Astronomy Test

Terrestrial Planets

Mercury, mars, venus, earth

Gaseous Planets

Jupiter, saturn, neptune, uranus

Characteristics of a terrestrial planet

• rocky surface

• smaller

• closely spaces

• closer to the sun

Characteristics of a gaseous planet

• Composed of gases (H,He)

• Larger

• Spaced further apart

• Further from the sun

Why is Pluto not considered a planet?

It does not meet planet criteria because it does not have a clear neighbourhood around it’s orbit of the sun

Luminous Objects

Celestial objects that make their own light and illuminate in space

Non-luminous objects

Celestial objects that don’t naturally make their own light but only reflect the light of the stars =

Dwarf Planet

a celestial object that: orbits a star, has enough mass to be round, and has not cleared its orbit of other objects

Asteroids

• rocky objects that orbit the sun, but are too small to be considered planets

• Located in asteroid belt

• Most are made of silicate (Stone) but they can be made of nickel or iron

Moons

• Natural satellites that revolve around planets

• Most moons have no atmosphere (airless) except for bigger moons (Jupiter’s Io, Saturns titan)

Kuiper Belt Objects

• a region of the solar system beyond the orbit of Neptune, believed to contain many comets, asteroids, and other small bodies made largely of ice.

Oort Cloud

• Contains billions of comets

• Defines the gravitational boundary of our solar system

Comets

• Icy objects that orbit the sun

• Start to melt in the inner solar system(Approaching the sun), creating two tails

• Dust tail(Yellow)

• Ion tail (Blue)

Short period comets

Originate in kuiper belt and orbit the sun in a few years

Long period comet

originate in oort cloud and take 1000s of years to orbit the sun

Meteoroid

rock that has travelled through space and gets trapped by the earth’s gravity and pulled into the atmosphere

Meteor

rock that falls towards the earth creating a bright streak of light as it comes through the atmosphere

Meteorite

Rock that hits the earth’s surface

Ice planets

Uranus, neptune

Which planet is furthest from the sun

Neptune

Which is the largest planet

Jupiter

Which planets are the coldest

Uranus and neptune

Which planet’s days are longer that a year?

Venus

What are the most common elements found in planetary atmospheres?

hydrogen, helium, nitrogen, oxygen, carbon dioxide, and argon

Solar Prominences

Streams of glowing gas that arch into space and return to the Sun

Solar Flares

Bursts of energy that flash off the sun’s surface

Sunspots

Areas of the sun’s surface that appear darker because they are a lower temperature than the surrounding area

Photosphere

Visible layer of the sun, cooler than other two layers

Chromosphere

Reddish colour, not visible to the naked eye, visible during solar eclipse.

Core

Hottest part of the solar system. Almost all the sun’s energy is produced here by fusion and moves outwards.

Corona

Outermost surface, only visible during a solar eclipse.

What are the colours for hot and cold in stars

Hot - blue

Cold - red

Apparent Magnitude

The brightness of a star seen from earth

Absolute magnitude

The brightness of a star that we observe if the stars were placed 32.6 light years from earth

What is a star?

Huge sphere of glowing gas

What is the chemical composition of most stars?

Helium and Hydrodgen

What is the approximate surface temperature?

6000 degrees celsius

How is it possible for white dwarf stars to have lower luminosity that the sun even though the sun is cooler than white dwarfs?

White dwarfs are a lot smaller than the sun, therefore they will give less light and have lower luminosity

How does the sun produce it’s energy?

Nuclear fusion of hydrogen to form helium

What type of celestial object does a low mass star evolve into?

White dwarf