A two-arm spiral density wave is moving through the Galactic disk. At the 8-kpc radius of the Sun's orbit around the Galactic center, the wave's speed is 120 km/s, and the Galactic rotation speed is 220 km/s. How many times has the Sun passed through a spiral arm since the Sun formed 4.6 billion years ago?

A two-arm spiral density wave is moving through the Galactic disk. At the 8-kpc radius of the Sun's orbit around the Galactic center, the wave's speed is 120 km/s, and the Galactic rotation speed is 220 km/s. How many times has the Sun passed through a spiral arm since the Sun formed 4.6 billion years ago?

Stars and Galaxies (MindTap Course List)

10th Edition

ISBN:9781337399944

Author:Michael A. Seeds

Publisher:Michael A. Seeds

Chapter15: The Milky Way Galaxy

Section: Chapter Questions

Problem 3P

See similar textbooks

Similar questions

The mass of the interstellar medium is determined by a balance between sources (which add mass) and sinks (which remove it). Make a table listing the major sources and sinks, and briefly explain each one.
A molecular cloud is about 1000 times denser than the average of the interstellar medium. Let’s compare this difference in densities to something more familiar. Air has a density of about 1 kg/m3, so something 1000 times denser than air would have a density of about 1000 kg/m3. How does this compare to the typical density of water? Of granite? (You can find figures for these densities on the internet.) Is the density difference between a molecular cloud and the interstellar medium larger or smaller than the density difference between air and water or granite?
Consider 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?
If the Sun were a member of the cluster NGC 2264, would it be on the main sequence yet? Why or why not?
The Sun orbits the center of the Galaxy in 225 million years at a distance of 26,000 light-years. Given that a3=(M1+M2)P2 , where a is the semimajor axis and P is the orbital period, what is the mass of the Galaxy within the Sun’s orbit?
The very first “image" of a black hole, at the centre of galaxy M87, was recently taken by the Event Horizon Telescope (EHT). More accurately, EHT imaged radio emission from the disc of gas that orbits the black hole with a lack of emission from the centre being attributed to the black hole. This image was only possible because EHT is not a single radio telescope, but is in fact a network of telescopes from around the world that take advantage of something known as interferometry. Interferometry is a method for combining the light from multiple telescopes, which results in an image that could have been taken by a telescope that has a diameter equal to the distance between the telescopes referred to as the "“baseline"-rather than the size of each individual telescope. EHT in particular combines observations from several Very Long Baseline Interferometry (VLBI) stations in order to achieve a high angular resolution. (a) Given that the "baseline" of EHT is effectively the diameter of the…
Figure 2 shows the "rotation curve" of NGC 2742. It plots the “radial velocity (V)" (how fast material is moving either toward or away from us) that is measured for objects at different distances (R = radius") from the center of the galaxy. The center of the galaxy is at 0 kpc (kiloparsecs) with a speed of 9 km/sec away from us. (These velocities have been corrected for the observed tilt of the galaxy and represent true orbital velocities of the stars and gas.) 200 100 U4779 -100 As you can see, one side of the galaxy is moving with a negative velocity (spinning toward us), while the other side has a positive velocity (spinning away from us). Using Newton's gravity equation, we will be able to determine the gravitational mass of the entire galaxy and how the mass varies versus distance from the galaxy's center. -200 -8 8 -4 Radius (kpc) Read the following text carefully and follow the instructions: Select five radii spaced evenly from 0-10 kpc across the galaxy. Your selections should…
The very first "image" of a black hole, at the centre of galaxy M87, was recently taken by the Event Horizon Telescope (EHT). More accurately, EHT imaged radio emission from the disc of gas that orbits the black hole with a lack of emission from the centre being attributed to the black hole. This image was only possible because EHT is not a single radio telescope, but is in fact a network of telescopes from around the world that take advantage of something known as interferometry. Interferometry is a method for combining the light from multiple telescopes, which results in an image that could have been taken by a telescope that has a diameter equal to the distance between the telescopes-referred to as the “baseline"-rather than the size of each individual telescope. EHT in particular combines observations from several Very Long Baseline Interferometry (VLBI) stations in order to achieve a high angular resolution. (a) Given that the "baseline" of EHT is effectively the diameter of the…
You observe a star orbiting the massive object at the galactic center at a speed of 1090 km/s in a circular orbit with a radius of 18 light-days. Calculate the mass of the object the star is orbiting. Enter in solar masses Hint: The orbital velocity equation is v=sqrt(G M / R). Also note that the orbital radius is in light DAYS.
If a standard passenger aircraft can fly at 0.32 km/s (716 mph), how long (in yr) would it take to reach the sun? ______ yr How long (In yr) would it take to reach the galactic center? (Note: 1 pc = 3.1 x 10^13 km. The radius of the suns orbit around the galactic center is approximately 8,300 pc.) ______ yr
A given star orbits the center of its galaxy at an average speed of v_star, at a distance of r_star from the center. The galaxy has 2 spiral arms, and the arms themselves orbit slower than the star -- at the same radius, they orbit at a speed of v_arm (in the same direction as the star). The galaxy's age is t_gal. In the history of this galaxy, how many times did this star cross through a spiral arm? Values: v_star = 200 km/s, r_star = 9 kpc, v_arms = 46 km/s, t_gal = 4 Gyr
A galaxy's rotation curve is a measure of the orbital speed of stars as a function of distance from the galaxy's centre. The fact that rotation curves are primarily flat at large galactocen- tric distances (vrot(r) ~ constant) is the most common example of why astronomer's believe dark matter exists. Let's work out why! Assuming that each star in a given galaxy has a circular orbit, we know that the accelera- tion due to gravity felt by each star is due to the mass enclosed within its orbital radius r and equal to v?/r. Here, ve is the circular orbit velocity of the star. (a) Show that the expected relationship between ve and r due to the stellar halo (p(r) xr-3.5) does not produce a flat rotation curve. (b) Show that a p(r) ∞ r¯² density profile successfully produces a flat ro- tation curve and must therefore be the general profile that dark matter follows in our galaxy.