APOD: 2023 August 21 Б Introducing Comet Nishimura
21.08.2023

Will Comet Nishimura become visible to the unaided eye? Given the unpredictability of comets, no one can say for sure, but it currently seems like a good bet. The comet was discovered only ten days ago by Hideo Nishimura during 30-second exposures with a standard digital camera.

Venus On The Horizon
14.10.1997

The month of October features a sky full of planets, including Venus as the brilliant evening star. Besides the sun and moon, Venus is the brightest object visible in Earth's sky. This month, Venus appears in early evening near the red planet Mars and Mars' red giant rival Antares above the southwestern horizon.

Tyrrhenian Sea and Solstice Sky
20.12.2014

Today the solstice occurs at 23:03 Universal Time, the Sun reaching its southernmost declination in planet Earth's sky. Of course, the December solstice marks the beginning of winter in the northern hemisphere and summer in the south.

Saturn: Shadows of a Seasonal Sundial
12.10.2011

Saturn's rings form one of the larger sundials known. This sundial, however, determines only the season of Saturn, not the time of day. In 2009, during Saturn's last equinox, Saturn's thin rings threw almost no shadows onto Saturn, since the ring plane pointed directly toward the Sun.

Sigmoids Predict Solar Eruptions
16.03.1999

On the Sun, S marks the spot. Solar explosions have been discovered to explode preferentially from regions marked with this letter. The surface of the quiet Sun is a maze of hot gas and flowing magnetic fields. When two regions of high magnetic field strength approach each other, they typically pass uneventfully.

Southwest Mercury
13.02.2000

The planet Mercury resembles a moon. Mercury's old surface is heavily cratered like many moons. Mercury is larger than most moons but smaller than Jupiter's moon Ganymede and Saturn's moon Titan. Mercury is much denser and more massive than any moon, though, because it is made mostly of iron.

A Zodiacal Sky over Horseshoe Bend
22.05.2017

What's causing the unusual ray of white light extending upward from the central horizon? Dust orbiting the Sun. At certain times of the year, a band of sun-reflecting dust from the inner Solar System rises prominently before sunrise and is called zodiacal light.

APOD: 2024 December 3 Б Ice Clouds over a Red Planet
3.12.2024

If you could stand on Mars -- what might you see? You might look out over a vast orange landscape covered with rocks under a dusty orange sky, with a blue-tinted Sun setting over the horizon, and odd-shaped water clouds hovering high overhead.

APOD: 2025 December 28 Б NGC 1898: Globular Cluster in the Large Magellanic Cloud
28.12.2025

Jewels don't shine this bright -- only stars do. And almost every spot in this jewel-box of an image from the Hubble Space Telescope is a star. Now, some stars are more red than our Sun, and some more blue -- but all of them are much farther away.

Palm Tree Partial Eclipse
13.04.2024

Only those along the narrow track of the Moon's shadow on April 8 saw a total solar eclipse. But most of North America still saw a partial eclipse of the Sun. From Clearwater, Florida, USA this single snapshot captured multiple images of that more widely viewed celestial event without observing the Sun directly.