Question

Predict and interpret the effects of Doppler shift.

Use the inverse square law equation to relate brightness and luminosity.

Use magnitudes to describe brightness and color.

Relate stellar properties and the OBAFGKM classification system.

Read H-R diagrams for stellar temperatures, radii, and luminosities.

Predict the ages of stellar clusters based on their color-magnitude diagrams.

Identify the major steps of stellar evolution by name and on the HR diagram.

Relate supernovae and compact objects to the stars that produce them.

Answer 1

ANS 1: Doppler effect is basically the change in frequency of wave in relation to an observer who is moving relative to the source of wave.It is a phenomenon used in astronomical measurements,radar and modern navigation system.The amount of shift depends on velocity of object in relation to observer,more the velocity,higher will be the shift.It works both  on  light and sound objects,for example when a sound object comes closer to you the frequency of sound waves increases whereas when it moves away that frequency decreases.In astronomy it shows that spectra of stars is not constant ,different stars show different absorption lines at particular frequency.

ANS 2:

ANS3: The magnitude of any celestial body is measured in terms of wavelength and color filters and each wavelength corresponds to a particular color.As the brightness increases the magnitude decreases.If the filter used is blue it is designated by 'B',for yellow green filter which has close senstivity to eye we designate it by'V',that is visual and for ultraviolet we give 'U' symbol ,so it is a UBV sytem for star color.These filters generally transmit light near the wavelength of 360 nm,420 nm and 540 nm.The difference between any two magnitudes like B-V is called color index. Bright stars may have negative magnitude like Sirius which has -1.6 magnitude.

ANS 4: Stellar classification is basically a system of star classification on the basis of spectral properties.The electromagnetic radiation coming from a star is allowed to split on a spectrum exhibiting different colors ,each color has a chemical component associated with it witha line strength that indicates the abundance of that element .Astronomers have devised a method of classification of stars using the letters OBAFGKM,it is a sequence from hottest to coolest.Each letter is subdivided into 10 numeric digits with 0 being hottest and 9 being coldest.Based on absorption,spectral line tell us about the temperature of star.