JUICE mission to fly by Earth in late September

This is an artist’s impression of the JUICE mission, which will target Jupiter’s icy moons. In this view, JUICE passes over Ganymede with Jupiter in the background. In order to get there, JUICE must first make 2 more flybys of Earth for gravity assists. Image via ESA (acknowledgement: ATG Medialab).

JUICE mission will fly by Earth in late September

The JUICE mission — which stands for JUpiter Icy Moons Explorer — is on its way to Jupiter, where it will explore its ocean-bearing moons. But its path to Jupiter is not straight. In fact, JUICE will swing by Earth in late September to get a gravity assist. This will be the third of four planned gravity assists to slingshot the spacecraft toward our solar system’s largest planet.

At the moment, ESA puts the date of the flyby as September 27. The countdown for the upcoming Earth flyby according to the ticker at ESA’s website more specifically puts the flyby at around 6:45 a.m. CDT on Monday, September 28, 2026. If this timing has revisions over the next couple weeks, we will update you!

ESA does not currently have a livestream planned for the event. But during the last Earth flyby, it did provide real-time updates.

JUICE launched to space in 2023. Its first gravity assist flyby was the first ever maneuver of its kind. On August 19 and 20, 2024, it swung past both the moon and then Earth. The flyby of the moon and Earth was technically a braking maneuver. It served to line JUICE up for a Venus flyby, where the successful gravity assist sped up the spacecraft, or gave it the juice, if you will. The Venus flyby was on August 31, 2025. Now there will be two more gravity assists, both at Earth. The first is on September 27, 2026, and the second is in January 2029. Then it will head out toward Jupiter, arriving in 2031.

This artist’s impression shows the JUICE spacecraft soaring in front of our planetary neighbor Venus. JUICE completed its flyby of Venus on August 31, 2025. Image via ESA.

JUICE mission launched on April 14, 2023

ESA’s JUICE mission launched on April 14, 2023, after a one-day delay due to lightning at ESA’s spaceport in French Guiana. The spacecraft lifted off successfully into cloudy skies, beginning a multi-year mission to Jupiter and its icy moons.

As often happens with missions to the outer solar system, the spacecraft will take a circuitous route to Jupiter, making multiple sweeps past the Earth, moon and Venus. Then, in 2031, it’ll arrive at the giant planet. At that time, it’ll perform 35 flybys of the Galilean moons Ganymede, Callisto and Europa, before going into orbit around the largest moon, Ganymede.

View larger. | This is JUICE’s journey to Jupiter. It will become a reality (fingers crossed) in July 2031, when JUICE is scheduled to arrive at Jupiter. It’s impressive, especially considering the spacecraft will still be soaring around Earth in 2029! Only when it has completed its 2nd flyby of our home planet will JUICE make a quick 2-year hop to Jupiter. There, it’ll complete 35 flybys of the giant planet’s 3 largest moons: Ganymede, Callisto and Europa. Image via ESA.

Jammed antenna

The JUICE mission’s primary antenna jammed soon after launch. But after three weeks of troubleshooting, engineers finally managed to fix the antenna. As the spacecraft traveled through deep space, JUICE mission control tried using thrusters to shake the antenna. Then they tried warming the jammed components in the sun’s rays. Finally, the team fired a mechanical device called an actuator. And that’s what made the antenna break free from its stuck position on May 12, 2023.

This RIME antenna, which stands for Radar for Icy Moons Exploration, will be used to study the structure of Jupiter’s icy moons down to a depth of 5.5 miles (9 km) when it finally reaches the gas giant in July 2031.

JUICE mission goals

ESA said its goals for JUICE are to:

… make detailed observations of the giant gas planet and its three large ocean-bearing moons – Ganymede, Callisto and Europa – with a suite of remote sensing, geophysical and in situ instruments.

And, ESA said, the mission will characterize these moons as both planetary objects and possible habitats.

ESA hopes that a wider study of the Jupiter system can be used as an archetype for gas giant planets and their moons across our Milky Way galaxy.

Why JUICE will study Europa

JUICE will arrive at Jupiter in 2031. One of the moons it will observe is perhaps the most fascinating of the Jovian moons to Earthly scientists: Europa. This moon is thought to have an ocean of liquid water under its icy crust (also made of water ice). And JUICE is designed to look for the sort of chemistry on Europa that is essential to life on Earth, for example organic molecules, or molecules containing carbon that are key to life on Earth.

JUICE also aims to understand the formation of Europa’s surface features and the composition of any non-water-ice material.

Why JUICE will study Ganymede

After a series of flybys of Jupiter and three of its large, icy moons, JUICE will eventually settle into an orbit around the largest moon, Ganymede. JUICE will orbit Ganymede down to 125 miles (200 km) for about three years. It’ll end its mission with an impact on the moon’s surface.

While at Ganymede, JUICE has many science objectives. They include:

• Characterization of the ocean layers and detection of possible subsurface water reservoirs.
• Topographical, geological and compositional mapping of the surface.
• Study of the physical properties of the icy crust.
• Characterization of the internal mass distribution, dynamics and evolution of the interior.
• Investigation of the exosphere.
• Study of Ganymede’s intrinsic magnetic field and its interactions with the Jovian magnetosphere.

Having a better understanding of this wet, cold world will also help us understand possible distant worlds around other suns, scientists say.

JUICE mocktails

Earlier this year, ESA had a little fun with the acronym JUICE, by holding a space juice contest. Check out these beautiful mocktails, and find the recipes here.

Having a little fun with the JUICE mission, these were the winners of ESA’s space juice contest. The mocktails included some made by 7 and 11-year-olds. Image via ESA.

JUICE art, from kids

ESA also invited kids from around the world to create JUICE-inspired artwork. Read more about the contest here. The winning entry – submitted by 8-year-old Yaryna from Ukraine – is going to space! It was painted on the Ariane 5 rocket, which launched JUICE.

Bottom line: The JUICE mission will perform a flyby of Earth on September 27, 2026. The spacecraft is headed toward Jupiter’s icy moons, where it will arrive in 2031.

Here’s what ‘habitable’ means to astronomers

Read more: Icy moons’ puzzling features may be due to salty ice

The post JUICE mission to fly by Earth in late September first appeared on EarthSky.

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This is an artist’s impression of the JUICE mission, which will target Jupiter’s icy moons. In this view, JUICE passes over Ganymede with Jupiter in the background. In order to get there, JUICE must first make 2 more flybys of Earth for gravity assists. Image via ESA (acknowledgement: ATG Medialab).

JUICE mission will fly by Earth in late September

The JUICE mission — which stands for JUpiter Icy Moons Explorer — is on its way to Jupiter, where it will explore its ocean-bearing moons. But its path to Jupiter is not straight. In fact, JUICE will swing by Earth in late September to get a gravity assist. This will be the third of four planned gravity assists to slingshot the spacecraft toward our solar system’s largest planet.

At the moment, ESA puts the date of the flyby as September 27. The countdown for the upcoming Earth flyby according to the ticker at ESA’s website more specifically puts the flyby at around 6:45 a.m. CDT on Monday, September 28, 2026. If this timing has revisions over the next couple weeks, we will update you!

ESA does not currently have a livestream planned for the event. But during the last Earth flyby, it did provide real-time updates.

JUICE launched to space in 2023. Its first gravity assist flyby was the first ever maneuver of its kind. On August 19 and 20, 2024, it swung past both the moon and then Earth. The flyby of the moon and Earth was technically a braking maneuver. It served to line JUICE up for a Venus flyby, where the successful gravity assist sped up the spacecraft, or gave it the juice, if you will. The Venus flyby was on August 31, 2025. Now there will be two more gravity assists, both at Earth. The first is on September 27, 2026, and the second is in January 2029. Then it will head out toward Jupiter, arriving in 2031.

This artist’s impression shows the JUICE spacecraft soaring in front of our planetary neighbor Venus. JUICE completed its flyby of Venus on August 31, 2025. Image via ESA.

JUICE mission launched on April 14, 2023

ESA’s JUICE mission launched on April 14, 2023, after a one-day delay due to lightning at ESA’s spaceport in French Guiana. The spacecraft lifted off successfully into cloudy skies, beginning a multi-year mission to Jupiter and its icy moons.

As often happens with missions to the outer solar system, the spacecraft will take a circuitous route to Jupiter, making multiple sweeps past the Earth, moon and Venus. Then, in 2031, it’ll arrive at the giant planet. At that time, it’ll perform 35 flybys of the Galilean moons Ganymede, Callisto and Europa, before going into orbit around the largest moon, Ganymede.

View larger. | This is JUICE’s journey to Jupiter. It will become a reality (fingers crossed) in July 2031, when JUICE is scheduled to arrive at Jupiter. It’s impressive, especially considering the spacecraft will still be soaring around Earth in 2029! Only when it has completed its 2nd flyby of our home planet will JUICE make a quick 2-year hop to Jupiter. There, it’ll complete 35 flybys of the giant planet’s 3 largest moons: Ganymede, Callisto and Europa. Image via ESA.

