The Ninth Celestial

T he

Ni

n

th

e s l tial e C

A Small History of the nine year mission to the dwarf planet pluto

1 The Ninth Celestial | New Horizons

American astronomer Clyde Tombaugh discovered Pluto, the ninth planet in our solar system, on February 18th, 1930.

Many key questions about Pluto, its moon Charon, and the outer fringes of our solar system await close-up observations.

The proposed NASA mission called New Horizons, depicted in the artist's concept below, would use miniature cameras, radio science experiments, ultraviolet and infrared spectrometers and space plasma experiments to study Pluto and Charon, map their surface compositions and temperatures, and examine Pluto's atmosphere in detail.

NASA’s New Horizons sped towards the edge of our solar system for a flyby of Pluto on July 14th, 2015. It didn’t make observations alone; NASA’s fleet of observatories were be busy gathering data before and after to help piece together what we know about Pluto, and what features New Horizons data might help explain.

The Ninth Celestial | New Horizons

“NASA is aiming some of our most powerful space observatories at Pluto,” said Paul Hertz, Astrophysics Division Director at NASA Headquarters, Washington. “With their unique capabilities combined, we will have a multi-faceted view of the Pluto system complementary to New Horizons data.”

2

Right around New Horizons’ closest approach to Pluto, Cassini took an image of the dwarf planet from its station in orbit around Saturn. Although Cassini is the closest spacecraft to New Horizons’ distant location, the image of Pluto will be but a faint dot on a field of stars. Even so, the image will provide a scientific measurement of Pluto from a different vantage point that will complement data collected by New Horizons.

3

“We have been waiting for this for along time,” said the Greek native, who now works as a scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “That’s what happenswhen it takes more than nine years to get to your destination.”

Until now, knowledge about the mysterious planet’s atmosphere has come mainly from stellar occultation, when the planet passes in front of bright stars during its highly elliptical-shape orbit around the sun. From these observations, scientists discovered that the planet’s atmosphere resembled that of Neptune’s moon, Triton. Although Triton is more massive than Pluto, Pluto’s atmosphere is thicker and, like Triton’s, likely consists of clouds and winds.

The Ninth Celestial | New Horizons

NASA heliophysicist Nikolaos Paschalidis was a happy man when New Horizons mission to Pluto flew past the distant, icy world: he created a mission-enabling technology that would help uncover details about the atmosphere of the never-beforevisited dwarf planet.

The Ninth Celestial | New Horizons

During its flyby, the New Horizons mission used its onboard suite of instruments — three optical, two plasma, a dust sensor, and a radio science receiver/radiometer — to take images and spectroscopic measurements to learn more about Pluto’s atmospheric structure, composition, and temperature, as well as its surface geology and composition.

4

5 The Ninth Celestial | Pluto

Pluto nearly fills the frame in this image from the Long Range Reconnaissance Imager (LORRI) aboard NASA’s New Horizons spacecraft, taken on July 13th, 2015 when the spacecraft was 476,000 miles (768,000 kilometers) from the surface. This is the last and most detailed image sent to Earth before the spacecraft’s closest approach to Pluto on July 14th.

This view is dominated by the large, bright feature informally named the “heart,” which measures approximately 1,000 miles (1,600 kilometers) across. The heart borders darker equatorial terrains, and the mottled terrain to its east (right) are complex. However, even at this resolution, much of the heart’s interior appears remarkably featureless—possibly a sign of ongoing geologic processes.

Three billion miles away, Pluto has sent a “love note” back to Earth, via NASA’s New Horizons spacecraft.

The image shows for the first time that some surfaces on Pluto are peppered with impact craters and are therefore relatively ancient, perhaps several billion years old.

Other regions, such as the interior of the heart, show no obvious craters and thus are probably younger, indicating that Pluto has experienced a long and complex geological history. Some craters appear partially destroyed, perhaps by erosion.

There are also hints that parts of Pluto’s crust have been fractured, as indicated by the series of linear features to the left of the heart.

The Ninth Celestial | Pluto

Pluto was discovered in 1930, but the icy world’s large companion remained hidden for 48 more years due to the close proximity of the pair, which made them appear to blur together in observations.

Charon and Pluto are separated by about 12,000 miles, with Charon measuring about 790 miles in diameter– slightly more than half Pluto’s size. Scientists sometimes refer to the objects as a “double planet” due to their sizes and close proximity.

Christy noticed that Pluto looked elongated in images, as if a blur moved around the planet at a rate of about 6.4 days, the time it takes Charon and Pluto to complete their “pas de deux” rotation about their common center of gravity. Christy studied archives of images of Pluto, which confirmed he had found Pluto’s first moon.

