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

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 16

Tycho and Clavius at Dawn

Image Credit & Copyright: Eduardo Schaberger Poupeau

Explanation: South is up in this dramatic telescopic view of the lunar terminator and the Moon’s rugged southern highlands. The lunar landscape was captured on July 7 with the moon at its first quarter phase. The Sun shines at a low angle from the right as dawn comes to the region’s young and old craters Tycho and Clavius. About 100 million years young, Tycho is the sharp-walled 85 kilometer diameter crater below and left of center. Its 2 kilometer tall central peak and far crater wall reflect bright sunlight, Its smooth floor lies in dark shadow. Debris ejected during the impact that created Tycho make it the stand out lunar crater when the Moon is near full though. They produce a highly visible radiating system of light streaks or rays that extend across much of the lunar near side. In fact, some of the material collected at the Apollo 17 landing site, about 2,000 kilometers away, likely originated from the Tycho impact. One of the oldest and largest craters on the Moon’s near side, 225 kilometer diameter Clavius is due south (above) of Tycho. Clavius crater’s own ray system resulting from its original impact event would have faded long ago. The old crater’s worn walls and smooth floor are now overlayed by newer smaller craters from impacts that occurred after Clavius was formed. Reaching above the older crater, tops of the newer crater walls reflect this dawn’s early light to create narrow shining arcs within a shadowed Clavius.

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 15

Lubovna Full Moon

Image Credit & Copyright: Petr Horalek / Institute of Physics in Opava

Explanation: On July 13 this well-planned telephoto view recorded a Full Moon rising over Lubovna Castle in eastern Slovakia. The photographer was about 3 kilometers from the castle walls and about 357,000 kilometers from this Full Moon near perigee, the closest point in its elliptical orbit. Known to some as supermoons, full moons near perigee are a little brighter and larger in planet Earth’s sky when compared to full moons that occur near the average lunar distance of around 384,000 kilometers. Of course any Full Moon near the horizon can show the effects of refraction over a long sight-line through dense clear atmosphere. In this image, atmospheric refraction creates the slight green flash framed by thin clouds near the top, with a ragged red rim along the bottom edge of July’s perigee Full Moon.

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 14

Webb’s Southern Ring Nebula

Image Credit: NASA, ESA, CSA, STScI, NIRCam

Explanation: Cataloged as NGC 3132 the Southern Ring Nebula is a planetary nebula, the death shroud of a dying sun-like star some 2,500 light-years from Earth. Composed of gas and dust the stunning cosmic landscape is nearly half a light-year in diameter, explored in unprecedented detail by the James Webb Space Telescope. In this NIRCam image the bright star near center is a companion of the dying star. In mutual orbit, the star whose transformation has ejected the nebula’s gas and dust shells over thousands of years is the fainter stellar partner. Evolving to become a white dwarf, the faint star appears along the diffraction spike extending toward the 8 o’clock position. This stellar pair’s orbital motion has resulted the complex structures within the Southern Ring Nebula.

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 13

Webb’s First Deep Field

Image Credit: NASA, ESA, CSA, STScI, NIRCam

Explanation: This is the deepest, sharpest infrared image of the cosmos so far. The view of the early Universe toward the southern constellation Volans was achieved in 12.5 hours of exposure with the NIRCam instrument on the James Webb Space Telescope. Of course the stars with six visible spikes are well within our own Milky Way. Their diffraction pattern is characteristic of Webb’s 18 hexagonal mirror segments operating together as a single 6.5 meter diameter primary mirror. The thousands of galaxies flooding the field of view are members of the distant galaxy cluster SMACS0723-73, some 4.6 billion light-years away. Luminous arcs that seem to infest the deep field are even more distant galaxies though. Their images are distorted and magnified by the dark matter dominated mass of the galaxy cluster, an effect known as gravitational lensing. Analyzing light from two separate arcs below the bright spiky star, Webb’s NIRISS instrument indicates the arcs are both images of the same background galaxy. And that galaxy’s light took about 9.5 billion years to reach the James Webb Space Telescope.

