Big Idea 5

Marc notices that when he looks at the stars at night, some appear to be brighter than others. Which three factors affect how bright a star appears to an observer on Earth?

• the star's color, size, and distance from Earth

• the star's energy, size, and temperature

• the star's size, temperature, and distance from Earth

• the star's movement, distance from Earth, and gravity

Which of the following is true of the Sun?

• The Sun is the closest star to Earth.

• The Sun is the largest star in the Milky Way.

• The Sun is the largest planet in our Solar System.

• The Sun is an example of a galaxy that gives off light energy.

Which of the following consists of gas, dust, and many stars?

• the Earth's atmosphere

• a galaxy

• a solar system

• the Sun

Brandon has learned that many stars are actually larger than the Sun. If this is true, why do these stars appear like points of light in the sky?

• These stars are hotter than the Sun.

• These stars have less mass than the Sun.

• These stars are farther away from Earth than the Sun is.

• These stars are made of different chemicals than the Sun.

Latoya is studying the stars and she learns that Barnard's star is the third closest star to Earth, although it cannot be seen without a telescope. She also knows that the brightest star in the night sky, Sirius, is much farther away but can be seen by the naked eye. Which of the following explains why Sirius can be seen without a telescope?

• Barnard's star is much larger and hotter than Sirius.

• Sirius is much larger and hotter than Barnard's star.

• All stars are the same size, so Sirius must be hotter than Barnard's star.

• All stars are the same temperature, so Sirius must be larger than Barnard's star.

There are lots of objects in our solar system, but only eight of them are planets. What do all planets have in common?

• They are all made of rock or ice.

• They all have rings or moons as satellites.

• They are all nearly round and orbit the Sun.

• They all rotate on an axis and orbit the Earth.

Which answer describes how the inner planets are similar to each other?

• They are all the same size.

• They all have solid surfaces.

• They all have at least one moon.

• They all have a thick atmosphere.

Which of the inner planets listed below is closest to the Sun?

• Earth

• Mars

• Mercury

• Venus

Tom and his friends were talking about what it would be like if they could go live on Mars someday. Mandy said it would be much colder there than on Earth and it would hardly ever get above freezing even in summer. Jose said there would be time periods on Mars like there are on Earth. What else might they experience if they ever went to live on Mars?

• A year on Mars would last almost as long as two Earth years.

• Water would run in the canals on Mars on the warmest days.

• They would see four big moons and several smaller ones at night on Mars.

• They could breathe the air since Mars and Earth have similar atmospheres.

When comets come close to the Sun they develop a tail that glows so we can see it from Earth. Asteroids do not develop tails like this. In what other way are asteroids different from comets?

• Asteroids orbit planets while comets orbit the Sun.

• Asteroids are rocky while comets are balls of ice and dust.

• Asteroids orbit outside of the Solar System while comets do not.

• Asteroids are smooth and round while comets are lumpy shapes.