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| Photo: In this artificial solar spectrum,
the vertical black lines are caused by absorption due
to the sun's compositional elements. Spectrum courtesy
of Dr. Fred Chaffee. |
Looking at a Hubble image doesn't reveal what a galaxy is made
of, how fast it is spinning, and how far away it is. To answer
these kinds of questions, astronomers analyze spectra, or the
component colors of stars. The light from our sun peaks in the
green part of the spectrum, which means that the sun's surface
is roughly 5,500 degrees Celsius. Stars with spectra which peak
in the blue or ultraviolet are hotter than the sun, and stars
with spectra which peak in the red are cooler than the sun.
The spectra indicate the temperature of a star, the component
elements which make up that star, and the speed at which a star
is moving toward or away from Earth. Each star has a unique
spectral "fingerprint" which helps scientists to understand
a great deal about the composition and properties of that star.
Spectra are so important to astronomers that taking spectra
occupies about 75 percent of the time at most of the world's
major observatories -- Keck Observatory included.
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Photo courtesy of W. M. Keck Observatory.
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Hawai'i is the best place on the planet to do astronomy, because
of its unique position on the globe. And Keck Observatory has
the biggest telescopes on earth. Astronomers use Keck's telescopes
to study our own solar system and beyond -- to the far reaches
of the universe -- at a fraction of the cost of space-based
telescopes. According to Dr. Fred Chaffee, Keck is a relatively
young observatory. "Over the next 20 years, the discoveries
made here may well be the most amazing in all human history,"
says Chaffee. It is likely that some of these discoveries, like
the "legacy" discoveries described below, will be completely
surprising and unexpected.
THE LEGACY DISCOVERIES
The Outer Solar System
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| Photo: Image of 2003 UB313 and its
moon, courtesy of Dr. Mike Brown. |
Astronomers at Keck Observatory have found planet-size
objects in the outer solar system that orbit our sun.
These "new" planets are something scientists would never
have thought possible ten years ago. Three years ago,
Caltech's Mike Brown identified "2003 UB313," an object
which is larger than Pluto and appears to have a moon
orbiting it. Since then, study of our outer solar system
has exploded with new discoveries. These recent discoveries
have ignited a debate about the definition of a planet. |
Extrasolar Planets
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| Photo: An artist's rendering of an
extrasolar planet orbiting its sun. Image by Lynette
Cooke. |
Extrasolar planets are those which orbit around stars
other than our own sun. Geoff Marcy
of the University of California at Berkeley has perfected
an ingenious technique for discovering extrasolar planets,
and he and his colleagues hold the distinction of discovering
more planets than have been discovered in all previous
human history: about 180 of them. As a planet orbits around
its star, planetary gravity exerts a pull on the star,
causing the star to wobble. The larger the planet and
the closer it passes to its star, the greater the wobble.
Astronomers can detect this wobble in a star by studying
the spectrum of that star over a period of time. The spectrum
of a wobbling star will shift slightly to the right and
then back to the left as the planet passes around it.
Marcy has used Keck telescopes to study stars in the vicinity
of our solar system. So far, Marcy has discovered over
400 sun-like stars that demonstrate "wobbles," leading
scientists to conclude that these stars have planets orbiting
around them. "It seems likely that many of these stars
have earth-like planets around them in addition to the
larger planets that Marcy's team has been discovering,
though we don't yet have the technology to detect them,"
explains Chaffee. "I predict that in the lifetime of our
children, we will discover life on another planet in the
universe." |
The Milky Way's Black Hole
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| Photo: A three color image of the
center of our Galaxy with the black hole (Sgr A*)
labeled. Surrounding the black hole is a rich population
of stars both young and old as well as a striking
dust lane running from the top left to the bottom
right of the image. The dust is spiraling in towards
the black hole. Image courtesy of Professor Andrea
Ghez and her research team at UCLA, using data from
the W. M. Keck Observatory. |
Ten years ago, black holes were largely science fiction.
Now they are science fact. Indeed, astronomer Andrea
Ghez has documented the existence of a black hole
at the center of our own Milky Way galaxy, as part of
her work at Keck Observatory. Ghez has plotted the position
of stars orbiting the center of our galaxy for about 10
years now -- since before the advent of adaptive optics
at Keck Observatory. Without adaptive optics, it might
have taken Ghez an entire lifetime to plot the orbit of
one star, but with adaptive optics, she has been able
to obtain enough high angular resolution images of stars
near the center of our galaxy to prove the existence of
a supermassive black hole there, named Sagittarius A*
(Sgr A*). |
Gamma Ray Bursters
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| Photo: An artist's rendition of a
gamma ray burster. Image by Dana Berry, Skyworks
& SEW, courtesy of Dr. Fred Chaffee. |
For the past 25 years, astronomers have been aware of
huge bursts of energy occurring daily from somewhere in
the universe, but it was not until 1998 that Keck data
was able to show that these bursts were coming from very,
very far away - from "cosmological distances." These huge
bursts of energy, called gamma ray bursters, may be caused
by the collision of two stars or black holes, or by a
single star reaching the end of its life. In a tremendous
burst of energy, called a hypernova, the core of a dying
star collapses from its own gravity into a black hole,
suddenly compressing its material into its core. This
event creates a gamma ray burst, which lasts about ten
seconds. In that 10 seconds, the burster puts out more
energy than the entire rest of the universe combined.
Dr. Shri Kulkarni from the California Institute of Technology
is the world's leading expert on gamma ray bursters. On
November 20, 2004, Kulkarni was able to obtain spectra
of a gamma ray burster during its ten-second lifespan.
This groundbreaking work was done at Keck Observatory.
Learn more
here. |
The Most Distant Objects in the Universe
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| Photo: Galaxies ranging from several
hundred million to 13 billion light years (LY) away.
Big red = 5 billion LY; little chaos = 8 billion
LY; smudge above bright star = 13 billion LY. Hubble
Deep Field image courtesy of Dr. Robert Williams,
HST. |
In the early 20th century, Edwin Hubble discovered that
our universe is expanding, by studying the spectra of
various celestial objects. Looking at the spectrum of
an object reveals the speed at which it is moving. Using
its speed, scientists can calculate how far the object
is away from Earth. Astronomers at Keck Observatory have
studied the spectra of thousands of galaxies, using spectroscopic
images of each galaxy to determine its distance from Earth.
The technique of gravitational lensing, or using a massive
object in the foreground to help magnify very faint objects
in the background, has allowed Keck astronomers, including
Dr.
Richard Ellis from the California Institute of Technology,
to detect objects which are very far away and which date
back nearly to the origin of the universe. The furthest
object currently recorded is 13.3 billion light years
away. The current estimate is that the universe is 13.7
billion years old. Chaffee admits that he was a member
of a team which for a few weeks held the record for finding
the most distant object in the universe; he still has
the t-shirt to commemorate this glorious, if fleeting,
achievement! |
The Accelerating Universe
Perhaps the most unexpected and perplexing discovery made
at Keck Observatory is the existence of "dark
energy" or an anti-gravity which is pushing the universe
apart. The universe is not just drifting through space,
but rather, it is accelerating as it expands. Astronomers
studied spectra from 200 supernovae and realized that
their predictions about the distance of these objects
from Earth were underestimated. The spectra were too faint,
indicating that the supernovae were further away than
scientists had anticipated. The cause is attributed to
a mysterious dark energy. "We have no idea what this is,"
says Chaffee, "but it could be one of the most important
discoveries in modern astronomy."  |
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