Image Archive: Solar System

Jupiter (6 January 2024)

Thu, 14 Mar 2024 15:00:00 +0100

The giant planet Jupiter, in all its banded glory, is revisited by the NASA/ESA Hubble Space Telescope in this new image, taken on 6 January 2024, that captures both sides of the planet. Hubble monitors Jupiter and the other outer Solar System planets every year under the Outer Planet Atmospheres Legacy programme (OPAL). This is because these large worlds are shrouded in clouds and hazes stirred up by violent winds, leading to a kaleidoscope of ever-changing weather patterns.

A pair of storms is visible: a deep red cyclone and a reddish anticyclone, appear to be next to each other at right of centre. They look so red that at first glance, it looks like Jupiter skinned a knee. These storms are rotating in opposite directions, indicating an alternating pattern of high- and low-pressure systems. For the cyclone, there’s an upwelling on the edges with clouds descending in the middle causing a clearing in the atmospheric haze.

The storms are expected to bounce past each other because their opposing clockwise and counterclockwise rotations make them repel each other.

Toward the left edge of the image is the innermost Galilean moon, Io — the most volcanically active body in the Solar System, despite its small size (only slightly larger than Earth's moon). Hubble resolves volcanic outflow deposits on the surface. Hubble's sensitivity to blue and violet wavelengths clearly reveals interesting surface features.

[Image description: Jupiter is banded with stripes of brownish orange, light grey, soft yellow, and shades of cream, with many large storms and small white clouds punctuating the planet. At upper right of centre, a pair of storms appear next to each other: a deep-red, triangle-shaped cyclone and a reddish anticyclone. Toward the far-left edge of this view is Jupiter’s tiny orange-coloured moon Io.]

Jupiter OPAL observations (January 2024)

Thu, 14 Mar 2024 15:00:00 +0100

This 12-panel series of NASA/ESA Hubble Space Telescope images, taken on 5–6 January 2024, presents snapshots of a full rotation of the giant planet Jupiter. The Great Red Spot can be used to measure the planet's real rotation rate of nearly 10 hours. The innermost Galilean satellite, Io, is seen in several frames, along with its shadow crossing over Jupiter's cloud tops. Hubble monitors Jupiter and the other outer Solar System planets every year under the Outer Planet Atmospheres Legacy programme (OPAL).

[Image description: These 12 views of Jupiter were taken by Hubble throughout the planet’s full rotation on 5–6 January 2024. At top centre is the label Hubble Space Telescope Observations of Jupiter. Next to the title are the labels F658N in red, F502N in green, and F395N in blue, which represent the filters and colours used to make these images. The date and time label for each view is centred at the bottom of each image. The Great Red Spot can be used to measure the planet’s real rotation rate of nearly 10 hours. Jupiter’s innermost moon, Io, is seen in several images, along with its shadow, crossing over Jupiter’s cloud tops.]

Hubble’s two new views of Jupiter (January 2024)

Thu, 14 Mar 2024 15:00:00 +0100

The giant planet Jupiter, in all its banded glory, is revisited by the NASA/ESA Hubble Space Telescope in these latest images, taken on 5–6 January 2024, that capture both sides of the planet. Hubble monitors Jupiter and the other outer Solar System planets every year under the Outer Planet Atmospheres Legacy programme (OPAL). This is because these large worlds are shrouded in clouds and hazes stirred up by violent winds, leading to a kaleidoscope of ever-changing weather patterns.

[left image] - Big enough to swallow Earth, the classic Great Red Spot stands out prominently in Jupiter's atmosphere. To its lower right, at a more southerly latitude, is a feature sometimes dubbed Red Spot Jr. This anticyclone was the result of storms merging in 1998 and 2000, and it first appeared red in 2006 before returning to a pale beige in subsequent years. This year it is somewhat redder again. The source of the red coloration is unknown but may involve a range of chemical compounds: sulphur, phosphorus or organic material. Staying in their lanes, but moving in opposite directions, Red Spot Jr. passes the Great Red Spot about every two years. Another small red anticyclone appears in the far north.

[right image] - Storm activity also appears in the opposite hemisphere. A pair of storms: a deep red cyclone and a reddish anticyclone, appear to be next to each other at right of centre. They look so red that at first glance, it looks like Jupiter skinned a knee. These storms are rotating in opposite directions, indicating an alternating pattern of high- and low-pressure systems. For the cyclone, there’s an upwelling on the edges with clouds descending in the middle causing a clearing in the atmospheric haze.