Jammed antenna

The JUICE mission’s primary antenna jammed soon after launch. But after three weeks of troubleshooting, engineers finally managed to fix the antenna. As the spacecraft traveled through deep space, JUICE mission control tried using thrusters to shake the antenna. Then they tried warming the jammed components in the sun’s rays. Finally, the team fired a mechanical device called an actuator. And that’s what made the antenna break free from its stuck position on May 12, 2023.

This RIME antenna, which stands for Radar for Icy Moons Exploration, will be used to study the structure of Jupiter’s icy moons down to a depth of 5.5 miles (9 km) when it finally reaches the gas giant in July 2031.

JUICE mission goals

ESA said its goals for JUICE are to:

… make detailed observations of the giant gas planet and its three large ocean-bearing moons – Ganymede, Callisto and Europa – with a suite of remote sensing, geophysical and in situ instruments.

And, ESA said, the mission will characterize these moons as both planetary objects and possible habitats.

ESA hopes that a wider study of the Jupiter system can be used as an archetype for gas giant planets and their moons across our Milky Way galaxy.

Why JUICE will study Europa

JUICE will arrive at Jupiter in 2031. One of the moons it will observe is perhaps the most fascinating of the Jovian moons to Earthly scientists: Europa. This moon is thought to have an ocean of liquid water under its icy crust (also made of water ice). And JUICE is designed to look for the sort of chemistry on Europa that is essential to life on Earth, for example organic molecules, or molecules containing carbon that are key to life on Earth.

JUICE also aims to understand the formation of Europa’s surface features and the composition of any non-water-ice material.

Why JUICE will study Ganymede

After a series of flybys of Jupiter and three of its large, icy moons, JUICE will eventually settle into an orbit around the largest moon, Ganymede. JUICE will orbit Ganymede down to 125 miles (200 km) for about three years. It’ll end its mission with an impact on the moon’s surface.

While at Ganymede, JUICE has many science objectives. They include:

• Characterization of the ocean layers and detection of possible subsurface water reservoirs.
• Topographical, geological and compositional mapping of the surface.
• Study of the physical properties of the icy crust.
• Characterization of the internal mass distribution, dynamics and evolution of the interior.
• Investigation of the exosphere.
• Study of Ganymede’s intrinsic magnetic field and its interactions with the Jovian magnetosphere.

Having a better understanding of this wet, cold world will also help us understand possible distant worlds around other suns, scientists say.

JUICE mocktails

Earlier this year, ESA had a little fun with the acronym JUICE, by holding a space juice contest. Check out these beautiful mocktails, and find the recipes here.

Having a little fun with the JUICE mission, these were the winners of ESA’s space juice contest. The mocktails included some made by 7 and 11-year-olds. Image via ESA.

JUICE art, from kids

ESA also invited kids from around the world to create JUICE-inspired artwork. Read more about the contest here. The winning entry – submitted by 8-year-old Yaryna from Ukraine – is going to space! It was painted on the Ariane 5 rocket, which launched JUICE.

Bottom line: The JUICE mission will perform a flyby of Earth on September 27, 2026. The spacecraft is headed toward Jupiter’s icy moons, where it will arrive in 2031.

Here’s what ‘habitable’ means to astronomers

Read more: Icy moons’ puzzling features may be due to salty ice

The post JUICE mission to fly by Earth in late September first appeared on EarthSky.

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Wildfires near the South Pole burned 90 million years ago

Scientists have found evidence of wildfires burning near the South Pole in Antarctica some 90 million years ago. The new evidence shows that the fires promoted peatlands in wet, swampy forests. Image via James McKay/ Alfred Wegener Institute.

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Wildfires near the South Pole burned 90 million years ago

Today, Antarctica is a vast, frozen landscape. A miles-thick ice sheet covers some 90% of the continent. But some 90 million years ago, during the Late Cretaceous period, scientists say this land was a rainforest where dinosaurs roamed. And on September 7, 2026, researchers with the Alfred Wegener Institute in Bremerhaven, Germany, said wildfires happened here regularly. In fact, they said they have found evidence in sediment cores of the southernmost wildfires ever recorded on Earth.

The researchers published their peer-reviewed paper in the journal Communications Earth and Environment on September 7, 2026.

The South Pole was once a rainforest

Back in 2020, researchers with the Alfred Wegener Institute (AWI) said they found evidence that a rainforest once existed in what is now Antarctica. They extracted a sediment core in an area that is currently in West Antarctica. That sediment core showed clear signs that a lush environment once existed here. Co-author Johann Klages of AWI said:

In a sediment core from the Amundsen Sea in West Antarctica, we found an extremely well-preserved forest soil dating back around 90 million years, containing abundant pollen and spores and a dense network of roots. During the Cretaceous, tectonic conditions meant that this temperate rainforest lay even farther south, just 900 kilometers [560 miles] from the South Pole.

Today, average annual temperatures at this location are around -30 Celsius [-22 F] and everything is covered by an ice sheet several kilometers thick. Our discovery showed that during the warmest period of the Cretaceous, when atmospheric CO2 levels were four to six times higher than today, a relatively warm and humid climate prevailed, even close to the South Pole.

In the new study, the researchers took a closer look at the sediment core and found clear evidence of recurring wildfires.

A closer look at the sediment core

The team found three pieces of evidence in the sediment core from the Late Cretaceous that pointed to recurring fires in this former rainforest.

First, the researchers found minute particles of charcoal. These tiny pieces became more abundant in the younger sediments. Their analysis showed the charcoal was mostly coming from soft conifer wood burning at low temperatures. These fires would be on the surface and not raging across the forest canopy.

Second, the researchers found amber. This amber is fossilized tree resin. In particular, the former tree resin here seems to have flowed over the tree trunks to protect and seal fire-damaged areas.

Third, the researchers found lots of spores of peat moss. Peat moss is a spongy soil made from dead plant matter. It decays slowly over thousands of years. This peat moss was the evidence that there were once raised bogs in Antarctica. The researchers link the formation of the bogs to the recurring fires.

This graph shows the sediment core the team extracted from Western Antarctica. It includes linescan and computed tomography images of the core, with the root network in green. Image via Alfred Wegener Institute/ Jürgen Titschack/ MARUM.

Imagining Antarctica from the past

So now imagine what Antarctica looked like 90 million years ago. First, the land was still partially connected to what is present-day Australia. The average temperature was 53 F (12 C). There were seasons of light and dark below the Antarctic Circle, along with dry periods and monsoon seasons. And sometimes, the monsoon season brought thunderstorms and associated lightning. The lightning struck Earth, igniting what would develop into large-scale fires.

Co-author Ulrich Salzmann of Northumbria University in England said:

90 million years ago, just 900 kilometers [560 miles] from the South Pole, a temperate and very swampy Antarctic rainforest with pronounced dry and monsoon seasons gradually silted up and developed into a peatland dominated by peat mosses.

Wildfires, which became increasingly frequent, clearly played a decisive role in this process. They kept the vegetation open and enabled the development of a peat bog where ground-level smoldering fires then occurred repeatedly, similar to those that have become increasingly common in German peatlands in recent years.

Wildfires near the South Pole and climate

The researchers explain how these boggy peatlands are important in climate change. Peatlands are a carbon sink, or a place where Earth stores its carbon. As co-author Thorsten Bauersachs of RWTH Aachen University said:

Peatlands play a key role in the climate system, both then and now, as highly effective long-term stores of carbon. In a warm climate, wetlands dry up more quickly and fires that prevent forest development occur more frequently. This can promote the formation of peatlands, where carbon-rich plant material accumulates over long periods.

Klages added:

The Late Cretaceous was extremely warm and prone to frequent fires. We were surprised to find evidence in our core of an early Antarctic ecosystem that, in many respects, resembled today’s Arctic raised bogs and also experienced regular fires.

Bottom line: Researchers have found evidence in a sediment core in Antarctica that wildfires near the South Pole were a regular occurrence some 90 million years ago.

Source: Co-evolution of wildfires and early Sphagnum-peatlands near the Cretaceous South Pole

Via Alfred Wegener Institute

Read more: A rainforest in Antarctica during the age of dinosaurs

Read more: Wildfires becoming more frequent in the north: See the maps

The post Wildfires near the South Pole burned 90 million years ago first appeared on EarthSky.

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Scientists have found evidence of wildfires burning near the South Pole in Antarctica some 90 million years ago. The new evidence shows that the fires promoted peatlands in wet, swampy forests. Image via James McKay/ Alfred Wegener Institute.

Love wildlife and the natural world? Get the latest animal stories – as well as space and night sky updates – delivered to your inbox.

Wildfires near the South Pole burned 90 million years ago

Today, Antarctica is a vast, frozen landscape. A miles-thick ice sheet covers some 90% of the continent. But some 90 million years ago, during the Late Cretaceous period, scientists say this land was a rainforest where dinosaurs roamed. And on September 7, 2026, researchers with the Alfred Wegener Institute in Bremerhaven, Germany, said wildfires happened here regularly. In fact, they said they have found evidence in sediment cores of the southernmost wildfires ever recorded on Earth.

