Clyde Tombaugh: Astronomer Who Discovered Pluto Clyde Tombaugh: Astronomer Who Discovered Pluto By Nola Taylor Redd, Space.com Contributor | February 15, 2013 03:05pm ET MORE When Clyde Tombaugh built his first telescope at the age of 20, he could not have known it was setting him forward on a path that would eventually lead to the discovery of the first known dwarf planet, Pluto. Let's take a look at the life of this amazing man. Clyde Tombaugh, discoverer of Pluto, peers into an instrument. Credit: Lowell Observatory Early life and family Clyde William Tombaugh was born on near Streator, Ill., on Feb. 4, 1906. His family purchased a farm near Burdett, Kan., while he was still young, where a hailstorm ruined his family's crops and put an end to his hopes to attend college at the time. In 1928, the amateur astronomer was offered a job at Lowell Observatory in Arizona, where he discovered Pluto. In 1934, he married Patricia Edson. They had two children, Annette and Alden.

He earned his bachelor's and master's degree in astronomy from the University of Kansas, working at the observatory during the summers. Clyde W. Tombaugh, discoverer of Pluto Credit: Academy of Achievement Tombaugh remained at Lowell Observatory until the advent of World War II, when he was called into service teaching navigation to the U.S. Navy at Arizona State College. After the war concluded, he worked at the ballistics research laboratory at White Sands Missile Range in New Mexico. From 1955 until he retired in 1973, he taught at New Mexico State University. Tombaugh passed away at his home in Las Cruces, N.M., on Jan. 17, 1997. An avid amateur astronomer Unimpressed with store-bought telescopes, Tombaugh constructed his first telescope at the age of 20, grinding the mirrors himself. Over the course of his life, he would build more than 30 telescopes. In 1928, he put together a 23-centimeter reflector out of the crankshaft of a 1910 Buick and parts from a cream separator.

Using this telescope, young Clyde made detailed observations of Jupiter and Mars, which he sent to Lowell Observatory in hopes of garnering feedback from professional astronomers. Over the course of his life, Tombaugh built more than 30 telescopes himself, including this one on his family's Kansas farm. Credit: NASA Instead of receiving constructive criticism, Tombaugh was instead offered a position at the observatory. The staff had been searching for an amateur astronomer to operate their new photographic telescope in search of, among other things, the mysterious Planet X. Not long after its discovery in 1781 , the new planet Uranus was found to have strange movements that could only be attributed to another body. Neptune's discovery in 1846 somewhat accounted for the orbit, but there were still discrepancies that led scientists to conclude yet another planet existed. In 1894, businessman Percival Lowell built Lowell Observatory to study Mars . In 1905, he turned the telescope toward the search for the elusive Planet X, though he died before the new planet could be found. When Tombaugh was hired in 1929, he joined the search for the missing planet.

The telescope at the observatory was equipped with a camera that would take two photographs of the sky on different days. A device known as a blink compactor rapidly flipped back and forth between the two photographs. Stars and galaxies essentially remained unmoving in the images, but anything closer could be visually identified by its motion across the sky. Tombaugh spent approximately a week studying each pair of photographs, which contained over 150,000 stars, and sometimes nearly a million. On Feb. 18, 1930, Tombaugh noticed movement across the field of a pair of images taken a month beforehand. After studying the object to confirm it, the staff of Lowell Observatory officially announced the discovery of a ninth planet on March 13. Original plates from Clyde Tombaugh's discovery of Pluto in Lowell Observatory Archive. Credit: Lowell Observatory With the discovery came the rights to name the new body, so the staff opened up a worldwide call for suggestions. Eleven-year old Venetia Burney of England suggested the name Pluto , because the dark, distant planet resembled the abode of the Greek god of the underworld. Pluto endured as a planet for more than 70 years.

As astronomical instruments became increasingly precise, however, other similar-sized objects were found beyond the orbit of Neptune. In 2006, almost a decade after Tombaugh's death, the International Astronomical Union reclassified Pluto as a dwarf planet . The New Horizons mission carries some of Tombaugh's ashes on board as it travels to Pluto and beyond. Although most famous for the discovery of the most controversial body in the solar system, Tombaugh also found a comet, hundreds of asteroids, and several galactic star clusters over the course of his career. — Nola Taylor Redd, SPACE.com Contributor Related: Pluto discovered - Feb 18, 1930 - HISTORY.com Pluto discovered Publisher A+E Networks Pluto, once believed to be the ninth planet, is discovered at the Lowell Observatory in Flagstaff, Arizona, by astronomer Clyde W. Tombaugh. The existence of an unknown ninth planet was first proposed by Percival Lowell, who theorized that wobbles in the orbits of Uranus and Neptune were caused by the gravitational pull of an unknown planetary body. Lowell calculated the approximate location of the hypothesized ninth planet and searched for more than a decade without success.

However, in 1929, using the calculations of Powell and W.H. Pickering as a guide, the search for Pluto was resumed at the Lowell Observatory in Arizona. On February 18, 1930, Tombaugh discovered the tiny, distant planet by use of a new astronomic technique of photographic plates combined with a blink microscope. His finding was confirmed by several other astronomers, and on March 13, 1930–the anniversary of Lowell’s birth and of William Hershel’s discovery of Uranus–the discovery of Pluto was publicly announced. With a surface temperature estimated at approximately -360 Fahrenheit, Pluto was appropriately given the Roman name for the god of the underworld in Greek mythology. Pluto’s average distance from the sun is nearly four billion miles, and it takes approximately 248 years to complete one orbit. It also has the most elliptical and tilted orbit of any planet, and at its closest point to the sun it passes inside the orbit of Neptune, the eighth planet. After its discovery, some astronomers questioned whether Pluto had sufficient mass to affect the orbits of Uranus and Neptune.

In 1978, James Christy and Robert Harrington discovered Pluto’s only known moon, Charon, which was determined to have a diameter of 737 miles to Pluto’s 1,428 miles. Together, it was thought that Pluto and Charon formed a double-planet system, which was of ample enough mass to cause wobbles in Uranus’ and Neptune’s orbits. In August 2006, however, the International Astronomical Union announced that Pluto would no longer be considered a planet, due to new rules that said planets must “clear the neighborhood around its orbit.” Since Pluto’s oblong orbit overlaps that of Neptune, it was disqualified. Related Videos When Was the Dwarf Planet Pluto Discovered? By Jennifer Rosenberg Updated March 03, 2016. On February 18, 1930, Clyde W. Tombaugh, an assistant at the Lowell Observatory in Flagstaff, Arizona, discovered Pluto. For over seven decades, Pluto was considered the ninth planet of our solar system. The Discovery It was American astronomer Percival Lowell who first thought there might be another planet somewhere near Neptune and Uranus.