The storms are expected to bounce past each other because their opposing clockwise and counterclockwise rotations make them repel each other.

[Image description: A side-by-side image showing both faces of Jupiter on the black background of space. The left image is labelled January 5, 2024. Jupiter is banded with stripes of brownish orange, light grey, soft yellow, and shades of cream, punctuated with many large storms and small white clouds. The Great Red Spot is the most prominent feature in the left bottom third of this view. The right image is labelled January 6, 2024. This opposite side of Jupiter is also banded with stripes of brownish orange, light grey, soft yellow, and shades of cream. At upper right of centre, a pair of storms appear next to each other: a deep-red, triangle-shaped cyclone and a reddish anticyclone. Toward the far-left edge of this view is Jupiter’s tiny orange-coloured moon Io.]

Jupiter (5 January 2024)

Thu, 14 Mar 2024 15:00:00 +0100

The giant planet Jupiter, in all its banded glory, is revisited by the NASA/ESA Hubble Space Telescope in these latest images, taken on 5 January 2024, that capture both sides of the planet. Hubble monitors Jupiter and the other outer Solar System planets every year under the Outer Planet Atmospheres Legacy programme (OPAL). This is because these large worlds are shrouded in clouds and hazes stirred up by violent winds, leading to a kaleidoscope of ever-changing weather patterns.

Big enough to swallow Earth, the classic Great Red Spot stands out prominently in Jupiter's atmosphere. To its lower right, at a more southerly latitude, is a feature sometimes dubbed Red Spot Jr. This anticyclone was the result of storms merging in 1998 and 2000, and it first appeared red in 2006 before returning to a pale beige in subsequent years. This year it is somewhat redder again. The source of the red coloration is unknown but may involve a range of chemical compounds: sulphur, phosphorus or organic material. Staying in their lanes, but moving in opposite directions, Red Spot Jr. passes the Great Red Spot about every two years. Another small red anticyclone appears in the far north.

[Image description: Jupiter is banded with stripes of brownish orange, light grey, soft yellow, and shades of cream, punctuated with many large storms and small white clouds. The largest storm, the Great Red Spot, is the most prominent feature in the left bottom third of this view. To its lower right is a smaller reddish anticyclone, Red Spot Jr.]

Hubble’s two new views of Jupiter (January 2024, compass image)

Thu, 14 Mar 2024 15:00:00 +0100

The giant planet Jupiter, in all its banded glory, is revisited by the NASA/ESA Hubble Space Telescope in these latest images taken on 5–6 January 2024, that capture both sides of the planet. Hubble monitors Jupiter and the other outer Solar System planets every year under the Outer Planet Atmospheres Legacy programme (OPAL). This is because these large worlds are shrouded in clouds and hazes stirred up by violent winds, leading to a kaleidoscope of ever-changing weather patterns.

The storms are expected to bounce past each other because their opposing clockwise and counterclockwise rotations make them repel each other.

[Image description: A side-by-side image titled Jupiter HST/WFC3/UVIS shows opposite faces of Jupiter banded in brownish orange, light grey, soft yellow, and shades of cream stripes, on the black background of space. Below the title is a colour key with filters and colours used to create the images: F395N is blue; F502N is green, and F631N is red. To the bottom right are compass arrows indicating orientation on the sky. The north arrow points towards 11 o’clock; the east arrow points toward 8 o’clock. On the other side of the planet, at upper right centre, a pair of storms appear next to each other: a deep-red, triangle-shaped cyclone and a reddish anticyclone. Toward the far-left edge of the image is Jupiter’s tiny orange-coloured moon Io.]

Saturn

Thu, 21 Dec 2023 16:00:00 +0100

This photo of Saturn was taken by the NASA/ESA Hubble Space Telescope on 22 October 2023, when the ringed planet was approximately 1365 million kilometres from Earth. Hubble's ultra-sharp vision reveals a phenomenon called ring spokes.

Saturn's spokes are transient features that rotate along with the rings. Their ghostly appearance only persists for two or three rotations around Saturn. During active periods, freshly-formed spokes continuously add to the pattern.

