Tag: in the world of stars

Questions Related to in the world of stars

Stars are believed to originate

physics in the world of stars evolution and end stages of stars life cycle of stars stars

  1. in clouds composed largely of hydrogen gas.

  2. when black holes eject excess matter and energy.

  3. when a supernova explode.

  4. when a cloud of helium starts to collapse and breaks into constituent protons (hydrogen atoms).

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Correct Option: A

A protostar is a developing star not yet hot enough to engage in the process of:

physics in the world of stars evolution and end stages of stars life cycle of stars stars

  1. nuclear fusion

  2. nuclear fission

  3. atomic transmission

  4. atomic emission

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Correct Option: A
Explanation:

An object is considered a protostar for as long as material is still falling inward. For our Sun, and stars of the same mass, the protostar phase would have ended after approximately 100,000 years. After this, the protostar stops growing and the disk of material surrounding it is destroyed by radiation.


If the protostar was unsuccessful in acquiring enough mass, a brown dwarf will come into shape. These substellar objects that are unable to sustain hydrogen fusion reactions in their cores, due to their insufficient mass

The gaseous body that continues to form, now appears as a large red object called a:

physics in the world of stars evolution and end stages of stars life cycle of stars stars

  1. protostar

  2. red dwarf

  3. red star port

  4. red giant

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Correct Option: A

What does the forming star become when the outward pressure equals the inward force of gravity?

physics in the world of stars evolution and end stages of stars life cycle of stars stars

  1. stable main-sequence star

  2. unstable secondary white dwarf

  3. unstable main-sequence star

  4. stable secondary red giant

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Correct Option: A
Explanation:

Since the forces balance, it forms a stable main sequence star

When the core of a protostar reaches 10 million degrees Kelvin, the pressure is so great that the nuclear fusion of which gas begins?

physics in the world of stars evolution and end stages of stars life cycle of stars stars

  1. hydroxide

  2. hydrogen

  3. heliogen

  4. hydrogate

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Correct Option: B
Explanation:

A star's composition is mostly made of gases of which hydrogen and helium forms the most largest component of it. Hydrogen being the lightest element will get fused to helium

After the initial contraction and when the temperature rises high enough, energy is radiated from the surface in the form of:

physics in the world of stars evolution and end stages of stars life cycle of stars stars

  1. short-wavelength red light

  2. short-wavelength blue light

  3. long-wavelength red light

  4. long-wavelength orange light

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Correct Option: C

What is the range of star masses for high-mass stars? 

physics in the world of stars evolution and end stages of stars life cycle of stars stars

  1. between 500 and about 1,000 solar masses

  2. between 200 and about 500 solar masses

  3. between 8 and about 100 solar masses

  4. between 2 and about 10 solar masses

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Correct Option: C
Explanation:

Range of star masses for high-mass stars varies from about $8$ to $200$ solar masses.

Answer is $C$.

The raw material for the formation of protostar is

physics in the world of stars evolution and end stages of stars life cycle of stars stars

  1. Coal

  2. Helium

  3. Hydrogen

  4. Uranium

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Correct Option: A

The distance of a galaxy from the earth is of the order of $10^{25}$ m. The time taken by light to reach the earth from the galaxy is

physics constellations and galaxies light year evolution and end stages of stars in the world of stars

  1. $3 \times 10^{14}$ s

  2. $3 \times 10^{16}$ s

  3. $3 \times 10^{18}$ s

  4. $3\times10^{20}$ s

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Correct Option: B
Explanation:

Speed of light, c = 3 x 10$^8$ m s$^{-1}$
Time taken by light to reach the earth from the galaxy is
$\displaystyle t = \frac {10^{25}m}{3\times 10^8m\,s^{-1}}\,=\,3\times 10^{16}s$

The $6563 A^0 H _\alpha$ line emitted by hydrogen in a star is found to be red-shifted by $15 A^0$. The speed with which the star is receding from the earth is

physics constellations and galaxies light year evolution and end stages of stars in the world of stars

  1. $3.2 \times 10^5m s^{-1}$

  2. $6.87 \times 10^5m s^{-1}$

  3. $2 \times 10^5m s^{-1}$

  4. $12.74 \times 10^5m s^{-1}$

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Correct Option: B
Explanation:

Wavelength of $H _\alpha$ line, 
$\lambda=6563A^o$
$=6563\times10^{-10}$


Redshift observed in star $(\acute{\lambda-\lambda})=15A^o=15\times 10^{-10}$

Let the velocity of the star with which it is receding away from the earth be v.
Red shift relation, $\acute{\lambda}-\lambda$=$\dfrac{v}{c}\lambda$

$=\dfrac{c}{\lambda}\times (\acute{\lambda}-\lambda)$

$=\dfrac{3\times 10^8\times 15\times 10^{-10}}{6563\times 10^{-10}}$
$=6.87 \times 10^5m s^{-1}$