Our Place in the COSMOS

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Our Place in the COSMOS
MVUC 1 August, 2004
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Earthrise as viewed from the Moon by the Apollo
11 spacecraft (1967)
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Planetary Exploration in the 21st Century The
New Missions to Mars
The worlds space agencies have recently agreed
to embark on an ambitious plan to send a series
of robotic spacecraft to Mars over the next 20
years - to explore the planets surface in search
of previous signs of life, and to return rock
and soil samples to the Earth for further study.
The ultimate goal of the Mars missions is to
land humans on the martian surface by the year
2030. The round-trip will require the
development of new rocket engines (such as ion
propulsion ) that could reduce the one-way
Earth-Mars travel time to a few months. The
journey to Mars will likely require the
establishment of a permanent base of operations
on the Moon where relatively light-weight
ion-propulsion spacecraft might be assembled
after the parts are ferried to the Moon from the
Earth using conventional liquid-fuel rockets.
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Martian polar caps contain a mixture of water-ice
and dry-ice ( frozen carbon dioxide). The
polar caps grow and shrink with the change of the
Martian seasons. Substantial water ice may also
exist under the Martian surface. The numerous
dry river channels that criss-cross the Martian
surface clearly show that running water was once
abundant on the Martian surface -- it likely
evaporated into space more than 3 billion years
ago.
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The US space agency (NASA) has sent space probes
to both flyby and orbit all of the planets in
our solar system. This slide is from NASAs
homepage, where you can find a wealth of
information on the scientific information
returned from all of NASAs space probes. The
outermost planet Pluto along with its large
moon Charon, will be visited by Pluto Express
which is scheduled for launch later this decade.
Pluto is more correctly identified as one of the
largest members of the Kuiper Belt, a group
of objects that reside primarily just beyond the
orbit of Neptune. The Kuiper Belt contains
millions of objects with rocky cores and ice
mantles that are more commonly known as comets.
Many of the Kuiper Belt objects are perturbed
and eventually captured by the gravitational
influence of Neptune into what are known as
resonance orbits around the Sun. This is very
likely what has happed to the Pluto-Charon
system.
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A close-up image of the planet Saturn taken with
the giant Keck telescope on the 14,000 ft summit
of Mauna Kea in Hawaii, showing that even from
the distance of Earth one can obtain spectacular
images of the surface features and rings of the
distant Giant planets (Jupiter, Saturn, Uranus,
Neptune) in our outer solar system.
Recently, the joint NASA/ESA Cassini spacecraft
(named after the French astronomer who discovered
the division or gap that is observed within the
ring system), passed through Saturns ring system
on its way into permanent orbit around the
planet. Cassini carries a probe (nicknamed
Huygens) which will be dropped onto Saturns
largest moon, Titan, in an attempt to determine
if Titan once harbored life. Watch the news for
close-up views of Saturns moons and the planets
cloud layers and rings as Cassini continues to
provide unprecedented images of the Saturn system.
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A pictoral catalog of the millions of small
planetesimals (i.e. asteroids and comets) which
have been discovered by the various NASA
Spacewatch programs which are designed to
protect the Earth from the threat of being hit
by one of these bodies Note this is a movie
which shows the various families of
planetesimals. The family names are shown in a
small box in the upper left corner. This movie
will only display from the fully downloaded .pdf
file.
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Stellar birth -- the Rosette Molecular Cloud
Our Solar System was born in a giant cloud of gas
and dust, most likely similar to the Rosette
Nebula shown above. Thousands of these large
gas clouds can be found throughout our Galaxy,
the Milky Way. This gas nebula already contains a
rich collection of molecules such as water (H2O),
ammonia (NH3), and methane (CH4) and other larger
molecules thought to be the precursors of life.
Pieces of the Rosette nebula are collapsing under
the force of gravity, leading to the formation of
groups, or cluster of stars. The brightest new
stars can be seen in the very center of the
glowing cloud of gas and dust. The nebula will
eventually form thousands of stars (each with its
own system of planets ..). Like our Sun, the
stars will eventually disperse throughout our
galaxy as they drift away from their birthsites,
and as the gas and dust cloud dissipates due to
the intense heat and radiation given off by the
most massive stars that are formed.
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Stellar old age -- a Red Giant Star
At the other end of a stars lifecycle, the first
evidence of stellar death coincides with the
onset of the formation of a Red Giant star,
when a stars outer regions expand and the star
swells in diameter by more than a thousand fold.
Our Sun will enter the red giant phase about 5
billion years from now at which point its
surface will likely expand to a large enough size
to cover the orbit of the Earth. The picture
above is of the star Beatleguse, a massive red
giant star in the constellation Orion. This
image was taken with the Canada-France-Hawaii
3.6m telescope located on the summit of Mauna Kea.