In 1981, NASA's Voyager 2 first photographed the ring spokes. Hubble continues observing Saturn annually as the spokes come and go. This cycle has been captured by Hubble's Outer Planets Atmospheres Legacy (OPAL) program that began nearly a decade ago to annually monitor weather changes on all four gas-giant outer planets.

Hubble's crisp images show that the frequency of spoke apparitions is seasonally driven, first appearing in OPAL data in 2021 but only on the morning (left) side of the rings. Long-term monitoring shows that both the number and contrast of the spokes vary with Saturn's seasons. Saturn is tilted on its axis like Earth and has seasons lasting approximately seven years.

This year, these ephemeral structures appear on both sides of the planet simultaneously as they spin around the giant world. Although they look small compared with Saturn, their length and width can stretch longer than Earth's diameter!

The OPAL team notes that the leading theory is that spokes are tied to interactions between Saturn's powerful magnetic field and the sun. Planetary scientists think that electrostatic forces generated from this interaction levitate dust or ice above the ring to form the spokes, though after several decades no theory perfectly predicts the spokes. Continued Hubble observations may eventually help solve the mystery.

[Image description: Planet Saturn with bright white rings, multi-colored main sphere, and moons Mimas, Dione, and Enceladus. Spoke features on the left and right sides of the rings appear like faint grey smudges against the rings’ bright backdrop, about midway from the planet to the rings’ outer edge. Above the rings plane, the planet’s bands are shades of red, orange and yellow, with bright white nearer the equator.]

Saturn (October 2023, annotated)

Thu, 21 Dec 2023 16:00:00 +0100

Jupiter in ultraviolet

Tue, 07 Nov 2023 17:10:56 +0100

This image from the NASA/ESA Hubble Space Telescope shows the planet Jupiter in a color composite of ultraviolet wavelengths.

The Great Red Spot appears red to the human eye, however in this ultraviolet image it appears darker because high altitude haze particles absorb light at these wavelengths. The reddish, wavy polar hazes are absorbing slightly less of this light due to differences in either particle size, composition, or altitude.

The data used to create this ultraviolet image is part of a Hubble proposal that looked at Jupiter’s stealthy superstorm system.

Hubble has a long history of observing the outer planets. From the Comet Shoemaker-Levy 9 impacts to studying Jupiter's storms, Hubble's decades-long career and unique vantage point provide astronomers with valuable data to chart the evolution of this dynamic planet.

Hubble’s ultraviolet-observing capabilities allow astronomers to study the short, high-energy wavelengths of light beyond what the human eye can see. Ultraviolet light reveals fascinating cosmic phenomena, including light from the hottest and youngest stars embedded in local galaxies; the composition, densities, and temperatures of the material between stars; and the evolution of galaxies.

This is a false-color image because the human eye cannot detect ultraviolet light. Therefore, colors in the visible light spectrum were assigned to the images, each taken with a different ultraviolet filter. In this case, the assigned colors for each filter are: Blue: F225W, Green: F275W, and Red: F343N.

Hubble sees boulders escaping from asteroid Dimorphos

Thu, 20 Jul 2023 16:00:00 +0200

This NASA/ESA Hubble Space Telescope image of the asteroid Dimorphos was taken on 19 December 2022, nearly four months after the asteroid was impacted by NASA’s DART (Double Asteroid Redirection Test) mission. Hubble’s sensitivity reveals a few dozen boulders knocked off the asteroid by the force of the collision. These are among the faintest objects Hubble has ever photographed inside the Solar System. The ejected boulders range in size from 1 metre to 6.7 metres across, based on Hubble photometry. They are drifting away from the asteroid at around a kilometre per hour. The discovery yields invaluable insights into the behaviour of a small asteroid when it is hit by a projectile for the purpose of altering its trajectory.

[Image Description: The bright white object at lower left is the asteroid Dimorphos. It has a blue dust tail extending diagonally to the upper right. A cluster of blue dots surrounds the asteroid. These are boulders that were knocked off the asteroid when, on 26 September 2022, NASA deliberately slammed the half-tonne DART impactor spacecraft into the asteroid as a test of what it would take to deflect some future asteroid from hitting Earth. Hubble photographed the slow-moving boulders in December 2022.]

