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| Ron |
 Posted: Wed Nov 10, 2004 3:24 pm |
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Guest
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http://www2.keck.hawaii.edu/news/science/uranus/index.html
KECK PICTURES OF URANUS SHOW BEST VIEW FROM THE GROUND
Keck Telescope
November 10, 2004
MAUNA KEA, Hawaii - Observations of Uranus conducted
at the W. M. Keck Observatory in Hawaii are surprising astronomers with
the level of detail they can see from the ground. Two separate teams of
astronomers, one from Berkeley/SSI and one from Wisconsin, used advances
in Keck adaptive optics (AO) to help make major scientific discoveries
regarding the planet's atmosphere and ring system. The results are a
powerful example of how ground-based telescopes are helping astronomers
study planets in the outer solar system that once could only be studied
from space. Early results were announced today at the 36th meeting of
the American Astronomical Society's Division for Planetary Sciences.
"We are stunned by the quality and detail of these images," said Dr.
Frederic Chaffee, director of the W. M. Keck Observatory in Hawaii.
"These are the best pictures of Uranus that have ever been produced by a
telescope, and they are opening new windows of understanding for this
unique and special world."
The most recent observations of Uranus show the planet as it approaches
its southern autumnal equinox, which takes place in 2007 (the length of
the year on Uranus is 84 Earth years). The two teams used narrow filters
at infrared wavelengths to study features in the atmosphere and ring
sets, both of which are enormously enhanced by the Keck adaptive optics
system. Ground-based telescopes are helping astronomers track climatic
changes in the planet's atmosphere.
"People may think that Uranus is relatively inactive, but these images
show that Uranus is definitely changing, and perhaps quite
dramatically," said Imke de Pater, professor of astronomy at University
of California, Berkeley, lead investigator for the team responsible for
the Berkeley observations. "What is causing it, no one knows for sure.
Only time will tell."
The new images are the result of many general improvements to the Keck
adaptive optics system. A new calibration technique removes artifacts
previously present in the images when measuring the atmospheric
distortion with a planet instead of a point source of light. Another
major improvement is a new wavefront reconstructor to improve the data
processing within the AO system. This dramatically reduces the effect
that "noise" or errors in measuring the atmospheric distortion have on
the image quality.
A dramatic visualization of the power of adaptive optics (Figure 1) was
made by Dr. Heidi Hammel of the Space Science Institute in Boulder,
Colorado and Dr. Imke de Pater of UC Berkeley, California. They took
images of Uranus and its rings with the second-generation Near Infrared
Camera (NIRC2) behind the AO system on the Keck II telescope, first with
the AO system off, and then with the AO system on. In this figure, the
ring system is more readily visible through the 2.2-micron filter
because methane absorption at this wavelength renders the planet
extremely dark except for a few high altitude clouds. In contrast, the
1.6-micron image shows deeper atmospheric cloud structure, including
many discrete features peppering the planet's northern hemisphere. At
1.6 microns, the rings are just barely visible as a faint streak across
the planet's northern hemisphere.
"The differences are stunning," said Hammel. "The detail provided by
Keck's AO system for the atmosphere and the rings of Uranus
fundamentally changes the science we can achieve."
Later observations conducted by the team at University of
Wisconsin-Madison, also with the Keck II AO system, were formed into a
composite image in which the highest clouds appear white, the middle
level clouds appear bright green, and the lower clouds appear darker
blue (Figure 2). The color balance used to reveal the cloud structure in
these infrared exposures, which are not normally visible to human eyes,
makes the ring system appear red in these images and is an artifact of
the process. The higher clouds are most abundant in the planet's
northern hemisphere.
Dr. Lawrence Sromovsky, principal investigator for the Wisconsin
observations said, "Twenty years ago we simply couldn't see the types of
details in the outer solar system the way we can today with large,
ground-based telescopes like Keck. These images actually reveal many
more cloud features than the Voyager spacecraft found after traveling
all the way to Uranus."
