Blood moons only occur during total lunar eclipses, when the Earth blocks the sun, but its atmosphere lets redder parts of sunlight through to reflect off the lunar surface.

Because the half of Earth that faces the sun is larger than the area of the shadow cast by the moon during a solar eclipse, observers may experience a total, annular, or partial eclipse.

Solar eclipses are a cosmic coincidence because the moon is 400 times smaller than the sun but 400 times closer to Earth, allowing it to completely block sunlight.

See a lunar eclipse share the night sky with the Milky Way

Photos taken at the Cerro Tololo Inter-American Observatory in Chile in March 2025 captured a blood moon and the Milky Way galaxy within the same field of view. The moon appears red from the bluer parts of its reflected sunlight being scattered by Earth's atmosphere.

Although the moon passes between the sun and Earth monthly, its orbit is tilted by five degrees, preventing the planet from experiencing a solar eclipse each month.

Just before and just after a total solar eclipse, sunlight can pass through uneven terrain on the lunar surface, producing disconnected bits of light around the moon called Baily's beads.

Moon's visibility is determined by its declination, equivalent to Earth latitude

The Moon's declination varies between approximately +28.7 degrees and -28.7 degrees, ensuring it rises and sets between latitudes of approximately 61.3 degrees north and south. This means there are places on Earth where the Moon is never visible above the horizon and places where it temporarily does not set.

Over thousands of years, the frequency of solar eclipses is greatest around the Arctic and Antarctic Circles and lowest near the equator.

While the sun, moon, and stars rise and set from east to west due to Earth's rotation, the moon's eastward revolution around the Earth causes its shadow to move from west to east during a solar eclipse.

The moon's little-known, incredibly thin atmosphere

Earth's colorless, lifeless moon is often portrayed as devoid of an atmosphere. However, this fascinating article describes the very thin layer of gases floating above the surface of our celestial neighbor, a layer so thin it's technically known as...

View photographs of solar eclipses on Mars, Jupiter, and Saturn caused by the moons of these planets blocking sunlight.

Rayleigh scattering of light gives the atmosphere its blue skies and red sunsets

Light is deflected from its original path by atmospheric particles, where bluer light is scattered more than other colors. When the sun is at its highest point in the sky, it travels through the thinnest part of the atmosphere, scattering some blue light across the sky. A greater atmospheric path length at sunset scatters more colors, leaving only red, yellow, and orange.

Just as directly observing a solar eclipse without protective glasses can cause permanent eye damage, photographing an eclipse requires a specialized filter to prevent damaging your camera.

Moon 101: NASA's complete overview of our lunar companion

From modulating our tides to impact our climate, Earth's lone natural satellite plays a key role forming the planet's habitat. Before diving into the rest of the resources on this page, check out NASA's overview of the basics of the Moon—how it got its name, its size and distance from Earth, its structure, and much more.

While solar eclipses were considered ominous throughout history, multiple cultures explained the celestial event as the result of mythical creatures nearly consuming the sun.

All rainbows are 'raincircles' caused by water droplets separating white sunlight into a spectrum of colors, but Earth's surface blocks the bottom half of the circle from our line of sight.

Eclipse glasses protect the eyes from overexposure to the sun's ultraviolet and infrared radiation, as a person's instinct to look away from the sun is diminished when it's partly blocked.

Learn about the sun's corona, which is nonlethal despite a temperature of millions of degrees

The outermost layer of the sun's atmosphere is best seen during a solar eclipse, when the moon blocks the much brighter (and significantly cooler) solar surface. Despite the high-energy particles in the corona moving fast enough to escape the sun's gravity and gradually become solar wind, their density is too low to contribute meaningfully to the region's overall radiation.

The majority of exoplanets—planets outside the solar system—have been discovered through mini-eclipses created when they pass in front of their host star and block some of its light from reaching Earth.

How to sight the new crescent moon that starts Ramadan

Ramadan doesn't begin on a fixed date. Instead, it begins when a crescent moon is visually confirmed. The Royal Museums Greenwich explains the astronomy behind the sighting, including the conditions that must be met: the sun must be below the horizon, the moon must be above it, and the two must not be within the Danjon Limit (roughly 5 to 7 degrees of separation in the sky, as shown below).

