Autumn and the Active Sun
23.09.1998

As the Sun heads South, crossing the celestial equator today at 1:37 a.m. Eastern Time, Autumn begins for Earth's Northern Hemisphere. This Autumnal Equinox finds an increasingly active Sun steadily approaching a solar cycle maximum expected around the year 2003.

Antarctic Ozone Hole Widens
11.09.2000

It's back, and it's bigger than ever. The ozone hole that has been a cause of concern in recent years has again reformed over Earth's South Pole. The seasonal recurrence of the ozone hole was expected, although the size of the hole has never been so large this early in the season.

A Venus Landing
24.01.1999

This image is part of the first color panoramic view from Venus. It was transmitted by a TV camera on the Soviet Venera 13 lander which parachuted to thesurface on March 1, 1982. Venus...

Jyvцskylц in the Sky
25.01.2024

You might not immediately recognize this street map of a neighborhood in Jyvцskylц, Finland, planet Earth. But that's probably because the map was projected into the night sky and captured with an allsky camera on January 16. The temperature recorded on that northern winter night was around minus 20 degrees Celsius.

Mammatus Clouds Over Mexico
30.12.2007

Normal cloud bottoms are flat because moist warm air that rises and cools will condense into water droplets at a very specific temperature, which usually corresponds to a very specific height. After water droplets form that air becomes an opaque cloud.

Light from a Extra Solar Planet
5.04.2005

Light emitted by a planet far beyond our Solar System has been identified for the first time. The planet, illustrated in the above drawing, had its light detected by comparing the brightness of only...

Mammatus Clouds over Saskatchewan
11.08.2021

When do cloud bottoms appear like bubbles? Normally, cloud bottoms are flat. This is because moist warm air that rises and cools will condense into water droplets at a specific temperature, which usually corresponds to a very specific height. As water droplets grow, an opaque cloud forms.

A Giant Starspot on HD 12545
12.07.2000

What could cause a star to have such a large spot? Our Sun itself frequently has sunspots, relatively cool dark magnetic depressions that move across its surface. HD 12545, however, exhibits the largest starspots yet observed.

Mount Everest Star Trails
1.12.2018

The highest peak on planet Earth is framed in this mountain and night skyscape. On September 30, the digital stack of 240 sequential exposures made with a camera fixed to a tripod at an Everest Base Camp captured the sheer north face of the Himalayan mountain and foreground illuminated by bright moonlight.

The Weather on Mars
24.03.1997

Would Mars be a nice place to visit? Sometimes. Much of Mars undergoes severe changes in climate during its orbit around the Sun, ranging from extreme cold to temperatures enjoyable by humans. But Mars...