The researchers published their peer-reviewed paper in the journal Communications Earth and Environment on September 7, 2026.

The South Pole was once a rainforest

Back in 2020, researchers with the Alfred Wegener Institute (AWI) said they found evidence that a rainforest once existed in what is now Antarctica. They extracted a sediment core in an area that is currently in West Antarctica. That sediment core showed clear signs that a lush environment once existed here. Co-author Johann Klages of AWI said:

In a sediment core from the Amundsen Sea in West Antarctica, we found an extremely well-preserved forest soil dating back around 90 million years, containing abundant pollen and spores and a dense network of roots. During the Cretaceous, tectonic conditions meant that this temperate rainforest lay even farther south, just 900 kilometers [560 miles] from the South Pole.

Today, average annual temperatures at this location are around -30 Celsius [-22 F] and everything is covered by an ice sheet several kilometers thick. Our discovery showed that during the warmest period of the Cretaceous, when atmospheric CO2 levels were four to six times higher than today, a relatively warm and humid climate prevailed, even close to the South Pole.

In the new study, the researchers took a closer look at the sediment core and found clear evidence of recurring wildfires.

A closer look at the sediment core

The team found three pieces of evidence in the sediment core from the Late Cretaceous that pointed to recurring fires in this former rainforest.

First, the researchers found minute particles of charcoal. These tiny pieces became more abundant in the younger sediments. Their analysis showed the charcoal was mostly coming from soft conifer wood burning at low temperatures. These fires would be on the surface and not raging across the forest canopy.

Second, the researchers found amber. This amber is fossilized tree resin. In particular, the former tree resin here seems to have flowed over the tree trunks to protect and seal fire-damaged areas.

Third, the researchers found lots of spores of peat moss. Peat moss is a spongy soil made from dead plant matter. It decays slowly over thousands of years. This peat moss was the evidence that there were once raised bogs in Antarctica. The researchers link the formation of the bogs to the recurring fires.

This graph shows the sediment core the team extracted from Western Antarctica. It includes linescan and computed tomography images of the core, with the root network in green. Image via Alfred Wegener Institute/ Jürgen Titschack/ MARUM.

Imagining Antarctica from the past

So now imagine what Antarctica looked like 90 million years ago. First, the land was still partially connected to what is present-day Australia. The average temperature was 53 F (12 C). There were seasons of light and dark below the Antarctic Circle, along with dry periods and monsoon seasons. And sometimes, the monsoon season brought thunderstorms and associated lightning. The lightning struck Earth, igniting what would develop into large-scale fires.

Co-author Ulrich Salzmann of Northumbria University in England said:

90 million years ago, just 900 kilometers [560 miles] from the South Pole, a temperate and very swampy Antarctic rainforest with pronounced dry and monsoon seasons gradually silted up and developed into a peatland dominated by peat mosses.

Wildfires, which became increasingly frequent, clearly played a decisive role in this process. They kept the vegetation open and enabled the development of a peat bog where ground-level smoldering fires then occurred repeatedly, similar to those that have become increasingly common in German peatlands in recent years.

Wildfires near the South Pole and climate

The researchers explain how these boggy peatlands are important in climate change. Peatlands are a carbon sink, or a place where Earth stores its carbon. As co-author Thorsten Bauersachs of RWTH Aachen University said:

Peatlands play a key role in the climate system, both then and now, as highly effective long-term stores of carbon. In a warm climate, wetlands dry up more quickly and fires that prevent forest development occur more frequently. This can promote the formation of peatlands, where carbon-rich plant material accumulates over long periods.

Klages added:

The Late Cretaceous was extremely warm and prone to frequent fires. We were surprised to find evidence in our core of an early Antarctic ecosystem that, in many respects, resembled today’s Arctic raised bogs and also experienced regular fires.

Bottom line: Researchers have found evidence in a sediment core in Antarctica that wildfires near the South Pole were a regular occurrence some 90 million years ago.

Source: Co-evolution of wildfires and early Sphagnum-peatlands near the Cretaceous South Pole

Via Alfred Wegener Institute

Read more: A rainforest in Antarctica during the age of dinosaurs

Read more: Wildfires becoming more frequent in the north: See the maps

The post Wildfires near the South Pole burned 90 million years ago first appeared on EarthSky.

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Why is Venus so bright in Earth’s sky?

View at EarthSky Community Photos. | Brian Mack captured this image on January 16, 2025, from Big Sur, California. Brian wrote: “Saturn and Venus low over the coast of Central California. The moon is just rising behind me, providing enough lighting for the landscape and ocean to expose in the photograph as well.” Thank you, Brian! Read on to find out why Venus is so bright.

In 2026, Venus emerged in the evening sky in February and will shine brightly in our evening sky through October. It will be at its brightest on September 18.

Why is Venus so bright?

Jupiter is a famously bright planet on our sky, and Mars can be impressively bright, too. But neither Jupiter nor Mars at their brightest can outshine Venus.

Our neighboring world – orbiting one step inward from Earth around the sun – is the third-brightest natural object in the sky, after the sun and the moon. It’s generally shining at around magnitude -4.0.

Venus reached its greatest distance from the evening sun in our sky on August 14-15, 2026. And the planet will be at its dazzling greatest brilliancy in the evening sky on September 18, 2026.

So why is Venus so bright?

Albedo = reflectivity

As the planet next inward from Earth in orbit around the sun, Venus is relatively nearby. But its nearness isn’t the only reason Venus is bright.

Consider that Mars orbits one step outward from Earth. And Mars waxes and wanes in brightness in our sky over about a two-year cycle. It’s only exceptionally bright around the time Earth passes between Mars and the sun, at the same time Mars is closest to the sun. The last time that happened was in 2018. And the next time will be in 2035.

With Venus, something else is going on. Astronomers use the term albedo to describe how bright a planet is in absolute terms. When sunlight strikes a planet, the planet’s surface absorbs some of the light and reflects the rest.

Albedo is a comparison between how much light strikes an object and how much the object reflects. And, as you might have guessed, Venus has the highest albedo of any major planet in our solar system.

Reflectivity makes Venus bright

The albedo of Venus is close to 0.7, meaning it reflects about 70% of the sunlight striking it. For context, the moon – whose surface is dark volcanic rock – reflects only about 10% of the light that hits it. It only appears brighter than Venus to us because it’s close to Earth. It’s only about a light-second away, in contrast to the several light-minutes distance of Venus.

Venus has a high albedo because it’s blanketed by highly reflective clouds. The clouds in the atmosphere of Venus contain droplets of sulfuric acid, as well as acidic crystals suspended in a mixture of gases. Light bounces easily off the smooth surfaces of these droplets and crystals. Sunlight bouncing from these clouds is a big part of why Venus is so bright.

By the way, Venus isn’t the most reflective body in our solar system. That honor goes to Enceladus, a moon of Saturn. The little moon’s icy surface reflects some 90% of the sunlight striking it.

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The phases of Venus – and its locations at inferior and superior conjunction – as viewed from Earth. Adapted from an image by NASA/ Chmee2/ Wikimedia Commons.

When and why is Venus brightest?

Venus is brightest when two factors combine: the phase of its crescent and the overall size of Venus’ disk in our sky. The combination of these factors dictates the amount of Venus’ surface area we see. When the greatest amount of surface area is visible, astronomers call it Venus’ greatest illuminated extent.

Why does it happen? Because Venus orbits the sun inside Earth’s orbit, it sometimes goes between us and the sun. At such times, its lit hemisphere, or day side, is facing away from us. Then it’s difficult to see Venus at all (though experienced astrophotographers sometimes catch it).

Also, around the time it passes between us and the sun – known as inferior conjunction – we see Venus exhibit phases … like a tiny moon (see chart above).

Venus will reach inferior conjunction on October 24, 2026. When Venus is racing toward inferior conjunction and catching up to Earth in our orbit, it’s increasing in size but its phases are shrinking (waning). Then, in October, it will “lap” us in the race of the planets. So, then observers on Earth can watch as the phase of Venus waxes.

As Venus moves away from its inferior conjunction, it’ll decrease in size … but its phase will increase. Smaller disk, but more of that disk visible.

View at EarthSky Community Photos. | Tameem Altameemi captured this image from Dubai and wrote: “This image beautifully captures a fascinating astronomical phenomenon: the similarity between the moon’s and Venus’ phases. Venus, like the moon, goes through phases as seen from Earth. This happens because Venus orbits inside Earth’s orbit, making it an inferior planet. The phase of Venus changes as its position relative to the sun and Earth shifts, like how the moon’s phases change.” Thank you, Tameem!

Venus at greatest brilliancy in September

Venus will pass between us and the sun at 4 UTC on October 24, 2026. Until then, it’ll be rushing to catch up with Earth in our orbit around the sun. Its phase will be decreasing, but its disk size will be increasing.

