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April 4 in spaceflight
Wikipedia records 5 spaceflight and astronomy events on April 4. Below are the pictures NASA published on April 4 in 6 different years — each one taken or released on this exact date.
Recorded events
IN THE RECORD5ENTRIES
Spaceflight and astronomy entries from Wikipedia's record of this date, oldest first — from 1968 onward.
Pictures from this date
PUBLISHED6IMAGES
NASA's Astronomy Picture of the Day for April 4, one per year. Some are public domain and some belong to the photographer — each says which.
Published on April 4
NASA’s Astronomy Picture of the Day, for this calendar date in each of the last several years.
2026
Hello World
From pole to pole our fair planet is captured in this snapshot from space, an evocative image from a window of the Orion spacecraft Integrity. From the spacecraft's perspective the Sun is moving behind Earth's bright limb along the lower right. Africa and the Iberian peninsula are in view on the pale blue planet's surface, while aurorae crown Earth's south and north poles at top right and bottom left. Commander Reid Wiseman took the historic picture on Artemis II mission flight day 2 (April 2), after the completion of the planned translunar injection burn. That burn boosted the spacecraft out of Earth orbit, sending Integrity and crew on a trajectory that will take them around the Moon and back again. That's a journey humans last made over 50 years ago. (Editor's note: Venus is photobombing Wiseman's historic pic. Currently appearing in our western skies after sunset, the inner planet is in the frame below and right of Earth's bright limb, immersed in a faint band of zodiacal light.)
NASA · public domain
2025
Hickson 44 in Leo
Scanning the skies for galaxies, Canadian astronomer Paul Hickson and colleagues identified some 100 compact groups of galaxies, now appropriately called Hickson Compact Groups. The four prominent galaxies seen in this intriguing telescopic skyscape are one such group, Hickson 44. The galaxy group is about 100 million light-years distant, far beyond the spiky foreground Milky Way stars, toward the constellation Leo. The two spiral galaxies in the center of the image are edge-on NGC 3190 with its distinctive, warped dust lanes, and S-shaped NGC 3187. Along with the bright elliptical, NGC 3193 (above and left) they are also known as Arp 316. The spiral toward the lower right corner is NGC 3185, the 4th member of the Hickson group. Like other galaxies in Hickson groups, these show signs of distortion and enhanced star formation, evidence of a gravitational tug of war that will eventually result in galaxy mergers on a cosmic timescale. The merger process is now understood to be a normal part of the evolution of galaxies, including our own Milky Way. For scale, NGC 3190 is about 75,000 light-years across at the estimated distance of Hickson 44.
© Jiang Wu — used with the credit NASA publishes
2024
Comet Pons-Brooks at Night
In dark evening skies over June Lake, northern hemisphere, planet Earth, Comet 12P/Pons-Brooks stood just above the western horizon on March 30. Its twisted turbulent ion tail and diffuse greenish coma are captured in this two degree wide telescopic field of view along with bright yellowish star Hamal also known as Alpha Arietis. Now Pons-Brooks has moved out of the northern night though, approaching perihelion on April 21. On April 8 you might still spot the comet in daytime skies. But to do it, you will have to stand in the path of totality and look away from the spectacle of an alluring solar corona and totally eclipsed Sun. NASA Coverage: Total Solar Eclipse of 2024 April 8
© Dan Bartlett — used with the credit NASA publishes
2023
Olympus Mons: Largest Volcano in the Solar System
The largest volcano in our Solar System is on Mars. Although three times higher than Earth's Mount Everest, Olympus Mons will not be difficult for humans to climb because of the volcano's shallow slopes and Mars' low gravity. Covering an area greater than the entire Hawaiian volcano chain, the slopes of Olympus Mons typically rise only a few degrees at a time. Olympus Mons is an immense shield volcano, built long ago by fluid lava. A relatively static surface crust allowed it to build up over time. Its last eruption is thought to have been about 25 million years ago. The featured image was taken by the European Space Agency's robotic Mars Express spacecraft currently orbiting the Red Planet. Your Sky Surprise: What picture did APOD feature on your birthday? (post 1995)
