The image above is an artist’s impression of Pluto’s surface and atmosphere commissioned by NASA just a few years ago. Today, however, this visionary image will no longer be needed as the day that millions of people around the world have been waiting for has finally arrived: NASA’s spacecraft “New Horizons” is completing its historic flyby mission to take the closest pictures of Pluto that any human has ever seen.
— NASA New Horizons (@NASANewHorizons) July 14, 2015
“After a voyage of nearly nine years and three billion miles —the farthest any space mission has ever traveled to reach its primary target – NASA’s New Horizons spacecraft came out of hibernation today for its long-awaited 2015 encounter with the Pluto system,” NASA announced not long ago in a statement on December 6, 2014, when the spacecraft “woke up” after 1,873 days in hibernation mode.
New Horizons was launched on January 19, 2006, at a velocity of 36,373 mph (58,536 km/h) – the fastest spacecraft to ever leave Earth orbit, 100 times faster than a jetliner – and has since traveled 2.9 billion miles from Earth.
Pluto, known as the largest body of the Kuiper Belt (even though smaller than our moon), is the last planet (now considered a dwarf-planet) in our solar system that has so far not been explored. NASA fittingly calls it the final chapter in “a five-decade-long era of reconnaissance,” which began in the early 1960s with the exploration of Venus and Mars, followed by Mercury, Jupiter, and Saturn in the 1970s and finally Uranus and Neptune in the 1980s. Kuiper Belt objects, such as Pluto, preserve evidence about the early formation of the solar system.
Today, as of 7:49 AM EDT on Tuesday, July 14, history is being made. At this very moment, New Horizons is within merely 7,750 miles of Pluto to take the first high-resolutions close-up pictures of the dwarf-planet.
“Every once in a while, a photo comes along that has the ability to shift not just how we see our place in the universe, but how we see ourselves — not just as Americans, but as citizens of Earth,” said Dr. John P. Holdren, director at the White House Office of Science and Technology Policy.
“The exploration of Pluto and its moons by New Horizons represents the capstone event to 50 years of planetary exploration by NASA and the United States,” said NASA Administrator Charles Bolden. “Once again we have achieved a historic first. The United States is the first nation to reach Pluto, and with this mission has completed the initial survey of our solar system, a remarkable accomplishment that no other nation can match.”
To commemorate the occasion and take the discovery experience to the next level, NASA is providing the general public with a live feed of the Pluto flyby via their NASA TV channel right here.
“Nothing like this has been done in a quarter-century, and nothing like this is planned by any space agency, ever again,” says New Horizons principal investigator, Alan Stern, about the significance of today’s event.
New Horizons is gathering roughly 100 times as much data as it can send home before flying away. Even though it will send crucial, high-level data back to Earth within days of the mission, it will continue to return datasets stored in onboard memory for another 16 months.
This includes mapping the geology of Pluto and its largest moon “Charon,” their surface composition, temperature, and atmosphere, as well as a study of Pluto’s smaller satellites and potential rings around the dwarf planet.
“After nearly 15 years of planning, building, and flying the New Horizons spacecraft across the solar system, we’ve reached our goal,” said project manager Glen Fountain at APL “The bounty of what we’ve collected is about to unfold.”
Another way of experiencing the flyby and continuing to follow New Horizons and other spacecrafts currently out in space is NASA’s interactive app called “Eyes on Pluto,” which lets you ride onboard the spacecraft and explore what its instruments can see in real time. You can download and activate the desktop app right here.
“This mission also opens the door to an entirely new “third” zone of mysterious small planets and planetary building blocks in the Kuiper Belt, a large area with numerous objects beyond Neptune’s orbit,” NASA confirmed about New Horizons’ on-going path once the spacecraft finished its Pluto mission.
New Horizons Project Scientist Hal Weaver at APL concluded that, “New Horizons is one of the great explorations of our time. There’s so much we don’t know, not just about Pluto, but other worlds like it. We’re not rewriting textbooks with this historic mission – we’ll be writing them from scratch.”
