A Sun Pillar Over Maine
2.01.2006

Have you ever seen a sun pillar? When the air is cold and the Sun is rising or setting, falling ice crystals can reflect sunlight and create an unusual column of light. Ice sometimes forms flat, stop-sign shaped crystals as it falls from high-level clouds.

To Scale: The Solar System
25.12.2015

Want to build a scale model Solar System? A blue marble 1.4 centimeters (about half an inch) across would be a good choice for a scale model Earth. Since the Sun is 109 times the diameter of Earth, a 1.5 meter diameter balloon could represent the Sun.

Stars Over Easter Island
12.10.2009

Why were the statues on Easter Island built? No one is sure. What is sure is that over 800 large stone statues exist there. The Easter Island statues, stand, on the average, over twice as tall as a person and have over 200 times as much mass.

Comet LINEAR Approaches
4.07.2000

Just possibly, a new comet may become bright enough to see without binoculars later this month. Comet C/1999 S4 LINEAR is rapidly approaching both the Earth and the Sun from the outer Solar System, and should be at its brightest around 2000 July 25 in the early evening sky of northern observers.

Oklo: Ancient African Nuclear Reactors
16.10.2002

The remnants of nuclear reactors nearly two billion years old were found in the 1970s in Africa. These reactors are thought to have occurred naturally. No natural reactors exist today, as the relative density of fissionable uranium has now decayed below that needed for a sustainable reaction.

Jupiter's Auroras
18.10.1996

Auroras are especially large on Jupiter. In pictures released yesterday, the Hubble Space Telescope imaged these unusual light displays in more detail than ever before. Jupiter's auroras are linked to its volcanic moon Io.

Evidence for Frame Dragging Black Holes
7.11.1997

Gravity can do more than floor you. According to recent measurements of a star system thought to contain a black hole, it can spin you too. This effect, called frame-dragging, is most prominent near massive, fast spinning objects. Now, a team led by W.

An Active Prominence on the Sun
18.06.2018

Sometimes the Sun's surface becomes a whirlwind of activity. Pictured is a time-lapse video of the Sun's surface taken over a two hour period in early May, run both forwards and backwards. The Sun's surface was blocked out so that details over the edge could be imaged in greater detail.

A Setting Sun Trail
29.07.2002

The Sun appears to move on the sky because the Earth rotates. The extreme brightness of the Sun, however, makes it difficult to capture a sun-trail -- the path the Sun traces on the sky.

Gamma Ray Sky Map
23.06.1995

What if you could "see" gamma rays? This computer processed image represents a map of the entire sky at photon energies above 100 million electron Volts. These gamma-ray photons are more than 40 million times more energetic than visible light photons and are blocked from the Earth's surface by the atmosphere.