
important.
But careful observa:ons of a rare class of double star have now
allowed a team of astronomers to deduce a much more precise
value for the LMC distance: 163, 000 light-years.
On August 31st last year a giant prominence on the sun erupted, sending out
par cles and a shock wave that travelled near Earth. This event may have been
one of the causes of a third radia on belt that appeared around Earth a few
days later, a phenomenon that was observed for the very first me by the newly
-launched Van Allen Probes.
Scien:sts already have theories about just what kind of waves sweep
out par:cles in the "slot" region between the first two belts. Now they
must devise models to find which waves have the right characteris:cs
to sweep out par:cles in the new slot region as well.
Another tantalizing observa:on to explore lies in tracking the causes of
the slot region back even
further: on August 31, 2012, a
long filament of solar material
that had been hovering in the
sun's atmosphere erupted out
into space. Baker says that this
might have caused the shock
wave that led to the forma:on
of the third ring a few days later.
In addi:on, the new belt was
virtually annihilated four weeks
aNer it appeared by another
powerful interplanetary shock
wave from the sun. Being able to
watch such an event in ac:on
provides even more material for
theories about the Van Allen
belts.
Despite the 55 years since the
radia:on belts were first
discovered, there is much leN to
inves:gate and explain, and
within just a few days of launch
the Van Allen Probes showed
that the belts are s:ll capable of
surprises.
Holding aloft a model of Explorer 1, the
spacecraft that discovered the Van Allen
Belts are (L to R): William H. Pickering of
the JPL; James A. Van Allen, and Wernher
von Braun. The rocket in front of von
Braun is the Juno 1 which launched
Explorer 1 and its multi-stage launch
system was designed by von Braun.
Explorer 1 ceased transmission
of data on May 23, 1958 when its ba4eries died, but remained in orbit
for more than 12 years. It made a fiery re-entry over the Pacific Ocean
on March 31, 1970.
The improvement in the measurement of the distance to the
Large Magellanic Cloud also gives be4er distances for many
Cepheid variable stars . These bright pulsa:ng stars are used as
standard candles to measure distances out to more remote
galaxies and to determine the expansion rate of the Universe —
the Hubble Constant. This in turn is the basis for surveying the
Universe out to the most distant galaxies that can be seen with
current telescopes. So the more accurate distance to the Large
Magellanic Cloud immediately reduces the inaccuracy in current
measurements of cosmological distances.
The astronomers worked out the distance to the Large
Magellanic Cloud by observing rare close pairs of stars, known as
eclipsing binaries . As these stars orbit each other they pass in
front of each other. When this happens, as seen from Earth, the
total brightness drops, both when one star passes in front of the
other and, by a different amount, when it passes behind.
By tracking these changes in brightness very carefully, and also
measuring the stars’ orbital speeds, it is possible to work out
how big the stars are, their
masses and other informa:on
about their orbits. When this is
Contacts
combined with careful
Ian Galletly
measurements of the total
(Ac:ng Chair)
brightness and colours of the
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stars remarkably accurate
distances can be found.
John Waller
This method has been used
(Membership & Treasurer)
before, but with hot stars.
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However, certain assump:ons
have to be made in this case
Jim Dean
and such distances are not as
(Events Secretary)
accurate as is desirable. But
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now, for the first :me, eight
extremely rare eclipsing
Julia Waller
binaries where both stars are
(Newsle4er Editor & Librarian)
cooler red giant stars have
12 Badger Road
been iden:fied. These stars
Coventry
have been studied very
CV3 2PU
carefully and yield much more
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accurate distance values —
accurate to about 2%.