Black Holes Are Black
19.01.2001

Q: Why are black holes black? A: Because they have an event horizon. The event horizon is that one-way boundary predicted by general relativity beyond which nothing, not even light, can return. X-ray astronomers...

APOD: 2025 June 20 Б Major Lunar Standstill 2024 2025
20.06.2025

Edmonton, Alberta, Canada, planet Earth lies on the horizon. in this stack of panoramic composite images. In a monthly time series arranged vertically top to bottom the ambitious photographic project follows the annual north-south swing of sunrise points, from June solstice to December solstice and back again.

The Road and the Milky Way
11.06.2022

At night you can follow this road as it passes through the Dark Sky Alqueva reserve not too far from Alentejo, Portugal. Or you could stop, look up, and follow the Milky Way through the sky. Both stretch from horizon to horizon in this 180 degree panorama recorded on June 3.

Night of the Long Leonid
22.11.2012

A cosmic grain of sand left the long and colorful trail across this all-sky view. Its grazing impact with planet Earth's atmosphere began at 71 kilometers per second. With the Milky Way stretching...

Crepuscular Moon Rays over Denmark
27.07.2022

This moon made quite an entrance. Typically, a moonrise is quiet and serene. Taking a few minutes to fully peek above the horizon, Earth's largest orbital companion can remain relatively obscure until it rises high in the nighttime sky.

The Belt of Venus
10.11.1999

Although you've surely seen it, you might not have noticed it. During a cloudless twilight, just before sunrise or after sunset, part of the atmosphere above the horizon appears slightly off-color, slightly pink.

Touran Sunrise
23.03.2007

Clouds covered the eastern horizon on Monday, when the Sun rose over the expansive Touran Wildlife Reserve in northeastern Iran. Of course, on that day the Moon rose with the Sun, creating a widely enjoyed partial solar eclipse.

Pluto in True Color
10.09.2019

What color is Pluto, really? It took some effort to figure out. Even given all of the images sent back to Earth when the robotic New Horizons spacecraft sped past Pluto in 2015, processing these multi-spectral frames to approximate what the human eye would see was challenging.

Aurora Over Greenland
23.08.2011

This aurora arched from horizon to horizon. During the current Shelios expedition to observe and learn about the northern lights, the sky last weekend did not disappoint. After sunset and some careful photographic planning, the above image was taken from the expedition's Qaleraliq campsite in southern Greenland.

Eclipse on a Polar Day
10.12.2021

During polar day, in Arctic and Antarctic summer, the Sun stays above the horizon for periods of 24 hours or more. Recorded on December 4, this fisheye timelapse image tracks the Sun in multiple frames as it completes a circle in the summer sky above Union Glacier, Antarctica.