Have you ever asked how astronomers gather information from space? How do they measure the mass of stars, the distance to stars and galaxies, and the elements in the bodies of stars? What is the key “actor” that has helped astronomers?
The key “actor” that has helped astronomers is light.
Light, in all its different forms, is the key way astronomers learn about the universe. By studying the light that comes from stars, planets and galaxies, whether it’s light they give off, absorb, or reflect, astronomers can figure out things like what they’re made of, how hot they are, how far away they are, and how they’re moving.
So, where does the light come from?
Photons are the fundamental particles that makeup light. A photon is a quantum of electromagnetic radiation, meaning it’s the smallest possible packet of energy associated with light. Photons are massless objects that travel at the speed of light in a vacuum (approximately ~300 km/s), and exhibit both wave-like and particle-like properties (wave-particle duality). We won’t delve too deeply into the concept of light-particle duality; it will be discussed in more detail in quantum physics. Let’s move on!
In this section, I will show you basic measurements for the distance in astronomy. We use some of the units for the distance. Remember that the distance of the star is so far far away from us, from Earth. Using a kilometer unit is not common and it is quite a hassle for us. We usually use light year, astronomical unit (au) and parsec (pc).
Related with “compiling the light”, I think it will be more advanced topic about spectroscopic. For more distant stars, astronomers use a method called spectroscopic parallax. They first determine a star’s luminosity class and its apparent brightness by analyzing its spectrum. By comparing these observations with the star’s known luminosity class, they can estimate its distance based on how its light has dimmed.
For the first, let’s start by getting acquainted with the basic topic.
What is the Astronomical Unit?
Astronomical Unit means the average distance between the Earth and the Sun is about ~150 mio kilometers. This unit is commonly used in our Solar System, like the distance for Saturn is about 8.75 au.
What is the Light-Year unit?
Sound familiar with Buzz from Toy Story right? HAHA. But it’s not about Buzz. Light-year (next we can call with ly) is a unit of the distance when light travels with ~300 km/s at 1 year. We know that the basic distance formula is s = v/t. Here, (v) is for velocity/speed, and (t) is for time. If we convert 1 ly to kilometer, we get about 9.461 x 10¹² kilometers. Imagine how far the distance is. The nearest star from our Solar System is Alpha Centauri (α Cen), the brightest star in the Centaurus constellation. The distance for it from the Earth is about ~4.4 ly.
What is the Parsec unit?
Apart from both mentioned above, we also use a parsec unit. Parsec is an acronym for Parallax Second. Astronomers derived the value for 1 pc as ~3.26 ly through the parallax’s concept.
So, what is the parallax?
Parallax is the apparent shift in the position of a nearby star against the background of distant stars as observed from Earth at different positions in its orbit around the Sun.
Source : http://hyperphysics.phy-astr.gsu.edu/hbase/Astro/para.html
As for the illustration above, the formula for d = 1/p, when the p = 1 arcsecond (1/36000 degree). Use trigonometry that d = 1/tan (p). We get the value 206,265 AU ~ 3.26 ly when we convert it to a light-year unit.
It is just about converting the unit to simplify the value. The universe is so big if we insist on using kilometers. We are too small to compare with the universe.
I’ll explain how we measure the Sun’s mass, what it’s made of, and where it will go when it dies. I’ll do my best asap, maybe next time. (Giggling ckck)
Reference:
Stellar Parallax, HyperPhysics, accessed on Tuesday, Aug 13th, 2024, http://hyperphysics.phy-astr.gsu.edu/
NASA Image, NASA, accessed on Tuesday, Aug 13th, 2024, https://science.nasa.gov/gallery/hubbles-universe/