Saturn in Blue and Gold
13.04.2014

Why is Saturn partly blue? The above picture of Saturn approximates what a human would see if hovering close to the giant ringed world. The above picture was taken in 2006 March by the robot Cassini spacecraft now orbiting Saturn. Here Saturn's majestic rings appear directly only as a thin vertical line.

Country Sky versus City Sky
8.04.2020

Dark skies are disappearing from the world. With modernization comes artificial lighting that brightens the night. While these lights allow modern humans to see, much light is wasted up into the sky. This light...

Behind Betelgeuse
11.05.2020

What's behind Betelgeuse? One of the brighter and more unusual stars in the sky, the red supergiant star Betelgeuse can be found in the direction of famous constellation Orion. Betelgeuse, however, is actually...

APOD: 2023 July 11 Б Sunspots on an Active Sun
11.07.2023

Why is our Sun so active now? No one is sure. An increase in surface activity was expected because our Sun is approaching solar maximum in 2025. However, last month our Sun sprouted more sunspots than in any month during the entire previous 11-year solar cycle -- and even dating back to 2002.

A High Energy Fleet
24.05.1998

Looking like a fleet of futuristic starcruisers, NASA's highly successful series of High Energy Astrophysical Observatory (HEAO) spacecraft appear poised over planet Earth. Labeled A, B, and C in this vintage illustration, the spacebased telescopes were known as HEAO-1, HEAO-2, and HEAO-3 respectively.

The Colorful Clouds of Rho Ophiuchi
9.07.2005

The many spectacular colors of the Rho Ophiuchi (oh'-fee-yu-kee) clouds highlight the many processes that occur there. The blue regions shine primarily by reflected light. Blue light from the star Rho Ophiuchi and nearby stars reflects more efficiently off this portion of the nebula than red light.

Saturn in Blue and Gold
3.05.2006

Why is Saturn partly blue? The above picture of Saturn approximates what a human would see if hovering close to the giant ringed world. The above picture was taken in mid-March by the robot Cassini spacecraft now orbiting Saturn. Here Saturn's majestic rings appear directly only as a thin vertical line.

A Dangerous Summer on HD 80606b
4.02.2009

On the distant planet HD 80606b, summers might be dangerous. Hypothetic life forms floating in HD 080606b's atmosphere or lurking on one of its (presently hypothetical) moons might fear the 1,500 Kelvin summer heat, which is hot enough not only to melt lead but also nickel.

A Flight of Helios
24.07.2011

An example of solar-powered flight, NASA's Helios aircraft flew almost one hundred years after the Wright brothers' historic flight on December 17, 1903. Pictured here at 3,000 meters in in skies northwest of Kauai, Hawaii, USA in August 2001, the remotely piloted Helios is traveling at about 40 kilometers per hour.

Water Vapor Discovered on Distant Exoplanet
17.09.2019

Where else might life exist? One of humanity's great outstanding questions, locating planets where extrasolar life might survive took a step forward recently with the discovery of a significant amount of water vapor in the atmosphere of distant exoplanet K2-18b.