Journey to the Sun: The Life Cycle, Observation, and Fun Facts
The Sun is the most studied star in the universe, yet there's still so much to learn about it. 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
- Top 6 hottest questions about the Sun
- Life of the Sun
- Layers of the Sun
- How to observe the Sun?
How the Sun shapes our sky
- February 19: Venus at perihelion
- March 4: Mercury at perihelion
- March 8: Mercury at greatest elongation east
- March 12: Saturn at solar conjunction
- March 19: Neptune at solar conjunction
- March 20: March equinox
- March 23: Venus at inferior solar conjunction
- March 24: Mercury at inferior solar conjunction
- March 29: Partial solar eclipse
- April 16: Mars at aphelion
- April 17: Mercury at aphelion
- June 21: June solstice
- September 21: Partial solar eclipse
- September 22: September equinox
- December 21: December solstice
- 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
More facts about the Sun
- The Sun burns 4 million tons of its own mass every second.
- The Sun doesn't just quietly exist – it makes a ton of noise! But we can't actually hear it since there's no air in space to carry sound. The Sun’s “screams” are more like vibrations that scientists can pick up with special instruments.
- The Sun’s outer layer, the corona (up to 3 million°C), is actually much hotter than its surface (around 5,000°C).
- Auroras on Earth, known as the Northern and Southern Lights, are caused by the solar wind – charged particles from the Sun – interacting with Earth's magnetic field.
- Many cultures have viewed solar eclipses as ominous events. For example, in ancient China, people believed that an eclipse occurred because a giant dragon was eating the Sun. The people would make loud noises and bang pots and pans to scare the dragon away and protect the Sun.
Top 6 hottest questions about the Sun
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.
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.
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.
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.
How the Sun shapes our sky
Though the Sun is not safe to observe directly, it still plays a huge role in astronomical observations, enhancing the visibility of the planets during oppositions or obscuring them from view during solar conjunctions. Also, each planet in the Solar System has its own perihelion and aphelion, referring to the points where they are closest to and farthest from the Sun in space, respectively.
In addition, the interposition of the Sun and Earth in space determines the change of astronomical seasons: the equinox marks the beginning of spring and fall, and the solstice marks the beginning of winter and summer.
One of the most spectacular phenomena related to the Sun is the solar eclipse, which occurs when the Moon passes between the Earth and the Sun, temporarily blocking the Sun’s light. There are different types: total, where the Moon completely covers the Sun; partial, where only part of the Sun is obscured; and annular, where the Moon appears smaller, and a bright ring of the Sun is visible around it.
February 19: Venus at perihelion
On February 19, at 16:23 GMT, Venus will reach perihelion, meaning it will be at its closest to the Sun in space. The distance between the two bodies will be 0.72 AU. Venus's orbit is nearly circular, with its distance from the Sun varying by only about 1.5% between perihelion (closest approach) and aphelion (furthest point). As a result, its surface receives almost the same amount of energy from the Sun at both perihelion and aphelion. However, this event doesn’t affect the planet’s appearance in the sky: observe it after sunset in the constellation Pisces.
March 4: Mercury at perihelion
On March 4, at 13:45 GMT, Mercury will reach perihelion, meaning it will be at its closest to the Sun in space. The distance between the two bodies will be 0.31 AU. Although the event has an incredible effect on the planet’s surface temperatures, it makes no difference to Mercury’s appearance in the sky. Observe it before sunrise in the constellation Pisces.
March 8: Mercury at greatest elongation east
On March 8, at 01:41 GMT, Mercury will reach the farthest apparent distance from the Sun (18°12'). The greatest elongation is the best time to observe Mercury, as the elusive planet isn’t lost in the Sun’s glare. The planet will be shining brightly at a magnitude of -0.4. Observe it after sunset in the constellation Pisces.
March 12: Saturn at solar conjunction
On March 12, at 10:19 GMT, Saturn will pass behind the Sun as seen from Earth. In the sky, the planet will be at an angular distance of only 1°54'° from the Sun. During the solar conjunction, Saturn will be too close to the Sun to be safely observed. It will start to appear as a morning object in early May.
March 19: Neptune at solar conjunction
On March 19, Neptune will be at its closest point to the Sun in the sky. The planet will be only 1°15' from the Sun, which means that Neptune will be completely unobservable for several weeks, lost in the Sun's glare. In astronomy, solar conjunction is a celestial configuration in which an object has an elongation of nearly 0°, meaning it is at the same celestial longitude as the Sun. Learn more about this phenomenon in our dedicated article.