Solar activity and the density and chemical composition of the air affect auroral colors

Oxygen atoms can emit red and green light when energized by collisions with the solar wind, but red takes longer to be emitted and is disrupted by bumping into other molecules. This causes red light to appear at higher altitudes, where the air is less dense. Higher-energy solar wind can penetrate to lower altitudes and collide with more abundant ionized nitrogen, which produces blue light.

The moon is moving 3.8 centimeters farther away from Earth each year

Driven by tidal forces, the effect is minimal and slow, ensuring stable tidal patterns and lunar cycles. Earth's rotation slows down as the Moon gains orbital momentum, slowly lengthening the day over time.

Photographer catches a 'once in a blue moon' shot

A rare "super blue moon" occurred in August 2023, a phenomenon which will not occur again until 2037. Photographer Andrew McCarthy caught a stunning image of the larger-than-normal orb with an ironic twist: a JetBlue flight silhouetted against the...

High solar activity can produce pink and purple auroras

Although less common, energetic enough charged particles from the sun that descend to an altitude of about 100 kilometers (62 miles) can strike a mixture of ionized and neutral nitrogen molecules, causing them to emit red and blue light, which our eyes perceive as purple.

Why time ticks faster on the moon, which may need its own time zone

Because Earth exerts a stronger gravitational pull than the moon, it lags behind between 56 and 59 microseconds each day, or about one second every 46.5 years. This impacts essential synchronous operations of future electronic equipment on the lunar surface, which could be alleviated by a standardized conversion system between Earth and moon time zones.

View the transparency of Earth's atmosphere and how it blocks most forms of light

The gases that make up Earth's atmosphere block most harmful forms of electromagnetic radiation from reaching the planet's surface, except for some ultraviolet light. Their transparency to radio waves means this form of light can reach Earth's surface, which is why most radio telescopes are ground-based rather than space-based.

How the moon creates tides

Anyone who has visited large bodies of water virtually anywhere on Earth notices low and high tides occur at regular intervals, a process primarily driven by the moon’s gravitational pull. This explainer details how the motion of the Earth and Moon interact to create tides.

Astronomers can identify systems with pairs of orbiting stars by observing recurring dips in the system's brightness as the stars eclipse one another.

In the third century BCE, the Greek astronomer Aristarchus of Samos estimated the distance to the moon using geometry after measuring the length of Earth's shadow during a lunar eclipse.

By separating light with tools such as prisms, scientists can reveal the presence and composition of celestial matter by identifying color fingerprints unique to specific elements and molecules.

Global eclipse tourism is a multibillion-dollar industry, with the 2024 total solar eclipse across North America estimated to have generated $6B in economic activity across regions along its path.

Breaking down sunlight and why the sun appears yellow despite emitting green light the most

This peak intensity is produced alongside a spectrum of other colors, which, when combined, make the sun appear white in space. Since Earth's atmosphere scatters bluer and greener wavelengths of light more than red and orange wavelengths, sunlight reaching Earth's surface appears yellow, while the sky appears blue. (Some readers may experience a paywall.)

Visualize the path of every solar eclipse from 1900 to 2099 and see what each looks like when observed from different locations on Earth.

The crew of Artemis II captured a photograph of Earth setting as they orbited the moon

On April 6, 2026, the Artemis II astronauts captured a striking image of Earth setting as their spacecraft orbited the Moon, echoing the iconic Earthrise photo taken by Apollo 8's Bill Anders 58 years earlier.

For the medievals, the moon was a versatile religious symbol

Within the distinct traditions of Christianity and Islam, the moon became a central metaphor and sign for religious teaching. For Christians, its light was used to explain Jesus' humanity with the light of the sun (divinity). For Muslims, the moon represented a cosmic longing for god.

While the leading hypothesis for the moon's origin involves a Mars-sized object called Theia striking ancient Earth and forming from the resulting debris, it cannot explain why lunar isotope abundances match Earth.