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Articles About Astronomy (106)

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. more

What is Local Mean Time (LMT)?

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? more

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. more

What's a Blood Moon?

Blood Moon may stem from the red glow a Full Moon gets when Earth casts a shadow on it. The term is sometimes used to describe 4 total lunar eclipses that occur in a row. more

11 Facts: Total Lunar Eclipse

The Sept 27/ 28, 2015 Total Lunar Eclipse is the final eclipse in a series of 4 total eclipses of the Moon called eclipses of the Blood Moon. more

Eclipse Magnitude

Eclipse magnitude is a number that astronomers associate with solar or lunar eclipses. What does it mean? more

DIY: Pinhole Projector

Make a simple pinhole projector using 2 pieces of card or paper to safely watch a projection of a solar eclipse. more

Mercury Transit

Local time for Mercury transit 11. / 12. November, 2019. Visible from most of the world. Will you be able to see it? Map of path and animation. more

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. more

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. more

What's 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. more

Solar Eclipses in History

Solar eclipses were historically viewed as omens that bring about death and destruction and people in many ancient civilizations tried their best to understand and predict them. more

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. more

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. more

Total Lunar Eclipses

A Total Lunar Eclipse happens when Earth's shadow blocks the direct light from the Sun reaching the Full Moon. more

Total Solar Eclipses

The total solar eclipse on August 21, 2017, has been nicknamed the Great American Eclipse as it will be visible all across the United States. more

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. more

The Moon Phases

There are 4 primary Moon phases and 4 intermediate phases. New Moon First Quarter Full Moon Third or Last Quarter Waxing and Waning Crescent Moon. more

When Is Fall Equinox?

The fall (autumnal) equinox in the Northern Hemisphere is in September. In the Southern Hemisphere, it's in March. more

December Solstice

The December solstice is also known as the summer solstice in the Southern Hemisphere and the winter solstice in the Northern Hemisphere. more

What Is June Solstice?

The June solstice is the longest day of the year in the Northern Hemisphere & the shortest day in the Southern Hemisphere. more

March Equinox

The March equinox around March 20-21 is the spring (vernal) equinox in the Northern Hemisphere and fall (autumnal) in the south. Night and day are nearly the same length. more

September Equinox

The Sun shines directly at the Equator on the September equinox and the length of day and night is nearly equal, but not quite. more

When Is Spring Equinox?

The Vernal (Spring) Equinox in the Northern Hemisphere is in March. In the Southern Hemisphere, it's in September. more

December Solstice Facts

10 things you may not know about the December Solstice, the shortest day of the year in the Northern Hemisphere. more

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? more

Asteroid to fly by Earth

At 7:24 PM UTC (19:24) on Friday, February 15, 2013, an asteroid called 2012 DA14, will come close to the Earth, closer than any other asteroid of similar size has ever come in recorded history. more

Asteroid 2004 BL86 to Fly By Earth

On Monday, January 26, 2015 asteroid 2004 BL86 flew by at only 3 times the distance of the Moon from the Earth. It will be the largest celestial body to come this close to Earth until 2027. more

Earth is Tilted

When an object the size of Mars crashed into the newly formed planet Earth around 4.5 billion years ago, it knocked it over and left it tilted at an angle. more

Dawn – Definition and Meaning

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. more

Dusk – Definition and Meaning

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. more

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. more

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? more

Equinox: Equal Day & Night?

Equinoxes don't have exactly 12 hours of day and night all over the world, like many believe. Such days do happen, but depend on the latitude of your city. more

Midnight Sun

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. more

What Are Moonbows?

Moonbows occur when the Moon’s light is reflected and refracted off water droplets in the air. more

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. more

Venus - Jupiter - Mars Conjunction

From time to time, some of the planets in our solar system are in conjunction and become visible together in the sky. Venus, Jupiter, Mars, and Mercury have all been visible in the early mornings of October 2015. more

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. more

What Causes Seasons?

