Planets and Dwarf Planets

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Questions and Answers

According to the International Astronomical Union, what is a key criterion for a celestial body to be classified as a planet?

  • It must have a complex atmospheric composition.
  • It must have cleared the area of its orbit of smaller objects. (correct)
  • It must be composed primarily of rock and metal.
  • It must be located within the asteroid belt.

What distinguishes a dwarf planet from a planet, according to the International Astronomical Union?

  • Dwarf planets have not cleared the area around their orbit of smaller objects. (correct)
  • Dwarf planets do not orbit a star.
  • Dwarf planets are not massive enough to be nearly spherical.
  • Dwarf planets have cleared the area around their orbit of smaller objects.

What is the significance of an astronomical unit (AU) in the context of our solar system?

  • It is used to measure the mass of celestial objects.
  • It standardizes measurements to the distance between Earth and the Sun. (correct)
  • It defines the boundary of the solar system.
  • It represents the distance light travels in one year.

How does the distance of a planet from the Sun generally affect its orbital period?

<p>Planets closer to the Sun have shorter orbital periods. (A)</p> Signup and view all the answers

Approximately how much more massive is the Sun compared to the combined mass of all other objects in the solar system?

<p>500 times more massive (C)</p> Signup and view all the answers

Which of the following sequences correctly lists the planets and Ceres in order of increasing distance from the Sun?

<p>Mercury, Venus, Earth, Mars, Ceres, Jupiter, Saturn, Uranus, Neptune (B)</p> Signup and view all the answers

What are the two primary regions that broadly categorize the layout of our solar system?

<p>The inner planets and the outer planets (A)</p> Signup and view all the answers

Which of these correctly lists all the inner planets of our solar system?

<p>Mercury, Venus, Earth, Mars (A)</p> Signup and view all the answers

Which of the following planets are classified as outer planets?

<p>Jupiter, Saturn, Uranus, Neptune (B)</p> Signup and view all the answers

How does Pluto's orbit differ from the orbits of the eight recognized planets in our solar system?

<p>Pluto's orbit is tilted and elliptical, sometimes passing inside Neptune's orbit. (C)</p> Signup and view all the answers

What is the Kuiper Belt primarily known for?

<p>Being a region where most comets in our solar system originate (B)</p> Signup and view all the answers

What is characteristic of the objects residing in the scattered disk region of the solar system?

<p>Objects with highly elliptical and inclined orbits (D)</p> Signup and view all the answers

What is the primary function of the heliosphere?

<p>To serve as a boundary between the solar and interstellar winds (A)</p> Signup and view all the answers

What did the ancient astronomers originally mean when they used the term 'planet'?

<p>Wandering stars (A)</p> Signup and view all the answers

Which technology was first employed to observe the moons of Jupiter, and who was the scientist who made these observations?

<p>Telescope, Galileo (B)</p> Signup and view all the answers

Approximately when did our solar system form?

<p>4.6 billion years ago (C)</p> Signup and view all the answers

What was the primary composition of the nebula that eventually formed our solar system?

<p>Hydrogen and helium (B)</p> Signup and view all the answers

What fundamental process defines our Sun as a star?

<p>It emits more energy than it absorbs. (A)</p> Signup and view all the answers

What is the key difference between a planet and a moon?

<p>A planet orbits a star, while a moon orbits a planet. (A)</p> Signup and view all the answers

What is the fundamental force that causes planets to orbit stars?

<p>Gravity (C)</p> Signup and view all the answers

Flashcards

Requirements to be a planet?

To be a planet, it must orbit a star, be big enough to be a sphere due to its own gravity, be small enough that it isn't a star, and have cleared its orbit of smaller objects.

Requirements to be a dwarf planet?

To be a dwarf planet, it must orbit a star, have enough mass to be nearly spherical, not have cleared the area around its orbit, and not be a moon.

What is an astronomical unit?

It is the average distance from the Earth to the Sun ( 150 MKm)

Distance vs. Orbital Periods?

Planets closer to the sun have shorter orbital periods.