Lowell had noticed that the gravitational pull of something large was affecting the orbits of those two planets. However, despite looking for what he called "Planet X" from 1905 until his death in 1916, Lowell never found it. Thirteen years later, the Lowell Observatory (founded in 1894 by Percival Lowell) decided to recommence Lowell's search for Planet X. They had a more powerful, 13-inch telescope built for this sole purpose. The Observatory then hired 23-year-old Clyde W. Tombaugh to use Lowell's predictions and the new telescope to search the skies for a new planet. It took a year of detailed, painstaking work, but Tombaugh did find Planet X. continue reading below our video 4 Tips for Improving Test Performance The discovery occurred on February 18, 1930 while Tombaugh was carefully examining a set of photographic plates created by the telescope. Despite Planet X being discovered on February 18, 1930, the Lowell Observatory was not quite ready to announce this huge discovery until more research could be done. After a few weeks, it was confirmed that Tombaugh's discovery was indeed a new planet.

On what would have been Percival Lowell's 75th birthday, March 13, 1930, the Observatory publicly announced to the world that a new planet had been discovered. Pluto the Planet Once discovered, Planet X needed a name. Everyone had an opinion. However, the name Pluto was chosen on March 24, 1930 after 11-year-old Venetia Burney in Oxford, England suggested the name "Pluto." The name denotes both the assumed unfavorable surface conditions (as Pluto was the Roman god of the underworld) and also honors Percival Lowell, as Lowell's initials make up the first two letters of the planet's name. At the time of its discovery, Pluto was considered to be the ninth planet in the solar system. Pluto was also the smallest planet, being less than half the size of Mercury and two-thirds the size of Earth's moon. Usually, Pluto is the planet farthest from the sun. This great distance from the sun makes Pluto very inhospitable; it's surface is expected to be made up of mostly ice and rock and it takes Pluto 248 years just to make one orbit around the sun.

Pluto Loses Its Planet Status As the decades passed and astronomers learned more about Pluto, many questioned whether Pluto could really be considered a full-fledged planet. Pluto's status was questioned in part because it was by far the smallest of the planets. Plus, Pluto's moon (Charon, named after Charon of the underworld , discovered in 1978) is incredibly large in comparison. Pluto's eccentric orbit also concerned astronomers; Pluto was the only planet whose orbit actually crossed that of another planet (sometimes Pluto crosses Neptune's orbit). When bigger and better telescopes began to discover other large bodies beyond Neptune in the 1990s, and especially when another large body was discovered in 2003 that rivaled the size of Pluto, Pluto's planet status became seriously questioned . In 2006, the International Astronomical Union (IAU) officially created a definition of what makes a planet; Pluto did not meet all the criteria. Pluto was then downgraded from a "planet" to a "dwarf planet." Why is Pluto no longer a planet? (Everyday Mysteries: Fun Science Facts from the Library of Congress) Why is Pluto no longer a planet?

The International Astronomical Union (IAU) downgraded the status of Pluto to that of a dwarf planet because it did not meet the three criteria the IAU uses to define a full-sized planet. Essentially Pluto meets all the criteria except one- it “has not cleared its neighboring region of other objects.” In August 2006 the International Astronomical Union (IAU) downgraded the status of Pluto to that of "dwarf planet." This means that from now on only the rocky worlds of the inner Solar System and the gas giants of the outer system will be designated as planets. The “inner Solar System” is the region of space that is smaller than the radius of Jupiter’s orbit around the sun. It contains the asteroid belt as well as the terrestrial planets, Mercury, Venus, Earth, and Mars. The “gas giants” of course are Jupiter, Saturn, Neptune, and Uranus. So now we have eight planets instead of the nine we used to have. What is a Dwarf Planet?

A “dwarf planet,” as defined by the IAU, is a celestial body in direct orbit of the Sun that is massive enough that its shape is controlled by gravitational forces rather than mechanical forces (and is thus ellipsoid in shape), but has not cleared its neighboring region of other objects. So, the three criteria of the IAU for a full-sized planet are: It is in orbit around the Sun. It has sufficient mass to assume hydrostatic equilibrium (a nearly round shape). It has "cleared the neighborhood" around its orbit. Pluto meets only two of these criteria, losing out on the third. In all the billions of years it has lived there, it has not managed to clear its neighborhood. You may wonder what that means, “not clearing its neighboring region of other objects?” Sounds like a minesweeper in space! This means that the planet has become gravitationally dominant -- there are no other bodies of comparable size other than its own satellites or those otherwise under its gravitational influence, in its vicinity in space. So any large body that does not meet these criteria is now classed as a “dwarf planet,” and that includes Pluto, which shares its orbital neighborhood with Kuiper belt objects such as the plutinos.

History of Pluto The object formerly known as the planet Pluto was discovered on February 18, 1930 at the Lowell Observatory in Flagstaff, Arizona, by astronomer Clyde W. Tombaugh, with contributions from William H. Pickering. This period in astronomy was one of intense planet hunting, and Pickering was a prolific planet predictor. In 1906, Percival Lowell, a wealthy Bostonian who had founded the Lowell Observatory in Flagstaff, Arizona in 1894, started an extensive project in search of a possible ninth planet, which he termed "Planet X." By 1909, Lowell and Pickering had suggested several possible celestial coordinates for such a planet. Lowell and his observatory conducted the search until his death in 1916, to no avail. Unknown to Lowell, on March 19, 1915, his observatory had captured two faint images of Pluto, but they were not recognized for what they were. Lowell was not the first to unknowingly photograph Pluto. There are sixteen known pre-discoveries, with the oldest being made by the Yerkes Observatory on August 20, 1909.

The search for Planet X did not resume until 1929, when the job was handed to Clyde Tombaugh, a 23-year-old Kansan who had just arrived at the Lowell Observatory. Tombaugh's task was to systematically image the night sky in pairs of photographs taken two weeks apart, then examine each pair and determine whether any objects had shifted position. Using a machine called a blink comparator, he rapidly shifted back and forth between views of each of the plates to create the illusion of movement of any objects that had changed position or appearance between photographs. On February 18, 1930, after nearly a year of searching, Tombaugh discovered a possible moving object on photographic plates taken on January 23 and January 29 of that year. After the observatory obtained further confirmatory photographs, news of the discovery was telegraphed to the Harvard College Observatory on March 13, 1930. The discovery made headlines across the globe.

