Journey to the Sun: The Life Cycle, Observation, and Fun Facts
On May 3, people around the world celebrate the International Sun Day. It’s a day to honor the Sun as the source of energy, light, and life itself. The Sun is crucial to life on Earth and great for observations, as long as you do them safely. To plan your observations, try using our app Sky Tonight. It gives you the exact times of different twilight phases in your area, so you'll always catch the perfect blue or golden hour. Now, let’s get to know our precious parent star even better!
Contents
- Quick facts about the Sun
- Life of the Sun
- Layers of the Sun
- How to observe the Sun?
- F.A.Q.
- The Sun: bottom line
Quick facts about the Sun
- Official name: Sun
- Alternative names: Sol, Helios
- Catalog designations: None
- Star type: yellow dwarf
- Apparent magnitude: -26.74
- Mass: 2 x 10³⁰ kg (4.4 × 10³⁰ lbs), about 333,000 Earth masses
- Luminosity: 3.828×10²⁶ W
- Radius: 695,700 km (432,287 miles)
- Surface temperature: ~5,600 ° C (~10,000 ° F)
- Composition: 71% hydrogen, 27% helium, 2% other elements
- Distance from the Earth: 149 million km (93 million miles)
- Rotation period: 25 Earth days at the equator and 35 Earth days at the poles
What type of star is the Sun?
The Sun is a G2 V star, commonly known as the yellow dwarf. The "G2" designation means that it is in the second category of the yellow G class, with a surface temperature of about 5800 K. The "V" refers to its status as a main sequence star.
How big is the Sun?
The Sun is the largest object in our Solar System, extending about 695,700 km (432,287 miles) from its center to the surface. It accounts for 99.86% of the total mass of the Solar System and is so large that it could pack in about 1.3 million Earths! In terms of the universe, however, it is considered an average-sized star. Some stars are as small as one-tenth the size of the Sun, while others can be more than 700 times larger.
How hot is the Sun?
The temperature of the Sun varies dramatically, from about 15 million ° C (27 million ° F) at its core to about 5,600 ° C (10,000 ° F) at its surface. Even though the surface is "cooler," it's still so hot that no solid or liquid can form there, so the Sun really doesn't have a solid surface at all. So, even if you could somehow tolerate the heat, you couldn't stand on the Sun.
Cosmic temperatures may be too extreme to imagine. Take a look at our Solar System Thermometer infographic to get an idea of how hot (or cold) they can really be.
What is the color of the Sun?
The Sun is actually white, meaning that it emits all the colors of the visible spectrum. But to us on the Earth, it appears orange-yellow or even red when it's near the horizon. This is because the Earth's atmosphere scatters shorter wavelengths of blue light more efficiently than red, orange, or yellow light wavelengths. So, we simply miss a part of the spectrum.
Does the Sun spin?
The Sun spins, or rotates, in a counterclockwise direction. However, it's not solid like the Earth, and different parts of it rotate at different speeds. The Sun's equator takes about 25 days to complete a full rotation, while its poles rotate once every 35 days.
The Sun also moves clockwise around the center of the Milky Way galaxy. It takes the Sun about 225 to 250 million years to complete a full circle around the center of the galaxy.
Life of the Sun
How old is the Sun?
The Sun is about 4.6 billion years old and is currently in the middle of its lifespan. It belongs to a generation of stars known as Population I, which are young, metal-rich stars typically found in the spiral arms of the Milky Way galaxy.
How was the Sun formed?
About 4.6 billion years ago, the Sun began to form from a molecular cloud of mostly hydrogen and helium. A shock wave from a nearby exploding star hit this cloud, causing it to begin to shrink. As it shrank, parts of the cloud began to fall in on themselves due to gravity, spinning and heating up. Most of the hydrogen and helium gathered in the center of this hot, spinning mass. Eventually, the gases got hot enough to start nuclear fusion, creating the Sun we see today.
What powers the Sun?
Nuclear fusion is the key process that powers the Sun. During this fusion, hydrogen atoms in the Sun's core fuse together to form helium atoms and release huge amounts of energy as heat and light.
What is the 11-year solar cycle?
The solar cycle, also called the solar magnetic activity cycle, or sunspot cycle, is an approximately 11-year cycle that marks changes in the Sun’s activity. During this cycle, the Sun's magnetic poles switch places — what was once the north pole becomes the south pole, and vice versa. It then takes another 11 years for the poles to switch back.
The number of sunspots visible on the Sun’s surface varies with this cycle. In the beginning, called the solar minimum, the Sun might have only a few small spots, typically at lower latitudes, and there can be months with no spots at all. As the cycle progresses, solar activity increases, reaching a peak in the middle of the cycle, called the solar maximum. At this point, there could be as many as 250 sunspots or even clusters of sunspots across the Sun. Towards the end of the cycle, activity decreases back to a minimum, and then the cycle starts anew.
When will the Sun explode?
It never will. In about 5 billion years, the Sun will transform from a yellow dwarf to a red giant. As it runs out of hydrogen, its core will contract, heat up, and begin to use helium as fuel. This will cause the Sun to expand greatly, engulfing Mercury, Venus, and possibly the Earth.
After expanding to about 200 times its present size, the Sun's core will heat up to about 100 million K and begin the process of turning helium into carbon. This intense activity will cause the Sun to lose its outer layers, and the remaining core will collapse to become a white dwarf, similar in size to the Earth. Then, the white dwarf will slowly fade and enter its final phase as a dim, cool black dwarf.
