Homework 9! This is a preview of the draft version of the quiz Started: Mar 29 at 9:24pm Quiz Instruc!ons Question 1 The Sun's spectrum peaks in the yellow-green region of optical light. The Main Sequence star Rigel is larger than the Sun. Rigel has a spectrum that peaks in the shortest-wavelength region of visible light. Compared with the Sun, Rigel is more massive and cooler less massive and hotter less massive and cooler more massive and hotter Question 2 Our Sun has an absolute magnitude of about +5 and a surface temperature of about 5800K. Our Sun's spectrum shows that our Sun is a G-type star. If an astronomer observes a K-type star that has an absolute magnitude of -10, what can this astronomer infer? This K-type star has a surface temperature larger than the Sun This K-type star is on the Main Sequence This K-type star is a bigger size than the Sun This K-type star is less luminous than the Sun
Question 3 Which wavelength region is most useful for investigating the dense cores inside the giant molecular clouds that collapse to form protostars? Infrared X-ray Ultraviolet Visible Question 4 Protostars are slowly expanding at the surface while the core contracts contracting and heating up heating up and expanding contracting and cooling Question 5 All stars on the Main Sequence generate energy by hydrogen fusion in their cores
have the same age, to within a few million years are changing slowly in size, due to gravitational contraction are the same size as our Sun Question 6 As you move downward and to the right on the Hertzsprung-Russell diagram the stars become cooler and redder hotter and redder cooler and bluer hotter and bluer Question 7 If a protostar were able to contract (get smaller) without any change in its surface temperature, what would happen to its luminosity? Hint: Place a point on the Hertzsprung-Russell diagram about where you would expect a protostar to exist. Move the point in the appropriate direction for the protostar to be contracting, but don't allow an increase or a decrease in temperature. How is the point moving relative to the luminosity axis of the H-R diagram? It is not possible to predict the change in the protostar's luminosity since other factors are involved The protostar's luminosity would increase due to the compression of its surface gas The protostar's luminosity would decrease due to its reduced surface area
The protostar's luminosity would remain the same since its temperature does not change Question 8 The Hyades is the nearest star cluster to the Earth. Assuming that all the stars in the Hyades are on the Main Sequence, the most luminous star in the Hyades is the star that has the smallest temperature the star that has the smallest mass the star that has the smallest radius the star that emits light with the smallest wavelength Question 9 An astronomer plots the H-R diagram of a star cluster and finds that it contains hot B-type stars on the Main Sequence and cooler G- and K-type stars noticeably above the Main Sequence. This cluster is of indeterminate age. The age of a star cluster cannot be estimated from the information given impossible. In the same star cluster, cool stars cannot be above the Main Sequence when hot stars are on the Main Sequence very old because the G and K stars are already moving off (away from) the Main Sequence very young because the G and K stars are still moving onto (towards) the Main Sequence
Question 10 By carefully compiling historical observations of our Sun, a future astronomer measures a shift in the Sun's position with a period of 500 years. She hypothesizes that our Sun is actually in a binary system and is being "wobbled" slowly by the gravity of a companion, Main Sequence, star. The companion star must have a mass less than one-fifth that of our Sun and be on a large circular orbit out beyond the edge of the Kuiper Belt (at about 0.0003 parsecs from the Earth). How could the scientist try to observe this companion star? There is no point looking...the companion star will be invisible as it will have burned through its hydrogen long ago By looking for an extremely slow-moving, faint object that is emitting light at very red or infrared wavelengths The scientist is wrong. This companion would be brighter than the Sun and would have been observed long ago The companion would orbit the Sun every 22 years, so look for stars that shift 16.3 o across the sky each year Not saved Submit Quiz