The Lowell Observatory, which had the right to name the new object, received over 1,000 suggestions from all over the world; the name Pluto was proposed by Venetia Burney, an eleven-year-old schoolgirl in Oxford, England. Venetia was interested in classical mythology as well as astronomy, and considered the name for the god of the underworld appropriate for such a presumably dark and cold world. She suggested it in a conversation with her grandfather Falconer Madan, a former librarian at the University of Oxford's Bodleian Library. Madan passed the name to Professor Herbert Hall Turner, who then cabled it to colleagues in the United States. Pluto officially became Pluto on March 24, 1930. The name was announced on May 1, 1930, and Venetia received five pounds (£5) as a reward. Related Web Sites International Astronomical Union (IAU): Pluto and the Developing Landscape of our Solar System - A discussion about Pluto from IAU that includes a history, references to how a planet is defined and a link to the report on the final resolution. Also included are questions and answers about Planets, Dwarf Planets, and Small Solar System Bodies.

The Girl Who Named a Planet - This is an article about Venetia (Burney) Phair, the girl who named the planet Pluto. NOVA: The Pluto Files - Watch the PBS program which features Neil deGrasse Tyson exploring the rise and fall of America’s favorite planet. Solar System Exploration: Pluto - NASA provides an abundance of information about Pluto such as facts, images, headline news, and a video. Further Reading Boyle, Alan. The case for Pluto: how a little planet made a big difference. Hoboken, N.J, John Wiley & Sons, c2010. 258 p. Doressoundiram, Alain, and Emmanuel Lellouch. At the edge of the solar system: icy new worlds unveiled. [Translator, Bob Mizon]. Berlin, New York, Springer Verlag; Chichester, U.K,: Published in association with Praxis, c2010. 205 p. Original French edition: Aux confin de système solaire Hoyt, William Graves. W. H. Pickering's planetary predictions and the discovery of Pluto. Isis, v. 67, Dec.1976: 551-564.

Pickering, W.H. Trans-Neptunian Planet. Popular astronomy, v. 38, June-July1930: 341-344. Putnam, Roger Lowell, and V.M. Slipher. Searching out Pluto, Lowell’s trans-Neptunian planet X. Scientific monthly, v. 34, Jan. 1932: 5-21. Tyson, Neil deGrasse. The Pluto files: the rise and fall of America’s favorite planet. New York, W.W. Norton, c2009. 194 p. For more print resources... Search on "Kuiper Belt" "Pluto (dwarf planet)," "Planets," or "Solar System" in the Library of Congress Online Catalog . Clyde Tombaugh - Kansapedia - Kansas Historical Society Jump to Navigation Clyde Tombaugh Discoverer of the planet Pluto. Born: February 4, 1906, Streator, Illinois. Died: January 17, 1997, Las Cruces, New Mexico.

Fifty miles west of Great Bend, down K-156 highway, is the small farm community of Burdett. In the shadow of the water tower is a roadside park with a large metal historical marker devoted to Clyde W. Tombaugh, the discoverer of Pluto. Clyde W. Tombaugh was born in 1906 in Streator, Illinois. In 1922 his family moved to a farm near Burdett. As a youngster, his interest in astronomy was encouraged by his father and uncle. Tombaugh was a self-taught amateur astronomer who made his own telescopes from hand ground mirrors and parts of farm equipment. He graduated from Burdett High School in 1925. In 1928 Tombaugh made a nine-inch telescope that enabled him to make very accurate and detailed sketches of Jupiter and Mars. Seeking advice from professional astronomers, he sent his sketches to the Lowell Observatory in Flagstaff, Arizona. As coincidence would have it, the Lowell staff was looking for an amateur astronomer capable of operating their new photographic telescope. They were sufficiently impressed with his work to offer Tombaugh the position on a trial basis.

Like many farm folk of that time, Tombaugh had never traveled very far from his home. In early January 1929 he boarded a train for Flagstaff. Tombaugh wrote: After spending 28 hours in a chair car on the Santa Fe, I arrived at Flagstaff in the early afternoon of 15 January, 1929. Dr. Slipher met me at the depot and drove me up Mars Hill. The yellow pine forest was in stark contrast to the treeless plains of Western Kansas. I was rather unnerved by it all, everybody were strangers, 1,000 miles from home, and not enough money in my wallet for a return ticket home . . . Little did he know that the three-month trial period would turn into 13 years at the Lowell Observatory. Prior to 1781 everyone knew that the solar system was composed of six planets. In March of that year William Herschel became the first person in recorded history to discover a planet. The discovery of Uranus was a glorious achievement for astronomy, however, there was a small problem. Uranus did not seem to want to conform to the laws of Newtonian physics.

The planet's behavior defied predictability, and no one seemed to be able to explain this erratic behavior. In 1824 Friedrich Bessel of Germany suggested that another planet beyond Uranus would explain the problem. By 1830 it had become generally accepted that another, yet undiscovered, planet existed. Finally, on September 23, 1846, the planet Neptune was discovered by Johann Galle at the Berlin Observatory. Neptune helped to explain the difficulties in predicting the orbit of Uranus and vindicated Newton's laws — in part. There still existed a couple of minor problems, but this time almost everyone agreed that there must be another planet beyond Neptune, which would explain the difficulties. Unfortunately, it was too distant, too dim, and probably impossible to find. Enter Percival Lowell. Lowell was born into a wealthy Boston family and attended Harvard. He became a very successful businessman and traveled extensively. He eventually turned to a serious pursuit of astronomy and in 1894 he built the Lowell Observatory at Flagstaff, so he could study the planet Mars.

In 1905 Lowell began his search for the ninth planet, which he labeled "Planet X." By 1908 another American, William Pickering, was also engaged in the quest to find the mysterious planet. Pickering had helped Lowell establish his observatory but had distanced himself after Lowell became convinced that intelligent life existed on Mars. Sadly, Percival Lowell suffered a massive stroke and died on November 12, 1916, without sighting the planet he had devoted many years to locating. Lowell left an endowment of more than a million dollars to keep his observatory operating. In his will he named his assistant, Vesto Slipher, director of the observatory. Lowell's widow contested the will, and the court battle to settle the estate—which would consume most of the endowment—lasted until 1927. Slipher prepared to resume the quest for Planet X by having a new and more powerful telescope installed. It would be a tedious task involving spending long hours in the unheated dome taking exposures of the sky and then trying to detect a minute shift in one of the thousands and thousands of points of light that would identify a planet.

