Night Sky Watching Night Sky Watching (Basics)(Basics)

Stars Pivot around a PointStars Pivot around a Point

The North Celestial Pole The North Celestial Pole (NCP)(NCP)

Special spot on the sky that the Earth’s Special spot on the sky that the Earth’s rotation axis points to rotation axis points to

Why special?Why special?

During the night the stars During the night the stars appear to rotate around appear to rotate around this spotthis spot

Also special (and useful) in other ways …Also special (and useful) in other ways …

Watching Stars from the North Watching Stars from the North PolePole

Constellations are BigConstellations are Big

Big Dipper: Points to PolarisBig Dipper: Points to Polaris

http://www.astropix.com/HTML/C_SPRhttp://www.astropix.com/HTML/C_SPRING/URSAS.HTMING/URSAS.HTM

Finding PolarisFinding Polaris

Lucky Breaks!Lucky Breaks!

The star Polaris is amazing close to NCP The star Polaris is amazing close to NCP (now)(now)

The “pointer stars” in the Big Dipper line The “pointer stars” in the Big Dipper line up directly with Polaris!!!!up directly with Polaris!!!!

Big Dipper is circumpolar constellationBig Dipper is circumpolar constellation– See it all night and all yearSee it all night and all year

Polaris also called Pole Star, North StarPolaris also called Pole Star, North Star

Big DipperBig Dipper

Why care about finding Polaris?Why care about finding Polaris?

The direction of Polaris is due NorthThe direction of Polaris is due North The angle between Polaris and the The angle between Polaris and the

horizon is horizon is YOUR LATITUDEYOUR LATITUDE How can I measure angles?How can I measure angles?

Big Dipper as Star GuideBig Dipper as Star Guide

ConstellationsConstellations

Astronomy Picture of the Day (APOD)Astronomy Picture of the Day (APOD)

http://antwrp.gsfc.nasa.gov/apod/ap090627.htmlhttp://antwrp.gsfc.nasa.gov/apod/ap090627.html

Summer TriangleSummer Triangle http://antwrp.gsfc.nasa.gov/apod/ap090912.htmlhttp://antwrp.gsfc.nasa.gov/apod/ap090912.html

Winter HexagonWinter Hexagon http://antwrp.gsfc.nasa.gov/apod/ap021106.htmlhttp://antwrp.gsfc.nasa.gov/apod/ap021106.html

Summer TriangleSummer Triangle

Winter Winter HexagonHexagon

Constellation FactsConstellation Facts Group of stars all in roughly the same Group of stars all in roughly the same

direction from Earth, BUT …. Each has direction from Earth, BUT …. Each has its own different distance from the its own different distance from the EarthEarth– Therefore, NOT grouped together is spaceTherefore, NOT grouped together is space

From Greek astronomers have From Greek astronomers have inherited the names of the inherited the names of the constellations: mythological figures or constellations: mythological figures or animalsanimals

Different cultures on Earth each have Different cultures on Earth each have different names for the constellationsdifferent names for the constellations

Constellation Constellation Stars at Stars at DifferentDifferent Distances Distances from Earthfrom Earth

Visible Constellations change over a Visible Constellations change over a yearyear

May have heard …May have heard …– ““Orion is a winter constellation”Orion is a winter constellation”– ““You can see Cygnus most of the summer”You can see Cygnus most of the summer”

Above comments arise because you Above comments arise because you cannot see the Constellations near cannot see the Constellations near where the Sun is in the skywhere the Sun is in the sky– Sun so bright it washes out rest of starsSun so bright it washes out rest of stars

Since Sun moves along the Ecliptic Since Sun moves along the Ecliptic over a year the constellations “away” over a year the constellations “away” from the Sun change over a year.from the Sun change over a year.

Constellations on Constellations on opposite side of opposite side of Sun (Opposition)Sun (Opposition)

The ZodiacThe ZodiacBand of constellations closest to the Ecliptic Band of constellations closest to the Ecliptic

(Sun’s yearly path across the sky)(Sun’s yearly path across the sky)Correspond to Horoscope “Signs”Correspond to Horoscope “Signs”

– Astrology used to make predictions (not Astrology used to make predictions (not science!)science!)

Useful for backyard astronomy: Planets and Useful for backyard astronomy: Planets and the Moon can the Moon can alwaysalways be found in the Zodiac be found in the Zodiac

Width of the Zodiac belt ~ 18Width of the Zodiac belt ~ 18°°

Mercury

MarsSaturn

Naming StarsNaming Stars

Brightest star in Brightest star in constellation Taurusconstellation Taurus

Greek name: Greek name: αα Taurus TaurusArabic name: Arabic name:

AldebaranAldebaran““Al Debarren”Al Debarren”““The Follower”The Follower”(of the Pleiades)(of the Pleiades)