The Starry Sky
Tuesday, March 5, 13
Ancient Constellations
Tuesday, March 5, 13
Ancient Constellations
‣
Why?
Tuesday, March 5, 13
Ancient Constellations
‣
‣
Why?
Ptolemy had 48, but left gaps
Tuesday, March 5, 13
Ancient Constellations
‣
‣
‣
Why?
Ptolemy had 48, but left gaps
Mostly bright stars
Tuesday, March 5, 13
Ancient Constellations
‣
‣
‣
‣
Why?
Ptolemy had 48, but left gaps
Mostly bright stars
Limited to Northern Hemisphere
Tuesday, March 5, 13
Ancient Constellations
‣
‣
‣
‣
Why?
Ptolemy had 48, but left gaps
Mostly bright stars
Limited to Northern Hemisphere
Tuesday, March 5, 13
Modern Constellations
Tuesday, March 5, 13
Modern Constellations
‣
Many added 16th thru 19th centuries
Tuesday, March 5, 13
Modern Constellations
‣
‣
Many added 16th thru 19th centuries
Modern names
Tuesday, March 5, 13
Modern Constellations
‣
‣
Many added 16th thru 19th centuries
Modern names
Tuesday, March 5, 13
Modern Constellations
‣
‣
‣
Many added 16th thru 19th centuries
Modern names
Fills in blanks (dim or Southern)
Tuesday, March 5, 13
Modern Constellations
‣
‣
‣
Many added 16th thru 19th centuries
Modern names
Fills in blanks (dim or Southern)
Tuesday, March 5, 13
Modern Constellations
‣
‣
‣
‣
Many added 16th thru 19th centuries
Modern names
Fills in blanks (dim or Southern)
1919 IAU forms
Tuesday, March 5, 13
Modern Constellations
‣
‣
‣
‣
‣
Many added 16th thru 19th centuries
Modern names
Fills in blanks (dim or Southern)
1919 IAU forms
1922 establish 88 official constellations
Tuesday, March 5, 13
Modern Constellations
‣
‣
‣
‣
‣
‣
Many added 16th thru 19th centuries
Modern names
Fills in blanks (dim or Southern)
1919 IAU forms
1922 establish 88 official constellations
1930 boundaries set for each
Tuesday, March 5, 13
Modern Constellations
‣
‣
‣
‣
‣
‣
Many added 16th thru 19th centuries
Modern names
Fills in blanks (dim or Southern)
1919 IAU forms
1922 establish 88 official constellations
1930 boundaries set for each
Tuesday, March 5, 13
Modern Constellations
‣
‣
‣
‣
‣
‣
Many added 16th thru 19th centuries
Modern names
Fills in blanks (dim or Southern)
1919 IAU forms
1922 establish 88 official constellations
1930 boundaries set for each
Tuesday, March 5, 13
Asterisms. Distance.
Tuesday, March 5, 13
Asterisms. Distance.
• Constellations vs. Asterisms
Tuesday, March 5, 13
Asterisms. Distance.
• Constellations vs. Asterisms
asterism is a figure made of a portion of a
‣ An
constellation
Tuesday, March 5, 13
Asterisms. Distance.
• Constellations vs. Asterisms
asterism is a figure made of a portion of a
‣ An
constellation
Tuesday, March 5, 13
Asterisms. Distance.
• Constellations vs. Asterisms
asterism is a figure made of a portion of a
‣ An
constellation
• Constellations and Distance
Tuesday, March 5, 13
Asterisms. Distance.
• Constellations vs. Asterisms
asterism is a figure made of a portion of a
‣ An
constellation
• Constellations and Distance
Stars
in
a
constellation
may
actually
be
very
‣ far apart. We cannot see the different
distances.
Tuesday, March 5, 13
Asterisms. Distance.
• Constellations vs. Asterisms
asterism is a figure made of a portion of a
‣ An
constellation
• Constellations and Distance
Stars
in
a
constellation
may
actually
be
very
‣ far apart. We cannot see the different
distances.