Hubble sees boulders escaping from asteroid Dimorphos (annotated)

Thu, 20 Jul 2023 16:00:00 +0200

[Image Description: The bright white object at lower left is the asteroid Dimorphos. It has a blue dust tail extending diagonally to the upper right. A cluster of blue dots surrounds the asteroid. These are boulders that were knocked off the asteroid when, on 26 September 2022, NASA deliberately slammed the half-tonne DART impactor spacecraft into the asteroid as a test of what it would take to deflect some future asteroid from hitting Earth. Hubble photographed the slow-moving boulders in December 2022.]

Hubble finds Saturn's rings heating its atmosphere

Thu, 30 Mar 2023 16:00:00 +0200

The planet Saturn is easily recognizable for its opulent ring system that can easily be seen through a small telescope. Astronomers have now found that the rings are not as placid as they look: a rain of icy particles is affecting the giant planet's weather. It took observations of Saturn from the ESA/NASA Hubble Space Telescope and the retired NASA/ESA/ASI Cassini probe, in addition to the Voyager 1 and 2 spacecraft and the retired International Ultraviolet Explorer mission, to pull it all together.

The telltale evidence is an excess of ultraviolet radiation, seen as a spectral line of hot hydrogen in Saturn's atmosphere. The most feasible explanation is heating caused by icy ring particles raining down onto Saturn's atmosphere. This rain could be due to the impact of micrometeorites, solar wind particle bombardment, solar ultraviolet radiation, or electromagnetic forces picking up electrically charged dust.

A new study pulled together archival ultraviolet-light (UV) observations from four space missions that studied Saturn. This included observations from the two Voyager probes that flew by Saturn in the 1980s and measured the UV excess — at the time, astronomers dismissed the measurements as noise in the detectors. The Cassini mission, which arrived at Saturn in 2004, also collected UV data on the atmosphere over several years, and additional data came from the International Ultraviolet Explorer, launched in 1978, and from Hubble.

But the lingering question was whether all the data could be illusory, or instead reflected a true phenomenon on Saturn. The key to assembling the jigsaw puzzle came in the decision to use measurements from Hubble's Space Telescope Imaging Spectrograph (STIS). Its precision observations of Saturn were used to calibrate the archival UV data from all four other space missions. Four decades of UV data cover multiple solar cycles and help astronomers study the Sun's seasonal effects on Saturn.

By bringing all the diverse data together and calibrating it, it was determined that there is no seasonal difference to the level of UV radiation. The unexpected interaction between the rings and the upper atmosphere is now being investigated in depth, to define new diagnostic tools for estimating if distant exoplanets have extended, Saturn-like ring systems.

These results are featured in the paper published on 30 March 2023 in the Planetary Science Journal.

[Image description: A close-up image of the planet Saturn in ultraviolet light. The planet is coloured in shades of blue. It is tilted at a forty-five degree angle, and inclined towards the viewer so that its rings are visible; they are only slightly brighter than the black background.]

Jupiter (November 2022 and January 2023) compass image

Thu, 23 Mar 2023 15:00:00 +0100

[LEFT] - The forecast for Jupiter is for stormy weather at low northern latitudes. A prominent string of alternating storms is visible, forming a ‘vortex street’ as some planetary astronomers call it. This is a wave pattern of nested cyclones and anticyclones, locked together like the alternating gears of a machine moving clockwise and counterclockwise. If the storms get close enough to each other and merge together, they could build an even larger storm, potentially rivalling the current size of the Great Red Spot. The staggered pattern of cyclones and anticyclones prevents individual storms from merging. Activity is also seen interior to these storms; in the 1990s Hubble didn’t see any cyclones or anticyclones with built-in thunderstorms, but these storms have sprung up in the last decade. Strong colour differences indicate that Hubble is seeing different cloud heights and depths as well.

The orange moon Io photobombs this view of Jupiter’s multicoloured cloud tops, casting a shadow toward the planet’s western limb. Hubble’s resolution is so sharp that it can see Io’s mottled-orange appearance, the result of its numerous active volcanoes. These volcanoes were first discovered when the Voyager 1 spacecraft flew by in 1979. The moon’s molten interior is overlaid by a thin crust through which the volcanoes eject material. Sulphur takes on various hues at different temperatures, which is why Io’s surface is so colourful. This image was taken on 12 November 2022.

