-------------------------------------------------------------------------------- 1 Sometimes what you don't know can be a lot more interesting than what you do know. Take Pluto for instance.
2 What We Know
3 Pluto is no bigger than the Earth's moon. Its gravity is about one-fifteenth of Earth's. Pluto is, on the average, about 5,913,000,000 kilometers from the sun. It revolves around the sun once every 248 Earth years, and rotates on its axis once every six and one-half earth days. It has a very elliptical, or egg shaped, orbit. In fact, Pluto's orbit actually crosses Neptune's orbit, making it closer to the sun than Neptune for 20 years out of its 248 year rotation. Pluto's orbit is also tilted; it is not in the same plane as the orbits of all of the other planets.
4 Photographs taken by the Hubble Space Telescope show that Pluto's surface has large light and dark areas. Pluto's surface is believed to be made up of ice and rock. It probably has some type of thin atmosphere. Pluto has one moon, named Charon.
5 Pluto was discovered on February 18, 1930 by Clyde Tombaugh at the Lowell Observatory, which is named after Percival Lowell, who had been searching for a ninth planet since the early 1900's.
6 Pluto is the only planet never explored by even a fly-by space probe.
7 What We Don't Know
8 There is a lot that we don't know about Pluto. Since it is so far away, it looks like just a little dot through the best Earth telescopes. Even the Hubble photos only get close enough to show large areas of light and dark over the whole planet. We don't know what Pluto's surface looks like or what it is made of. We don't know much about the make-up of its atmosphere either. No one knows much of anything about the inside, or core, of the planet.
9 Estimates of Pluto's size keep getting smaller as scientists become more accurate in their measurements, so maybe we still don't really know how big it is either.
10 There are a lot of things scientists still don't know about Pluto's unusual orbit. For a planet as far away as Pluto, what they do know comes mainly from mathematical calculations. Pluto's orbit never matches the calculations exactly; it always leaves a little mystery for the scientists to ponder.
11 This is just the beginning of what we don't know about Pluto. Here is the really big thing that we don't know about Pluto; we don't know whether Pluto is really a planet! There are several reasons why some scientists say that Pluto is not really a planet. It is very small for a planet. It has that strange, elliptical, tilted orbit. Its surface of rock and ice reminds scientists of the moons of the outer planets more than of a planet itself.
12 Here are some of their theories about what Pluto really is:
Pluto is a planet. Pluto and its moon, Charon, are twin planets revolving around each other. Pluto used to be one of Neptune's moons, but it escaped Neptune's gravity. Pluto is just one of the many rocky comets that orbit the sun out beyond the planets. 13 Scientists hope that, in a few years, a space probe nicknamed the Pluto Express will be blasting off to explore Pluto, its moon Charon, and space beyond Pluto. Maybe then we will begin to know more about the mysterious planet (or is it?) Pluto.
5. The statement " Pluto and Charon are twin planets." is a _____. Metaphor Mistake Fact Theory
6. Which happened second. Percival Lowell searched for a ninth planet. Clyde Tombaugh discovered Pluto. The Hubble Space Telescope photographed Pluto. The Pluto Express blasted off.
7. From this article, you can infer that _____. Neptune is really the 9th planet Scientists are not very interested in Pluto Pluto is the final planet in the solar system Scientists don't know as much about Pluto as the other planets
8. The main idea of this article is _____. Clyde Tombaugh should be more famous than he is There is a lot that we don't know about Pluto Pluto is really a comet and not a planet Pluto is the smallest planet
Pluto - Answer Key
1 5,913,000,000 2 False 3 False 4 False 5 Theory 6 Clyde Tombaugh discovered Pluto. 7 Scientists don't know as much about Pluto as the other planets 8 There is a lot that we don't know about Pluto
Name _____________________________ Date ___________________ Pluto (Answer ID # 0434499)
Complete and show your work.
1. Pluto has an estimated diameter of 1420 miles, approximately 1/5 the diameter of the Earth. Using the estimated diameter of Pluto, what is the circumference of the Earth? Round your answer to the nearest hundredth.
