Download Ch.1, Sec.3 - Mapping the Stars

Ch.1, Sec.3 - Mapping the Stars
 Patterns in the Sky
 constellation: a region of the sky that contains a
recognizable star pattern and that is used to describe the
location of objects in space
- every star or galaxy is located within 1 of 88 constellations
- as seasons change on Earth, the visibility of certain
constellations change too
- visible constellations are different in the Southern
Hemisphere as compared to the Northern Hemisphere
Ch.1, Sec.3 - Mapping the Stars
 Finding Stars in the Night Sky
- the use of an astrolabe helps
show the location of a star or
planet
- three points of reference
need to be used: zenith,
altitude, and horizon
Ch.1, Sec.3 - Mapping the Stars
 zenith: an imaginary point in
the sky directly above an
observer on Earth (the
zenith always has an altitude
of 90˚!)
 altitude: the angle between
the object and the horizon
 horizon: the line where the
sky and the Earth appear to
meet
Ch.1, Sec.3 - Mapping the Stars
- astronomers also use the celestial
sphere model to locate stars (see figure
5 on pg. 17)
- circumpolar stars are stars that can be
seen at all times of year and at all times
of night
- in the Northern Hemisphere,
______________
is the most famous
Polaris
circumpolar star
- in the Southern Hemisphere, Sigma
Octantis is the most famous circumpolar
star
Ch.1, Sec.3 - Mapping the Stars
 The Size and Scale of the Universe
- stars are much farther than
planets and we use the lightyear to measure their distance
from us
- one light-year represents the
distance light travels in 365
days (6 trillion miles @ 186,000
miles per second)
Proxima Centauri is the closest star to our
solar system at 4.2 light years away!
Epsilon Eridani b is the closest planet to
our solar system at 10 light years away!
Ch.1, Sec.3 - Mapping the Stars
- There are 100 billion galaxies in the observable Universe.
When you put those numbers together, you get an estimate
of 1024 stars in the entire Universe or a 1 followed by 24
zeroes (called one septillion)! That’s
1,000,000,000,000,000,000,000,000 stars or more than all
the combined grains of sand on planet Earth!!!!
Ch.1, Sec.3 - Mapping the Stars
- The Andromeda Galaxy is the closest spiral galaxy to the
Milky Way at just over 2.5 million light-years away.
Ch.1, Sec.3 - Mapping the Stars
 The Doppler Effect
- redshift occurs because objects moving faster away from
Earth emit a redder light
- blueshift occurs because
objects moving faster towards
Earth emit a bluer light
- everything is expanding in the Universe!!!
Ch.1, Sec.3 - Mapping the Stars
- evidence of redshift from the Hubble Ultra Deep Field image
Ch.1, Sec.3 - Mapping the Stars