[RIGHT] - Jupiter’s legendary Great Red Spot takes centre stage in this view. Though this vortex is big enough to swallow Earth, it has actually shrunk to the smallest size it has ever been according to observation records dating back 150 years. Jupiter’s icy moon Ganymede can be seen transiting the giant planet at lower right. Slightly larger than the planet Mercury, Ganymede is the largest moon in the Solar System. It is a cratered world and has a mainly water-ice surface with apparent glacial flows driven by internal heat. This image was taken on 6 January 2023.

This image is smaller in size because Jupiter was 130,000 kilometres farther from Earth when the image was taken.

[Image description: Two views of the giant gas planet Jupiter appear side-by-side for comparison.]

Jupiter (November 2022 and January 2023)

Thu, 23 Mar 2023 15:00:00 +0100

This image is smaller in size because Jupiter was 130,000 kilometres farther from Earth when the image was taken.

[Image description: Two views of the giant gas planet Jupiter appear side-by-side for comparison.]

Uranus (November 2014)

Thu, 23 Mar 2023 15:00:00 +0100

This is a Hubble view of Uranus taken in 2014, seven years after the northern spring equinox when the Sun was shining directly over the planet’s equator, and shows one of the first images from the OPAL programme. Multiple storms with methane ice-crystal clouds appear at mid-northern latitudes above the planet’s cyan-tinted lower atmosphere. Hubble photographed the ring system edge-on in 2007, but the rings are seen starting to open up seven years later in this view. At this time, the planet had multiple small storms and even some faint cloud bands.

[Image description: Uranus is mainly colored cyan. The planet looks like a flat circle outlined with a pinkish gray limb. Faint, pinkish gray bands and streaks run nearly vertically across Uranus, while splotches of white clouds dot the right half of the planet’s face. The right third of the planet appears mostly white and pinkish gray, as though that part of the atmosphere were thick with clouds.]

Jupiter (January 2023)

Thu, 23 Mar 2023 15:00:00 +0100

Jupiter’s legendary Great Red Spot takes centre stage in this view. Though this vortex is big enough to swallow Earth, it has actually shrunk to the smallest size it has ever been according to observation records dating back 150 years. Jupiter’s icy moon Ganymede can be seen transiting the giant planet at lower right. Slightly larger than the planet Mercury, Ganymede is the largest moon in the Solar System. It is a cratered world and has a mainly water-ice surface with apparent glacial flows driven by internal heat. This image was taken on 6 January 2023.

[Image description: Jupiter looms large in this image. Set against a black background, the planet is banded in stripes of brownish orange, light gray, soft yellow, and shades of cream. White and cream colored ovals punctuate the planet at all latitudes. The icy moon Ganymede appears as a gray, mottled orb crossing the face of Jupiter.]

Uranus (November 2022)

Thu, 23 Mar 2023 15:00:00 +0100

As seen in 2022, Uranus’s north pole shows a thickened photochemical haze that looks similar to the smog over cities. Several little storms can be seen near the edge of the polar haze boundary. Hubble has been tracking the size and brightness of the north polar cap and it continues to get brighter year after year. Astronomers are disentangling multiple effects — from atmospheric circulation, particle properties, and chemical processes — that control how the atmospheric polar cap changes with the seasons. At the Uranian equinox in 2007, neither pole was particularly bright. As the northern summer solstice approaches in 2028 the cap may grow brighter still, and will be aimed directly toward Earth, allowing good views of the rings and the north pole; the ring system will then appear face-on. This image was taken on 10 November 2022.

[Image description: Uranus appears tipped on its side. Set against a black background, the planet is mainly colored cyan. It looks like a flat circle outlined with a pinkish gray limb. A faint, pink ring encircles the planet nearly vertically. The faint ring appears to be almost face on. A large area of white coves much of the right side of the planet.]

Jupiter (November 2022)

Thu, 23 Mar 2023 15:00:00 +0100

The forecast for Jupiter is for stormy weather at low northern latitudes. A prominent string of alternating storms is visible, forming a ‘vortex street’ as some planetary astronomers call it. This is a wave pattern of nested cyclones and anticyclones, locked together like the alternating gears of a machine moving clockwise and counterclockwise. If the storms get close enough to each other and merge together, they could build an even larger storm, potentially rivalling the current size of the Great Red Spot. The staggered pattern of cyclones and anticyclones prevents individual storms from merging. Activity is also seen interior to these storms; in the 1990s Hubble didn’t see any cyclones or anticyclones with built-in thunderstorms, but these storms have sprung up in the last decade. Strong colour differences indicate that Hubble is seeing different cloud heights and depths as well.

