New Horizons crosses paths with Neptune on way to Pluto
In an unusual coincidence, NASA’s Pluto-bound New Horizons probe, now an estimated 2.75 billion miles from Earth, crossed the orbit of the ice giant Neptune on August 25, 2014 – 25 years to the day that the Voyager 2 spacecraft conducted its closest flyby of the Neptune system. The space agency responsible for both of these iconic missions, detailed, how with each passing mile, New Horizons was making history.
NASA celebrated both missions with a two-hour media event featuring two panel discussions, one by the New Horizons team, who speculated about what might be seen at Pluto next year, and the other by members of both mission teams, who compared their experiences exploring new worlds in 1989 and today.
While New Horizons launched eight years and eight months ago, on January 19, 2006, team members began planning the mission at the time of the Neptune flyby.
Most remained on the team since those early days. Several noted they worked on the Voyager team as young scientists or graduate students and now are senior scientists once again on the brink of exploring a new world.
Built at the Johns Hopkins University Applied Physics Lab (JHUAPL), New Horizons is much smaller than the Voyagers, measuring about the size of a grand piano. It has seven of the most sophisticated scientific instruments ever launched on a spacecraft that will send back detailed images and information about Pluto and its five known moons.
The fastest spacecraft ever launch, New Horizons left the Earth at a speed of 36,256 miles per hour (58,348 kilometers) and crossed the Moon’s orbit in nine hours. Thirteen months after launch, in February 2007, it arrived at Jupiter, testing its instruments by imaging the giant planet and its icy moon Io.
A gravity assist from Jupiter sped up the spacecraft and put it on a trajectory to Pluto. It crossed the orbit of Saturn in June 2008 and the orbit of Uranus in March 2001.
The $700 million mission will make its closest approach to Pluto on July 14, 2015 at 7:49:59 a.m. EDT (1149:59 GMT), flying 6,200 miles from the small planet’s surface.
Communication with the spacecraft at that distance from Earth will take 4.5 hours each way. Initial images and data will be sent back within days, but it will take until late 2016 for all the flyby data to return.
“What we used to call the outer solar system, where giant planets reside, is actually the middle zone of the solar system. It is the Kuiper Belt that is the third zone, the true outer solar system. And within it, a new class of planet, the dwarfs,” said Dr. Alan Stern, Principal Investigator of New Horizons.
Though theorized for decades, the Kuiper Belt was discovered in 1992. It is a vast region containing billions of comets and an unknown number of small planets like Pluto.
Current plans are for New Horizons to explore one or two small Kuiper Belt Objects (KBOs) after the Pluto flyby. The mission team was granted time of the Hubble Space Telescope to search for such objects in the mission’s path. No specific KBO discoveries were announced at the event.
Jim Green, director of NASA’s Planetary Science Division, noted, “It’s a cosmic coincidence that connects one of NASA’s iconic past outer solar system explorers, with our next out solar system explorer. Exactly 25 years ago at Neptune, Voyager 2 delivered out ‘first’ look at an unexplored planet. Now it will be New Horizons’ turn to reveal the unexplored Pluto and its moons in stunning detail next summer on its way into the vast outer reaches of the solar system.
The New Horizons team released an image of Neptune and Triton taken by New Horizons’ Long range Reconnaissance Imager (LORRI) on July 10 of this year, from a distance of 2.457 billion miles.
Triton and Pluto are believed to have similar histories, meaning Voyager’s findings at Triton could be a preview of features seen on Pluto. Both objects come from the Kuiper Belt. Because Triton has a retrograde orbit around Neptune, it is believed to have once been a planet that orbited the Sun directly, only to have been subsequently captured by Neptune. Both Pluto and Triton are geologically active, slightly smaller than Earth’s moon possess thin, nitrogen-dominated atmospheres, and have various ices on their surfaces.
In anticipation of next year’s findings at Pluto, Dr. Paul Schenk of the Lunar and Planetary Institute in Houston, Texas, made a video of Triton, restoring footage from Voyager to create a new, higher resolution map of the large moon.
Triton surprised scientists because it is a geologically active world, with cryovolcanoes, a varied terrain, bright poles, and an icy surface.
Ralph McNutt at JHUAPL was a member of the Voyager 2 plasma-analysis team and now heads New Horizons’ energetic-particle investigation group.
“There is a lot of speculation over whether Pluto will look like Triton, and how well they will match up,” McNutt said. “That’s the great thing about first-time encounters like this — we don’t know exactly what we’ll see, but we know from decades of experience in first-time exploration of new planets that we will be very surprised.”
Video Courtesy of USRA Houston
Pluto is known to have a mass of 70 percent rock, an escaping atmosphere composed primarily of nitrogen, winds, polar caps, a surface that has changed over time, and a large moon — Charon.
Pluto and Charon are sometimes considered a binary planet system because both orbit a common center of gravity outside Pluto.
“The U.S. has led the exploration of the planets and space to a degree no other nation has, and continues to do so with New Horizons,” Stern emphasized. “We’re incredibly proud that New Horizons represents the nation again as NASA breaks records with its newest, farthest and very capable planetary exploration spacecraft.”
The first panel included Green, director of NASA’s Planetary Division of the Science Mission Directorate; Ed Stone of the California Institute of Technology in Pasadena, California and Voyager Project Scientist; and Stern, of the Southwest Research Institute in Boulder, Colorado.
The session that followed was moderated by Dr. David Grinspoon of the Planetary Science Institute in Tucson, Arizona. Panelists included Fran Bagenal of the University of Colorado at Boulder; Bonnie Buratti of NASA’s Jet Propulsion Lab in Pasadena, California; Jeffrey Moore of the NASA Ames Research Center, Moffett Field, California; and John Spencer of the Southwest Research Institute, Boulder, Colorado.
Laurel Kornfeld is an amateur astronomer and freelance writer from Highland Park, NJ, who enjoys writing about astronomy and planetary science. She studied journalism at Douglass College, Rutgers University, and earned a Graduate Certificate of Science from Swinburne University’s Astronomy Online program. Her writings have been published online in The Atlantic, Astronomy magazine’s guest blog section, the UK Space Conference, the 2009 IAU General Assembly newspaper, The Space Reporter, and newsletters of various astronomy clubs. She is a member of the Cranford, NJ-based Amateur Astronomers, Inc. Especially interested in the outer solar system, Laurel gave a brief presentation at the 2008 Great Planet Debate held at the Johns Hopkins University Applied Physics Lab in Laurel, MD.