Articles About Sun (80)
Twilight, dawn, & dusk
Learn more about different kinds of twilight, dawn and dusk.
Astro Events 2024–2025
When, where, and how to see things happening in the sky and space.
December Solstice
December solstice marks the shortest day north of the equator and the longest day in the south.
When Does Winter Start?
The first day of winter in the Northern Hemisphere is in December; south of the equator, it is in June. Find out exactly when the winter season starts.
What Causes Seasons on Earth?
Seasons change because Earth's rotational axis tilts away or towards the Sun during the course of a year.
September Equinox
The Sun shines directly on the Equator on the September equinox and the length of day and night is nearly equal, but not quite.
June Solstice 2025
The June solstice is the longest day of the year in the Northern Hemisphere and the shortest day in the Southern Hemisphere.
What Causes Tides?
The gravitational pull of the Moon and the Sun makes the water in the oceans bulge, causing a continuous change between high and low tide.
The Golden Hour – When Sunlight Turns Magical
When the Sun is close to the horizon, its light appears warmer and softer. Explore the definition of the golden hour, along with helpful photography tips.
Solar and Lunar Eclipses
Solar and lunar eclipses, why they occur, when the next eclipse is, and from where you can see them.
Magnetic Declination
A compass needle doesn't point to the geographical North Pole but to magnetic north. Did you know that it usually doesn't point to the magnetic North Pole either?
March Equinox
At the March equinox, the Sun crosses the equator from south to north. Explanation and 2025 equinox date.
Civil Twilight – Civil Dawn & Dusk
Civil twilight is the brightest of the twilight phases. How is it defined and when does it start and end? What are civil dawn and civil dusk?
Total Solar Eclipse
Total solar eclipses occur when the New Moon comes between the Sun and Earth and casts the darkest part of its shadow, the umbra, on Earth.
Northern and Southern Lights
What causes these colorful and dramatic light displays in the sky, and when and from where can you see them?
What Is Solar Noon?
Noon is at 12 o'clock but solar noon can be at a different time. What's the difference between the two?
Nautical Twilight – Nautical Dawn & Dusk
Nautical twilight is the second twilight phase. How is it defined and when does it start and end? What are nautical dawn and nautical dusk?
Total Lunar Eclipse
What happens when the Earth’s dark, reddish shadow covers the Moon completely?
When Does Spring Start?
The first day of spring is at the vernal equinox, when day and night are equal. Find out the exact time and date.
Equation of Time
The difference between the time measured by the Sun and the time measured by our clocks is known as the equation of time.
Astronomical Twilight – Astronomical Dawn & Dusk
Astronomical twilight is the darkest of the twilight phases. How is it defined and when does it start and end? What are astronomical dawn and astronomical dusk?
10 Facts about the December Solstice
Here are 10 things about the December solstice you might not know.
What Is a Solar Eclipse?
Solar eclipses happen when the Moon moves between Sun and Earth, blocking the Sun's rays and casting a shadow on Earth.
Earth's Perihelion
Earth's closest approach to the Sun is two weeks after the December solstice is a coincidence and has no special significance.
Equinox: Equal Day & Night?
Equinoxes don't have exactly 12 hours of day and night all over the world, like many believe. Such days, called equilux, do occur, but depend on your location.
Lunar Eclipse: Red Moon
Find out why a totally eclipsed Moon turns a shade of red.
Astronomical Glossary - Terms & Definitions
What do astronomers really mean when they use those technical terms?
Solar Eclipse Myths
The solar eclipse has inspired many mythical stories and influenced human behavior. Even today, eclipses of the Sun are considered bad omens in many cultures.
What Is Universal Time?
Universal Time is a solar time standard used in astronomy and to define time on Earth. How is it measured? What's the difference between UT, UT0, UT1, UT2, and UTC?
When Does Summer Start?
When is the summer solstice 2024 and 2025 in the southern and northern hemispheres?
How Often Do Solar Eclipses Happen?
There are between 2 and 5 solar eclipses every year, each one visible only in a limited area.
What Is Local Mean Time?
Use a sundial to determine the time of day and you will probably be off by a few minutes. That's where LMT comes into play. How is it measured and what is it used for?
Annular Solar Eclipse
An annular solar eclipse is when the Moon moves in front of the Sun but leaves the outer edge of the Sun visible as a ring of fire.
What Is the Umbra?
The umbra is the dark center portion of a shadow. The Moon's umbra causes total solar eclipses, and the Earth's umbra is involved in total and partial lunar eclipses.
What Is Dusk?
Dusk generally refers to the transition from day to night. However, the scientific definition is more specific and consists of three stages of dusk.
Watching Lunar Eclipses
A lunar eclipse can be seen with the naked eye, unlike solar eclipses, which have special safety requirements.
Partial Solar Eclipse
A partial solar eclipse happens when the Moon only partially covers the Sun.
What Is Dawn?
Dawn generally refers to the transition from night to day. However, the scientific definition refers to three separate and definable stages of dawn.
Altitude & Azimuth: The Horizontal Coordinate System
Learn how to use altitude (elevation) and azimuth angles to locate any object in the sky, such as stars, planets, satellites, the Sun, or the Moon.
