Hubble's Planetary Discoveries
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Watching the weather patterns on the giant outer planets (Jupiter, Saturn, Uranus, and Neptune) has been an ongoing activity throughout Hubble’s lifetime.
Jupiter's monster storm, the Great Red Spot, was once so large that three Earths would fit inside it. But new measurements by Hubble reveal that the largest storm in our solar system has downsized significantly. The Red Spot, which has been raging for at least a hundred years, is now only the width of one Earth. The storm images were taken in 1995, 2009, and 2014. The images were taken with Wide Field and Planetary Camera 2 (1995) and Wide Field Camera 3.
The large Wide Field Camera 2 image of Jupiter was obtained in 2007, with its moon, Ganymede, just emerging from behind the planet.
The semi-major axis of Jupiter's orbit about the Sun is 5.2 astronomical units (483 million miles or 778 million km). The planet has a diameter of roughly 88,789 miles (142,984 km) at the equator.
This image of Europa is derived from a global surface map generated from combined NASA Voyager and Galileo space probe observations. The graphic shows the location of water vapor detected over Europa's south pole by Hubble in December 2012. The Hubble observations provide the best evidence to date of water plumes erupting off Europa's surface. Hubble didn't photograph plumes, so the plume and the illustration in the center are artist’s conceptions. However, Hubble observers used the Space Telescope Imaging Spectrograph to spectroscopically detect auroral emissions from oxygen and hydrogen. The aurora is powered by Jupiter's magnetic field. This is only the second moon in the solar system found ejecting water vapor from the frigid surface. Another of Jupiter’s moons, Ganymede, is also likely to have a subsurface ocean.
Europa is the sixth closest Jovian moon. It is the smallest of the four Jovian satellites discovered by Galileo Galilei, but still the sixth largest moon in the Solar System. Europa was discovered by Galileo in 1610.
Images taken in ultraviolet light by Hubble’s Space Telescope Imaging Spectrograph (STIS) show both Jupiter auroras in 1998, the oval-shaped objects in the inset photos. Ground-based telescopes cannot view these phenomena in ultraviolet light, as it is blocked by the Earth’s atmosphere.
Auroras are curtains of light resulting from high-energy electrons racing along the planet's magnetic field into the upper atmosphere. The electrons excite atmospheric gases, causing them to glow.
The electric-blue image of Jupiter’s northern aurora shows the main oval of the aurora, which is centered on the magnetic north pole, plus more diffuse emissions inside the polar cap. Though the aurora resembles the same phenomenon that crowns Earth's polar regions, the blue Hubble image shows unique emissions from the magnetic "footprints" of three of Jupiter's largest moons. (These points are reached by following Jupiter's magnetic field from each satellite down to the planet). Jupiter has at least 68 moons. Auroral footprints can be seen in this image from Io (along the left-hand limb), Ganymede (near the center), and Europa (just below and to the right of Ganymede's auroral footprint). These emissions, produced by electric currents generated by the satellites, flow along Jupiter's magnetic field, bouncing in and out of the upper atmosphere. They are unlike anything seen on Earth.
This ultraviolet image of Jupiter was taken with the Hubble Space Telescope Imaging Spectrograph (STIS) on November 26, 1998. In this ultraviolet view, the aurora stands out clearly, but Jupiter's cloud structure is masked by haze.
Saturn’s aurora was observed with Hubble in 2005. Images were obtained with the Advanced Camera for Surveys in the optical and STIS in the ultraviolet. The aurora appeared in Saturn’s southern polar region for several days. Hubble snapped a series of photographs of the aurora dancing in the sky. The snapshots show that Saturn's auroras differ in character from day to day -- as they do on Earth -- moving around on some days and remaining stationary on others. But compared with Earth, where auroral storms develop in about 10 minutes and may last for a few hours, Saturn's auroral displays always appear bright and may last for several days.
Recently, NASA’s New Horizons mission imaged Pluto and two of its moons, Nix and Hydra, which were discovered by Hubble in 2005. Peering out to the dim, outer reaches of our solar system beyond Pluto, Hubble uncovered three Kuiper Belt objects (KBOs) that the agency's New Horizons spacecraft could potentially visit after it flies by Pluto in July 2015. The KBOs were detected through a dedicated Hubble observing program by a New Horizons search team that was awarded telescope time for this purpose.
The lower set of Pluto images shows Hubble Space Telescope data from the Advanced Camera for Surveys exhibiting an icy, mottled, dark molasses-colored world undergoing seasonal surface color and brightness changes. Pluto has become significantly redder, while its illuminated northern hemisphere is getting brighter. These changes are most likely consequences of surface ice melting on the sunlit pole and then refreezing on the other pole, as the dwarf planet heads into the next phase of its 248-year-long seasonal cycle. Analysis shows the dramatic change in color took place from 2000 to 2002. Note that Hubble found four of Pluto’s five moons – Nix, Hydra, Styx and Kerberos.
http://hubblesite.org/newscenter/archive/releases/2014/47/full/ http://hubblesite.org/newscenter/archive/releases/solar-system/pluto/2010/06/ http://hubblesite.org/newscenter/archive/releases/solar-system/pluto/2012/32/
and related links
http://www.nasa.gov/nh_new-horizons-spots-small-moons-orbiting-pluto/#.VPnlP2TF_b4 http://pluto.jhuapl.edu/
Other outer solar system objects:
Eris is 1.27 times the mass of Pluto, and formerly the largest member of the Kuiper Belt of icy objects beyond Neptune. Hubble observations in 2006 showed that Eris is slightly physically larger than Pluto. But the mass could only be calculated by observing the orbital motion of the moon Dysnomia around Eris. Multiple images of Dysnomia's movement along its orbit were taken by Hubble and Keck.
http://hubblesite.org/newscenter/archive/releases/solar%20system/2007/24/image/c/format/web/
Also in 2002, Hubble measured a large object discovered in the outer solar system. It was the largest outer solar system object discovered since Pluto and was superseded by the observation of Eris. Approximately half the size of Pluto, the icy world is called "Quaoar" (pronounced kwa-whar). Quaoar is about 4 billion miles away, more than a billion miles farther than Pluto. Like Pluto, Quaoar dwells in the Kuiper belt, an icy belt of comet-like bodies extending 7 billion miles beyond Neptune's orbit.
The upper image, taken by Hubble, reveals the orbital motion of the planet Fomalhaut b. Based on these observations, astronomers calculated that the planet is in a 2,000-year-long, highly elliptical orbit around its parent star, Fomalhaut. The planet will appear to cross a vast belt of debris around the star roughly 20 years from now. If the planet's orbit lies in the same plane with the belt, icy and rocky debris in the belt could crash into the planet's atmosphere. The black circle at the center of the image is caused by a device called a coronograph, which blocks out the otherwise overwhelming light from the bright star and allows reflected light from the belt and planet to be photographed. The Hubble images were taken with the Space Telescope Imaging Spectrograph in 2010 and 2012.
Fomalhaut is 25 light years (8 parsecs) away.
http://hubblesite.org/newscenter/archive/releases/2013/01/
The lower graphic demonstrates Hubble’s first detection ever of an organic molecule in the atmosphere of a Jupiter-sized planet orbiting another star. This breakthrough is an important step toward eventually identifying signs of life on a planet outside our solar system. The molecule found by Hubble is methane, which under the right circumstances can play a key role in prebiotic chemistry — the chemical reactions considered necessary to form life as we know it. The graphic shows a spectrum of methane with the configuration of the star and the planet (not to scale) in relation to Hubble. The object is 63 light years (19 parsecs) away.