Uranus (November 2014 and November 2022)

Thu, 23 Mar 2023 15:00:00 +0100

Planetary oddball Uranus rolls around the Sun on its side as it follows its 84-year orbit, rather than spinning in a more ’vertical’ position as Earth does. Its weirdly tilted ‘horizontal’ rotation axis is angled just eight degrees off the plane of the planet’s orbit. One recent theory proposes that Uranus once had a massive moon that gravitationally destabilised it and then crashed into it. Other possibilities include giant impacts during the formation of the planets, or even giant planets exerting resonant torques on each other over time. The consequences of Uranus’s tilt are that for stretches of time lasting up to 42 years, parts of one hemisphere are completely without sunlight. When the Voyager 2 spacecraft visited during the 1980s, the planet’s south pole was pointed almost directly at the Sun. Hubble’s latest view shows the northern pole now tipping toward the Sun.

[LEFT] - This is a Hubble view of Uranus taken in 2014, seven years after the northern spring equinox when the Sun was shining directly over the planet’s equator, and shows one of the first images from the OPAL programme. Multiple storms with methane ice-crystal clouds appear at mid-northern latitudes above the planet’s cyan-tinted lower atmosphere. Hubble photographed the ring system edge-on in 2007, but the rings are seen starting to open up seven years later in this view. At this time, the planet had multiple small storms and even some faint cloud bands.

[RIGHT] - As seen in 2022, Uranus’s north pole shows a thickened photochemical haze that looks similar to the smog over cities. Several little storms can be seen near the edge of the polar haze boundary. Hubble has been tracking the size and brightness of the north polar cap and it continues to get brighter year after year. Astronomers are disentangling multiple effects — from atmospheric circulation, particle properties, and chemical processes — that control how the atmospheric polar cap changes with the seasons. At the Uranian equinox in 2007, neither pole was particularly bright. As the northern summer solstice approaches in 2028 the cap may grow brighter still, and will be aimed directly toward Earth, allowing good views of the rings and the north pole; the ring system will then appear face-on. This image was taken on 10 November 2022.

[Image description: Two views of the tipped planet Uranus appear side-by-side for comparison.]

Uranus (November 2014 and November 2022) compass image

Thu, 23 Mar 2023 15:00:00 +0100

[Image description: Two views of the tipped planet Uranus appear side-by-side for comparison.]

Hubble’s new views of Jupiter and Uranus

Thu, 23 Mar 2023 15:00:00 +0100

[Jupiter: left] - The forecast for Jupiter is for stormy weather at low northern latitudes. A prominent string of alternating storms is visible, forming a ‘vortex street’ as some planetary astronomers call it. This is a wave pattern of nested cyclones and anticyclones, locked together like the alternating gears of a machine moving clockwise and counterclockwise. If the storms get close enough to each other and merge together, they could build an even larger storm, potentially rivalling the current size of the Great Red Spot. The staggered pattern of cyclones and anticyclones prevents individual storms from merging. Activity is also seen interior to these storms; in the 1990s Hubble didn’t see any cyclones or anticyclones with built-in thunderstorms, but these storms have sprung up in the last decade. Strong colour differences indicate that Hubble is seeing different cloud heights and depths as well.

[Uranus: right] - Uranus’s north pole shows a thickened photochemical haze that looks similar to the smog over cities. Several little storms can be seen near the edge of the polar haze boundary. Hubble has been tracking the size and brightness of the north polar cap and it continues to get brighter year after year. Astronomers are disentangling multiple effects — from atmospheric circulation, particle properties, and chemical processes — that control how the atmospheric polar cap changes with the seasons. At the Uranian equinox in 2007, neither pole was particularly bright. As the northern summer solstice approaches in 2028 the cap may grow brighter still, and will be aimed directly toward Earth, allowing good views of the rings and the north pole; the ring system will then appear face-on. This image was taken on 10 November 2022.

Note: The planets do not appear in this image to scale.

[Image description: Jupiter is positioned on the left. It is banded in stripes of brownish orange, light gray, soft yellow, and shades of cream. Uranus is positioned on the right. It appears tipped on its side and is mainly coloured cyan.]