This is the task the observatory hired Tombaugh to perform. To detect the movement of an object in the sky involved taking two photographs of the same section of the sky several days apart using the observatory's 13-inch astrograph. The plates were then placed in a device called a blink comparator that "blinked" back and forth between the two plates at a speed to make the two appear as one. Any object that has moved between the frames would be the elusive planet. Each photographic plate could contain more than 150,000 stars, and those taken of the Milky Way could contain close to a million. It took Tombaugh up to a week to examine each pair of exposures. Late in the afternoon on February 18, 1930, the 24-year-old Tombaugh was gazing into the eyepiece of a Zeiss Blink microscope at photographic images of a star field, examining a pair of plates taken in mid-January. Suddenly the monotony was broken when his attention was caught by one of the millions of minute specks of lights whose image had moved slightly between one photograph and the next. He checked and rechecked his photographs for 45 minutes before calling his supervisors.

He knew he had found Planet X. The observatory staff watched the star for a few weeks to confirm the movement, and on March 13, 1930, the discovery of the ninth planet was officially announced. Front page headlines around the world heralded the discovery. The name for the new planet was suggested by a young schoolgirl from England. She thought that because the planet was so far away from the sun and in its own dark world, it should be named for the Greek god of the underworld, Pluto, which was announced May 1, 1930. Tombaugh went from being an anonymous planet hunter to an internationally famous astronomer over night. On the heels of his discovery, Tombaugh received an offer of a scholarship for the University of Kansas University, which he accepted. He went on to earn degrees from KU and Northern Arizona University. He concluded his career as an astronomy professor at New Mexico State University. He is credited with the discovery of several galactic star clusters, hundreds of asteroids, a comet, a cluster of 1,800 galaxies and other observations. Tombaugh died January 17, 1997.

By the early 21st century many more objects of Pluto's size were discovered. In 2006 the International Astronomical Union officially defined the term planet and Pluto was determined to be the second-largest dwarf planet, and tenth largest body orbiting the Sun. February 18, 1930 : Pluto discovered Introduction Pluto, once believed to be the ninth planet, is discovered at the Lowell Observatory in Flagstaff, Arizona, by astronomer Clyde W. Tombaugh. The existence of an unknown ninth planet was first proposed by Percival Lowell, who theorized that wobbles in the orbits of Uranus and Neptune were caused by the gravitational pull of an unknown planetary body. Lowell calculated the approximate location of the hypothesized ninth planet and searched for more than a decade without success. However, in 1929, using the calculations of Powell and W.H. Pickering as a guide, the search for Pluto was resumed at the Lowell Observatory in Arizona. On February 18, 1930, Tombaugh discovered the tiny, distant planet by use of a new astronomic technique of photographic plates combined with a blink microscope.

His finding was confirmed by several other astronomers, and on March 13, 1930–the anniversary of Lowell’s birth and of William Hershel’s discovery of Uranus–the discovery of Pluto was publicly announced. With a surface temperature estimated at approximately -360 Fahrenheit, Pluto was appropriately given the Roman name for the god of the underworld in Greek mythology. Pluto’s average distance from the sun is nearly four billion miles, and it takes approximately 248 years to complete one orbit. It also has the most elliptical and tilted orbit of any planet, and at its closest point to the sun it passes inside the orbit of Neptune, the eighth planet. After its discovery, some astronomers questioned whether Pluto had sufficient mass to affect the orbits of Uranus and Neptune. In 1978, James Christy and Robert Harrington discovered Pluto’s only known moon, Charon, which was determined to have a diameter of 737 miles to Pluto’s 1,428 miles. Together, it was thought that Pluto and Charon formed a double-planet system, which was of ample enough mass to cause wobbles in Uranus’ and Neptune’s orbits.

In August 2006, however, the International Astronomical Union announced that Pluto would no longer be considered a planet, due to new rules that said planets must “clear the neighborhood around its orbit.” Since Pluto’s oblong orbit overlaps that of Neptune, it was disqualified. Article Details: February 18, 1930 : Pluto discovered Author February 18, 1930 : Pluto discovered URL A Day in History… February 18 — Clyde Tombaugh, 1st Photographed Pluto - Prof. Boerner's Explorations Prof. Boerner's Explorations Commentary: For years before the (former) planet Pluto was observed on photographic film, it was predicted by Percival Lowell and William Pickering and its basic orbit was known. How could such a feat be accomplished? Not by magic, but by careful measurement of its neighboring planet, Neptune’s orbit. Anomalies were observed that could only be explained by another planet-like entity in relative proximity to Neptune. In 1930 a young astronomer working at the Lowell Observatory in Flagstaff, Arizona photographed the area of the sky in which the new planet should have been.

After doing this for several nights in succession, he compared the images, he found an object moving in that portion of the sky. The new planet was confirmed; our solar systems ninth planet, was discovered. Its name, Pluto, was among many suggestions submitted. The name Pluto was proposed by Venetia Burney, an eleven-year-old schoolgirl in Oxford, England. I learned about this in school and I loved the story. Then, after extensive study, Pluto was downgraded from a planet to a dwarf planet in 2006 when the International Astronomical Union (IAU) defined what it means to be a "planet" within the Solar System. I will probably continue to think of Pluto even though it may not actually be classified as such. Now let’s jump into our exploration of the discovery of Pluto… GLB These Introductory Comments are copyrighted: Copyright©2011 — Gerald Boerner — All Rights Reserved [ 3676 Words ] “Astronomy teaches the correct use of the sun and the planets.” — Stephen Leacock “Planets move in ellipses with the Sun at one focus.” — Johannes Kepler “A time will come when men will stretch out their eyes.

They should see planets like our Earth.” — Christopher Wren “I am sorry to say that there is too much point to the wisecrack that life is extinct on other planets because their scientists were more advanced than ours.” — John F. Kennedy “In so many and such important ways, then, do the planets bear witness to the earth’s mobility.” — Nicolaus Copernicus “Accordingly, since nothing prevents the earth from moving, I suggest that we should now consider also whether several motions suit it, so that it can be regarded as one of the planets. For, it is not the center of all the revolutions.” — Nicolaus Copernicus “The planets are never the same twice, they’re always different, so they could compare the markings I had drawn with their current photographs and they knew that I was drawing what I was really seeing and it wasn’t copied from somewhere.” — Clyde Tombaugh “I used to think about how nice it would be to visit the planets. Of course, I didn’t expect to see in my lifetime what has happened. I knew it would happen some day, but it came along faster than I at first thought.” — Clyde Tombaugh Clyde W.

