But the spectrum of a star also reveals additional information, such as the star’s radial velocity – that component of its velocity that is directly toward or away from observers on earth. Trace amounts of heavier elements are also present. We know this because we can produce the same kinds of lines in a laboratory on earth by heating various elements to a given temperature, and observing the resulting spectrum.įrom spectroscopy, we know that all observed stars are comprised almost entirely of hydrogen and helium gas – the two lightest elements. They tell us exactly what stars are made of, and also the surface temperature. So, these absorption lines are like an atomic fingerprint. Each element has a specific set of absorption lines for a given temperature range. These are called absorption lines and are due to the energy levels of electrons in the atoms of the outer layers of a star. Careful analysis will reveal thin, dark lines in this spectrum, indicating that certain wavelengths of light are missing or at least greatly suppressed. This device splits the light into its constituent wavelengths (“colors”), directing them to different locations and forming a spectrum – much like a rainbow. The light from a distant star is directed into an instrument called a spectroscope. This type of analysis is called spectroscopy. By separating and analyzing the wavelengths of the incoming light, we can learn a great deal about the source of that light. This is the main reason we are able to know about anything beyond our solar system. Some of the photons (the particles of light) reach earth, and they carry with them some information about their source. Instead, we depend upon God to set up the conditions of the “experiment,” and we must use careful reasoning to interpret the data He has already provided.įortunately, many things in space glow stars and nebulae emit light. In astrophysics, the challenges are even greater because we do not have direct access to distant stars. Indirect methods must be used, and some of these are ingenious. For example, the mass of an electron cannot be measured on a balance the way we would measure the mass of a rock. Physicists often have to devise clever ways to discover scientific information that is not easily accessible in a typical laboratory. And these new discoveries challenge the secular view of origins. But through some careful measurements and ingenious reasoning, there is additional information we can learn about exoplanets. In cases where the planet passes directly in front of its star, we are also able to estimate the size of the planet, its true mass, and therefore its density. In many instances, we know only the orbital period and minimum mass of the planet. Several thousand exoplanets have been discovered. We have been examining the recent discoveries of extrasolar planets – those planets that orbit a star other than the sun.
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