July
2008
Features
The latest in our series of articles
specially written for the Organ by astrophysicist, Professor
Michael Rowan-Robinson.
28.
Vega
Midsummer is quite a frustrating time for astronomy because
the nights are so short and never get totally dark, so we
can see only the brighter stars.
Almost overhead in the late evening is Vega, also known
as Alpha Lyrae, the brightest star in the constellation
of the Lyre, and the fifth brightest star in the sky. It
has a sharp blue-white glitter, which in a large telescope
becomes a vivid pool of blue light. It is twenty-seven light
years away, is nearly sixty times more luminous than the
Sun and is about three times as massive. Its diameter has
been measured by a special telescope at Narrabri, Australia,
an interferometer, which makes the light from different
parts of the star interfere together to make a fringe pattern
on the detector. It turns out to be about three times larger
than the Sun.
In 1983 the Infrared Astronomical Satellite (IRAS), a joint
US-Dutch-British mission on which I was a member of the
science team, made a remarkable discovery about Vega. The
IRAS calibration team, led by two Americans - George Aummann
and the late Fred Gillett - were trying to use Vega to calibrate
the IRAS infrared measurements. Vega has been used to define
the magnitude scale at different wavelengths or colours
for stars for well over a century. The IRAS team found that
Vega was behaving very strangely and was much brighter than
expected at infrared wavelengths. The reason turned out
to be that Vega is surrounded by a disk of dust particles,
probably a planetary system in formation. Many other examples
of these ‘dust debris disks’ have been found
around nearby stars and there is now a whole branch of astronomy
devoted to ‘proto-planetary disks’.
You should also notice two other bright stars overhead,
Deneb and Altair which, with Vega, make up the ‘summer
triangle’. Vega and Altair are on opposite sides of
the Milky Way, which begins to become prominent in the night
sky in July and August. The ancient Chinese astronomers
called Altair and Vega the Herd-boy and the Weaving-Girl.
The story was that they are separated by the Celestial River
of the Milky Way. Once a year the gods take pity on them
and they are allowed to meet when a bridge of birds temporarily
spans the River of Stars. The Pawnee Indians of Nebraska
call Vega the Black Star, which in the light of its dust
disk turns out to be rather an appropriate name.
Past Stars’n Tides articles can be found at http://astro.ic.ac.uk/~mrr/starsntides/
© Michael Rowan-Robinson 2008
 It's
the Wine
Talking
by Leslie
J. Brinton of 'In the Pink' 01986 872579WINE TALKING...
JULY 2008
The last weekend in September will again see the Aldeburgh
Food and Wine Festival installed at Snape Maltings –
last year, this was a smash-hit magnet for foodies and I
see no reason why this year’s should be different.
A week of events around Suffolk will precede this highlight
and details should be available as this July issue of the
Organ is published.
At last year’s fringe event at The Swan, we were
treated to a glass of Adnams Tour Du Prelat Rouge, a French
country wine of character, to accompany chef Ian Howell’s
rolled lamb creation; last month at Southwold’s Crown,
a trio of lamb chops on top of shredded lamb was handsomely
accompanied by a whole bottle of the same (we weren’t
driving this time) Rhône-type brew, assembled with
skill from the Grenache, Syrah, Morvèdre and Counoise
grapes. Decent value at £12.50 a bottle. Even better
at £6.50 from the shops.
Leslie J Brinton
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