Our solar system is a wonder, from the star at the center to the planets and moons in orbit, as seen in these fantastic pictures taken by Hubble, the Solar Dynamics Observatory, and the Mars Reconnaissance Orbiter. Now, we know of many other stellar systems, and we're even starting to see systems in their early formation, including proplyds like the one captured by the European Southern Observatory.
Credit: NASA, ESA, and E. Karkoschka (University of Arizona)
Monday, 22 September 2025
NASA's Hubble Space Telescope caught Jupiter's moon Ganymede playing a game of "peek-a-boo." In this crisp Hubble image, Ganymede is shown just before it ducks behind the giant planet.
Ganymede completes an orbit around Jupiter every seven days. Because Ganymede's orbit is tilted nearly edge-on to Earth, it routinely can be seen passing in front of and disappearing behind its giant host, only to reemerge later.
Composed of rock and ice, Ganymede is the largest moon in our solar system. It is even larger than the planet Mercury. But Ganymede appears as a dirty snowball compared to Jupiter, the largest planet in our solar system. Jupiter is so big that only part of its Southern Hemisphere can be seen in this image.
Hubble's view is so sharp that astronomers can see features on Ganymede's surface, most notably the white impact crater, Tros, and its system of rays, bright streaks of material blasted from the crater. Tros and its ray system are roughly the width of Arizona.
The image also shows Jupiter's Great Red Spot, the prominent, eye-shaped feature located at the upper left. A storm the size of two Earths, the Great Red Spot has been raging for more than 300 years. Hubble's sharp view of the gas giant planet also reveals the texture of the clouds in the Jovian atmosphere as well as various other storms and vortices.
Astronomers use these images to study Jupiter's upper atmosphere. As Ganymede passes behind the giant planet, it reflects sunlight, which then passes through Jupiter's atmosphere. Imprinted on that light is information about the gas giant's atmosphere, which yields clues about the properties of Jupiter's high-altitude haze above the cloud tops.
This color image was made from three images taken on April 9, 2007, with the Wide Field Planetary Camera 2 in red, green, and blue filters. The image shows Jupiter and Ganymede in close to natural colors.
Credit: NASA/JPL-Caltech/University of Arizona
Tuesday, 23 September 2025
These Martian dunes in Mars' northern hemisphere were captured from above by NASA's Mars Reconnaissance Orbiter using its High-Resolution Imaging Science Experiment (HiRISE) camera on Sept. 8, 2022. Scientists use such images to track the amount of frost that settles on the landforms and then disappears as the weather warms in spring.
Martian dunes migrate just like dunes on Earth, with wind blowing away sand on one side of the dune and building up on another. Recent research has shown that winter frost stops the movement of sand grains, locking the dunes in place until the spring thaw.
Credit: NASA's GSFC, SDO AIA Team via APOD
Wednesday, 24 September 2025
Toward the middle of 2012, a long-standing solar filament suddenly erupted into space, producing an energetic coronal mass ejection (CME). The filament had been held up for days by the Sun's ever-changing magnetic field, and the timing of the eruption was unexpected. Watched closely by the Sun-orbiting Solar Dynamics Observatory (SDO), the resulting explosion shot electrons and ions into the Solar System, some of which arrived at Earth three days later and impacted Earth's magnetosphere, causing visible auroras. Loops of plasma surrounding the active region are visible above the erupting filament in the featured ultraviolet image.
Credit: ESA/Hubble, NASA, L. Lamy, L. Sromovsky
Thursday, 25 September 2025
This image of Uranus’ aurorae was taken by the NASA/ESA Hubble Space Telescope on 10 October 2022. These observations were made by the Space Telescope Imaging Spectrograph (STIS) and include both visible and ultraviolet data.
An international team of astronomers used Hubble to make new measurements of Uranus' interior rotation rate by analyzing more than a decade of the telescope’s observations of Uranus’ aurorae. This refinement of the planet’s rotation period achieved a level of accuracy 1000 times greater than previous estimates and serves as a crucial new reference point for future planetary research.
Credit: ESO/M. L. Aru et al.
Friday, 26 September 2025
Young stars are surrounded by a disc of gas and dust: the building materials for planets. When other very bright and massive stars are present nearby, their light heats the young star’s disc, stripping away part of its material. The teardrop-shaped object in this image, 177-341 W, is in the Orion Nebula. The stars eroding away the disc of 177-341 W are out of the frame, past the upper-right corner.
When their radiation clashes with the material around the young star, it creates the bright, bow-like structure seen here in yellow. The tail extending from the star towards the lower-left corner represents material being dragged away from 177-341 W by the stars, which are out of the field of view. This type of object — ionised protoplanetary discs — is known as “proplyds”.
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