Despite the name, the universe’s white dwarfs can glow in a wide range of colors—even green. For the first time, astronomers have spotted a star that appears green to the human eye, and the reddest ever recorded. These outlier stars help explain how certain white dwarf stars would shine in green, pink, cyan, yellow, and purple if we actually saw them up close in space. These colorful findings are described in a study recently published in the journal RAS Techniques and Instruments.

Looking for the ‘perfect radiator’

White dwarf stars are the dense remnants left behind after stars like our sun reach the end of their lifespan. For most stars, their color gives a hint to their temperature. Cooler stars appear orange, warm stars like our sun look white. The hottest glow pale blue, similar to how a blacksmith’s iron will go from red to orange to white hot. Astronomers believed that white dwarfs followed this same rule. They even earned their name after the earliest examples were surprisingly hot and glowed in a white/pale blue. 

“Most stars, including most white dwarfs, behave like ‘perfect radiators,’ so their colour is set almost entirely by temperature. But nobody had really looked into what else might be possible for white dwarfs,” Mark Hollands, a study co-author and astronomer at the University of Warwick in England, said in a statement. “It turns out these incredibly dense stars can produce colours nobody expected, and some of them genuinely surprised me.” 

According to the team, the key to these colors is density. The atmospheres surrounding the coolest white dwarfs can reach about the same density as water (roughly 1 gram per cubic centimeter). They are also millions of times denser than the sun’s photosphere, the lowest layer of its atmosphere. Under these higher density conditions, any trace elements present (carbon, calcium, sodium, etc.) interact with the surrounding dense helium plasma. As they interact with the plasma, they can absorb light across a wider spectrum of colors than they would at lower densities. This then shifts the star’s color away from the more typical orange, white, and blue.

Unfortunately, no white dwarf sky is close enough for its color to be seen directly. Instead, the team calculated their color from data astronomers routinely collect—a star’s spectrum. The spectrum is a “fingerprint” that’s produced when starlight splits apart by wavelength, similar to how a prism splits sunlight into a rainbow. Astronomers ran these spectra through a computer model of what colors human vision can see to check what color a star’s light would appear to our eyes. 

The first green and the reddest red

The team applied this method to several white dwarfs across the cosmos. They found that their colors fall into distinct groups linked to what makes up a star’s atmosphere. Carbon-rich white dwarfs generally appear pink or purple. Stars enriched with debris from busted asteroids and comets, the remains of old planetary systems, tend to be more yellow. Cooler white dwarfs with atmospheres of mixed hydrogen and helium show a more cyan or pale blue tinge. This cyan-pale blue is caused by hydrogen molecules colliding with helium atoms inside their ultra-dense atmospheres.  

The most striking example is WD J1330+6435. This star is about 7,232 degrees Fahrenheit (4,000 degrees Celsius) and around 284 light-years away from Earth. Over time, it has gathered rocky material from its planetary system. All of this extra material enriched its atmosphere with calcium, lithium, and sodium. The result—a chartreuse green appearance in the team’s models. As far as the researchers are aware, no other star (living or dead) has ever been credibly reported as green.

“The traces of sodium in the atmosphere of this white dwarf absorb the orange part of the spectrum, leaving behind a ghostly green glow,” added Hollands. “Imagine standing on a planet and looking up at a green star. It feels like something out of science fiction.” 

On the opposite end of the spectrum, the team identified what could be the reddest star ever recorded—WD J1011+2845. This white dwarf is only 48 light-years away from Earth, and has a deep convection zone. This zone is full of carbon that’s been lifted up from the star’s core to its surface. The carbon molecules then distort the star’s light so much that almost all of it is squeezed into wavelengths beyond 600 nanometres. This wavelength produces an unusual deep salmon-pink glow.

What are the odds?

The team also studied 151 white dwarfs located within about 65 light-years (20 parsecs) from Earth. Only five of these showed unusual colors, two yellow and three pink. This suggests that about 1 in 30 of the universe’s white dwarfs shine with an unusually colored light. 

The team then measured the color temperature of the remaining 146 white dwarfs. Color temperature is commonly used to describe light bulbs using degrees Kelvin—warm white at 3,000K, cool white at 6,000 K, etc. The median color temperature of the sample was approximately 6,800K, which our eyes perceive as white. This measurement corrects a common misconception that white dwarfs are typically blue. The hotter and bluer white dwarfs are mostly brighter, so they can be seen from further away and are over-represented in surveys that only look at a star’s brightness.

“One in thirty might not sound like a huge fraction, but across the entire population of white dwarfs in the Universe, that is still a lot of oddly coloured stars out there,” added study co-author and University of Warwick astronomer Boris Gänsicke. “Yet if we take the median across a representative population of white dwarfs, we found that the average white dwarf really is white.”

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It’s true, the moon is shrinking. And astronomers now know how fast it’s contracting. While only satellite observations and the most delicate instruments can detect these shifts, the consequences of this shrinkage means moonquakes can occur anywhere on the lunar surface at a moment’s notice.

