New Horizons On The Way To Pluto
The nuclear powered New Horizons interplanetary probe designed to study Pluto, the Solar System's farthest known (dwarf) planet, was blasted off on an Atlas 5 rocket from Cape Canaveral Air Force Station, Florida, on January 19, 2006.
Image Left: On its way to Pluto, the New Horizons spacecraft flies by the planet Jupiter in this artist's rendering by the Southwest Research Institute and Johns Hopkins University Applied Physics Laboratory. Tiny specks of light near the distant Sun are Earth, Venus and Mercury. The dim crescent shape at the upper right of the Sun is Callisto, the outermost of Jupiter's four largest moons. Just left of Jupiter is its moon Europa.
The flight will take New Horizons across more than three billion miles of deep space to Pluto by 2015 because flight controllers are able to use a time-saving slingshot effect gained from a Jupiter flyby. The spacecraft passed the planet Jupiter in February 2007, just 13 months after launch. The assist from the big planet's gravity will speed up the probe on its way out to Pluto.
The piano-sized spacecraft is about 8 feet wide and weighs half a ton - 1,025 pounds - at the outset with a full load of fuel.
New Horizons is on the fastest spacecraft trip ever to the outer Solar System. It reached the orbit of Earth's Moon in fewer than 9 hours, and then hustled off toward Jupiter. It passed by Jupiter from February 25 to March 2, 2007.
The interplanetary cruise will extend through June 2015 when New Horizons will arrive at the Pluto system for a five-month-long reconnaissance flyby of the planet, its moon Charon and two other unnamed moons just discovered in 2005.
In 2015, Pluto will be about 3.1 billion miles from Earth. Initially scientists thought Charon was Pluto's only moon. Now, astronomers, using the Hubble Space Telescope, have observed two additional moons around Pluto. The new moons announced in 2005 are said to be 5,000 times fainter than Pluto. Including the planet, the total number of objects known to be in that vicinity is four. Click here to learn about the moons of Pluto.
Beyond Pluto. After touring the Pluto system, New Horizons will fly on out, farther away from the Sun, into the zone of space known as the Kuiper Belt to examine one or two of the ancient, icy mini-worlds in that vast region a billion or more miles beyond Pluto's orbit. That journey will span 2016-2020. (Watch for a posting about the fascinating Kuiper Belt in an upcoming What's Up in Space.)
Far, far away. A radio signal moving at the speed of light takes about four hours to reach Pluto from Earth, or to reach Earth from Pluto.
Data from New Horizons will be received by radio on Earth using NASA's Deep Space Network antennas. It then will be sent to the spacecraft's Mission Operations Center at Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland. APL built the New Horizons spacecraft for NASA and manages the mission.
Electrical power. The spacecraft has a nuclear power supply to generate electricity over its many years of life.
Plutonium-238 fuel is used to power a radioisotope thermal generator (RTG), which is the probe's long-life battery. An RTG converts heat from naturally decaying plutonium into electricity.
The RTG uses plutonium dioxide ceramic pellets as a heat source and solid-state thermocouples that convert the plutonium's heat energy to electricity.
Pluto rings? Astronomers are wondering if they will see rings around Pluto when New Horizons arrives on the scene. Fine debris kicked up by objects hitting Pluto may have been captured in orbit around the planet.
Each of the four giant gas planets in the outer Solar System - Jupiter, Saturn, Uranus, and Neptune - is orbited by rings of dust and small particles of matter. Saturn is most famous for its rings.
The astronomer Galileo saw Saturn's rings first in 1610. The interplanetary probe Voyager 1 found Jupiter's ring in 1974. The Uranian ring system was discovered in 1977 during observations from Earth. Suspected since the 1980s, the probe Voyager 2 verified rings around Neptune in 1989. Click here to learn more about rings around planets.
Image Right: New Horizons encounters Pluto and Charon in this artist's rendering by Johns Hopkins University Applied Physics Laboratory and Southwest Research Institute. The largest structure on the spacecraft is the 7-foot dish antenna through which it communicates with Earth from more than 3 billion miles or farther away. The miniature cameras, radio science experiment, ultraviolet and infrared spectrometers and space plasma experiments measure the global geology and geomorphology of Pluto and its moons, mapping surface compositions and temperatures, and examining Pluto's atmosphere.
