If the Sun were 9 times more heavier than it is, while the Earth were still 1 A.U. (Astronomical Unit) away from it, the

Earth year would be:

• a. 1/3 year;• b. 9 years;• c. 3 years;• d. none of the above

How is the distance to a star related to its parallax?

A. Distance is proportional to parallax

B. Distance is inversely proportional to parallax

C. Distance is proportional to parallax squared

D. Distance is inversely proportional to parallax squared

Sun spots are dark

• A. only in comparison with the surrounding material

• B. because they contain heavy elements• C. because magnetic fields are dark• D. because magnetic fields absorb light

Sun spots are cooler than surrounding gas

• A. as they emit more efficiently than surrounding gas• B. as magnetic field impede thermal conduction• C. as nuclear reactions are suppressed by in sun spots• D. as magnetic field undergoes reconnection there

What is the difference between brightness andluminosity?

a. There are different names for the same thing

b. Brightness is how we see a star, luminosity is how muchlight it emits

c. Luminosity is the measure of the size of the star, brightnessis the measure the age the star

d. None of the above

The limit on the resolution of a large groundbased telescope is due to

• a. diffraction• b. refraction• c. the focal length• d. atmospheric seeing

Arrays of radio telescopes can produce much better resolution than single-dish telescopes because they

work on the principle of

• a. reflection• b. refraction• c. diffraction• d. interference

The biggest problem for infrared observations is

• a. smog• b. carbon dioxide• c. water wapor• d. light polution

Solar activity reflected by the number of sunspots is believed to influence the climate on Earth as

• A. when Sun has more sunspots it radiates less heat• B. sunspots inhibit nuclear reactions in the Sun• C. the number of energetic particles interacting

with Earth atmosphere changes • D. sunspots affect the Earth orbit

Sun’s magnetism is due to

• A. iron core of the Sun• B. heating of Corona by energetic particles generated

during Solar Flares• C. generation of magnetic fields via fluid+magnetic

field motions• D. neutrino flows coming from the Sun’s core

Standard candle is

• A. Astronomical instrument to measure spectra• B. Source of emission with known luminosity• C. Source of neutrino generation• D. Focus of laser beam used to correct for turbulence

in atmosphere

O stars show weak hydrogen absorption lines as

• A. they do not contain hydrogen• B. their magnetic fields are too strong• C. they are hot• D. they are very cold

Jets are launched from young stars

A. Due to nuclear blasts in the starB. Due to magnetic forces acting on accreting materialC. Due to radiation forces from the hot nuclear burning star core

D. Due to gravitational pull of the star on the jet material

Our Sun will eventually

A. Become white dwarf

B. Explode as a supernova

C. Become a protostar

D. Become a black hole

The spectral type of a star is most directly related to its

a. Absolute magnitude

b. Surface temperature

c. Size or radius

d. Luminocity

Which two vital parameters are used to describe the systematics of a group of stars in the HR diagram?

• a. Mass and weight• b. Luminocity and radius• c. Surface temperature and mass• d. Luminocity and surface temperature

CNO cycle happens

A. In protostars as they are not hot enoughB. In the stars similar to our Sun

C. In high mass stars with very hot coreD. In fully convective low mass stars

Why is it that the majority of stars in the sky are in the main sequence phase of their lives?

• a. Because this is the only phase that is common to all stars

• b. because most stars die at the end of main sequence phase

• c. because most stars in the scy are created at about the same time

• d. because this is the longest lasting phase in each star life

When a star leaves the main sequence and expands towards the red giant region, what is happening

inside the star?

• a. Hydrogen burning is taking place in a spherical shell just outside the core; the core itself is almost pure helium.

• b. Helium is being converted into carbon and oxygen in the core.

• c. Helium burning is taking place in a spherical shell just outside the core.

• d. hydrogen burning is taking place in a spherical shell, while the core has not yet started thermonuclear reactions and still mostly hydrogen.

A Cepheid variable is

• a. a low mas red giant that varies in size and brightness in an irregular way

• b. a big planet• c. a high-mass giant or supergiant star that

pulsates regularly in size and brightness• d. a variable emission nebula near a young star

One of the reasons for pulsars to experience glitches is

A. Nuclear burning in the neutron starB. Nuclear burning in the white dwarf

C. Cracking of the neutron star crust as it gets more round

D. Cracking of the neutron star crust as it gets more oblate

Exploding white dwarfs (supernovae type Ia) provide good standard candle as

A. Their light curve (luminosity versus time) is the same

B. Their magnetic fields are well known

D. Burning of hydrogen in white dwarfs has been well studied theoretically

C. They produce neutron stars with known properties

Pulsars produce observed pulses as

• A. Their surface is subject to pulsation• B. Their magnetic fields are changing rapidly as

reconnection events take place• C. The cone of their radiation encompasses the

observer as the neutron star rotates• D. Accretion of material onto pulsar’s surface is

periodic

Thermal radiation emitted by isolated Black Holes can be understood in terms of

A. Nuclear burning induced by the black holeB. Expansion of the Universe locally near the black hole

C. Effect of the gravitational field on virtual electron-positron pairs arising due to the quantum

mechanical energy uncertainty

D. Stopping of time in the vicinity of the black hole as the black hole travels through space-time

Reflection nebulae are bluish as

A. Dust emits more blue light rather than red light

B. Dust scatters more blue light compared to red light

D. Magnetic fields block most of the red light

C. Hydrogen gets ionized by ambient stars

21 cm emission is due to

• A. Flipping of spin of an electron in the magnetic field of a proton

• B. Electrostatic interaction of an electron and a proton• C. Emission of virtual electron-positron pairs by a

proton• D. Gravitational interaction of an electron and a

proton

As a star converts most of its hydrogen in its core into helium, the star gets

a. less luminous and smallerb. hotter and fainterc. more luminous and biggerd. less luminous and red

A hydrogen burning shell is created near the helium core because

a. helium diffuses into the shellb. hydrogen diffuses into the corec. core is hot and densed. both a. and b.

If we observe a star cluster which has all the starsof main sequence present, this cluster is

a. oldb. youngc. was born as a result of supernova explosiond. both a. and c.

Gravitational lensing of light by clusters of galaxies

A. Indicates the existence of dark matter

B. Proves that the Universe has large positive curvature

D. Indicates the existence of dark energy in the Universe

C. Proves the expansion of the Universe

Solar Flares happen due toa. annihilation of oppositely directed magnetic fields

b. nuclear reactions on the Sun surfacec. explosions of chemicals on the Sun surface

d. comets hitting the Sun surface

A solid body (e.g. a brick of metallic iron of size 1 cm) does not emita distinct emission line spectrum of its constituent atoms asa. as there are no laws for emission for solid bodiesb. quantum mechanics is not applicable to any solid body starting from thesize of0.1 millimeterc. atoms interact strongly in the body and do not emit independentlyd. the line emission is absorbed by the atmosphere between the solid and theobserver

Magnetic pressure of magnetic field in Sun spots is compensated bya. high gaseous pressure of the surrounding materialb. nuclear reactions in the surrounding materialc. magnetic reconnection in Solar Coronad. all of the above

What causes the core of a star to contract during the main sequencephase of the star’s life?

a. Helium has a larger atomic weight than hydrogen and exerts a strongergravitational pull on the core.

b. Convection in the outer layers carries energy out of the core moreefficiently as the star ages

c. A black hole gets created at the stellar cored. The conversion of hydrogen into helium reduces the number of

particles in the core