Supernovas are the most powerful and spectacular outbursts known in nature. What is called a Type II supernova is due to the collapse of a massive star, at least eight times as massive as the sun, that has used up its main nuclear fuel and produced a nickel-iron core. When this core can no longer support the pressure of the star’s outer layer, it collapses to form a neutron star of immense density. Over 2,500 million tons of neutron star packed into a matchbox. Its temperature is around 100,000 million degrees centigrade.

   Multitudes of neutrons are produced in the collapsed star, which pass directly through the star into space, and this release of neutrons causes the core to respond with a shock wave that moves outward.

   When it meets the material that is falling inward, the result is a catastrophic explosion. Sometimes most of the star’s material is blown away, leaving only a small, incredibly dense remnant that may be a neutron star or, in extreme cases, a black hole.

   A supernova is often more than 500 million times as luminous as the sun. A supernova remnant (SNR) may be detectable as a pulsar, an example of which is the Crab Nebula, known to be a remnant of the supernova observed in the year 1054. The 1987 supernova in the Large Cloud of Magellan had a low peak luminosity by supernova standards, only about 250 million times that of the sun. As its brightest the supernova shone as a star between magnitudes 2 and 3, even though it was 170,000 light-years away.

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions

What is the main topic of the passage?

Câu hỏi liên quan

• The word “perishable” in paragraph 1 is closest in meaning to ............

• The author uses the word “But” in paragraph 4 to ______.

• We can see from paragraph 5 that after his father’s death, Mantle ______.

ZUNIA12

• When is the most famous football game held annually?

• What does the passage mainly discuss?

• The word “they” in line 17 refers to ...........

• What does the passage mainly discuss?

   

• Why did the author write the passage?

• Which of the following is NOT true about algae?

• This article is about ................

• The word “sophisticated” in line 12 could best be replaced by?

• What does the writer’s mother look like?

• What does the author probably mean by using the expression “children interrupt their education to go to school” (lines 2-3) ?

• The phrase “in season” in line 1 refers to ________ .

• According to the passage, Porter’s Father was ___________.

• What do the Hindu people think about marriage?

• The word “ integral” in line 13 is closest in meaning to .....

•  In line 3, the words pays heed to are closest in meaning to ………………...

• The phrase ‘suck out’ in paragraph 2 is closest in meaning to which of the following?

• The Daylight Saving Time Energy Act of 1973 was responsible for ..