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)

July 17, 2015

The first close-up images of the dwarf planet Pluto have dazzled planetary scientists, revealing a landscape more alien than they had imagined. Once thought to be a dead ball of rock and ice, Pluto turns out to be a world of giant mountains, mysteriously clean surfaces, and other wonders.

New close-up images of a region near Pluto’s equator reveal a giant surprise: a range of youthful mountains rising as high as 11,000 feet (3,400 meters) above the surface of the icy body.
Credit: NASA-JHUAPL-SwRI

The images were taken by the New Horizons probe, launched by the United States National Aeronautics and Space Administration (NASA). They were taken during the probe’s closest approach to Pluto on July 14, 2015, and they show features as small as ½ mile (0.8 kilometer) across. One image shows mountains rising up to 11,000 feet (3,400 meters) above the surrounding surface, comparable in height to the Rocky Mountains on Earth. These mountains appear to be made of water ice, because frozen methane and frozen nitrogen—two ices previously detected on Pluto’s surface—are too weak to form such steep structures. Observations from Earth had failed to detect any water ice on Pluto.

Scientists were also amazed by a relative lack of impact craters in the images. Such craters tend to build up over time as planets and other bodies are bombarded by chunks of rock and ice. The lack of craters suggests that the surfaces imaged are less than 100 million years old. Since Pluto is thought to be the same age as the rest of the solar system, about 4.5 billion years old, some process must be erasing craters, rejuvenating the planet’s surface. Weather and geological activity—such as earthquakes, volcanoes, and the shifting of tectonic plates—can erase impact craters. But both processes typically require more energy, in the form of heat, than the frigid planet of Pluto seems capable of producing.

It will take about 16 months for the New Horizons spacecraft to send back all the data it has gathered on its nearly 10-year mission. Until then, scientists will anxiously await clues to these and other mysteries.

Other World Book articles: 

Astronomy (2006-a Back in time article) 

Space exploration (2006-a Back in time article)

July 9, 2015

What do a doughnut, a heart, and a whale have in common? They can all be seen on Pluto’s surface (or, regions that resemble these things can, anyway). As it barrels towards Pluto, the U.S. National Aeronautics and Space Administration’s (NASA’s) probe New Horizons continues to generate better images of and more data about the most famous resident of the Kuiper belt (the band of icy bodies beyond the orbit of Neptune).

An image snapped on July 7 by the New Horizons spacecraft while just under 5 million miles (8 million kilometers) from Pluto is combined with color data in this most detailed view yet of the Solar System’s most famous unexplored world. The region shown includes the tip of an elongated dark area along Pluto’s equator already dubbed “the whale.” A bright heart-shaped region on the right is about 1,200 miles (2,000) kilometers across, possibly covered with a frost of frozen methane, nitrogen, and/or carbon monoxide. Credit: NASA/Johns Hopkins Univ./APL/Southwest Research Inst.

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 also hope to encounter one or more other objects in the Kuiper belt. The measurements made by New Horizons will help scientists learn about the nature of these Kuiper belt objects (KBO’s), thought to be remnants of the material that came together to form the planets.

NASA launched New Horizons on Jan. 19, 2006. The probe overcame a computer glitch last weekend and is on track to study the Pluto system as it zooms past on July 14, 2015. Even now, it is now taking far better pictures of Pluto than any Earth-based telescope (even the Hubble Space Telescope). As the dwarf planet comes into focus, a few regions of Pluto have been found to look like things here on Earth. A large, dark region in the southern hemisphere resembles a whale. A donut lookalike, a circular light region with a dark spot in the center, is nestled in the crook of the whale’s tail. To the right of the whale’s head is a giant bright region that resembles a heart symbol.

Scientists are not yet certain how these regions formed. They suspect that the doughnut is a large volcano or crater, and that the whale and heart were formed from different chemicals falling from Pluto’s thin atmosphere. After New Horizons passes Pluto, it will take 16 months for the probe to relay all the information it gathered back to Earth. Only then will we know the true story of the doughnut, the heart, and the whale!

