September s Aurora
23.09.2011

September's equinox arrives today at 0905 UT. As the Sun crosses the celestial equator heading south, spring begins in the southern hemisphere and autumn in the north. And though the seasonal connection is still puzzling, both spring and autumn bring an increase in geomagnetic storms.

Sun and Winter Solstice 1996
21.12.1996

Today is the Winter Solstice for 1996. After steadily sinking in Northern Hemisphere skies, the Sun is now at its lowest declination - marking the first day of Northern Winter (but Southern Summer!). The Earth...

Fire on Earth
21.11.2000

Sometimes, regions of planet Earth can be seen lit up with fire. Since fire is the rapid acquisition of oxygen, and since oxygen is a key indicator of life, fire on any planet would be an indicator of life on that planet.

Perihelion and Aphelion
3.07.2009

This year Aphelion, the point in Earth's elliptical orbit when it is farthest from the Sun, occurs tomorrow, July 4th. Of course, that doesn't affect the seasons on our fair planet. Those...

APOD: 2023 June 21 Б Three Sun Paths
21.06.2023

Does the Sun follow the same path every day? No. The Sun's path changes during the year, tracing a longer route during the summer than the winter. Pictured here...

A Picturesque Equinox Sunset
20.03.2022

What's that at the end of the road? The Sun. Many towns have roads that run east - west, and on two days each year, the Sun rises and sets right down the middle. Today is one of those days: an equinox.

A Martian Autumn Begins
23.09.1997

Today is the first day of Autumn in the Northern Hemisphere of Planet Earth. The Autumnal Equinox occured yesterday at 7:56 pm EDT as the Sun crossed the celestial equator from North to South.

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.

Sunrise Solstice over Stonehenge
20.06.2021

Today the Sun reaches its northernmost point in planet Earth's sky. Called a solstice, many cultures mark this date as a change of seasons -- from spring to summer in Earth's Northern Hemisphere and from fall to winter in Earth's Southern Hemisphere.

A Nibble on the Sun
14.07.2018

The smallest of the three partial solar eclipses during 2018 was just yesterday, Friday, July 13. It was mostly visible over the open ocean between Australia and Antarctica. Still, this video frame...