Wisley’s Astronomy Briefing
Chapter 8
Astronomical Concepts
Unfamiliar about the special words and phrases used by scientists and astronomers? Don’t worry, here is a guide to some of them!
Redshift
You might know that the universe is ever expanding, but one of the reasons we know that fact is due to galaxies experiencing redshift as astronomers observe them from Earth. As the universe is expanding, the wavelengths of light get stretched longer and longer. Since red light has a longer wavelength than blue light, that is why objects moving further away from the observer tend to be redder. In the opposite direction, blueshift describes objects moving closer and closer to the observer.
Schwarzschild Radius
The Schwarzchild radius is the gravitational radius needed to form a black hole. As the German physcist Schwarzchild hypotheized based on Eisntein’s theory of relativity, anything with mass can become a black hole if it reaches a specific radius. That built the foundation for the existence of black holes, which was later proven by indirect and direct observations from telescopes and scientists.
Planets
According to the International Astronomical Union (IAU), there needs to be three requirements in order for an object to be a planet. First of all, a planet needs to orbit a star, like the Sun. Secondly, the planet needs to have enough mass to have gravity and form itself as a round object. And thirdly, the planet must clear its neighbourhood around its orbit, this is the criteria that is infamous for kicking Pluto out from the planets club and into the dwarf planets.
Doppler Effect
Have you ever heard the siren of an ambulance? When it is coming near you, the sound gets louder and louder, and when it leaves away, the sound gradually dims down. That works the same in space, but instead of listening to sounds, astronomers see that pattern through wavelengths. Many exoplanet hunters use the doppler effect to observe exoplanets, and just like redshift from earlier, the principles from the doppler effect were used on cosmic expansion.
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