In another tutorial, I had you research NGC 936 using Simbad where we found that the redshift of that galaxy is z=0.004096 (redshift is denoted using the lowercase letter z). The amount of shift was not constant and further research showed that the amount of redshift correlated to distance (the redshift actually indicates that the object being observed is moving away from us however, we are also moving and so we can calculate how fast an object is moving away from us and from that calculate the distance the light from the object traveled to get to us). When astronomers observed objects like stars or galaxies, they analyzed the light coming and found the colors tended to be towards the red end of the color spectrum. What Is Redshift?Īs you just learned, longer wavelengths of light are toward the red end of the spectrum of light. If the star is moving away from you, the wavelength of the light would become longer and so be shifted toward the red end of the spectrum of light. Based on the second diagram in this article, shorter wavelengths are shifted toward the violet side of the spectrum of light. If the star is moving toward you, like the ambulance in the first image of this article, the wavelength of light would become shorter because the star and the light it is emitting is moving toward you. You could use a spectrometer, a device that measures the wavelength of light, to determine the color of the light coming from the star. You could look at the star and see the light coming from it. Instead of the ambulance in the preceding scenario, imagine that it is a star and that it is not moving either toward or away from you. Longer wavelengths are toward the red end of the spectrum of light, and shorter wavelengths are toward the violet end of the spectrum of light. Light changes color as its wavelength changes, as shown in the following diagram: When we hear a higher-pitched sound, the wavelength of the sound is shorter and when we hear a lower-pitched sound, its wavelength is longer. Like sound, light also behaves as a wave. As the ambulance passes and moves away from you, the frequency of the sound becomes lower because the ambulance and the sound waves it is producing are moving away from you. As the ambulance moves toward you, its frequency is higher because both the ambulance and sound waves are moving towards you. The preceding figure showed how the Doppler effect works when the source of the sound is moving. Applied to cosmic sources of electromagnetic radiation, it has become one of the most important observational tools of modern astronomy. This motion-induced change in the frequency is known as the Doppler Effect, named after Christian Doppler, the 19th century Austrian physicist who first explained it. Most of us have had the experience of hearing the pitch of a siren change from a high shrill (high-frequency, short wavelength) to a low blare (low frequency, long wavelength) as the ambulance, fire truck, or police car approaches and recedes: But what is redshift and how does it indicate distance?īefore you understand redshift, you need to understand the Doppler Effect. I do mention in that post that you can convert a redshift value to a distance. But with millions of objects visible in the sky there’s not always a Wikipedia page and so you are left to research the object on your own.Ī search on Simbad can yield a lot of good information about an object and I discuss the basic use of Simbad here: Understanding Simbad. When researching an object to observe, or when you want to find out more about an object, there’s often a Wikipedia page about it which gives you a lot of good information about it.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |