26.1 Astronomical Units READ Talking and writing about distances in our solar system can be cumbersome. The Sun and Neptune are on average 4,500,000,000 (or four billion, five hundred million) kilometers apart. Earth’s average distance from the Sun is 150,000,000 (one hundred fifty million) kilometers. It can be difficult to keep track of all the zeroes in such large numbers. And it’s not easy to compare numbers that large. Astronomers often switch to astronomical units (abbreviated AU) when describing distances in our solar system. One astronomical unit is 150,000,000 km-the same as the distance from Earth to the Sun. Neptune is 30 AU from the Sun. Not only is 30 an easier number to work with than 4,500,000,000; but using astronomical units allows us to see immediately that Neptune is 30 times as far from the Sun as Earth. In this skill sheet, you will practice working with astronomical units. EXAMPLE Jupiter is 778 million kilometers from the Sun, on average. Find this distance in astronomical units. Solution: Divide 778 million km by 150 million km: 778,000,000 150,000,000-5.19 AU The average distance from Mars to the Sun is 1.52 AU. Find this distance in kilometers Solution: Multiply 1.52 AU by 150 million lam: 1.52 x 150,000,000-228,000,000 km PRACTICE 1. The average distance from Saturn to the Sun is 1.43 billion kilometers. Find this distance in astronomical units. The average distance from Venus to the Sun is 108 million kilometers. Find this distance in astronomical units Mercury’s average distance from the Sun is 0.387 astronomical units. How far is this in kilometers? The average distance from Uranus to the Sun is 19.13 astronomical units. How far is this in kilometers? Is the distance from Earth to the moon more or less than one astronomical unit? How do you know? Which planet is almost 20 times as far away from the Sun as Earth SUS Which planet is less than half as far away from the Sun as Earth? Which planet is almost twice as far from the Sun as Jupiter?term An unmanned spacecraft launched from Earth has traveled 10 astronomical units in the direction away from the Sun. It most recently passed through the orbit of which planet? 10. An unmanned spacecraft launched from Earth has traveled 0.5 astronomical units toward the Sun. Has it passed through the orbit of Venus yet?
The Correct Answer and Explanation is :
Let’s address each of the practice questions step by step:
- The average distance from Saturn to the Sun is 1.43 billion kilometers. Find this distance in astronomical units. To convert kilometers to astronomical units (AU), divide the distance in kilometers by the distance from Earth to the Sun (1 AU = 150,000,000 km): 1.43 * 10^9 / 150000000 = 9.533333333333333 AU Therefore, Saturn’s average distance from the Sun is approximately 9.53 AU.
- The average distance from Venus to the Sun is 108 million kilometers. Find this distance in astronomical units. Using the same conversion method: 108000000 / 150000000 = 0.72 AU Thus, Venus’s average distance from the Sun is 0.72 AU.
- Mercury’s average distance from the Sun is 0.387 astronomical units. How far is this in kilometers? To convert AU to kilometers, multiply the distance in AU by 150,000,000 km: 0.387 * 150000000 = 58050000.0 km Therefore, Mercury’s average distance from the Sun is approximately 58.05 million kilometers.
- The average distance from Uranus to the Sun is 19.13 astronomical units. How far is this in kilometers? Applying the same conversion: 19.13 * 150000000 = 2869500000.0 km Thus, Uranus’s average distance from the Sun is approximately 2.87 billion kilometers.
- Is the distance from Earth to the Moon more or less than one astronomical unit? How do you know? The average distance from Earth to the Moon is about 384,400 kilometers. Since 1 AU equals 150,000,000 km, the Moon’s distance is much less than one AU.
- Which planet is almost 20 times as far away from the Sun as Earth? Neptune is approximately 30.1 AU from the Sun, which is about 20 times Earth’s distance (1 AU). (Phys.org)
- Which planet is less than half as far away from the Sun as Earth? Mercury is about 0.387 AU from the Sun, which is less than half of Earth’s distance (1 AU). (Phys.org)
- Which planet is almost twice as far from the Sun as Jupiter? Saturn is approximately 9.58 AU from the Sun, which is about 1.8 times Jupiter’s average distance of 5.2 AU. (Phys.org)
- An unmanned spacecraft launched from Earth has traveled 10 astronomical units in the direction away from the Sun. It most recently passed through the orbit of which planet? After traveling 10 AU, the spacecraft would be between the orbits of Jupiter and Saturn. (Phys.org)
- An unmanned spacecraft launched from Earth has traveled 0.5 astronomical units toward the Sun. Has it passed through the orbit of Venus yet? Venus’s average distance from the Sun is 0.72 AU. Since the spacecraft has traveled 0.5 AU, it has not yet reached Venus’s orbit. (Phys.org)
Understanding astronomical units simplifies the comparison of distances within our solar system, as it provides a consistent scale based on Earth’s average distance from the Sun.