How could you describe to someone where a location is on Earth? Bellwork 9/19 How could you describe to someone where a location is on Earth?

Coming Up Today: Begin Constellations and Positions, Finish modeling lab if needed Friday 9/21: Finish Planisphere practice, Celestial Sphere computer simulation Tuesday 9/25: Stellar Parallax notes & activity Thursday 9/27: Review Tuesday10/2: Begin Unit 2 Thursday 10/4: Unit 1 Test

A few things… Content Rubric Lab Rubric Scientific Reasoning Rubric Be prepared for a Lunar Phase/Eclipse lab question on your test!!!

Earth-Moon system Moon Phases The relative positions of the Sun, Earth, and Moon constantly change Lunar phases are a consequence of the motion of the Moon and the sunlight that is reflected from its surface It’s because of our perspective from Earth…what we can see at any given time… This is NOT Earth’s shadow!

Lunar motions Moon's period of rotation about its axis and its revolution around Earth are the same Causes the same lunar hemisphere to always face Earth Synodic month Cycle of the moon phases Takes 29 1/2 days

“To obscure light from” Eclipses “To obscure light from” Solar eclipse Moon moves in a line directly between Earth and the Sun Can only occur during the new-Moon phase Lunar eclipse Moon moves within the shadow of Earth Only occurs during the full-Moon phase **For any eclipse to take place, the Moon must be in the plane of the ecliptic at the time of new- or full-Moon **

Solar eclipse

Lunar eclipse

Moon Motions The Moon DOES rotate on its axis The Moon revolves at the same rate it rotates The Moon takes about 28 days to revolve around Earth…not 24 hours... The Moon rises & sets, just like the Sun and constellations

Understanding the Celestial Sphere

How could you describe to someone where a location is on Earth?

Pareidolia--the tendency to perceive a specific, often meaningful, image in a random or ambiguous visual pattern

People of the past used this phenomenon to designate locations & positions in the night sky. Why would they care to do that?

Constellations A recognizable pattern of stars in the sky Used to separate & locate regions of the sky 88 constellations They were not all designated at one time

Constellations Bayer System System of labeling stars First for Brightness Using Greek alphabet α Brightest β 2nd Brightest And so on

Celestial Sphere Stars appeared to move around a fixed point and rotate around Earth We now know that these “star trails” are due to the Earth’s rotation…not the stars’.

Celestial Meridian: Divides the sky in half from north to south. Zenith: Bisects the meridian This point never changes on the celestial sphere, but from the observers’ point of view, the stars at the zenith change “Actual” zenith vs. “local” zenith How do we tell “what’s what”?

Locating Objects in the Sky: There are 2 ways to look at it… 1. Equatorial system of location Two location components Declination – the angular distance north or south of the celestial equator Measured in degrees  Right ascension – the angular distance measured eastward along the celestial equator from the position of the vernal equinox Measured in hours & minutes 

Right Ascension (or "RA") and Declination (or "Dec") are global coordinates any particular star has the same RA and Dec for all observers on Earth, and that position remains the same, night after night.

Locating objects in the night sky: Local Coordinates 2. Altitude and Azimuth local coordinates each observer sets up his own reference frame Altitude and Azimuth of a given star will change over just a few minutes as the star appears to move across the sky

Ecliptic Zodiac The apparent path of the sun through the stars The broad belt of constellations that lie along the ecliptic 12 total constellations

Anatomy of a Planisphere: Inner ring: time of day Declination: Degrees in “viewing window” Middle ring: Months & Days Outer ring: Right ascension (hours & minutes)

How to use a Planisphere IF NEEDED, set the planisphere to the correct day and time Make sure you’re holding the planisphere in the correct orientation  “East horizon” on the right, “West horizon” on the left Find the Declination Find the Right Ascension (a straight edge can be helpful with this)

What the heck am I looking at?!? Horizon (looking South) Horizon (looking North) Directly overhead…or the Zenith

Planisphere Practice: What is the RA & Dec. of Arcturus? (near constellation Bootes) RA: ~14hr 15min Dec: ~+20⁰