Other links: 

• New Horizon (NASA site)
• Space exploration (World Book article)
• Space exploration (2006-a Back in time article)

March 28, 2014

A probable dwarf planet that orbits much farther from the sun than any other known object has been discovered by American astronomers Chad Trujillo and Scott Sheppard. The little planet is so far away that its orbit takes it 15 times as far from the sun as the orbit of Neptune, the most distant major planet in the solar system. The astronomers first sighted the object, designated 2012 VP113, or VP for short, using the Dark Energy Camera mounted on the 4-meter Blanco telescope in Chile. However, to confirm the shape of the object’s orbit around the sun, the astronomers needed to watch the object for many months. The would-be dwarf planet VP is the second such object found orbiting the sun at such a vast distance. The first, named Sedna, was discovered in 2003 by a team that included Trujillo. VP appears to be about 280 miles (450 kilometers) across, about half the size of Sedna and the most commonly known dwarf planet, Pluto. Trujillo and Sheppard nicknamed the new dwarf planet Biden, for United States Vice President Joe Biden.

The distance from Earth to the sun is, on average, about 93 million miles (150 million kilometers). This distance is called an astronomical unit or AU. Neptune is about 30 AU from the sun. The orbit of Sedna is a stretched out oval that carries it as far as 1,000 AU from the sun. However, Sedna also comes to within 76 AU of the sun at its closest approach. The orbit of VP is more circular. For this reason, VP doesn’t stray as far as Sedna, only about 450 AU. On the other hand, VP never gets closer than 80 AU to the sun at its closest approach, farther than any other solar system body known.

Dwarf planets Ceres, Eris, Haumea, Makemake, and Pluto and their moons, compared with Earth and its moon. All of these dwarf planets are smaller than the moon. (©UCAR/University of Michigan)

The area to which Pluto and several other dwarf planets belong is called the Kuiper belt. It is the region beyond Neptune and includes millions of icy bodies. Far beyond the Kuiper belt is a region called the Oort cloud, an area thought to be filled with millions of comets. Both Sedna and VP orbit between the Kuiper belt and the Oort cloud. Many astronomers believed this area was empty. The discovery of Sedna and now VP puts that idea into question.

The discovery offers new information about how the solar system was formed. How did such large objects assume orbits so far from the sun? How many are there yet to be found? One interesting conclusion suggested by astronomers studying the new data is that the orbits of Sedna and VP may be influenced by a large, yet undiscovered planet.

Additional World Book articles:

• Ceres
• Eris
• Planet (the dwarf planets)
• Exploring the Suburban Solar System (a Special Report)
• Astronomy (2004) (a Back in Time article)
• Astronomy (2006) (a Back in Time article)

February 27, 2013

The name “Vulcan” was a surprise co-winner in the “Pluto Rocks” online contest in which the public was asked to help choose names for two moons recently discovered orbiting Pluto. “Vulcan,” which was not on the original ballot, was a write-in candidate suggested by actor William Shatner, who starred in the “Star Trek” science-fiction television and film series. “Vulcan” collected 174,062 of the 450,324 votes cast. “Cerberus,” the name of the three-headed dog that guarded the entrance to the underworld in Greek and Roman mythology, came in second, with nearly 100,000 votes. The contest was organized by astronomers with the SETI Institute, who found the moons in 2011 and 2012 using the Hubble Space Telescope. SETI is a research organization that searches for life in the universe beyond Earth.

