Added: Lanna Fortson - Date: 21.11.2021 01:11 - Views: 24888 - Clicks: 2340
An astronomer explains how they form, why they appear to twinkle, how they got their name, and much more. The following questions were answered by astronomer Dr. The biggest stars are known as "red supergiants. If you plopped Betelgeuse into the middle of our solar system, it would fill it out to roughly the orbit of Jupiter! Red supergiants are about times larger than our sun. That would be about million miles across, which is over three times the distance between Earth and the sun. If the sun were a red supergiant, it would swallow up Mercury, Venus, Earth, Mars, and some asteroids!
Betelgeuse is actually cooler than our sun.
That is why it is red — red stars are cooler than the sun, blue-white stars are hotter. Betelgeuse is, however, much bigger and brighter. It is about times bigger than our sun. Also it is about 10, times brighter than our sun because a larger star is brighter.
We think that there are about billion stars in our galaxy, the Milky Way. There are billions of other galaxies, too. So the total of stars in space is HUGE!!!! Of course you can't see them all.
Most of them are too faint to see except through a big telescope. I'm not sure why you see stars on some nights where there were none before. Sometimes the sky is very clear and you can see fainter stars, while other times it is a little hazy and you can see only the brighter stars. Scintillation, or the "twinkling" we see of stars in the sky, is due to motions in the earth's atmosphere. I have watched this many times through a telescope! So it is very much connected to our atmosphere and its weather. When we look at a star from the surface of the earth, we are also looking through the various layers of the atmosphere.
Air has several kinds of motions. There is the wind, of course, but it also has a convective bubbling motion where blobs of hot air rise, cool, then fall, to be warmed by the warm earth below. The astronomers and engineers who build telescopes are very familiar with this, because some of these telescopes are deed to get around the blurring effects of these motions. When I used to observe at Perkins Observatory in Ohio, I noticed that the scintillation we also call it "seeing" changed in a predictable pattern The sun looking for stars on the weather. Right after a front passed, the atmosphere was turbulent bubbling a lot and the image of the star was large and blobby.
The next night the air was calmer, and the image of the star looked smaller and more stable. This would continue, until the cirrus clouds that come before the next front arrived. Then the image was the smallest and most stable the icy cirrus clouds form in very calm air. I think of stars being rather faint because they are so far away! Most stars are very similar to our sun.
In fact the sun is a pretty normal kind of star. It's much brighter than the other stars because it is close by. Even the closest star other than the sun is very far away.
To give you an idea of how far, we can compare the time that it takes for light to travel from one place to another. Light is very, very fast; it travelsmiles in one second. Even so it takes about eight minutes for light to travel from the sun to the earth.
How long does it take for light from the sun to travel to the nearest star? When you look at the stars at night, some are closer and some are farther. Most of the stars that are the brightest are also the closest to us.
The farther away the star is, the fainter it is.
Well, no, stars are not on fire although they look that way. We sometimes talk about them "burning," which can be confusing because we don't mean burning as in fire. Stars shine because they are extremely hot which is why fire gives off light — because it is hot.
The source of their energy is nuclear reactions going on deep inside the stars. In most stars, like our sun, hydrogen is being converted into helium, a process which gives off energy that heats the star. The inside is actually millions of degrees, extremely hot! That warms the outer layers of the star, which gives off heat and light.
Something that is on fire, like the wood in a fireplace, requires oxygen to burn. The temperature of such a fire is hot, but not as hot as The sun looking for stars star! Did you know that our sun is a star? It's a pretty ordinary, normal kind of star. So that's what a star looks like up close. Some stars are bigger, some are smaller, some are hotter and look bluish-white and some are cooler and may look yellow, orange, or red.
Baby stars are born in big, dark clouds of gas and dust. They start out all wrapped up in these clouds, like blankets protecting them. But there is one thing about baby stars you might not expect. They start out BIG and get smaller as they grow older! That is because the baby stars are formed out of those clouds, and gravity pulls them together to make a star.
The baby star starts out big and cool, surrounded by clouds, so you can't see it. But as it gets older, it gets hotter and brighter. The clouds are blown away and then you can see the baby star now more like a "toddler". Where do "young" stars get their energy from if nuclear fusion has not yet taken place? When does it finally take place? Young stars get their energy from gravity. They are slowly contracting, and as they squeeze together that generates energy which gets radiated away as light.
Once the center of the star is hot and dense enough millions of degrees! It takes a star the size of our sun about 20 million years to reach this point. Once it starts nuclear fusion, the star can shine for about 10 billion years. The first method is to look at the star's spectrum formed when we spread out the light from the star into the various colors, like a rainbow. Using special instruments, we can find dark lines in the spectrum that correspond to the elements in a star.
The element lithium can be used to get an age for a star because the amount of lithium in a star decreases with time. This is because it gets converted to other elements by nuclear reactions.
So if we can measure the amount of lithium in the star, we can get its age the less lithium, the older the star. The The sun looking for stars method is to find the age of a cluster, or group, of stars. Many stars form together in clusters, so they all have the same age. We know from our calculations that very big, massive stars burn up their nuclear fuel very fast and have short lifetimes, while smaller stars use up their fuel much more slowly and can continue giving off light for much longer.
By looking at the various stars in the cluster we can see which ones have used up their fuel and become red giants and which ones are still shining as usual. Then we can figure out that all the stars in the cluster must be the same age as the age of the stars that just recently used up their nuclear fuels. For instance, if all the stars that are greater than three times as massive as our sun have run out of nuclear fuel and have become red giants, then we know that all the stars in the cluster are million years old. Well of course here on Earth we see the sun brighter than anything else!
That is because the sun is so much closer than the other stars. But if you could line up a bunch of stars, including our sun, all at the same distance, you would see that some stars are brighter and some are fainter than our sun.
The biggest, heaviest stars can make more energy and shine more brightly than the sun. The smaller, lighter stars make less energy and shine less brightly than our sun. So it all depends on how big and heavy a star is. It's all due to gravity. The nebula consists of gases, mostly hydrogen, and also dust. The dust is just what you would expect, tiny rocky particles. If the nebula is cold and dark, denser blobs can form in it. Those blobs have gravity and can put surrounding gas and dust into them. As they get bigger, they have stronger gravity and can pull more and more gas and dust to them.
The inner layers of gas and dust start to warm from the pressure of the gas and dust above. The dust is vaporized and turned into gas. When the inner gases get hot enough, the blob — now a protostar, or very young star — begins to glow.
At first it can be seen only in infrared light, but as it warms up and brightens it can be seen as a red star.The sun looking for stars
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How do we know what stars like our Sun are made of?