Unlike humans, stars have well-defined and stable life cycles. Learn more about the lifespan of stars with our fun infographic.
Layers of the Sun
While the Sun might appear as a chaotic, boiling sphere, it is actually highly structured and composed of distinct layers, divided into inner and outer layers.
Inner layers:
- Core: The hottest part of the Sun, with temperatures reaching up to 15 million ° C (27 million ° F). It is the primary source of the Sun's energy.
- Radiation Zone: This layer is responsible for transferring energy from the core's nuclear reactions to the convection zone through radiation.
- Convection Zone: A layer in which energy is transported to the photosphere through convection currents of heated and cooled gases.
Outer layers:
- Photosphere: The apparent surface of the Sun, which emits most of the light that reaches the Earth directly.
- Chromosphere: A layer of plasma above the photosphere, characterized by features such as filaments and prominences. It has a red hue due to its high hydrogen content, visible at the edge of the Sun only during a total solar eclipse.
- Transition Region: A very thin layer, about 100 km thick, where the temperature sharply rises from 20,000 K in the upper chromosphere to over 2 million K in the corona.
- Corona: The Sun's outermost layer and its largest, least dense structure, consisting of plasma that escapes into space. The solar wind carries corona material into the interplanetary medium. The corona is visible from Earth only during a total solar eclipse.
How to observe the Sun?
Safety rules
First and foremost: Never look directly at the Sun or use equipment such as binoculars or telescopes without a special filter. Bright sunlight can damage your eyes or even cause blindness, especially when magnified by optical devices. Additionally, your optical equipment itself can be damaged if left unprotected. Even if the Sun is partially covered by clouds, it's still unsafe because ultraviolet and infrared rays can damage your retina. Also, never use ordinary sunglasses to look at the Sun. The only safe way to look directly at the Sun is to use specially-made solar filters. Or try indirect observations with a pinhole camera, which is easy to make at home.
When does the Sun rise and set today?
If you want to find out the sunrise and sunset times in your city or access more specific information like civil, astronomical, and nautical twilight times, check out the Sky Tonight app’s calendar. Open the Sky tab and choose your preferred display format (lines or circles). The times highlighted in blue are interactive – click on them to see what the sky will look like at that moment.
What can you see on the Sun?
If you have the proper equipment and follow all safety precautions, you're ready to observe these interesting features of the Sun:
- Sunspots are dark spots on the Sun caused by its magnetic field; they are the easiest to see.
- Granules look like tiny bubbles on the Sun’s surface and last about five to ten minutes. A high-power telescope will show them best.
- Prominences are beautiful, large loops of red gas that shoot out from the Sun. You can see them during a total solar eclipse or with a special H-alpha telescope.
- Filaments are similar to prominences but look like long dark threads against the brighter Sun’s surface. They also require a H-alpha telescope to observe.
- Sometimes, the inner planets Venus and Mercury transit in front of the Sun from our point of view. Venus transits are very rare, happening next in December 2117 and 2125. Mercury transits are more common, with the next ones on November 12-13, 2032, and November 7, 2039.
- Transits of the International Space Station (ISS) happen more often. You can use the ISS Transit Finder to know when you can see the ISS move across the Sun from your location.
In addition to the phenomena that can be observed on the Sun's surface, there are many beautiful atmospheric effects that are caused by the Sun. Check our article on daytime astronomy to find out what else you can see in bright sunlight.
What can you see on the Sun during a total solar eclipse?
In addition to the features mentioned above, during a total solar eclipse, you'll have a great opportunity to see the solar corona, the Sun's outermost atmospheric layer. Also, look for Baily's Beads and the Diamond Ring. Baily's Beads appear when the Moon nearly covers the Sun, with the last rays of sunlight passing through the Moon's mountains and valleys, forming a string of luminous spots. The Diamond Ring effect occurs when only one of these beads remains, shining like a diamond on a glowing ring.
F.A.Q.
Is the Sun a star?
The Sun is just a star, like billions of others in space. Check out our colorful infographic to learn what sets stars apart from planets.
Is every star a sun?
A star is considered a sun if it is at the center of a planetary system. Therefore, not all stars are suns, but there are many suns besides our own Sun.
What is the brightest star after the Sun?
The brightest star in the sky after the Sun is Sirius – the "Dog Star" in the constellation Canis Major.
Is the Earth getting closer to the Sun?
Sometimes the Earth gets closer to the Sun, and sometimes it's farther away. That's because the Earth travels in an elliptical orbit, with distances ranging from 147 to 152 million kilometers (91 to 94 million miles) from the Sun. The point where the Earth is closest to the Sun is called perihelion, and the farthest point is called aphelion.
When is the Sun the hottest?
On the Earth, the Sun feels hottest a few hours past noon because that's when the Sun's direct rays have had enough time to heat up the air. However, the actual temperature of the Sun doesn't change much at all. It varies by less than 0.2% over the course of the year, and these minor fluctuations don't really impact the warmth we feel here on the ground.
The Sun: bottom line
The Sun is a magnificent celestial body that not only sustains life on Earth but also provides a breathtaking view. So don't limit your skywatching to the night! Use Sky Tonight to find out the exact timing of astronomical, nautical, and civil twilight in your city. And discover the Sun’s full beauty, from the atmospheric phenomena created by its light to the sunspots dancing on the Sun’s surface.
