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The SOCIETY for POPULAR ASTRONOMY
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Electronic News Bulletin No. 240 2008 March 16
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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
using our secure site and can take credit and debit cards. You can
join or renew via a secure server or just see how much we have to
offer by visiting http://popastro.c.topica.com/maacvtjaa8Qpbbc8AEAb/



STEVE EVANS (1953-2008)
By Alastair McBeath, SPA Meteor Section Director

As some ENB readers will be aware, long-time SPA Meteor Section
observer Steve Evans died unexpectedly on March 7th, from a massive
heart attack. Steve carried out much solo and double-station
photographic meteor work in the 1980s and 90s, more recently turning
to a variety of automated video meteor systems, operated from his
Gloucestershire home, and was a regular contributor to the International
Meteor Organization's Video Commission monthly reports, the UK's
sole such representative. He approached his meteor activities with
enthusiasm, knowledge and dedication. He particularly enjoyed
participating in several amateur-professional expeditions with
colleagues from the Czech Republic and the Netherlands in 2000,
2001 and 2002, to obtain high-quality triangulated images of meteors
during the strong to storm Leonid returns in those years. He always felt
the highlight of those was seeing the 2001 storm from the wonderful
dark skies of Arizona, as he said "a truly once in a lifetime experience."
His dedication was shown by his computer reduction of the more than
5000 meteor trails recorded by his own video system during that same
storm, which took until 2003 to finish, data that subsequently featured
in professional science journal papers in conjunction with those of his
co-observers.

The global meteor community is a relatively small one, so the death of
any of its members tends to be keenly felt. Steve's tragically early
passing has been felt more than most, as has been clear from the
numerous comments I've received from friends and colleagues,
beginning immediately after the event was announced. It is equally clear
that he has been and will continue to be greatly missed. Our heartfelt
sympathies go to his family, to whom I have sent a message of sincerest
condolence on behalf of the Section.


FIREBALLS UPDATE
By Alastair McBeath, SPA Meteor Section Director

Since ENB 239 ( http://tinyurl.com/2nfomp), further fireball reports have
come through to the Section, with a possible second observation of the
February 8-9, magnitude -6 fireball imaged from Holland at ~21:46 UT,
made from Norfolk. The sightings tally for the brilliant ~20:55 UT meteor
on February 11-12 has risen to twenty now too. Two fresh events have
been reported:

Date Time (UT) Magnitude and Notes Observed from
08/02/27-28 22:50 -6/-8 Oxfordshire
08/03/4-5 00:40 Very bright Northumberland

Fireball observations (a fireball is any meteor that reaches at least
magnitude -3) made from Britain or points adjacent are always
welcomed by the SPA Meteor Section, whether of the above objects or
not. Details to send are outlined on the "Fireball Observing" page of the
SPA website, at: http://tinyurl.com/l62fh .


POSSIBLE METEORITIC FIREBALL OVER OREGON
By Alastair McBeath, SPA Meteor Section Director

Accidentally omitted from last time's fireballs round-up, but as regular
followers of the SPA Forums will be aware, a major fireball occurred
over the north-western USA at 13:30:59 UT on February 18-19 this year.
It was partly imaged on an automated video system by Section
correspondent and dedicated radio meteor observer Jeff Brower, from
British Columbia, Canada, as it passed below his horizon. It was also
videoed from Portland, Oregon and other places. A violent fragmentation
event, or possibly two, caused sonic booms which rattled windows and
woke people up (it happened around 5:30 a.m. local time) which were
recorded by seismometers. The meteor was seen from California,
Oregon, Idaho, Montana, Washington and British Columbia, following a
generally northwest to southeast trajectory. Several significant fragments
were seen after the break-up, and it is possible meteorites landed as a
result. Estimates suggest these may have come down within 15 km or
so of Pendleton in northeast Oregon, but nothing had been reported as
found up to March 12. Further details can be traced via:
http://tinyurl.com/3avdca on the SPA's Observing Forum.