March 20: March equinox
On March 20, at 09:01 GMT, the Sun will be located directly above the equator, and both hemispheres will receive an almost equal amount of sunlight. The event is called an equinox. March equinox marks the beginning of astronomical spring in the Northern Hemisphere and the start of autumn in the Southern Hemisphere.
March 23: Venus at inferior solar conjunction
On March 23, at 01:26 GMT, Venus will pass between the Sun and the Earth. In the sky, the planet will be at an angular distance of only 8° from the Sun. During the solar conjunction, Venus will be too close to the Sun to be safely observed. It will start to appear as a “morning star” in a couple of days after the conjunction.
March 24: Mercury at inferior solar conjunction
On March 24, at 19:43 GMT, Mercury will pass in front of the Sun, as seen from the Earth. The apparent distance between the two celestial bodies will be 3°10'. The event is called inferior solar conjunction and occurs once in 130 days when the planet forms a straight line with the Sun and the Earth. For a few weeks, Mercury will be lost in the Sun’s glare. After that, it will reappear in the sky as a morning object. Avoid observing Mercury while it’s close to the Sun: it may result in permanent blindness.
March 29: Partial solar eclipse
On March 29, observers from east of North America, north of South America, Europe, western Russia, north of Asia, and north-western Africa will see a partial solar eclipse – the lunar disc will cover up to 93.8% of the Sun. The event will last from 08:50 to 12:43 GMT, with the maximum phase of the eclipse occurring at 10:47 GMT. Check the infographic about the upcoming eclipses for the visibility map and other details.
April 16: Mars at aphelion
On April 16, at 20:38 GMT, Mars will reach aphelion, meaning it will be at its farthest to the Sun in space. The distance between the two bodies will be 1.67 AU. Mars's orbit is significantly elliptical, with its distance from the Sun varying by about 20% between perihelion (closest approach) and aphelion (furthest point). As a result, Mars receives 31% less heat and light from the Sun at aphelion compared to perihelion. However, this event doesn’t affect the planet’s appearance in the sky: observe it after sunset in the constellation Cancer.
April 17: Mercury at aphelion
On April 17, at 13:32 GMT, Mercury will reach aphelion, meaning it will be at its farthest from the Sun in space. The distance between the two bodies will be 0.47 AU. Although the event has an incredible effect on the planet’s surface temperatures, it makes no difference to Mercury’s appearance in the sky. Observe it before sunrise in the constellation Pisces.
June 21: June solstice
On June 21, at 02:42 GMT, the Northern Hemisphere will reach its maximum tilt towards the Sun and experience the longest day and shortest night of the year. The Southern Hemisphere, in its turn, will get the shortest day and the longest night. This day will mark the beginning of an astronomical summer in the Northern Hemisphere and the start of an astronomical winter in the Southern Hemisphere.
September 21: Partial solar eclipse
On September 21, observers from Australia, New Zealand, Antarctica, and the Pacific Islands will see a partial solar eclipse – the lunar disc will cover up to 85.5% of the Sun. The event will last from 17:29 to 21:53 GMT, with the maximum phase of the eclipse occurring at 19:41 GMT. Check the infographic about the upcoming eclipses for the visibility map and other details.
September 22: September equinox
On September 22, at 18:19 GMT, the Sun will be located directly above the equator, and both hemispheres will receive an almost equal amount of sunlight. The event is called an equinox. September equinox marks the beginning of astronomical autumn in the Northern Hemisphere and the start of spring in the Southern Hemisphere.
December 21: December solstice
On December 21, at 15:03 GMT, the Southern Hemisphere will reach its maximum tilt towards the Sun and experience the longest day and shortest night of the year. The Northern Hemisphere, in its turn, will get the shortest day and the longest night. This day will mark the beginning of an astronomical summer in the Southern Hemisphere and the start of an astronomical winter in the Northern Hemisphere.
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.
Now that you've learned so much about the Sun, it's time to put your knowledge to the test! Are you ready to challenge yourself with our Solar Quiz? From the celestial mechanics behind solar eclipses to the unique orbits of the planets, let's see how well you really understand the star at the heart of our Solar System. Good luck!
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.