So there’s a balancing act going on between those two factors; the decreasing phase reduces brightness, but the growing disk size increases brightness. Venus’ greatest brilliancy happens when these two factors combine to give the greatest illuminated surface area. And that happens on September 18, 2026!

Don’t miss Venus blazing after twilight begins around then. Check Stellarium.org for local times.

The view from above

Heliocentric view of solar system, September 2026. Here you can see Venus is racing to catch up with Earth as we orbit around the sun. And Venus will reach its greatest brilliancy on September 18. Chart via Guy Ottewell’s 2026 Astronomical Calendar. Used with permission. Plus Guy Ottewell explains heliocentric charts here.

More photos from our community

View at EarthSky Community Photos. | Gwen Forrester of DeKalb County, Tennessee, captured these images on February 3, 2025. Gwen wrote: “Venus has been shining at its brightest recently, accompanied by the waxing crescent moon, as its own crescent phase wanes. Tonight, they were at roughly equal illumination as viewed from Earth.” Thank you, Gwen!

View at EarthSky Community Photos. | P Govardhana Siddartha of India submitted this composite image of Venus taken over 4 months. Venus was recorded from December 2024 to March 2025 as it raced toward inferior conjunction in March. You can see how the size of Venus increases and the phase decreases. Thank you, P Govardhana!

Bottom line: In 2026, dazzling Venus emerged in the west after sunset in the evening twilight in March. It will be visible in the evening sky through October. It’s the third brightest object in the sky, after the sun and moon. But why is Venus so bright?

Read about Venus at greatest brilliancy

Venus greatest distance from the sun August 14-15, 2026

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View at EarthSky Community Photos. | Brian Mack captured this image on January 16, 2025, from Big Sur, California. Brian wrote: “Saturn and Venus low over the coast of Central California. The moon is just rising behind me, providing enough lighting for the landscape and ocean to expose in the photograph as well.” Thank you, Brian! Read on to find out why Venus is so bright.

In 2026, Venus emerged in the evening sky in February and will shine brightly in our evening sky through October. It will be at its brightest on September 18.

Why is Venus so bright?

Jupiter is a famously bright planet on our sky, and Mars can be impressively bright, too. But neither Jupiter nor Mars at their brightest can outshine Venus.

Our neighboring world – orbiting one step inward from Earth around the sun – is the third-brightest natural object in the sky, after the sun and the moon. It’s generally shining at around magnitude -4.0.

Venus reached its greatest distance from the evening sun in our sky on August 14-15, 2026. And the planet will be at its dazzling greatest brilliancy in the evening sky on September 18, 2026.

So why is Venus so bright?

Albedo = reflectivity

As the planet next inward from Earth in orbit around the sun, Venus is relatively nearby. But its nearness isn’t the only reason Venus is bright.

Consider that Mars orbits one step outward from Earth. And Mars waxes and wanes in brightness in our sky over about a two-year cycle. It’s only exceptionally bright around the time Earth passes between Mars and the sun, at the same time Mars is closest to the sun. The last time that happened was in 2018. And the next time will be in 2035.

With Venus, something else is going on. Astronomers use the term albedo to describe how bright a planet is in absolute terms. When sunlight strikes a planet, the planet’s surface absorbs some of the light and reflects the rest.

Albedo is a comparison between how much light strikes an object and how much the object reflects. And, as you might have guessed, Venus has the highest albedo of any major planet in our solar system.

Reflectivity makes Venus bright

The albedo of Venus is close to 0.7, meaning it reflects about 70% of the sunlight striking it. For context, the moon – whose surface is dark volcanic rock – reflects only about 10% of the light that hits it. It only appears brighter than Venus to us because it’s close to Earth. It’s only about a light-second away, in contrast to the several light-minutes distance of Venus.

Venus has a high albedo because it’s blanketed by highly reflective clouds. The clouds in the atmosphere of Venus contain droplets of sulfuric acid, as well as acidic crystals suspended in a mixture of gases. Light bounces easily off the smooth surfaces of these droplets and crystals. Sunlight bouncing from these clouds is a big part of why Venus is so bright.

By the way, Venus isn’t the most reflective body in our solar system. That honor goes to Enceladus, a moon of Saturn. The little moon’s icy surface reflects some 90% of the sunlight striking it.

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The phases of Venus – and its locations at inferior and superior conjunction – as viewed from Earth. Adapted from an image by NASA/ Chmee2/ Wikimedia Commons.

When and why is Venus brightest?

Venus is brightest when two factors combine: the phase of its crescent and the overall size of Venus’ disk in our sky. The combination of these factors dictates the amount of Venus’ surface area we see. When the greatest amount of surface area is visible, astronomers call it Venus’ greatest illuminated extent.

Why does it happen? Because Venus orbits the sun inside Earth’s orbit, it sometimes goes between us and the sun. At such times, its lit hemisphere, or day side, is facing away from us. Then it’s difficult to see Venus at all (though experienced astrophotographers sometimes catch it).

Also, around the time it passes between us and the sun – known as inferior conjunction – we see Venus exhibit phases … like a tiny moon (see chart above).

Venus will reach inferior conjunction on October 24, 2026. When Venus is racing toward inferior conjunction and catching up to Earth in our orbit, it’s increasing in size but its phases are shrinking (waning). Then, in October, it will “lap” us in the race of the planets. So, then observers on Earth can watch as the phase of Venus waxes.

As Venus moves away from its inferior conjunction, it’ll decrease in size … but its phase will increase. Smaller disk, but more of that disk visible.

View at EarthSky Community Photos. | Tameem Altameemi captured this image from Dubai and wrote: “This image beautifully captures a fascinating astronomical phenomenon: the similarity between the moon’s and Venus’ phases. Venus, like the moon, goes through phases as seen from Earth. This happens because Venus orbits inside Earth’s orbit, making it an inferior planet. The phase of Venus changes as its position relative to the sun and Earth shifts, like how the moon’s phases change.” Thank you, Tameem!

Venus at greatest brilliancy in September

Venus will pass between us and the sun at 4 UTC on October 24, 2026. Until then, it’ll be rushing to catch up with Earth in our orbit around the sun. Its phase will be decreasing, but its disk size will be increasing.

So there’s a balancing act going on between those two factors; the decreasing phase reduces brightness, but the growing disk size increases brightness. Venus’ greatest brilliancy happens when these two factors combine to give the greatest illuminated surface area. And that happens on September 18, 2026!

Don’t miss Venus blazing after twilight begins around then. Check Stellarium.org for local times.

The view from above

Heliocentric view of solar system, September 2026. Here you can see Venus is racing to catch up with Earth as we orbit around the sun. And Venus will reach its greatest brilliancy on September 18. Chart via Guy Ottewell’s 2026 Astronomical Calendar. Used with permission. Plus Guy Ottewell explains heliocentric charts here.

More photos from our community

View at EarthSky Community Photos. | Gwen Forrester of DeKalb County, Tennessee, captured these images on February 3, 2025. Gwen wrote: “Venus has been shining at its brightest recently, accompanied by the waxing crescent moon, as its own crescent phase wanes. Tonight, they were at roughly equal illumination as viewed from Earth.” Thank you, Gwen!

View at EarthSky Community Photos. | P Govardhana Siddartha of India submitted this composite image of Venus taken over 4 months. Venus was recorded from December 2024 to March 2025 as it raced toward inferior conjunction in March. You can see how the size of Venus increases and the phase decreases. Thank you, P Govardhana!

Bottom line: In 2026, dazzling Venus emerged in the west after sunset in the evening twilight in March. It will be visible in the evening sky through October. It’s the third brightest object in the sky, after the sun and moon. But why is Venus so bright?

Read about Venus at greatest brilliancy

Venus greatest distance from the sun August 14-15, 2026

The post Why is Venus so bright in Earth’s sky? first appeared on EarthSky.

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Mercury is shrinking up to 30% more than expected

The MESSENGER spacecraft captured this view of Mercury in 2008. Scientists have long known Mercury is shrinking. But now they say it has shrunk up to 30% more than they thought. Image via NASA/ Johns Hopkins University Applied Physics Laboratory/ Carnegie Institution of Washington.

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Mercury is shrinking up to 30% more than expected

Astronomers have long known that Mercury is shrinking. In the few billion years since it was born in a series of fiery collisions, the planet has cooled and begun to shrink.

But on September 10, 2026, an international team of researchers said that the closest planet to the sun seems to have shrunk up to 30% more than they expected.

The signs of the planet’s shriveling are written right on its face in the form of wrinkles. Scientists call these wrinkles shortening structures. But craters and debris scattered across its surface from impacts have likely obscured even more evidence of its shrinking.

The researchers published their peer-reviewed study in the journal Geophysical Research Letters on September 10, 2026.

Cooling and shrinking

Our solar system began forming around 4.5 billion years ago. Mercury formed from planetesimals smashing together and heating up its interior. Then, over time, the planet cooled. Meanwhile, it was pelted with smaller material that left its mark on the planet’s surface.

