A Fading Moonset Over Hong Kong
15.12.2009

Do stars appear dimmer when nearer the horizon? Yes -- atmospheric air absorbs and reradiates light, so that the greater the airmass through which one peers, the fainter an object will appear. Pictured above in a multi-frame image, stars, the planet Jupiter, and even the Moon show the horizon-dimming effects of Earth's nearly-transparent atmosphere.

HESS Telescopes Explore the High Energy Sky
8.01.2019

They may look like modern mechanical dinosaurs but they are enormous swiveling eyes that watch the sky. The High Energy Stereoscopic System (H.E.S.S.) Observatory is composed of four 12-meter reflecting-mirror telescopes surrounding a larger telescope housing a 28-meter mirror.

Wonder and Mystery above the Very Large Telescopes
9.05.2011

What's that bright orange dot above the large telescope on the right? Even seasoned sky enthusiasts might ponder the origin of the orange orb seen by scrolling across this panoramic image, taken last December. Perhaps identifying known objects will help.

HESS Gamma Ray Telescope
6.09.2002

Most ground-based telescopes with lenses and mirrors are hindered by the Earth's nurturing, protective atmosphere that blurs images and scatters and absorbs light. But this telescope was designed to detect extreme gamma rays - photons with over 100 billion times the energy of visible light - and actually requires the atmosphere to operate.

APOD: 2023 September 6 Б HESS Telescopes Explore the High Energy Sky
6.09.2023

They may look like modern mechanical dinosaurs, but they are enormous swiveling eyes that watch the sky. The High Energy Stereoscopic System (H.E.S.S.) Observatory is composed of four 12-meter reflecting-mirror telescopes surrounding a larger telescope housing a 28-meter mirror.

Cosmic Rays from Galactic Centers
12.11.2007

Where do cosmic rays come from? A major step toward answering this century old question may have just come in from the Auger Observatory project, the world's premier cosmic ray observatory. That high energy fundamental particles are barreling through the universe has been known for about a century.

Tonight: A Blue Moon
31.07.2004

How often does a full moon occur twice in a single month? Exactly once in a Blue Moon. In fact, the modern usage of the term "Blue Moon" refers to the second Full Moon in a single month. Tonight's Blue Moon will be the first since November 2001.

NEAR to an Asteroid
15.02.1996

Excitement mounts as NASA's Near Earth Asteroid Rendezvous (NEAR) spacecraft nears launch - currently scheduled for 3:53 ET on February 16. NEAR's mission is to become the first spacecraft to rendezvous with and orbit an asteroid, the asteroid designated 433 Eros.

Almahata Sitta 15
28.03.2009

Small asteroid 2008 TC3 fell to Earth at dawn on October 7, 2008, tracking through the skies over the Nubian Desert in northern Sudan. That event was remarkable because it was the first time an asteroid was detected in space before crashing into planet Earth's atmosphere.

Mizar Binary Star
19.02.1997

Mizar (sounds like "My Czar") is a binary star. In fact, most stars are binary stars. In a binary star system, each star of the pair follows an elliptical orbital path. Mutual gravity causes...