Astronomy
1st Edition
ISBN: 9781938168284
Author: Andrew Fraknoi; David Morrison; Sidney C. Wolff
Publisher: OpenStax
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Textbook Question
Chapter 19, Problem 22E
Luhman 16 and WISE 0720 are brown dwarfs, also known as failed stars, and are some of the new closest neighbors to Earth, but were only discovered in the last decade. Why do you think they took so long to be discovered?
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A 1.5 M neutron star and a 0.7 M white dwarf have been found orbiting each other with a period of 10 minutes. What is their average separation? Convert your answer to units of the Sun's radius, which is 0.0047 AU.
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)…
(Astronomy)
White Dwarf Size I.
The density of Sirius B is 2×106 g/cm3 and its mass is 1.95×1030 kg. What is the radius of the white dwarf in km? (Hint: Density = mass/volume, and the volume of a sphere is 4/3πr3)
Please round your answer to two significant digits.
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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Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, physics and related others by exploring similar questions and additional content below.Similar questions
- Why do you think astronomers have suggested three different spectral types (L, T, and Y) for the brown dwarfs instead of M? Why was one not enough?arrow_forwardWould you expect to find any white dwarfs in the Orion Nebula? (See The Birth of Stars and the Discovery of Planets outside the Solar System to remind yourself of its characteristics.) Why or why not?arrow_forwardHow much would you weigh if you were suddenly transported to the white dwarf Sirius B? You may use your own weight (or if don’t want to own up to what it is, assume you weigh 70 kg or 150 lb). In this case, assume that the companion to Sirius has a mass equal to that of the Sun and a radius equal to that of Earth. Remember Newton’s law of gravity: F=GM1M2/R2 and that your weight is proportional to the force that you feel. What kind of star should you travel to if you want to lose weight (and not gain it)?arrow_forward
- (Astronomy) (Part A) White Dwarf Size II. The white dwarf, Sirius B, contains 0.98 solar mass, and its density is about 2 × 106 g/cm3. Find the radius of the white dwarf in km to three significant digits. (Hint: Density = mass⁄volume, and the volume of a sphere is 4/3πr3). (Part B) 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?arrow_forwardWhat is the escape velocity (in km/s) from the surface of a 1.1 M. neutron star? From a 3.0 M, neutron star? (Hint: Use the formula for escape velocity, V̟ = 2GM -; make sure to express quantities in units of meters, kilograms, and seconds. Assume a neutron star has a radius of 11 km and assume the mass of the Sun is 1.99 × 1030 kg.) 1.1 M neutron star km/s 3.0 M. neutron star km/s If a neutron star has a radius of 12 km and a temperature of 8.0 x 10° K, how luminous is it? Express your answer in watts and also in solar luminosity units. (Hint: Use the relation . Use 5,800 K for the surface temperature of the Sun. The luminosity of the Sun is 3.83 x 1026 W.) luminosity in watts luminosity in solar luminosity units Loarrow_forwardCalculate the Kepler speed grazing the surface of a) a white dwarf, b) a neutron star. Give your answers in terms of the speed of light. (Take RNS = 10 km, RWD = 10 000 km, and MWD = MNS = 1 Msun.)arrow_forward
- Which of the following is least reasonable regarding novae and supernovae? Group of answer choices A type I (carbon-detonation) supernova results when a white dwarf in a binary system absorbs enough mass from its companion to push it over the Chandrasekhar limit. A type II supernova results from any supermassive star at the end of its life, when it runs out of fusion energy and collapses. A nova can occur multiple times in a binary system. If a white dwarf in a binary system absorbs enough mass to go beyond the Chandrasekhar limit, the white dwarf explodes as a supernova. The reason a type I supernova does not produce hydrogen lines is that the explosion originates from a stellar core (white dwarf), where hydrogen has already fused to produce heavier elements (so there is no longer any hydrogen). More supernovae are observed in the Milky Way because they are much closer to us than those in other galaxies.arrow_forwardWhat is the escape velocity (in km/s) from the surface of a 1.1 M. neutron star? From a 3.0 M. neutron star? (Hint: Use the formula for escape velocity, V̟ = V 2GM ; make sure to express quantities in units of meters, kilograms, and seconds. Assume a neutron star has a radius of 11 km and assume the mass of the Sun is 1.99 x 1030 kg.) 1.1 M neutron star km/s 3.0 M. neutron star km/s If a neutron star has a radius of 12 km and a temperature of 8.0 x 10° K, how luminous is it? Express your answer in watts and also in solar luminosity units. (Hint: Use the relation Use 5,800 K for the surface temperature of the Sun. The luminosity of the Sun is 3.83 x 1026 w.) luminosity in watts luminosity in solar luminosity unitsarrow_forwardUse the H-R Diagram below to help answer the following questions. Luminosity (solar units) 10,000+ 1,000+ 100+ 10- .01+ .001+ .0001 B White Dwarfs 20,000 B Spectral Type A Main Sequence D 10,000 Temperature (K) FGK Red Giants 5,000 M -5 10 15 Absolute Magnitudearrow_forward
- Why are red dwarfs very dim.arrow_forward(Astronomy) Binary Pulsar. Part A: Use the orbital period 27 min for the binary pulsar (two neutron stars orbit each other) to find the orbital separation of the pair in AU and solar radii. Assume a neutron star's mass is 3 solar masses. (Hints: Use the version of Kepler's third law for binary stars.) Part B: Is this system orbiting closer or further than Mercury is to the Sun?arrow_forwardWhy are Cepheid variables important? O Cepheids variables are pulsating stars whose pulsation periods are directly related to their true luminosities. Therefore they can be used as distance indicators. O Cepheids variables are supermassive stars that are on the verge of becoming supernovae. Therefore they allow us to choose candidates to watch if we hope to observe a supernova. O Cepheid variables are stars that vary in brightness because they harbor a black hole. Therefore, they provide direct evidence for black holes. O Cepheids variables are a type of irregular galaxy, much more common in the early universe. Therefore they help to understand how galaxies formed.arrow_forward
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