This left Mercury with craters and debris from impacts, along with scarps and ridges from the cooling and shrinking. The new study, led by Gaku Nishiyama of the German Aerospace Center (DLR) Institute of Space Research, looked at how much shrinking Mercury might have undergone since its formation. This information can tell us more about Mercury’s interior and evolution. Nishiyama said:

More shrinking means Mercury could have a larger metal core, less light elements like silicon mixed into the metal core, or a higher starting temperature.

This MESSENGER image shows scarps on the surface of Mercury. MESSENGER captured the image during a fly-by on January 14, 2008. Image via NASA/ Johns Hopkins University Applied Physics Laboratory/ Carnegie Institution of Washington.

Mapping Mercury’s surface

The impact debris obscures the view of previous shrinkage and scarps on Mercury. So the researchers created a detailed map of Mercury’s surface to track the lumpiness. What they found was that the areas that were lumpiest show the fewest wrinkles. The team believes this is largely impact debris hiding evidence of older wrinkles and shrinkage. Nishiyama said:

It made us think that there’s a process obscuring shortening structures.

The press release described it as newly lain gravel covering up old ruts in a road.

Cooling should shrink Mercury uniformly. So the researchers then estimated how much shrinkage likely occurred planetwide based on the less obscured scarps. They then found the missing scarps could amount to 10% to 30% more shrinkage than previously estimated. The previous estimates of Mercury’s shrinkage were around 2.5 to 10 miles (4 to 16 km) in diameter. The new estimate puts it closer to 14.5 miles (23 km). Nishiyama said:

30% is a little bit surprising, but the corrected amount of contraction actually makes sense to me.

The MESSENGER spacecraft captured this receding view of Mercury as it flew away from the closest planet to the sun in 2008. Image via NASA/ Johns Hopkins University Applied Physics Laboratory/ Carnegie Institution of Washington.

Or maybe Mercury is shrinking even more than that?

Nishiyama said they could still be underestimating the amount of shrinkage on the closest planet to the sun. The team used data from the MESSENGER mission, which explored Mercury until 2015. But in just a couple of months, the BepiColombo mission will begin probing Mercury at even higher resolution. Maybe the new data will reveal Mercury has shrunk even more than the new estimates suggest. Stay tuned!

Bottom line: A new study shows Mercury is shrinking more than scientists first thought. The planet might have already shrunk up to 30% more than they expected.

Source: Underestimation of Planetary Contraction Due To Obscuration by Surface Roughness: The Case of Mercury

Via AGU

Read more: BepiColombo mission 1 step closer to Mercury today

Read more: Mercury’s sodium tail is now appearing in special filters

The post Mercury is shrinking up to 30% more than expected first appeared on EarthSky.

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The MESSENGER spacecraft captured this view of Mercury in 2008. Scientists have long known Mercury is shrinking. But now they say it has shrunk up to 30% more than they thought. Image via NASA/ Johns Hopkins University Applied Physics Laboratory/ Carnegie Institution of Washington.

Don’t miss the next unmissable night sky event. Sign up to EarthSky’s free newsletter for daily night sky updates.

Mercury is shrinking up to 30% more than expected

Astronomers have long known that Mercury is shrinking. In the few billion years since it was born in a series of fiery collisions, the planet has cooled and begun to shrink.

But on September 10, 2026, an international team of researchers said that the closest planet to the sun seems to have shrunk up to 30% more than they expected.

The signs of the planet’s shriveling are written right on its face in the form of wrinkles. Scientists call these wrinkles shortening structures. But craters and debris scattered across its surface from impacts have likely obscured even more evidence of its shrinking.

The researchers published their peer-reviewed study in the journal Geophysical Research Letters on September 10, 2026.

Cooling and shrinking

Our solar system began forming around 4.5 billion years ago. Mercury formed from planetesimals smashing together and heating up its interior. Then, over time, the planet cooled. Meanwhile, it was pelted with smaller material that left its mark on the planet’s surface.

This left Mercury with craters and debris from impacts, along with scarps and ridges from the cooling and shrinking. The new study, led by Gaku Nishiyama of the German Aerospace Center (DLR) Institute of Space Research, looked at how much shrinking Mercury might have undergone since its formation. This information can tell us more about Mercury’s interior and evolution. Nishiyama said:

More shrinking means Mercury could have a larger metal core, less light elements like silicon mixed into the metal core, or a higher starting temperature.

This MESSENGER image shows scarps on the surface of Mercury. MESSENGER captured the image during a fly-by on January 14, 2008. Image via NASA/ Johns Hopkins University Applied Physics Laboratory/ Carnegie Institution of Washington.

Mapping Mercury’s surface

The impact debris obscures the view of previous shrinkage and scarps on Mercury. So the researchers created a detailed map of Mercury’s surface to track the lumpiness. What they found was that the areas that were lumpiest show the fewest wrinkles. The team believes this is largely impact debris hiding evidence of older wrinkles and shrinkage. Nishiyama said:

It made us think that there’s a process obscuring shortening structures.

The press release described it as newly lain gravel covering up old ruts in a road.

Cooling should shrink Mercury uniformly. So the researchers then estimated how much shrinkage likely occurred planetwide based on the less obscured scarps. They then found the missing scarps could amount to 10% to 30% more shrinkage than previously estimated. The previous estimates of Mercury’s shrinkage were around 2.5 to 10 miles (4 to 16 km) in diameter. The new estimate puts it closer to 14.5 miles (23 km). Nishiyama said:

30% is a little bit surprising, but the corrected amount of contraction actually makes sense to me.

The MESSENGER spacecraft captured this receding view of Mercury as it flew away from the closest planet to the sun in 2008. Image via NASA/ Johns Hopkins University Applied Physics Laboratory/ Carnegie Institution of Washington.

Or maybe Mercury is shrinking even more than that?

Nishiyama said they could still be underestimating the amount of shrinkage on the closest planet to the sun. The team used data from the MESSENGER mission, which explored Mercury until 2015. But in just a couple of months, the BepiColombo mission will begin probing Mercury at even higher resolution. Maybe the new data will reveal Mercury has shrunk even more than the new estimates suggest. Stay tuned!

Bottom line: A new study shows Mercury is shrinking more than scientists first thought. The planet might have already shrunk up to 30% more than they expected.

Source: Underestimation of Planetary Contraction Due To Obscuration by Surface Roughness: The Case of Mercury

Via AGU

Read more: BepiColombo mission 1 step closer to Mercury today

Read more: Mercury’s sodium tail is now appearing in special filters

The post Mercury is shrinking up to 30% more than expected first appeared on EarthSky.

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2026 September equinox: All you need to know

Satellite views of Earth on the solstices and equinoxes. We are at the September equinox now. Read more about this image. Images via NASA Earth Observatory.

The September equinox is a seasonal milestone in Earth’s yearly orbit around the sun. At an equinox, the sun appears directly above Earth’s equator. At the September equinox, the sun is moving from north to south as it crosses above the equator. It’s bringing spring to the Southern Hemisphere and fall to the Northern Hemisphere.

The 2026 September equinox will fall at 00:05 UTC on September 23, 2026. That’s 19:05 p.m. CDT on September 22. And it’s 12:05 p.m. New Zealand Standard Time on September 23. On this day, days and nights are approximately (but not exactly) equal in length for everyone across the globe. The word equinox comes from the Latin aequus (equal) and nox (night), that is, equal night.

Keep reading to learn more about this important day.

Happy equinox! This artist’s concept of the September and March equinoxes isn’t to scale. But it illustrates the fact that every equinox is a milestone in Earth’s orbit around the sun. And it shows that, at the equinoxes, Earth’s Northern and Southern Hemispheres receive nearly equal amounts of daylight. Image via NASA/ GSFC/ Genna Duberstein.

Earth’s tilt causes it

The earliest humans spent more time outside than we do. They used the sky as both a clock and a calendar. And they could easily see that the sun’s path across the sky, the length of daylight and the location of the sunrise and sunset all shift in a regular way throughout the year.

The equinoxes and solstices happen because Earth tilts on its axis by 23 1/2 degrees. Because of the Earth’s tilt, the Northern and Southern Hemispheres trade places in receiving the sun’s light and warmth most directly. The solstices indicate our greatest (or least) tilt toward the sun, in either hemisphere. The equinoxes fall midway between the solstices.

Earth’s two hemispheres receive the sun’s rays about equally around equinox time. But Earth never stops moving in orbit around the sun. And these days of approximately equal daylight and night will change quickly as we move toward the December solstice. Maybe you’ve noticed that? The length of daylight changes more quickly from day to day around the equinoxes than around the time of the solstices.

Around the time of an equinox, Earth’s Northern and Southern Hemispheres are receiving the sun’s rays equally. However, that doesn’t mean that day and night are exactly equal in length. In fact, 2 factors cause more day than night during an equinox. Image via Wikipedia (CC BY-SA 2.0).

