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3.3 Newton’s Universal Law of Gravitation. By the end of this section, you will be able to: Newton’s laws of motion show that objects at rest will stay at rest and those in motion will continue moving uniformly in a straight line unless acted upon by a force. Thus, it is the straight line that defines the most natural state of motion.
- Adapted by Jean Creighton
- 2019
Feb 2, 2016 · 3. Gravitationally, there is little immediate effect on earth on a daily basis, though over very long periods of time, stars that pass near enough to the sun could disrupt the orbits of Oort cloud objects and send them towards the sun (and earth or other planets in our Solar System).
- Stellar Evolution
- The Fate of Medium-Sized Stars
- The Fate of Massive Stars
A star is born, lives, and dies, much like everything else in nature. Using observations of stars in all phases of their lives, astronomers have constructed a lifecycle that all stars appear to go through. The fate and life of a star depends primarily on it's mass. All stars begin their lives from the collapse of material in a giant molecular cloud...
When a medium-sized star (up to about 7 times the mass of the Sun) reaches the red giant phase of its life, the core will have enough heat and pressure to cause helium to fuse into carbon, giving the core a brief reprieve from its collapse. Once the helium in the core is gone, the star will shed most of its mass, forming a cloud of material called ...
A red giant star with more than 7 times the mass of the Sun is fated for a more spectacular ending. These high-mass stars go through some of the same steps as the medium-mass stars. First, the outer layers swell out into a giant star, but even bigger, forming a red supergiant. Next, the core starts to shrink, becoming very hot and dense. Then, fusi...
Stars form in large clouds of gas and dust called molecular clouds. Molecular clouds range from 1,000 to 10 million times the mass of the Sun and can span as much as hundreds of light-years. Molecular clouds are cold which causes gas to clump, creating high-density pockets. Some of these clumps can collide with each other or collect more matter ...
For the most massive stars, neutrons from fusion bombard atoms in the star to make yet more elements, including technetium, a rapidly-decaying element that doesn’t exist naturally on Earth. The more stable atoms from the dying star appear in the spectrum of its light, and are shed into interstellar space as the star dies.
After a supernova, some stars leave behind a super dense neutron star, while the heaviest stars leave a black hole. Based on our understanding of stellar evolution, the Sun will start to run out of core hydrogen in about 5 billion years. The Sun will expand, engulfing several of the inner planets, including Earth.
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Objects like apples at the surface of Earth, at a distance of one Earth-radius from the center of Earth, are observed to accelerate downward at 9.8 meters per second per second (9.8 m/s 2) (9.8 m/s 2). It is this force of gravity on the surface of Earth that gives us our sense of weight.
