Night Sky Watching
(Basics)
Stars Pivot around a Point
The North Celestial Pole
(NCP)
 Special
spot on the sky that the Earth’s
rotation axis points to
 Why special?
During the night the stars
appear to rotate around
this spot
 Also
special (and useful) in other ways …
Watching Stars from the North
Pole
Constellations are Big
Big Dipper: Points to Polaris
 http://www.astropix.com/HTML/C_S
PRING/URSAS.HTM
Finding Polaris
Lucky Breaks!
 The
star Polaris is amazing close to
NCP (now)
 The “pointer stars” in the Big Dipper
line up directly with Polaris!!!!
 Big Dipper is circumpolar
constellation
–See it all night and all year
 Polaris also called Pole Star, North
Star
Big Dipper
Why care about finding Polaris?
 The
direction of Polaris is due North
 The angle between Polaris and the
horizon is
 How
YOUR LATITUDE
can I measure angles?
Big Dipper as Star Guide
Constellations
Astronomy Picture of the Day (APOD)
http://antwrp.gsfc.nasa.gov/apod/ap090627.htm
l
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Summer Triangle
http://antwrp.gsfc.nasa.gov/apod/ap090912.html
Winter Hexagon
http://antwrp.gsfc.nasa.gov/apod/ap021106.html
Summer Triangle
Winter
Hexagon
Constellation Facts
 Group
of stars all in roughly the same
direction from Earth, BUT …. Each has
its own different distance from the
Earth
– Therefore, NOT grouped together is space
 From
Greek astronomers have
inherited the names of the
constellations: mythological figures or
animals
 Different cultures on Earth each have
different names for the constellations
Constellation
Stars at
Different
Distances
from Earth
Visible Constellations change over a
year
 May
have heard …
– “Orion is a winter constellation”
– “You can see Cygnus most of the summer”
 Above
comments arise because you
cannot see the Constellations near
where the Sun is in the sky
– Sun so bright it washes out rest of stars
 Since
Sun moves along the Ecliptic
over a year the constellations “away”
from the Sun change over a year.
Constellations on
opposite side of
Sun (Opposition)
The Zodiac
 Band
of constellations closest to the
Ecliptic (Sun’s yearly path across the
sky)
 Correspond to Horoscope “Signs”
–Astrology used to make predictions (not
science!)
 Useful
for backyard astronomy:
Planets and the Moon can always be
found in the Zodiac
 Width of the Zodiac belt ~ 18°
Mars
Saturn
Mercury
Naming Stars
Brightest star in
constellation Taurus
Greek name: α Taurus
Arabic name:
Aldebaran
“Al Debarren”
“The Follower”
(of the Pleiades)