Articles About Sun (68)
Twilight, dawn, & dusk
Learn more about different kinds of twilight, dawn and dusk.
2020 Cosmic Calendar
Astronomical events and highlights of 2020 and 2021 including supermoons, solar and lunar eclipses, meteor showers, solstices, and equinoxes.
The December solstice is the summer solstice in the Southern Hemisphere and the winter solstice in the Northern Hemisphere.
When Is Winter Solstice?
The Winter solstice in the Northern Hemisphere is in December, while in the Southern Hemisphere, it's in June.
What Causes Seasons on Earth?
Seasons change because Earth's rotational axis tilts away or towards the Sun during the course of a year.
The Sun shines directly on the Equator on the September equinox and the length of day and night is nearly equal, but not quite.
The June solstice is the longest day of the year in the Northern Hemisphere & 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. Why is that so? What is the definition of the golden hour? Explanation with 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.
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 marks the beginning of spring in the Northern Hemisphere. It is the Southern Hemisphere's autumnal/fall equinox.
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 Eclipses
A total lunar eclipse happens when Earth's shadow blocks the direct light from the Sun reaching the Full Moon.
When Is Spring Equinox?
The Vernal (Spring) Equinox in the Northern Hemisphere is in March. In the Southern Hemisphere, it's in September.
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?
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?
December Solstice Facts
10 things you may not know about the December Solstice, the shortest day of the year in the Northern Hemisphere.
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 Orbit & Solstice
Earth's closest approach to the Sun is 2 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 Is Summer Solstice?
The summer solstice in the Northern Hemisphere is in June, while in the Southern Hemisphere, it's in December.
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 sunset to nighttime, and the term is often used as another word for evening twilight. However, science defines dusk on the basis of the angle that the Sun makes with the horizon.
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 as the morning twilight brightens the sky. However, there is also a formal definition that refers to specific moments during that transition.
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 September Equinox Facts
10 things you may not know about the September Equinox.
Why 3 Shadows?
The Earth and the Moon cast 3 different shadows: umbra, penumbra, and antumbra. Why are there 3 types of shadows and how are they defined?
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. How is it defined? 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.
What Is a Partial Lunar Eclipse?
A partial lunar eclipse happens when the Earth moves between the Sun and the Moon, but they are not precisely aligned.
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.
When Mercury transits the Sun, you can see it as a tiny black dot silhouetted against the Sun's disk. The last Mercury transit was on November 11, 2019.
Midnight Sun, or polar day, means that at least a sliver of the Sun's disk is visible above the horizon 24 hours of the day.
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
A penumbral lunar eclipse occurs when the outer shadow of Earth falls on the Moon's face. It is easy to miss this type of lunar eclipse.
June Solstice Facts
11 things you may not know about the June Solstice.
Hybrid Solar Eclipse
A hybrid eclipse or annular/total eclipse starts as a total solar eclipse but changes into an annular solar eclipse. Why is that so? When is the next hybrid solar eclipse?
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.
Why does the sky turn red during sunrise and sunset?
Eclipse magnitude is a number that astronomers associate with solar or lunar eclipses. What does it mean?
Safely See a Solar Eclipse
Protect your eyes during a solar eclipse. Sunglasses don't work.
March Equinox Facts
On Sat, March 20, 2021, day and night will be of almost equal duration in most time zones in the world.
Make a Box Pinhole Projector
Instructions on how to DIY a pinhole projector using a cardboard box and household items to safely see a solar eclipse.
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
It takes both skill and good equipment to photograph a lunar eclipse aka a Blood Moon. Here are a few tips to help you on your way.
Solar Eclipse Photography
It takes some skill and some extra equipment to take dramatic pictures of a solar eclipse. But it is possible to capture the mood even with a simple cell phone camera.
What Are Rainbows?
When sunlight hits water droplets, we see a rainbow. How does it work?
Sunrise and Sunset Photography
Use your smartphone to take impressive pictures during sunrise and sunset.