Download Last chance for a transit

News
Editorial
Last chance for
a transit
Sue Bowler,
Editor
Transit
June’s transit
of Venus
offers the last
opportunity
for a lifetime
to watch an
astronomical event that comes
around twice every century or
so. The transit is a relatively
simple geometrical coincidence
that is easy to understand, yet
has complex and significant
implications for historical and
current astronomy. Transits
allowed astronomers to take the
first steps on the cosmic distance
ladder, using parallax to measure
some of the dimensions of the
solar system. Historically, transits
of Venus have triggered scientific
thinking and launched scientific
expeditions that discovered far
more than astronomical data.
The transit of 1639 was observed
in Much Hoole, Lancashire, by
Jeremiah Horrocks, possibly from
the window of Carr House, as
Kevin Kilburn and Clive Elphick
discuss in this issue. And Captain
Cook’s expedition to observe
the 1769 transit resulted in the
discovery – by the western world
– of Australia, with significant and
damaging legal consequences for
its Aboriginal peoples, discussed
in these pages by Ragbir Bhathal.
Transits now have significance
for exploration in the search for
planets in other solar systems.
The transit method sounds simple
– using the dimming of light from
a star as a planet passes in front
of it to deduce orbital parameters
and size of an exoplanet – but
seeing the size of Venus as it
crosses the disc of our Sun does
highlight the precision needed
to detect Earth-sized planets on
Earth-like orbits. And it makes the
fact that we have the technology
to detect so many planets in this
way, inspirational.
Unfortunately, only the last hour
or so of the transit will be visible
from the UK in the early hours
of 6 June this year, but if you are
prepared to be up with the Sun,
you may see Venus in silhouette
for yourself. Good weather will
help, of course, as will being in the
north of the UK. Have a look at the
transit pages on the RAS website
or look online for transit times and
local events where you live.
3.4
Transit events and resources
Transit Early risers in the UK have
the opportunity to see the final
stages of the last transit of Venus
for more than a century.
The transit on 5 and 6 June will be
visible only in the early hours in
the UK, depending on the weather.
Despite the historical significance of
transits in determining distances in
the solar system, they are now valued for their rarity as astronomical
phenomena, the educational opportunities they present, and the sense
of a link with important events in
scientific and world history. There
are details about the transit available
on the RAS website, with links to
other transit sites. Diagrams of when
and where the transit can be seen are
available on the transitofvenus.org
website, for example, as well as useful
diagrams and explanations and practical suggestions and instruments for
safely viewing the transit in a group.
Many organizations are using the
transit as a focus for outreach with
exhibitions and events. The Royal
The 2004 transit of Venus, as seen
by the Williams College Transit of
Venus Team. (J M Pasachoff, D Butts,
J Gangestad, O Westbrook [Williams
College Transit of Venus Team], J
Seiradakis, G Asimellis [Aristotelian
University of Thessaloniki, Greece];
expedition run with B Babcock
(Williams College) and G Schneider
[University of Arizona])
to the Edge of the Cosmos” until 2
September 2012, as well as a free
Venus Transit smartphone app, and
a website to track the progress of
the expedition to observe the 2012
transit from Lord Howe Island in a
replica of Captain Cook’s ship HMB
Endeavour, organized by the Australian National Maritime Museum.
UNAWE, the European universe
awareness outreach project, is
focusing its work for the transit on
the Democratic Republic of TimorLeste, Indonesia, where the whole
of the event will be visible. UNAWE
will organize educational activities
there, including teacher training
workshops and a public observing event. UNAWE is also creating
new educational materials for local
schools and universities, and plans
to distribute Galileoscopes, solar
scopes and planispheres.
Observatory Greenwich has an
exhibition entitled “Measuring the
Universe: from the Transit of Venus
http://www.ras.org.uk
http://www.transitofvenus.org
http://www.rmg.co.uk
http://www.unawe.org
HST to use transit to probe venusian atmosphere
Transit Researchers interested in
the atmosphere of Venus will be
using the Hubble Space Telescope
and the Moon to examine sunlight
passing through the atmosphere
during the transit of Venus this
month. The technique is the same
as that used to determine atmo­
spheric constituents of transiting
exoplanets.
As with ordinary telescopes on
Earth, the Hubble Space Telescope is
not designed to point directly at the
Sun, so these observations will use
light reflected from the Moon, and
a battery of instruments at a range
of wavelengths from ultraviolet to
near-infrared: the Advanced Camera
for Surveys, Wide Field Camera 3,
and Space Telescope Imaging Spectrograph.
The success of the observations
Now, the space weather forecast
The Met Office is expanding its
services to include operational
space-weather forecasts for the
UK, working with the research
community to expand existing cli­
mate models. Further collabora­
tive work will apply the enhanced
model to extrasolar planets.
David Jackson of the Met Office
presented the work on the Unified
Model at the National Astronomy
Meeting in Manchester in March
this year. “To develop a more accurate and useful advanced-warning
system for space weather,” he said,
“we need to develop a system of
interconnected models that describe
the whole domain – the conditions
on the Sun, inter­planetary space, the
layers of the Earth’s atmosphere, all
the way down to the Earth’s surface.”
It is hoped that the forecasts will
benefit the aviation and power
industries, as well as a whole range
of activities that rely on GPS timing
and positioning, radio communication or satellite-based observations.
A further team, led by Isabelle
Baraffe of the University of Exeter
is adapting the Unified Model for
extrasolar planet climatology. “The
Met Office has developed a sophisticated tool for Earth weather forecasting and climate studies,” said David
Acreman of the University of Exeter.
“It could be of vital importance in the
interpretation of the wealth of observational data on extrasolar planets
we expect in the next decade.”
Extrasolar planets pose particular
problems such as the nature of the
atmospheric circulation on “hot
Jupiters”, giant gas planets orbiting very close to their parent stars.
In the longer term, the project will
be extended to study Earth-like exoplanet atmospheres and to identify
biosignatures, potentially revealing
biospheres and life.
http://bit.ly/GZuRAV
depends on observations throughout the seven hours of the transit,
requiring precise pointing of the
telescope on each 90-minute orbit
of the Earth. The Hubble team has
also prepared several test exposures
of its target reflecting areas on the
Moon ready to compare with the
image when light is passing through
the atmosphere of Venus.
http://hubblesite.org/news/2012/22
Astronomy
writing prize
The ESO and the STFC are organiz­
ing a Europe-wide competition for
the very best in astronomy journal­
ism in print, online or broadcast.
The winner gets a trip to ESO’s
Very Large Telescope in Chile.
The competition will capture and
promote inspirational coverage
of European astronomy and was
launched at the UK National Astronomy Meeting in March. Entries for
the European Astronomy Journalism
Prize must be about astronomy and
related areas of technology, or about
the work and lifestyles of astronomers, engineers or others working in
the field of astronomy. The competition is being run by the STFC and
ESO in conjunction with the Association of British Science Writers and the
RAS. Closing date is 27 July 2012.
http://www.eso.org/public/astroprize http://www.stfc.ac.uk/astroprize
A&G • June 2012 • Vol. 53