Our universe started with a bang and has been expanding ever since, the space between galaxies increasing with time. The data received declared that the universe wasn't slowing down at all, as was previously thought, rather it was speeding up as though something were propelling it, driving its expansion faster and faster.
Hubble has thoroughly studied stars. The closest star to our Earth is the Sun. It is considered typical of middle-aged stars, formed from a collapsed cloud of gas and dust. Stars are born in clouds of gas and dust. One such stellar nursery is the Orion Nebula, an enormous cloud of gas and dust many light-years across. Turbulence from deep .
within these clouds creates high density regions called knots. These knots contain sufficient mass that the gas and dust can begin to collapse from gravitational attraction. As it collapses, pressure from gravity causes the material at the center to heat up, creating a protostar. One day, this core becomes hot enough to ignite fusion and a star is born. Not all of the material in the collapsing cloud ends up as part of a star- the remaining dust can become planets, asteroids or comets ... or it may remain as dust. The chemical makeup of stars, revealed through spectroscopy, depends on the material in which they originate. In the early universe, stars were formed from matter that lacked most elements except for hydrogen and helium. The other chemical elements have been and still are being created in the interior of stars through nuclear fusion processes. That new material is eventually recycled into subsequent generations of stars and planets. The groupings of stars that form together can vary from a few stars to many hundreds or thousands. The stars in each cluster have a variety of masses. The most massive stars are rare, while the least massive stars are the most numerous. Hubble has probed star clusters of all sizes and uses spectroscopy to determine the detailed chemistry in star cluster members. By taking precise observations of star cluster members, scientists using Hubble can determine their luminosities and temperatures. When their nuclear fuel is exhausted, the most massive stars explode in a spectacular fashion, called a supernova, leaving behind neutron stars, black holes or nothing at all.
Question 1: What evidence does the passage provide to support the idea that the universe is expanding?
Answer: The passage states that the space between galaxies is increasing with time, indicating that the universe is expanding. Additionally, it mentions that data received showed the universe is speeding up in its expansion, contrary to previous beliefs.
Question 2: How does the passage describe the formation of stars from clouds of gas and dust?
Answer: Stars are described as being born in clouds of gas and dust, with high-density regions called knots forming within these clouds. The material in these knots collapses due to gravitational attraction, eventually heating up to create a protostar. Fusion ignites within the core, leading to the birth of a star.
Question 3: What role does spectroscopy play in studying the chemical makeup of stars?
Answer: Spectroscopy is used to reveal the chemical makeup of stars by analyzing the light they emit. The passage explains that the chemical makeup of stars depends on the material from which they originate, and spectroscopy helps identify the elements present in stars.
Question 4: How do stars contribute to the creation of chemical elements in the universe?
Answer: Stars create chemical elements through nuclear fusion processes that occur in their interiors. These elements are then released into space through stellar processes like supernova explosions, contributing to the chemical composition of subsequent generations of stars and planets.
Question 5: What is the significance of star clusters in the study of astronomy?
Answer: Star clusters provide valuable insights into stellar evolution and chemistry. They vary in size and contain stars with a range of masses. By studying star clusters, astronomers can determine the luminosities, temperatures, and chemical compositions of their members, helping to unravel the mysteries of stellar life cycles.
Question 6: What happens to the most massive stars when their nuclear fuel is exhausted, according to the passage?
Answer: When the nuclear fuel of the most massive stars is exhausted, they explode in a spectacular fashion known as a supernova. This process can leave behind neutron stars, black holes, or nothing at all, depending on the mass of the star.
