It is a result of the space between the Earth and the galaxies expanding. Red-shift and speedĪstronomers see red-shift in virtually all galaxies. The diagram shows part of the emission spectrum of light from a distant galaxy. The lines are moved or shifted towards the red end of the spectrum. The dark lines in the spectra from distant galaxies show an increase in wavelength. When they do this, they see it is different to the light from the Sun. Spectra from distant galaxiesĪstronomers can observe light from distant galaxies. The diagram shows part of the emission spectrum of light from the Sun. Different elements produce different patterns of dark lines. Elements in the star absorb some of the emitted wavelengths, so dark lines are present when the spectrum is analysed. Of course, we will continue to refine our understanding of the processes of the formation of galaxies, the formation of stars, and the origin of the elements using ultraviolet observations of galaxies near the Earth.Light from a star does not contain all the wavelengths of the electromagnetic spectrum.
Redshift galaxy full#
In other words, the full story of the formation of galaxies, for instance, requires a multiwavelength approach. To actually understand the evolution of these processes through cosmic time, we have to look at distant objects: we are studying the physics as noted above, but the light with which we study the physics appears in the red and not in the blue because of the expansion of the Universe. The ultraviolet studies discussed above have laid the ground work and given us the physical insight for the study of the formation of galaxies, the formation of stars, and the origin of the elements. Therefore, the study of the physics behind the creation of ultraviolet radiation and the study of the origin of the elements as one looks back in time depends on having equipment on Earth that senses light from astronomical objects which is actually red, not blue, because it has been redshifted. At the highest redshifts known, ultraviolet light from the source will appear to be infrared light at the Earth.
The wavelength of the radiation has shifted from the ultraviolet to much longer wavelengths during its journey through space from the galaxy to a telescope in space near the Earth. As the Universe expands, all wavelengths stretch, and short wavelength photons appear to have longer wavelengths. As we observe objects at greater distances, say halfway out in the Universe, the ultraviolet radiation produced by the physics I discussed will shift to redder wavelengths because all light in the expanding Universe is redshifted. The light we study to understand the physics of star and galaxy formation, the origin of the elements, and the origin of intergalactic and galactic gas, is ultraviolet at the source. Each galaxy is also labelled with its estimated redshift.Ĭredit: NASA, ESA, R. Not all of the galaxies are observable in the main image. Enhanced fragments of the distant galaxies are displayed in black and white across the top of the image and the location of each of the galaxies is marked in the main image by a box of the same color. The new data reveals a possible population of distant galaxies at redshifts between 9 and 12, including a candidate for the most distant object observed from Earth to date. Hubble Ultra Deep Field 2012: This is an improved version of the Hubble Ultra Deep Field (2004) featuring additional observation time. Wavelengths will be stretched by factors of 2, 4, 6, or even more as objects are further and further away from us. Light from intrinsically hot, blue stars in distant galaxies will look redder than when it left the source. On the other hand, the Universe is expanding and all light from distant objects will be perceived to be redder than when it left the source. If the Universe were not expanding, the same kinds of objects seen very far away from us would still appear to be blue. The stars will be predominantly blue in color. Consider a galaxy with hot stars that is near the Earth.
Another issue is the redshift of distant galaxies and gas.
I already mentioned the need for larger and larger telescopes. You have to ask yourself, “Well, where’s the field going?” That’s something I’m not sure we know. On the Hubble Space Telescope alone there are two instruments that operate in the ultraviolet and perform the experiments I’ve described to you. I think the field has been a major triumph in the sense that we now understand the physics behind the emission of ultraviolet light, and the astrophysical phenomenon in the nearby Universe that can be studied with that light.
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