Answer:
1. The proportion of the universe's galaxies that can be seen from Earth is approximately 10 per cent (option a).
2. The model of galaxy formation in which sections of gas clouds collapse into small pieces which repeatedly combine into larger pieces under the influence of gravity is called the SZ model or the bottom-up model.
3. Most stars are not destroyed in a galaxy collision because galaxies move too slowly for that kind of damage (option c).
4. It is estimated that the galaxies in the universe have evolved since about 13.8 billion years ago, just after the universe first formed (option b).
Explanation:
1. What we can see of the universe is due to distant stellar objects, whose light has reached us. Current estimates indicate that there may be as many as 2 billion galaxies in the entire universe, many of which are not visible.
Using the "Hubble" space telescope would only allow the observation of 200 billion galaxies and study their composition, which represents about 10 per cent of existing galaxies.
In the future, through the use of more powerful and higher resolution telescopes, it would be possible to observe galaxies that cannot be studied so far.
2. Leonard Searle and Robert Zinn proposed, in 1978, a model for the formation of galaxies, in which small units -globular clusters- associated with each other to progressively form larger components.
Globular clusters are the product of the collapse that occurred before galaxies began to form, and are capable of uniting under the effect of gravity to form larger clusters and thus form the galaxy. The name "bottom up" is due to the fact that small elements form larger ones. Likewise, the name "SZ" results from the initials of the scientists who proposed it.
3. Galaxy collisions are a form of gravity-dependent interaction between galaxies, with one having an effect on the other.
The result of the collision of two galaxies, in general, is the fusion of both, where the larger one is capable of absorbing the smaller one .without this involving the destruction of stars- since the movement of the colliding galaxies is very slow.
4. The formation of galaxies has a calculated time of about 13.8 trillion years, about 500 or 600 million years after the Big Bang.
It is believed that the origin of galaxies reside in the gravitational instability induced primitive fluctuations, leading to the formation of dense units from the scattered gases. This condensation of gases is called clusters or superclusters, and galaxies may have formed from them.
Answer:
1. The universe's galaxies have evolved since what point in time?
2. Which proportion of the universe's galaxies can be seen from Earth?
3. Which was used to create the first image of a black hole?
4. Which of these describes a nebula?
5. Why are most stars not destroyed in a galaxy collision?
6. What do supernova remnant and planetary nebulae have in common? Select the three correct answers.
7. Which of the following is an accurate description of cosmic microwave background (CMB) radiation? Select the two correct answers.
8. Select the correct answers from the list.
The model of galaxy formation in which sections of gas clouds collapse into small pieces which repeatedly combine into larger pieces under the influence of gravity is called the ____ model or the ____ model.
9. Drag and drop the words into the correct locations. Answers may be used once, more than once, or not at all.
Galaxies can be grouped by the age of the stars they tend to contain, with ____ galaxies having the youngest stars and ____ galaxies having the oldest stars.
10. Which event triggers the start of black hole formation?
Explanation:
1. 13.8 billion years ago, right after the universe first formed
2. far less than 1 percent
3. radio waves from matter at the edge of the black hole
4. cloud of gas and dust
5. Galaxies are mostly empty space.
6. They emit non-visible radiation.
They are composed of matter from dying stars.
They contribute matter to interstellar space.
7. CMB is uniformly distributed and of a uniform temperature across the universe.
CMB is remnant radiation from the Big Bang.
8. inside-out / bottom-up
9. irregular / elliptical
10. A massive star depletes its stores of hydrogen and helium
