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The Origins of the Solar System
As we know, the Solar System contains over 178 objects that revolve around the central star or Sun. We can see some of these objects from Earth with the unaided eye or an Earth-based telescope. Still, the majority have only been detected by developing instruments such as the Hubble Space Telescope or unmanned probes such as Voyager. These operate outside Earth’s atmosphere and collect more information about the composition and behavior of objects in the Solar System, which has enabled researchers to hypothesize about their origins.
It is generally thought that a cloud of interstellar gas and dust is known as a ‘nebula’ disturbed by some major event in space – possibly a supernova – about 5 billion years ago and collapsed under its own gravity. This cloud rotated rapidly as it got smaller and denser and heated up to several thousand degrees, causing some of its elements to vaporize into a gas. The cloud center became so hot that it eventually exploded into a star, with the cooler gases flowing around it. In time, the gases condensed into dust, metals, and various kinds of ice in the cold outer reaches of space. These solid particles collided with each other to form larger objects or asteroids as they continued to spin around the central star.
As these asteroids increased in size, their gravity pulled in all the material in their immediate surroundings, and the largest of these became planets. The very different composition of the inner planets (Mercury, Venus, Earth, and Mars) and the outer planets (Jupiter, Saturn, Neptune, and Uranus) leads astronomers to believe that their distances from the Sun caused them to develop at different rates and in different ways. According to the most widely-held opinions, the planets closest to the Sun where all the ice particles were vaporized because of the incredible heat (the Sun is 15.6 million degrees Kelvin at the core), were formed mostly of rock, silicates, and metals with high melting points as these particles collided and were pulled together by gravity. These inner planets have thin atmospheres or none at all, and few, if any satellites, which would show that most of the material was either pulled into their own gravity or burnt away in the heat of the Sun.
The inner and outer planets are separated by an asteroid belt comprising a material that was probably prevented from coalescing into a world by interfering with Jupiter’s immense gravity. Beyond this area, as more dust and ice particles escaped destruction by the Sun, four larger planets formed over a longer period of time in a far colder environment as the material was thrown out from the center by the spinning star’s centrifugal force. About a million years after the original nebula’s cooling, the Sun emitted a stream of charge, protons, and electrons known as the solar wind, which blew the remaining gases outwards, to be sucked in by the outer planets which became gas giants. These planets attracted many objects into their vast gravity fields, some of which are big enough to be termed ‘satellites’ and countless smaller fragments that form rings around the planets.
The discovery of more objects in the Solar System in recent times has led to the need for further classification. Far beyond the outer planets lies Pluto, which was originally considered the ninth planet but has since been found to be a binary system of two dwarf planets, the other being Charon. Pluto’s origins may be in the recently discovered Kuiper Belt, the source of many of the comets that travel through the Solar System; this theory is based on Pluto’s rock/ice composition to that of a comet. At one time, also thought to be a moon of Neptune, Pluto/Charon was reclassified in 2006 as one of three dwarf planets discovered so far: Eris and Ceres.
All scientific knowledge is only as good as the ability of scientists to collect and understand the evidence, and as new advances are made in astronomy, the present theories as to the extent of the Solar System may be disproved, as in the case of Pluto. At this time, the above account represents the consensus of current opinions on the matter.
It is generally thought that a cloud of interstellar gas and dust is known as a ‘nebula’ disturbed by some major event in space – possibly a supernova – about 5 billion years ago and collapsed under its own gravity. This cloud rotated rapidly as it got smaller and denser and heated up to several thousand degrees, causing some of its elements to vaporize into a gas. The cloud center became so hot that it eventually exploded into a star, with the cooler gases flowing around it. In time, the gases condensed into dust, metals, and various kinds of ice in the cold outer reaches of space. These solid particles collided with each other to form larger objects or asteroids as they continued to spin around the central star.
