Two Tails of Comet Lulin
24.02.2009

Go outside tonight and see Comet Lulin. From a dark location, you should need only a good star map and admirable perseverance -- although wide-field binoculars might help. Yesterday, Comet Lulin passed its closest to Earth, so that the comet will remain near its brightest over the next few days.

APOD: 2025 September 23 Б NGC 6357: Cathedral to Massive Stars
22.09.2025

How massive can a normal star be? Estimates made from distance, brightness and standard solar models had given one star in the open cluster Pismis 24 over 200 times the mass of our Sun, making it one of the most massive stars known.

Zooming in on the First Stars
10.06.2003

What became of the first stars? No known stars appear to be composed of truly primordial gas -- all of the stars around us have too many heavy elements. Our own Sun is thought to be a third generation star, with many second-generation stars seen in globular clusters.

Julius Caesar and Leap Days
28.02.2016

Today, February 29th, is a leap day - a relatively rare occurrence. In 46 BC, Julius Caesar, featured here in a self-decreed minted coin, created a calendar system that added one leap day every four years.

The 47 Ursae Majoris System
17.08.2001

Watching and waiting, astronomers have uncovered the presence of more than 70 planets orbiting stars other than the Sun. So far almost all these extrasolar planets have crazy elongated orbits, lie uncomfortably close to their parent stars, or are found in bizarre, inhospitable systems.

APOD: 2024 March 18 Б Comet Pons Brooks Swirling Coma
17.03.2024

A bright comet will be visible during next month's total solar eclipse. This very unusual coincidence occurs because Comet 12P/Pons-Brooks's return to the inner Solar System places it by chance only 25 degrees away from the Sun during Earth's April 8 total solar eclipse.

Zodiacal Light Panorama
5.04.2012

Sweeping from the eastern to western horizon, this 360 degree panorama follows the band of zodiacal light along the solar system's ecliptic plane. Dust scattering sunlight produces the faint zodiacal glow that spans...

APOD: 2025 June 21 Б Two Worlds, Two Analemmas
20.06.2025

Sure, that figure-8 shaped curve you get when you mark the position of the Sun in Earth's sky at the same time each day over one year is called an analemma.

Comet Halleys Nucleus: An Orbiting Iceberg
3.01.2010

What does a comet nucleus look like? Formed from the primordial stuff of the Solar System, comet nuclei were thought to resemble very dirty icebergs. But ground-based telescopes revealed only the surrounding cloud of gas and dust of active comets nearing the Sun, clearly resolving only the comet's coma, and the characteristic cometary tails.

APOD: 2026 March 20 Б Spring Equinox at Teide Observatory
19.03.2026

The defining astronomical moment of the equinox today is at 14:46 UTC (March 20). That's when the Sun crosses the celestial equator moving north in its yearly journey through planet Earth's sky, marking the beginning of spring for our fair planet in the northern hemisphere and fall in the southern hemisphere.