A good day to find due east and due west

The day of an equinox is a good day for finding the directions due east and due west from your favorite place to watch the sky. The sun rises due east and sets due west at the equinoxes. It’s true no matter where you live on Earth. Why? Because we all see the same sky.

Everywhere on Earth, except at the North and South Poles, you have a due east and due west point on your horizon. And each point marks the intersection of your horizon with the celestial equator, the imaginary line above the true equator of the Earth.

At the equinoxes, the sun appears overhead at local solar noon as seen from Earth’s equator, as the illustration below shows. The sun is on the celestial equator. The celestial equator intersects due east and due west for everyone around the globe. Therefore, the sun rises and sets due east and due west at the equinox.

So go outside around sunset or sunrise on the day of an equinox. Notice the location of the sun on the horizon with respect to familiar landmarks. If you do this, you’ll be able to use those landmarks to find those cardinal directions in the weeks and months ahead, long after Earth has moved on in its ceaseless orbit around the sun.

Illustration of the sun’s location on the celestial equator, every hour, on the day of an equinox, via Tau’olunga/ Wikimedia Commons (CC BY-SA 2.5).

Signs of the September equinox in nature

The signs that summer is gone – and winter is coming – are everywhere now on the northern half of Earth’s globe. In the Northern Hemisphere, dawn comes later, and sunset earlier. Also, notice the arc of the sun across the sky. It’s shifting southward now. And birds and butterflies are migrating south, along with the path of the sun.

The shorter days are bringing cooler weather. A chill is in the air. In New York City and other fashionable places, some people have stopped wearing white. Creatures of the wild are putting on their winter coats.

All around us, trees and plants are ending this year’s cycle of growth. Perhaps they’re responding with glorious autumn leaves, or a last burst of bloom before winter comes.

In the night sky, Fomalhaut – our Autumn Star – is making its way across the heavens each night.

Here’s Fomalhaut’s constellation Piscis Austrinus the Southern Fish. When you look toward this part of the sky, you’re looking out our galaxy’s south window into intergalactic space. Fomalhaut is bright! But the rest of the stars of Piscis Austrinus are tough to see without a dark sky. Chart via EarthSky.

Equinoxes and Earth’s seasons

The tilt of the Earth’s axis affects the amount of sunlight we each receive, on our various locations on the globe, as Earth travels around the sun. At the equinoxes, the sun in shining most evenly across Earth. Image via NASA.

Bottom line: The September equinox is here! It’ll arrive at 00:05 UTC on September 23, 2026. The sun will be exactly above Earth’s equator, moving from north to south. Autumn for the Northern Hemisphere. Spring for the Southern Hemisphere. Here’s all you need to know.

Read: Year’s fastest sunsets at equinox

Read more: Equinox shadows trace a straight line from west to east

The post 2026 September equinox: All you need to know first appeared on EarthSky.

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Satellite views of Earth on the solstices and equinoxes. We are at the September equinox now. Read more about this image. Images via NASA Earth Observatory.

The September equinox is a seasonal milestone in Earth’s yearly orbit around the sun. At an equinox, the sun appears directly above Earth’s equator. At the September equinox, the sun is moving from north to south as it crosses above the equator. It’s bringing spring to the Southern Hemisphere and fall to the Northern Hemisphere.

The 2026 September equinox will fall at 00:05 UTC on September 23, 2026. That’s 19:05 p.m. CDT on September 22. And it’s 12:05 p.m. New Zealand Standard Time on September 23. On this day, days and nights are approximately (but not exactly) equal in length for everyone across the globe. The word equinox comes from the Latin aequus (equal) and nox (night), that is, equal night.

Keep reading to learn more about this important day.

Happy equinox! This artist’s concept of the September and March equinoxes isn’t to scale. But it illustrates the fact that every equinox is a milestone in Earth’s orbit around the sun. And it shows that, at the equinoxes, Earth’s Northern and Southern Hemispheres receive nearly equal amounts of daylight. Image via NASA/ GSFC/ Genna Duberstein.

Earth’s tilt causes it

The earliest humans spent more time outside than we do. They used the sky as both a clock and a calendar. And they could easily see that the sun’s path across the sky, the length of daylight and the location of the sunrise and sunset all shift in a regular way throughout the year.

The equinoxes and solstices happen because Earth tilts on its axis by 23 1/2 degrees. Because of the Earth’s tilt, the Northern and Southern Hemispheres trade places in receiving the sun’s light and warmth most directly. The solstices indicate our greatest (or least) tilt toward the sun, in either hemisphere. The equinoxes fall midway between the solstices.

Earth’s two hemispheres receive the sun’s rays about equally around equinox time. But Earth never stops moving in orbit around the sun. And these days of approximately equal daylight and night will change quickly as we move toward the December solstice. Maybe you’ve noticed that? The length of daylight changes more quickly from day to day around the equinoxes than around the time of the solstices.

Around the time of an equinox, Earth’s Northern and Southern Hemispheres are receiving the sun’s rays equally. However, that doesn’t mean that day and night are exactly equal in length. In fact, 2 factors cause more day than night during an equinox. Image via Wikipedia (CC BY-SA 2.0).

A good day to find due east and due west

The day of an equinox is a good day for finding the directions due east and due west from your favorite place to watch the sky. The sun rises due east and sets due west at the equinoxes. It’s true no matter where you live on Earth. Why? Because we all see the same sky.

Everywhere on Earth, except at the North and South Poles, you have a due east and due west point on your horizon. And each point marks the intersection of your horizon with the celestial equator, the imaginary line above the true equator of the Earth.

At the equinoxes, the sun appears overhead at local solar noon as seen from Earth’s equator, as the illustration below shows. The sun is on the celestial equator. The celestial equator intersects due east and due west for everyone around the globe. Therefore, the sun rises and sets due east and due west at the equinox.

So go outside around sunset or sunrise on the day of an equinox. Notice the location of the sun on the horizon with respect to familiar landmarks. If you do this, you’ll be able to use those landmarks to find those cardinal directions in the weeks and months ahead, long after Earth has moved on in its ceaseless orbit around the sun.

Illustration of the sun’s location on the celestial equator, every hour, on the day of an equinox, via Tau’olunga/ Wikimedia Commons (CC BY-SA 2.5).

Signs of the September equinox in nature

The signs that summer is gone – and winter is coming – are everywhere now on the northern half of Earth’s globe. In the Northern Hemisphere, dawn comes later, and sunset earlier. Also, notice the arc of the sun across the sky. It’s shifting southward now. And birds and butterflies are migrating south, along with the path of the sun.

The shorter days are bringing cooler weather. A chill is in the air. In New York City and other fashionable places, some people have stopped wearing white. Creatures of the wild are putting on their winter coats.

All around us, trees and plants are ending this year’s cycle of growth. Perhaps they’re responding with glorious autumn leaves, or a last burst of bloom before winter comes.

In the night sky, Fomalhaut – our Autumn Star – is making its way across the heavens each night.

Here’s Fomalhaut’s constellation Piscis Austrinus the Southern Fish. When you look toward this part of the sky, you’re looking out our galaxy’s south window into intergalactic space. Fomalhaut is bright! But the rest of the stars of Piscis Austrinus are tough to see without a dark sky. Chart via EarthSky.

Equinoxes and Earth’s seasons

The tilt of the Earth’s axis affects the amount of sunlight we each receive, on our various locations on the globe, as Earth travels around the sun. At the equinoxes, the sun in shining most evenly across Earth. Image via NASA.

Bottom line: The September equinox is here! It’ll arrive at 00:05 UTC on September 23, 2026. The sun will be exactly above Earth’s equator, moving from north to south. Autumn for the Northern Hemisphere. Spring for the Southern Hemisphere. Here’s all you need to know.

Read: Year’s fastest sunsets at equinox

Read more: Equinox shadows trace a straight line from west to east

The post 2026 September equinox: All you need to know first appeared on EarthSky.

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See Venus in the daytime: Here are 3 tips

View at EarthSky Community Photos. | Steven Bellavia captured this image on February 7, 2025, in Virginia. Steven wrote: “Venus, in broad daylight, on a beautiful clear day. A little zoom-in, and you can see the crescent shape.” Thank you, Steven! Keep reading for tips on seeing Venus in the daytime.

• Venus is bright enough to see in daylight when the sky is clear and you know exactly where to look.
• One way is to use the moon as a guide. Or look when Venus is highest in the sky. Or, when Venus is up before sunrise, track it after sunrise.
• Never look at the sun with your unprotected eyes. When searching for Venus in daylight, position the sun behind a building.

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Why can you see Venus in daylight?

After the sun and moon, Venus is the brightest natural object in our sky.

It appears so bright because it’s relatively close to Earth, and is nearly as large as Earth. But, most importantly, Venus is covered with highly reflective clouds. It reflects approximately 75% of the sunlight shining on it back into space.

Still, Venus can be difficult to find against a bright blue sky. You need to know its location before you begin looking. How can you know at any given time whether Venus is up in the morning or the evening? A great way is to check EarthSky’s visible planets guide. It’s updated daily and will tell you when and where Venus is currently visible.