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 12

Noctilucent Clouds over Paris

Credit & Copyright: Bertrand Kulik

Explanation: It’s northern noctilucent cloud season. Composed of small ice crystals forming only during specific conditions in the upper atmosphere, noctilucent clouds may become visible at sunset during late summer when illuminated by sunlight from below. Noctilucent clouds are the highest clouds known and now established to be polar mesospheric clouds observed from the ground. Although observed with NASA’s AIM satellite since 2007, much about noctilucent clouds remains unknown and so a topic of active research. The featured image shows expansive and rippled noctilucent clouds wafting over Paris, France. This year, several northern locations are already reporting especially vivid displays of noctilucent clouds.

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 11

Andromeda over the Sahara Desert

Credit & Copyright: Jordi Coy

Explanation: What is the oldest thing you can see? At 2.5 million light years distant, the answer for the unaided eye is the Andromeda galaxy, because its photons are 2.5 million years old when they reach you. Most other apparent denizens of the night sky — stars, clusters, and nebulae — appear as they were only a few hundred to a few thousand years ago, as they lie well within our own Milky Way Galaxy. Given its distance, light from Andromeda is likely also the farthest object that you can see. Also known as M31, the Andromeda Galaxy dominates the center of the featured zoomed image, taken from the Sahara Desert in Morocco last month. The featured image is a combination of three background and one foreground exposure — all taken with the same camera and from the same location and on the same calendar day — with the foreground image taken during the evening blue hour. M110, a satellite galaxy of Andromenda is visible just above and to the left of M31’s core. As cool as it may be to see this neighboring galaxy to our Milky Way with your own eyes, long duration camera exposures can pick up many faint and breathtaking details. Recent data indicates that our Milky Way Galaxy will collide and combine with the similarly-sized Andromeda galaxy in a few billion years.

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 10

In the Center of the Cat’s Eye Nebula

Credit: NASA, ESA, Hubble, HLA; Reprocessing & Copyright: Raul Villaverde

Explanation: Three thousand light-years away, a dying star throws off shells of glowing gas. This image from the Hubble Space Telescope reveals the Cat’s Eye Nebula (NGC 6543), to be one of the most complex planetary nebulae known. Spanning half a light-year, the features seen in the Cat’s Eye are so complex that astronomers suspect the bright central object may actually be a binary star system. The term planetary nebula, used to describe this general class of objects, is misleading. Although these objects may appear round and planet-like in small telescopes, high resolution images with large telescopes reveal them to be stars surrounded by cocoons of gas blown off in the late stages of stellar evolution. Gazing into this Cat’s Eye, astronomers may well be seeing more than detailed structure, they may be seeing the fate of our Sun, destined to enter its own planetary nebula phase of evolution … in about 5 billion years.

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 9

Saturn and the ISS

Image Credit & Copyright: Tom Glenn

Explanation: Soaring high in skies around planet Earth, bright planet Saturn was a star of June’s morning planet parade. But very briefly on June 24 it posed with a bright object in low Earth orbit, the International Space Station. On that date from a school parking lot in Temecula, California the ringed-planet and International Space Station were both caught in this single high-speed video frame. Though Saturn was shining at +0.5 stellar magnitude the space station was an even brighter -3 on the magnitude scale. That difference in brightness is faithfully represented in the video capture frame. In the challenging image, the orbiting ISS was at a range of 602 kilometers. Saturn was about 1.4 billion kilometers from the school parking lot.

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 8

Roots on a Rotating Planet

Image Credit & Copyright: Marcella Giulia Pace

Explanation: With roots on a rotating planet, an old tree is centered in this sequence of 137 exposures each 20 seconds long, recorded one night from northern Sicily. Digital camera and fisheye lens were fixed to a tripod to capture the dramatic timelapse, so the stars trailed through the region’s dark sky. Of course that makes it easy to spot the planet’s north celestial pole. The extension of Earth’s axis of rotation into space is toward the upper left, at the center of the concentric star trail arcs. The Milky Way is there too. The plane of our galaxy stretches across the wide field of view from north to east (left to right) creating a broader luminous band of diffuse starlight.