Leading up to July 14, here is what NASA has learned about Pluto and shared on the official New Horizons blog.
New Horizons is the fastest spacecraft ever launched. It is equipped with a total of seven science instruments, including advanced imaging infrared and ultraviolet spectrometers, a space-dust detector, a high-resolution telescopic camera, and two powerful particle spectrometers. The spacecraft has a relative velocity of 30,800 mph at its approach to Pluto.
“The size of Pluto has been debated since its discovery in 1930. We are excited to finally lay this question to rest,” said mission scientist Bill McKinnon, Washington University, St. Louis, about the fact that measuring Pluto’s size has been a challenge due to complicating factors from its atmosphere.
The result? Pluto is 1,473 miles (2,370 kilometers) in diameter, larger than many prior estimates. Images used to make this determination were acquired with the Long Range Reconnaissance Imager (LORRI) camera.
Pluto’s newly estimated size means that its density is slightly lower than previously thought, and the fraction of ice in its interior is slightly higher. Also, the lowest layer of Pluto’s atmosphere, called the troposphere, is shallower than previously believed.
Its largest moon Charon lacks a substantial atmosphere, and its diameter was easier to determine (than Pluto’s) using ground-based telescopes. New Horizons observations of Charon confirm previous estimates of 751 miles (1208 km) across.
LORRI also zoomed in on two of Pluto’s smaller moons, Nix and Hydra.
Nix and Hydra were discovered using the Hubble Space Telescope in 2005. Even to Hubble, they appeared as points of light, and that’s how they looked to New Horizons until the final week of its approach to Pluto. Now, the latest LORRI images show the two diminutive satellites not as pinpoints, but as moons seen well enough to measure their sizes. Nix is estimated to be about 20 miles (about 35 km) across, while Hydra is roughly 30 miles (roughly 45 km) across. These sizes lead mission scientists to conclude that their surfaces are quite bright, possibly due to the presence of ice.
Smaller and fainter than Nix and Hydra, Pluto’s two smallest moons Kerberos (orbits Pluto every 32 days) and Styx (circles Pluto every 20 days) are harder to measure. Mission scientists should be able to determine their sizes with observations New Horizons makes during the flyby today and will transmit to Earth at a later date.
How Similar are Pluto and Charon to the Earth and the Moon?
In this video, NASA explores how Pluto and its moon compare to Earth and our moon:
Images Leading Up to Today’s Flyby
As NASA’s unmanned New Horizons spacecraft was speeding closer to the historic July 14 Pluto flyby, it was producing more and more images of the icy world that has been growing more fascinating and complex every day. Here are a few of them.
July 13, 2015 – Pluto’s bright, mysterious “heart” is rotating into view, ready for its close-up on close approach, in this image taken by New Horizons on July 12 from a distance of 1.6 million miles (2.5 million kilometers). It is the target of the highest-resolution images that will be taken during the spacecraft’s closest approach to Pluto on July 14. The intriguing “bulls-eye” feature at right is rotating out of view, and will not be seen in greater detail.
On July 11, 2015, New Horizons captured this image, which suggests some new features that are of keen interest to the Geology, Geophysics and Imaging (GGI) team now assembled at the Johns Hopkins University Applied Physics Lab in Laurel, Maryland. For the first time on Pluto, this view reveals linear features that may be cliffs, as well as a circular feature that could be an impact crater. Just starting to rotate into view on the left side of the image is the bright heart-shaped feature that will be seen in more detail during New Horizons’ closest approach.
These images were taken between April 25 and May 1, revealing Kerberos and Styx – the smallest and faintest of Pluto’s five known moons. They marked the first time New Horizons had photographed those two moons, which were discovered in 2011 and 2012, respectively, by New Horizons team members using the Hubble Space Telescope.
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