Or use an astronomy app such as Stellarium.

Right now – September 13, 2026 — Venus is in the west after sunset. It’ll pass between the Earth and sun on October 23-24, 2026. Afterwards, it’ll return to the east before dawn. You should begin to see it before dawn in early November, 2026.

Safety warning: Never look directly at the sun. Do not use binoculars, a telescope or a camera to search for Venus in daylight. If possible, stand where a tree trunk or building completely blocks the sun.

View at EarthSky Community Photos. | Paolo Palma captured this image on March 18, 2025, from Italy. To the unaided eye, Venus looks like a point of light. But magnified photographs can reveal its changing phases. Around the time the planet is passing between Earth and the sun, it’ll appear as a slim crescent in our sky. Venus will go between us and the sun next on October 23-24, 2026.

Tip #1 for seeing Venus in daylight: Use the moon

Venus is bright enough to appear as a tiny white point in a blue daytime sky. The easiest way to find it — when Venus is in the evening sky, as it is now – is to use the moon as a guide.

Then, on a clear sunny day, find the moon first with your unaided eyes. And use the app to determine which direction Venus lies from the moon and how far apart they appear. Venus will look like a tiny white point.

Remember to keep the sun hidden behind a building.

Shortly after sunset on September 13 and 14, the thin waxing moon will sweep past brilliant Venus. And Venus is at its greatest brilliancy this week! Be sure to step outside for this sweet sky scene. The farther south you are on Earth’s globe, the higher Venus will appear in your sky after sunset. The moon will occult, or pass in front of, Venus in daylight for people in Europe and Africa at 11 UTC on September 14. Few people (or nobody) will see the occultation. But many will see the moon exceptionally near Venus in the evening sky. The Southern Hemisphere has the best view! Read about the occultation here. Chart via EarthSky.

Tip #2: Look for Venus high in the sky

On days when Venus is above your horizon in daylight, it reaches its highest point in the sky as it crosses your local meridian (an imaginery line across the sky over your head, between your sky’s due north and due south points). Astronomers call this crossing a meridian transit, or culmination, of Venus.

Venus can be easier to find around this time because — at meridian transit — it’s as high above the horizon as it will be that day.

An astronomy app can provide the time of Venus’s meridian transit, along with its altitude, or height above your horizon. It’ll also give you the compass direction of Venus. That direction varies with your location, the season and the time of day. So follow the app rather than assuming Venus will be due south or north.

As always, before you look, position yourself so that a solid structure blocks the sun.

View at EarthSky Community Photos. | A magnified view of crescent Venus in daylight, captured four days before inferior conjunction. Steven Bellavia captured the image on March 18, 2025, in Virginia.

Tip #3: Track Venus after sunrise

Another way — useful when Venus comes back to the morning sky this November — is to locate Venus before sunrise and follow it as the sky brightens. Again, an astronomy app can also show you exactly where to look. But you don’t need an app. You can just watch. This is often the easiest method for finding Venus in daylight, but it only works when Venus is visible in the morning (which it will be, again, by early November 2026).

Just find the planet before sunrise, when it will be the brightest starlike object in that part of the sky. Note its position relative to a building, pole or other fixed landmark. Continue watching as the eastern sky brightens at dawn. Venus will become less obvious after sunrise, but, if you keep watching, you can keep it in view. If you look away, use your landmark to return to Venus as dawn is breaking.

Stop if the sun approaches your line of sight, and never use binoculars or a telescope to search for the planet.

Good luck!

Have you photographed Venus in daylight? Submit your image to EarthSky.

View larger. | One way to see Venus in daylight is to find it before sunrise and follow it as the sky brightens. Note its position relative to a foreground landmark so you can find it again. Always keep the sun safely out of view. Chart via EarthSky.

Bottom line: You can see Venus in daylight when the sky is clear and you know where to look. Use the moon as a guide, track Venus through sunrise or use an astronomy app to find it when it is highest in the sky. Always keep the sun safely out of view.

Source: Venus facts from NASA

Source: Eye safety from the American Astronomical Society

Read more: Why is Venus so bright?

Read more: Top 10 space objects to see during the day

The post See Venus in the daytime: Here are 3 tips first appeared on EarthSky.

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View at EarthSky Community Photos. | Steven Bellavia captured this image on February 7, 2025, in Virginia. Steven wrote: “Venus, in broad daylight, on a beautiful clear day. A little zoom-in, and you can see the crescent shape.” Thank you, Steven! Keep reading for tips on seeing Venus in the daytime.

• Venus is bright enough to see in daylight when the sky is clear and you know exactly where to look.
• One way is to use the moon as a guide. Or look when Venus is highest in the sky. Or, when Venus is up before sunrise, track it after sunrise.
• Never look at the sun with your unprotected eyes. When searching for Venus in daylight, position the sun behind a building.

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Why can you see Venus in daylight?

After the sun and moon, Venus is the brightest natural object in our sky.

It appears so bright because it’s relatively close to Earth, and is nearly as large as Earth. But, most importantly, Venus is covered with highly reflective clouds. It reflects approximately 75% of the sunlight shining on it back into space.

Still, Venus can be difficult to find against a bright blue sky. You need to know its location before you begin looking. How can you know at any given time whether Venus is up in the morning or the evening? A great way is to check EarthSky’s visible planets guide. It’s updated daily and will tell you when and where Venus is currently visible.

Or use an astronomy app such as Stellarium.

Right now – September 13, 2026 — Venus is in the west after sunset. It’ll pass between the Earth and sun on October 23-24, 2026. Afterwards, it’ll return to the east before dawn. You should begin to see it before dawn in early November, 2026.

Safety warning: Never look directly at the sun. Do not use binoculars, a telescope or a camera to search for Venus in daylight. If possible, stand where a tree trunk or building completely blocks the sun.

View at EarthSky Community Photos. | Paolo Palma captured this image on March 18, 2025, from Italy. To the unaided eye, Venus looks like a point of light. But magnified photographs can reveal its changing phases. Around the time the planet is passing between Earth and the sun, it’ll appear as a slim crescent in our sky. Venus will go between us and the sun next on October 23-24, 2026.

Tip #1 for seeing Venus in daylight: Use the moon

Venus is bright enough to appear as a tiny white point in a blue daytime sky. The easiest way to find it — when Venus is in the evening sky, as it is now – is to use the moon as a guide.

Then, on a clear sunny day, find the moon first with your unaided eyes. And use the app to determine which direction Venus lies from the moon and how far apart they appear. Venus will look like a tiny white point.

Remember to keep the sun hidden behind a building.

Shortly after sunset on September 13 and 14, the thin waxing moon will sweep past brilliant Venus. And Venus is at its greatest brilliancy this week! Be sure to step outside for this sweet sky scene. The farther south you are on Earth’s globe, the higher Venus will appear in your sky after sunset. The moon will occult, or pass in front of, Venus in daylight for people in Europe and Africa at 11 UTC on September 14. Few people (or nobody) will see the occultation. But many will see the moon exceptionally near Venus in the evening sky. The Southern Hemisphere has the best view! Read about the occultation here. Chart via EarthSky.

Tip #2: Look for Venus high in the sky

On days when Venus is above your horizon in daylight, it reaches its highest point in the sky as it crosses your local meridian (an imaginery line across the sky over your head, between your sky’s due north and due south points). Astronomers call this crossing a meridian transit, or culmination, of Venus.

Venus can be easier to find around this time because — at meridian transit — it’s as high above the horizon as it will be that day.

An astronomy app can provide the time of Venus’s meridian transit, along with its altitude, or height above your horizon. It’ll also give you the compass direction of Venus. That direction varies with your location, the season and the time of day. So follow the app rather than assuming Venus will be due south or north.

As always, before you look, position yourself so that a solid structure blocks the sun.

View at EarthSky Community Photos. | A magnified view of crescent Venus in daylight, captured four days before inferior conjunction. Steven Bellavia captured the image on March 18, 2025, in Virginia.

Tip #3: Track Venus after sunrise

Another way — useful when Venus comes back to the morning sky this November — is to locate Venus before sunrise and follow it as the sky brightens. Again, an astronomy app can also show you exactly where to look. But you don’t need an app. You can just watch. This is often the easiest method for finding Venus in daylight, but it only works when Venus is visible in the morning (which it will be, again, by early November 2026).

Just find the planet before sunrise, when it will be the brightest starlike object in that part of the sky. Note its position relative to a building, pole or other fixed landmark. Continue watching as the eastern sky brightens at dawn. Venus will become less obvious after sunrise, but, if you keep watching, you can keep it in view. If you look away, use your landmark to return to Venus as dawn is breaking.

Stop if the sun approaches your line of sight, and never use binoculars or a telescope to search for the planet.

Good luck!

Have you photographed Venus in daylight? Submit your image to EarthSky.