Canadian-born actor William Shatner gained fame as Captain James T. Kirk, commander of the starship U.S.S. Enterprise in the television science-fiction series "Star Trek" (1966-1969). (© Paramount/The Kobal Collection)

The ballot for the “Pluto Rocks” contest originally included 12 names from Greek and Roman mythology associated with the underworld, also known as Hades. Pluto was the god of the dead in Roman mythology. He was almost identical to Hades, the Greek god of the dead. The SETI scientists agreed to add “Vulcan” to the ballot after Shatner promoted the name on Twitter. In Roman mythology, Vulcan was the god of fire, metalworking, and skilled craftwork in general. Although he did not dwell in Hades, he was a nephew of Pluto and was believed to have his blacksmith’s forge beneath Mount Etna in Sicily. Coincidentally, Vulcan was the name of the fictional home planet of Spock, the half-human first officer to Shatner’s Captain James T. Kirk.

Leonard Nimoy played the alien Mr. Spock in the "Star Trek" science-fiction television series and motion pictures. (NBC-TV/The Kobal Collection)

The SETI astronomers will now recommend the winning names to the International Astronomical Union (IAU), which determines the names of celestial bodies. The IAU, which is not required to accept the winning names, was expected to announce the new moons’ official names sometime this spring.

Additional World Book articles:

• New Horizons
• Space exploration
• Exploring the Suburban Solar System (a special report)
• Astronomy 1930 (Back in Time article)
• Astronomy 1978 (Back in Time article)
• Astronomy 2006 (Back in Time article)
• Space exploration 2006 (Back in Time article)

February 13, 2013

Astronomers with the SETI Institute, a research organization that searches for life in the universe beyond Earth, are giving the public a chance to help pick the names for the two newest moons discovered in orbit around Pluto. Now known as P4 and P5, the moons were found by astronomers at the institute in 2011 and 2012, respectively, using the Hubble Space Telescope (HST).

The ballot for the “Pluto Rocks” project includes 12 names from Greek and Roman mythology associated with the land of the dead, also known as Hades. Pluto was the god of the dead in Roman mythology. He was almost identical to Hades, the Greek god of the dead. The candidate names for the new moons include Cerberus, the three-headed dog that guarded the entrance to the underworld;  Hercules, who descended into Hades to capture Cerberus and bring him back to the upper world; Persephone, a goddess who was kidnapped by Pluto (Hades); and Styx, the gloomy river in the underworld. Pluto’s other three moons are Charon, named for the ragged old boatman who ferried the shades (spirits) of the dead across the Styx or other rivers of the underworld; Hydra, a many-headed serpent that had its den at the entrance to Hades; and Nix, the goddess of the night.

Hades, the Greek god of the underworld--with Cerberus--was known as Pluto in Roman mythology. (World Book illustration by Pat and Robin Dewitt)

The ballot can be found on the Internet at http://plutorocks.seti.org. Voting ends at noon Eastern Standard Time on February 25, 2013. After the voting, the astronomers will pick two names to submit to the International Astronomical Union (IAU), which determines the names of celestial bodies. The IAU was expected to announce the new moons’ official names sometime this spring.

Pluto was discovered by Clyde W. Tombaugh in 1930, based on predictions by astronomer Percival Lowell in 1905. The name for Tombaugh’s planet was suggested by Venetia Phair, an 11-year-old British girl, to her grandfather, a librarian, who passed on the suggestion to an astronomer friend. The friend cabled the name to the Lowell Observatory in Flagstaff, Arizona, where Tombaugh worked. Long considered the ninth planet in the solar system, Pluto was “demoted” from planet to a new category of space object called dwarf planet after astronomers in the 1990′s found many objects similar to Pluto in the outer reaches of the solar system, in an area called the Kuiper belt.

Additional World Book articles:

• New Horizons
• Space exploration
• Exploring the Suburban Solar System (a special report)
• Astronomy 1930 (Back in Time article)
• Astronomy 1978 (Back in Time article)
• Astronomy 2006 (Back in Time article)
• Space exploration 2006 (Back in Time article)

July 12, 2012

Astronomers using the Hubble Space Telescope (HST) have discovered another moon orbiting Pluto, announces NASA. The new satellite is the fifth found circling the small body, which for decades was widely considered the ninth planet in the solar system. Pluto was “demoted” from planet to a new category of space object called “dwarf planet” after astronomers in the 1990′s found many objects similar to Pluto in the outer reaches of the solar system, in an area called the Kuiper Belt. Pluto was discovered by Clyde W. Tombaugh in 1930, based on predictions by astronomer Percival Lowell in 1905. Pluto is 1,460 miles (2,350 kilometers) in diameter.