Tuesday, March 5, 13
Star Names
Tuesday, March 5, 13
Star Names
‣
Ancient Arabic Names
Tuesday, March 5, 13
Star Names
‣
‣
-
Ancient Arabic Names
Greek-Letter system:
Use order of Greek Alphabet to indicate
relative brightness within constellation.
Tuesday, March 5, 13
Star Names
‣
‣
-
Ancient Arabic Names
Greek-Letter system:
Use order of Greek Alphabet to indicate
relative brightness within constellation.
Tuesday, March 5, 13
Star Names
‣
‣
-
Ancient Arabic Names
Greek-Letter system:
Use order of Greek Alphabet to indicate
relative brightness within constellation.
Examples: (Official list at IAU)
★The brightest star in Lyra is Vega, also known as α Lyrae.
★Next is Sheliak. Written with abbreviation as β Lyr.
★The brightest star in Taurus is Aldebaran, also known as α Tauri.
★Next is Elnath. Written with abbreviation as β Tau.
Tuesday, March 5, 13
Brightnesses of Stars
Tuesday, March 5, 13
Brightnesses of Stars
• The ancient Greek astronomer Hipparchus
(we think) made a star catalog with numbers
to indicate the brightness of each star.
-
Tuesday, March 5, 13
1st magnitude=brightest
6th magnitude=dimmest
Brightnesses of Stars
• The ancient Greek astronomer Hipparchus
(we think) made a star catalog with numbers
to indicate the brightness of each star.
-
1st magnitude=brightest
6th magnitude=dimmest
• Now extended well beyond visible stars.
Tuesday, March 5, 13
Brightnesses of Stars
• The ancient Greek astronomer Hipparchus
(we think) made a star catalog with numbers
to indicate the brightness of each star.
-
1st magnitude=brightest
6th magnitude=dimmest
• Now extended well beyond visible stars.
Tuesday, March 5, 13
Brightnesses of Stars
• The ancient Greek astronomer Hipparchus
(we think) made a star catalog with numbers
to indicate the brightness of each star.
-
1st magnitude=brightest
6th magnitude=dimmest
• Now extended well beyond visible stars.
• Notice two unusual features:
- The magnitude scale is reverse
- The magnitude scale logarithmic
Tuesday, March 5, 13
Time and Place
Tuesday, March 5, 13
Time and Place
• All celestial bodies appear to make a full
circle around the earth each day.
Tuesday, March 5, 13
Time and Place
• All celestial bodies appear to make a full
circle around the earth each day.
• This is really a result of the Earth spinning
once per day.
Tuesday, March 5, 13
Time and Place
• All celestial bodies appear to make a full
circle around the earth each day.
• This is really a result of the Earth spinning
once per day.
• The basic times of day—sunrise, noon,
sunset, and midnight—are really places.
Tuesday, March 5, 13
Time and Place
• All celestial bodies appear to make a full
circle around the earth each day.
• This is really a result of the Earth spinning
once per day.
• The basic times of day—sunrise, noon,
sunset, and midnight—are really places.
Tuesday, March 5, 13
Celestial Poles & Equator
Tuesday, March 5, 13
Celestial Poles & Equator
• The Earth’s north and south poles point to fixed spots
in the sky, even as the Earth turns.
Tuesday, March 5, 13
Celestial Poles & Equator
• The Earth’s north and south poles point to fixed spots
in the sky, even as the Earth turns.
• The Earth’s equator points to a fixed circle in the sky,
even as the Earth turns.
Tuesday, March 5, 13
Celestial Poles & Equator
• The Earth’s north and south poles point to fixed spots
in the sky, even as the Earth turns.
• The Earth’s equator points to a fixed circle in the sky,
even as the Earth turns.
• The North and South Celestial Poles and the Celestial
Equator are extensions of the Earth’s poles and
equator.
Tuesday, March 5, 13
Celestial Poles & Equator
• The Earth’s north and south poles point to fixed spots
in the sky, even as the Earth turns.
• The Earth’s equator points to a fixed circle in the sky,
even as the Earth turns.
• The North and South Celestial Poles and the Celestial
Equator are extensions of the Earth’s poles and
equator.
Tuesday, March 5, 13