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WorksheetsStellar Classification
Total questions: 12
Worksheet time: 14mins
Harvard Classification Scheme from A to P class stars are based on
Star's temperature
Strength of Balmer lines
Stellar Compositions
Star's Energy
Balmer lines are strongest in which class stars?
O5 class stars
A2 class stars
G2 class stars
M5 class stars
What is the relation between the strength of Balmer lines and classification the classification of OBAFGKM
The coolest star is Hydrogen poor has the strongest Balmer lines
The hottest star is Hydrogen rich, hence the strongest Balmer lines
Balmer lines is lower near the hottest star and steadily increases from O class to A class
Balmer lines is strongest near the hottest star with highest Helium and Metal
Equivalent Width (EW) is useful to characterize the strength of absorption lines. EW is proportional to
The distance of the star
The intensity of the flux density
The length of missing flux
Wavelength of the stars measured
Boltzmann Excitation Equilibrium Equation states the
Ratio of exited atoms to the other energy levels
Ratio of exited ions to the other energy levels
Energy of the atom in exited state
Energy of the ion in exited state
Boltzmann Excitation Equilibrium Equation conclude that
The strength of Balmer lines is proportional to the number of Hydrogen ion in exited state, n=2
The strength of Balmer lines is proportional to the number of Hydrogen atom in exited state, n=2
The strength of Balmer lines is proportional to the temperature of Hydrogen atom populated
The strength of Balmer lines is proportional to the temperature of Hydrogen ions populated
Saha equation tells us that
Strength of Balmer lines in higher temperature where the atoms is ionized
ratio of the number of Hydrogen atom in higher state
to the number of atom in lower state
ratio of the number of ions in higher state
to the number of ions in lower state
Strength of Balmer lines at temperature 10000K where the Hydrogen atoms is completely ionized
This diagram displays the rise and fall of
all non-ground state transitions with temperature. From this diagram we can deduce that
series of optical stellar spectra displays the
systematic change in absorption line strengths
with temperature.
smooth variation along the spectral types indicates minor variations of the chemical composition of stars with temperature.
ionization occurs over a small temperature range. The Hydrogen neutral at 7000 K - 10,000 K.
equivalent width is the amount
of wavelength the amount of
spectrum that would be completely “black”.
Why were there not any hydrogen features in red and cooler stars?
because it is late type and Hydrogen poor
because it is early type and Helium rich
because the Hydrogen atom is in ground state
because the stars are runs out of Hydrogen
Why were very minimum hydrogen features in blue and hottest stars?
because it is early type, hence Hydrogen poor
because all the Hydrogen is almost ionized
because it early type, hence Helium rich
because the Hydrogen is in the ground state
The temperature of the star dependent upon the strength of Balmer lines.
TRUE
FALSE
Very thin absorption line in high luminosity class star in Morgan-Keenan (MK) System is due to
pressure broadening in high mass stars
error in spectral parallax
very low atom Hydrogen in exited state
most of atom Hydrogen is in ionized state, therefore it can absorbs radiation
