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Electronic News Bulletin No. 238 2008 February 17

Here is the latest round-up of news from the Society for Popular
Astronomy. The SPA is Britain's liveliest astronomical society, with
members all over the world. We accept subscription payments online
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By Alastair McBeath, SPA Meteor Section Director

Trying not to be outdone by the clutch of fireball observations made
from multiple sites in mid-January, mid-February has produced a
further three such events so far, on February 11-12 around 20:55 UT
(magnitude -8/-12; 17 sightings from southern Wales, southern England
and an all-sky fireball patrol image by Klaas Jobse in Holland; more
sightings were made elsewhere in the Netherlands and Belgium) and
within 15 minutes of 22:45 UT (-7/-9?; five reports, all from
southeast England), plus at least one other bright meteor on February
12-13, sometime between 22:15 and 22:35 UT (three reports from
Flintshire, South Yorkshire and Bedfordshire). Several of the sighting
reports can be read at: on the SPA's
Observing Forum, including links to Klaas Jobse's wonderful
image. This ~20:55 UT event on February 11-12 may have started high
above the North Sea off East Anglia and ended somewhere over northern
England, on a roughly SE to NW trajectory, while the ~22:45 UT event
may have been off the south coast or over northern France. Assuming
all the February 12-13 sightings were of the same meteor (which is not
yet certain), that object may have been out over the North Sea
following a crudely south to north track.

Grateful thanks go to all the witnesses who have sent in details on
all these events so far. Observations of any fireballs seen from the
UK or close-by (a fireball is a meteor that reaches at least magnitude
-3), are always welcomed by the SPA Meteor Section, including further
sightings of any of the above. Advice and the details to send me are
outlined on the "Fireball Observing" page of the SPA website, at: .

By Alastair McBeath, SPA Meteor Section Director

Having carried out a detailed examination of the radio data across the
Quadrantid epoch in Radio Meteor Observation Bulletin 174 (January
2008; available at: ) in recent days, in general,
I concur with Assistant Meteor Director David Entwistle's preliminary
findings (presented in ENB 236, at: ), of a
roughly day-long period of increased activity from ~16h UT on January
3 to ~19h UT on January 4, and a weighted mean peak time within that
interval of 05h45m UT on January 4 (David's findings implied ~05h30m).
However, a closer inspection of when the peaks occurred could infer
two distinct phases of higher activity, one at some stage from roughly
23h-08h UT on January 3-4 ("peak [1]"), the second from ~10h-16h UT on
January 4 ("peak [2]"). Peak [1] seemed quite ill-defined, falling
between ~01h-07h UT perhaps, with a weighted mean peak time around
03h15m UT, albeit this was close to the mid-point of this interval at
03h30m. It was found by observers in the three main geographic regions
represented, Europe, North America and Japan. There was a suggestion
that the marginally best Quadrantid rates during the shower overall
happened around 04h-05h UT. Peak [2] saw the radiant below the horizon
for Japan, but the North American and European systems all found
something during it. The majority favoured the 10h-11h UT interval,
with a "tail" persisting till 13h or possibly 14h. This was probably
similar to, or only a little less, than the ~04h UT peak in
strength. It was particularly interesting that no radio results showed
a peak in rates during the 08h-10h UT spell, so there did seem to be a
distinct separation of the two possible peak phases. If this potential
"double-peak" feature was real (and it is always possible it may not
have been), the apparently stronger two maximum timings around 04h and
10h UT gave a separation of six hours, rather less than the 9h-12h
separation I have found before for maybe similar double maxima at some
of the recent visual-radio Quadrantid returns. That only part of peak
[2] coincided with the International Meteor Organization's preliminary
findings, for an ill-defined peak between 08h-11h UT on January 4 is
intriguing. The somewhat lower than normal Zenithal Hourly Rates (~80)
those visual results suggested may help account for the nature of the
radio results, however.


Saturn's A-ring and Enceladus are separated by 100,000 kilometres, yet
there is a physical connection between the two: observations made by
Cassini in 2004 are now found to indicate that Enceladus is actually
delivering a portion of its mass directly to the outer edge of the
A-ring. This is not the first surprising phenomenon associated with
the ice geysers of Enceladus. Earlier, the geysers were found to be
responsible for the content of the E-ring. Next, the whole magnetic
environment of Saturn was found to be affected by the material
erupting from Enceladus, which becomes plasma -- a gas of electrically
charged particles. Now, Cassini scientists find that the plasma,
which forms a doughnut-shaped cloud around Saturn, is being captured
by Saturn's A-ring.

Cassini made its closest pass over the A-ring when it first arrived at
Saturn in 2004. Hot spots on the inside surface of the plasma shell
-- the part colliding with the A-ring -- were emitting radio signals.
The signals behaved as a natural radio beacon, indicating the local
plasma density (the higher the frequency, the greater the density).
As Cassini approached the A-ring, the frequency dropped, implying that
the density of the plasma was decreasing because it was being absorbed
by the ring. As the spacecraft passed over the Cassini division in
the rings the frequency increased where plasma was leaking through the


Taking advantage of the presence of light echoes, astronomers have
measured accurately the distance of a Cepheid -- a class of variable
stars that constitutes one of the first steps in the cosmic distance
ladder. Cepheids are pulsating stars that have been used as distance
indicators for almost a hundred years. The new measurement is
important as, unlike most others, it is purely geometrical and does
not rely on hypotheses about the physics of the star itself.

