http://www.skyandtelescope.com.au 49by Alan Plummer VARIABLE STARSis sufficient to find U Her. However,
to participate fully I suggest you read
the AAVO Visual Observers Manual,
and jump in. The astronomical world
awaits!■ ALAN PLUMMER observes from the
Blue Mountains west of Sydney, and
can be contacted at alan.plummer@
variablestarssouth.orgLegacy of a long-period variable
The history of U Herculis stretches back more than 150 years.
T
hey say it’s a small world, and it
seems that in astronomy circles
it has been for some time, as
there has always been a two-way street
between observers and researchers.
The American Association of Variable
Star Observers (AAVSO), for instance,
is an interface between observers and
the wider astronomical community. To
illustrate: the star U Herculis’ variability
was first documented in 1860 by Karl
Ludwig Hencke, a Prussian postal clerk.
His interest in astronomy had led him
into contact with professionals such as
Encke, von Fraunhofer and Argelander
— famous names all. So, U Her it was a
case of a discovery by an amateur who
was motivated by professionals.
The U Her data set proper began in
1863, with the work of professional
astronomers in England and Germany.
And in the USA in 1906, the director
of the Harvard College Observatory,
Edward Pickering, actively enlisted
amateurs from around the world to
monitor variable stars, leading to
today’s wonderful AAVSO database.
U Her is an ideal subject for those
with a good northern outlook. It is a
long-period variable (LPV) with a visual
magnitude range of 6.4 to 13.4 overa period of 404 days. With predicted
maximum light coming up on July 12,
it’s a great target for 50-mm binoculars.
The AAVSO has it in its LPV Legacy
list — selected stars that have long-term
data sets and whose light curves are
expected to be scientifically useful for
decades to come.
The finder chart here, along with
the all sky map in the centre pages,W U Herculis is
located at 16h
25m 47.47s,
+18° 53' 32.9"
(epoch J2000).
This chart
(courtesy of
the AAVSO) is
approximately
4 degrees wide
and has visual
magnitudes
shown with
decimal points
omitted to avoid
confusion with
faint stars —
so 60 denotes a
magnitude 6.0
star.