Orbits & Objects in Space

1. Orbits & Objects in Space

2. What is an orbit? • An orbit is a regular, repeating path that one object in space takes around another one. An object in an orbit is called a satellite. A satellite can be natural, like the Earth or the Moon. It can also be man-made, like the Space Shuttle or the ISS.—NASA

3. Satellites • A satellite is actually trying to travel in a straight line to conform to Newton's 1st law of motion (an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force). • However, the Earth's gravity is, at the same time, pulling the satellite down (the external force in Newton's law).

4. Satellites and Orbits • Imagine a firing a gun horizontally. • The bullet will eventually fall to Earth. But what if the bullet were travelling fast enough that it passed the horizon before starting to drop? • As the bullet fell to Earth, the curvature of the Earth would mean the ground was curving away underneath it.

5. Satellites and Orbits • Now, apply that to a satellite. If the satellite is travelling fast enough, the curvature of the Earth will cause the ground to fall away from beneath the satellite as gravity is pulling it down. This process continues, causing the satellite to orbit the Earth.

6. Orbits and Forces

7. Low Earth Orbit (LEO): Orbiting at an altitude of 600-1,000 km. LEO Path of Satellite 7

8. Types of Earth Orbits • LEO (Low Earth Orbit) • ~520-1,500 km altitude • Orbital period ~ninety minutes • MEO (Medium Earth Orbit) • ~20,000 km altitude • Between LEO and GEO • Orbital period ~5-6 hours

9. Types of Earth Orbits • HEO (High Earth Orbit or Highly Elliptical Orbit) • ~40,000 km altitude (at perigee) • Large dwell time over one hemisphere • Orbital period ~12-24 hours • GEO (Geosynchronous or Geostationary Earth Orbit) • ~36,000 km altitude • Orbital period ~24 hours (matches Earth’s rotation)

10. Planetary Orbits How do the planets stay in orbit around the sun? • The solar system was formed from a rotating cloud of gas and dust which spun around a newly forming star, our sun, at its center. • The planets all formed from this spinning disk-shaped cloud, and continued this rotating course around the sun after they were formed.

11. Planetary Orbits • The gravity of the sun attracts the planets and keeps the planets in their orbits. The stay in their orbits because there is no other force in the solar system which can stop them.   • In fact, the planets are constantly falling toward the sun in much the same way that a thrown ball falls down to the ground.

12. Planetary Orbits • When you throw a ball. it moves away from you and falls to the ground.  • If you throw the ball slowly, it lands on the ground a few feet from you. • If you throw it faster, it will fall farther away. • The faster you throw the ball, the farther it goes.

13. Planetary Orbits • Now imagine throwing the ball so fast that its path has the same shape as the curvature of the Earth. • Since the Earth is round, the ball you threw would fall all the way around the planet.  • If it goes fast enough to keep going around and around, the ball would stay in orbit.  The planets stay in orbit around the sun in the same way.

14. Our Solar System Our solar system is made up of: • Sun • Eight planets (Poor Pluto ) • Their moons • Asteroids • Comets

15. Planets A "planet” is a celestial body that: • (1) is in orbit around the Sun, • (2) has sufficient mass for its gravity to assume a nearly round shape • (3) has “cleared the neighborhood” around its orbit. • it has enough gravity that it does not share its orbit space with any other similarly sized body other than its own moons. (Pluto shares its orbit so it’s now a dwarf planet)

16. Inner Planets The inner four rocky planets at the center of the solar system are: • Mercury • Venus • Earth • Mars

17. Outer Planets The outer planets composed of gas are : • Jupiter • Saturn • Uranus • Neptune

18. Comets • The word "comet" comes from the Greek word for "hair.” • Our ancestors thought comets were stars with what looked like flowing hair trailing behind.

19. Comets: “Dirty Snowballs” • Comets are loose collections of ice, dust, and small rocky particles whose orbits are usually very long, narrow ellipses.

20. Structure of a Comet A Comet’s Head • Outer layer= Coma (water vapor, CO2, and other gases) • Solid inner core= Nucleus (frozen ice, gas and dust )

21. Comet’s Tail • As a comet approaches the sun and heats up, some of its gas and dust stream outward, forming a tail. • Most comets have 2 tails: • gas (ion),tail • dust tail • Tails point away from the sun because of the force of the solar wind. • A comet’s tail can be more than 100 million kilometers long.

