Download Planets and Transits

Keynote Speaker
Dr Fred Watson

Rotary District Conference
Wollongong, 18 March 2012
In the Face of The Sun
Planets and Transits
FRED WATSON
Anglo-Australian
Observatory
What is a transit?
Planets and
Transits
Transit geometry
Why isn’t there a Venus transit every year or so?
Venus’ orbit is tilted relative to Earth’s…
This makes transits of Venus
jolly rare events…
Planets and
Transits
Cyclic phenomenon…
Transits of Venus
follow a 243-year
repeating pattern.
They always occur in
June or December
because that is when the
Earth crosses the line of
nodes.
Planets and
Transits
Hans Lipperhey
On the request of Hans Lipperhey, born in Wesel, living
in Middelburg, spectacle-maker, having discovered a
certain instrument for seeing far, as has been shown to
the Gentlemen of the States, requesting that, since the
instrument ought not to be made generally known, he be
granted a patent for thirty years…
Thurs. 2nd October, 1608
Planets and
Transits
The dawn of the telescope era…
Della Porta’s sketch
of 1609 shows the
principle.
But it was Galileo
who turned it into an
engine of discovery
in the same year
Planets and
Transits
The 1639 transit
Drat!
I’ve missed
the good
bit.
Predicted by Jeremiah Horrocks (1618-1641).
Observed by him at Much Hoole, 4 Dec. 1639.
Had to dash off to church before the event started.
Venus was in mid-transit when he returned.
What he actually said…
‘Then I beheld a most agreeable
spectacle… a spot of unusual
magnitude and of a perfectly
circular shape…’
The 1639 transit
It was also observed by his friend William Crabtree
(1610-1644), a Manchester cloth-merchant.
More transit geometry
Why is a Venus transit potentially so useful?
It allows you to measure the distance to the Sun
Bright idea courtesy of
Edmond Halley (1656-1742)
Planets and
Transits
The 1769 transit
By then, telescopes had improved significantly.
And governments
were prepared to
fund expeditions to
far-flung places to get
the best view of the
transit.
Planets and
Transits
The 1769 transit
• James Cook in Tahiti
• (And the rest is history…)
Planets and
Transits
The trouble with transits
Cook and others
found their timings
spoiled by the blackdrop effect...
1874
Planets and
Transits
The 1874 transit in Australia
Henry C. Russell:
‘Never perhaps in the
world’s history did
morning dawn on so
many waiting
astronomers as it did
on 9 Dec. 1874.’
He observed from
Sydney, Woodford,
Eden and Goulburn.
Russell’s rival, John
Tebbutt, disparagingly
described his report on
the 1874 transit as a
‘…gorgeous volume…’
Planets and
Transits
And again in 1882…
Consternation!
German transit expedition in Chile, 1882
Photographic assistance
Taken by
William
Harkness of
the US Naval
Observatory,
6 Dec 1882.
(It was cloudy
in Sydney.)
Harkness looks to the future…
‘We are now on the eve of the second transit of a
pair, after which there will be no other till the
twenty-first century of our era has dawned upon
the earth, and the June flowers are blooming in
2004…
What will be the state of science when the next
transit season arrives, God only knows.’
(Dec 1882.)
Planets and
Transits
The transit of 6 June 2012…
Don’t look directly at the Sun (especially not
through binoculars or a telescope)!
Use eyepiece projection (like Horrocks) or
check the NASA webcast (unlike Horrocks).
Sydney times: First contact 08:16
Second contact 08:34
Mid-transit 11:30
Third contact 14:26
Fourth contact 14:44
Planets and Transits
What is the use of planetary transits
today?
So, looking for the characteristic dimming is a
good way to find extra-solar planets…
And it tells us much about the the planet and
star, as well as how many are out there…
Hence new telescopes…
• …such as the 0.9-m
RCT (Robotically
Controlled
Telescope) at Kitt
Peak in Arizona.
Planets and Transits
A Special Sort Of
Transit…
By an astonishing
cosmic coincidence, the
Moon is 400 times
smaller than the Sun,
but is on average 400
times nearer.
Thus we have the
possibility of Total Solar
Eclipses...
Planets and
Transits
Planets and
Transits
Planets and
Transits
Planets and
Transits
Northern Australia, 14 Nov 2012, 06:39
Planets and
Don’t miss it!!
Transits
Planets and Transits
Back to Venus…
Transit of Venus 1769
Planets and
Transits
Transit of Venus 1882
Transit of Venus 2004
THE END
In the Face of
the Sun
THE END
In the Face of
the Sun