MAY 10, 2016 Beginning of Class: We looked into the future of the Glendale sky using Stellarium The sky is blue because the light bounces off the air molecules and scatters. Air molecules are better at scattering the color blue compared to other colors. So if aliens stole all of our air, there would be no color. They sky would look as if it were night, but with a bright sun. What about sunsets? (Noon) When the light hits from here, the sky is blue because of the air molecules A e r eh ps om t (Sunset) When the light hits from here, it is forced to travel through the low-amplitude air longer. Lowamplitude air is filled with dust and dust easily scatters the color red More dust in the air More red sky
may 11, 2016 Dynamic Range: The difference between the brightest and the darkest spots The biggest problem with observation in LA: Light Polution At night, the sky isn't completely black because lights from the ground (like buildings) bounce off the air molecules and into your eye. It makes it appear as though the sky is lighter. There are many many stars in the sky, but they aren't bright enough in the night sky for us to see them with the human eye. In a good dark sky, a person with good eyes could see about 6,000 stars. MAY 12, 2016 The Greeks created a magnitude system that measured the brightness of stars: The lower the number, the bright the star Example: Sirius is -0.7 They used Polaris as reference, but that was a bad move because Polaris is a variable star, meaning that it gets brighter and dimmer periodically. The Greeks then switched to Vega. Today, brightness of a star is measured by amount of energy per area per time. There's a handy system to quickly naming the brightest star in a constellation: Alpha Beta Gamma... Greek Alphabet + Constellation name
MAY 13, 2016 Azimuthal Grid: Grid in the sky The sky looks like a big flat hemisphere. Grid it off exactly like the globe with the horizon as the equator equivalent. The very top is called the zenith. Where are things? To describe the location of something use: The angle above the horizon (altitude) + lines of longitude (azimuth) If the altitude is negative, it's below the horizon. Due North is 0 degrees azimuth. Arbitrary, based on where you stand Remember the Arclength Formula: S=Rθ Angular width of something: Take a line from one end of the object to the eyeball and another line from the other end of the object to the eyeball. The angular width is the angle difference in the lines. Tricks to measure degrees: The thumb is about 2 degrees long The fist is about 10 degrees long The full Moon and the Sun are both about.5 degrees long The Azimuthal coordinates of something are constantly changing because the sky moves. They are based on your position and time.
MAY 20 2016 Degrees/Minutes/Seconds: ' 1 Minute = 1 = 1/60 (or arcminute) 1 Second = 1 = 1/60 (or arcsecond) 23 54 27.932 -> 23 + 54/60 + 27.932/3600 = 23.907759 38.2 -> 38 12 Why?.2 = 1/5 = 1/5 (60 ) 38.2997143 ->? How many 1/60 in 0.2997143? 0.2997143 /(1/60) = 17.982858 How many 1/60 in.982858? 1.982858 /(1/60) = 58.971 Answer: 38 17 58.971 MAY 22, 2016 Cool air is better than warm air when stargazing. It's better to watch at 3 a.m. than at 9 p.m. because throughout the day, the ground absorbs heat. At 9, the air takes some of the heat off of the ground. By 3, the ground has completely cooled off and the air is at its coldest. Syzygy: When any 3 things line up and make a straight line Opposition: When the object you're talking about is on the other side of another object.
MAY 25, 2016 ECLIPTIC: Path of the Sun on the celestial sphere The seasons are based on the Sun's position in relation to the ecliptic Lowest point: Winter solstice (December 21) Crosses the equator: Spring/Autumnal Equinox (March 20/Sept 22) Highest point: Summer solstice (June 20) The exact date shifts by about 20 minutes per year and it would take 11,000 years to get a 6 month shift (though it doesn't show this on Stellarium due to a flaw in the software) The Summer solstice is the longest day of the year and the Winter solstice, the shortest. On the days of the equinox, there is the same amount of day and night. QUESTION: If June 20th is the longest day of the year, why isn't it the hottest? And if December 21 is the shortest day of the year, why isn't it the coldest? ANSWER: The Earth s oceans and atmosphere act as heat sinks and absorb the sun s warm rays. During the longest days of the year, they absorb the most heat and then retain that heat. This retention makes July and August the hottest months of the year. After a certain point, more heat is lost at night than is gained during the day. This cooling trend continues until after the winter solstice when the days become longer and more heat enters the atmosphere. Similarly, the shortest day of the year isn t the coldest, January and February are usually the coldest months.
MAY 26, 2016 Beginning of class: Set things on fire using Maine's mirror and telescope. QUESTION: What's the difference between a lunar eclipse and a solar eclipse? ANSWER: In a lunar eclipse, you cannot see the moon because it is blocked by the Earth's shadow. In a solar eclipse, the the sun is not visible because it is blocked by the moon. QUESTION: Why don't eclipses happen once a month? ANSWER: The galaxy is not flat and the moon's orbit is a little tilted. Lunar eclipses happen more often than solar eclipses because the shadow cast by the Earth is quite a bit larger than the Moon.
MAY 27, 2016 Apod.nasa.gov: A site with pretty pictures and not-complicated explanations How has astronomy changed? Major improvement: Telescopes Galileo's telescope = A modern-day pair of decent binoculars But binoculars are better because they give a brighter image than the telescope. It's kind of like artificially giving yourself bigger pupils. Main Function of Telescopes/Binoculars: Get the most light possible. Without a telescope Jupiter looks like a point in the sky. If you had really good eyes, and it were either half as far or twice as big, you could see it as a ball. With a telescope/binoculars, you could see it as a planet with moons. The moons of Jupiter The discovery of the moons of Jupiter was the most important find in all of science. QUESTION: Why were the moons of Jupiter discovered sooner than the moons of a closer planet, like Mars? ANSWER: Mars's moons are very tiny compared to Jupiter's. When observing Jupiter and its moons, you will notice that the moons change place noticeably after just an hour. This is due to their fast orbit.
Observation Even with a telescope, planets look blurry because you are looking through kilometers of air and wind. The biggest factor in visual astronomy: Strength of the stratosphere LA has pretty stable air The Horsehead Nebula can't be seen with the naked eye because it is very very far away and super dim. Images of the nebula are created with a 2-hour long exposure. MAY 31, 2016 When you look at the moon, you are actually seeing it 1 second late. When looking at a star, you are seeing it as it was 60 years ago. With the Andromeda Galaxy, it's 2-3 million years! QUESTION: Of all the stars we can see, how many are still there? ANSWER: Probably all of them because most of them are close, about only a few thousand light years. A few thousand years is a tiny tiny fraction of the life of a star. Eta Carinae is going to blow up, and when it does, it might unleash a super nova that would illuminate the sky for more than a week. It is 7500 light years away. The Milky Way will crash with the Andromeda Galaxy in 4-5 billion years. We spent the rest of the class time watching galaxy collision simulations.
JUNE 1 2016 Maine brought in his telescope and we talked about it for a little bit before going outside to try and see the moon. Large telescopes like his don't focus well on close objects because light rays from close objects diverge a lot. When the mirrors of the telescope have to put together the picture, the image comes out blurry. With far away objects, the light rays are almost parallel. Astro-photography is expensive because the image requires a really long exposure. The camera needs to be fixed with big heavy steel parts with are costly. Maine's telescope creates an upside down image. This doesn't really matter when it comes to observing the sky. Bird watchers wouldn't appreciate this though. How big is stuff? Earth's diameter: 8,000 miles or 13,000 km Distance to the moon: 30 Earth Diameters (slightly over a light second) There would be an awkward 2 second pause in phone calls between Earth and the Moon because radio waves are light waves.