Astronomy
1st Edition
ISBN: 9781938168284
Author: Andrew Fraknoi; David Morrison; Sidney C. Wolff
Publisher: OpenStax
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Textbook Question
Chapter 19, Problem 32E
The best parallaxes obtained with Hipparcos have an accuracy of 0.001 arcsec. If you want to measure the distance to a star with an accuracy of 10%, its parallax must be 10 times larger than the typical error. How far away can you obtain a distance that is accurate to 10% with Hipparcos data? The disk of our Galaxy is 100,000 light-years in diameter. What fraction of the diameter of the Galaxy’s disk is the distance for which we can measure accurate parallaxes?
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Let us imagine that the spectrum of a star is collected and we find the absorption line of Hydrogen-Alpha (the deepest absorption line of hydrogen in the visible part of
the electromagnetic spectrum) to be observed at 656.5 nm instead of 656.3 nm as measured in a lab here on Earth. What is the velocity of this star in
m/s? (Hint: speed of light is 3*10^8 m/s; leave the units off of your answer)
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Let us imagine that the spectrum of a star is collected and we find the absorption line of Hydrogen-Alpha (the deepest absorption line of hydrogen in the visible part of the electromagnetic spectrum) to be observed at 656.5 nm instead of 656.3 nm as measured in a lab here on Earth. What is the velocity of this star in m/s? (Hint: speed of light is 3*10^8 m/s; leave the units off of your answer)
White Dwarf Size II. The white dwarf, Sirius B, contains 0.98 solar mass, and its density is about 2 x 106 g/cm?. Find the radius of the white dwarf in km to three significant digits. (Hint: Density = mass/volume, and the volume of a
4
sphere is Tr.)
3
km
Compare your answer with the radii of the planets listed in the Table A-10. Which planet is this white dwarf is closely equal to in size?
I Table A-10 I Properties of the Planets
ORBITAL PROPERTIES
Semimajor Axis (a)
Orbital Period (P)
Average Orbital
Velocity (km/s)
Orbital
Inclination
Planet
(AU)
(106 km)
(v)
(days)
Eccentricity
to Ecliptic
Mercury
0.387
57.9
0.241
88.0
47.9
0.206
7.0°
Venus
0.723
108
0.615
224.7
35.0
0.007
3.4°
Earth
1.00
150
1.00
365.3
29.8
0.017
Mars
1.52
228
1.88
687.0
24.1
0.093
1.8°
Jupiter
5.20
779
11.9
4332
13.1
0.049
1.30
Saturn
9.58
1433
29.5
10,759
9.7
0.056
2.5°
30,799
60,190
Uranus
19.23
2877
84.3
6.8
0.044
0.8°
Neptune
* By definition.
30.10
4503
164.8
5.4
0.011
1.8°
PHYSICAL PROPERTIES (Earth = e)…
Chapter 19 Solutions
Astronomy
Ch. 19 - Explain how parallax measurements can be used to...Ch. 19 - Suppose you have discovered a new cepheid variable...Ch. 19 - Explain how you would use the spectrum of a star...Ch. 19 - Which method would you use to obtain the distance...Ch. 19 - What are the luminosity class and spectral type of...Ch. 19 - The meter was redefined as a reference to Earth,...Ch. 19 - While a meter is the fundamental unit of length,...Ch. 19 - Most distances in the Galaxy are measured in...Ch. 19 - The AU is defined as the average distance between...Ch. 19 - What would be the advantage of making parallax...
Ch. 19 - Parallaxes are measured in fractions of an...Ch. 19 - For centuries, astronomers wondered whether comets...Ch. 19 - The Sun is much closer to Earth than are the...Ch. 19 - Parallaxes of stars are sometimes measured...Ch. 19 - Estimating the luminosity class of an M star is...Ch. 19 - Figure 19.9 is the light curve for the prototype...Ch. 19 - Which of the following can you determine about a...Ch. 19 - A G2 star has a luminosity 100 times that of the...Ch. 19 - A star has a temperature of 10,000 K and a...Ch. 19 - What is the advantage of measuring a parallax...Ch. 19 - What is the disadvantage of the parallax method,...Ch. 19 - Luhman 16 and WISE 0720 are brown dwarfs, also...Ch. 19 - Most stars close to the Sun are red dwarfs. What...Ch. 19 - Why would it be easier to measure the...Ch. 19 - When Henrietta Leavitt discovered the...Ch. 19 - A radar astronomer who is new at the job claims...Ch. 19 - The New Horizons probe flew past Pluto in July...Ch. 19 - Estimate the maximum and minimum time it takes a...Ch. 19 - The Apollo program (not the lunar missions with...Ch. 19 - In 1974, the Arecibo Radio telescope in Puerto...Ch. 19 - Demonstrate that 1 pc equals 3.091013 k m and that...Ch. 19 - The best parallaxes obtained with Hipparcos have...Ch. 19 - Astronomers are always making comparisons between...Ch. 19 - Gaia will have greatly improved precision over the...Ch. 19 - Using the same techniques as used in Exercise...Ch. 19 - The human eye is capable of an angular resolution...Ch. 19 - How much better is the resolution of the Gaia...Ch. 19 - The most recently discovered system close to Earth...Ch. 19 - What would the parallax of Luhman 16 (see Exercise...Ch. 19 - The New Horizons probe that passed by Pluto during...Ch. 19 - What physical properties are different for an M...
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