PERU IMPACT UPDATE
By Alastair McBeath, SPA Meteor Section Director

We featured the meteoritic impact event at Carancas in Peru, near the
Bolivian border, on 2007 September 15, back in ENB 229
( http://tinyurl.com/2wktp3), but occasional notes have surfaced in places
at times since, including some that continued to speculate that the event
was not really meteoritic, even after some genuine meteorite fragments
from the site had been examined (suggesting that perhaps a previously-
fallen meteorite could have been excavated from below the surface
during a terrestrially-created impact, for instance). Fresh news came on
March 12, when two investigators presented findings to the Lunar and
Planetary Science Conference in Houston, Texas. One, Professor Peter
Schultz from Brown University, Rhode Island, suggested that the impact
may have happened at a significantly higher velocity than expected,
around 6.5 km/sec (pre-atmospheric meteor velocities begin at
11 km/sec and go up from there to 72 km/sec). This may have held the
pieces of the Carancas meteorite together within the shockwave-front
of the fireball until after it landed. Typically, past witnessed stony
meteorite falls have produced a scatter of small fragments, sometimes
several thousand, over an area of at least several square kilometres,
though smaller, single, falls have happened too, the object(s) dropping
at near-free-fall speeds. The other idea, proposed by Dr Thomas
Kenkmann from Humboldt University in Berlin, was that the event
happened at low velocity and with a slanting approach angle, again
helping the pieces stay relatively close together after the impact.
Unsurprisingly, given the general caution that has surrounded many of
the reports on this event, neither explanation has convinced the whole
meteorite science community so far. More details can be sourced
through the SPA's General Chat Forum topic at: http://tinyurl.com/2n2dkj.


EARTH'S ROTATION MAY ACCOUNT FOR SPACECRAFT ANOMALY
New Scientist

A phenomenon causing small, unexpected deviations in robotic
spacecraft trajectories near the Earth may be a step closer to an
explanation. Scientists have come up with a mathematical formula that
successfully reproduces all the known occurrences of the effect, and
they suspect that the Earth's rotation may somehow be to blame. They
first noticed something amiss in the motion of spacecraft passing near
the Earth when the Galileo spacecraft flew by our planet in 1990 to
get a boost from the planet's gravity. The fly-by boosted Galileo's
speed by several kilometres per second, as expected, but it was found
that the boost was very slightly larger than expected, by about 4
millimetres per second. Although the amount is very small, it is more
than 10 times larger than can be accounted for by errors in tracking
and other known influences, such as gas escaping from the spacecraft.

The anomaly also cropped up in a Galileo fly-by in 1992, as well as in
a 1998 Earth fly-by of the Near-Earth-Asteroid Rendezvous (NEAR)
mission. The anomaly received more attention in 2006, when the
possibility was suggested of a link with a similar puzzle called the
Pioneer anomaly. The Pioneer anomaly refers to the observation that
the Pioneer 10 and 11 spacecraft are both slowing down more than
expected as they fly away from the Sun in opposite directions. Now,
scientists have stumbled on a formula that accurately reproduces all
five instances where a fly-by anomaly has been observed so far. The
formula involves the angle that the spacecraft's incoming and outgoing
trajectories make with respect to Earth's equator. For fly-bys where
the angle is very different for the incoming and outgoing parts of the
trajectory, such as the 1998 NEAR fly-by, both the formula and the
observations give a large anomaly, but where incoming and outgoing
angles are similar, the anomaly is very small, and in some cases too
small to be detected. Both the 2005 fly-by of the Messenger
spacecraft en route to Mercury and the 2007 passage of Rosetta on its
way to a comet had very similar incoming and outgoing angles, and
neither showed a detectable anomaly. Although the team has been
unable to come up with an underlying physical explanation, the formula
suggests some sort of connection to the Earth's rotation.


SATURN'S RHEA MAY HAVE RINGS
NASA

It has been (seemingly belatedly) announced that, on a close fly-by of
Saturn's second-largest moon, Rhea, in 2005 November, the Cassini
spacecraft found evidence of material forming a disc or ring around
it. The existence of some debris was expected because a rain of dust
constantly hits Saturn's moons, including Rhea, knocking particles
into space around them. Oblique evidence for a debris disc, possibly
consisting of particles ranging in size from pebbles to boulders, in
addition to a tenuous dust cloud, came from a gradual drop on either
side of Rhea in the number of electrons detected by Cassini's
instruments. One possible explanation for a disc is as a remnant from
an asteroid or comet collision in the distant past. Rhea is roughly
750 km in radius; the dust cloud may extend to a radius of 5,900 km.
Models show that Rhea's gravity field, in combination with its orbit
around Saturn, could maintain a disc in place for a very long time.


