Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2022 July 25

Find the New Moon

Image Credit & Copyright: Mohamad Soltanolkotabi

Explanation: Can you find the Moon? This usually simple task can be quite difficult. Even though the Moon is above your horizon half of the time, its phase can be anything from crescent to full. The featured image was taken in late May from Sant Martí d’Empúries, Spain, over the Mediterranean Sea in the early morning. One reason you can’t find this moon is because it is very near to its new phase, when very little of the half illuminated by the Sun is visible to the Earth. Another reason is because this moon is near the horizon and so seen through a long path of Earth’s atmosphere — a path which dims the already faint crescent. Any crescent moon is only visible near the direction the Sun, and so only locatable near sunrise or sunset. The Moon runs through all of its phases in a month (moon-th), and this month the thinnest sliver of a crescent — a new moon — will occur in three days.

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2022 July 24

Saturn in Infrared from Cassini

Image Credit: NASA, JPL-Caltech, SSI; Processing: Maksim Kakitsev

Explanation: Many details of Saturn appear clearly in infrared light. Bands of clouds show great structure, including long stretching storms. Also quite striking in infrared is the unusual hexagonal cloud pattern surrounding Saturn‘s North Pole. Each side of the dark hexagon spans roughly the width of our Earth. The hexagon‘s existence was not predicted, and its origin and likely stability remains a topic of research. Saturn’s famous rings circle the planet and cast shadows below the equator. The featured image was taken by the robotic Cassini spacecraft in 2014 in several infrared colors. In 2017 September, the Cassini mission was brought to a dramatic conclusion when the spacecraft was directed to dive into ringed giant.

Explore Your Universe: Random APOD Generator

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2022 July 23

Apollo 11 Landing Panorama

Neil Armstrong, Apollo 11, NASA

Explanation: Have you seen a panorama from another world lately? Assembled from high-resolution scans of the original film frames, this one sweeps across the magnificent desolation of the Apollo 11 landing site on the Moon’s Sea of Tranquility. The images were taken by Neil Armstrong looking out his window of the Eagle Lunar Module shortly after the July 20, 1969 landing. The frame at the far left (AS11-37-5449) is the first picture taken by a person on another world. Toward the south, thruster nozzles can be seen in the foreground on the left, while at the right, the shadow of the Eagle is visible to the west. For scale, the large, shallow crater on the right has a diameter of about 12 meters. Frames taken from the Lunar Module windows about an hour and a half after landing, before walking on the lunar surface, were intended to initially document the landing site in case an early departure was necessary.

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2022 July 22

Spiral Galaxy M74: A Sharper View

Image Credit: NASA, ESA, CSA, STScI; Processing Copyright: Robert Eder

Explanation: Beautiful spiral galaxy Messier 74 (also known as NGC 628) lies some 32 million light-years away toward the constellation Pisces. An island universe of about 100 billion stars with two prominent spiral arms, M74 has long been admired by astronomers as a perfect example of a grand-design spiral galaxy. M74’s central region is brought into a stunning, sharp focus in this recently processed image using publicly available data from the James Webb Space Telescope. The colorized combination of image data sets is from two of Webb’s instruments NIRcam and MIRI, operating at near- and mid-infrared wavelengths. It reveals cooler stars and dusty structures in the grand-design spiral galaxy only hinted at in previous space-based views.

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2022 July 21

Messier 10 and Comet

Image Credit & Copyright: German Penelas Perez

Explanation: Imaged on July 15 2022, comet C/2017 K2 (PanSTARRS) had a Messier moment, sharing this wide telescopic field of view with globular star cluster Messier 10. Of course M10 was cataloged by 18th century comet hunter Charles Messier as the 10th object on his list of things that were definitely not comets. While M10 is about 14 thousand light-years distant, this comet PanSTARRS was about 15 light-minutes from our fair planet following its July 14 closest approach. Its greenish coma and dust tail entertaining 21st century comet watchers, C/2017 K2 is expected to remain a fine telescopic comet in northern summer skies. On a maiden voyage from our Solar System’s remote Oort Cloud this comet PanSTARRS was discovered in May 2017 when it was beyond the orbit of Saturn. At the time that made it the most distant active inbound comet known. Its closest approach to the Sun will be within 1.8 astronomical units on December 19, beyond the orbital distance of Mars.