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 7

The NGC 6914 Complex

Image Credit & Copyright: Giorgio Ferrari

Explanation: A study in contrasts, this colorful skyscape features stars, dust, and glowing gas in the vicinity of NGC 6914. The interstellar complex of nebulae lies some 6,000 light-years away, toward the high-flying northern constellation Cygnus and the plane of our Milky Way Galaxy. Obscuring interstellar dust clouds appear in silhouette while reddish hydrogen emission nebulae, along with the dusty blue reflection nebulae, fill the cosmic canvas. Ultraviolet radiation from the massive, hot, young stars of the extensive Cygnus OB2 association ionize the region’s atomic hydrogen gas, producing the characteristic red glow as protons and electrons recombine. Embedded Cygnus OB2 stars also provide the blue starlight strongly reflected by the dust clouds. The over 1 degree wide telescopic field of view spans about 100 light-years at the estimated distance of NGC 6914.

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 5

A Molten Galaxy Einstein Ring

Image Credit: ESA/Hubble & NASA, S. Jha; Processing: Jonathan Lodge

Explanation: It is difficult to hide a galaxy behind a cluster of galaxies. The closer cluster’s gravity will act like a huge lens, pulling images of the distant galaxy around the sides and greatly distorting them. This is just the case observed in the featured image recently re-processed image from the Hubble Space Telescope. The cluster GAL-CLUS-022058c is composed of many galaxies and is lensing the image of a yellow-red background galaxy into arcs seen around the image center. Dubbed a molten Einstein ring for its unusual shape, four images of the same background galaxy have been identified. Typically, a foreground galaxy cluster can only create such smooth arcs if most of its mass is smoothly distributed — and therefore not concentrated in the cluster galaxies visible. Analyzing the positions of these gravitational arcs gives astronomers a method to estimate the dark matter distribution in galaxy clusters, as well as infer when the stars in these early galaxies began to form.

 

New APOD Social Mirrors in Arabic: On Facebook, Instagram, and Twitter

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 4

Strawberry Supermoon Over Devil’s Saddle

Image Credit & Copyright: Lorenzo Busilacchi

Explanation: Near the horizon the full moon often seems to loom large, swollen in appearance by the famous Moon illusion. But time-lapse image sequences demonstrate that the Moon’s angular size doesn’t really change as it rises or sets. Its color does, though. Recording a frame about every 60 seconds, this image also shows how red the Sun can look while low on the horizon. The featured montage was taken from Cagliari, Sardinia, Italy, the day after June’s Strawberry Moon, a full moon dubbed a supermoon due to its slightly larger-than-usual angular size. This Strawberry Supermoon is seen rising behind the Devil’s Saddle, a mountain named for the unusual moon-sized dip seen just to the right of the rising moon. A shrinking line-of-sight through planet Earth’s dense and dusty atmosphere shifted the moonlight from strawberry red through honey-colored and paler yellowish hues. That change seems appropriate for a northern June Full Moon also known as the Strawberry or Honey Moon. A Thunder Supermoon — the third of four supermoons in 2022 — will occur later this month.

 

Today’s Adventure Link: Click on “Cagliari”

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 3

Phobos: Doomed Moon of Mars

Image Credit: HiRISE, MRO, LPL (U. Arizona), NASA

Explanation: This moon is doomed. Mars, the red planet named for the Roman god of war, has two tiny moons, Phobos and Deimos, whose names are derived from the Greek for Fear and Panic. These martian moons may well be captured asteroids originating in the main asteroid belt between Mars and Jupiter or perhaps from even more distant reaches of our Solar System. The larger moon, Phobos, is indeed seen to be a cratered, asteroid-like object in this stunning color image from the robotic Mars Reconnaissance Orbiter, with objects as small as 10 meters visible. But Phobos orbits so close to Mars – about 5,800 kilometers above the surface compared to 400,000 kilometers for our Moon – that gravitational tidal forces are dragging it down. In perhaps 50 million years, Phobos is expected to disintegrate into a ring of debris.