WATER FOUND FLOWING ON MARS?
University of Arizona

Liquid water has, after all, not been found on the Martian surface
within the last decade. A new finding rejects the 2006 report that
the bright spots in some Martian gullies indicated that liquid water
had flowed down those gullies since 1999. Astronomers used topo-
graphic data derived from images obtained by the Mars Reconnaissance
Orbiter. They applied some basic physics to see how a flow of liquid
water would look on comparison with an avalanche of dry granular
debris such as sand and gravel; the latter matches their calculations
much better.


GRAPHITE COULD EXPLAIN SUPERNOVA DIMNESS
Carnegie Institution

Interstellar space may be strewn with tiny whiskers of carbon, dimming
the light of far-away objects. That suggestion could demolish the
'dark energy' hypothesis, proposed a decade ago in part to explain the
unexpected dimness of distant Type-1a supernovae, which are among the
brightest objects in the Universe and are used as 'standard candles'
to gauge cosmological distances. In the late 1990s some astronomers
noticed that some seemed too dim -- too far away -- to be explained by
conventional theories of the Universe's expansion. That led to the
hypothesis that the expansion was accelerating, and theoreticians said
that it must be being pushed along by something that they called dark
energy.

In the current study, astronomers of the Carnegie Institution's
Geophysical Laboratory report the discovery of 'graphite whiskers' --
a form of carbon in minerals within meteorites dating from the
formation of the Solar System. The whiskers may have been produced
from carbon-rich gas at high temperatures and were found within
features called calcium-aluminium inclusions, which at around 4.5
billion years old are the oldest known solids in our Solar System.
When the Sun was young, the solar wind was very strong, so graphite
whiskers formed near the Sun could have been blown into interstellar
space, and the same could have happened around other young stars as
well. Graphite whiskers might also be produced and dispersed into
space by supernovae explosions. A thin interstellar haze of them
would dim the light of distant objects, perhaps especially in the near
infrared, where the dimming of light from Type_1a supernovae was the
thing that first (mis?)led researchers into thinking that the
Universal expansion was accelerating.


ALPHA CENTAURI B
Astronomy

Certain University of California astronomers say that terrestrial-type
planets could exist around the star Alpha Centauri B and be orbiting
at a distance such that liquid water could exist on a planet's
surface. Of course the same thing could be said about almost any
star, but the spokesmen say that a number of factors converge to
make Alpha Centauri B a good candidate for searching for terrestrial
planets. The Doppler detection method, which has revealed the
majority of the 228 known extra-solar planets, measures wavelength
shifts in the light from a star to detect the tiny wobble induced by
the gravity of an orbiting planet. Factors that favour the use of
that technique for Alpha Cen B include the brightness of the star and
its position in the sky, which gives it a long period of observability
each year from the Southern Hemisphere.

Detecting planets the mass of the Earth is challenging, however,
because they induce a only very small wobbles in their host stars.
The Earth, for example, moves the Sun at a rate of only 9 cm/s.
Moreover, a star has not got a solid surface whose own velocity is
well defined, but consists of gases in convective motion at velocities
thousands of times larger than the quantity of interest, so its
measured mean velocity cannot be expected to be stable to an
indefinitely high accuracy. All the same, the optimists in California
say that five years of observations with a dedicated telescope would
enable detection of an Earth-like planet around Alpha Cen B, if one
existed. Astronomers from San Francisco State University are already
monitoring Alpha Cen A and B with the 1.5-m telescope at Cerro Tololo
in Chile.


