Concept explainers
(a)
The radius of the circumsteller accretion disc using ruler.
Answer to Problem 28Q
The radius of circumstellar accretion disc is
Explanation of Solution
Calculation:
The radius of circumstellar accretion disc is one-sixth of the measuring ruler which has a total length of
The radius of circumstellar accretion disc is calculated as,
The radius of circumstellar accretion disc in km is calculated as,
Conclusion:
The radius of circumstellar accretion disc is
(b)
The orbital period of the particle at outer edge of the disc.
Answer to Problem 28Q
The orbital period of particle is
Explanation of Solution
Given:
Mass of the young star is
Formula used:
The expression of orbital period is given by,
Calculation:
The orbital period of the particle at the edge of disc is calculated as,
Conclusion:
The orbital period of particle is
(c)
The length of the jet that extends to the right of the circumstellar accretion disc and time taken by the star to traverse the entire visible range of jet.
Answer to Problem 28Q
The distance of the jet extends to the right of the disc is
Explanation of Solution
Given:
Speed of the gas is
Formula used:
The expression of time taken is given by,
Calculation:
The length of the jet which extends at the right side of the circumstellar accretion disc is one third of the total length of about
The length of jet is calculated as,
The time taken by the gas is calculated as,
Conclusion:
The distance of the jet extends to the right of the disc is
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Chapter 18 Solutions
Universe: Stars And Galaxies
- 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)…arrow_forwardThe best parallaxes obtained with the Hipparcos satellite have an uncertainty such that we believe measurements as low as 0.005 arc-seconds. What is the farthest distance a star can be to have an accurate distance from Hipparcos? 200 Parsecs The disk of our Galaxy is 100,000 light-years in diameter. Using the results from the previous problem, what fraction of the diameter of the Galaxy's disk is the distance for which we can measure accurate parallaxes? 0.0065 The Gaia satellite has greatly improved precision over Hipparcos, measuring parallaxes that are as small as 0.00025 arcseconds. How many times farther away is Gaia be able to measure distances to than Hipparcos?arrow_forwardThe best parallaxes obtained with the Hipparcos satellite have an uncertainty such that we believe measurements as low as 0.005 arc-seconds. What is the farthest distance a star can be to have an accurate distance from Hipparcos?200 parsecs The disk of our Galaxy is 100,000 light-years in diameter. Using the results from the previous problem, what fraction of the diameter of the Galaxy's disk is the distance for which we can measure accurate parallaxes?arrow_forward
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- You can estimate the age of the planetary nebula in image (c) in Figure 22.18. The diameter of the nebula is 600 times the diameter of our own solar system, or about 0.8 light-year. The gas is expanding away from the star at a rate of about 25 mi/s. Considering that distance=velocitytime , calculate how long ago the gas left the star if its speed has been constant the whole time. Make sure you use consistent units for time, speed, and distance. Figure 22.18 Gallery of Planetary Nebulae. This series of beautiful images depicting some intriguing planetary nebulae highlights the capabilities of the Hubble Space Telescope. (a) Perhaps the best known planetary nebula is the Ring Nebula (M57), located about 2000 lightyears away in the constellation of Lyra. The ring is about 1 light-year in diameter, and the central star has a temperature of about 120,000 °C. Careful study of this image has shown scientists that, instead of looking at a spherical shell around this dying star, we may be looking down the barrel of a tube or cone. The blue region shows emission from very hot helium, which is located very close to the star; the red region isolates emission from ionized nitrogen, which is radiated by the coolest gas farthest from the star; and the green region represents oxygen emission, which is produced at intermediate temperatures and is at an intermediate distance from the star. (b) This planetary nebula, M2-9, is an example of a butterfly nebula. The central star (which is part of a binary system) has ejected mass preferentially in two opposite directions. In other images, a disk, perpendicular to the two long streams of gas, can be seen around the two stars in the middle. The stellar outburst that resulted in the expulsion of matter occurred about 1200 years ago. Neutral oxygen is shown in red, once-ionized nitrogen in green, and twice-ionized oxygen in blue. The planetary nebula is about 2100 light-years away in the constellation of Ophiuchus. (c) In this image of the planetary nebula NGC 6751, the blue regions mark the hottest gas, which forms a ring around the central star. The orange and red regions show the locations of cooler gas. The origin of these cool streamers is not known, but their shapes indicate that they are affected by radiation and stellar winds from the hot star at the center. The temperature of the star is about 140,000 °C. The diameter of the nebula is about 600 times larger than the diameter of our solar system. The nebula is about 6500 light-years away in the constellation of Aquila. (d) This image of the planetary nebula NGC 7027 shows several stages of mass loss. The faint blue concentric shells surrounding the central region identify the mass that was shed slowly from the surface of the star when it became a red giant. Somewhat later, the remaining outer layers were ejected but not in a spherically symmetric way. The dense clouds formed by this late ejection produce the bright inner regions. The hot central star can be seen faintly near the center of the nebulosity. NGC 7027 is about 3000 light-years away in the direction of the constellation of Cygnus. (credit a: modification of work by NASA, ESA, and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration; credit b: modification of work by Bruce Balick (University of Washington), Vincent Icke (Leiden University, The Netherlands), Garrelt Mellema (Stockholm University), and NASA; credit c: modification of work by NASA, The Hubble Heritage Team (STScI/AURA); credit d: modification of work by H. Bond (STScI) and NASA)arrow_forwardConsider the following five kinds of objects: open cluster, giant molecular cloud, globular cluster, group of O and B stars, and planetary nebulae. A. Which occur only in spiral arms? B. Which occur only in the parts of the Galaxy other than the spiral arms? C. Which are thought to be very young? D. Which are thought to be very old? E. Which have the hottest stars?arrow_forward
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