How can the composition of a star be determined

For instance, there are many different mechanisms by which an object, like a star, can produce light. Each of these mechanisms has a characteristic spectrum. White light what we call visible or optical light can be split up into its constituent colors easily and with a familiar result: the rainbow.

All we have to do is use a slit to focus a narrow beam of the light at a prism. This setup is actually a basic spectrometer. The resultant rainbow is really a continuous spectrum that shows us the different energies of light from red to blue present in visible light. But the electromagnetic spectrum encompasses more than just optical light. It covers all energies of light, extending from low-energy radio waves, to microwaves, to infrared, to optical light, to ultraviolet, to very high-energy X-rays and gamma rays.

Three types of spectra: continuous, emission line and absorption. Each element in the periodic table can appear in gaseous form and will produce a series of bright lines unique to that element. Hydrogen will not look like helium which will not look like carbon which will not look like iron Thus, astronomers can identify what kinds of stuff are in stars from the lines they find in the star's spectrum. This type of study is called spectroscopy. The science of spectroscopy is quite sophisticated.

From spectral lines astronomers can determine not only the element, but the temperature and density of that element in the star. When photographic emulsions came into use, the spectroscope became the spectrograph, in which a photographic film or plate replaces the human eye. During the first half of the 20th century spectrographs were used on telescopes to observe thousands of stars, the intensities of the lines being measured from the blackness of the film or plate.

Most recently photoelectric detectors are used to scan the spectrum in a spectrophotometer. Stellar spectra can also be measured by other techniques. Although the ultraviolet, visual, and infrared parts of a star's spectrum can be measured in this way, other techniques must be used, above the atmosphere, to measure the shorter wavelength spectra of X-ray stars and gamma-ray stars.

Instead of gratings and prisms, various combinations of filters and detectors are used to measure portions of the X-ray and gamma-ray spectra. At the other extreme - that is, very long wavelengths - radio spectra of stars and other radio sources are measured by "tuning" a radio telescope to different frequencies.

A radio telescope - the largest is more than m 1, ft across - is like a giant optical reflector with a radio amplifier at the focus. Radio spectra are much more accurate than optical spectra.

Multiple radio telescopes, placed thousands of kilometers apart, can determine the position of a radio-emitting star as accurately as an optical telescope can, to better than 0. Create a List. List Name Save. Rename this List. Rename this list. Stars have no molten rock in them like the interiors of some of the planets.

The next two things have already been noted elsewhere but they are important enough to state again. Universality of physical laws: The same pattern of hydrogen lines are seen in the in spectra of the Sun, stars, distant galaxies, and quasars active galaxies at very great distances from us. This is a sensitive test of whether or not the laws of physics used in the structure of atoms works everywhere in the universe.

Even slight differences in the rules of quantum mechanics that govern the interactions of the protons, electrons, and neutrons or differences in the strengths of the fundamental forces of natures from that observed on the Earth would produce noticeable changes in the spacing and strength of the spectral lines.

If the subatomic particles had different amount of charge or mass, the pattern of lines would be different than what you see on the Earth. Because the same patterns are seen in the spectra, regardless of where the light comes from, the physics used on Earth must work everywhere else in the universe!