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TRAPPIST-1 / Temperate Earth-sized planets transiting a nearby ultracool dwarf star - publication
2016-05-02 08:00 - 2023-08-12 17:00 (Europe/Amsterdam)
TRAPPIST-1, ook als 2MASS J23062928-0502285 aangeduid, is een ultrakoele (temperatuur < 2700 K) dwergster die zich op 40,66 lichtjaar (12 parsec) van de Aarde bevindt in het sterrenbeeld Waterman. Om de ster draaien (ten minste) zeven exoplaneten.
Een team van astronomen, geleid door Michaël Gillon van het Institut d’Astrophysique et Géophysique te Luik, België, gebruikte de TRAPPIST (Transiting Planets and Planetesimals Small Telescope)-telescoop van het La Silla-observatorium in de Atacamawoestijn in Chili om de ster en haar planeten te observeren. Door het gebruik van transitfotometrie vond men drie planeten met aardachtige afmetingen die rond de dwergster draaien. De twee binnenste planeten bevinden zich in synchrone rotatie tegenover de ster, terwijl de derde zich juist binnen de bewoonbare zone bevindt ofwel juist erbuiten. Het team deed de waarnemingen van september tot en met december 2015 en publiceerde zijn bevindingen in het tijdschrift Nature van mei 2016. Op 22 februari 2017 vonden astronomen nog vier bijkomende planeten rond TRAPPIST-1. Dit brengt het aantal planeten rond de ster op zeven. De vier nieuw-ontdekte planeten bevinden zich vrij zeker in de bewoonbare zone.
De naam TRAPPIST-1 komt van de ontdekkende telescoop TRAPPIST, met een 1 omdat dit de eerste ster met planeten is die met deze telescoop ontdekt werd. De aanduiding van planeten gebeurt in volgorde van ontdekking: b is voor de eerste planeet die rond de ster draait, c voor de tweede en zo voorts. In het geval van TRAPPIST-1 werden er eerst drie ontdekt, die dus werden aangeduid met b, c en d, in volgorde van toenemende omwentelingsperiode. Daarna volgen e tot h voor de latere ontdekkingen. TRAPPIST-1 is een ultrakoele ster die een massa heeft van ongeveer 8% van die van de Zon en een diameter van 11% van de Zon. De temperatuur aan de oppervlakte bedraagt 2550 K. De ster is minstens 500 miljoen jaar oud. Door haar massa kan de ster 4 tot 5 biljoen jaar oud worden. Ter vergelijking: de Zon is 4,6 miljard jaar oud en heeft een oppervlaktetemperatuur van 5778 K. TRAPPIST-1 staat ongeveer 39 lichtjaar van de Aarde, maar ondanks deze relatief korte afstand is TRAPPIST-1 niet met het blote oog te zien en zelfs niet met een grote amateurtelescoop. De ster is rijk aan metalen. Zij bevat 109% van de hoeveelheid ijzer (Fe) die de Zon bevat. Haar luminositeit bedraagt 0,04% van de Zon.
Het volledige systeem (ster plus planeten) past binnen de baan van Mercurius. Het systeem is beter te vergelijken met dat van Jupiter en zijn manen dan met het zonnestelsel. Alle zeven bekende planeten van TRAPPIST-1 draaien veel dichter rond hun ster dan de Aarde rond de Zon draait. De afstand tussen de omloopbanen van TRAPPIST-1b en TRAPPIST-1c is slechts 1,6 maal de afstand tussen de Aarde en de Maan. De planeten zijn voortdurend zichtbaar vanaf elkaars oppervlak en soms lijken ze groter dan de Maan vanaf de Aarde. De omwentelingstijd van de planeet het dichtst bij de ster is 1,5 aardse dag. De zesde planeet doet er 12,3 dagen over. Van de zevende is de omloopsnelheid niet precies gekend, omdat er nog maar één transitie is waargenomen. Men schat hem tussen de 14 en 35 dagen. De getijdengebonden planeten hebben altijd dezelfde kant naar de ster gericht. Daardoor zijn de temperatuurverschillen zeer groot. Eventueel leven kan zich slechts op de dag-/nachtovergang bevinden. Als er een atmosfeer is, waaien er waarschijnlijk zeer sterke winden. Rode dwergen stoten echter krachtige vlammen uit, die de atmosfeer van nabijgelegen planeten weg kunnen blazen.
Links:
Harmonie tussen gemigreerde planeten houdt Trappist-1 stabiel, Fritschy, Yannick, New Scientist, 15 mei 2017
NASA Telescope Reveals Largest Batch of Earth-Size, Habitable-Zone Planets Around Single Star, jpl.NASA gov (22/02/2017).
Earth-sized planets: The newest, weirdest generation, exoplanets.NASA.gov
Promising Worlds Found Around Nearby Ultra-cool Dwarf Star
Drie potentieel leefbare werelden gevonden rond nabije ultrakoele dwergster, eso.org
TRAPPIST-1 in SIMBAD
TRAPPIST-1 / A cool runaway greenhouse without surface magma ocean – publication
The JWST Shows Us That TRAPPIST-1d Is Not As Earth-Like As We Hoped
(Exo)Planeet

