Monthly Archives: November 2004

galaxies, hubble space telescope

More Than Meets The Eye

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Courtesy STScI
Courtesy STScI

A long time ago I wrote a planetarium show called More Than Meets The Eye about all the things you can see in the sky if you look with your naked eye and then enhance the view with binoculars and telescopes. Everywhere you look in the night sky you can see stars, but if you magnify the view, you can see nebulae and galaxies, details on planets and in comet tails, and even small little chunks of rock called asteroids.

The Hubble Space Telescope gives us magnified views of the universe every day. In recent weeks it spotted a small asteroid wending its way through the field of view as the telescope was studying a small companion to the Milky Way called the Sagittarius Dwarf Irregular Galaxy. You can see the trail of the asteroid as it traveled across HST’s view. The wavy path is not the actual path of the asteroid—it doesn’t actually wander quite that frenetically. It’s wandering a bit because the telescope is a) moving, and b) several different images were taken over a period of time. That’s why the trail looks interrupted and not quite straight.

What I find fascinating is the field of stars and galaxies that the HST image also shows. If you look closely you’ll see a few distant spirals, some edge-on galaxies, and some other blobs of light that are either too distant or too faint to make out good shapes. The scattering of stars across the top of the image is part of the dwarf galaxy the scientists were after when they took the images. It’s about 3.5 million light-years away, while the most distant galaxies in the image are at least a hundred million light-years away. The asteroid, on the other hand, is about 169 million miles away from us. It’s quite a panoramic view of the cosmos in one image—and definitely MORE than meets the eye!

planetary science

You Can Never Be Too Thin or Too Gaseous

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Near infrared images of Uranus before and after the AO system on Keck was turned on. The images on the left show Uranus at K (2.2 micron) and H (1.6 micron) bands as we saw the planet before Keck was equipped with Adaptive Optics. On the right you see the improvement in image quality (sharpening) after the AO system was turned on. (Image credit: Heidi B. Hammel and Imke de Pater)
Near infrared images of Uranus before and after the AO system on Keck was used (Image credit: Heidi B. Hammel and Imke de Pater)

What’s the latest at Uranus? According to Professor Imke de Pater (University of California, Berkeley) and Heidi Hammel (Space Science Institute), the 7th planet out from the Sun is not the boring and unchanging planet everybody thinks it is. The weather’s changing as the southern hemisphere summer at Uranus comes to a close. There are more clouds in the upper atmosphere than scientists saw when Voyager first approached the planet back in 1986. This is due to high-altitude cloud activity perpetrated by strong convection currents in the atmosphere. If you look at the planet with infrared-enabled instruments, those clouds really stand out. And, as an added bonus, there’s a newly discovered dim ring to be checked out. This new one, called 1986U2R, is—like the other rings in the system—only only a single layer of boulder-sized particles thick. That’s downright diaphanous by ring standards!

These discoveries weren’t made with a flyby spacecraft. Instead, the Uranus observation teams have been using the Keck telescope out on Mauna Kea (Hawaii), and the careful application of adaptive optics (a method to “erase” the effects of atmospheric aberration from ground-based observations).

What’s next for Uranus as the seasons change? Maybe more clouds will bubble their way up from the depths of the planet’s atmosphere. Nobody’s quite sure, since this is the first time the planet’s seasons have changed since high-resolution telescopes like the Keck and others have been in use.