- Where in the Galaxy is the solar system located? a. in the nucleus, b. in the halo, c. in a spiral arm, d. between two spiral arms, e. in the central bulge
Our solar system is located in one of the two major spiral arms of the disk-shaped Milky Way Galaxy. It is not located in the center or nucleus of Galaxy because the supermassive black hole Sagittarius A*, because of its tremendous gravitational force, make it possible for clusters to remain intact. In the halo of a galaxy, there are mostly spherical distribution of globular clusters, dark matters, and isolated stars. If between the two spiral arms, it is tantamount to saying that our Galaxy is at its nucleus. At the central bulge, it is made mainly of gas, dust, and old stars. However, our Sun is not that old as compared to those at the bulge. Thus, we are left with an answer that our solar system is in one of the Milky Way Galay’s spiral arms.
- What evidence indicates that a supermassive black hole is located at the center of our Galaxy?
The extraordinary activity that occurs in our Galaxy’s nucleus (known as Sagittarius A) is an evidence of the presence of a supermassive black hole. The said black hole holds the stars and gas tightly while they are in rapid rotation around the center of Milky Way Galaxy. Only supermassive black hole can have very strong gravitational forces to make the orbits of these galactic bodies even at a very fast rate.
Astronomers used Kepler’s third law and found out that the gravitational pull needed to keep the galactic stars and gas to remain in its interstellar region is 4 x 106 M. Moreover, there is also very long burst of X rays that was noticed at the center of our Galaxy, thus, implying that a supermassive black hole is responsible for the stars and gas to remain in place.
- Spiral density waves are directly responsible for which of the following? a. flocculent spirals, b. grand-design spirals, c. supernovae, d. the collisions between galaxies, e. galactic cannibalism (See answer on Chapter 18)
(Spiral density waves are spiral-shaped pressure waves that orbits the disks of spiral galaxies. They fit the velocity field of the thin, well-defined and graceful spiral arms of grand-design spiral galaxies. Hence, only spiral density waves are directly responsible for them. Unlike flocculent spiral galaxies, they are poorly demarcated, fuzzy, and broad types. Supernovae are simply the results of stellar explosions which make them similar to intergalactic collisions and even galactic cannibalism or absorption of a smaller to a larger galaxy.)
- Some galaxies in the Local Group exhibit blue-shifted spectral lines. Why are these blue shifts not violations of the Hubble law?
Some galaxies in the Local Group that exhibit blueshifted spectral lines have a more predominating gravitational force over those under Hubble’s Law; thus, no violation is made. Andromeda and Milky Way galaxies, not to mention the other remaining clusters, exert very powerful intergalactic gravitational interactions because they have the first two largest/massive galaxies in the Local Group.
- Suppose you suspected a certain object in the sky to be a quasar. What sort of observations would you perform to confirm your hypothesis?
- Which force in nature is believed to have formed second? a. gravity, b. electromagnetic force, c. weak force, d. strong force, e. all formed at the same time
Gravity, one of the four fundamental forces of nature, is generally defined as the attraction between two bodies with mass or the force of attraction that pulls objects together. Electromagnetic force, the second natural force, is the force in electromagnetic fields where attraction or repulsion occurs between/among electrically/magnetically charged objects. Weak force, the third force, is the interaction between/among decaying/transmutation of lepton and hadrons (as in the emissions and absorptions of neutrinos and anti-neutrinos).
Many physicists believe that the four fundamental forces of nature are related from one another. It is also thought that they all emanated from single force early in the birth of the universe. Logically, what was thought of as separate or distinct entities, such as electricity and magnetism, are related. Thanks to the works of Oersted, Maxwell, Faraday, and others. What has come to be known today as the theory that link together the four fundamental forces is popularly known as the grand unified theory.]
- Explain the difference between a Doppler redshift and a cosmological redshift.
A Doppler redshift refers to an emitting object’s relative velocity when the red spectral wavelengths / lightwaves were emitted as compared to when they are received. On the other hand, cosmological redshift refers to spacetime expansion that “increase[s] the separation between large groups of galaxies” . Any change in the wavelength of light/radiation is caused by the relative motion between the observer on earth and the source along the line of sight. In other words, in Doppler redshift, the frequency of radiation is stretched and recedes from the object that emitted it (i.e., rest frame of the emitting body).
In a cosmological redshift, the light frequency is stretched as space expands. In particular, the Doppler redshift is applicable for nearby objects moving away from an observer from earth whereas a cosmological or gravitational redshift, according to the Einstein’s general theory of relativity, is not due mainly on the moving away of celestial bodies of the elasticity of spacetime.
- Assuming that the universe will expand forever, what will eventually become of the microwave background radiation?
The cosmic microwave background radiation (CMBR) or 3-degree background radiation will cool up to approximately absolute zero, hence, becoming undetectable. As the cooling up continued, the wavelength had continuously stretched as well. Hence, the spectrum’s peak will also then move continuously in the radio region up to the extent that it goes to the long radio wavelength waveband.
As already mentioned, CMBR will also continue to be harder and much harder to determine, notice or observe after billion of years. At present, it is still not relatively difficult to detect the CMB and know more about the universe we live in.
- Which stellar spectral type is most likely to have a planet on which advanced life exists? a. O, b. B, c. A, d. G, e. M
(G-typed stellar spectral type, such as our Sun, is most likely to have a hospitable planet on which advanced life may exist. Our Sun has longevity of 10 billion years. It is also fairly luminous, which would make the existence of life possible. On the other hand, O, B, and A stars are much hotter than our Sun. They also have shorter lifespan. In like manner, M stars have smaller zone for life. They are also flare or too hot stellar bodies and tend to live longer. In recap, only G stars may probably support life.)
Comins, N. F. and W. J. Kaufmann. Discovering the Universe. New York: W. H. Freeman, 2011. Web.