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Intro to Astronomy. “Equipped with his five senses, man explores the universe around him and calls the adventure science.” Edwin P. Hubble (1889-1953), The Nature of Science. On Your Card. Write your name NEATLY List one interesting fact about yourself
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Intro to Astronomy “Equipped with his five senses, man explores the universe around him and calls the adventure science.” Edwin P. Hubble (1889-1953), The Nature of Science
On Your Card • Write your name NEATLY • List one interesting fact about yourself • List one interesting fact about someone else in the classroom • List one fact you already know about astronomy
Quick rules • Be nice – penalty jar • Be on time – even a moment is a moment too late • Participate – I won’t drag you through this. • Act like you are ready to graduate soon – Quality work is the only acceptable work • Passes/TP points • Logbook
Books and Other Resources • Horizons: Exploring the Universe • Soft cover • Gentle! • Other resources • Bad Astronomy by Phil Plait • Articles – NY Times • DVDs/Videos • Online resources • Your notes – take them!
Old NASA cards 3-2-1 • Select NASA card and informally present to the class: • 3 facts • 2 pertinent vocabulary words • 1 question you still have
Astronomy is not Astrology • Astronomy – from Greek - ‘star arranging’ • We are here to learn more about the sky, the planets, interplanetary motion, the Milky Way, etc. • We will not be telling anyone’s horoscope. But we did add a new sign… • Everyone here knows something; no one here knows everything about astronomy. I welcome contributions. We can make this course go anywhere you choose – it just won’t “sit still”.
Misconceptions • Too numerous to name! • Example: Standing an egg on the Vernal Equinox • Vernal Equinox - The date (near March 21 in the northern hemisphere) when night and day are nearly the same length and the sun crosses the celestial equator moving northward = First day of Spring! • Let’s try it!
Bad Astronomy in Our Everyday Lives • We misuse astronomical (and other) phrases on a daily basis. • As an intro to Astronomy, let’s clear some up!
“Shoot for the moon. Even if you miss, you’ll land among the stars” • Sorry to disappoint, but there are no starts between here and the moon. • You’d have to really overshoot the moon to “land among the stars” since our nearest neighboring star which is not the sun (Alpha Centauri) is 4.2 light years away.
“A Meteoric Rise” • Bad Astronomy: Commenting on an up-and-coming person as having "a meteoric rise”. • Good astronomy: Meteors don't rise. They fall. • This phrase has the exact opposite meaning of what it is trying to say!
What is a meteor? • A meteoroid is any bit of detritus floating around in space, whose path intersects the Earth's. • It becomes a meteor when it hits the Earth's atmosphere and burns up. • If it impacts the ground, it's called a meteorite.
Meteors start off in space, and then fall to the Earth. They appear dramatically, flashing into our view, and burn out suddenly, sometimes leaving a long trail of glowing ash behind them. • On a clear night – 2-3/hour
Meteor Showers • Perseid shower - ~August 13th every year • >60/hour • Video • Leonids shower • Associated w/ comet Tempel-Tuttle • November • Superspurts: 1799, 1833*, 1866, 1966 • >2000/hour! • *1833 – 200,000/hour! • These meteors are associated with bits and pieces of comets that slough off as the comet orbits the Sun.
Several Leonid meteors are visible in the upper left of a time-exposure photograph taken on Nov. 18, 2001, near Las Cruces, N.M. • Video
More “Bad Science” about Meteorites • Aren’t glowing red when they hit • Slow down significantly entering atmosphere; melted stuff ablates • Large ones (meters across) can be much faster • A car in New York was struck by a small meteorite and had a hole punched through it and the whole back end crushed in. Ouch! • Incoming! • Meteor in Russia 2013 • Another video of the Russian meteorite
“Light years ahead” • Bad Astronomy: "We're light years more advanced than our competition!” • Good astronomy: There is no good astronomy equivalent here. The phrase is just wrong!
How it works: • Light is terrifically fast • To the moon: just over 1 second • To the sun: 8 minutes • To distant Pluto: 6 hours • To nearest known star: 4.3 years • It will travel 9,500,000,000,000 km in one year. This distance is defined as a light year (ly). • So “light years” is a measure of distance, not time.
A Star Wars Connection • In the movie Star Wars, Han Solo brags that he can make the Kessel Run in less than 12 parsecs. • This is another example of Bad Astronomy. • Like a light year, a parsec is a unit of distance, not time (= 3.26 light years). • 1 Parsec (pc) = 3.08568025 × 1016 meters or about 19 trillion miles • "parallax of one arcsecond”
Where did “parsec” come from? • Though it had probably been used before, the term parsec was first mentioned in an astronomical publication in 1913, when Astronomer Royal Frank Watson Dyson expressed his concern for the need of a name for that unit of distance: he proposes the name astron, but mentions that Carl Charlier had suggested siriometer, and Herbert Hall Turner had suggested parsec (parallax second).
“Dark Side of the Moon” • Bad Astronomy: "That's as remote as the dark side of the Moon!” • Good astronomy: "That's as remote as the far side of the Moon!" • Good intro to the Phases of the Moon • Bright side = hemisphere we always see; not a fixed place; bright for only 2 weeks; a.k.a. the nearside • Farside = hemisphere we don’t see; has only been seen by probes or astronauts that have actually orbited the moon
Phase of the Moon • New moon - when the Moon is between the Earth and the Sun, we see it almost entirely in shadow • Full moon - half a lunar orbit after the new moon (two weeks or so) it is fully illuminated by the Sun • In between we get a half moon, sometimes confusingly called a quarter moon because the Moon has completed 1/4 of an orbit.
