Announcements
•The last 1st Quarter Observing Night is next
Wednesday. Starts at 7:30pm so set-up begins at
6:45pm. Meet here at that time. We will set-up in
the Atrium with a few Dobs outside if it is clear.
•Don’t forget the second project. Presentations are
two weeks from Tuesday.
•Exam 3 is Tuesday May 3 at 4:00pm. Will cover
Chapters 8 & 9. Sample questions are posted.
Astronomy Courses Next
Semester (and beyond)
Next Semester
•Astr 3005/3006: Observational Astronomy
Beyond
•Astr 3020: Cosmology
•Astr 3040: Astrobiology
•Astr 4010/4020: Astrophysics I & II
•Astr 3030: Astronomical Methods and Instrumentation
•Astr 4000/4001: Astrophotography
Where does the Sun get its energy?
In 1848, Julius Mayer calculated
the life of the Sun as a coal burning
furnace
He came up with only a few
thousand years. After that, he
suggested the impact of
meteorites would keep it hot
William Thomson, Lord Kelvin, also
proposed infalling material
To generate enough heat, this would add mass to the Sun,
changing the orbital periods of the planets within a few centuries
Hermann Helmholtz proposed
gravitational contraction as a
source of energy
This would last a few million years but geology said the
Earth was at least hundreds of millions of years old
It would be 1926 before Arthur
Eddington proposed that the Sun
transmuted hydrogen into helium
Eddington didn’t know what
the precise mechanism was
but he knew that, since the
mass of four hydrogen atoms
is more than the mass of one
helium atom, E = mc2 was the
only energy production
process that could last long
enough.
It was Hans Bethe who proposed
the detailed mechanism of
hydrogen fusion in the Sun
He won the 1967 Nobel Prize for his
work in understanding the process
As astronomy advanced, better
telescopes were needed
Most 19th century observatories
used a “transit circle” telescope
The early reflectors used speculum
mirrors: a copper/tin alloy
Speculum tarnished easily and required
frequent polishing and reshaping
Justus von Liebig, a chemist, figured
out how to metalize a glass blank
Large achromatic refractors were
still being made, though
The last great refractors were
made by Alvan Clark & Sons
Using glass blanks made by the Chance Brothers of
Birmingham and Feil-Mantois of Paris the Clarks ground
the finest refractors ever
The largest refractor ever made was
the 40” at the Yerkes Observatory
With improved techniques,
reflectors were becoming the
instrument of choice
The 100” Hooker Telescope
on Mount Wilson
Lassel’s 40” reflector
on Malta
Solar System Studies
Charles Messier was one of the most famous comet
hunters but he never followed up on his discoveries
to determine the nature of comets
Giovan Donati was the first to do
serious telescopic studies of a
comet in 1858
F. A. Bredikhin compiled
descriptions and images of comets
and came up with a modest theory
It wasn’t until Fred Whipple in the
1950’s that we got a true
understanding of comets
Shooting Stars
Meteor falls had been observed in
history
The 1492 Ensisheim
fall in Germany was
well documented
Ernst Chlandi speculated that
meteorites were leftovers from the
formation of the solar system
The great Meteor Storm of
1833 sparked interest in the
study of meteors
Denison Olmsted figured out the
November meteors all seem to come
out of Leo
John Locke and Hubert Newton
deduced the radiants for the
Aquariads and the Perseids
John Couch Adams calculated orbits
and correlated them to comets
The Leonids were from Comet Temple
The discovery of moons
Galileo
discovered the
major moons
of Jupiter in
1610 in some
of his first
observations
using the
newly invented
telescope
Io
Ganymede
Europa
Callisto
Soon, moons of Saturn were
being discovered
Titan was discovered by
Christiaan Huygens in 1655
Giovanni Cassini discovered
four more Saturnian moons
Iapetus in 1671
Rhea in 1672
Dione and Tethys in 1684
Neptune has one large moon:
Triton
William Lassell discovered Triton in 1846 only a few
weeks after Neptune was discovered
By 1851 Lassell had discovered
two more moons around Uranus
Lassell discovered Ariel
and Umbriel. Herschel
had already discovered
Oberon and Titania.
Miranda wasn’t
discovered until 1948.
Voyager 2 discovered
10 more moons in
1986. Since then
another 11 have been
discovered
Asaph Hall discovered the moons of
Mars in 1877 using the USNO 26”
refractor
Giovanni Schiaparelli made detailed
observations of Mars in 1877
He made even more detailed
observations during the 1888
opposition
A mis-translated word set Percival
Lowell off in search of Martians
H. G. Wells picked up on the
Martians mania
On October 30, 1938
the Mercury Theater
broadcast an
adaptation of War of
the Worlds. Listen to
it on the YouTube link.