As these asteroids increased in size, their gravity pulled in all the material in their immediate surroundings, and the largest of these became planets. The very different composition of the inner planets (Mercury, Venus, Earth, and Mars) and the outer planets (Jupiter, Saturn, Neptune, and Uranus) leads astronomers to believe that their distances from the Sun caused them to develop at different rates and in different ways. According to the most widely-held opinions, the planets closest to the Sun where all the ice particles were vaporized because of the incredible heat (the Sun is 15.6 million degrees Kelvin at the core), were formed mostly of rock, silicates, and metals with high melting points as these particles collided and were pulled together by gravity. These inner planets have thin atmospheres or none at all, and few, if any satellites, which would show that most of the material was either pulled into their own gravity or burnt away in the heat of the Sun.
The inner and outer planets are separated by an asteroid belt comprising a material that was probably prevented from coalescing into a world by interfering with Jupiter’s immense gravity. Beyond this area, as more dust and ice particles escaped destruction by the Sun, four larger planets formed over a longer period of time in a far colder environment as the material was thrown out from the center by the spinning star’s centrifugal force. About a million years after the original nebula’s cooling, the Sun emitted a stream of charge, protons, and electrons known as the solar wind, which blew the remaining gases outwards, to be sucked in by the outer planets which became gas giants. These planets attracted many objects into their vast gravity fields, some of which are big enough to be termed ‘satellites’ and countless smaller fragments that form rings around the planets.
The discovery of more objects in the Solar System in recent times has led to the need for further classification. Far beyond the outer planets lies Pluto, which was originally considered the ninth planet but has since been found to be a binary system of two dwarf planets, the other being Charon. Pluto’s origins may be in the recently discovered Kuiper Belt, the source of many of the comets that travel through the Solar System; this theory is based on Pluto’s rock/ice composition to that of a comet. At one time, also thought to be a moon of Neptune, Pluto/Charon was reclassified in 2006 as one of three dwarf planets discovered so far: Eris and Ceres.
All scientific knowledge is only as good as the ability of scientists to collect and understand the evidence, and as new advances are made in astronomy, the present theories as to the extent of the Solar System may be disproved, as in the case of Pluto. At this time, the above account represents the consensus of current opinions on the matter.
1. In paragraph 1, what does the author say about the role of the Hubble Space Telescope?
A. It is too defective for our scientists to come up with definite answers to the origin of the universe
B. Scientists discovered billions of new planets by combining measurements from the Hubble Space Telescope with Voyager measurements
C. It solved the age of the universe and measured the age of what may be the youngest galaxy ever seen in the universe
D. It has helped unveil many mysteries or queries about our universe
2. The word disturbed in the passage is closest in meaning to:
A. broken
B. bothered
C. attracted
D. imported
3. The word their in the passage is closest in meaning to:
A. materials
B. surroundings
C. planets
D. asteroids
4. Which of the following best expresses the essential information in the italicized sentence in the passage?
A. Planets formed from gases and dust particles after comets collided with the Sun
B. According to scientists, the manners in which planets developed was wholly dependent on their distance from Jupiter’s rings
C. The dissimilar make-up of the planets closest to the Sun and those farthest from the Sun suggests that the distance from the Sun affected their formation
D. Scientists believe the Sun evolved from the composition of several older planets in the solar systen
5. According to paragraph 4, the inner and outer planets are seperated by what?
A. an asteroid belt
B. a star
C. comets
D. a moon
6. According to the passage, all of the following are true about our solar system EXCEPT:
A. Planets nearest the Sun were formed mostly of rock
B. There continues to be new discoveries as technology improves
C. Colliding asteroids eventually formed planets
D. Most of the comets in the solar system can be seen with the naked eye during an annual solar eclipse
7. Why does the author mention Pluto in paragraph 5?
A. To discuss Pluto’s rock/ice composition
B. To introduce the concept of planet formation
C. To show that new discoveries are always occuring
D. To introduce the distinction between planets and dwarf planets
8. The word vaporised in the passage is the closest in meaning to:
A. turn into liquid
B. turn into gas
C. turn into a solid
D. remained the same
9. It can be inferred from the passage that the planets _____
A. broke off from the rapidly spinning moon
B. collided more frequently, to spur the formation and growth of protoplanets
C. were initially asteroids
D. were formed by the collisions of massive objects circling a black hole in eccentric orbits
10. According to the passage, what were the universe’s origins?
A. A nebula collapsed under its gravity
B. A black hole exploded and merged to create the universe
C. A super being wished it into existence
D. The Sun collapsed it on itself