TRAPPIST-1 / A cool runaway greenhouse without surface magma ocean - publication
2023-08-09
Exoplanets in the Trappist-1 system more likely to be habitable than scientists once thought, a study suggests.
A computer model simulating the evolution of planetary atmospheres found that water may have survived on some planets of the fascinating planetary system. For years, scientists have been debating the odds of life existing on seven fascinating planets orbiting the Trappist-1 star, the most famous planetary system outside our own. The reason? Although several of these planets orbit in their star’s habitable zone, the region around a stellar body where liquid water can exist because temperatures are just right, these worlds weren’t always so comfortable. In the past, Trappist-1 exoplanets were subject to much harsher conditions because their parent star used to be much hotter. During those hundreds of millions of scorching years, any water which may have been trapped in the rocks of these planets would have evaporated and dissipated into space, scientists previously thought. That would, of course, ruin the chance of the Trappist-1 planets to develop life as we know it. But a study, based on a novel modeling technique of the evolution of planetary atmospheres, suggests all may not be lost for life on Trappist-1 exoplanets.
Links:
TRAPPIST-1 / Temperate Earth-sized planets transiting a nearby ultracool dwarf star – publication
Exoplanets in the Trappist-1 system more likely to be habitable than scientists once thought, study suggests

WASP-107b / SO2, silicate clouds, but no CH4 detected in a warm Neptune - publication
2023-11-15
WASP-107b is a super-Neptune exoplanet that orbits the star WASP-107. It lies 200 light-years away from Earth in the constellation Virgo, its discovery was announced in 2017 by a team led by D. R. Anderson via the WASP-South.
WASP-107b could not have formed in its current orbit. It likely migrated inward from its birth orbit beyond 1 AU due to interaction with the heavier planet WASP-107c. WASP-107b is in a retrograde orbit, strongly misaligned with the equatorial plane of the parent star. The misalignment angle is equal to 118°+38 −19. WASP-107c follows a highly eccentric and inclined orbit with a period of 1088+15 −16 days. WASP-107b is a super-Neptune ice giant exoplanet located 200 light years away from Earth in the constellation Virgo. It is roughly the size of Jupiter but less than one-tenth of Jupiter’s mass, making it one of the lowest density exoplanets. Its radius is 0.96±0.03 times Jupiter’s, making its atmosphere fluffy, and coupled with transiting a moderately bright K-type star, makes it a target for atmospheric characterization. It is eight times nearer to its star than Mercury is to the Sun and orbits its star every 5.7 days. With a temperature of 773K / 500 °C, its atmosphere makes it one of the hottest known exoplanets. Helium was discovered in the planet’s atmosphere in 2018, making it the first time helium was discovered on an exoplanet. A follow-up observation with Keck in 2020 showed that the helium absorption extends beyond transit-egress. Extreme ultraviolet radiation from the host star is gradually whittling down the planet’s atmosphere, forming a comet-like tail 7 times as long as the radius of the planet.
A transmission spectrum of the warm Neptune exoplanet WASP-107b, captured by the Low Resolution Spectrometer (LRS) of the Mid InfraRed Instrument (MIRI) on board JWST, reveals evidence for water vapor, sulfur dioxide, and silicate (sand) clouds in the planet’s atmosphere. Credit: Michiel Min / European MIRI EXO GTO team / ESA / NASA
While the James Webb Space Telescope (JWST or Webb) may spend a lot of its time observing the farthest reaches of the early universe when galaxies were only just starting to form, it also spends plenty of its time focused on objects a lot closer to home — such as the atmospheres of exoplanets in our galactic neighborhood. A team of European astronomers, co-led by researchers from the KU Leuven Institute of Astronomy, used observations from the JWST to detail the atmospheric composition of the exoplanet WASP-107b. The researchers found water vapor, sulfur dioxide and even silicate sand clouds residing within the exoplanet’s dynamic atmosphere. The study ‘SO2, silicate clouds, but no CH4 detected in a warm Neptune‘ may also have implications for our understanding of the chemistry of distant planets.

