Some Basics About Astronomy!!

Some Basics About Astronomy!!

Astronomy is the study of everything in the universe outside the Earth's atmosphere.  This includes things we can see with our naked eyes, such as the sun, moon, planets, and stars.  It also includes objects that we can only see with telescopes or other instruments, such as distant galaxies and small particles.  And it also includes questions about things we can't see at all, like dark matter and dark energy.

Early observers of the night sky saw patterns in the stars.  These patterns, which we call constellations, may appear to change place, but they do not change shape.  People around the world gave them names (like Orion the Hunter or Leo the Lion) and told stories about them.  You may know some of these stories as mythology or astrology.  Astrology is fun to think about, but it's different from astronomy.  Astrology is not science!  Early observers also saw some bright objects in the sky that seemed to revolve around the stars.  Ancient Greek philosophers called these objects "planets".  The planets are our closest neighbors, and they move.  They revolve around the Sun, just like the Earth does.

To the naked eye, stars look like tiny dots of light.  But stars aren't tiny—they're huge, burning balls of gas like our Sun.  They only appear small because they are so far away.  The nearest star to our solar system is 4 light years away, which is 20 trillion miles.  All the stars can be seen at the same distance, as if they were affixed to the wall of a large dome.  But this is also an illusion.  Some stars are tens of thousands of light years away from Earth than others.

How can we tell how far away a star is?

A clue is its brightness. If we were closer to them, the distant stars would appear dim in comparison. But this indication is not very reliable, because the brightness of the stars varies greatly. Some of the stars that stand out in the sky aren't really that far away compared to other stars, they're just incredibly big and bright. And some nearby stars are dim. In fact, our Sun's nearest stellar neighbor, Proximus Centauri, is such a tiny baby that we need telescopes to see it! So astronomers rely on measuring something called parallax to find the distance to stars. They look at a nearby star from two different locations and compare its position to other, much more distant stars.

You may feel like you're sitting still, but are you really? No, you're flying incredibly fast through space! This is because the Earth is carrying you like a spaceship. The earth is spinning. If you were standing at the equator, you and the ground beneath your feet would be spinning at about a thousand miles per hour. But the Earth is also orbiting the Sun, moving even faster: 67,000 miles per hour. And the sun itself is spinning around the center of our galaxy, taking everything in the solar system with it, at a speed of 490,000 miles per hour. And that's not all. Our galaxy, the Milky Way, is also moving—at 872,405 miles per hour. Our galaxy cluster is also moving. And so is everything else in the universe. Yes, fur aya savad?

 If the earth is moving so fast, why don't we fly?

Can thank gravity for that. Gravity is the force of attraction between all objects in the universe. The gravity of an object depends on its mass. The greater the mass, the stronger the gravity. And the closer two objects are, the stronger the gravitational pull between them. Gravity is what keeps your feet on the ground—and what helps Earth and the other planets orbit the Sun instead of floating.

Light is more than what our eyes can see.

Light is a form of energy called electromagnetic radiation.  We see objects because they reflect light to our eyes.  But there is a whole spectrum of electromagnetic radiation, and our eyes can only detect a small part of it.  That part—visible light—is made up of different wavelengths of light that we perceive as different colors.  If you think of the electromagnetic spectrum as a piano keyboard, visible light equals one octave.  Objects in space are emitting or reflecting radiation from all over the spectrum, including ultraviolet (UV), infrared, microwaves, and radio waves.  To see this invisible electromagnetic radiation we need to use special instruments like microwave telescopes and gamma ray telescopes.

So far we've talked about things we can detect with our eyes and our instruments, such as galaxies, stars, and planets.  These objects (and even trees, dogs, and your beloved) are all called substances.  But did you know that there are things in the universe that we cannot detect, no matter what instruments we use?  They are called dark and dark energy.

Dark matter does not emit light like a galaxy or absorb light like a black hole.  Scientists know it exists because it has gravity, just like normal matter.  Dark energy is a mysterious pressure that works against gravity, pulling matter apart.  Scientists still don't know much about dark matter and dark energy, but they are hard at work trying to learn more.  Will you try?

The universe is very very vast, not so vast that you love your lover as much as the vast universe that has yet to be discovered, which needs more astronomers, many secrets of the universe are waiting for you.  When you come and open them.