Top Document: [sci.astro] Solar System (Astronomy Frequently Asked Questions) (5/9) Previous Document: E.05 When will the Sun die? How? Next Document: E.07 Could the Sun explode? See reader questions & answers on this topic! - Help others by sharing your knowledge A couple of possibilities exist. Prior to forming a planetary nebula, a low-mass star (i.e., one with a mass similar to that of the Sun) forms a red giant. Planets close to the star are engulfed in the expanding star, spiral inside it, and are destroyed. In our own solar system, Mercury and Venus are doomed. As the star expands to form a red giant, it also starts losing mass. All stars lose mass. For instance, the Sun is losing mass. However, at the rate at which the Sun is currently losing mass, it would take over 1 trillion years (i.e., 100 times longer than the age of the Universe) for the Sun to disappear. When a star enters the red giant phase, the rate at which it loses mass can accelerate. The mass of a star determines how far a planet orbits from it. Thus, as the Sun loses mass, the orbits of the other planets will expand. The orbit of Mars will almost certainly expand faster than the Sun does, thus Mars will probably not suffer the same fate as Mercury and Venus. It is currently an open question as to whether the Earth will survive or be engulfed. The orbits of planets farther out (Jupiter, Saturn, Uranus, Neptune, and Pluto) will also expand. However, they will not expand by much (less than double in size), so they will remain in orbit about the Sun forever, even after it has collapsed to form a white dwarf. (Any planets around a high-mass star would be less lucky. A high-mass star loses a large fraction of its mass quickly in a massive explosion known as a supernova. So much mass is lost that the planets are no longer bound to the star, and they go flying off into space.) As for the material in the planetary nebula, it will have little impact on the planets themselves. The outer layers of a red giant are extremely tenuous; by terrestrial standards they are a fairly decent vacuum! User Contributions:Comment about this article, ask questions, or add new information about this topic:Top Document: [sci.astro] Solar System (Astronomy Frequently Asked Questions) (5/9) Previous Document: E.05 When will the Sun die? How? Next Document: E.07 Could the Sun explode? Part0 - Part1 - Part2 - Part3 - Part4 - Part5 - Part6 - Part7 - Part8 - Single Page [ Usenet FAQs | Web FAQs | Documents | RFC Index ] Send corrections/additions to the FAQ Maintainer: jlazio@patriot.net
Last Update March 27 2014 @ 02:11 PM
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with stars, then every direction you looked would eventually end on
the surface of a star, and the whole sky would be as bright as the
surface of the Sun.
Why would anyone assume this? Certainly, we have directions where we look that are dark because something that does not emit light (is not a star) is between us and the light. A close example is in our own solar system. When we look at the Sun (a star) during a solar eclipse the Moon blocks the light. When we look at the inner planets of our solar system (Mercury and Venus) as they pass between us and the Sun, do we not get the same effect, i.e. in the direction of the planet we see no light from the Sun? Those planets simply look like dark spots on the Sun.
Olbers' paradox seems to assume that only stars exist in the universe, but what about the planets? Aren't there more planets than stars, thus more obstructions to light than sources of light?
What may be more interesting is why can we see certain stars seemingly continuously. Are there no planets or other obstructions between them and us? Or is the twinkle in stars just caused by the movement of obstructions across the path of light between the stars and us? I was always told the twinkle defines a star while the steady light reflected by our planets defines a planet. Is that because the planets of our solar system don't have the obstructions between Earth and them to cause a twinkle effect?
9-14-2024 KP