NEUTRON-STAR MISSING LINK?
NASA-GSFC

Observations from the Rossi X-ray Timing Explorer (RXTE) have revealed
that the youngest known pulsing neutron star occasionally emits
powerful bursts of X-rays, which are making astronomers re-think the
life-cycle of neutron stars. Most known neutron stars are 'pulsars'
that emit regular pulsations that are powered by rapid spins; nearly
1,800 are known in our galaxy. Pulsars have incredibly strong
magnetic fields by Earthly standards, but a dozen of them -- slow
rotators known as magnetars -- actually derive their energy from
incredibly powerful magnetic fields, the strongest known in the
Universe. The fields can stress the neutron star's solid crust past
the breaking point, triggering starquakes that snap magnetic-field
lines, producing violent and sporadic X-ray bursts.

Astronomers would like to know if magnetars represent a rare class of
pulsars, or if some or all pulsars go through a magnetar phase during
their life-cycles. A clue has come from examination of archival RXTE
data of a young neutron star, known as PSR J1846-0258, in the
constellation Aquila. It had been classified as a normal pulsar
because of its fast spin (3.1 times per second) and pulsar-like
spectrum, but RXTE caught five magnetar-like X-ray bursts in 2006.
Although none of the events lasted longer than 0.14 second, they all
had a momentary luminosity of at least 75,000 Suns. Never before has
a normal pulsar been observed to produce magnetar bursts, and young,
fast-spinning pulsars were not thought to have enough magnetic energy
to generate such powerful bursts. However, the Chandra X-ray
Observatory observed the neutron star in 2000, and again in 2006
around the time of the bursts, and showed that the object had
brightened then in X-rays, confirming that the bursts were indeed from
the pulsar, and that its spectrum had changed to become more
magnetar-like.

PSR J1846 is believed to be very young for several reasons. First, it
is inside a supernova remnant,indicating that it has not had time to
move far from its birthplace. Secondly, from the rapidity with which
its spin rate is slowing down, it is calculated to be no older than
884 years. Magnetars are thought to be about 10,000 years old,
whereas most pulsars are thought to be considerably older. The fact
that PSR J1846's spin rate is slowing down relatively quickly also
means that its rotation is being braked by a magnetic field whose
implied intensity is stronger than the Earth's field by a factor of
the order of 10*12, but is nevertheless 10 to 100 times below typical
magnetar field strengths. PSR J1846's actual magnetic field could be
much stronger than the measured amount, so it is possible that many
young neutron stars classified as pulsars might actually be magnetars
in disguise, and that the true strength of their magnetic field only
reveals itself over thousands of years as they ramp up in activity.


NEW EVIDENCE OF EARLY UNIVERSE
NASA

NASA has just published five years of data collected by the Wilkinson
Microwave Anisotropy Probe (WMAP). WMAP measures a remnant of the
early Universe -- its oldest light. That light has been red-shifted
as the Universe has expanded, and is now seen as microwaves. WMAP's
accurate measurements of microwave patterns bear on some longstanding
questions about the Universe's age, composition and development. The
microwave radiation seen by WMAP, coming from when the Universe was
only about 380,000 years old, has been interpreted as showing that, at
the time, neutrinos made up 10% of the Universe, atoms 12%, dark
matter 63%, photons 15%, and 'dark energy' was negligible. WMAP data
suggest, with some confidence, the existence of a cosmic neutrino
background.

The hot and dense young Universe was a nuclear reactor that produced
helium. Theories based on the amount of helium seen today require
that a sea of neutrinos should have been present when the helium was
made. The new WMAP data agree with that requirement. WMAP data also
offer some insight into the end of the 'dark ages', when the first
generation of stars began to shine. The glow from those stars created
in the surrounding gas a thin fog of electrons that scatters
microwaves, in somewhat the same way as fog scatters light beams.
Astronomers now have evidence that the creation of the fog was a
drawn-out process, starting when the Universe was about 400 million
years old and lasting for half a billion years.


FIRST LIGHT WITH LARGE BINOCULAR TELESCOPE
University of Arizona

The Large Binocular Telescope has taken celestial images using its
twin, side-by-side, 8.4-m primary mirrors together, achieving first
'binocular' light (a single mirror was first operational in 2005).
It could be claimed now to be the world's most powerful telescope, as
it has a light-collecting area equivalent to a single 11.8-m surface
and will combine light to produce the image sharpness equivalent to a
single 22.8-m telescope. It is located on 10,480-foot Mount Graham in
southeastern Arizona.




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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