Question

What are WIMPs?

1. Very small, low-mass stars
2. A candidate class of dark matter that only interacts with the gravitational force
3. Stable, massive, sub-atomic particles that interact with the weak & gravitational forces
4. Stable, massive, sub-atomic particles that interact with the strong & gravitational forces E) A candidate class of dark matter that only interacts with the electromagnetic force

[22] In beta-decay of a neutron into a proton ….

1. A down quark decays into an up-quark emitting an electron and an anti-neutrino
2. An up quark decays into a down quark emitting a positron and a neutrino
3. A down quark decays into an up-quark emitting an positron and a neutrino
4. A down quark decays into an up quark emitting a photon
5. A down quark decays into a top quark emitting an electron and an anti-neutrino

[23] What is the main energy generation mechanism in stars on the main-sequence?

1. Nuclear fision of hydrogen into helium
2. Nuclear fusion of hydrogen into helium
3. Release of gravitational potential energy as the star contracts
4. Collapse of the stellar core into a neutron star or black hole
5. Nuclear fusion of helium into heavier elements

[24] Pulsars are:

1. Accreting black holes
2. Spinning white dwarf stars
3. Spinning neutron stars
4. Pulsating neutron stars
5. Spinning giant stars

[25] Which particles likely “froze out” earliest in the history of the universe?

1. Neutrons
2. Quarks
3. Photons
4. WIMPS
5. Electrons

Answer 1

[21] WIMP: Weakly interacting massive particles are hypothetical particles that are one of the proposed candidates for dark matter. WIMP, heavy, electromagnetically neutral subatomic particle that is hypothesized to make up most dark matter and therefore some 22 percent of the universe. These particles are thought to be heavy and slow moving because if the dark matter particles were light and fast moving, they would not have clumped together in the density fluctuations from which galaxies and clusters of galaxies formed. The absence of light from these particles also indicates that they are electromagnetically neutral. These properties give rise to the particles’ common name, weakly interacting massive particles. Because WIMPs may only interact through gravitational and weak forces, they are extremely difficult to detect.

Hence, the correct option is B.

[22] In beta-decay of a neutron converted into a proton, the process creates an electron and an electron antineutrino. The electron and antineutrino fly away from the nucleus, which now has one more proton than it started with. Since an atom gains a proton during beta-minus decay, it changes from one element to another. For example, after undergoing beta-minus decay, an atom of carbon (with 6 protons) becomes an atom of nitrogen (with 7 protons). An neutron, composed of two down quarks and an up quark, decays to a proton composed of a down quark and two up quarks.

Hence, the correct option is A.

[23] The main energy generation mechanism in stars on the main-sequence is Nuclear fusion of hydrogen into helium. Energy is produced in a star’s center, or core, where pressures are enormous and temperatures reach 27 million°F (15 million°C). The proton-proton chain dominates in stars with masses less than or equal to our sun’s. It involves the fusion of two hydrogen nuclei into a helium nucleus. This causes nuclear fusion—atoms of hydrogen are ripped apart and fuse (join) to form helium. These reactions release vast amounts of energy, which makes the star shine.

Hence, the correct option is B.

[24] Pulsars are types of neutron stars;  that spins rapidly and emits radio waves along its magnetic axis.

Hence, the correct option is C.

[25] Protons and Neutrons froze out when the temperature dropped below 1013 K, when the universe was only 0.0001 s old.

Hence, the correct option is A.