On February 24, 1987, Chilean astronomers detected an extremely bright light, which they identified as a supernova (the explosion of a massive star) occurring 168 thousand light years from Earth. It began to dim over the next few ______ although they are extremely powerful, supernovas are short-lived phenomena.21 Mark For ReviewWhich choice completes the text so that it conforms to the conventions of Standard English?A) weeks. However,B) weeks, however,C) weeks; however,D) weeks, however;

Imagine you are observing light from a distant galaxy 100 million light years away from you. By analysis of the starlight received, you are able to tell that the image we see is of a 10 million year old star. You are also able to predict that the star will have a total lifetime of 50 million years, at which point it will end in a catastrophic supernova.How much longer will it be before we receive the light from the supernova event?

Ethan observes a star which brightness changes with time on Earth. Upon closer inspection, he does not observe any stars nearby. Which of the following is an accurate term to describe the star?

What made supernova 1987A so useful?Group of answer choicesThe Hubble Space Telescope was available for high resolution images.As it was in the Large Magellanic Cloud, we knew it was 170,000 ly distant.Its parent star had been studied previously.It was spotted while still on the rise, and its light curve is well established.All of the above are true.

For all we've learned about the sun, our home star remains shrouded in mystery. Now, after seven years of relative calm, the sun is set to become more ______________-and a fleet of sun-gazing spacecraft are ready to watch as it awakens. Those spacecraft are offering scientists an unprecedented chance to study our stormy star and the ways it can affect our cosmic neighbourhood.1Mark for ReviewABCWhich choice completes the text with the most logical and precise word or phrase?AaccessibleBtemperamentalCmysteriousDtransient

Type the missing letters to complete the text below.William Herschel's Theory of StarsIn 1785, William Herschel theorized about the life cycle of stars, in which a star would exist for a limited amount of time before exploding in a dramatic event called a supernova. He suggested afterwards would into a of from new would . Herschel's theory was confirmed with the discovery of nebulae and the recognition that stars formed from within these interstellar dust clouds.