Updated on: December 11, 2025 | By: Jameswebb Discovery Editorial Team

James Webb Telescope Uncovers Atmosphere on Sizzling Lava Planet TOI-561 b – A Super-Earth Defying All Odds with Magma Oceans and Thick Air (December 2025)

Picture a world so close to its star that its surface is a roiling sea of molten rock, with temperatures hot enough to melt steel in seconds. Now imagine that same planet clinging to a dense blanket of gases, refusing to let its atmosphere be stripped away by relentless stellar winds. That's the reality NASA's James Webb Space Telescope has revealed for TOI-561 b, an ultra-hot super-Earth that's rewriting the rules of planetary survival.This isn't just another exoplanet find – it's the strongest proof yet that rocky worlds baked by extreme radiation can hold onto substantial atmospheres. Webb's Near-Infrared Spectrograph (NIRSpec) peered at this distant inferno, uncovering a volatile-rich envelope above a global magma ocean. The discovery, detailed in a new paper in The Astrophysical Journal Letters, challenges long-held ideas about how small planets endure in hellish orbits.As astronomers dig deeper into Webb's data, TOI-561 b emerges as a key puzzle piece in understanding early planetary formation. Formed around an ancient star in a metal-scarce part of the galaxy, this planet could be a snapshot of what rocky worlds looked like billions of years ago. Let's dive into the details of this scorching breakthrough and what it means for the hunt for alien atmospheres.

The Hellish World of TOI-561 b: A Super-Earth on the Edge

TOI-561 b orbits a star about 280 light-years away in the constellation Scorpius. Discovered by NASA's TESS (Transiting Exoplanet Survey Satellite) in 2020, it's part of a fascinating multi-planet system. But what sets it apart is its extreme proximity to its host – a G-type star slightly smaller and cooler than our Sun, yet twice as old at around 10 billion years. With an orbital period of just 10.8 hours, TOI-561 b whips around its star at a distance of less than 1 million miles – that's 40 times closer than Mercury is to the Sun. This makes it tidally locked, with one side eternally facing the star in perpetual daylight, while the other lurks in endless night. The dayside faces blistering radiation, estimated at 2,500 times what Earth receives, pushing surface temperatures well beyond 2,000 °C.At first glance, you'd expect TOI-561 b to be a barren, airless rock – much like many "lava worlds" theorized in exoplanet science. But its density tells a different story. Clocking in at about 3.0 grams per cubic centimeter (compared to Earth's 5.5 g/cm³), it's puffier than a pure rock-iron composition would suggest. "What really sets this planet apart is its anomalously low density," explains lead researcher Johanna Teske from Carnegie Science's Earth and Planets Laboratory. "It’s not a super-puff, but it is less dense than you would expect if it had an Earth-like composition."This low density hinted at something extra – perhaps a lighter mantle made of low-density silicates, or maybe an atmosphere adding bulk. Given the star's age and location in the Milky Way's thick disk – a region poor in heavy elements – TOI-561 b likely formed from a primordial mix of materials, lacking the iron-rich core we see in our solar system's rocky planets. This chemical heritage could make it a relic of the Universe's early days, when stars and planets were forged from simpler building blocks.

Webb's Infrared Eyes Pierce the Heat: Detecting the Atmosphere

To unravel the mystery, an international team turned to JWST's NIRSpec for a marathon observation session in May 2024. Over 37 hours – covering nearly four full orbits of TOI-561 b – the telescope captured the planet's secondary eclipses, when it dips behind its star from our viewpoint. This method measures the planet's own infrared glow, separate from the star's light. If TOI-561 b were a bare magma world with no atmosphere, its dayside should radiate like a blackbody at around 2,700 °C. But the data showed something cooler: about 1,800 °C. That's still hotter than Venus's surface, but far below predictions for an airless rock.The emission spectrum – plotting brightness across near-infrared wavelengths – revealed telltale signs of atmospheric interference. Strong absorption at certain wavelengths suggests gases like water vapor or carbon dioxide soaking up heat, while possible silicate clouds high in the atmosphere could reflect incoming starlight, acting like a planetary sunscreen.Co-author Anjali Piette from the University of Birmingham notes, "We really need a thick volatile-rich atmosphere to explain all the observations. Strong winds would cool the dayside by transporting heat over to the nightside. Gases like water vapor would absorb some wavelengths of near-infrared light emitted by the surface before they make it all the way up through the atmosphere."This isn't a flimsy veil of vapor – it's a substantial envelope, potentially rich in volatiles boiled off from the magma below. Tim Lichtenberg from the University of Groningen describes the dynamic: "There is an equilibrium between the magma ocean and the atmosphere. At the same time that gases are coming out of the planet to feed the atmosphere, the magma ocean is sucking them back into the interior. "Webb's data rules out a thin rock-vapor layer as the sole cause; only a thick, heat-trapping atmosphere fits. The team is now analyzing phase-curve data (how brightness changes as the planet orbits) to map temperatures globally and pinpoint exact gas compositions.