A team led by Smithsonian National Air and Space Museum planetary geologist Thomas Watters detailed their findings in a study recently published in The Planetary Science Journal. Researchers used data from NASA’s Lunar Reconnaissance Orbiter Camera (LROC), which has spent over 17 years generating millions of images of the moon’s surface. A shriveling lunar landscape may sound dramatic, but it’s occurring at a glacial pace. Based on these new calculations, the moon’s overall radius has decreased nearly 148 feet over the last 400–800 million years as it continues to cool. That’s about 2.4 to 4.3 inches per million years, or just 0.1 micrometer annually.

Although slow, the incremental activity’s effects are visible everywhere. On Earth, about 90 percent of all seismic activity occurs near the boundaries between lithospheric plates. But unlike its host planet, our moon is encased by a single, shell-like plate. This means interior cooling can generate slips and faults anywhere at any given time. After reviewing images taken by the LROC, the study’s authors tallied over 10,000 visible lunar faults.

“The number of these young faults revealed in LROC images is much greater than I ever imagined,” said Watters. “As the interior of the moon continues to cool and contract, it is expected that the growth of existing faults and formation of new faults continues today.”

While the faults can happen anywhere, some lunar regions are more likely than others to feature them. Areas with the thickest crust have fewer faults, which indicates they may be more stable than other, thinner sections. In addition to better understanding lunar history, the distribution and frequency of moonquakes may also help NASA better plan for a long-term human presence on the moon.

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NASA’s Perseverance Mars rover has officially traveled 28.10 miles—farther across another planet’s surface than any other vehicle in history. Not only that, but the six-wheeled science lab accomplished this impressive feat almost entirely autonomously and in barely a third the time it took the previous recordholder.

“The original mission called for no more than 12.4 miles of driving. We’ve blown well past that,” Steven Lee, Perseverance and Curiosity project manager at NASA’s Jet Propulsion Laboratory, said in a statement.

Perseverance began operations on Mars on February 18, 2021, after landing in an ancient river delta selected for potential past microbial life called Jezero Crater. Since then, the rover has slowly but steadily made its way across the region, while conducting multiple sediment drilling surveys. These samples are then chemically analyzed using onboard laboratory equipment before the results are sent back to mission specialists at NASA.

Perseverance surpassed the previous travel record of 28.06 miles set by NASA’s Opportunity rover, before its communications with NASA ended on June 10, 2018. However, it took Opportunity nearly 15 years to accrue its distance while Perseverance exceeded the same mileage in less than six years, and on the 2,006th Martian day (sol) of its mission. Perseverance is currently traveling towards an area named Idubi through an expanse nicknamed “Lac de Charmes.” The region near Jezero Crater’s western rim hosts what may be the oldest landscape ever investigated in the solar system. Mars does not feature tectonic plates like Earth, which means its terrain is never eroded and subsumed into the planet’s substrates.

Mission engineers have not spent the last six years remotely steering Perseverance, either. The rover arrived on Mars equipped with a self-piloting system called AutoNav, which constructs 3D maps of the immediate surroundings to flag any potential hazards. AutoNav then charts a route between specific waypoints chosen by NASA specialists back home. Perseverance has completed 90 percent of its total excursion with AutoNav. Opportunity and its sibling rover, Spirit, only relied on a first version of the piloting system about five percent of the time.

Perseverance has a long road ahead of it, if all goes according to plan. In October, NASA approved the first mission extension that will continue the rover’s operations through about the end of 2028.

“With all mobility systems fully operational and favorable extended-ground-life test results, we expect Perseverance to keep adding to this record for many years to come,” added Lee.

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Successfully sending Artemis II astronauts on their historic lunar flyby earlier this year required some of the latest and most precise technologies, but not everything in this mission needed the same intense equipment. As crewmates gazed through Orion’s capsule window at the moon’s eclipse of the sun on April 6, 2026, three of the travelers needed a way to easily sketch some of their preliminary observations. They took turns writing their notes on a shared tablet PC—and NASA has recently highlighted their work with a screenshot of their efforts.

Astronauts Reid Wiseman, Victor Glover, Christina Koch, and Jeremy Hansen had a lengthy list of tasks during their 10-day, 700,000-mile roundtrip. One of the most visually dramatic jobs involved carefully assessing lunar activity while passing across the moon’s dark side from a distance of about 46,000 miles away. The roughly hour-long observation period provided astronauts with an unprecedented opportunity to record meteorite activity.

The tablet screenshot includes notes taken by Wisemen (in blue), Hansen (in red), and Glover (in green) during the moon’s eclipse of the sun. The crew collectively spotted at least five faint flashes of light caused by impacts. According to Wiseman, the first three impacts occurred within about 10 minutes into their observations, while another two happened later during the flyby. Impacts two and four were likely also corroborated by Hansen and Glover.

Since the moon does not have an atmosphere like Earth’s, the lunar surface is regularly bombarded by space rocks. Most of them are comparatively small, but they will still pose a problem for future crewed trips to the surface,especially those stationed in a planned permanent lunar base. The data gathered by Artemis II on April 6 will help NASA better understand these dynamics, and plan for the safest environments possible for their astronauts.

Artemis II’s astronauts safely returned to Earth during a splashdown off the coast of San Diego at 8:07 p.m. EDT on April 11. If all goes as planned, Artemis III’s crew will launch on their mission no earlier than June 2027.

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This curious cloud requires no solid particles to seed its formation — a theoretical phenomenon that's never been observed until now.

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