Planisphere Practice: What is the RA & Dec. of Betelgeuse? (in constellation Orion) RA: ~6hrs Dec: ~+8⁰

Planisphere Practice: Set your planisphere to September 16th at 10:00pm. Name a constellation that is RISING (on the East Horizon). Taurus Perseus Aries Ect…

Planisphere Practice: Set your planisphere to January 12th at 6:00pm. Name a constellation that is SETTING (on the West Horizon). Sagitta Cygnus Capricornus Ect…

Planisphere Practice: Set your planisphere to February 28th at 8:00pm. Name a constellation that is close to its ZENITH.  Zenith = bisecting line of the meridian… SO divide your “window” in half horizontally and choose a constellation at that bisecting line Gemini, Auriga, Camelopardalis

Bellwork 9/22 What unit is Declination measured in? What unit is Right Ascension measured in? What is the purpose of measuring Declination & Right Ascension?

Reminder: Today: Finish up constellations & positions Tuesday 9/26: Stellar Parallax & Review Thursday 9/28: Unit 1 Test

Bellwork 9/21 How do astronomers communicate the location of objects in the celestial sphere? …There is more than one answer here!

Coming Up—B Day Today: Begin Constellations and Positions, Finish modeling lab if needed Friday 9/21: Finish Planisphere practice, Celestial Sphere computer simulation Tuesday 9/25: Stellar Parallax notes & activity Thursday 9/27: Review Tuesday10/2: Begin Unit 2 Thursday 10/4: Unit 1 Test

Coming Up—A Day Today 9/20: Finish Planisphere practice, Celestial Sphere computer simulation Monday 9/24: Stellar Parallax notes & activity Wednesday 9/26: Review Monday 10/1: Begin Unit 2 Wednesday 10/3: Unit 1 Test

Anatomy of a Planisphere: Inner ring: time of day Declination: Degrees in “viewing window” Middle ring: Months & Days Outer ring: Right ascension (hours & minutes)

What the heck am I looking at?!? Horizon (looking South) Horizon (looking North) Directly overhead…or the Zenith

Planisphere Practice: What is the RA & Dec. of Pollux? (within the constellation GEMINI) RA: ~7hr 45min Dec: ~+28⁰

Planisphere Practice: What is the RA & Dec. of Sirius? (within the constellation CANIS MAJOR) RA: ~6hr 45min Dec: ~-17⁰

Planisphere Practice: What is the RA & Dec. of Vega? (within the constellation LYRA) RA: ~6hr 45min Dec: ~-17⁰

Planisphere Practice: Set your planisphere to October 15th at midnight. Name a constellation that is close to its ZENITH.  Zenith = bisecting line of the meridian… SO divide your “window” in half horizontally and choose a constellation at that bisecting line Cassiopeia, Perseus

Planisphere Practice: Set your planisphere to March 20th at midnight. Name a constellation that is close to its ZENITH.  Zenith = bisecting line of the meridian… SO divide your “window” in half horizontally and choose a constellation at that bisecting line Ursa major

Planisphere Practice: Set your planisphere to February 28th at 8:00pm. Name a constellation that is close to its ZENITH.  Zenith = bisecting line of the meridian… SO divide your “window” in half horizontally and choose a constellation at that bisecting line Gemini, Auriga, Camelopardalis

Planisphere Practice: Set your planisphere to September 16th at 10:00pm. Name a constellation that is RISING (on the East Horizon). Taurus Perseus Aries Ect…

Planisphere Practice: Set your planisphere to January 12th at 6:00pm. Name a constellation that is SETTING (on the West Horizon). Sagitta Cygnus Capricornus Ect…

Planisphere Practice: Set your planisphere to July 15th at 9:00pm. Name a constellation that is RISING (on the East Horizon). Pegasus Delphinius Aquarius Capricornus

Planisphere Practice: Set your planisphere to April 15th at 11:00pm. Name a constellation that is SETTING (on the West Horizon). Gemini, Canis Minor, Cancer, Auriga