Starry Monday at Otterbein Welcome to Starry Monday at Otterbein Astronomy Lecture Series -every first Monday of the month- October 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 Relative positions of stars do not change -> attached to sphere In ancient times was often literally thought of as a physical sphere rotating about the earth

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/skymaps/novlines.html http://www.google.com/sky/ http://www.kidscosmos.org/kid-stuff/star-maps.html

Star Maps 40º 90º Celestial North Pole – everything turns around this point Zenith – the point right above you & the middle of the map

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 Circumpolar – never rise or set

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 Note higher magnitude means a dimmer star! Abs magnitude is effectively the luminosity; apparent magnitude involves the luminosity and distance It is a property of the eye that a fixed difference in perceived brightness corresponds to a multiplicative factor in energy: thus if one star is one order of magnitude brighter than another, it gives off about 2.5 times as much light; 2 orders of magnitude, 2.5H2.5=6.25 times as much light; etc. 5 orders of magnitude=100 times.

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 Slow drift across background of fixed stars caused by rotation of earth about sun Period = 1 year (365 ¼ days) 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 Skyglobe demo 7 visible “planets” incl. the sun and moon Planet = “wanderer” Days of the week named after the planets

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 Moon Jupiter Uranus Neptune Moon Jupiter

South-West 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

with Plejades and the Double Cluster East Perseus and Auriga with Plejades and the Double Cluster

Greek Mytho- logy 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!