Announcements First exam will be on Friday, September 17 All lecture notes and a practice exam are...
-
Upload
pearl-neal -
Category
Documents
-
view
215 -
download
0
Transcript of Announcements First exam will be on Friday, September 17 All lecture notes and a practice exam are...
![Page 1: Announcements First exam will be on Friday, September 17 All lecture notes and a practice exam are available at the class web site at kaaret/sgu_f04.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649ea85503460f94babada/html5/thumbnails/1.jpg)
Announcements
• First exam will be on Friday, September 17
• All lecture notes and a practice exam are available at the class web site at http://phobos.physics.uiowa.edu/~kaaret/sgu_f04
• Astronomy tutorials will be held in 618 VAN on Tuesday 12:30-2:30 pm, Thursday 11:00 am - noon, and Friday 10:30-11:30 am.
• Observing continues on the roof of Van Allen Hall this week, Monday-Thursday 9-11 pm. Go and get the extra credit.
![Page 2: Announcements First exam will be on Friday, September 17 All lecture notes and a practice exam are available at the class web site at kaaret/sgu_f04.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649ea85503460f94babada/html5/thumbnails/2.jpg)
Announcements
• Wednesday will be a review session
• Please hand-in or e-mail questions for the review session.
• If time permits, we will play “Who wants to be a millionaire astronomer” based on the questions on the practice exam. Anyone who can reach the millionaire level gets an automatic 100% score on Friday’s exam.
![Page 3: Announcements First exam will be on Friday, September 17 All lecture notes and a practice exam are available at the class web site at kaaret/sgu_f04.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649ea85503460f94babada/html5/thumbnails/3.jpg)
Today’s topics
• Phases of the Moon
• Angular size and physical size
• Precession of the Earth
• Reading sections 2.3-2.4, 3.1-3.5
![Page 4: Announcements First exam will be on Friday, September 17 All lecture notes and a practice exam are available at the class web site at kaaret/sgu_f04.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649ea85503460f94babada/html5/thumbnails/4.jpg)
Phases of the Moon
![Page 5: Announcements First exam will be on Friday, September 17 All lecture notes and a practice exam are available at the class web site at kaaret/sgu_f04.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649ea85503460f94babada/html5/thumbnails/5.jpg)
Phases of the Moon
• The phases of the Moon are caused by the orbit of the Moon around the Earth, but how does this work?
• Any thoughts?
![Page 6: Announcements First exam will be on Friday, September 17 All lecture notes and a practice exam are available at the class web site at kaaret/sgu_f04.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649ea85503460f94babada/html5/thumbnails/6.jpg)
Moon’s Orbit• Relative to the Sun, the
Moon orbits the Earth once every 29.5 days (relative to the stars the orbit is 27.3 days)
• The orbit of the Moon is tilted by about 5 degrees relative to the ecliptic
• The Moon rotates at the same rate that it orbits, so the same face of the Moon always points towards Earth
![Page 7: Announcements First exam will be on Friday, September 17 All lecture notes and a practice exam are available at the class web site at kaaret/sgu_f04.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649ea85503460f94babada/html5/thumbnails/7.jpg)
Phases of the Moon
Picture taken by Galileo spacecraft from 4 million miles away
![Page 8: Announcements First exam will be on Friday, September 17 All lecture notes and a practice exam are available at the class web site at kaaret/sgu_f04.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649ea85503460f94babada/html5/thumbnails/8.jpg)
Phases of the Moon
![Page 9: Announcements First exam will be on Friday, September 17 All lecture notes and a practice exam are available at the class web site at kaaret/sgu_f04.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649ea85503460f94babada/html5/thumbnails/9.jpg)
![Page 10: Announcements First exam will be on Friday, September 17 All lecture notes and a practice exam are available at the class web site at kaaret/sgu_f04.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649ea85503460f94babada/html5/thumbnails/10.jpg)
Does the Earth have phases? (as seen from the Moon)
![Page 11: Announcements First exam will be on Friday, September 17 All lecture notes and a practice exam are available at the class web site at kaaret/sgu_f04.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649ea85503460f94babada/html5/thumbnails/11.jpg)
Do the planets have phases?
![Page 12: Announcements First exam will be on Friday, September 17 All lecture notes and a practice exam are available at the class web site at kaaret/sgu_f04.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649ea85503460f94babada/html5/thumbnails/12.jpg)
Phases of the Planets
![Page 13: Announcements First exam will be on Friday, September 17 All lecture notes and a practice exam are available at the class web site at kaaret/sgu_f04.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649ea85503460f94babada/html5/thumbnails/13.jpg)
Sizes of Astronomical Objects
• How can we measure the sizes of astronomical objects?
• The same way that we measure distances – using triangles
![Page 14: Announcements First exam will be on Friday, September 17 All lecture notes and a practice exam are available at the class web site at kaaret/sgu_f04.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649ea85503460f94babada/html5/thumbnails/14.jpg)
The Small-Angle Formula D = linear size of object
θ = angular size of object (in arcsec)
d = distance to the object206265
dD
![Page 15: Announcements First exam will be on Friday, September 17 All lecture notes and a practice exam are available at the class web site at kaaret/sgu_f04.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649ea85503460f94babada/html5/thumbnails/15.jpg)
Example: On November 28, 2000, the planet Jupiter was 609 million kilometers from Earth
and had an angular diameter of 48.6″. Using the small-angle formula, determine Jupiter’s actual
diameter.
D = 48.6″ x 609,000,000 km / 206265 = 143,000 km
The Small-Angle Formula D = linear size of object
θ = angular size of object (in arcsec)
d = distance to the object206265
dD
![Page 16: Announcements First exam will be on Friday, September 17 All lecture notes and a practice exam are available at the class web site at kaaret/sgu_f04.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649ea85503460f94babada/html5/thumbnails/16.jpg)
Precession
• If you spin a top, its very hard to get it to spin exactly straight – usually it wobbles around in a circle
• The spinning Earth wobbles in exactly the same way – this is called precession
![Page 17: Announcements First exam will be on Friday, September 17 All lecture notes and a practice exam are available at the class web site at kaaret/sgu_f04.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649ea85503460f94babada/html5/thumbnails/17.jpg)
Precession of the Earth