Seasons change because Earth's rotational axis tilts away or towards the Sun during the course of a year. more

2017 Cosmic Calendar

List of cosmic events in 2017 including supermoons, solar and lunar eclipses, meteor showers, solstices, and equinoxes. more

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. more

Timekeeping by Stars

Out and about at night without a watch or a smartphone readily available? If you are in the Northern Hemisphere use the Big Dipper and the North Star to tell the time. more

A Year Is Never 365 Days

The definition of a tropical year is the time it takes the Earth to complete a full orbit around the Sun. It is approximately 365.242189 days long. more

June 5-6, 2012: Transit of Venus

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 May 2016. more

Zodiacal lights

Also known as false dawn, zodiacal lights are rare optical phenomena that occur around sunset and sunrise in early spring and late fall. more

What Is a Black Moon?

It can be the 3rd New Moon in a season of 4 New Moons or the 2nd New Moon in the same month or even no New Moon at all. more

Is a Blue Moon Blue?

A Blue Moon is a type of a Full Moon. It can also be a rare Moon that looks blue due to atmospheric dust particles. more

First Quarter Moon

The First Quarter Moon is a primary Moon phase when we can see exactly half of the Moon's surface illuminated. If it is the left or right half, depends on where you are on Earth. more

The Full Moon

The Full Moon is the moment the entire face of the Moon is illuminated by the Sun's rays. It is the 3rd primary phase. Each Full Moon has a name, except the Blue Moon. more

Full Moon names

Full Moons have ancient given names in many cultures. The North American Full Moon names mainly reflect the changing seasons and nature, like Strawberry, Snow, or Harvest Moon. more

The Lunar Month

A lunar month is the time it takes the Moon to pass through all of the Moon phases, usually measured from a New Moon the next New Moon. more

What Is Lunar Perigee and Apogee?

The Moon's orbit around Earth is elliptical. The point of the orbit closest to Earth is called perigee, while the point farthest from Earth is known as apogee. more

The New Moon

In modern astronomy, the New Moon is when the Sun and Moon are aligned, with the Sun and Earth on opposite sides of the Moon. The New Moon also has important cultural and religious significance worldwide. more

What Is a Supermoon?

A Supermoon happens when a Full Moon or New Moon coincides with the Moon's closest approach to Earth, its perigee. more

Third Quarter Moon

The Third or Last Quarter Moon is when the opposite half of the Moon is illuminated compared to the First Quarter. more

Waning Crescent Moon

During the Waning Crescent Moon phase, the illuminated part of the Moon decreases from a semicircle at Third Quarter until it disappears from view entirely at New Moon. more

Waning Gibbous Moon

The Waning Gibbous Moon is an intermediate Moon phase which starts after Full Moon and lasts until half of the Moon's surface is illuminated at Third Quarter Moon. more

Waxing Crescent Moon

Waxing Crescent Moon is an intermediate Moon phase which starts after New Moon and lasts until half of the Moon's surface is illuminated at First Quarter Moon. more

Waxing Gibbous Moon

The Waxing Gibbous Moon is an intermediate Moon phase which starts after the First Quarter Moon and lasts until the Full Moon. more

2013: Year of comets

2013 is going to be a good year for comet watchers, with at least 3 comets that may be visible without the aid of sophisticated equipment. more

What Are Comets?

Comets are small celestial bodies that orbit the Sun. Primarily made of dust and ice, many have a tail (coma) and are thought to be remnants of the formation of the Solar System. more

Eta Aquarid Meteor Shower

The Eta Aquarid meteor shower is expected to peak on May 5 and May 6, 2017. The Eta Aquarids is one of two meteor showers created by debris from Halley's Comet. more

2017 Geminids Meteor Shower

The Geminid meteor shower can be seen from December 4–16. In 2017, the shower will reach its peak around December 13. Local time and direction to see it. more

Meteor Showers

Dates and tips on how and where to see "shooting stars" from meteor showers all over the world. more

Perseid Meteor Shower

The 2017 Perseid meteor shower will peak on Aug 12 and 13. A waning gibbous Moon may make it harder for observers to see the celestial fireballs. more

2017 Quadrantids Meteor Shower

The 2017 Quadrantids meteor shower is expected to peak on January 4, 2017. Quadrantids, the first major shower of the year is best viewed from locations in the Northern Hemisphere. more

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