2. Pluto is 39 times as far from the sun as the Earth is. If Pluto is 5.91 x 109 kilometers from the sun, how far from the sun is the Earth?
3. Once every 248 years Pluto's orbit brings it inside Neptune's orbit. It stays inside Neptune's orbit for approximately 20 years. The last time this happened was in 1979. What year will it be when Pluto pass into Neptune's orbit for the 5th time?
4. Pluto revolves around the sun once every 248 Earth years. How many times does Pluto revolve around the sun in 3,968 Earth years?
5. Pluto is 5,913,000,000 kilometers from the sun. Express Pluto's distance from the sun in scientific notation.
6. Scientists believe that the temperature on Pluto may be as cold as –390F. The temperature on Mercury may rise as high as 800F. If today's temperatures on Pluto and Mercury are -350F and 746F, respectively. What is the difference between the two temperatures?
Answer Key 1 22294 miles 2 1.52 x 108 km 3 3219 4 16 times 5 5.913 x 109 km 6 1096 degrees Fahrenheit
GENERAL INFORMATION Pluto is the ninth and usually the farthest planet from the sun in our solar system. It is also the smallest planet in our solar system and the last to be discovered. It is smaller than a lot of the other planets' moons, including our moon. Pluto is the only planet in our solar system that has not been visited by our spacecraft yet. We only have blurry pictures of its surface; even the Hubble Space Telescope orbiting the Earth can only get grainy photos because Pluto is so far from us.
SIZE Pluto is about 1,413 miles (2274 km) in diameter. This is about 1/5 the diameter of the Earth. Pluto is the smallest planet in our Solar System.
MASS AND GRAVITY Pluto's mass is about 1.29 x 1022 kg. This is about 1/500th of the mass of the Earth. The gravity on Pluto is 8% of the gravity on Earth.
Pluto is the least massive planet in our Solar System
A 100 pound person on Pluto would weigh only 8 pounds.
LENGTH OF A DAY AND YEAR ON PLUTO Each day on Pluto takes 6.39 Earth days. Each year on Pluto takes 247.7 Earth years (that is, it takes 247.7 Earth years for Pluto to orbit the Sun once).
PLUTO'S ORBIT Pluto is 39 times farther from than the sun than the Earth is. Pluto ranges from 2.8 to 4.6 billion miles (4.447 billion to 7.38 billion km) from the Sun. From Pluto, the sun would look like a tiny dot in the sky.
Occasionally, Neptune's orbit is actually outside that of Pluto; this is because of Pluto's highly eccentric (non-circular) orbit. During this time (20 years out of every 248 Earth years), Neptune is actually the farthest planet from the Sun (and not Pluto). From January 21, 1979 until February 11, 1999, Pluto was inside the orbit of Neptune. Now and until September 2226, Pluto is outside the orbit of Neptune.
Orbital Eccentricity Pluto has a very eccentric orbit; that means that its distance from the sun varies a lot during its orbit around the sun. Sometimes it is even closer to the Sun than the planet Neptune (it was that way from January 1979 to February 11, 1999)! Pluto also rotates about its axis in the opposite direction from most of the other planets.
Orbital Inclination Pluto's orbit is tilted from the plane of the ecliptic. This angle, its orbital inclination, is 17.15°. This is the largest inclination of any of the planets.
TEMPERATURE ON PLUTO Pluto is VERY, VERY cold. Its temperature may range from between -396°F to -378°F (-238°C to -228°C, or 35 K to 45 K). The average temperature is -393°F (-236°C = 37 K).
PLANETARY COMPOSITION Pluto's composition is unknown. It is probably made up of about 70% rock and 30% water. This is determined from density calculations; Pluto's density is about 2,000 kg/m3. There may be methane ice together with frozen nitrogen and carbon dioxide on the cold, rocky surface.
