Education

Astronomy with the World of the Deaf #5 The sun

The sun - how far is it from us? How is it built? How hot is it? You can find this and other information in the movie "Astronomy with the World of the Deaf # 5 Sun". Tomasz Smakowski explains in Polish sign language. [Automatic translation. Please let us know if you notice an error]

The sun – we all know what it is. We feel them every day. We see them everyday. Even when it is hidden behind the clouds, it is bright during the day, thanks to the sun. In short, without the sun, life on earth could not exist. But what exactly is the sun? How it works?

The size of the sun

Let’s start with the fact that the sun is HUGE. The sun has the shape of an almost perfect sphere, about 1,400,000 km in diameter. For comparison, the Earth has a diameter of 12,742 km. This means that the diameter of the Sun is equal to 109 Earths !!! Let’s see it in the picture (57 seconds in the video).

On the other hand, if we compared the Sun to a huge empty ball or ball, it could contain as many as a million Earths! An ordinary plane would take up to 7 months to orbit the sun. And although the Sun is huge, it belongs to the group of medium-sized stars – there are other stars in space so large that when compared to the sun, The sun is a tiny dot next to them. Anyway, see for yourself (see video 1:39).

The mass of the sun

The sun is also terribly heavy. If we compare the masses of the sun and the earth, the mass of the sun is 333,000 times the mass of the earth. The mass of the sun is 99.86% of the mass of the entire solar system. What does it mean? If we count the weight of all planets, such as Mars, Jupiter, Earth, etc., their moons, various asteroids, asteroids, and all that is in the solar system, the mass of all these objects will constitute just 0.14% of the mass of the entire solar system. The rest is just the sun. In the core of the Sun, matter is very dense – 1 liter of matter from the sun’s core weighs about 150 kg.

Distance from Earth to the Sun

The sun is also very far away. Do you remember episode 3 of Astronomy with the World of the Deaf with astronomical units? In this episode it was said that the Sun is 150 million km from Earth – to understand how far it is, let’s take an example: if you wanted to go to the sun at the speed of an ordinary car, you would be flying about 200 years.

Structure of the Sun – the core

How is the sun built? It consists of hot plasma. What exactly is plasma, we will definitely do a separate section about it someday, but imagine it as a very dense gas. So we have a giant gas ball in which the transformation of hydrogen into helium – in one second, 620 million tons of hydrogen is turned into helium. Energy is also produced. In the center of the sun is, of course, the nucleus. This is where the reactions we just mentioned take place. From the core, photons transfer energy to the upper layers of the sun. It takes over a million years! The nucleus takes up about 25% of the diameter of the Sun.

Structure of the Sun – the radiant zone

Apart from the core, we divide the Sun into so-called layers or shells, zones – each of them has different characteristics. The first of them – apart from the core – is the radiant zone, it extends up to about 70% of the Sun’s radius. There are no chemical reactions in it, but the heat is transferred from the core to the outside of the sun.

Structure of the Sun – convective zone

The second layer is the convective zone – from 70% of the sun’s ray to its surface. This layer is approximately 200,000 km thick. What’s going on in this layer? Hot gas rises to the surface of the sun. Here the gas cools down, and then, already cooled, it sinks lower. Below it, it heats up again and the cycle repeats itself. This process is called convection.

Structure of the Sun – photosphere

The next layer is the photosphere – this is the part of the sun that we see. It is “only” about 400 km thick. For the sake of simplicity, we could say that the photosphere is the surface of the sun. However, since the Sun is a giant ball of gas, it is hard to tell where that surface would be. Therefore, it is assumed that this is a place where the solar atmosphere, seen from the Earth, ceases to be transparent. It is in this layer that most of the photons are formed.

And what does the photosphere look like up close? You can see it in the video behind me (see video 6:23). What we see is called solar granulation. It looks a bit like a thick soup, right? But it’s not very clear from the movie what size it is. So – in every such clear fragment, a cell, Poland would fit.

We just said that hot gas, plasma, rises to the surface. In the film, bright fragments, cells, this is hot gas. The gas cools down and flows towards these black lines, or cell edges. These are places of cooler gas. Colder doesn’t mean colder. He’s still hot, just cooler than the light part. And then, from these black spots, the gas flows down the star, into the convection zone, where it heats up again.

These black stripes look narrow, but can be up to 200 km wide. And they are not actually black – they simply emit less light than the bright parts, which is why in the photo we see them as darker.

Solar atmosphere – the solar corona

Above the photosphere is the solar atmosphere. The solar corona is part of the solar atmosphere. And although it is luminous and above the surface of the sun, we cannot see it, because its light is too dim compared to the blinding light of the photosphere. There is one exception, however, when we can see the solar corona with our own eyes – it’s a complete solar eclipse. Then, for a few minutes, the Moon covers the Sun’s disc – the photosphere, and the sun’s corona appears beautifully.

Unfortunately, the next full solar eclipse seen from Poland is October 7… 2135. Maybe it is worth saving in the calendar? 😉

Solar atmosphere – heliosphere

Even further away is the largest part of the sun’s atmosphere – the heliosphere. The heliosphere is filled with plasma from the solar wind – it is very rare and extends beyond the solar system! The Heliosphere can be compared to a giant bubble that stretches for billions of kilometers. The Earth is also inside the heliosphere, so we can say that the Earth is in the solar atmosphere. Let’s see in the illustration what it might look like (9:32). Remember that this is an artistic illustration, not a real photo. The little yellow dot is the Sun, the orbits of the planets around it, and far beyond them we see a bubble of the heliosphere.

