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Welcome to
Starry Monday at Otterbein
Astronomy Lecture Series
-every first Monday of the monthOctober 6, 2008
Dr. Uwe Trittmann
Today’s Topics
• Practical Astronomy –Star maps and
such
• The Night Sky in October
Feedback!
• Please write down suggestions/your interests on the
note pads provided
• If you would like to hear from us, please leave your
email / address
• To learn more about astronomy and physics at
Otterbein, please visit
– http://www.otterbein.edu/dept/PHYS/weitkamp.asp (Obs.)
– http://www.otterbein.edu/dept/PHYS/ (Physics Dept.)
What’s up in the night sky?
The Celestial Sphere
• An imaginary sphere
surrounding the earth,
on which we picture the
stars attached
• Axis through earth’s
north and south pole
goes through celestial
north and south pole
• Earth’s equator
Celestial equator
What’s up for you?
Observer
Coordinates
• Horizon – the
plane you stand on
• Zenith – the point
right above you
• Meridian – the
line from North to
Zenith to south
…depends where you are!
• Your local sky –
your view depends on your location on earth
Look
North in
Westerville
Look
North on
Hawai’i
SkyGazer
• A computer program that simulates the
vision of the sky during day and night
Things to observe:
• Position on Earth: observe how the view of sky
changes as you move E,W, N,S
• Note the distribution of sunlight on Earth!
• Rotation is around Polaris which is not in zenith
Star Maps
• … are a 2D rendering of a 3D situation
 They can’t be perfect!
• You are looking at the inside of a sphere
East and West are reversed
On the Web
• http://www.stargazing.net/David/constel/sky
maps/novlines.html
• http://www.google.com/sky/
• http://www.kidscosmos.org/kid-stuff/starmaps.html
Star
Maps
Celestial
North Pole –
everything
turns around
this point
Zenith – the
point right
above you &
the middle of
the map
40º
90º
Daily Rising and Setting
• Due to the rotation of the
Earth around its axis
• Period of rotation:
1 siderial day= 23h56m4.1s
• 1 solar day (Noon to Noon) =24h
• Stars rotate around the
North Star – Polaris
That’s
what
you’d
actually
see!
Confusing?
Experts’
view
Learn to
identify crucial
constellations
Find your way
around the
night sky
Hands On!
• Dial in the night sky as we will see it NOW!
• Advance time
• Advance date
How bright are Stars? -The Magnitude Scale
• The magnitude is a measure of
the apparent brightness
• Logarithmic scale
• Notation: 1m.4 (smaller brighter)
• Originally six groupings
– 1st magnitude the brightest
– 6th magnitude the dimmest
• The absolute magnitude is the
apparent magnitude a star would
have at a distance of 33 ly: 2M.8
When can I see a star/constellation?
• When the Sun is not in the constellation!
– As Earth moves around the Sun, the Sun seems
to move around the ecliptic: from Aries to
Taurus, Gemini, etc.
• As the Earth rotates, stars rise in the East
– Wait a while and “your” star will rise
– Bummer: if you have to wait too long, the Sun
will rise, too, and outshine your star.
Sun’s Apparent Path
As Earth moves around the Sun, the Sun
appears “in front” of the constellations of the
ecliptic (Zodiac)
3D view
Vernal equinox:
Ecliptic
intersects with
celestial equator
When can I see the Moon?
• Depends on its position relative to Sun, i.e.
its phase
• New Moon: same as Sun
• Full Moon: opposite of Sun
When can I see the Planets?
• The move slowly around the ecliptic
• Look up in which constellation they appear
• Identify them as “the extra star”
Motion of Sun, Moon and other Planets
•
•
All major bodies in the Solar System move around ecliptic
Slow drift (from W to E) against the background of stars
Night Sky of the Season
• As a crude way of finding visible
constellations, one divides them into
Summer, Autumn, Winter and Spring
constellations
• Some constellations are ALWAYS visible –
the circumpolar ones that are close enough
to the celestial pole
The Night Sky in October
• The sun is past autumn equinox -> longer nights!
• Autumn constellations are coming up: Cassiopeia,
Pegasus, Perseus, Andromeda, Pisces
 lots of open star clusters!
• Jupiter is visible all night
Moon Phases
• Today (Waning Gibbous, 70%)
• 10 / 7 (First Quarter Moon)
• 10/ 14 (Full Moon)
• 10 / 21 (Last Quarter Moon)
• 10 / 28 (New Moon)
Today
at
Noon
Sun at
meridian,
i.e.
exactly
south
10 PM
Typical
observing
hour,
early
October
Uranus
Neptune
Moon
Jupiter
SouthWest
High in the
sky:
The summer
triangle
Due
North
Big Dipper
points to the
north pole
High up – the
Autumn
Constellations
• W of
Cassiopeia
• Big Square
of Pegasus
• Andromeda
Galaxy
Andromeda
Galaxy
• “PR” Foto
• Actual look
East
Perseus and
Auriga
with Plejades
and the
Double
Cluster
Greek
Mythology in
the Sky
South 2006
• Planets
– Uranus
– Neptune
• Zodiac:
– Capricorn
– Aquarius
South –
2007
• Planets
– Uranus
– Neptune
• Zodiac:
– Capricorn
– Aquarius
South –
2008
• Planets
– Uranus
– Neptune
• Zodiac:
– Capricorn
– Aquarius
Mark your Calendars!
• Next Starry Monday: November 3, 2008, 7 pm
(this is a Monday
• Observing at Prairie Oaks Metro Park:
– Friday, October 3, 7:45 pm
– Friday, January 30, 7:00 pm
• Web pages:
– http://www.otterbein.edu/dept/PHYS/weitkamp.asp (Obs.)
– http://www.otterbein.edu/dept/PHYS/ (Physics Dept.)
)
Mark your Calendars II
•
•
•
•
Physics Coffee is every Wednesday, 3:30 pm
Open to the public, everyone welcome!
Location: across the hall, Science 256
Free coffee, cookies, etc.
Solar vs Siderial Day
• Earth rotates in 23h56m
• also rotates around sun
 needs 4 min. to “catch up”
• Consequence: stars rise 4
minutes earlier each night
• after 1/2 year completely
different sky at night!