Transcript Document
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!