Analemma over Taipei
21.06.2022

Does the Sun return to the same spot on the sky every day? No. A better and more visual answer to that question is an analemma, a composite of images taken at the same time and from the same place over the course of a year.

APOD: 2025 November 12 Б A Super Lunar Corona
12.11.2025

What are those colorful rings around the Moon? A corona. Rings like this will sometimes appear when the Moon is seen through thin clouds. The effect is created by the diffraction of light around individual, similarly-sized water droplets in an intervening but mostly transparent cloud.

A Mercury Transit Sequence
27.05.2003

Earlier this month, the planet Mercury crossed the face of the Sun, as seen from Earth. Because the plane of Mercury's orbit is not exactly coincident with the plane of Earth's orbit, Mercury usually appears to pass over or under the Sun.

Filaprom on the Western Limb
24.06.2022

A solar filament is an enormous stream of incandescent plasma suspended above the active surface of the Sun by looping magnetic fields. Seen against the solar disk it looks dark only because it's a little cooler, and so slightly dimmer, than the solar photosphere.

The Equal Night
20.03.2005

Today, the Sun crosses the celestial equator heading north, marking the Vernal Equinox -- the first day of spring in the Northern Hemisphere and autumn in the south. Equinox means equal night and with the Sun on the celestial equator, Earthlings will experience 12 hours of daylight and 12 hours of darkness.

APOD: 2025 January 1 Б Alpha Centauri: The Closest Star System
1.01.2025

The closest star system to the Sun is the Alpha Centauri system. Of the three stars in the system, the dimmest -- called Proxima Centauri -- is actually the nearest star. The bright stars Alpha Centauri...

Looking Sideways from the Parker Solar Probe
9.12.2019

Everybody sees the Sun. Nobody's been there. Starting in 2018 though, NASA launched the robotic Parker Solar Probe (PSP) to investigate regions near to the Sun for the first time. The PSP's looping orbit brings it yet closer to the Sun each time around -- every few months.

Venus on the Horizon
19.06.1999

Venus can appear as a brilliant evening star. Besides the sun and moon, Venus is the brightest object visible in Earth's sky. Because it is closer to the sun than Earth, Venus never...

A Moon Dressed Like Saturn
16.03.2020

Why does Saturn appear so big? It doesn't -- what is pictured are foreground clouds on Earth crossing in front of the Moon. The Moon shows a slight crescent phase with most of its surface visible by reflected Earthlight known as ashen glow.

Launch of the Parker Solar Probe
15.08.2018

When is the best time to launch a probe to the Sun? The now historic answer -- which is not a joke because this really happened this past weekend -- was at night. Night, not only...