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Top Document: [sci.astro] Solar System (Astronomy Frequently Asked Questions) (5/9) Previous Document: E.09 Where can I find pictures and planetary data? Next Document: E.11 Is Pluto a planet? Is Ceres? Is Titan? See reader questions & answers on this topic! - Help others by sharing your knowledge A star is usually defined as a body whose core is hot enough and under enough pressure to fuse light elements into heavier ones with a significant release of energy. The most basic (and easiest, in terms of the temperatures and pressures required) type of fusion involve the fusion of four hydrogen nuclei into one helium-4 nucleus, with a corresponding release of energy (in the form of high-frequency photons). This reaction powers the most stable and long-lived class of stars, the main sequence stars (like our Sun and nearly all of the stars in the Sun's immediate vicinity). Below certain threshold temperatures and pressures, the fusion reaction is not self-sustaining and no longer provides a sufficient release of energy to call said object a star. Theoretical calculations indicate (and direct observations corroborate) that this limit lies somewhere around 0.08 solar masses; a near-star below this limit is called a brown dwarf. By contrast, Jupiter, the largest planet in our solar system, is only 0.001 masses solar. This makes the smallest possible stars roughly 80 times more massive than Jupiter; that is, Jupiter would need something like 80 times more mass to become even one of the smallest and feeblest red dwarfs. Since there is nothing approaching 79 Jupiter masses of hydrogen floating around anywhere in the solar system where it could be added to Jupiter, there is no feasible way that Jupiter could become a star. 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.09 Where can I find pictures and planetary data? Next Document: E.11 Is Pluto a planet? Is Ceres? Is Titan? 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