The heliosphere is dangerous to the Earth, but we have a shield in the form of the Earth’s atmosphere and the Earth’s magnetic field. At the same time, the same heliosphere that is dangerous to us protects us from cosmic rays, which comes from other stars and is very dangerous.

The temperature of the sun

The sun is hot and we find out for ourselves on a hot day. But of course the temperature of the Sun is incomparably higher than it is here on Earth. And so: the temperature at the core of the Sun is about 15.5 million degrees. On the surface, the Sun is around 5,500 degrees Celsius and then rises rapidly, and several thousand km above the surface of the Sun, the corona of the Sun, which is what we see during a solar eclipse, has a temperature of several million degrees. Scientists do not fully understand where this sharp rise in temperature is coming from.

Sunspots

Sometimes the so-called sun spots. What is this? Earlier, we said that hot gas, plasma, rises to the surface, cools it, and descends back into the star. But sometimes this process is disturbed and colder gas than normal reaches the surface in some places, than in the rest of the sun. And just like before we saw black stripes – the edges of cells that are cooler than the rest of the surface, there, the sunspots are cooler gas, which we see in the photos as a dark place, spots. They are actually bright, only darker than their surroundings. And although the spots are cooler than the rest of the sun’s surface, which is around 5,500 degrees Celsius, they are very hot anyway – their temperature is around 4,000 degrees Celsius.

Sometimes the sun is completely clear of sunspots, and then there are more and more, until their number decreases again and disappears completely, and the cycle repeats itself. One such cycle lasts about 11 years. And just recently, in 2021, a new cycle began. This means that over the next 5 or 6 years the number of sunspots will increase.

The rotation of the sun around its axis

Imagine the Earth is a giant ball. If we mark, for example we draw three points on it, one on the top, one in the middle and one on the bottom, and we turn the ball, all these points will turn too and they will return to the same place at exactly the same time. And this is how it is on Earth – our entire planet rotates evenly and it takes 24 hours. The sun also rotates, but its rotation is not as smooth as it is on Earth.

And so: the rotation time at the equator is 25 days, and at the poles 35 days. This is because the Sun is a giant ball of gas. This causes disturbances in the magnetic field, contributes to the formation of sunspots, which we have just talked about, as well as the emergence of prominences or flares.

Prominences and solar wind

What we see in the picture (13:49), is exactly the prominence. This arc is part of the gas, the surface of the sun, that has fired, creating such beautiful shapes. They are huge. Several planets such as Earth could fit in the center of this arc. Most often, all the material that is fired falls back to the surface of the sun. Sometimes, however, the force of the explosion is so great that this material, with great energy and weighing billions of tons, escapes into outer space. We call it a solar flare and it can be very dangerous to us. Such a flare contains an enormous amount of energy. We call it the solar wind.

The Earth is protected against low energy by its atmosphere and magnetic field – this energy is pushed towards the Earth’s poles, and as a result, we see beautiful auroras there. But if a large solar flare hit Earth, our magnetic field might be too weak.

Geomagnetic storm

This was the case on September 1, 1859. One of the largest recorded flares was recorded then. The English amateur astronomer Richard Christopher Carrington was the first to spot this great flare. He drew sunspots. To this end, he watched the sun, but of course he did not do so with the naked eye, because it is not allowed to do so. It looked as if he had a telescope aimed at the sun that was shedding light on the paper. On the page he could see both the sun and the sunspots. Then he redrawn the shape of the sunspots.

It was then that the biggest solar flare in history happened. The astronomer saw luminous points on the page because the flare in the sun was so bright and bright. 18 hours later, the world was in chaos. Of course, in the 19th century there were very few electrical devices that could break down, but for example there were telegraph lines – as a result of the solar flare reaching the Earth, these lines sparkled and ignited! The compasses freaked out, and the northern lights were visible not only at the poles, but also in Cuba, Australia and Great Britain!

A Contemporary Threat

What if there had been such a flare today? This was the case in March 1989. The flare reached Earth after three days. The northern lights were visible in Florida, and 7 million people in Canadian Quebec were without electricity.

So we see that a strong solar flare can deprive us of electricity, destroy transmission lines, satellites, communication systems, electronics. The losses would be huge. But even a much smaller flare can disrupt satellite communication or completely destroy satellites – because they are located outside the magnetic field that protects the Earth. Unfortunately, we have no way of influencing the activity of the Sun, nor of preventing the solar flare from hitting the Earth.

And we had a similar situation recently, and more precisely: on Sunday, January 30 – there was a solar flare that began to move towards the Earth. On Thursday, February 3 – SpaceX launched 49 Starlink satellites into orbit. On Friday, February 4 – the solar flare reached Earth. 40 satellites were destroyed.

What happened? Have they been burned by the flare? Not. The solar flare itself, or actually all the energy that came to Earth from that flare, did not damage the satellites. But the solar flare caused a geomagnetic storm on Earth, as a result of which the densities of the atmosphere increased. The satellites were at an altitude of about 200 kilometers. As a result of the storm, the density of the atmosphere in this place increased by about 50%. So the air resistance was much greater than normal, the satellites slowed down and fell.

Of course, the density of the atmosphere at an altitude of 200 kilometers was still very low compared to that on the ground below. But its sudden compaction was enough for the satellites to drop out of their low orbit.

Astronomy with the World of the Deaf

That’s it for today. There was a lot of information about the Sun today, right? 🙂 Yet there are still many things that we haven’t mentioned in this episode. That is why we will definitely return to the Sun more than once in our films. Finally, a warning: remember, NEVER look at the Sun with your naked eye, let alone binoculars or a telescope !!! This way you can permanently and irreversibly damage your eyesight!

See you in the next episodes of Astronomy with the World of the Deaf.

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