January 16, 2019

On January 1, the United States National Aeronautics and Space Administration (NASA) probe New Horizons flew by a 21-mile- (34-kilometer-) long rock at the outer reaches of our solar system. The probe took the rock’s first “close-up” photos, revealing details of the snowman-shaped space object, called 2014 MU69 or “Ultima Thule.” The term Thule was used by ancient European cartographers to describe the farthest northern lands of Earth. Ultima Thule (farthermost Thule) once described areas beyond the known world. Ultima Thule, then, is a fitting name for the distant object: it is 4 billion miles (6.5 billion kilometers) from Earth.

The New Horizons spacecraft took this photo of Ultima Thule on Jan. 1, 2019, from a distance of some 18,000 miles (28,000 kilometers). Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

New Horizons is the first spacecraft to study Pluto and the Kuiper belt, a band of icy bodies largely beyond the orbit of the planet Neptune. New Horizons flew past Pluto in July 2015, revealing a surprisingly varied and geologically active world. Despite its distance from the sun, Pluto has been molded and shaped by many of the same forces that created the eight planets of our solar system.

With the flyby of Ultima Thule, New Horizons became the first spacecraft to visit an object discovered after the spacecraft was launched. The craft blasted off from Cape Canaveral Air Force Station in Florida in 2006. Astronomers discovered Ultima Thule in 2014.

This NASA illustration shows New Horizons encountering 2014 MU69–“Ultima Thule.” Credit: NASA/JHUAPL/SwRI

What’s so special about Ultima Thule? It may look like just another space rock, but it is far different from the asteroids and comets found closer to the sun. The solar system’s planets and other inner objects have been transformed by the sun’s extreme heat, by catastrophic collisions, and by immense gravitational pressures. Ultima Thule and other Kuiper belt objects (KBO’s) are like frozen time capsules that show how things looked as the solar system was forming. The first grainy photographs of Ultima Thule show an object made up of two lobes that likely came together in a walking-speed “collision”—a rather serene birth in an otherwise violent universe.

New Horizons has completed its study of Ultima Thule, but NASA expects to learn more about the distant object over the next 20 months or so as information continues to trickle in. It takes a while for data to be transmitted across the immense distance to Earth. And this may not be the last distant flyby for New Horizons. NASA is searching for other space objects to visit before New Horizons runs out of power in the mid-2030’s.

September 21, 2015

Hazy Pluto: Just 15 minutes after its closest approach to Pluto on July 14, 2015, NASA’s New Horizons spacecraft looked back toward the sun and captured this near-sunset view of the rugged, icy mountains and flat ice plains extending to Pluto’s horizon. The image was taken from a distance of 11,000 miles (18,000 kilometers) to Pluto; the scene is 780 miles (1,250 kilometers) wide. Credit: NASA/JHUAPL/SwRI

Despite Pluto’s immense distance from the sun and its frigid temperatures, it is proving to be an incredibly active and varied world. Since the United States National Aeronautics and Space Administration’s (NASA’s) New Horizons probe sped past the dwarf planet on July 14 of this year, it has been slowly sending data back to Earth. This process will continue until the end of next year, and the probe continues to change scientists’ view of Pluto.

New Horizons is the first space probe sent to study the dwarf planet Pluto. The main goal of the mission is to explore Pluto and its large moon, Charon. Mission managers are also planning other encounters for New Horizons in the Kuiper belt, the band of icy bodies beyond the orbit of Neptune. The measurements made by New Horizons will help scientists learn about the nature of these Kuiper belt objects (KBO’s), thought to be the remains of the material that came together to form the planets.

On Thursday, NASA released pictures New Horizons took of Pluto as it was speeding away from the dwarf planet. The probe captured stunning images of Pluto’s hazy atmosphere, craggy mountains, and smooth plains backlit by the faint light of the setting sun. Aside from being incredibly beautiful, these images are helping scientists to better understand the forces responsible for shaping Pluto.

Scientists now think that Pluto’s polar areas have a nitrogen cycle similar to Earth’s water cycle. Gaseous nitrogen in Pluto’s atmosphere probably condenses and falls back to the surface as snow. This may be driven by uneven heating and cooling from the distant sun, just like Earth’s weather. Glaciers of nitrogen ice cover many parts of the planet, much like the glaciers made of water ice in Greenland and Antarctica. Scientists eagerly await the next exciting batch of images that New Horizons will deliver.

Other World Book Behind the headline articles

• Pluto Dazzles in First Close-Up (July 17, 2015)
• Cold, “Dead” World Alive and Kicking (July 28, 2015)

July 28, 2015

New Horizons discovered flowing ices in Pluto’s heart-shaped feature. Swirl-shaped patterns of light and dark suggest that a surface layer of ices has flowed around obstacles and into depressions, similar to how glaciers behave on Earth.
Credit: NASA/JHUAPL/SwRI

Since its discovery in 1930, many astronomers have thought the dwarf planet Pluto to be a cold, dead world. As data pour in from the United States National Aeronautics and Space Administration (NASA) probe New Horizons, however, Pluto is proving itself to be far from dead—although it is still cold!

New Horizons was the first probe sent to Pluto. It explored the dwarf planet and its large moon, Charon. Mission managers also hope to study other objects in the Kuiper belt, the band of icy bodies beyond the orbit of Neptune. The measurements made by New Horizons will help scientists learn about the nature of these Kuiper belt objects (KBO’s), thought to be the remains of the material that came together to form the planets.

New Horizons flew past Pluto on July 14, 2015. During its time near the dwarf planet, the probe captured dozens of photographs along with other scientific data. Because New Horizons is so far away, however, it will take 16 months for the probe to return all of its information to Earth. But New Horizons has already sent home amazing photographs and is challenging earlier ideas about Pluto.

At Pluto’s estimated surface temperature of –385 °F (–232 °C), any water would be frozen solid, and the ice would be extremely rigid and brittle. But at those temperatures, ices made up of other molecules can still flow over many years. New Horizons has revealed glaciers made of carbon monoxide, methane, and nitrogen in the large, heart-shaped region on Pluto’s surface. These glaciers appear to have flowed down from higher points to lower ones, just as water-ice glaciers do here on Earth.

An image taken on July 13, 2015, from New Horizons, when the probe was 476,000 miles (768,000 kilometers) from the surface. The heart-shaped region on Pluto holds glaciers made of carbon monoxide, methane, and nitrogen.
Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

Furthermore, astronomers have estimated that this glacial activity has occurred relatively recently. Before New Horizons, most scientists had assumed that Pluto had changed very little in the past 4 billion years. But the glaciers formed within the last 30 million years and may still be flowing today. In geological terms, that is not very long at all—more than 35 million years after the dinosaurs went extinct on Earth, for example. Even some 3.5 billion miles (6 billion kilometers) away from the sun, Pluto has shown itself to be an active—if icy—world!

Other World Book Behind the headlines:

• Are We There Yet? (April 15, 2015)
• A Heart and A Whale With a Doughnut In Its Tail? (July 9, 2015)
• Pluto Dazzles In First Close-Up (July 17, 2015)