APOD: 2025 September 18 Б Comet C/2025 R2 SWAN
17.09.2025

A new visitor from the outer Solar System, comet C/2025 R2 (SWAN) also known as SWAN25B was only discovered late last week, on September 11. That's just day before the comet reached perihelion, its closest approach to the Sun.

A Spiral Galaxy Gallery
9.04.1996

A progression of beautiful spiral galaxies is illustrated above with three photographs from NASA's Ultraviolet Imaging Telescope (UIT). Flying above the Earth's obscuring layer of atmosphere on the Space Shuttle Columbia during...

A Quasar Portrait Gallery
24.11.1996

QUASARs (QUASi-stellAR objects) lie near the edge of the observable Universe. Discovered in 1963, astronomers were astounded - to be visible at such extreme distances of billions of light-years they must emit prodigious amounts of energy. Where does the energy come from?

Martian Analemma
26.06.2003

On planet Earth, an analemma is the figure-8 loop you get when you mark the position of the Sun at the same time each day throughout the year. But similarly marking the position...

TRACE and the Active Sun
15.05.1998

This dramatic high resolution picture looking across the edge of the Sun was taken April 24th by a telescope on board the newly launched Transition Region and Coronal Explorer (TRACE) satellite. It shows graceful arcs of intensely hot gas suspended in powerful looping magnetic fields which soar above a solar active region.

The VLT Interferometric Array
8.03.1999

The Very Large Telescope (VLT) Interferometric Array will be able to act as individual telescopes or as one huge telescope. Of the four planned VLTs in Chile, two have now reached completion. The first VLT to operate is visible on the left of the above photograph and was recently given the name Antu.

Our Busy Solar System
18.03.2006

Our Solar System is a busy place. Although the major planets get the most press, a swarm of rocks, comets, and asteroids also exist. The above plot shows the placement of known inner Solar System objects on 2002 July 20. The light blue lines indicate the orbits of planets.

Halloween and the Ghost Head Nebula
30.10.2007

Halloween's origin is ancient and astronomical. Since the fifth century BC, Halloween has been celebrated as a cross-quarter day, a day halfway between an equinox (equal day / equal night) and a solstice (minimum day / maximum night in the northern hemisphere). With our modern calendar, however, the real cross-quarter day will occur next week.

Beautiful Spiral NGC 7331
22.10.2008

A favorite target for astronomers, big, beautiful spiral galaxy NGC 7331 is one of the brighter galaxies not found in Charles Messier's famous 18th century catalog. About 50 million light-years distant...

Halo of the Cat s Eye
31.08.2012

The Cat's Eye Nebula (NGC 6543) is one of the best known planetary nebulae in the sky. Its haunting symmetries are seen in the very central region of this tantalizing image, processed to reveal the enormous but extremely faint halo of gaseous material, about 6 light-years across, which surrounds the brighter, familiar planetary nebula.