Astronomy 101The Solar System

Tuesday, Thursday2:30-3:45 pmHasbrouck 20

Tom Burbinetomburbine@astro.umass.edu

Course

• Course Website:– http://blogs.umass.edu/astron101-tburbine/

• Textbook:– Pathways to Astronomy (2nd Edition) by Stephen Schneider

and Thomas Arny.• You also will need a calculator.

Office Hours

• Mine

• Tuesday, Thursday - 1:15-2:15pm

• Lederle Graduate Research Tower C 632

• Neil

• Tuesday, Thursday - 11 am-noon

• Lederle Graduate Research Tower B 619-O

Homework

• We will use Spark

• https://spark.oit.umass.edu/webct/logonDisplay.dowebct

• Homework will be due approximately twice a week

Homework #1 (Email it to me if you have not submitted it)

• Find an article concerning a topic concerning the Solar System and write about why you found it interesting.

• Include the name of the article and where it was published.

• Submit using Spark

Homework #2 (due today)

• 10 questions

• In Assessment on Spark

HW #3 (due Thursday)

• 10 questions

• In Assessment in Spark

Let’s look at the sky

• http://www.skyandtelescope.com

Terminology for looking at the sky

Celestial Poles

• The altitude of the celestial pole (near Polaris) is equal to your latitude

• If the altitude of the celestial pole is 50 degrees, you latititude is 50 degrees

Angular size

• We measure distances in the sky using angles

• 180o in the observable sky

More precise distances

• 1 degree = 60 arcminutes (symbol ´)

• 1 arcminute = 60 arcseconds (symbol ´´)

• So something that is 2 degrees, 10 arcminutes, 22 arcseconds would be written as

• 2o 10´ 22´´

Star positions change versus latitude

Astrology

• Astrology by birth sign or sun sign means that your particular horoscope characteristics are based mainly upon the location of the sun's astrological position in the zodiac at the time of your birth.

Aries (21 March - 20 April)

• Arians have a tendency to act like a dynamo of energy when they set their mind on achieving some goal. They can sometimes act so quickly that they later discover that they should have put in just a little more thought before starting. Action and achievement are important and slow pokes that get in the way, watch out! Aries may step on your toes. Aries enthusiasm rubs off onto others and they get involved in something, others are ready to follow. Selfishness, which sometimes includes a need to control others, tarnishes their otherwise positive and adventurous spirit. They need to have empathy and concern for the needs of others. As a lover, they are passionate, giving and enterprising.

Seasons

• You an use the location of different constellations in the sky to tell what season it is

Video

• http://www.learner.org/resources/series28.html

Precession• Gravity-induced, slow and continuous change in

an astronomical body's rotational axis

• Gradual shift in the orientation of Earth's axis of rotation, which, like a wobbling top, traces out a cone in a cycle of approximately 26,000 years

http://en.wikipedia.org/wiki/File:Earth_precession.svg

http://calgary.rasc.ca/images/radec_earth_precession.gif

Implications

• Polaris won’t always be the North Star

http://en.wikipedia.org/wiki/File:Lunar-Phase-Diagram.png

Eclipses

Moon is tilted at an angle of 5 degrees to Earth’s orbit

• http://astronomyonline.org/SolarSystem/LunarEclipse.asp

Color of lunar eclipse• The Moon does not completely disappear because of the

refraction of sunlight by the Earth’s atmosphere

• If the Earth had no atmosphere, the Moon would be completely dark during an eclipse.

• The red color arises because sunlight reaching the Moon must pass through the Earth’s atmosphere, where it is scattered.

• Shorter wavelengths are more likely to be scattered by the small particles. By the time the light has passed through the atmosphere, the longer wavelengths dominate. This resulting light reflected from the Moon we perceive as red.

Solar eclipse

http://en.wikipedia.org/wiki/Image:Solar_eclips_1999_4_NR.jpg

• Solar eclipses occur approximately every 18 months• However, they recur (on average) at any given place only

once every 370 years• Moon's umbra moves eastward at over 1,700 km/hr

• Every year, there are at least two lunar eclipses. • Can be viewed anywhere on the night side of the Earth

http://home.cogeco.ca/~astrosarnia/Photos/Lunar%20eclipse%20binocular.jpg

Solar eclipse of July 22, 2009

• Lasted a maximum of 6 minutes and 39 seconds off the coast of Southeast Asia

http://en.wikipedia.org/wiki/File:Solar_eclipse_22_July_2009_taken_by_Lutfar_Rahman_Nirjhar_from_Bangladesh.jpg

http://upload.wikimedia.org/wikipedia/commons/f/f2/Solar_eclipse_animate_%282009-Jul-22%29.gif

Models

• When you have a model of how something works, you should be able to predict what will happen

• If observations do not fit the model, either the observations or the model is wrong

• The ancient astronomers wanted to predict the positions of planets in the sky

What did the ancients think

• That the Earth was the center of the universe

• That the celestial sphere was rotating around the Earth

• However, there was two observations that caused problems with this idea– Apparent retrograde motion– Inability to detect stellar parallax

Greek model

Apparent Retrograde Motion = “backward” motion

Retrograde Motion

Retrograde

• Planet appears to go backwards in its orbit

Stellar Parallax

• Stellar Parallax – The apparent shift in the position of a nearby star (relative to distant objects) that occurs as we view the star from different positions in the Earth’s orbit of the Sun each year

The distance the star moves is greatly exaggerated in this figure.Stellar parallax can only be seen by a telescope.

Ancient astronomers could not detect stellar parallax

• If Earth orbited the Sun, ancient astronomers believed that they would see differences in angular separation of stars as the Earth rotated around the Sun

• Since they saw no changes in angular separation of the stars, they assumed the Earth was the center of the universe

• They could not fathom that stars are so far away that stellar parallax is undetectable by the human eye

Any Questions?