The astronomers studied RS Puppis, a Cepheid bright enough to be
easily visible with binoculars. RS Pup varies in brightness by almost
a factor of five every 41.4 days. It is 10 times more massive than the
Sun, 200 times larger, and on average 15 000 times more luminous. It
is the only Cepheid known to be embedded in a large nebula, which is
made of very fine dust that reflects some of the light emitted by the
star. Because the luminosity of the star changes in a very
distinctive pattern, the presence of the nebula allows the astronomers
to see light echoes and use them to measure the distance of the star.

The light that travels from the star to a dust grain and then to the
telescope arrives a bit later than the light that comes directly from
the star, so any isolated dust blob in the nebula will show a 'light
echo' that varies in brightness in the same manner the Cepheid, but
after a delay. The astronomers monitored the variations of the
brightnesses of several blobs in the nebula, and thereby derived the
distance of each blob from the star -- it is simply the measured time
delay multiplied by the velocity of light. Knowing those distances
and the apparent separations on the sky between the star and each
blob, one can compute the distance of RS Pup. From the observations
of the echoes from several nebular features, the distance of RS Pup
was found to be 6500 +/- 90 light years.


Gravitational lensing by the massive cluster of galaxies known as
Abell 1689, about 2.2 billion light-years away, has enabled the Hubble
and Spitzer space telescopes to see a particularly remote galaxy that
would otherwise be too faint to detect. It may have a redshift of
more than 7.

There is a theory that in the early history of the Universe there were
'dark ages' that began about 400,000 years after the Big Bang, as
matter in the expanding Universe cooled and formed clouds of cold
hydrogen, which pervaded the whole of space like a thick fog. At some
point stars and galaxies started to form; their collective light
heated and cleared the fog of cold hydrogen, and ended the dark ages
about a billion years after the Big Bang. On that picture, the galaxy
that has recently been observed, and appears to be undergoing a spate
of star birth, would be one of the first to have formed at the end of
the dark era.

New Scientist

NASA has committed funding for a major new mission to the outer solar
system, to be launched in 2016 or 2017. Three concepts are in
competition for the mission. One would see a spacecraft in orbit
around Jupiter's moon Europa; it would use ground-penetrating radar to
try to measure the depth of the ocean suspected to lie beneath the
moon's icy surface. Another would see a lander, orbiter and
balloon-borne robot exploring Saturn's moon, Titan, while the third
would see a spacecraft fly by several of Jupiter's moons and go into
orbit around the largest, Ganymede.

Closer to home, a total of $344 million is earmarked for three new
robotic missions to be launched by 2014 to the Moon. They include an
orbiting spacecraft called the Lunar Atmosphere and Dust Environment
Explorer (LADEE) and two small landers to act as geophysical
monitoring stations on the Moon.

NASA's Earth-science division is to spend $910 million over the next
five years to develop new Earth-science spacecraft, including a
mission called SMAP to study soil moisture and one called ICESat II to
monitor changes in polar ice. For extra-solar planet research, NASA's
2009 budget request is a mixed bag. The Space Interferometry Mission
(SIM), designed to study light from planets circling other stars, has
been deleted from the 2009 budget, even though the US congress forced
NASA to reinstate the mission, which had been axed in the 2008 budget
request. On the other hand, NASA is providing $272 million over the
next five years towards a new medium-scale space mission to study
extra-solar planets, with a scaled-down version of SIM being
considered as one possibility. On the downside, NASA is largely
shutting down its New Millenium programme. The programme, which
received $26 million for 2008, was intended to prove cutting-edge
technologies for space missions, such as the ion engines used on the
Dawn spacecraft and artificial-intelligence software used on the Mars

Science Daily

NASA is asking the public to propose a name for its next mission.
The Gamma-ray Large-Area Space Telescope, otherwise known as GLAST,
is due to be launched on May 16 and is intended to observe energetic
phenomena related to such things as black holes, gamma-ray bursts, and
pulsars. NASA is looking for a name that might capture the excitement
of GLAST's mission and call attention to gamma-ray and high-energy
astronomy. It can't think of such a name itself, but it hopes that
someone will come up with one that is catchy, easy to say and will
help make the satellite and its mission a topic of dinner-table and
classroom discussion. The period for accepting names closes on March
31. Participants must include statements of not more than 25 words
about why their respective suggestions would suit the mission. To
avoid possible embarrassment, the winning name will not be announced
until after the telescope's launch. To submit a suggestion for the
mission name, visit:

Previous names have included the Galileo mission to Jupiter (named
after Italian astronomer Galileo Galilei), the Hubble space telescope
(US astronomer Edwin Hubble) and Messenger (said to stand for (MErcury
Surface, Space ENvironment, GEochemistry, and Ranging).

BBC News

British astronomers have been given a temporary reprieve over their
access to the two Gemini telescopes. Membership of the Gemini
consortium has been giving British astronomers direct access to two of
the biggest optical-infrared reflecting telescopes in the world. In
January, administrators announced their intention to withdraw the UK
from participation in Gemini, as they looked for means to plug an £80m
hole in their finances. That would have barred UK astronomers from
viewing the northern-hemisphere sky with telescopes of the largest
class. Upon reconsideration, it has now been decided that the UK will
continue to pay up for 2008, and will explore options for continued

By Peter Grego SPA Lunar Section Director

Join SPA Lunar Section Director Peter Grego at
for a LIVE WEBCAST of the total eclipse of the Moon on the night of
February 20/21 from 01:30 to 05:15 UT (if the event is clouded out a
real-time computer simulation of the eclipse will be broadcast).
Peter will be using a 200-mm SCT and a Philips ToUcam Pro, and the
view will take in the entire lunar disc.

The SPA Electronic News Bulletins are sponsored by the Open University.

Bulletin compiled by Clive Down

(c) 2008 the Society for Popular Astronomy

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