E.5 Fusion and stars

A star is on the main sequence.

What are the most abundant element(s) in the core of the star and in the outer layer of the star?

A star is on the main sequence.

What are the most abundant element(s) in the core of the star and in the outer layer of the star?

Star X has the same surface temperature as the Sun and a luminosity of ${10}^4{L}_{\odot }$

What is $\frac{\text{radius of X}}{\text{radius of the Sun}}$?

A.  10

B.  10²

C.  10³

D.  10⁴

Star X has the same surface temperature as the Sun and a luminosity of ${10}^4{L}_{\odot }$

What is $\frac{\text{radius of X}}{\text{radius of the Sun}}$?

A.  10

B.  10²

C.  10³

D.  10⁴

Show that the energy released is about 18 MeV.

Show that the energy released is about 18 MeV.

Show that the energy released is about 18 MeV.

A fusion reaction of one nucleus of hydrogen-2 and one nucleus of hydrogen-3 converts 0.019 u to energy. A fission reaction of one nucleus of uranium-235 converts a mass of 0.190 u to energy.

What is the ratio $\frac{\text{specific energy of this fusion of hydrogen}}{\text{specific energy of this fission of uranium}}$?

A.  0.1

B.  0.2

C.  5

D.  10

A fusion reaction of one nucleus of hydrogen-2 and one nucleus of hydrogen-3 converts 0.019 u to energy. A fission reaction of one nucleus of uranium-235 converts a mass of 0.190 u to energy.

What is the ratio $\frac{\text{specific energy of this fusion of hydrogen}}{\text{specific energy of this fission of uranium}}$?

A.  0.1

B.  0.2

C.  5

D.  10

The Hertzsprung–Russell diagram shows two stars, $\text{X}$ and $\text{Y}$.

What is $\frac{\mathrm{radius} \mathrm{of} \mathrm{X}}{\mathrm{radius} \mathrm{of} \mathrm{Y}}$?

A.  $\frac{1}{16}$

B.  $\frac{1}{4}$

C.  4

D.  16

The Hertzsprung–Russell diagram shows two stars, $\text{X}$ and $\text{Y}$.

What is $\frac{\mathrm{radius} \mathrm{of} \mathrm{X}}{\mathrm{radius} \mathrm{of} \mathrm{Y}}$?

A.  $\frac{1}{16}$

B.  $\frac{1}{4}$

C.  4

D.  16

The Hertzsprung–Russell diagram shows two stars, $\text{X}$ and $\text{Y}$.

What is $\frac{\mathrm{radius} \mathrm{of} \mathrm{X}}{\mathrm{radius} \mathrm{of} \mathrm{Y}}$?

A.  $\frac{1}{16}$

B.  $\frac{1}{4}$

C.  4

D.  16

The Hertzsprung–Russell diagram shows two stars, $\text{X}$ and $\text{Y}$.

What is $\frac{\mathrm{radius} \mathrm{of} \mathrm{X}}{\mathrm{radius} \mathrm{of} \mathrm{Y}}$?

A.  $\frac{1}{16}$

B.  $\frac{1}{4}$

C.  4

D.  16

The Hertzsprung–Russell diagram shows two stars, $\text{X}$ and $\text{Y}$.

What is $\frac{\mathrm{radius} \mathrm{of} \mathrm{X}}{\mathrm{radius} \mathrm{of} \mathrm{Y}}$?

A.  $\frac{1}{16}$

B.  $\frac{1}{4}$

C.  4

D.  16

The Hertzsprung–Russell diagram shows two stars, $\text{X}$ and $\text{Y}$.

What is $\frac{\mathrm{radius} \mathrm{of} \mathrm{X}}{\mathrm{radius} \mathrm{of} \mathrm{Y}}$?

A.  $\frac{1}{16}$

B.  $\frac{1}{4}$

C.  4

D.  16

The Hertzsprung–Russell diagram shows two stars, $\text{X}$ and $\text{Y}$.