ATMOSPHERE Not much is known about Pluto's atmosphere. It is probably mostly nitrogen with a little carbon monoxide and methane - definitely not breatheable by humans. The atmospheric pressure is probably very low. The atmosphere forms when Pluto is closest to the Sun and the frozen methane is vaporized by the solar heat. When it is farther from the Sun, the methane freezes again. From Pluto, the sky would appear black, even when the Sun (the size of a star) is up.
PLUTO'S MOON Pluto has one moon, Charon, that is almost as big as Pluto itself. Although Charon is small, about 1,172 km (728 miles) in diameter, it about half of the size of Pluto itself. Charon orbits about 19,640 km from Pluto on average. It may be covered by water ice and probably has no atmosphere. Charon is in a synchronous orbit around Pluto. That is, Charon is always over the same spot on Pluto; Charon's orbit takes exactly one Pluto day.
Charon was discovered by Jim Christy in 1978. Charon was named after the mythological demon who ferried people across the mythological river Styx into Hades.
DISCOVERY OF PLUTO Pluto was the last planet to be discovered. Planet "X" was the temporary name given to the then-unknown planet beyond Neptune that disturbed the orbits of Uranus and Neptune. Percival Lowell calculated the rough location of Planet "X's" orbit, but died in 1916 before it was found. This planet was eventually found by the American astronomer Clyde W. Tombaugh in 1930 and named Pluto. He did his observations at the Lowell Observatory in Arizona.
Pluto was named after the Roman god of the underworld, Pluto. Its symbol is the combined letters "P" and "L," either for Percival Lowell or for Pluto.
The name Pluto was suggested by Venetia Burney of England, who was 11 years old at the time. She suggested the name to her grandfather, who was Librarian at Oxford. He passed her idea to the astronomers who were trying to name the newly-discovered planet.
PLUTO: PLANET, ASTEROID, OR TNO Pluto's unusual orbit makes some scientists think that Pluto is not a regular planet. but a "minor planet" or a Trans Neptunian Object (TNO) [Kuiper Belt objects left over from the formation of the solar system]. In the future, Pluto may be listed as an asteroid (it will probably be given the asteroid number 10,000) and also as the first TNO - it will also still be considered a planet, albeit an unusual one.
Pluto: Cloze Activity Fill in the blanks below. Answers Word Bank: Tombaugh farthest dot moon spacecraft mass gravity 8 1978 ninth direction Sun orbit Pluto asteroid
Pluto is the ________________________ and usually the ________________________ planet from the Sun in our Solar System; it is also the smallest planet in our Solar System. This cold, rocky planet was the last planet to be discovered. Clyde W. ________________________ discovered Pluto in 1930. Pluto is the only planet in our Solar System that has not been visited by our ________________________ yet. We only have blurry pictures of its surface. From Pluto, the Sun would look like a tiny ________________________ in the sky. Pluto is about 1,413 miles (2274 km) in diameter. This is about 1/5 the diameter of the Earth. It is smaller than a lot of the other planets' moons, including our ________________________.
Pluto's ________________________ is about 1.29 x 1022 kg; it is the least massive planet in our Solar System. Pluto is about 1/500th of the mass of the Earth. The ________________________ on Pluto is only 8% of the gravity on Earth. A 100 pound person on Pluto would weigh only ________________________ pounds.
Each day on Pluto takes 6.39 Earth days. Each year on Pluto takes 247.7 Earth years (that is, it takes 247.7 Earth years for Pluto to orbit the ________________________ once).
Pluto has a very eccentric ________________________; that means that its distance from the sun varies a lot during its orbit around the sun. Pluto also rotates about its axis in the opposite ________________________ from most of the other planets. Pluto's orbit is tilted from the plane of the ecliptic. This angle, its orbital inclination, is 17.15°. This is the largest inclination of any of the planets. Pluto's unusual orbit makes some scientists think that Pluto is not a regular planet, but perhaps an ________________________.
Pluto has one moon, Charon, that is almost as big as ________________________ itself. Charon was discovered by Jim Christy in ________________________. Charon was named after the mythological demon who ferried people across the mythological river Styx into Hades