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Quiz 2
Physics 55: Introduction to Astronomy
Professor Henry Greenside
Monday, September 19, 2005
This quiz is closed book. You can use a scientific calculator but no other electronic device. If you have any
questions during the quiz, please do not hesitate to ask me.
True or False Questions (1 point each)
Please circle “T” for true or “F” for false to indicate the truth of the following statements.
1. T / F If one star has an altitude of 30◦ and a second star has an altitude of 70◦ , then the angular
distance between the two stars is 40◦ .
2. T / F Although the Big Dipper (also known as Ursa Major or the Big Bear) is one of the easiest and
most useful group of stars to identify for people living in the northern hemisphere, it is a bad place in
the sky to look for planets. (Note: The Big Dipper is not close to the ecliptic.)
3. T / F If the Earth were to reverse the direction of its orbit around the Sun but continue to rotate
about its axis the same way, the celestial sphere would reverse its direction of rotation in our night sky.
4. T / F Because Venus does not have any moons, the celestial coordinates RA and dec of some object
in the celestial sphere as seen from Venus do not have to be corrected by an epoch time.
Multiple Choice Questions (4 points each)
Circle the letter that best answers each of the following questions.
1. While traveling on a night cruise in December, you notice at 9 pm that the star Polaris is six fists and
two little fingers above the horizon when your arm is fully extended. You conclude that the altitude
of Polaris is
(a) 6◦ 20 N.
(b) 28◦ N.
(c) 62◦ N.
(d) 83◦ 580 N.
(e) Some other value.
2. On that same December night cruise, you would be comfortably dressed while standing out on the
deck if you were wearing
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(a) a bathing suit.
(b) shorts and a short-sleeve shirt.
(c) pants, a long-sleeved shirt, and a sweater.
(d) A heavy winter coat, a hat, a scarf, and gloves.
3. According to the above figure, around January 21 the zodiacal constellation closest to your meridian
at midnight will be
(a) Cancer.
(b) Capricornus.
(c) Taurus.
(d) Virgo.
(e) Some other constellation.
4. If the celestial coordinates of an object is RA 22h and dec −46◦ and if the winter solstice is on your
meridian at midnight when you are on Earth’s equator, then
(a) the object will cross your meridian about 4 hours after midnight.
(b) the object will cross your meridian about 4 hours before midnight.
(c) the object will cross your meridian during daytime and so not be visible.
(d) the object may not cross your meridian at all.
5. The rotational axis of Venus is tilted by an angle of about 177◦ with respect to the ecliptic plane. Over
a Venusian year of 0.62 Earth years, an astronomer on Venus (if it could look through Venus’s thick
cloud layer) would see the declination of the Sun vary over the range
(a) −3◦ to 3◦ .
(b) −177◦ to 177◦.
(c) −23.5◦ to 23.5◦.
(d) −156.5◦ to 156.5◦.
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(e) Some other range.
Open Questions
( 8 points) What is the altitude (to an accuracy of a minute) and the direction of the star Betelgeuse when
it crosses the meridian at midnight in the local sky of Sydney, Australia?
Some data: Sydney has a longitude of about 151◦ 170 East and a latitude of about 33◦ 550 South, while
Betelgeuse has a right ascension of about 5h 55m 10s and a declination of about 7◦ 240 .
You need to give the details of how you obtained your answer to get full credit for this problem.
Extra credit (3 points): How many minutes does it take the Moon to move across the celestial sphere
an amount equal to its angular width of 0.5◦ ? Some data: a synodic month is 29.5 days, a sidereal month
is 27.3 days, and a year is 365 days.
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