21st Century Astronomy
6th Edition
ISBN: 9780393428063
Author: Kay
Publisher: NORTON
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Chapter 17, Problem 27QP
To determine
The way in which astronomers can estimate the age of a star cluster by taking a looking at its H-R diagram.
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Chapter 17 Solutions
21st Century Astronomy
Ch. 17.1 - Prob. 17.1CYUCh. 17.2 - Prob. 17.2CYUCh. 17.3 - Prob. 17.3CYUCh. 17.4 - Prob. 17.4CYUCh. 17 - Prob. 1QPCh. 17 - Prob. 2QPCh. 17 - Prob. 3QPCh. 17 - Prob. 4QPCh. 17 - Prob. 5QPCh. 17 - Prob. 6QP
Ch. 17 - Prob. 7QPCh. 17 - Prob. 8QPCh. 17 - Prob. 9QPCh. 17 - Prob. 10QPCh. 17 - Prob. 11QPCh. 17 - Prob. 12QPCh. 17 - Prob. 13QPCh. 17 - Prob. 14QPCh. 17 - Prob. 15QPCh. 17 - Prob. 16QPCh. 17 - Prob. 17QPCh. 17 - Prob. 18QPCh. 17 - Prob. 19QPCh. 17 - Prob. 20QPCh. 17 - Prob. 21QPCh. 17 - Prob. 22QPCh. 17 - Prob. 23QPCh. 17 - Prob. 24QPCh. 17 - Prob. 25QPCh. 17 - Prob. 26QPCh. 17 - Prob. 27QPCh. 17 - Prob. 28QPCh. 17 - Prob. 29QPCh. 17 - Prob. 30QPCh. 17 - Prob. 31QPCh. 17 - Prob. 32QPCh. 17 - Prob. 33QPCh. 17 - Prob. 34QPCh. 17 - Prob. 35QPCh. 17 - Prob. 36QPCh. 17 - Prob. 37QPCh. 17 - Prob. 38QPCh. 17 - Prob. 39QPCh. 17 - Prob. 40QPCh. 17 - Prob. 41QPCh. 17 - Prob. 42QPCh. 17 - Prob. 43QPCh. 17 - Prob. 44QPCh. 17 - Prob. 45QP
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- Explain how an HR diagram of the stars in a cluster can be used to determine the age of the cluster.arrow_forwardCalculate the total number density ( ntot ) and the density ( ρ ) at a depth in a star composed of pure hydrogen where T = 9500 K and 35 % of the atoms are ionized (assume UI = 2). What percentage of hydrogen atoms are in the energy level n = 2?arrow_forward= A star population is composed of stars with masses in the range between 1M and 150M. The initial mass function is = 0 (M/M)-2.3, where o (Mo). The luminosity of a star = (M/M) 3.3. Calculate the percentage of the total luminosity of the stars in the population which is produced by stars with mass between 120M and 150M. scales with its mass as L/Larrow_forward
- The flux received at the Earth from Supernova 1885 was 3.0182 x 10 10 W/m². The luminosity of the supernova is 6 x 10° Lo (or 6 x 10° solar luminosities). What is the distance to the supernova in parsecs? Take 1 pc = 3.0857 x 1016 m and Lo= 3.828 x 1026 w. d = pcarrow_forwardThe star HD 93250 in the Carina Nebula is a bright O-type star. It has a reported apparent magnitude in the V band of mV = 7.41 and V band absolute magnitude of MV = −6.14. Using these values calculate the distance to HD 93250 in parsec. The distance to HD 93250 has been measured by other means as 2350 pc. Compare your calculated value of the distance with the measured value, and give a possible explanation for any difference. Calculate the value of the interstellar extinction in the V band AV that would account for the difference in the distances. The parameter E(B − V ) = AB − AV , where AB and AV are the extinctions in the B and V bands, is often used to characterize interstellar extinction. For the star HD 93250 the value E(B − V ) = 0.48 has been measured. Given the above value of E(B − V ) for HD 93250, calculate the extinction in the B band, and explain why the parameter E(B − V ) is often called the “reddening.” The B band apparent magnitude of HD 93250 is mB = 8.12. Calculate…arrow_forwardObservations show that stellar luminosity, L, and mass, M, are related by L x M3.5 for main sequence stars. Obtain an expression that relates the main sequence life time and the mass of a star. You should assume that the luminosity is constant throughout a star's main sequence life time, and that the amount of mass converted into energy by a star while it is on the main sequence is given by AM main sequence life time of a 20 Solar mass star given that the Sun is expected to spend 1010 years on the main sequence. Comment on the significance of your answer. fM, where f is a constant. Estimate thearrow_forward
- Question 41 .Suppose you are looking at H-R diagrams of two similar star clusters. The most luminous main sequence stars in the Porcini cluster are much more luminous than the most luminous main sequence stars in the Morel cluster. What can you conclude? O the Porcini cluster is younger than the Morel cluster O the Porcini cluster is farther away than the Morel cluster O the Porcini cluster is lower in metallicity than the Morel cluster O the Porcini cluster is larger in diameter than the Morel clusterarrow_forwardAn O8 V star has an apparent visual magnitude of +5. Use the method of spectroscopic parallax to estimate the distance to the star (in pc). (Hints: Refer to one of the H–R diagrams in the chapter, and use the magnitude–distance formula, d = 10(mV − MV + 5)/5 where d is the distance in parsecs, mV and MV are the apparent and absolute visual magnitude respectively.)arrow_forwardUsing the HR diagram what is the approximate range of relative luminosities covered for a main sequence star at 10 000 K?arrow_forward
- H II regions can exist only if there is a nearby star hot enough to ionize hydrogen. Hydrogen is ionized only by radiation with wavelengths shorter than 91.2 nm. What is the temperature of a star that emits its maximum energy at 91.2 nm? (Use Wien’s law from Radiation and Spectra.) Based on this result, what are the spectral types of those stars likely to provide enough energy to produce H II regions?arrow_forwardYou can use the equation in Exercise 22.34 to estimate the approximate ages of the clusters in Figure 22.10, Figure 22.12, and Figure 22.13. Use the information in the figures to determine the luminosity of the most massive star still on the main sequence. Now use the data in Table 18.3 to estimate the mass of this star. Then calculate the age of the cluster. This method is similar to the procedure used by astronomers to obtain the ages of clusters, except that they use actual data and model calculations rather than simply making estimates from a drawing. How do your ages compare with the ages in the text? Figure 22.10 NGC 2264 HR Diagram. Compare this HR diagram to that in Figure 22.8; although the points scatter a bit more here, the theoretical and observational diagrams are remarkably, and satisfyingly, similar. Figure 22.12 Cluster M41. (a) Cluster M41 is older than NGC 2264 (see Figure 22.10) and contains several red giants. Some of its more massive stars are no longer close to the zero-age main sequence (red line). (b) This ground-based photograph shows the open cluster M41. Note that it contains several orange-color stars. These are stars that have exhausted hydrogen in their centers, and have swelled up to become red giants. (credit b: modification of work by NOAO/AURA/NSF) Figure 22.13 HR Diagram for an Older Cluster. We see the HR diagram for a hypothetical older cluster at an age of 4.24 billion years. Note that most of the stars on the upper part of the main sequence have turned off toward the red-giant region. And the most massive stars in the cluster have already died and are no longer on the diagram. Characteristics of Main-Sequence Starsarrow_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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