Atmospheric features on Uranus and Neptune are revealed in images
taken with the Space Telescope Imaging Spectrograph and the
Advanced Camera for Surveys aboard NASA’s Hubble Space Telescope.
A wider view of Uranus reveals the planet’s faint rings and several
of its satellites. The observations were taken in August 2003.

Uranus and Neptune:

The top row reveals Uranus and Neptune in natural colors, showing
the planets as they would appear if we could see them through a
telescope. The images are made of exposures taken with filters
sensitive to red, green, and blue light. In the bottom images,
astronomers used different color filters to detect features we can’t
see. The photographs demonstrate that, by using certain types of
color filters, astronomers can extract more information about a
celestial object than our eyes normally can see.

At first glance, the top row of images makes the planets appear like
twins. But the bottom row reveals that Uranus and Neptune are two
different worlds. Uranus’s rotational axis, for example, is tilted
almost 90 degrees to Neptune’s axis. The south poles of Uranus and
Neptune are at the left and bottom, respectively. Both are tilted
slightly toward Earth. Uranus also displays more contrast between
both hemispheres. This may be caused by its extreme seasons.

Both planets display a banding structure of clouds and hazes aligned
parallel to the equator. Additionally, a few discrete cloud features
appear bright orange or red. The color is due to methane absorption
in the red part of the spectrum. Methane is third in abundance in the
atmospheres of Uranus and Neptune after hydrogen and helium, which
are both transparent. Colors in the bands correspond to variations in
the altitude and thickness of hazes and clouds. The colors allow
scientists to measure the altitudes of clouds from far away.

Uranus (A Wider View):

This wider view of Uranus reveals the planet’s faint rings and several
of its satellites. The area outside Uranus was enhanced in brightness
to reveal the faint rings and satellites. The outermost ring is brighter
on the lower side, where it is wider. It is made of dust and small
pebbles, which create a thin, dark, and almost vertical line across the
right side of Uranus (especially visible on the natural-color image).

The bright satellite on the lower right corner is Ariel, which has a
snowy white surface. Five small satellites with dark surfaces can be
seen just outside the rings. Clockwise from the top, they are:
Desdemona, Belinda, Portia, Cressida, and Puck. Even fainter satellites
were imaged in deeper exposures, also taken with the Advanced Camera in
August 2003.

Image credit: NASA and Erich Karkoschka, University of Arizona

Electronic image files and additional information are available at:

The Space Telescope Science Institute (STScI) is operated by the
Association of Universities for Research in Astronomy, Inc. (AURA),
for NASA, under contract with the Goddard Space Flight Center,
Greenbelt, MD. The Hubble Space Telescope is a project of
international cooperation between NASA and the European Space
Agency (ESA).