Bad Moon Risin’ • The reason for the Moon's phases depends on two things: the Moon is round, and the angle it makes with the Earth and Sun changes over its orbit
Waxing and Waning • Waxing – means “growing” • Waning – means “shrinking” • Crescent • Gibbous – “swollen on one side” • Sequence: New moon waxing crescent first quarter waxing gibbous full moon waning gibbous third quarter waning crescent new moon etc.
Phases of the Moon • Animation • Lunar phases repeat every 29.5 days (the synodic period) • Oreo Moon Phases Lab • More in Chapter 3! Read p. 25-30
More General Moon Info • The Universe - The Moon • Moon – from the Latin mensis (month) • Latin: Luna • Earth’s only natural satellite • 5th largest natural satellite in Solar System • Fairly large compared to Earth • Average center-to-center distance from the Earth to the Moon: 384,403 km • Formation – Remember the movie?
The Moon By the Numbers • Diameter: 3,474 km • A little more than ¼ of Earth • Moon's volume: ~2% of Earth’s • Circumference: 10,921 km (equatorial) • Gravity: 17% of Earth’s • What is gravity? • Acceleration due to gravity on Earth = 9.8 m/s2 • F ~ m1m2/d2;F = G (m1m2/d2) • Makes a complete orbit around the Earth every 27.3 days (the orbital period) • Periodic variations in the geometry of the Earth-Moon-Sun system are responsible for the lunar phases that repeat every 29.5 days (the synodic period).
The Moon’s Surface • The Universe – The Moon • Impact craters
Impact craters (cont.) • Half a million craters with diameters greater than 1 km can be found • Cool fact: Since impact craters accumulate at a nearly constant rate, the number of craters per unit area superposed on a geologic unit can be used to estimate the age of the surface (crater counting) • No weather (no atmosphere) so craters stay preserved
South Pole-Aitken basin - largest known craters in the Solar System • Topographical map of the South Pole-Aitken basin based on Clementine data. Red represents high elevation, purple represents low elevation.
The South Pole-Aitken basin is the darker area at the bottom of this image.
Moon surface images/info • From The Moon video: • Maria • Lava filled craters • Regolith • Ground up rock – fine dusty layer • Breccia • Rocks formed during asteroid impacts • Basaltic rock • Volcanic rock
Movement of the Moon • Relative to the stars, the moon moves eastward in the sky each night. • How far each night? • 360°/27.3 days per orbit = ? • ~13°/night • So a Moon day = 27.3 Earth days and a Moon year (time it takes to orbit the Earth) is also 27.3 days
Each phase is therefore located at a slightly different place on the horizon and at different times: • The waxing crescent moon is visible near the western horizon just after sunset. • The first quarter moon rises at about noon. • A third quarter moon is visible in the southern sky at sunrise. • The waning crescent moon is visible above the eastern horizon a couple of hours before sunrise.
Still confused? Me too! • The New Moon transits about the same time as the Sun ... it rises and sets with the Sun. • The Waxing Crescent Moon transits less than 6 hours after the Sun. It rises in the east after sunrise and before noon. It is seen in the southern sky after 12 noon and in the western night sky just after sunset appearing higher in the sky with each successive evening. It sets before midnight.
The First Quarter Moon transits 6 hours after the Sun. It rises in the east at about noon, appears in the southern sky at sunset and sets in the west 6 hours after the Sun around the midnight hour. • The Waxing Gibbous Moon transits more than 6 but less than 12 hours after the Sun. It rises in the east after 12 noon and before sunset. It is seen in the southern sky after sunset and before midnight and sets after midnight and before sunrise.
The Full Moon transits 12 hours after the Sun. It rises in the east as the Sun sets in the west, appears in the southern sky around the midnight hour and sets in the west at sunrise. • The Waning Gibbous Moon transits more than 12 and less than 18 hours after the Sun. With each successive night after the Full Moon, the waning Moon rises in the east about 48 minutes later until it is rising in the early morning hours. (Some prefer using 1 hour rather than 48 minutes in approximating the moonrise.) It appears in the southern sky before sunrise and sets in the afternoon.
The Third Quarter Moon transits 6 hours before the Sun. This Moon rises in the east in the early morning hours, appears in the southern sky at sunrise and sets in the west 6 hours before the Sun. • The Waning Crescent Moon transits less than 6 hours before the Sun. It rises less than 6 hours before the Sun, appears in the southern sky less than 6 hours before noon and sets less than 6 hours before the Sun.
Celestial Calendar for 2012 • Current Moon Phases • Full Moon – February 7 • Last Quarter – February 14 • New Moon – February 21 • First Quarter – February 29
To the moon, Alice! • The Moon is the only celestial body to which humans have traveled and upon which humans have performed a manned landing. The first artificial object to pass near the Moon was the Soviet Union's Luna 1, the first artificial object to impact the lunar surface was Luna 2, and the first photographs of the normally occluded far side of the Moon were made by Luna 3, all in 1959. The first spacecraft to perform a successful lunar soft landing was Luna 9; this was soon followed with the first successful lunar soft landing by Surveyor 1 and the first unmanned vehicle to orbit the Moon by Luna 10, all in 1966. The U.S. Apollo program achieved the only manned missions to date, resulting in six landings between 1969 and 1972. Human exploration of the Moon ceased with the conclusion of the Apollo program, although a few robotic landers and orbiters have been sent to the Moon since that time. Several countries have announced plans to return humans to the surface of the Moon in the 2020s.
Lunar Landing Hoax? • YouTube will give you an earful! • Bad Astronomy – A Whole Chapter! • Myth Busters Part #1 • Bad Astronomy online • Myth Busters Additional Footage