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2022 July 20

Jupiter and Ring in Infrared from Webb

Image Credit: NASA, ESA, CSA, STScI; Processing & License: Judy Schmidt

Explanation: Why does Jupiter have rings? Jupiter’s main ring was discovered in 1979 by NASA’s passing Voyager 1 spacecraft, but its origin was then a mystery. Data from NASA’s Galileo spacecraft that orbited Jupiter from 1995 to 2003, however, confirmed the hypothesis that this ring was created by meteoroid impacts on small nearby moons. As a small meteoroid strikes tiny Metis, for example, it will bore into the moon, vaporize, and explode dirt and dust off into a Jovian orbit. The featured image of Jupiter in infrared light by the James Webb Space Telescope shows not only Jupiter and its clouds, but this ring as well. Also visible is Jupiter’s Great Red Spot (GRS) — in comparatively light color on the right, Jupiter’s large moon Europa — in the center of diffraction spikes on the left, and Europa’s shadow — next to the GRS. Several features in the image are not yet well understood, including the seemingly separated cloud layer on Jupiter’s right limb.

Celestial Surprise: What picture did APOD feature on your birthday? (post 1995)

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2022 July 19

Pleiades over Half Dome

Image Credit & Copyright: Dheera Venkatraman

Explanation: Stars come in bunches. The most famous bunch of stars on the sky is the Pleiades, a bright cluster that can be easily seen with the unaided eye. The Pleiades lies only about 450 light years away, formed about 100 million years ago, and will likely last about another 250 million years. Our Sun was likely born in a star cluster, but now, being about 4.5 billion years old, its stellar birth companions have long since dispersed. The Pleiades star cluster is pictured over Half Dome, a famous rock structure in Yosemite National Park in California, USA. The featured image is a composite of 28 foreground exposures and 174 images of the stellar background, all taken from the same location and by the same camera on the same night in October 2019. After calculating the timing of a future juxtaposition of the Pleiades and Half Dome, the astrophotrographer was unexpectedly rewarded by an electrical blackout, making the background sky unusually dark.

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2022 July 18

Stephan’s Quintet from Webb, Hubble, and Subaru

Image Credit: Webb, Hubble, Subaru; NASA, ESA, CSA, NOAJ, STScI; Processing & Copyright: Robert Gendler

Explanation: OK, but why can’t you combine images from Webb and Hubble? You can, and today’s featured image shows one impressive result. Although the recently launched James Webb Space Telescope (Webb) has a larger mirror than Hubble, it specializes in infrared light and can’t see blue — only up to about orange. Conversely, the Hubble Space Telescope (Hubble) has a smaller mirror than Webb and can’t see as far into the infrared as Webb, but can image not only blue light but even ultraviolet. Therefore, Webb and Hubble data can be combined to create images across a wider variety of colors. The featured image of four galaxies from Stephan’s Quintet shows Webb images as red and also includes images taken by Japan‘s ground-based Subaru telescope in Hawaii. Because image data for Webb, Hubble, and Subaru are made freely available, anyone around the world can process it themselves, and even create intriguing and scientifically useful multi-observatory montages.

Stephan’s Quintet from just: Webb, Hubble

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2022 July 17

Europa and Jupiter from Voyager 1

Image Credit: NASA, Voyager 1, JPL, Caltech; Processing & License: Alexis Tranchandon / Solaris

Explanation: What are those spots on Jupiter? Largest and furthest, just right of center, is the Great Red Spot — a huge storm system that has been raging on Jupiter possibly since Giovanni Cassini‘s likely notation of it 357 years ago. It is not yet known why this Great Spot is red. The spot toward the lower left is one of Jupiter’s largest moons: Europa. Images from Voyager in 1979 bolster the modern hypothesis that Europa has an underground ocean and is therefore a good place to look for extraterrestrial life. But what about the dark spot on the upper right? That is a shadow of another of Jupiter’s large moons: Io. Voyager 1 discovered Io to be so volcanic that no impact craters could be found. Sixteen frames from Voyager 1’s flyby of Jupiter in 1979 were recently reprocessed and merged to create the featured image. Forty-five years ago this August, Voyager 1 launched from Earth and started one of the greatest explorations of the Solar System ever.

Free Download: Voyager Posters