22. Comet’s Tail

23. Comet’s Orbit • Comets move in an elliptical shaped orbit.

24. Origin of Comets • Most comets are found in 2 regions of the solar system: Kuiper belt and Oort cloud. • Kuiper belt-doughnut-shaped region that extends beyond Neptune’s orbit to about 100 times Earth’s distance from the sun. • populated with frozen bodies left over from the solar system's formation • Oort cloud-spherical region of comets that surrounds the solar system out to more than 1,000 times the distance between Pluto and the sun.

25. Famous Comets • Comet Halley is perhaps the most famous comet in history. • Each time this comet's orbit approaches the Sun, its 15-km (9-mile) nucleus sheds about 6 m (7 yards) of ice and rock into space. This debris forms an orbiting trail that, when falling to Earth, is called the Orionids meteor shower. • Halley’s comet reappears every 76 years. Its next appearance is in 2061.

26. July 23, 1995- an unusually large and bright comet was seen outside of Jupiter's orbit by Alan Hale of New Mexico and Thomas Bopp of Arizona. Exceptionally large size. It was visible even through bright city skies, and may have been the most viewed comet in recorded history. It will not appear again for another 2,400 years. Comet Hale-Bopp

27. Other Famous Comets • Comet Hyakutake-On January 30, 1996, Yuji Hyakutake (pronounced "hyah-koo-tah-kay"), an amateur astronomer from southern Japan, discovered a new comet using a pair of binoculars. • Comet Shoemaker-Levy 9-Between July 16 and July 22, 1994, more than 20 fragments of Comet Shoemaker-Levy 9 collided with the planet Jupiter. Astronomers Carolyn and Eugene Shoemaker and David Levy discovered the comet in 1993. It was the first collision of two Solar System bodies ever to be recorded.

28. Asteroids • A small and rocky space object that orbits the sun. • Most asteroids are found in the asteroidbelt. • The asteroid belt is located between the orbits of Mars and Jupiter. • Also called a “minor planet” or “planetoid” • Smaller than planets but larger than meteoroids

30. How many asteroids are there? • There are about 40,000 known asteroids that are over 0.5 miles (1 km) in diameter in the asteroid belt About 3,000 asteroids have been cataloged. • There are many smaller asteroids (100,000). • Asteroids are made of metals, silicate, iron, nickel, and carbon. • The first one discovered (and the biggest) is named Ceres; it was discovered in 1801. • Asteroids range in size from tiny pebbles to about 578 miles (930 kilometers) in diameter (Ceres).

31. ASTEROIDS BECOMING MOONS • Asteroids can be pulled out of their solar orbit by the gravitational pull of a planet. They would then orbit that planet instead of orbiting the Sun. • Astronomers theorize that the two moons of Mars, Phobos and Deimos, are captured asteroids.

32. Asteroid Strike • Scientists hypothesize that one or more large asteroids hit Earth 65 million years ago and caused extinction of the dinosaurs. • Scientists also hypothesize that the largest mass extinction, 250 million years ago, killing off 90% of all species was also caused by a large asteroid.

33. Meteoroids • Meteoroid-chunk of rock or dust in space. • Meteoroids come from comets or asteroids • Smaller than an asteroid.

34. Meteor • When a meteoroid enters Earth’s atmosphere, friction with the air creates heat and produces a streak of light that you can see in the sky. • A meteor is a meteoroid that enters Earth’s atmosphere and burns up.

35. Meteorites • Meteoroids that pass through the atmosphere and hit Earth’s surface are called meteorites. • Classified by composition: stony, iron ,or stony-iron.

36. What do we do if an NEO (Near-Earth-Object) is approaching? • Unknown… Still being experimented. • Scientist are calculating ways to use nuclear energy to divert an incoming object. • High energy x-ray pulses produce a shock wave to push the NEO in the opposite direction.

37. Review • Comet: A comet is a relatively small solar system body that orbits the Sun. When close enough to the Sun they display a visible coma (a fuzzy outline or atmosphere due to solar radiation) and sometimes a tail. • Asteroids:are small solar system bodies that orbit the Sun. Made of rock and metal, they can also contain organic compounds. Asteroids are similar to comets but do not have a visible coma (fuzzy outline and tail) like comets do. • Meteoroid: is a small rock or particle of debris in our solar system. They range in size from dust to around 10 meters in diameter (larger objects are usually referred to as asteroids). • Meteor: A meteoroid that burns up as it passes through the Earth’s atmosphere is known as a meteor. If you’ve ever looked up at the sky at night and seen a streak of light or ‘shooting star’ what you are actually seeing is a meteor. • Meteorite: A meteoroid that survives falling through the Earth’s atmosphere and colliding with the Earth’s surface is known as a meteorite.