Tag: the stars

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Questions Related to the stars

Multiple choice physics life cycle of stars evolution and end stages of stars the stars stars

Match the columns

A B
(1) Speed of light (a) 4.3 light years away from earth
(2) Light year                (b) 300,000 km/s
(3) Sun (c) Nearest star
(4) Alpha Centauri (d) distance travelled by light in one year
(e) 18 light minutes away from the Earth

  1. 1-d 2-d, 3-a, 4-e

  2. 1-a, 2-b, 3-c, 4-e

  3. 1-d, 2-b, 3-e, 4-c

  4. 1-b, 2-d, 3-c, 4-a
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The speed of light is 300,000 km/s.
Light year is the distance travelled by light in one year.
Sun is the nearest star from Earth.
Alpha Centauri is 4.3 light years away from Earth.

Multiple choice physics life cycle of stars evolution and end stages of stars the stars stars

The observed wavelength of light coming from a distant galaxy is found to be increased by $0.5\%$ as compared with that coming from a terrestrial source. The galaxy is.

  1. Stationary with respect t to the earth

  2. Approching the earth with velocity of light

  3. Receding from the earth with velocity of light

  4. Receding from the earth with a velocity equal to $1.5\times 10^{6}m/s$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$\displaystyle\frac{\Delta \lambda}{\lambda}=\frac{v}{c}$
Now, $\Delta\lambda=\displaystyle\frac{0.5}{100} \lambda$
$\Rightarrow \displaystyle\frac{\Delta\lambda}{\lambda}=\frac{0.5}{100}$
$\therefore v=\displaystyle\frac{0.5}{100}\times c=\frac{0.5}{100}\times 3\times 10^8$
$=1.5\times 10^6m/s$
increase in $\lambda$ indicates that the star is receding.

Multiple choice physics life cycle of stars evolution and end stages of stars the stars stars

$1$ parsec equals to:

  1. $3.26$ light years

  2. $3.1 \times 10^{13}\ km$

  3. $1.92 \times 10^{13}\ miles$

  4. all of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$1$ parsec = $3.26$ light years

$= 3.6 \times 9.46 \times 10^{12}\ km$
$\approx 3.1 \times 10^{13}\ km$
$=\dfrac{3.1 \times 10^{13}}{1.6}\ miles$

             
 $\approx 1.92 \times 10^{13}\ miles$

Multiple choice physics life cycle of stars evolution and end stages of stars the stars stars

The evidence for the rotation of stars comes mainly from the.

  1. Stark effect

  2. Photoelectric effect

  3. Doppler effect

  4. Zeeman effect
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The Doppler effect causes shifts in the spectral lines of a rotating star. As one side of the star rotates toward the observer and the other away, the light is blueshifted and redshifted respectively, causing spectral line broadening.

Multiple choice physics life cycle of stars evolution and end stages of stars the stars stars

Which of the following statements about degeneracy pressure is not true?

  1. Degeneracy pressure varies with the temperature of the star.

  2. Degeneracy pressure can halt gravitational contraction of a star even when no fusion is occurring in the core.

  3. Degeneracy pressure keeps any protostar less than 0.08 solar mass from becoming a true, hydrogen-fusing star.

  4. Degeneracy pressure supports white dwarfs against gravity.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Degeneracy pressure is the pressure which prevent the neutron star from becoming the Black hole.

Degeneracy pressure does not varies with the temperature of the star.

Multiple choice physics life cycle of stars evolution and end stages of stars the stars stars

What is happening inside a star while it expands into a subgiant?

  1. It is fusing hydrogen into helium in the core.

  2. It is fusing hydrogen into helium in a shell outside the core.

  3. It is fusing helium into carbon in the core.

  4. It is fusing helium into carbon in a shell outside the core.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Fusion reactions take place and all hydrogen gets fuses to helium, thereby depleting hydrogen completely

Multiple choice physics life cycle of stars evolution and end stages of stars the stars stars

Which two energy sources can help a star maintain its internal thermal pressure? 

  1. nuclear fusion and gravitational contraction

  2. nuclear fission and gravitational contraction

  3. chemical reactions and gravitational contraction

  4. nuclear fusion and chemical reactions
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Fusion reaction happen on star   such as sun where hydrogen combine to form $He$ a fusion reaction releasing energy and gravitational contraction occur due to very high gravitational pull.

Multiple choice physics life cycle of stars evolution and end stages of stars the stars stars

What happens when a star exhausts its core hydrogen supply?

  1. Its core contracts, but its outer layers expand and the star becomes bigger and brighter.

  2. It contracts, becoming smaller and dimmer.

  3. It contracts, becoming hotter and brighter.

  4. It expands, becoming bigger but dimmer.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Nuclear fusion powers a star for most of its life. Initially the energy is generated by the fusion of hydrogen atoms at the core of the main-sequence star. Later, as the preponderance of atoms at the core becomes helium, stars like the Sun begin to fuse hydrogen along a spherical shell surrounding the core. This process causes the star to gradually grow in size, passing through the subgiant stage until it reaches the red giant phase.

When they reach this phase, hydrogen in them almost becomes depleted off and they become brighter and hotter and becomes low-mass white dwarfs

Multiple choice physics life cycle of stars evolution and end stages of stars the stars stars

At approximately what temperature can helium fusion occur? 

  1. 100,000 K

  2. 1 million K

  3. 100 million K

  4. None of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Helium fusion (the triple-alpha process) requires significantly higher temperatures than hydrogen fusion to overcome the increased electrostatic repulsion of helium nuclei. This typically occurs at temperatures around 100 million Kelvin.