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What do astronomers use photographic plate for？
A．Decreasing the time it takes to photograph objects.
B．Avoiding using a telescope.
C．Sharpening the color of what they observe.
D．Obtaining images of distant objects.
答案
更多“What do astronomers use photographic plate for？A．Decreasing the time it takes to photograp”相关的问题
第1题
According to the passage, what do people often think about astronomers？
A．They spend most of their time looking through telescopes.
B．They are constantly analyzing data.
C．They often live near observatories.
D．They devote a lot of time to theoretical problems.
第2题
Black Holes
1 Black holes can be best described as a sort of vacuum, sucking up everything in space. Scientists have discovered that black holes come from an explosion of huge stars. Stars that are near death can no longer burn due to loss of fuel, and because its temperature can no longer control the gravitational(重力的) force, hydrogen ends up putting pressure onto the star’s surface until it suddenly explodes then collapses.
2 Black holes come from stars that are made of hydrogen, other gases and a few metals. When these explode it can turn into a stellar-mass(恒星质量) black hole, which can only occur if the star is large enough (should be bigger than the sun) for the explosion to break it into pieces, and the gravity starts to compact every piece into the tiniest particle. Try to see and compare: if a star that’s ten times the size of the sun end up being a black hole that’s no longer than 70 kilometers, then the Earth would become black hole that’s only a fraction of an inch!
3 Objects that get sucked in a black hole will always remain there, never to break free. But remember that black holes can only gobble up(吞噬) objects within a specific distance to it. It’s possible for a large star near the sun to become a black hole, but the sun will continue to stay in place. Orbits(轨道) do not change because the newly formed black hole contains exactly the same amount of mass as when it was a star, only this its mass is totally contracted that it can end up as no bigger than a state.
4 So far, astronomers have figured out that black holes exist because of Albert Einstein’s theory of relativity. In the end, through numerous studies, they have discovered that black holes truly exist. Since black holes trap light and do not give off light, it is not possible to detect black holes via a telescope. But astronomers continue to explore galaxies(银河系), space and the solar system to understand how black holes. It is possible that black holes can exist for millions of years, and later contribute further process in galaxies, which can eventually lead to creation of new entities. Scientists also credit black holes as helpful in learning how galaxies began to form.
A Is there proof that black holes really exist？
B What are different types of black holes？
C How are black holes formed？
D How were black holes named？
E What happened to the objects around a black hole？
F What are black holes made of？
23 Paragraph 1________
第3题
What did eighteenth-century astronomers have in common with astronomers today？
A．They could not explain everything they detected with their instruments.
B．They knew the correct distances of objects they could not identify.
C．Their instruments were not powerful enough to detect spiral nebulae.
D．They argued over the natural brightness of variable stars.
第4题
A．the night sky there is too dark.
B．the once dark areas are also polluted by lights.
C．these areas are not polluted by chemicals.
D．these areas are less developed.
第5题
What is the lecture mainly about？
A．How astronomers found the correct interpretation for a certain observation
B．How astronomers distinguish between two kinds of nebulae
C．Various improvements to the telescope over the last 300 years
D．An old problem in astronomy that remains unsolved
第6题
What could astronomers better estimate once they knew what nebulae really were？
A．The diameter of variable stars
B．The density of cosmic dust
C．The size of the universe
D．The average number of planets in a galaxy
第7题
What is the one reason astronomers make long time exposures？
A．To spend less time at their telescopes.
B．To overcome the problem of weak light.
C．To take more photographs.
D．To photograph astronomical objects without using a telescope.
第8题
A．Study the moons of Jupiter
B．Observe gamma-ray bursters
C．Reject the dust theory of nebulae
D．Prove that galaxies are surprisingly small
第9题
What is the purple of the conversation？
A．To gather information for the student"s astronomy class.
B．To write a research paper about a recent discovery in space.
C．To report findings from an astronomers" conference.
D．To get information for the astronomy club.
第10题
As far as astronomers can determine, the entire universe is built of the same matter. They have no reason to doubt that matter obeys the same laws in every part of the universe. Therefore, it is reasonable to guess that other stars, with their own planets, were born in the same way as our own solar system. What we know of life on earth suggests that life will arise wherever the proper conditions exist.
Life requires the right amount and kind of atmosphere. This eliminates all those planets in the universe that are not about the same size and weight as the earth. A smaller planet would lose its atmosphere, a larger one would hold too much of it.
Life also required a steady supply of heat and light. This eliminates double stars, or stars that flare up suddenly. Only single stars that are steady sources of heat and light like our sun would qualify.
Finally, life could evolve only if the planet is just the right distance from its sun. With a weaker sun than our own, the planet would have to be closer to it. With a stronger sun, it would have to be farther away.
If we suppose that every star in the universe has a family of planets, then how many planets might support life？ First, eliminate those stars that are not like our sun. Next, eliminate most of their planets, they are either too far from or too close to their suns. Then eliminate all those planets which are not the same size and weight as the earth. Finally, remember that the proper conditions do not necessarily mean that life actually does exist on a planet. It may not have begun yet, or it may have already died out.
This process of elimination seems to leave very few planets on which earthlike life might be found. However, even if life could exist on only one planet in a million, there are so many billions of planets that this would still leave a vast number on which life could exist.
Astronomers believe that matter in different parts of the universe ______.
A．has different laws
B．has one common law
C．shares the same laws
D．shares no common law