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Stellar death -- The Ring Nebula
As a star like the Sun approaches its final death
stage, it will shed the bloated outer layers of
its red giant phase, ultimately revealing an
extremely hot, and compact core known as a white
dwarf star. Here, we see such a white dwarf
star, ?-Lyra, at the center of the colorful Ring
Nebula. ?-Lyra has recently expelled its outer
gas layers, which now continue to glow in
several colors characteristic of the atoms of
hydrogen, helium, oxygen, nitrogen, etc. These
expelled layers of gas will eventually detach
themselves from the gravitational attraction of
their former host star. This phase of stellar
death is natures way of seeding the interstellar
medium with the heavier elements that were made
inside the star. Without such heavy elements, we
humans would not exist !!
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Wide angle photograph of our galaxy - The Milky
Way
The picture above was taken by an amateur
astronomer using a conventional camera with a
very wide field-of-view lens. The exposure was
captured by keeping the lens open for several
minutes, hence thetrails due to relatively
close near-Earth asteroids whose positions change
substantially during the exposure. The much
more distant stars and gas clouds which make up
our Galaxy do not appear to move substantially
during the exposure. If you have ever looked up
at the summer sky on a very dark night you will
likely have seen the milky band as shown above,
stretching across the nighttime sky. This
band is actually an overabundance of stars
along with opaque clouds of gas and dust which
make up the inner regions of our Milky Way
galaxy. The band is simply the edge on view of
our Galaxy, which in reality is a relatively thin
disk-like object.
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Panoramic view of the sky at infrared wavelengths
showing an edge-on view of the Milky Way
This is one of the first views of the sky showing
the full edge-on disk of our galaxy the Milky
Way. This panoramic view was obtained in the
near-infrared with the 2-Micron All-Sky survey
telescope. The small satellite galaxies - the
Large and Small Magellenic Clouds - can be seen
below the disk of the Milky Way, in the lower
right portion of the image. The thousands of
dots scattered over the entire image are both
very nearby stars in our own galaxy as well as
much more distant Galaxies.
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Andromeda (M31)
A visible-light image of our nearest large
neighbor galaxy, Andromeda (also known by its
catalog name of Messier 31) obtained with the
Canada-France-Hawaii 3.6m telescope on Mauna Kea
in Hawaii. Our Milky Way galaxy would look
something like this if viewed from Andromeda !
Like our own galaxy, Andromeda contains perhaps
one hundred billion stars, the majority of which
likely have their own planetary systems.
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The spiral galaxy - M81
Images taken in optical and infrared light of the
same nearby galaxy, Messier 81. The different
images emphasize different parts of the galaxy -
optical light favors the stars while the infrared
light images better show the clouds of gas and
dust out of which new stars are forming. The
infraed images were just recently obtained with
NASAs Spitzer infrared satellite.
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Our largest nearby neighbor galaxies
A collection of the 30 largest nearby neighbor
galaxies as seen by the 2MASS Telescopes in
near-infrared light. Each of these galaxies
contains over one hundred billion stars. Their
individual shapes vary depending largely on the
angle at which their thin disk of stars is
inclined to our line of sight from Earth.
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The Hubble Deep Field
The famous Hubble Deep Field (HDF)represents
the longest exposure ever obtained with the
wide-field-planetary camera (WFPC2) on-board the
Hubble Space Telescope. This deep 320Hr exposure
revealed for the first time the true number
density of galaxies in the sky. NONE of the
nearly 5,000 objects in this image would be seen
with the unaided eye !! The smallest and
faintest objects in this image represent galaxies
at the most distant reaches of the universe,
whose light is just now reaching us after
traveling over trillions of miles. The diameter
of the HDF is only one-tenth the diameter of the
full Moon, yet it shows nearly 5,000 galaxies. A
similar density of galaxies would be seen over
the entire sky, if the entire sky were to be
imaged with WFPC2 using similar long exposures.
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The Hubble Space telescope Ultra-Deep Field (UDF)
This is the latest and deepest optical image of
the sky to be obtained with the Hubble Space
Telescope. It was taken with the new Advanced
Camera for Surveys (ACS) which is able to image a
7x larger region of the sky than was possible
with the WFPC2 camera. The ACS is also more
sensitive than the older WFPC2 camera, thus the
above exposure reveals even fainter objects than
were seen in the previous picture of the HDF.
Such images as shown here are affectionately
known as cosmic wallpaper. Eventually the
entire sky will be imaged to a similar depth as
shown above, using a new Generation of
wide-field telescopes equipped with gigapixel
cameras such as the new PanSTARRS Telescope
being constructed in Hawaii. The PanSTARRS
all-sky deep survey will will catalog over one
hundred billion galaxies !!
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Curiosity and imagination are the human traits
that drive the pace of astronomical discovery,
and the pace of that discovery has been truly
breathtaking over the past 30 years. Using
data from a new generation of spacecraft and
large ground-based telescopes, astronomers have
been able to determine the true size and age of
our Universe, and are on the verge of cataloging
the nearly one hundred billion galaxies that it
contains. Galaxies typically contain
billions of stars, and the majority of these
stars are accompanied by planets. The new field
of astrobiology is developing methods to search
for life that almost certainly exists on some
planets around some stars. We are not
alone. But despite our success at mapping our
Universe, one basic question remains the same --
Where did it all come from ? .