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They are the characteristic frequencies of the elements "burning up" in the stars in the galaxy interspersed with absorption lines of other material between these elements and the earth. All these wavelengths will be increased by the red shift which results from the galaxy receding from the earth.
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The spectral lines of elements when observed in distant galaxies show a shift towards?
The red end of the spectrum.
Do action-at-a-distance forces require physical contact between objects?
No. A couple of examples:- . The Cosmic Microwave background, is the residual radiation signature left over from the time of the creation of the Universe from the Big Bang. . The determination, by means of a spectroscope, of the spectral lines indicating the presence of particular elements in a distant star. . You may argue that the traffic microwave radar has its waves impinging on the target vehicle, but most would consider this a non-contact measurement.
What is the Doppler shift as it applies to light from stars?
You've probably heard the old classical description of the Doppler effect; if you're standing still near a train track, you can hear the sound of the moving train shifted to a higher frequency as the train is coming toward you, and as the train passes by, you can hear the sound shift down in pitch. The sound waves are bunched up a bit as the train is coming toward you, and you hear the train at an increased tone; when the train passes by and moves away from you, the sound waves are stretched out so you hear the sound at a lower pitch. By measuring the change in the sound, you can calculate quite accurately how fast the train was moving when it passed by. For stars, we're not listening to a tone; we're measuring the light spectrum, but the principle is the same. We know what the "normal" frequencies in the starlight would be, for a star not moving towards us or away from us. We measure specific spectrum patterns called "absorption lines". We can detect shifts in these patterns. So, we can measure whether the star is coming toward us (spectral lines at higher frequencies than normal) or is headed away from us (spectrum showing lower frequencies than normal). When we measure the light - and the Doppler shift - of other stars in our Galaxy, we see a mix of stars moving toward us, and stars moving away from us. This is perfectly normal. But when we measure the Doppler shift of the light from other galaxies, we see that most of the other galaxies are moving away from us, and that the farther away they are, the faster they are moving! Note: For those who like a bit of extra detail: The change in the light from distant galaxies is not a true Doppler shift. It's similar, but is caused by the expansion if space itself.
What do astronomers use to determine the chemical composition in star?
The light that comes from the star. The light is spread out into its spectrum and the pattern of spectral lines allow the composition (and temperature) to be determined. The temp can also be found by looking at the black body curve for the star (also from spectrum), or, by looking at the color of the star (difference in intensity of the light through two different color filters typically B and V. The light that comes from the star. The light is spread out into its spectrum and the pattern of spectral lines allow the composition (and temperature) to be determined. The temp can also be found by looking at the black body curve for the star (also from spectrum), or, by looking at the color of the star (difference in intensity of the light through two different color filters typically B and V.
How can you identify the elements in other galaxies?
Each element has a characteristic "fingerprint", that can be noticed in the light that comes from a star, or galaxy. When the light is separated into its component, you see a so-called "spectrum"; specific elements have lines at specific position on such a spectrum. This can give at least a qualitative analysis; a quantitive analysis (the exact amounts) is trickier, but it can at least be estimated.
