That the galaxy is moving away from us.
The light from distant galaxies is redshifted. The only reasonable explanation for that is that the galaxies are moving away from us.
Astronomers can watch galaxies that are far away. Since the light takes billions of years to reach us from the farthest known galaxies, they would be watching galaxies in the early Universe. It turns out, from such observations, that the Universe is changing.
The redshift of distant galaxies is believed to be a result of the Doppler effect - in other words, the light is shifted towards lower frequencies ("redshifted") due to the fact that the galaxies move away from us.
The expansion of the Universe results in the light from faraway galaxies being redshifted. This is called the "cosmological redshift"; it can be compared with the Doppler effect (which also causes a redshift), but the details are somewhat difference.It is an observed fact that most galaxies are redshifted; the explanation that seems most reasonable is that it is caused by the cosmological redshift. This means that space itself is expanding.
Yes, galaxies emit light primarily from the stars within them. This light can range from visible light to other forms of electromagnetic radiation such as radio waves, infrared, ultraviolet, and X-rays. The light emitted by galaxies allows astronomers to study their composition, age, and distance from Earth.
Edwin Hubble proved the existence of other galaxies by observing the redshift of light from distant celestial objects. In the 1920s, he analyzed the spectra of these objects and discovered that their light was redshifted, indicating they were moving away from us. By correlating the redshift with their distances, Hubble established the relationship known as Hubble's Law, demonstrating that the universe is expanding and that these distant, redshifted objects were indeed separate galaxies beyond the Milky Way. This groundbreaking work fundamentally changed our understanding of the universe's structure.
The light astronomers observe through telescopes provides crucial information about galaxies, including their composition, temperature, distance, and motion. Different wavelengths of light, such as visible, infrared, and ultraviolet, reveal the presence of elements, star formation rates, and the dynamics of galaxy structures. By analyzing the spectra of this light, astronomers can also determine redshift, which helps measure the galaxy's speed and distance from Earth, offering insights into the universe's expansion. Overall, light serves as a fundamental tool for understanding the nature and evolution of galaxies.
Galaxy redshift is much light the Doppler effect. If a galaxy is traveling away from us, the light that it emits and is seen by us is stretched out (the faster we are separating, the stronger the redshift), that means that the wavelegnth is stretched a bit, shifting the light towards red.
When the spectrum of light from a star is redshifted, it indicates that the star is moving away from the observer. This is due to the Doppler effect, where the wavelengths of light stretch, causing them to shift toward the red end of the spectrum. Redshift can also suggest the star is part of an expanding universe, as seen in distant galaxies. Overall, redshift is a key indicator of the star's velocity relative to Earth.
When astronomers investigate the most distant galaxies, they find evidence that the universe was much younger and more active in its early stages. Observations of these galaxies reveal higher rates of star formation and interactions, suggesting that they were in a more chaotic and dynamic state. Additionally, the light from these galaxies has taken billions of years to reach us, allowing astronomers to study the evolution of galaxies over cosmic time. This research helps to deepen our understanding of the universe's formation and the processes that shaped its structure.
The evidence for Hubble's Law, which shows the relationship between distance and recession velocity of galaxies, was collected through observing the redshift of light from galaxies. Astronomers used spectroscopy to measure the redshift of galaxies, which is caused by the Doppler effect as the galaxies move away from us. By studying the redshift of galaxies at different distances, astronomers were able to support the idea that the universe is expanding.
shifted to longer wavelengths, indicating that the galaxies were moving away from us. This observation led to the development of the theory of the expanding universe.