Tombaugh, Astronomer who First Photographed Pluto Pluto, formal designation 134340 Pluto, is the second most massive known dwarf planet in the Solar System (after Eris) and the tenth most massive body observed directly orbiting the Sun. Originally classified as a planet, Pluto is now considered the largest member of a distinct population known as the Kuiper belt. Like other members of the Kuiper belt, Pluto is composed primarily of rock and ice and is relatively small: approximately a fifth the mass of the Earth’s Moon and a third its volume. It has an eccentric and highly inclined orbit that takes it from 30 to 49 AU (4.4–7.4 billion km) from the Sun. This causes Pluto to periodically come closer to the Sun than Neptune. From its discovery in 1930 until 2006, Pluto was considered the Solar System’s ninth planet. In the late 1970s, following the discovery of minor planet 2060 Chiron in the outer Solar System and the recognition of Pluto’s relatively low mass, its status as a major planet began to be questioned.

In the late 20th and early 21st century, many objects similar to Pluto were discovered in the outer Solar System, notably the scattered disc object Eris in 2005, which is 27% more massive than Pluto. On August 24, 2006, the International Astronomical Union (IAU) defined what it means to be a "planet" within the Solar System. This definition excluded Pluto as a planet and added it as a member of the new category "dwarf planet" along with Eris and Ceres. After the reclassification, Pluto was added to the list of minor planets and given the number 134340. A number of scientists continue to hold that Pluto should be classified as a planet. Pluto and its three known moons Pluto and its largest moon, Charon, are sometimes treated as a binary system because the barycenter of their orbits does not lie within either body. The IAU has yet to formalize a definition for binary dwarf planets, and until it passes such a ruling, they classify Charon as a moon of Pluto. Pluto has two known smaller moons, Nix and Hydra, discovered in 2005.

Discovery of Pluto In the 1840s, using Newtonian mechanics, Urbain Le Verrier predicted the position of the then-undiscovered planet Neptune after analysing perturbations in the orbit of Uranus. Subsequent observations of Neptune in the late 19th century caused astronomers to speculate that Uranus’ orbit was being disturbed by another planet besides Neptune. In 1906, Percival Lowell, a wealthy Bostonian who had founded the Lowell Observatory in Flagstaff, Arizona in 1894, started an extensive project in search of a possible ninth planet, which he termed "Planet X". By 1909, Lowell and William H. Pickering had suggested several possible celestial coordinates for such a planet. Lowell and his observatory conducted his search until his death in 1916, but to no avail. Unknown to Lowell, on March 19, 1915, his observatory had captured two faint images of Pluto, but did not recognize them for what they were.

Due to a ten-year legal battle with Constance Lowell, Percival’s widow, who attempted to wrest the observatory’s million-dollar portion of his legacy for herself, the search for Planet X did not resume until 1929, when its director, Vesto Melvin Slipher, summarily handed the job of locating Planet X to Clyde Tombaugh, a 23-year-old Kansas man who had just arrived at the Lowell Observatory after Slipher had been impressed by a sample of his astronomical drawings. Tombaugh’s task was to systematically image the night sky in pairs of photographs taken two weeks apart, then examine each pair and determine whether any objects had shifted position. Using a machine called a blink comparator, he rapidly shifted back and forth between views of each of the plates, to create the illusion of movement of any objects that had changed position or appearance between photographs. On February 18, 1930, after nearly a year of searching, Tombaugh discovered a possible moving object on photographic plates taken on January 23 and January 29 of that year. A lesser-quality photograph taken on January 21 helped confirm the movement.

After the observatory obtained further confirmatory photographs, news of the discovery was telegraphed to the Harvard College Observatory on March 13, 1930. Naming the Planet The discovery made headlines across the globe. The Lowell Observatory, who had the right to name the new object, received over 1000 suggestions from all over the world, ranging from Atlas to Zymal. Tombaugh urged Slipher to suggest a name for the new object quickly before someone else did. Constance Lowell proposed Zeus, then Percival and finally Constance – her own first name. These suggestions were disregarded. Venetia Burney The name Pluto was proposed by Venetia Burney (1918–2009), an eleven-year-old schoolgirl in Oxford, England. Venetia was interested in classical mythology as well as astronomy, and considered the name, that of the Roman god of the underworld, appropriate for such a presumably dark and cold world. She suggested it in a conversation with her grandfather Falconer Madan, a former librarian at the University of Oxford’s Bodleian Library. Madan passed the name to Professor Herbert Hall Turner, who then cabled it to colleagues in the United States.

The object was officially named on March 24, 1930. Each member of the Lowell Observatory was allowed to vote on a short-list of three: Minerva (which was already the name for an asteroid), Cronus (which had lost reputation through being proposed by the unpopular astronomer Thomas Jefferson Jackson See), and Pluto. Pluto received every vote. The name was announced on May 1, 1930. Upon the announcement, Madan gave Venetia five pounds as a reward. The name was soon embraced by wider culture. In 1930, Walt Disney introduced for Mickey Mouse a canine companion, named Pluto apparently in the object’s honor, although Disney animator Ben Sharpsteen could not confirm why the name was given. In 1941, Glenn T. Seaborg named the newly created element plutonium after Pluto, in keeping with the tradition of naming elements after newly discovered planets, such as uranium, which was named after Uranus, and neptunium, which was named after Neptune. the discoverer of Pluto Once found, Pluto’s faintness and lack of a resolvable disc cast doubt on the idea that it was Lowell’s Planet X.

Estimates of Pluto’s mass were revised downward throughout the 20th century. In 1978, the discovery of Pluto’s moon Charon allowed the measurement of Pluto’s mass for the first time. Its mass, roughly 0.2% that of the Earth, was far too small to account for the discrepancies in the orbit of Uranus. Subsequent searches for an alternate Planet X, notably by Robert Sutton Harrington, failed. In 1992, Myles Standish used data from Voyager 2′s 1989 flyby of Neptune, which had revised the planet’s total mass downward by 0.5%, to recalculate its gravitational effect on Uranus. With the new figures added in, the discrepancies, and with them the need for a Planet X, vanished. Today, the majority of scientists agree that Planet X, as Lowell defined it, does not exist. Lowell had made a prediction of Planet X’s position in 1915 that was fairly close to Pluto’s actual position at that time; however, Ernest W. Brown concluded almost immediately that this was a coincidence, a view still held today.

