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What is believed to be the source of many ultrahigh-energy cosmic rays?
Q18: In 1785, William Herschel proposed that the
Q43: If a person falls as far as
Q85: Which of these stars could be classified
Q128: What is remarkable about the supernova remnant
Q141: How does a gravitational field affect the
Q142: Which of these statements about the capability
Q145: Which nuclear fusion cycle is the next
Q152: The first pulsar was discovered in which
Q197: Main-sequence stars can be divided into those
Q266: At what temperature do nuclear reactions begin