NASA · public domain
2022
A Vortex Aurora over Iceland
No, the car was not in danger of being vacuumed into space by the big sky vortex. For one reason, the vortex was really an aurora, and since auroras are created by particles striking the Earth from space, they do not create a vacuum. This rapidly developing auroral display was caused by a Coronal Mass Ejection from the Sun that passed by the Earth closely enough to cause a ripple in Earth's magnetosphere. The upper red parts of the aurora occur over 250 kilometers high with its red glow created by atmospheric atomic oxygen directly energized by incoming particles. The lower green parts of the aurora occur over 100 kilometers high with its green glow created by atmospheric atomic oxygen energized indirectly by collisions with first-energized molecular nitrogen. Below 100 kilometers, there is little atomic oxygen, which is why auroras end abruptly. The concentric cylinders depict a dramatic auroral corona as seen from the side. The featured image was created from a single 3-second exposure taken in mid-March over Lake Myvatn in Iceland. April is: Global Astronomy Month
© Christophe Suarez — used with the credit NASA publishes
2021
In, Through, and Beyond Saturn's Rings
Four moons are visible on the featured image -- can you find them all? First -- and farthest in the background -- is Titan, the largest moon of Saturn and one of the larger moons in the Solar System. The dark feature across the top of this perpetually cloudy world is the north polar hood. The next most obvious moon is bright Dione, visible in the foreground, complete with craters and long ice cliffs. Jutting in from the left are several of Saturn's expansive rings, including Saturn's A ring featuring the dark Encke Gap. On the far right, just outside the rings, is Pandora, a moon only 80-kilometers across that helps shepherd Saturn's F ring. The fourth moon? If you look closely inside Saturn's rings, in the Encke Gap, you will find a speck that is actually Pan. Although one of Saturn's smallest moons at 35-kilometers across, Pan is massive enough to help keep the Encke gap relatively free of ring particles. After more than a decade of exploration and discovery, the Cassini spacecraft ran low on fuel in 2017 and was directed to enter Saturn's atmosphere, where it surely melted.
NASA · public domain
What happened on April 4
1975
Vietnam War: A United States Air Force Lockheed C-5A Galaxy transporting orphans, crashes near Saigon, South Vietnam shortly after takeoff, killing 172 people.
Vietnam War ↗
1983
Space Shuttle program: Space Shuttle Challenger makes its maiden voyage into space on STS-6.
Space Shuttle program ↗
1996
Comet Hyakutake is imaged by the USA Asteroid Orbiter Near Earth Asteroid Rendezvous.
Comet Hyakutake ↗
1997
Space Shuttle program: Space Shuttle Columbia is launched on STS-83. However, the mission is later cut short due to a fuel cell problem.
Space Shuttle Columbia ↗
Sources and licences
Event text and thumbnails come from Wikipedia and are used under CC BY-SA 4.0. Images are drawn only from Wikimedia Commons, which does not accept non-free content — each thumbnail links to its file page, where its licence and author are recorded.
Launch records are from The Space Devs’ Launch Library 2. This archive is still being mirrored, so some days are incomplete. Pictures are NASA’s Astronomy Picture of the Day; NASA imagery is generally not subject to copyright, but individual APOD entries are frequently the property of the photographer, and each caption says which applies.
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Cosmos — Carl Sagan
Still the best single argument for why any of this matters, and it leaves the arithmetic in. For a reader who wants the science, not just the awe.
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Pale Blue Dot — Carl Sagan
The case for leaving Earth, written by someone unsentimental about how hard that is. Suits readers who want the argument rather than the poster.
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Project Hail Mary — Andy Weir
Hard-SF problem solving in The Martian's key — for anyone who liked the engineering more than the peril. The only novel on this list.
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