Transcript Astronomy_Chapter_1

Astronomy Chapter 1
Charting the Universe
Obj.#1
What is Astronomy?
• Astronomy is the study of the Universe
• The universe is the total of all space, time,
matter, and energy
• The universe is made up of galaxies
Our Galaxy …The Milky Way
Galaxy NGC 300
• Light year- distance traveled by liht in one
year
• Light years are used to measure the
universe
• The speed of light is 186,000 per second
Obj. #2 What is a constellation?
• Humans made patterns of stars that they
saw in the sky
• These patterns are by chance.
• Humans can see around 6,000 stars with
the naked eye
The Big Dipper
Obj. 3 Describe the Celestial
Sphere
• The celestial sphere is an imaginary
sphere that surrounds Earth. The stars
and planets appear to be attached to the
sphere
• It is used to help locate stars and planets
Important parts of the celestial
sphere
• North Celestial pole- directly over the north
pole
• South Celestial pole- directly over the
south pole
• Celestial equator- circle half way between
the North and South Celestial Sphere
Celestial Sphere
• Declination- angular degrees above and
below the equator- ( similar to latitude line
on an Earth globe)
• Vernal Equinox is the 0 point on the
celestial equator line
• Right Ascension- measured in hours and
measures distances eastward of the
Vernal Equinox
Declination lines
Lines of Ascension
• Zenith- Where ever you are located…the
point directly over your head on the
celestial sphere
Zenith
Obj. 4: Distinguish between a
Solar Day and a Sidereal Day
• Solar Day- basic time unit of 24 hours
that it takes the Earth to rotate on its axis
• Sidereal Day- a day measured with
respect to the stars. It is 23 hours and 56
minutes
Solar and Sidereal Day
Obj. #5: Explain what causes
seasonal changes
• Elliptic Plane is the Earth’s orbit around
the Sun
• Summer Solstice- the point where the
Earth’s North pole is pointed at the Sun
• Occurs on June 21…longest day of the
year
• Winter Solstice- shortest day of the year
• South pole faces the Sun
• Equinoxes- when the light during the day
and night are equal
Reason for the Seasons
• The Earth is tilted at 23.5 degrees all year
long.
• Sunlight strikes the Earth’s surface at
different angles during the year
causing the changes in the season.
• We are not closer to the sun in the
summer!!!
Reason for the Seasons
Obj. 6: Describe precession
Precession is the change of the Earth’s
cycle over time. One complete cycle takes
26,000 years to complete
Objective 7: Explain the Phases of
the Moon
• The Sun always lights half of the moon.
• What part of that light we see from Earth
depends on where the Moon is located as
it travels around Earth.
Phases of the Moon
1. New Moon- the near side of the moon
faces away from the sun making
observers on Earth see the dark side.
2. Waxing Crescent- this means that the
right side is brighter and appears to be
making a crescent.
New Moon
Waxing Crescent
3. Quarter Moon- at this stage one would
be one-half of the moon. Light is on the
right.
4. Waxing Gibbous Moon- when the quarter
moon begins to grow…almost full
5. Full moon-occurs two weeks after new
moon.
Quarter Moon
Waxing Gibbous
Full Moon
6. Waning Gibbous- when the light begins
to shrink.
7. Third quarter moon- moon with ½ light on
the left side
8. Waning Crecent- has a crescent on the
left side.
Waning Gibbous Moon
3rd Quarter Moon
Phases of the Moon
Obj. # 8 Describe a lunar and solar
eclipse
• Lunar eclipse-occurs when the Earth is
directly between the Sun and Moon.
Earth’s shadow falls on the moon.
• Solar eclipse- occurs when the moon is
directly between the Sun and the Earth.
The Moon blocks sunlight from hitting
Earth.
Lunar Eclipse
Solar Eclipse