Until recently, little was known about the oddball planet, which gets
its name from the Greek word "Ouranos," a mythological god who
personifies the heavens. Uranus lies tipped on its side, probably the
result of an ancient cosmic collision, and its magnetic field lays
strangely off-set from and tilted with respect to the planet's
rotational pole. In 1986, the Voyager 2 spacecraft sent pictures to
earth of what appeared to be a non-descript ball suspended in space. At
that time, Uranus' South Pole was pointed almost directly at the sun,
and the North Pole pointed away. Now, more than 18 years later, the
planet is drawing near the point in its orbit where the planet's equator
will be pointing toward the Sun, and both poles will get about 17 hours
of sunlight a day.
On Earth, the massive storms captured in the new pictures of Uranus
would engulf nations as large as the continental United States, about 3
million square miles. But at a distance of more than 1.6 billion miles,
even such large storms are barely detectable and require the use of the
world's most powerful telescopes.
Funding for the telescopes and the Keck II adaptive optics system is
provided by the W.M. Keck Foundation. Optimization for the Keck adaptive
optics system is provided by the National Science Foundation and the
Technology Center for Adaptive Optics, managed by UCSC under cooperative
agreement No. AST 9876783 (de Pater). Additional funding was provided by
NASA grants NAG5-11961, NAG5-10451 (Hammel) and NAG5 12206 (Sromovsky).
The W. M. Keck Observatory is operated by the California Association for
Research in Astronomy (CARA), a non-profit 501 (c) (3) corporation whose
board of directors includes representatives from the California
Institute of Technology, the University of California, and the National
Aeronautics and Space Administration. For more information, please visit
www.keckobservatory.org.
Media Contact:
Laura K. Kraft
W.M. Keck Observatory
65-1120 Mamalahoa Hwy.
Kamuela, HI 96743
(808) 885-7887 |
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| Ralph Hertle |
| Posted: Thu Nov 11, 2004 12:34 am |
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Ron wrote:
[quote:532f8d27ab]http://www2.keck.hawaii.edu/news/science/uranus/index.html
KECK PICTURES OF URANUS SHOW BEST VIEW FROM THE GROUND
Keck Telescope
November 10, 2004
MAUNA KEA, Hawaii - Observations of Uranus conducted
at the W. M. Keck Observatory in Hawaii are surprising astronomers with
the level of detail they can see from the ground. Two separate teams of
astronomers, one from Berkeley/SSI and one from Wisconsin, used advances
in Keck adaptive optics (AO) to help make major scientific discoveries
regarding the planet's atmosphere and ring system. The results are a
powerful example of how ground-based telescopes are helping astronomers
study planets in the outer solar system that once could only be studied
from space. Early results were announced today at the 36th meeting of
the American Astronomical Society's Division for Planetary Sciences.
"We are stunned by the quality and detail of these images," said Dr.
Frederic Chaffee, director of the W. M. Keck Observatory in Hawaii.
"These are the best pictures of Uranus that have ever been produced by a
telescope, and they are opening new windows of understanding for this
unique and special world."
The most recent observations of Uranus show the planet as it approaches
its southern autumnal equinox, which takes place in 2007 (the length of
the year on Uranus is 84 Earth years). The two teams used narrow filters
at infrared wavelengths to study features in the atmosphere and ring
sets, both of which are enormously enhanced by the Keck adaptive optics
system. Ground-based telescopes are helping astronomers track climatic
changes in the planet's atmosphere.
"People may think that Uranus is relatively inactive, but these images
show that Uranus is definitely changing, and perhaps quite
dramatically," said Imke de Pater, professor of astronomy at University
of California, Berkeley, lead investigator for the team responsible for
the Berkeley observations. "What is causing it, no one knows for sure.
Only time will tell."
The new images are the result of many general improvements to the Keck
adaptive optics system. A new calibration technique removes artifacts
previously present in the images when measuring the atmospheric
distortion with a planet instead of a point source of light. Another
major improvement is a new wavefront reconstructor to improve the data
processing within the AO system. This dramatically reduces the effect
that "noise" or errors in measuring the atmospheric distortion have on
the image quality.