Science tools. New Horizon has seven scientific instruments with cute acronym names made up by their designers:
- Alice is an ultraviolet spectrometer measuring gas composition
- Ralph combines an infrared spectrometer (LEISA) mapping surface composition with a color optical imager (MVIC) mapping surface structure and composition
- REX is a radio experiment measuring atmospheric composition and temperature
- LORRI is an optical telescope for the highest resolution imaging of the surface
- PEPSSI is a plasma-sensing instrument measuring particles escaping from Pluto's atmosphere
- SWAP is a plasma-sensing instrument measuring the properties of the solar wind* at Pluto and Pluto's atmospheric escape rate, and searching for a magnetosphere around Pluto.
- SDC is an instrument measuring dust impacts on the New Horizons spacecraft during its entire flight. It was built by students at the University of Colorado in Boulder.
* Solar wind is a stream of charged particles leaving the Sun and traveling outward across the Solar System at high speed.
Searching for more moons. As evidenced by the Hubble discovery of two additional moons around Pluto, New Horizons astronomers have been using telescopes on Earth and in Earth-orbit to hunt for other moons orbiting Pluto.
The Hubble Space Telescope orbiting Earth is able to see natural satellites of Pluto as small as 6.2 miles in diameter. As it approaches the planet, the New Horizons spacecraft should be able to detect moons around Pluto only one-tenth that size - 0.62 miles in diameter.
Pluto at last. Pluto is the only planet in our Solar System never visited by a spacecraft from Earth. A successful New Horizons trip will change that.
Believe it or not, NASA actually argued against sending a probe to the distant world, but planetary scientists across the country said it was important to go now while Pluto remains in a favorable position and before its surface becomes more frozen as it moves farther away on its long orbit around the Sun.
Some astronomers have suggested Pluto should not be considered a planet, but a Kuiper Belt Object instead. In 2006, it demoted Pluto to dwarf planet. That left only eight major planets in the Solar System and a great deal of public frustration.
Plutoids. The IAU (International Astronomical Union) astronomers thought and thought, and in 2008 came up with the label plutoid for all dwarf planets lying beyond Neptune.
IAU defines plutoid as a type of dwarf planet that orbits the Sun at a distance greater than Neptune and has enough mass for its self-gravity to give it a near-spherical shape.
Astronomers wanted to distinguish between rocky dwarf planets like Ceres, which is closer to the Sun in the asteroid belt between Mars and Jupiter, and icy dwarf planets like Pluto. Get the whole story about Pluto's demotion by clicking here.
About Pluto...
- Pluto is named after the Greek god of the underworld.
- PL, the astronomical symbol for Pluto, is a tribute to Percival Lowell, who started the search for the ninth planet in the early 1900s.
- Pluto was discovered in 1930 by American astronomer Clyde Tombaugh.
- Pluto's orbit averages 3.7 billion miles (5.9 billion km or 39.5 AU) from the Sun.
- At 1,470 miles (about 2,370 kilometers) diameter, Pluto could fit between Washington, D.C., and Denver, Colorado.
- Pluto orbits the Sun once every 248 years.
- A person on Pluto would weigh 1/15 what she or he would weigh on Earth. By comparison, astronauts on the Moon had 1/6 of their Earth weight.
- Pluto is an ice dwarf, a new kind of planet found in the far outer reaches of our Solar System.
- Pluto has weather, winds, hazes, chemistry and an ionosphere.
- Pluto's surface has nitrogen, methane and carbon monoxide ices on it.
- Pluto's estimated surface temperature ranges from -378°F to -396°F (-228°C to -238°C).
- Pluto is one of two planets that rotate on their sides. Uranus is the other.
- A radio signal, moving at the speed of light, takes about 4 hours to reach Pluto from Earth or Earth from Pluto.
About Charon...
- Charon is named after the mythological boatman who ferried souls across the river Styx to Pluto for judgment.
- American astronomers James Christy and Robert Harrington discovered Charon in 1978.
- Charon is half of Pluto's diameter, making it the largest satellite relative to the planet it orbits.
- Charon is 20 times closer to Pluto than our Moon is to Earth.
- Pluto-Charon combine to form the Solar System's only known binary planet.
About the Kuiper Belt...
- The Kuiper Belt is named after Dutch astronomer Gerald Kuiper (1905-73).
- The Kuiper Belt is a collection of icy, rocky objects orbiting the Sun beyond the orbits of the planets Neptune and Pluto.
- Kuiper Belt objects also are known as Trans-Neptunian Objects.
- The first Kuiper Belt Object was discovered in 1992.
- Some Kuiper Belt Objects have an average reddish color, while others are gray.
CREDIT: Johns Hopkins University Applied Physics Laboratory