View larger. | One way to see Venus in daylight is to find it before sunrise and follow it as the sky brightens. Note its position relative to a foreground landmark so you can find it again. Always keep the sun safely out of view. Chart via EarthSky.

Bottom line: You can see Venus in daylight when the sky is clear and you know where to look. Use the moon as a guide, track Venus through sunrise or use an astronomy app to find it when it is highest in the sky. Always keep the sun safely out of view.

Source: Venus facts from NASA

Source: Eye safety from the American Astronomical Society

Read more: Why is Venus so bright?

Read more: Top 10 space objects to see during the day

The post See Venus in the daytime: Here are 3 tips first appeared on EarthSky.

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Crepuscular rays are sunrays in twilight skies

View at EarthSky Community Photos. | Sudhir Sharma photographed this on October 7, 2025, in India, and wrote: “While driving this afternoon we saw this amazing sunset with crepuscular rays.” Thank you, Sudhir!

What are crepuscular rays?

Crepuscular means resembling twilight or dim. This phenomenon occurs around sunrise or sunset, when the sun is below the horizon. And you can also see crepuscular rays when the sun is hiding behind clouds. They’re more noticeable when the sky is a bit darker and there is greater contrast between dark and light. We can see the rays of light thanks to dust, smoke or water droplets that scatter the light toward our eyes.

The darker streaks beside the sunrays are due to shadows, where the terrain or clouds block the sunlight from coming through. Sometimes those obstructions are below the horizon from your point of view, so it may not seem immediately clear what’s causing the darker rays.

When crepuscular rays extend from behind a cloud toward the ground, they also go by the nickname Jacob’s Ladder. The term comes from a story in the Bible where Jacob has a dream in which he sees a ladder leading up to the golden light of heaven with angels ascending and descending.

Parallel lines that seem to converge

Crepuscular rays appear to fan across the sky. But these sunrays are really parallel to each other. In fact, sometimes you can trace them all the way across the sky to the point on the horizon opposite the sunset. So, the next time you see them, remember to turn around. You might spot the fainter and less noticeable anticrepuscular rays. The illusion is similar to standing on train tracks and seeing how they appear to converge in the far distance in front of and behind you.

View at EarthSky Community Photos. | Ross Stone captured this image on July 15, 2026, from California and wrote: “With the summer heat of the Owens valley being unbearable, an afternoon trip into the White mountains is a must to escape the heat. As I reached the Sierra Vista lookout, I was treated to crepuscular rays crossing over Bishop, California, and the Eastern Sierra mountains.  It is beautifully majestic scenery, and a highlight of my summer (so far).” Thank you, Ross!

View at EarthSky Community Photos. | Cecille Kennedy captured this view on April 26, 2026, in Oregon. Cecille wrote: “Approaching sunset the sun was behind the clouds but shafts of light known as crepuscular rays, broke through the cloud layers. If you look closer there is a dark cloud triangle in the middle where some rays are also emanating. Sunrays (crepuscular rays) are a form of optical illusion based on perspective. While the sun’s rays are actually parallel, they appear to diverge or fan out from the sun due to linear perspective, similar to how parallel train tracks look like they converge in the distance.” Thank you, Cecille!

Photo gallery of crepuscular rays

All of these photos were contributed by EarthSky friends. Thanks for sharing your awesome photos with us! Would you like to contribute? Submit your image here.

View at EarthSky Community Photos. | Peter Lowenstein photographed this on February 25, 2026, in Zimbabwe. Peter wrote: “Following the development of rainbow pilei and cloud shadows above the prominent cumulus formation near Murahwa Mountain, the setting sun, which remained hidden, continued to shine brightly beyond and then produced a beautiful display of orange, red and magenta crepuscular rays adjacent to a broad cloud shadow which had developed above the cumulus remnant near the sunset point.” Thank you, Peter!

View at EarthSky Community Photos. | Palo Bardelli captured this image on April 30, 2026, in Italy and wrote: “A beautiful sunset with twilight rays created by low clouds. Venus, very bright, is almost in the center of the image.” Thank you, Palo!

View at EarthSky Community Photos. | Lorraine Boyd shared this image taken on January 2, 2026, in the UK. Lorraine wrote: “It was a beautiful & dramatic scene taking place in the sky, over the Washington County Grasslands. Known as Crepuscular Rays, the sunlight passes through breaks in the clouds, caused by tiny particles (dust, water droplets, haze) in the air scattering this sun light.” Thank you, Lorraine!

Marcy Curran captured this image of crepuscular rays from Wyoming on August 26, 2026.

Bottom line: Crepuscular rays are shadows in the sky of distant terrain or clouds. They form around twilight when particles in the atmosphere reflect the sun’s light beams toward our eyes. Sometimes you can see anticrepuscular rays on the horizon opposite the sun.

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The post Crepuscular rays are sunrays in twilight skies first appeared on EarthSky.

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View at EarthSky Community Photos. | Sudhir Sharma photographed this on October 7, 2025, in India, and wrote: “While driving this afternoon we saw this amazing sunset with crepuscular rays.” Thank you, Sudhir!

What are crepuscular rays?

Crepuscular means resembling twilight or dim. This phenomenon occurs around sunrise or sunset, when the sun is below the horizon. And you can also see crepuscular rays when the sun is hiding behind clouds. They’re more noticeable when the sky is a bit darker and there is greater contrast between dark and light. We can see the rays of light thanks to dust, smoke or water droplets that scatter the light toward our eyes.

The darker streaks beside the sunrays are due to shadows, where the terrain or clouds block the sunlight from coming through. Sometimes those obstructions are below the horizon from your point of view, so it may not seem immediately clear what’s causing the darker rays.

When crepuscular rays extend from behind a cloud toward the ground, they also go by the nickname Jacob’s Ladder. The term comes from a story in the Bible where Jacob has a dream in which he sees a ladder leading up to the golden light of heaven with angels ascending and descending.

Parallel lines that seem to converge

Crepuscular rays appear to fan across the sky. But these sunrays are really parallel to each other. In fact, sometimes you can trace them all the way across the sky to the point on the horizon opposite the sunset. So, the next time you see them, remember to turn around. You might spot the fainter and less noticeable anticrepuscular rays. The illusion is similar to standing on train tracks and seeing how they appear to converge in the far distance in front of and behind you.

View at EarthSky Community Photos. | Ross Stone captured this image on July 15, 2026, from California and wrote: “With the summer heat of the Owens valley being unbearable, an afternoon trip into the White mountains is a must to escape the heat. As I reached the Sierra Vista lookout, I was treated to crepuscular rays crossing over Bishop, California, and the Eastern Sierra mountains.  It is beautifully majestic scenery, and a highlight of my summer (so far).” Thank you, Ross!

View at EarthSky Community Photos. | Cecille Kennedy captured this view on April 26, 2026, in Oregon. Cecille wrote: “Approaching sunset the sun was behind the clouds but shafts of light known as crepuscular rays, broke through the cloud layers. If you look closer there is a dark cloud triangle in the middle where some rays are also emanating. Sunrays (crepuscular rays) are a form of optical illusion based on perspective. While the sun’s rays are actually parallel, they appear to diverge or fan out from the sun due to linear perspective, similar to how parallel train tracks look like they converge in the distance.” Thank you, Cecille!

Photo gallery of crepuscular rays

All of these photos were contributed by EarthSky friends. Thanks for sharing your awesome photos with us! Would you like to contribute? Submit your image here.

View at EarthSky Community Photos. | Peter Lowenstein photographed this on February 25, 2026, in Zimbabwe. Peter wrote: “Following the development of rainbow pilei and cloud shadows above the prominent cumulus formation near Murahwa Mountain, the setting sun, which remained hidden, continued to shine brightly beyond and then produced a beautiful display of orange, red and magenta crepuscular rays adjacent to a broad cloud shadow which had developed above the cumulus remnant near the sunset point.” Thank you, Peter!

View at EarthSky Community Photos. | Palo Bardelli captured this image on April 30, 2026, in Italy and wrote: “A beautiful sunset with twilight rays created by low clouds. Venus, very bright, is almost in the center of the image.” Thank you, Palo!

View at EarthSky Community Photos. | Lorraine Boyd shared this image taken on January 2, 2026, in the UK. Lorraine wrote: “It was a beautiful & dramatic scene taking place in the sky, over the Washington County Grasslands. Known as Crepuscular Rays, the sunlight passes through breaks in the clouds, caused by tiny particles (dust, water droplets, haze) in the air scattering this sun light.” Thank you, Lorraine!

Marcy Curran captured this image of crepuscular rays from Wyoming on August 26, 2026.

Bottom line: Crepuscular rays are shadows in the sky of distant terrain or clouds. They form around twilight when particles in the atmosphere reflect the sun’s light beams toward our eyes. Sometimes you can see anticrepuscular rays on the horizon opposite the sun.

Enjoying EarthSky? Sign up for our free daily newsletter today!

The post Crepuscular rays are sunrays in twilight skies first appeared on EarthSky.

from EarthSky https://ift.tt/HuTwQ76