Hubble Captures Rare Transit of Moons Across Jupiter
Hubble Telescope Images of Jupiter
Capture Unusual View of Three Moons Crossing Its Face: Europa, Callisto and Io
By Gautam Naik in the Wall Street
Journal
New images from the Hubble space
telescope show three of Jupiter’s largest moons moving across the face of the
planet at the same time, a rare occurrence that happens only once or twice a
decade.
The moons of Jupiter are often seen
moving across Jupiter’s banded face and casting shadows on the layers of clouds
below. But on Jan. 23, the Hubble telescope snagged the unusual view of three
in the same frame. The moons in the photographs are Europa, Callisto and Io.
Jupiter and its moons have long been
a source of fascination for astronomers. The planet has 50 moons, though many
are small orbs. But one of them, Ganymede, is bigger than the planet Mercury
and the largest moon in the solar system.
In 1610, Galileo Galilei observed
Jupiter’s four largest moons through a homemade telescope. His realization that
the moons weren’t stars but planetary bodies in orbit around Jupiter provided
evidence to support the Copernican system, revealing that not every planetary
body revolved around the Earth. His findings challenged the Catholic Church’s
beliefs and led to Galileo being put on trial for heresy and imprisoned.
Now astronomers are once again
setting their sights on the planet. The National Aeronautics and Space
Administration is asking for $30 million in
its fiscal year 2016 budget request
to plan a mission to Jupiter’s moon Europa, a planetary body that many
astrobiologists believe could have a “habitable zone” and therefore the
potential to harbor some form of life.
Europa’s surface is mostly water
ice, and there also appears to be a vast ocean of water or slushy ice beneath
it. In all, the moon could have twice the amount of water as Earth. Scientists
note that because life has been found in some of Earth’s extreme
environments—near undersea volcanoes, for example—similar harsh locations on
Europa may also harbor life.
NASA is asking for $30 million in
its fiscal year 2016 budget request to plan a mission to Jupiter's moon Europa
which it calls one of the most likely places to find current life beyond Earth.
WSJ's Monika Auger reports.
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