A new podcast, Astronomy 141, Life in the Universe, is available
for those interested in continuing an exploration of topics in
modern astronomy.
Dec 6, 2009
Are there planets around other stars? Are there Earth-like planets
around other stars? Do any of those harbor life? Intelligent life?
We'd like to know the answers to all of these questions, and in recent
years we've made great progress towards at least answering the first.
To date, more than 200 planets have been found around other stars, most in the
interstellar neighborhood of the Sun, but a few at great distance. This
lecture reviews the search for ExoPlanets, discussing the successful
Doppler Wobble, Transit, and Microlensing techniques. What we have
found so far are very suprising systems, especially Jupiter-size or
bigger planets orbiting very close (few hundredths of an AU) from their
parent stars. The existance of a significant population of so-called
"Hot Jupiters" may be telling us that planetary migration can be much
more extreme that we saw in our own Solar System, or that these
planetary system formed in a very different way than ours. It seems
appropriate to end this class with more questions than answers, but
that's where the science becomes most exciting. Recorded 2006 Dec 1 in
100 Stillman Hall on the Columbus campus of The Ohio State University.
Dec 1, 2006
What is a planet? Is Pluto a planet? This lecture traces the debate on
the nature of what it means to be a planet by taking an historical approach,
looking at how the question has arisen with the discovery of the asteroids and
later Pluto and the Kuiper Belt. Many of the issued raised at the 2006
IAU General Assembly meeting were raised two centuries before after the
discovery of Ceres and Pallas. We will end with the new definition of a
planet, and why Pluto is better understood as a Dwarf Planet, among the
two largest objects of the class of small icy bodies of the outer solar
system, than as the smallest of the planets. Recorded 2006 Nov 30 in
100 Stillman Hall on the Columbus campus of The Ohio State University.
Nov 30, 2006
Comets are occasional visitors from the icy reaches of the outer Solar
System. This lecture discusses the orbits, structure, and properties of
comets, and introduces the "dirty snowball" model of a comet nucleus.
The end of class was a demo where I created a model of a comet nucleus
from common household and office materials. Imagine a twisted
combination of Alton Brown and Emeril Lagasse with a PhD in Astrophysics
and you get the idea. We were not able to arrange for a videographer to
come, but we did get some stills before the batteries died on the
digital camera. The pictures are on the lecture webpage. The lecture
is slightly abbreviated because we did the student evaluation of
instruction surveys before class started. Recorded 2006 Nov 29 in 100
Stillman Hall on the Columbus campus of The Ohio State University.
Nov 29, 2006
Beyond the orbit of Neptune is the realm of the icy worlds, ranging in
size from Triton, the giant moon of Neptune, and the dwarf planets Pluto
and Eris, all the way down to the nuclei of comets. This lecture
discussed the icy bodies of the Trans-Neptunian regions of the Solar
System, discussing the basic properties of Triton (the best studied such
object), Pluto, Eris, and the Kuiper Belt, introducing the dynamical
families of Trans-Neptunian Objects that record in their orbits the slow
migration of Neptune outwards during the early history of the Solar
System. The Kuiper Belt is the icy analog of the main Asteroid Belt of
the inner Solar System: both are shaped by their gravitational
interaction with giant gas planets (Jupiter for the asteroids, Neptune
for the KBOs), and are composed of leftover raw materials from the
formation of their respective regions of the Solar System. Recorded
2006 Nov 28 in 100 Stillman Hall on the Columbus campus of The Ohio
State University.
Nov 28, 2006
Asteroids are the leftover rocky materials from the formation of the
Solar System that reside mainly in a broad belt between the orbits of
Mars and Jupiter. Meteoroids are fragments of asteroids or bits of
debris from passing comets that occasionally pass through our atmosphere
as meteors, and even more rarely survive the fiery passage to reach the
ground as a meteorite. This lecture reviews the physical and dynamical
(orbital) properties of Asteroids and Meteoroids, and discusses the role
of Jupiter and orbital resonances in dynamically sculpting the Main
Belt. Recorded 2006 Nov 27 in 100 Stillman Hall on the Columbus campus
of The Ohio State University.
Nov 27, 2006
All Jovian planets have rings. We are most familiar with the bright,
spectacular rings of Saturn, but the other Jovian planets have rings
systems around them. This lecture describes the different ring systems
and their properties, and discusses their origin, formation, and the
physics - resonances and shepherd moons - that govern their evolution.
Recorded 2006 Nov 22 in 100 Stillman Hall on the Columbus campus of The
Ohio State University.
Nov 22, 2006
Saturn is attended by a system of 56 known moons and bright, beautiful
rings. The Moon system is the focus of our attention today. Saturn has
one giant moon, Titan, which is the 2nd largest moon in the Solar
System, and the only one with a heavy atmosphere. On Titan, the
atmosphere is mostly nitrogen and methane, but the temperature and
pressure are such that methane plays the same role that water plays on
the Earth: it can be either a solid, gas, or liquid. I will review
tantalizing evidence from the Cassini and Huygens probes that there is,
in fact, liquid methane and maybe even liquid methane lakes on Titan.
Most of the other moons are ancient, icy, and heavily cratered -
geologically dead worlds - but one, Enceladus, is a big surprise. The
shiniest object in the Solar System, Enceladus has spectacular fountains
- cryovolcanos - that spew water vapor from reservoirs created in its
tidally-heated interior. This ice repaves much of the surface of
Enceladus, giving it a young, shiny surface, and builds the E ring of
Saturn. Recorded 2006 Nov 21 in 100 Stillman Hall on the Columbus
campus of The Ohio State University.
Nov 21, 2006
Jupiter is surrounded by a solar system in miniature of 63 known moons.
Most (59) are tiny, irregular bodies that are a combination of captured
asteroids and comets. The 4 largest are the giant Galilean Moons: Io,
Europa, Ganymede, and Callisto. Each is a fascinating world of its own,
with a unique history and properties: volcanically active Io, icy Europa
which may hide an ocean of liquid water beneath the surface, the grooved
terrain of Ganymede, and frozen dirty Callisto with the most ancient
surface of the four. Recorded 2006 Nov 20 in 100 Stillman Hall on the
Columbus campus of The Ohio State University.
Nov 20, 2006
Uranus and Neptune are the smallest and outermost of the 4 Jovian
planets. While superficially similar to Jupiter and Saturn, there are
substantial differences. Uranus and Neptune have smaller rocky cores
surrounded by deep, slushy ice mantles and relatively thinner hydrogen
atmospheres, quite different from the massive cores and deep metallic
hydrogen mantles of Jupiter and Saturn. We will also ask why they
appear blue, look at their internal energy and weather, and then review
the properties of the Jovian planets as a group. Recorded 2006 Nov 16
in 100 Stillman Hall on the Columbus campus of The Ohio State
University.
Nov 16, 2006
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