Pluto is so far from Earth and is so small that even powerful telescopes reveal little detail of its surface. The Hubble Space Telescope gathered the light for the pictures of Pluto shown here. (NASA)

Astronomers with the SETI Institute, a research organization that searches for life in the universe beyond Earth, discovered the new moon and gave it the temporary name P5. The astronomers are using the HST to study Pluto in preparation for a fly-by of the dwarf planet by the New Horizons space probe in July 2015. New Horizons was launched in 2006 to explore Pluto, its largest moon Charon, and other objects in the Kuiper Belt.

According to the researchers, P5 is a tiny, irregularly shaped body that measures from 6 to 15 miles (10 to 25 kilometers) across. The astronomers were unable to get a closer measurement because Pluto and its moons are about 2.8 billion miles (4.7 billion kilometers) away from Earth. Pluto’s moon Charon, which is about 750 miles (1,207 kilometers) in diameter, was discovered in 1978. Hydra and Nix, each up to 100 miles (160 kilometers) in diameter, were found in 2005. Pluto’s fourth moon, P4, discovered in 2011, is about 8 to 21 miles (13 to 34 kilometers) in diameter.

The scientists were a bit disconcerted by the discovery of an unknown moon as New Horizons is nearing Pluto. “All of this stuff poses a navigation hazard for New Horizons,” according to Ray Villard, news director of the Space Telescope Science Institute. However, tiny P5 has also produced a sense of wonder at the complexity of ex-planet Pluto’s system of satellites.

Additional World Book articles:

• Space exploration
• Exploring the Suburban Solar System (a special report)
• Astronomy 1930 (Back in Time article)
• Astronomy 1978 (Back in Time article)
• Astronomy 2006 (Back in Time article)
• Space exploration 2006 (Back in Time article)

Nov. 2, 2011

The dwarf planet Eris, whose discovery in 2005 contributed to Pluto’s demotion from planet to dwarf planet, is actually a bit smaller than Pluto, new observations suggest. Discovered in 1930, Pluto was widely considered a full-fledged planet­, until scientists found Eris. At first, it seemed that Eris, which appeared to be slightly larger than Pluto, might become the 10^th planet. Instead, the possibility that astronomers might find many more objects about the size of Pluto and Eris led to a scientific debate about the definition of a planet. In 2006, the International Astronomical Union, the body in charge of naming objects in space, created a formal definition for a planet as well as a new category of objects called dwarf planet for Eris and Pluto.

Eris, Pluto, and two other dwarf planets, called Makemake and Haumea, are found in the Kuiper belt, the area of the solar system immediately beyond the orbit of Neptune. A fifth dwarf planet called Ceres is the largest member of the Main Belt, a region of asteroids between the orbits of Mars and Jupiter. The new observations indicate that Eris is less than 1,454 miles (2,340 kilometers) in diameter. Pluto is about 1,455 miles (2,342 kilometers) wide. All the dwarf planets are smaller than Earth’s moon. Some scientists think there may be thousands of dwarf planets in the solar system.

This illustration shows the dwarf planets Ceres, Eris, Haumea, Makemake, and Pluto and their moons in comparative size to Earth and the moon. UCAR/University of Michigan.

Despite their similar size, Eris and Pluto are remarkably different. Eris is much denser and shinier than Pluto. In fact, Eris is one of the brightest objects in the solar system. Scientists think Eris may be so shiny because of methane ice on its surface.

Additional World Book articles:

• Back in Time (Astronomy,  1930)
• Back in Time (Astronomy, 2005)
• Exploring the Suburban Solar System (special report)
• Tombaugh, Clyde William