A dramatic visualization of the power of adaptive optics (Figure 1) was
made by Dr. Heidi Hammel of the Space Science Institute in Boulder,
Colorado and Dr. Imke de Pater of UC Berkeley, California. They took
images of Uranus and its rings with the second-generation Near Infrared
Camera (NIRC2) behind the AO system on the Keck II telescope, first with
the AO system off, and then with the AO system on. In this figure, the
ring system is more readily visible through the 2.2-micron filter
because methane absorption at this wavelength renders the planet
extremely dark except for a few high altitude clouds. In contrast, the
1.6-micron image shows deeper atmospheric cloud structure, including
many discrete features peppering the planet's northern hemisphere. At
1.6 microns, the rings are just barely visible as a faint streak across
the planet's northern hemisphere.
"The differences are stunning," said Hammel. "The detail provided by
Keck's AO system for the atmosphere and the rings of Uranus
fundamentally changes the science we can achieve."
Later observations conducted by the team at University of
Wisconsin-Madison, also with the Keck II AO system, were formed into a
composite image in which the highest clouds appear white, the middle
level clouds appear bright green, and the lower clouds appear darker
blue (Figure 2). The color balance used to reveal the cloud structure in
these infrared exposures, which are not normally visible to human eyes,
makes the ring system appear red in these images and is an artifact of
the process. The higher clouds are most abundant in the planet's
northern hemisphere.
Dr. Lawrence Sromovsky, principal investigator for the Wisconsin
observations said, "Twenty years ago we simply couldn't see the types of
details in the outer solar system the way we can today with large,
ground-based telescopes like Keck. These images actually reveal many
more cloud features than the Voyager spacecraft found after traveling
all the way to Uranus."
Until recently, little was known about the oddball planet, which gets
its name from the Greek word "Ouranos," a mythological god who
personifies the heavens. Uranus lies tipped on its side, probably the
result of an ancient cosmic collision, and its magnetic field lays
strangely off-set from and tilted with respect to the planet's
rotational pole. In 1986, the Voyager 2 spacecraft sent pictures to
earth of what appeared to be a non-descript ball suspended in space. At
that time, Uranus' South Pole was pointed almost directly at the sun,
and the North Pole pointed away. Now, more than 18 years later, the
planet is drawing near the point in its orbit where the planet's equator
will be pointing toward the Sun, and both poles will get about 17 hours
of sunlight a day.
On Earth, the massive storms captured in the new pictures of Uranus
would engulf nations as large as the continental United States, about 3
million square miles. But at a distance of more than 1.6 billion miles,
even such large storms are barely detectable and require the use of the
world's most powerful telescopes.
Funding for the telescopes and the Keck II adaptive optics system is
provided by the W.M. Keck Foundation. Optimization for the Keck adaptive
optics system is provided by the National Science Foundation and the
Technology Center for Adaptive Optics, managed by UCSC under cooperative
agreement No. AST 9876783 (de Pater). Additional funding was provided by
NASA grants NAG5-11961, NAG5-10451 (Hammel) and NAG5 12206 (Sromovsky).
The W. M. Keck Observatory is operated by the California Association for
Research in Astronomy (CARA), a non-profit 501 (c) (3) corporation whose
board of directors includes representatives from the California
Institute of Technology, the University of California, and the National
Aeronautics and Space Administration. For more information, please visit
www.keckobservatory.org.
Media Contact:
Laura K. Kraft
W.M. Keck Observatory
65-1120 Mamalahoa Hwy.
Kamuela, HI 96743
(808) 885-7887
[/quote:532f8d27ab]
Thank you for the fine job of science and reporting.
The facts are wonderful.
Ralph Hertle |
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| Mike Maxwell |
| Posted: Thu Nov 11, 2004 10:03 am |
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Ron wrote:
<snip>
[quote:e08a9a70c8]"We are stunned by the quality and detail of these images," said Dr.
Frederic Chaffee, director of the W. M. Keck Observatory in Hawaii.
"These are the best pictures of Uranus that have ever been produced by a
telescope, and they are opening new windows of understanding for this
unique and special world."
[/quote:e08a9a70c8]
They are indeed nice pics. Which made me wonder--what would Keck be
able to see of Pluto, and how would the pictures compare with those
taken by Hubble? Pluto is roughly 20x smaller and 2 and a half times
further from the Sun, so I guess it would still show up pretty small...
Mike McSwell |
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