Herschel\'s attempt to map the Milky Way by counting stars led to an inaccurate
ID: 235227 • Letter: H
Question
Herschel's attempt to map the Milky Way by counting stars led to an inaccurate estimate of the Galaxy's size because he was unaware of absorption by interstellar dust. The instability strip is below the main sequence on the H-R diagram. 21 cm radio waves allow us to map the distribution of hydrogen in spiral arms on the opposite side of the Galaxy. The most likely explanation of the high-speed motion of stars and gas near the Galactic center is that the stars and gas are orbiting a supermassive black hole. The longer the period of pulsation for a Cepheid, the more massive and luminous the variable giant star is. Shapley found the globular cluster distribution equally concentrated all along the galactic plane. Most of the mass in the Milky Way lies out beyond the Sun's orbit. The rotation curve for our galaxy shows stars farther out than our Sun moving slower than should be expected. Cepheids are good examples of cataclysmic variable stars. A population II star could have terrestrial planets orbiting it. A pulsar is a type of pulsating variable star.Explanation / Answer
1. True
2.False; Instablity strip is a vertical region in the H-R diagram and it contains many variable stars like RR Lyrae, Cepheid variable etc. It intersects the main sequence in the region of A and F stars and can extend to G and K early bright super giants. It lies above the main sequence.
3. True: 21 cm radio waves are used to determine the motions and locations of gas in spiral arms of the galaxies by virtue of their doppler shift
4. True
5. True: There is direct relationship between pulsation period and the luminosity of cepheid, the longer the pulsion period the more luminous it is. And also the massive stars are more luminious than the small size stars. So we can say that the period of pulsation for a cepheid the more luminious and massive varibale giant star is.
6. False: Shapely in 1917 started studying globular cluster,.The globular cluster of milky way galaxy had strongly asymmetrical distribution.Majority of the stars were found in the galatic core and the other large majority found within the sides of the celestial sky centered on the core.
7. False
8. False: Cataclaclysmic variable stars are those whose luminosity changes rapidly and significantly due to violent outburst processes within the star. Cepeheids are examples of pulsating variables which periodically expand and contract their surface layers due to change in their size, effective temperature and spectral properties.
10. false: population ii star is metal poor stars. whereas population i is metal rich eg sun and population i star are more likely to possess terrestial planets in comparsion to population ii and population iii which are metal depleted because planets were thought to be formed out of accretion of metals.
11. False: pulsar is a type of neutron star or the dead relic of star.