What is $\frac{\mathrm{radius} \mathrm{of} \mathrm{X}}{\mathrm{radius} \mathrm{of} \mathrm{Y}}$?

A.  $\frac{1}{16}$

B.  $\frac{1}{4}$

C.  4

D.  16

The Hertzsprung–Russell diagram shows two stars, $\text{X}$ and $\text{Y}$.

What is $\frac{\mathrm{radius} \mathrm{of} \mathrm{X}}{\mathrm{radius} \mathrm{of} \mathrm{Y}}$?

A.  $\frac{1}{16}$

B.  $\frac{1}{4}$

C.  4

D.  16

The Hertzsprung–Russell diagram shows two stars, $\text{X}$ and $\text{Y}$.

What is $\frac{\mathrm{radius} \mathrm{of} \mathrm{X}}{\mathrm{radius} \mathrm{of} \mathrm{Y}}$?

A.  $\frac{1}{16}$

B.  $\frac{1}{4}$

C.  4

D.  16

The Hertzsprung–Russell diagram shows two stars, $\text{X}$ and $\text{Y}$.

What is $\frac{\mathrm{radius} \mathrm{of} \mathrm{X}}{\mathrm{radius} \mathrm{of} \mathrm{Y}}$?

A.  $\frac{1}{16}$

B.  $\frac{1}{4}$

C.  4

D.  16

During its evolution, the Sun is likely to be a red giant of surface temperature 3000 K and luminosity 10⁴ L_☉. Later it is likely to be a white dwarf of surface temperature 10 000 K and luminosity 10-4 L_☉. Calculate the $\frac{\text{radius of the Sun as a white dwarf}}{\text{radius of the Sun as a red giant}}$.

During its evolution, the Sun is likely to be a red giant of surface temperature 3000 K and luminosity 10⁴ L_☉. Later it is likely to be a white dwarf of surface temperature 10 000 K and luminosity 10-4 L_☉. Calculate the $\frac{\text{radius of the Sun as a white dwarf}}{\text{radius of the Sun as a red giant}}$.

The astronomical unit ($\mathrm{AU}$) and light year ($\mathrm{ly}$) are convenient measures of distance in astrophysics. Define each unit.

$\mathrm{AU}$:

$\mathrm{ly}$:

The astronomical unit ($\mathrm{AU}$) and light year ($\mathrm{ly}$) are convenient measures of distance in astrophysics. Define each unit.

$\mathrm{AU}$:

$\mathrm{ly}$:

Show that the apparent brightness $b\propto \frac{A{T}^4}{d^2}$, where $d$ is the distance of the object from Earth, $T$ is the surface temperature of the object and $A$ is the surface area of the object.

Show that the apparent brightness $b\propto \frac{A{T}^4}{d^2}$, where $d$ is the distance of the object from Earth, $T$ is the surface temperature of the object and $A$ is the surface area of the object.

Two of the brightest objects in the night sky seen from Earth are the planet Venus and the star Sirius. Explain why the equation $b\propto \frac{A{T}^4}{d^2}$ is applicable to Sirius but not to Venus.

Two of the brightest objects in the night sky seen from Earth are the planet Venus and the star Sirius. Explain why the equation $b\propto \frac{A{T}^4}{d^2}$ is applicable to Sirius but not to Venus.

Carbon (C-12) and hydrogen (H-1) undergo nuclear fusion to form nitrogen.

${}_6{}^{12}\text{C+}{}_1{}^1\text{H →N+}$ photon

What is the number of neutrons and number of nucleons in the nitrogen nuclide?

Carbon (C-12) and hydrogen (H-1) undergo nuclear fusion to form nitrogen.

${}_6{}^{12}\text{C+}{}_1{}^1\text{H →N+}$ photon

What is the number of neutrons and number of nucleons in the nitrogen nuclide?