6

7

Pluto’s small, irregularly shaped moon Hydra (right) is revealed in this black and white image taken from New Horizons’ LORRI instrument on July 14th, 2015, from a distance of about 143,000 miles (231,000 kilometers). Features as small as 0.7 miles (1.2 kilometers) are visible on Hydra, which measures 34 miles (55 kilometers) in length.

While Pluto’s largest moon Charon has grabbed most of the lunar spotlight so far, these two smaller and lesserknown satellites are now getting some attention. Nix and Hydra – the second and third moons to be discovered – are approximately the same size, but their similarity ends there.

The Ninth Celestial | Pluto

Pluto’s moon Nix (left), shown here in enhanced color as imaged by the New Horizons Ralph instrument, has a reddish spot that has attracted the interest of mission scientists. The data were obtained on the morning of July 14th, 2015, and received on the ground on July 18th. At the time the observations were taken New Horizons was about 102,000 miles (165,000 km) from Nix. The image shows features as small as approximately 2 miles (3 kilometers) across on Nix, which is estimated to be 26 miles (42 kilometers) long and 22 miles (36 kilometers) wide.

The Ninth Celestial | Pluto

This graphic presents a view of Pluto and Charon as they would appear if placed slightly above Earth’s surface and viewed from a great distance. Recent measurements obtained by New Horizons indicate that Pluto has a diameter of 2370 km, 18.5% that of Earth’s, while Charon has a diameter of 1208 km, 9.5% that of Earth’s.

8

9 The Ninth Celestial | Pluto

Peering closely at the “heart of Pluto,” in the western half of what missionscientists have informally named Tombaugh Regio (Tombaugh Region), New Horizons’ Ralph instrument revealed evidence of carbon monoxide ice. The contours indicate that the concentration of frozen carbon monoxide increases towards the center of the “bull’s eye.” These data were acquired by the spacecraft on July 14th,2015 and transmitted to Earth on July 16th.

NASA’s New Horizons mission has found evidence of exotic ices flowing across Pluto’s surface, at the left edge of its bright heart-shaped area. New close-up images from the spacecraft’s Long-Range Reconnaissance Imager (LORRI) reveal signs of recent geologic activity, something scientists hoped to find but didn’t expect.

The Ninth Celestial | Pluto

“We’ve only seen surfaces like this on active worlds like Earth and Mars,” said mission co-investigator John Spencer of SwRI. “I’m really smiling.”

10

The new close-up images show fascinating detail within the Texas-sized plain (informally named Sputnik Planum) that lies within the western half of Pluto’s heart-shaped region, known as Tombaugh Regio. There, a sheet of ice clearly appears to have flowed—and may still be flowing—in a manner similar to glaciers on Earth.

11 The Ninth Celestial | Pluto

A newly discovered mountain range lies near the southwestern margin of Pluto’s Tombaugh Regio (Tombaugh Region), situated between bright, icy plains and dark, heavily-cratered terrain. This image was acquired by New Horizons’ Long Range Reconnaissance Imager (LORRI) on July 14th, 2015 from a distance of 48,000 miles (77,000 kilometers) and sent back to Earth on July 20th. Features as small as a half-mile (1 kilometer) across are visible.

Pluto’s icy mountains have company.

NASA’s New Horizons mission has discovered a new, apparently less lofty mountain range on the lower-left edge of Pluto’s best known feature, the bright, heart-shaped region named Tombaugh Regio (Tombaugh Region).

These newly-discovered frozen peaks are estimated to be one-half mile to one mile (1-1.5 kilometers) high, about the same height as the United States’ Appalachian Mountains. The Norgay Montes (Norgay Mountains) discovered by New Horizons on July 15 more closely approximate the height of the taller Rocky Mountains.

The new range is just west of the Wregion within Pluto’s heart called Sputnik Planum (Sputnik Plain). The peaks le some 68 miles (110 kilometers) northwest of Norgay Montes.

The Ninth Celestial | Pluto 12

Pluto sends a breathtaking farewell to New Horizons. Backlit by the sun, Pluto’s atmosphere rings its silhouette like a luminous halo in this image taken by NASA’s New Horizons spacecraft around midnight EDT on July 15th, 2015. This global portrait of the atmosphere was captured when the spacecraft was about 1.25 million miles (2 million kilometers) from Pluto and shows structures as small as 12 miles across. The image, delivered to Earth on July 23rd, is displayed with north at the top of the frame.

ew 2015