天王星 月惑星研究会 関西支部
Uranus Image 2006/08/23(UT)
Ralf Vandebergh,Willem Kivits,Frank J Melillo,Hubble Space Telesc
Ralf Vandebergh(250mm Newton)|
Attached are observations of Uranus from last night (Aug 23) taken in almost exellent planetary conditions,no wind/some haze
A little haze is still acceptable for Uranus when working at the right f-ratio.
The red light images show some albedo variations again,and both the red and the lum image from (right) show a compareable structure
which is in equatorial direction.It seems visible as a faint band over the mid of the disk.
Beside from the usual brightening of the SPR,possibly a brightening of the NPR is noticeable.
The little movie which I have added,is made from images taken rapidly after each other through the R610 filter.
Here are some further processings from Aug 23. This is were I possibly have captured a hint of NPR-brightening.
(see the arrow in the high contrast image version).It's visible in the color image as a bright spot at the righter side
(west) of the disk,and a bright bulge in the HC image.
[Ralf Vandebergh:Neighbourhood of Maastricht Netherlands]
Over the last few days I told you about Arnoud van Kranenburg
who send you his images of Venus for placement.He also did
write to you at least 4 emails on 3 following days.Can you please
tell me why this problem hasn't been solved.
Unauthorized use prohibited
[copyright(c) Willem Kivits:Siebengewald Netherlands]
Frank J Melillo(Celestron 203mm Schmidt Starlight Xpress MX-5)|
[Frank J Melillo Holtsville NY U.S.A]
Just as we near the end of the hurricane season in the Atlantic Ocean, winds whirl and clouds churn 2 billion miles away in the atmosphere of Uranus, forming a dark vortex large enough to engulf two-thirds of the United States.
Hubble Space Telescope(2900mm fl=5300mm)|
Lawrence Sromovsky of the University of Wisconsin-Madison leads a team that used NASA's Hubble Space Telescope to take the first definitive images of a dark spot on Uranus. The elongated feature measures 1,100 miles by 1,900 miles (1,700 kilometers by 3,000 kilometers).
There have been prior unconfirmed sightings of dark spots on Uranus, including sketches made in the early 1900s, low-contrast ultraviolet Voyager spacecraft flyby images in 1986, and near-infrared observations taken from a ground-based observatory in 1993. However, no other Hubble images taken almost every summer from 1994 through early 2006 have shown such a dark spot. This indicates that the current dark disturbance probably formed very recently, researchers said.
Although rare on Uranus, dark spots have been frequently observed on Neptune. Uranus is similar in size and atmospheric composition to Neptune, but it has not appeared to have as active an atmosphere. Recently, however, Uranus's atmosphere has shown an increase in activity.
The development of a dark spot may be a signal of the oncoming uranian northern spring, said researchers. Uranus is approaching its December 2007 equinox, when the Sun will shine directly over the equator. "We have hypothesized that Uranus might become more Neptune-like as it approached its equinox," said team member Heidi B. Hammel of the Space Science Institute in Boulder, Colo. "The sudden appearance of this unusual dark feature suggests we might be right."
The dark spot was detected at a latitude of 27 degrees in Uranus's northern hemisphere, which is just now becoming fully exposed to sunlight after many years of being in shadow. Astronomers are keenly interested in how strongly and quickly the atmosphere of Uranus seems to be responding to seasonal sunlight changes.
Uranus's rotation axis is tilted almost parallel to its orbital plane, such that the planet appears to be rotating on its side. This sideways orientation leads to extreme seasons during the planet's 84-year path around the Sun.
This three-wavelength composite image was taken with Hubble's Advanced Camera for Surveys on August 23, 2006. The research team found the dark spot again on August 24. The inset image shows a magnified view of the spot with enhanced contrast. Uranus's north pole is near the 3 o'clock position in this image. The bright band in the southern hemisphere is at 45 degrees south.
[NASA/JPL/Space Science Institute]