Supporting Concepts Clyde William Tombaugh (1906 – 1997) was an American astronomer. Although he is best known for his discovery in 1930 of the dwarf planet Pluto, the first object to be discovered in what would later be identified as the Kuiper Belt, Tombaugh also discovered many asteroids; he also called for serious scientific research of unidentified flying objects. While a young researcher working for the Lowell Observatory in Flagstaff, Arizona, Tombaugh was given the job to perform a systematic search for a trans-Neptunian planet (also called Planet X), which had been predicted by Percival Lowell and William Pickering. Tombaugh used the observatory’s 13-inch astrograph to take photographs of the same section of sky several nights apart. He then used a blink comparator to compare the different images. When he shifted between the two images, a moving object, such as a planet, would appear to jump from one position to another, while the more distant objects such as stars would appear stationary. Tombaugh noticed such a moving object in his search, near the place predicted by Lowell, and subsequent observations showed it to have an orbit beyond that of Neptune.

This ruled out classification as an asteroid, and they decided this was the ninth planet that Lowell had predicted. The discovery was made on Tuesday, February 18, 1930, using images taken the previous month. The name "Pluto" was reportedly suggested by Venetia Burney, then an 11-year-old English school girl, who died in April 2009, having lived to see the reclassification of Pluto as a dwarf planet. It won out over numerous other suggestions partly because it was named after the Roman god of the underworld because he was able to render himself invisible and because Percival Lowell’s initials PL formed the first 2 letters. The name Pluto was officially adopted on May 1, 1930. Lowell Observatory is an astronomical observatory in Flagstaff, Arizona. Lowell Observatory was established in 1894, placing it among the oldest observatories in the United States, and was designated a National Historic Landmark in 1965. The Observatory’s original 24-inch (0.61 m) Alvan Clark Telescope is still in use today for public education.

Lowell Observatory hosts 70,000 visitors per year at their Steele Visitors Center who take guided daytime tours and view various wonders of the night sky through the Clark Telescope and other telescopes. It was founded by astronomer Percival Lowell, and run for a time by his third cousin Guy Lowell of Boston’s well-known Lowell family. The current trustee of Lowell Observatory is William Lowell Putnam, grandnephew of founder Percival Lowell and son of long-time trustee Roger Putnam. The position of trustee is historically handed down through the family. The observatory operates several telescopes at two locations in Flagstaff. The main facility, located on Mars Hill just west of downtown Flagstaff, houses the original 24-inch (0.61 m) Clark Refracting Telescope, although its role today is as a public education tool and not research. The telescope, built in 1896 for $20,000, was assembled in Boston by Alvan Clark and then shipped by train to Flagstaff. Also located on the Mars Hill campus is the 13-inch (0.33 m) Pluto Discovery Telescope, used by Clyde Tombaugh in 1930 to discover the dwarf planet Pluto.

A planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighboring region of planetesimals. The term planet is ancient, with ties to history, science, mythology, and religion. The planets were originally seen by many early cultures as divine, or as emissaries of the gods. As scientific knowledge advanced, human perception of the planets changed, incorporating a number of disparate objects. In 2006, the International Astronomical Union officially adopted a resolution defining planets within the Solar System. This definition has been both praised and criticized, and remains disputed by some scientists. The planets were thought by Ptolemy to orbit the Earth in deferent and epicycle motions. Though the idea that the planets orbited the Sun had been suggested many times, it was not until the 17th century that this view was supported by evidence from the first telescopic astronomical observations, performed by Galileo Galilei. By careful analysis of the observation data, Johannes Kepler found the planets’ orbits to be not circular, but elliptical.

As observational tools improved, astronomers saw that, like Earth, the planets rotated around tilted axes, and some share such features as ice-caps and seasons. Since the dawn of the Space Age, close observation by probes has found that Earth and the other planets share characteristics such as volcanism, hurricanes, tectonics, and even hydrology. Planets are generally divided into two main types: large, low-density gas giants, and smaller, rocky terrestrials. Under IAU definitions, there are eight planets in the Solar System. In order of increasing distance from the Sun, they are the four terrestrials, Mercury, Venus, Earth, and Mars, then the four gas giants, Jupiter, Saturn, Uranus, and Neptune. Six of the planets are orbited by one or more natural satellites. Additionally, the Solar System also contains at least five dwarf planets and hundreds of thousands of small Solar System bodies. A dwarf planet, as defined by the International Astronomical Union (IAU), is a celestial body orbiting the Sun that is massive enough to be spherical as a result of its own gravity but has not cleared its neighboring region of planetesimals and is not a satellite.

More explicitly, it has to have sufficient mass to overcome its compressive strength and achieve hydrostatic equilibrium. The term dwarf planet was adopted in 2006 as part of a three-way categorization of bodies orbiting the Sun, brought about by an increase in discoveries of trans-Neptunian objects that rivaled Pluto in size, and finally precipitated by the discovery of an even more massive object, Eris. This classification states that bodies large enough to have cleared the neighborhood of their orbit are defined as planets, while those that are not massive enough to be rounded by their own gravity are defined as small solar system bodies. Dwarf planets come in between. The definition officially adopted by the IAU in 2006 has been both praised and criticized, and has been disputed by scientists such as Alan Stern. Asteroids, sometimes grouped with centaurs, Neptune trojans and trans-Neptunian objects into minor planets or planetoids, are a class of small Solar System bodies in orbit around the Sun.

The term "asteroid" was historically applied to any astronomical object orbiting the Sun that was not observed to have the characteristics of an active comet or a planet, but it has increasingly come to particularly refer to the small rocky and metallic bodies of the inner Solar System and out to the orbit of Jupiter. As small objects in the outer Solar System have begun to be discovered their observed composition differs from the objects historically termed asteroids. Harbouring predominantly volatiles-based material similar to comets rather than the more familiar rocky or metallic asteroids, they are often distinguished from them. There are millions of asteroids, and like most other small Solar System bodies the asteroids are thought to be remnants of planetesimals, material within the young Sun’s solar nebula that have not grown large enough to form planets. The large majority of known asteroids orbit in the main asteroid belt between the orbits of Mars and Jupiter, however many different orbital families exist with significant populations including Jupiter Trojans and near-Earth asteroids. Individual asteroids are categorized by their characteristic spectra, with the majority falling into three main groups: C-type, S-type, and M-type. These are generally identified with carbon-rich, stony, and metallic compositions respectively.