10 Facts about the September Equinox
10 things you may not know about the September equinox.
Shadow Science
There are three kinds of shadows that produce eclipses.
Solar Eclipses in History
Solar eclipses were historically seen as omens that bring about death and destruction. People in many ancient civilizations tried their best to understand them.
The Blue Hour
The blue hour in the morning and evening is a favorite with photographers. When does it start & end? Explanation with times, degrees & photography tips.
Halos, Sundogs and Light Pillars
These are atmospheric phenomena created by the reflection and refraction of light by ice crystals in the atmosphere.
Partial Lunar Eclipse
What happens when the Earth’s dark shadow covers part of the Moon’s face?
What Is the Penumbra?
The penumbra is the lighter outer part of a shadow. The Moon's penumbra causes partial solar eclipses, and the Earth's penumbra is involved in penumbral lunar eclipses.
Mercury Transit
When Mercury transits the Sun, you can see it as a tiny black dot silhouetted against the Sun's disk.
Midnight Sun
The Midnight Sun is where the Sun never sets over a period of 24 hours or more. It occurs in polar regions during summer.
What Are Polar Nights?
A Polar Night is a night that lasts for at least 24 hours. It's the opposite of Midnight Sun / Polar Day.
Make a Pinhole Projector
Make a simple pinhole projector using 2 pieces of card or paper to safely watch a projection of a solar eclipse.
What Is the Antumbra?
The antumbra is the lighter part of a shadow that forms at a certain distance from the object casting the shadow. It is involved in annular solar eclipses and planet transits.
Penumbral Lunar Eclipse
What happens when the Earth’s lighter, outer shadow covers the Moon?
10 Facts about the June Solstice
10 things you may not know about the June solstice.
Hybrid Solar Eclipse
A hybrid solar eclipse or annular/total eclipse changes from a total to an annular eclipse. Why is that so? When is the next hybrid eclipse?
Solar Analemma
A Solar Analemma is a graph showing the position of the Sun in the sky above a single location at the same time of the day throughout the course of a year.
Rayleigh Scattering
Why does the sky turn red during sunrise and sunset?
Eclipse Magnitude
Learn more about the number that tells us how deep an eclipse will be.
Protect Your Eyes!
Never look directly at the Sun without proper protection.
10 Facts about the March Equinox
On this date, day and night are of almost equal duration around the world.
Make a Box Pinhole Projector
You’ll need a cardboard box, plus a few other household items.
Make a Solar Eclipse Projector
Make a Sun projector a pair of binoculars or a telescope to safely watch solar eclipses or a planet transit.
June Solstice Traditions
In many Northern Hemisphere cultures, the June solstice is associated with holidays, feasts and celebrations.
What Is Earthshine?
Earthshine is a dull glow that occurs when the Sun’s light reflects off the Earth's surface and illuminates the unlit portion of the Moon.
Transit of Venus: June 5-6, 2012
The 2012 Venus transit was the last chance to see this phenomenon for over 100 years. Mercury transits happen more often, the next one in 2032.
Lunar Eclipse Photography
Planning to take pictures of a lunar eclipse? Follow our guide for amazing eclipse photos! We tell you what kind of equipment you need and how to use it.
Solar Eclipse Photography
Take that perfect solar eclipse photo with your camera and some extra equipment, or capture it with your mobile phone.
Sunlight through valleys
Read more about Baily’s beads.
A jewel in the sky
Read more about the diamond ring.
How to Make the Best Use of Solar Eclipse Glasses
Learn the four basic rules for using eclipse glasses to make the most of viewing a solar eclipse while maintaining your eye safety.
Eclipse Seasons
Roughly speaking, there are two eclipse seasons per year. Each season contains different kinds of eclipses to the last one.
Holidays Connected to Astronomic Events
People worldwide mark the movement of celestial bodies with a wide variety of celebrations and rituals. We list the most important astronomical holidays.
Equation of Time
Why doesn't the year's earliest sunset occur on the winter solstice, even though it is the shortest day of the year in terms of daylight?
What Are Rainbows?
When sunlight hits water droplets, we see a rainbow. How does it work?
Sunset and Sunrise Photography
The secrets of how to use your cellphone to take impressive pictures during sunrise and sunset.
The Solar System
Everything that orbits the Sun is part of the solar system.
The Sun: Our Home Star
Energy from the Sun reaches Earth in the form of solar radiation, or sunlight.
What Are Sunspots?
If you look at the Sun with a telescope, using a solar filter, you may see some dark spots on the Sun's surface. What are sunspots, and how do they form?
99% of Earthlings See Sunlight on July 8 (And on Other Dates, Too)
Our Sun data confirm an internet meme claiming 99% of the world’s population gets sunlight at 11:15 UTC on July 8. But does it happen on other dates, too?
99% Of Us See Daylight at This Moment (Or Do We?)
Is it really true that 99% of the world's population see daylight at 11:15 UTC on July 8?
Dec 6: Minute of Global Darkness
There's a moment each year when almost 9 in 10 people worldwide experience night.