A quasar is a. a massive and luminous galaxy b. a star that emits an unusual amount of radio waves c. a bright galactic nucleus powered by a black hole
Scientists first discovered quasars in a. 1913 b. 1931 c. 1961
Most quasars are a. billions of light years away b. close to the Milky Way Galaxy c. almost as old as the universe
Discussion/essay questions
What do you think the purpose of studying space is? Why do humans want to understand the universe?
Transcript
A quasar is a celestial object that emits enough radiation to glow brighter than a galaxy. The energy that a quasar emits comes from a supermassive black hole at its centre. When scientists first observed quasars in 1961, they thought they were stars, or star-like objects. The name “quasar” is an abbreviation for “quasi-stellar radio source”, because the first observed quasars looked like stars that emitted lots of radio waves. Scientists now know that quasars are the nuclei of young galaxies. Even though quasars are very bright, most of them are billions of light years away, which means that observing them can provide information about the state of the universe in the distant past. The oldest discovered quasar formed nearly 13 billion years ago, at the very beginning of the universe’s life.
The ozone layer absorbs a. visible light b. ultraviolet radiation c. debris from space
Ozone is made up of a. bonded oxygen atoms b. bonded oxygen and chlorine atoms c. bonded oxygen and carbon atoms
The “hole” in the ozone layer is above a. Australia b. North America c. Antarctica
Discussion/essay questions
The quick action taken in 1987 prevented a global disaster. Do you think the world will be able to prevent climate change the same way?
Transcript
The ozone layer is a layer of gas in the Earth’s atmosphere that absorbs ultraviolet radiation from the Sun. The molecules that make up ozone gas are made of three bonded oxygen atoms. Ozone forms when photons break up molecules of oxygen gas. The ozone layer protects humans and animals from the harmful effects of UV radiation, including cancers. However, in the 1980s, scientists discovered a dangerously thin area in the ozone layer above Antarctica. This is commonly known as the “ozone hole”. Artificial emissions of chlorine gases had destroyed many of the ozone molecules in the atmosphere. In 1987, a global agreement known as the Montreal Protocol banned the use of certain chemicals in order to protect the ozone layer. Since then, the ozone hole has been shrinking.
On April 26, 1986, the nuclear reactor of the Chernobyl Power Plant in Ukraine . The explosion occurred early in the morning, while plant were performing a maintenance check. They had turned off a control system that was keeping the reactor stable. The initial explosion killed two of the workers, and 28 other workers died of radiation sickness in the months after the . The explosion also caused residents of a nearby town called Pripyat to be exposed to radiation. Because of this, the residents were forced to evacuate and find new places to live. In order to more deaths from radiation exposure, the of what was then the Soviet Union created an exclusion zone around the Chernobyl plant. Although the zone is now safe for tourists to visit, scientists believe that the most contaminated areas will not be habitable for over 20,000 years.
Comprehension questions
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Discussion/essay questions
Nuclear power is a controversial topic. Many people are afraid of the potential dangers that nuclear power plants could cause. Chernobyl is a good example of this. However, nuclear power is a useful source of energy that doesn’t release carbon dioxide. How do you feel about nuclear power? Is it too dangerous, or are the benefits are more important than the risks?
Transcript
On April 26, 1986, the nuclear reactor of the Chernobyl Power Plant in Ukraine exploded. The explosion occurred early in the morning, while plant workers were performing a maintenance check. They had turned off a control system that was keeping the reactor stable. The initial explosion killed two of the workers, and 28 other workers died of radiation sickness in the months after the disaster. The explosion also caused residents of a nearby town called Pripyat to be exposed to radiation. Because of this, the residents were forced to evacuate and find new places to live. In order to prevent more deaths from radiation exposure, the government of what was then the Soviet Union created an exclusion zone around the Chernobyl plant. Although the zone is now safe for tourists to visit, scientists believe that the most contaminated areas will not be habitable for over 20,000 years.