The Magma Ocean Below: A Boiling Cauldron of Rock and Gas

Beneath this unexpected atmosphere lies TOI-561 b's defining feature: a global magma ocean. With dayside heat melting any solid crust, the surface is a vast sea of liquid rock, perhaps thousands of kilometers deep. This isn't like Earth's occasional volcanoes – it's a planet-wide lava lake, churning with convection currents that recycle materials.The magma ocean plays a crucial role in the atmosphere's survival. As heat causes silicates to evaporate, volatiles like water, carbon, and sulfur compounds bubble up, sustaining the gaseous layer. But why doesn't the star's radiation blow it all away? The answer may lie in the ocean's "sucking back" effect – a feedback loop where heavy gases rain down and dissolve back into the melt, while lighter ones escape more slowly.This setup evokes comparisons to early Earth or Venus, but on steroids. On Venus, a runaway greenhouse turned the planet into a pressure cooker. TOI-561 b might represent an extreme end-state: a stable "lava atmosphere" world where outgassing balances loss.

Comparing TOI-561 b to Other Lava Worlds and Super-Earths

TOI-561 b isn't alone in its fiery existence, but it's unique in having a confirmed thick atmosphere. JWST has spotlighted several "lava worlds" recently, offering points of comparison.For instance, 55 Cancri e, another super-Earth, shows hints of a volatile atmosphere (possibly carbon monoxide or dioxide) above its magma surface, based on JWST observations in 2024. Like TOI-561 b, it's tidally locked and ultra-hot, but orbits a younger star. The key difference? 55 Cancri e's density suggests a more Earth-like core, while TOI-561 b's puffiness points to lighter materials overall.Then there's K2-141 b, a lava planet with rock-vapor winds, modeled as having extreme day-night contrasts. Without Webb's direct spectral data, its atmosphere remains theoretical – but TOI-561 b's cooling effect suggests similar heat transport via gases.Closer to home, the TRAPPIST-1 system hosts rocky planets like TRAPPIST-1 b and c, which JWST studied in 2023–2024. These are cooler than TOI-561 b but show no thick atmospheres, aligning with expectations for irradiated worlds. TOI-561 b bucks the trend, perhaps because its magma ocean actively replenishes gases.Broader super-Earths like LHS 3844 b (observed by Spitzer) appear airless, with bare rock surfaces. TOI-561 b's discovery implies that factors like star age, composition, and volatile content determine if atmospheres persist. In metal-poor environments like the thick disk, planets might start with more volatiles trapped in lighter mantles, aiding retention.Even fictional worlds come to mind – think Mustafar from Star Wars, a lava hellscape. But TOI-561 b is real, and its atmosphere adds a layer of intrigue: Could microbial life hide in cooler high-altitude clouds? Unlikely at these temperatures, but it sparks questions about extreme habitability.

Implications for Exoplanet Habitability and Future Searches

TOI-561 b's resilient atmosphere has ripple effects across exoplanet science. If even the hottest rocky worlds can maintain air, then milder super-Earths in habitable zones might be more likely to have stable climates.This ties into the search for biosignatures. Atmospheres are key to detecting life – they hold gases like oxygen or methane that could signal biology. Webb's success here boosts confidence in upcoming programs targeting cooler worlds, like those in the habitable zones of red dwarfs.For lava worlds specifically, TOI-561 b suggests a new class: "equilibrium magma-atmosphere planets." These could be common around old stars, where initial volatile stores haven't fully escaped. Future missions like ARIEL (ESA, launching 2029) could survey dozens more, mapping their compositions.The discovery also highlights JWST's versatility. As the premier infrared observatory, it's uniquely suited to study hot exoplanets' thermal emissions. With over 5,000 confirmed exoplanets and thousands more candidates from TESS, Webb's queue is packed – but finds like this justify the wait.On a broader scale, TOI-561 b underscores the diversity of rocky worlds. Earth isn't the template; super-Earths dominate in the galaxy, and understanding their extremes helps contextualize our own planet's evolution. As Teske puts it, "This planet must be much, much more volatile-rich than Earth to explain the observations."

What's Next for TOI-561 b and JWST Exoplanet Hunts

The team isn't done yet. Ongoing analysis of the full 37-hour dataset will yield a global temperature map, revealing how heat flows from day to night. Transmission spectroscopy – watching starlight filter through the atmosphere during transits – could nail down exact gases like H2O or CO2.Beyond TOI-561 b, JWST has a slate of lava world targets: CoRoT-7 b, Kepler-10 b, and others. Combined with ground-based observatories like the Extremely Large Telescope (ELT), we'll build a census of atmospheric survival on hot rocks.In the bigger picture, this bolsters NASA's push for exoplanet science, from Habitable Worlds Observatory concepts to ongoing TESS and PLATO missions. As we hunt for Earth 2.0, understanding hellish cousins like TOI-561 b sharpens our tools.TOI-561 b reminds us: The Universe is full of survivors. Even in the face of stellar fury, planets find ways to hold on – a testament to nature's resilience across the stars.

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