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Mass of our sun compared to the solar system?

The Sun's mass is 500 times more massive than everything else in the solar system combined.

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Order of planets and dwarf planets?

Mercury, Venus, Earth, Mars, Ceres, Jupiter, Saturn, Uranus, Neptune, Pluto, Haumea, Makemake, Eris.

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Two main regions of the solar system?

The inner and outer planets

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List the inner planets.

Mercury, Venus, Earth, Mars

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List the outer planets

Jupiter, Saturn, Uranus, Neptune

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Pluto's orbital plane different?

Pluto's orbit is tilted relative to the other planets and is shaped like a long, narrow ellipse. Because of this, Pluto's orbit sometimes even passes inside Neptune's orbit.

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What is the Kuiper Belt?

The region beyond Neptune where Pluto and many more objects (asteroids) revolve around the Sun. It is the region that is home to most of our solar system's comets.

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What is happening in the scattered disk?

The region is filled with strangely orbiting objects and minor planets.

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What is the heliosphere?

It's the magnetic bubble which forms the very outer edge of our solar system. It's also the boundary between the solar and interstellar winds.

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What did "planet" mean to ancient astronomers?

wandering stars

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Technology to observe Jupiter's moons?

telescope

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When did our Solar system form?

4.6 B.Y.A

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Main composition of solar nebula?

H and He

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Why is our sun a star?

" ...it emits more energy than it absorbs."

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Difference between a planet and a moon?

A planet revolves around a star.

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Why do planets orbit stars?

Gravity!!

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Study Notes

  • Requires a link to external reference material

Requirements to be a planet, according to the International Astronomical Union (IAU):

  • Orbit a star
  • Possess enough gravity to be shaped as a sphere
  • Not be a star itself
  • Have cleared its orbital area of smaller objects

Requirements to be a dwarf planet, according to the IAU:

  • Orbit a star
  • Have enough mass to be nearly spherical
  • Not have cleared the area around its orbit of smaller objects
  • Not be a moon

Astronomical Unit

  • Average distance from Earth to the Sun: 150 MKm

Distance of Planets from the Sun and Orbital Periods

  • The closer to the sun, the shorter the orbital period

Mass of the Sun Compared to the Solar System

  • The sun's mass is 500 times more massive than the combined mass of everything else in the solar system

Order of the Planets and Dwarf Planets by Distance from the Sun:

  • Mercury, Venus, Earth, Mars, Ceres (in the asteroid belt), Jupiter, Saturn, Uranus, Neptune, Pluto, Haumea, Makemake, Eris

Two Main Regions of the Solar System:

  • inner planets
  • outer planets

Inner Planets

  • Mercury
  • Venus
  • Earth
  • Mars

Outer Planets

  • Jupiter
  • Saturn
  • Uranus
  • Neptune

Pluto's Orbit

  • Tilted in relation to the other planets
  • Shaped like a long, narrow ellipse
  • It sometimes passes inside Neptune’s orbit

Kuiper Belt

  • Region beyond Neptune where Pluto and many other asteroid-like objects revolve around the Sun
  • Most of solar systems comets are in the Kuiper Belt

Scattered Disk

  • Region filled with strangely orbiting objects and minor planets

Heliosphere

  • Magnetic bubble forming the outer edge of the solar system
  • Boundary between the solar and interstellar winds

Ancient Astronomers Definition of a Planet

  • Wandering stars

First Technology Used to Observe Jupiter's Moons

  • Telescope, by Galileo.

Solar System Formation

  • 4.6 B.Y.A

Main Composition of Nebula Forming the Solar System

  • H and He

Why Our Sun Is A Star

  • It emits more energy than it absorbs

Difference Between Planets and Moons

  • A planet revolves around a star
  • A moon revolves around a planet

Why Planets Orbit Stars

  • Gravity

Possible Existence of a Ninth Planet

  • Explained by distant dwarf planets beyond Pluto moving on large elliptical orbits
  • Its orbits are caused by a gravitational pull of an object large enough to distort the orbit

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