Spokes Spotted In Saturn's Rings

Thu, 09 Feb 2023 15:00:00 +0100

The NASA/ESA Hubble Space Telescope has observation time devoted to Saturn each year, thanks to the Outer Planet Atmospheres Legacy (OPAL) program, and the dynamic gas giant planet always shows us something new. This latest image heralds the start of Saturn's "spoke season" with the appearance of two smudgy spokes in the B ring, on the left in the image.

The spokes are enigmatic features which appear across Saturn’s rings. Their presence and appearance varies with the seasons — like Earth, Saturn is tilted on its axis and therefore has four seasons. With Saturn's much larger orbit, each season lasts approximately seven Earth years. Equinox occurs when the rings are tilted edge-on to the Sun and marks the height of spokes’ visibility, while during a solstice when the Sun is at its highest or lowest latitude, the spokes disappear.

The shape and shading of spokes varies — they can appear light or dark, depending on the viewing angle, and sometimes appear more like blobs than classic radial spoke shapes, as seen here. The ephemeral features don't last long, but as the planet's autumnal equinox approaches on 6 May 2025, more will appear.

Scientists will be looking for clues to explain the cause and nature of the spokes. It's suspected they are caused by interaction between Saturn's magnetic field and the solar wind, which also causes aurorae to appear on the planet. The hypothesis is that spokes are the smallest, dust-sized, icy ring particles being temporarily electrically charged and levitated, but this has not been confirmed.

Saturn's last equinox occurred in 2009, while the NASA/ESA/ASI Cassini spacecraft was orbiting the gas giant planet for close-up reconnaissance. With Cassini's mission completed in 2017, Hubble is continuing the work of long-term monitoring of changes on Saturn and the other outer planets.

[Image description: A close-up image of the planet Saturn. The rings are level with the viewer, and tilted slightly down.]

Visitor to a Galaxy

Mon, 16 Jan 2023 06:00:00 +0100

A host of astronomical objects throng this image from the NASA/ESA Hubble Space Telescope. Background galaxies ranging from stately spirals to fuzzy ellipticals are strewn across the image, and bright foreground stars much closer to home are also present, surrounded by diffraction spikes. In the centre of the image, the vague shape of the small galaxy UGC 7983 appears as a hazy cloud of light. UGC 7983 is around 30 million light-years from Earth in the constellation Virgo, and is a dwarf irregular galaxy — a type thought to be similar to the very earliest galaxies in the Universe.

This image also conceals an astronomical interloper. A minor asteroid, only a handful of kilometres across, can be seen streaking across the upper left-hand side of this image. The trail of the asteroid is visible as four streaks of light separated by small gaps. These streaks of light represent the four separate exposures that were combined to create this image, the small gaps between each observation being necessary to change the filters inside Hubble’s Advanced Camera for Surveys.

Capturing an asteroid was a fortunate side effect of a larger effort to observe every known galaxy close to the Milky Way. When this project was first proposed, roughly 75% of all the Milky Way’s near galactic neighbours had been imaged by Hubble. A group of astronomers proposed using the gaps between longer Hubble observations to capture images of the remaining 25%. The project was an elegantly efficient way to fill out some gaps not only in Hubble's observing schedule, but also in our knowledge of nearby galaxies.

Hubble’s Observations of Uranus and Neptune in 2021

Tue, 31 May 2022 17:00:00 +0200

Left: Hubble’s 25 October 2021 view of Uranus puts the planet’s bright northern polar hood in the spotlight.

Right: Hubble’s 7 September 2021 view of Neptune features the planet’s dark spot and darkened northern hemisphere.

A Dazzling Hubble Collection of Supernova Host Galaxies

Thu, 19 May 2022 16:00:00 +0200

Spanning from 2003 to 2021, this collection of images from the NASA/ESA Hubble Space Telescope features galaxies that are all hosts to both Cepheid variables and supernovae. These two celestial phenomena are both crucial tools used by astronomers to determine astronomical distance, and have been used to refine our measurement of Hubble’s constant, the expansion rate of the Universe.

Broken Asteroid Trail in NGC 4548

Fri, 06 May 2022 09:00:00 +0200

This is a broken asteroid trail crossing the outer regions of galaxy NGC 4548 in Coma Berenices. Five trail segments (shown in white) were extracted from individual exposures and added to a cleaned colour image of the galaxy.

The asteroid enters the image at top center and moves down toward the lower left. Large gaps in the trail occur because the telescope is orbiting the Earth and cannot continuously observe the galaxy.