|In this artist's concept, Pluto and its moon Charon are seen from the surface of one of Pluto's newly discovered candidate satellites. Credit: David A. Aguilar of the Harvard-Smithsonian CfA
The New Horizons mission launched from Cape Canaveral, Florida at 2 p.m. Eastern time this afternoon. The spacecraft is now headed to the planet Pluto, speeding from Earth at 8 miles per second. Because Pluto is so far away, it will take New Horizons nine years to reach its destination.
Pluto is one of the most mysterious objects in our solar system. Ten thousand times fainter than the eye can see, and a hundred times smaller than Mars in the night sky, Pluto has never been investigated up-close by a spacecraft. The best image of Pluto, obtained by the Hubble Space Telescope, is just a crude grouping of bright and dark pixels.
Pluto is different from both the inner rocky planets and the outer gaseous planets. The icy planet is a member of the Kuiper Belt, an enormous disc-shaped region of ice and dust that encircles our solar system. The half-million icy bodies that make up this belt are thought to be over 4 billion years old. Many scientists believe Pluto is just one of many large Kuiper Belt Objects.
Pluto's moon Charon is large enough that some consider the two to be a binary planetary system. Astronomers recently discovered two smaller moons orbiting more than twice as far away as Charon. The goal of the New Horizons mission is to map the sunlit portions of Pluto, Charon, and these newly discovered satellites.
|George Wetherill of the Carnegie Institution of Washington has suggested that without Jupiter and Saturn, there would be many more comets in the Kuiper Belt (shown above).
After visiting Pluto, Charon, and the two newly discovered moons, an extended mission would allow the New Horizons spacecraft to encounter one or two Kuiper Belt Objects (KBOs). Because the Kuiper Belt is so vast, the closest KBO to Pluto is about 1 AU away, the same distance between the Earth and the sun.
The spacecraft has seven science instruments -- three are cameras, while three others will measure solar wind, space dust, and energetic particles. A radio instrument will measure Pluto's surface temperatures and atmosphere.
The spacecraft also has a CD-ROM inscribed with about half a million names of people who signed up on the Internet. A nuclear power supply will generate electricity during the long mission.
In early 2007, a flyby of Jupiter will increase the spacecraft's speed by an additional 2.5 miles per second. The spacecraft should reach Pluto by mid-2015.
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