The Kuiper belt , sometimes called the Edgeworth–Kuiper belt, is a region of the Solar System beyond the planets extending from the orbit of Neptune (at 30 AU) to approximately 55 AU from the Sun. It is similar to the asteroid belt, although it is far larger—20 times as wide and 20–200 times as massive. Like the asteroid belt, it consists mainly of small bodies, or remnants from the Solar System’s formation. While the asteroid belt is composed primarily of rock and metal, the Kuiper objects are composed largely of frozen volatiles (termed "ices"), such as methane, ammonia and water. The belt is home to at least three dwarf planets – Pluto, Haumea, and Makemake. Some of the Solar System’s moons, such as Neptune’s Triton and Saturn’s Phoebe, are also believed to have originated in the region. Since the belt was discovered in 1992, the number of known Kuiper belt objects (KBOs) has increased to over a thousand, and more than 70,000 KBOs over 100 km (62 mi) in diameter are believed to exist.

The Kuiper belt was initially believed to be the main repository for periodic comets, those with orbits lasting less than 200 years. However, studies since the mid-1990s have shown that the Kuiper belt is dynamically stable, and that their true place of origin is the farther scattered disc, a dynamically active region created by the outward motion of Neptune 4.5 billion years ago; scattered disc objects such as Eris are KBO-like bodies with extremely large orbits that take them as far as 100 AU from the Sun. Pluto is the largest known member of the Kuiper belt. Originally considered a planet, Pluto’s position as part of the Kuiper belt has caused it to be reclassified as a "dwarf planet". It is compositionally similar to many other objects of the Kuiper belt, and its orbital period is identical to that of the KBOs known as "plutinos". In Pluto’s honor, the four currently accepted dwarf planets beyond Neptune’s orbit are called "plutoids". Please take time to further explore more about PLUTO, CLYDE W.

TOMBAUGH, LOWELL OBSERVATORY, KUIPER BELT, PLANET, DWARF PLANET, ASTEROID, WHITE SANDS MISSILE RANGE by accessing the Wikipedia articles referenced below… Other Events on this Day: In 1735… The first opera performance in America, Flora, or Hob in the Well, is presented in Charleston, South Carolina. In 1841… The first continuous filibuster begins in the Senate and lasts until March 11. In 1885… Mark Twain’s The Adventures of Huckleberry Finn, the great American novel, is published. In 1930… Astronomer Clyde W. Tombaugh observes the first photographic evidence of the ninth planet in our solar system at the Lowell Observatory in Flagstaff, Ariz. An 11-year-old English girl, Venetia Burney, suggests the name Pluto and lives to see it named a planet and then, in 2006, downgraded to a “dwarf” planet. Venetia Burney Phair died in 2009; a student-built science instrument on a recent mission to Pluto was named in her honor.

In 1977… The first space shuttle, Enterprise, takes its maiden test flight, attached to the top of a Boeing 747. In 2001… At age 49, NASCAR driver Dale Earnhardt Sr. dies from head injuries suffered during a last-lap crash at the Daytona 500 in Daytona Beach, Fla. His son Dale Earnhardt Jr. finishes the race in second place, following winner Michael Waltrip. In 2006… Shani Davis of the United States wins the 1,000-meter speed skating event at the Winter Olympic Games in Turin, Italy, becoming the first black athlete to win an individual gold medal at the Winter Olympics. Four years later, Davis will successfully defend his title at the Games in Vancouver, Canada. Dates and events based on: William J. Bennett and John Cribb, (2008) The American Patriot’s Almanac Daily Readings on America.

(Kindle Edition) Background information is from Wikipedia articles on: Wikipedia: Pluto… Clyde Tombaugh – IIT-Vidya Blog Clyde Tombaugh Clyde William Tombaugh (February 4, 1906 – January 17, 1997) was an American astronomer. Although he is best known for discovering the dwarf-planet Pluto in 1930, the first object to be discovered in what would later be identified as the Kuiper belt, Tombaugh also discovered many asteroids; he also called for the serious scientific research of unidentified flying objects, or “U.F.O.s”. American astronomer who discovered Pluto in 1930 after a systematic search for a ninth planet instigated by the predictions of other astronomers. He also discovered several clusters of stars and galaxies, studied the apparent distribution of extragalactic nebulae, and made observations of the surfaces of Mars, Venus, Jupiter, Saturn, and the Moon. Biography: Tombaugh was born in Streator, Illinois. After his family moved to Burdett, Kansas in 1922, Tombaugh’s plans for attending college were frustrated when a hailstorm ruined his family’s farm crops.

Starting in 1926, he built several telescopes with lenses and mirrors by himself. He sent drawings of Jupiter and Mars to the Lowell Observatory, which offered him a job. Tombaugh worked there from 1929 to 1945. Following his discovery of Pluto, Tombaugh earned bachelor’s and master’s degrees in astronomy from the University of Kansas in 1936 and 1938. During World War II he taught naval personnel navigation at Northern Arizona University. He worked at White Sands Missile Range in the early 1950s, and taught astronomy at New Mexico State University from 1955 until his retirement in 1973. Tombaugh initially had no formal training in astronomy, only a keen interest that had been sharpened by his first glimpse of the heavens through his uncle’s telescope. After finishing high school, Tombaugh built his own telescope according to specifications published in a 1925 issue of Popular Astronomy. Using this instrument, he made observations of Jupiter and Mars and sent sketches of these planets to Lowell Observatory in Flagstaff, Ariz., hoping to receive advice about his work. Instead, he received a job offer.

Tombaugh’s assignment was to locate the ninth planet, a search instigated in 1905 by astronomer Percival Lowell. To carry out this task, Tombaugh used a 33-cm (13-inch) telescope to photograph the sky and an instrument called a blink comparator to examine the photographic plates for signs of moving celestial bodies. On Feb. 18, 1930, Tombaugh pinpointed Pluto, and on March 13 Lowell Observatory announced the discovery of the new planet. (In 2006 Pluto was reclassified as a dwarf planet.) The asteroid 1604 Tombaugh, discovered in 1931, is named after him. He discovered hundreds of asteroids, beginning with 2839 Annette in 1929, mostly as a by-product of his search for Pluto and his searches for other celestial objects. Tombaugh named some of them after his wife, children and grandchildren. The Royal Astronomical Society awarded him the Jackson-Gwilt Medal in 1931.

