Today we’re taking a look at that hot glowing ball of plasma we call the Sun.
1. It’s Really Massive
In fact, the Sun accounts for over 99.8% of the total mass of the Solar System. That’s right – all the planets and all the moons and all the other small cosmic objects make up less than 0.2% of the Solar System’s mass. In you want some really big numbers, the Sun’s mass is approximately two nonillion kilograms (that’s a two and thirty zeroes). By volume, the Sun is equivalent to 1.3 million Earths.
Actually, the solar mass is used quite often in astronomy as a standard unit of measurement for really, really big things. When we talk about stars or nebulae or even galaxies, we often use the solar mass unit to express their mass. When dealing with smaller objects, we usually stick to using Earth’s mass as a measurement unit (which is 333,000 times less than the solar mass, btw).
2. It’s Not Really That Massive
I know I just said that the Sun is really, really big, but that’s only compared to other stuff in our Solar System. Venture beyond for a bit and the Universe is filled with much bigger things. The Sun is classified as a G-type main sequence star, commonly referred to as a yellow dwarf although that’s not very accurate.
As the name suggests, there are much bigger stars out there classified as giants, supergiants and hypergiants. UY Scuti, a red supergiant located 9,500 light-years away, is currently a frontrunner for the title of Largest Known Star with a diameter approximately 1,700 times that of the Sun. That’s a circumference of 7.5 billion kilometers. Even light needs almost seven hours to circumnavigate the star. If, somehow, our Sun and UY Scuti switched places, the star’s surface would extend well past Earth and even past Jupiter.
3. What Happens When the Sun Dies?
Stars might have really long life cycles ranging in the billions of years, but they still have to die some day. Their ultimate fate is dependent on their size. Smaller stars end up as stellar remnants called brown dwarfs. The massive stars have a much more explosive finish – they can go supernova or even hypernova and collapse into a neutron star or a black hole. In rare cases, these giants can even experience a highly-energetic explosion known as a gamma-ray burst.
Our Sun is somewhere in the middle – it won’t put on a massive show but won’t fizzle out, either. Once it reaches the end of its main sequence and it exhausts its hydrogen fuel, the Sun will start collapsing under its own weight, causing the core to get denser and hotter. This will cause the Sun to expand as it sheds its outer layers, thus becoming a red giant. Finally, it will settle in as a white dwarf – a tiny stellar remnant of incredible density (it’s about the size of Earth but still has the mass of the Sun).
4. What’s It Made Of?
Primarily hydrogen and helium, like most stars. It’s about 71% hydrogen, 27% helium and the remaining 2% consist of trace amounts of dozen of elements, primarily oxygen and carbon. In fact, in astronomy, all the elements except for hydrogen and helium are commonly referred to as metals (not to be confused with solid metals we all know & love). Metallicity is the astronomical term for the fraction of mass of a cosmic object consisting of everything except hydrogen and helium.
5. How Hot Is It?
That really depends on what part of the Sun we are talking about. The core of the Sun is insanely hot – temperatures reach 27 million degrees F (15 million degrees C). Then, as we make our way through the various layers of the star, temperatures keep dropping until we reach the chromosphere which is “only” a few thousand degrees. However, temperatures quickly climb in the millions of degrees in the outer layer of the Sun, the corona, and we’re not entirely sure why, although we have a few good ideas.
6. How Old Is It?
The Sun is about 4.6 billion years old. We’ve calculated its age by looking at other things from our Solar System that we can date more accurately such as meteorites or even Earth rocks. Although they might seem unrelated, our current understanding suggests that the Solar System formed as a unit, meaning that its main components were all formed around the same time. A G-star has a typical lifetime ranging between 9 and 10 billion years, meaning that our Sun is about halfway through.
7. How Bright Is It?
Obviously, the Sun is the brightest thing in our sky because it is much, much closer to us than any other star. Turning to the night sky, Sirius is the brightest star, followed by Canopus.
The apparent magnitude is the term used to denote the brightness of a celestial object from Earth. The Sun has an apparent magnitude of -27. However, the problem with this type of measurement is that it’s entirely reliant on the position of the observer. It shows the brightness of a star using Earth as a reference point, not its true brightness. That is why astronomers also use absolute magnitude, meaning the brightness of a star observed from 32.6 light-years away aka 10 parsecs.
8. How Fast Is the Sun?
The rotation of the Sun is a bit tricky to pin down because it changes depending on the region. If you want the short answer with no explanation, then the Sun does a full rotation in approximately 25.4 days.
The Sun doesn’t actually rotate as a solid body like Earth does. It is fastest at the equator (24.5 days) and starts slowing down as we head towards the poles (38 days). The aforementioned sunspots make it pretty easy to keep track of the Sun’s rotation because some of them can last for months.
As far as the Sun’s speed in the Universe is concerned, our whole Solar System is orbiting the center of the Milky Way galaxy just like Earth orbits the Sun. The speed we’re traveling at is 514,000 mph or 828,000 km/h. One full orbit is known as a galactic year and it takes anywhere between 225 and 250 million Earth years.
9. What Are Sunspots?
Occasionally, dark spots can be observed on the surface of the Sun known as sunspots. They have a lower temperature than the rest of the solar surface and are caused by fluctuations in the Sun’s magnetic field. Some of them can be large enough to see with the naked eye and it is possible for groups of 100+ sunspots to appear at the same time. However, this is exceedingly rare. And don’t let their appearance fool you. Sunspots only appear dark because they are set against an incredibly bright background. On their own, they would also be very bright.
10. The Sun Reverses Its Magnetic Field
North is north and south is south, right? Well, not really, because geomagnetic reversals happen all the time. The positions of magnetic north and magnetic south are switched around. What is odd about the Sun’s magnetic field is that its polarity changes quite often. It changed during your lifetime and will likely change again, approximately every 11 years.
The Earth goes through the same process, except far less often. The last time it happened was roughly 800,000 years ago, but we have no idea when it will happen again.