The USNO Millennium Time Ball
29.10.1999

In the nineteenth century, dropping a time ball from a prominent location was a practical way of communicating the time to the surrounding country side and ships at sea. Initiating a fledgling time service for the United States, the U.S. Naval Observatory dropped a time ball at precisely noon every day begining in 1845.

The Dark Horsehead Nebula
29.12.2000

While drifting through the cosmos, sculpted by stellar winds and radiation, this magnificent interstellar dust cloud has chanced to assume a recognizable shape. Fittingly named The Horsehead Nebula it is embedded in the immense complex of star forming gas and dust surrounding the Orion Nebula some 1,500 light-years distant.

VDB 142 in Cepheus
11.10.2001

A gorgeous collection of dust and gas nebulae in the Northern Milky Way graces the high and far off constellation of Cepheus. With colors based on astronomical filters, this close up of the region highlights stars embedded in curiously shaped cosmic clouds.

Peculiar Arp 295
10.10.2003

A spectacular bridge of stars and gas stretches for nearly 250,000 light-years and joins this famous peculiar pair of galaxies cataloged as Arp 295. The cosmic bridge between the galaxies and the long...

Crosby Ramsey Memorial Observatory Refractor
14.01.1999

The Massachusetts-based firm of Alvan Clark and Sons became famous for making telescope optics near the end of the last century. Near the end of this century, major astronomical observatories still boast of telescopes...

Startling Star V838 Mon
5.12.2003

Variable star V838 Monocerotis startled astronomers in January of 2002, undergoing a dramatic outburst like no other variable star known. Followed closely by ground-based instruments and the Hubble Space Telescope over the following months...

Charon: Moon of Pluto
3.06.2023

A darkened and mysterious north polar region known to some as Mordor Macula caps this premier high-resolution view. The portrait of Charon, Pluto's largest moon, was captured by New Horizons near the spacecraft's closest approach on July 14, 2015.

Charon: Moon of Pluto
6.07.2018

A darkened and mysterious north polar region known to some as Mordor Macula caps this premier high-resolution view. The portrait of Charon, Pluto's largest moon, was captured by New Horizons near the spacecraft's closest approach on July 14, 2015.

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...

Deimos: A Small Martian Moon
2.09.2001

Mars has two tiny moons, Phobos and Deimos. Pictured above is Deimos, the smaller moon of Mars. In fact, Deimos is one of the smallest known moons in the Solar System measuring only nine miles across.