After his discovery, Tombaugh attended the University of Kansas on a scholarship, returning each summer to the observatory until completing (1939) his M.A. in astronomy. Upon graduating, he returned to the observatory and continued his patrol of the skies, cataloging more than 30,000 celestial objects before he left in 1946. His observations of Mars led him to conclude in 1950 that the surface of the planet was pitted with craters as a result of its proximity to the asteroid belt, a prediction borne out by images taken by the Mariner 4 space probe in the 1960s. Tombaugh also taught at Arizona State College and at the University of California, Los Angeles, and he worked as an astronomer and optical physicist at the White Sands Missile Range near Las Cruces, N.M., where he helped set up an optical tracking system to follow ballistic missiles. He joined the faculty of New Mexico State University in 1955 and there instituted a major program of planetary research. He retired in 1973 but remained involved as an observer and adviser at the university.

Death: Tombaugh died on January 17, 1997, when he was in Las Cruces, New Mexico, at the age of 90. A small portion of his ashes were placed aboard the New Horizons spacecraft. The container includes the inscription: “Interned (sic) herein are remains of American Clyde W. Tombaugh, discoverer of Pluto and the solar system’s ‘third zone’. Adelle and Muron’s boy, Patricia’s husband, Annette and Alden’s father, astronomer, teacher, punster, and friend: Clyde W. Tombaugh (1906–1997)”. Tombaugh was survived by his widow, Patricia (1912–2012), and their children, daughter Annette and son Alden. Tombaugh was an active Unitarian-Universalist. Discovery of Pluto: While a young researcher working for the Lowell Observatory in Flagstaff, Arizona, Tombaugh was given the job to perform a systematic search for a trans-Neptunian planet (also called Planet X), which had been predicted by Percival Lowell and William Pickering.

Tombaugh used the observatory’s 13-inch astrograph to take photographs of the same section of sky several nights apart. He then used a blink comparator to compare the different images. When he shifted between the two images, a moving object, such as a planet, would appear to jump from one position to another, while the more distant objects such as stars would appear stationary. Tombaugh noticed such a moving object in his search, near the place predicted by Lowell, and subsequent observations showed it to have an orbit beyond that of Neptune. Following the discovery, starting in the 1990s, of other Kuiper belt objects, Pluto began to be seen not as a planet orbiting alone at 40 AU, but as the largest of a group of icy bodies in that region of space. After it was shown that at least one such body was larger than Pluto, on August 24, 2006 the International Astronomical Union (IAU) reclassified Pluto, grouping it with two similarly sized “dwarf planets” rather than with the eight “classical planets”.

Further search: Tombaugh continued searching for some years after the discovery of Pluto, and the lack of further discoveries left him satisfied that no other object of a comparable apparent magnitude existed near the ecliptic. No more trans-Neptunian objects were discovered until (15760) 1992 QB1, in 1992. However, more recently the relatively bright object Makemake has been discovered. It has a relatively high orbital inclination, but at the time of Tombaugh’s discovery of Pluto, Makemake was only a few degrees from the ecliptic near the border of Taurus and Auriga at an apparent magnitude of 16. This position was also very near the galactic equator, making it almost impossible to find such an object within the dense concentration of background stars of the Milky Way. Share this: Clyde Tombaugh | Article about Clyde Tombaugh by The Free Dictionary Clyde Tombaugh | Article about Clyde Tombaugh by The Free Dictionary Related to Clyde Tombaugh: Percival Lowell Tombaugh, Clyde William (tŏm`bô), 1906–97, American astronomer, b. Streator, Ill.

Although lacking formal training or a college degree, he was hired in 1929 as an assistant by the Lowell Observatory Lowell Observatory, astronomical observatory located in Flagstaff, Ariz.; it was founded in 1894 by Percival Lowell, the American astronomer who popularized the idea that Mars might support intelligent life. Its original telescope, still in operation, is a 24-in. ..... Click the link for more information. to continue the search for a planet beyond Neptune, which had been initiated by Percival Lowell Lowell, Percival, 1855–1916, American astronomer, b. Boston, grad. Harvard, 1876; brother of Abbott Lawrence Lowell and Amy Lowell. He visited Korea and Japan, where he acted as counselor and foreign secretary to the Korean Special Mission to the United States and wrote ..... Click the link for more information. . Tombaugh used a blink microscope blink microscope, in astronomy, device for determining a change in position or magnitude (brightness) of a star relative to other stars in the background. Two photographs of the same field or area of the sky are projected so that they precisely coincide. ..... Click the link for more information.

to compare photographs of a small part of the night sky and detect the planet. After ten months of painstaking comparisons, on Feb. 18, 1930, he found Pluto Pluto, in astronomy, a dwarf planet and the first Kuiper belt, or transneptunian, object (see comet) to be discovered (1930) by astronomers. Pluto has an elliptical orbit usually lying beyond that of Neptune. ..... Click the link for more information. (now regarded as a Kuiper belt object [see comet comet [Gr.,=longhaired], a small celestial body consisting mostly of dust and gases that moves in an elongated elliptical or nearly parabolic orbit around the sun or another star. Comets visible from the earth can be seen for periods ranging from a few days to several months. ..... Click the link for more information. ] and a dwarf planet dwarf planet, a nonluminous body of rock or gas that orbits the sun and has a rounded shape due to its gravity. Unlike a planet, a dwarf planet is not capable of clearing its orbit of smaller objects by collision, capture, or other means. ..... Click the link for more information. ) in the constellation Gemini.

After several weeks of observation by the observatory staff to validate the discovery, it was announced on Mar. 13, the 75th anniversary of Lowell's birth. Tombaugh received a scholarship from the Univ. of Kansas, where he obtained his bachelor's (1936) and master's (1939) degrees. He subsequently returned to the observatory and also held several academic posts. He focused on planetary observations, particularly of Mars, and in 1965 images returned by the space probe Mariner 4 confirmed his prediction that the Martian surface would have craters caused by asteroid impacts. He wrote Out of the Darkness: The Planet Pluto (1980) with Patrick Moore. Bibliography See biography by D. H. Levy (1992).

Question: Which heavenly body was discovered by astronomer Clyde W Tombaugh on 18 February 1930?
Answer: Pluto