Links:
James Webb Space Telescope reveals sandy surprise in distant planet
Op ‘suikerspinplaneet’ WASP-107b blijkt het ook te regenen, alleen valt daarbij geen water, maar zand uit de lucht
Wetenschappers van KU Leuven ontdekken zandwolken op exoplaneet WASP-107b: “Wetenschappelijke mijlpaal”
Alien Atmosphere: Webb Detects Water Vapor, Sulfur Dioxide and Sand Clouds in Nearby Exoplanet

GJ 9827d / NASA’s Hubble Finds Water Vapor in Small Exoplanet’s Atmosphere - publication
2024-01-25
Astronomers using NASA’s Hubble Space Telescope observed the smallest exoplanet where water vapor has been detected in the atmosphere.
At only approximately twice Earth’s diameter, the planet GJ 9827d could be an example of potential planets with water-rich atmospheres elsewhere in our galaxy. However, it remains too early to tell whether Hubble spectroscopically measured a small amount of water vapor in a puffy hydrogen-rich atmosphere, or if the planet’s atmosphere is mostly made of water, left behind after a primeval hydrogen/helium atmosphere evaporated under stellar radiation. If the planet has a residual water-rich atmosphere, then it must have formed farther away from its host star, where the temperature is cold and water is available in the form of ice, than its present location. In this scenario, the planet would have then migrated closer to the star and received more radiation. The hydrogen was heated and escaped, or is still in the process of escaping the planet’s weak gravity. The alternative theory is that the planet formed close to the hot star, with a trace of water in its atmosphere. The Hubble program observed the planet during 11 transits – events in which the planet crossed in front of its star – that were spaced out over three years. During transits, starlight is filtered through the planet’s atmosphere and has the spectral fingerprint of water molecules. If there are clouds on the planet, they are low enough in the atmosphere so that they don’t completely hide Hubble’s view of the atmosphere, and Hubble is able to probe water vapor above the clouds. GJ 9827d was discovered by NASA’s Kepler Space Telescope in 2017. It completes an orbit around a red dwarf star every 6.2 days. The star, GJ 9827, lies 97 light-years from Earth in the constellation Pisces.
Links:
NASA’s Hubble Finds Water Vapor in Small Exoplanet’s Atmosphere
Hubble has found water on a small rocky planet beyond our Solar System
Nu voor het eerst ook waterdamp gevonden in de atmosfeer van een kleine planeet

Transmission Spectroscopy of the Habitable Zone Exoplanet LHS 1140 b with JWST/NIRISS - publication
2024-06-21
Located 50 light-years from Earth, the beady-eyed exoplanet LHS 1140 b could be a perfect candidate for discovering liquid water outside the solar system, research ‘Transmission Spectroscopy of the Habitable Zone Exoplanet LHS 1140 b with JWST/NIRISS‘ suggests.
Links:
Habitable Zone Exoplanet LHS 1140b is Probably Snowball or Water World
‘Eyeball’ planet spied by James Webb telescope might be habitable

JWST-TST High Contrast: Living on the Wedge, or, NIRCam Bar Coronagraphy Reveals CO2 in the HR 8799 and 51 Eri Exoplanets' Atmospheres - publication
2025-03-17
Astronomers have announced that the James Webb Space Telescope (JWST) has successfully captured its first direct images of carbon dioxide gas on a planet beyond the solar system, the findings are both a testament to the telescope’s power in direct imaging and provide valuable insights into how planets form, both within our solar system and across the universe.
The latest JWST observations focused on the HR 8799 system, which consists of four planets orbiting their host star about 130 light-years from Earth in the constellation Pegasus. Previous observations have shown four of them are more massive than Jupiter, and are in orbits with periods that range from decades to centuries. This system has long intrigued astronomers studying planet formation, largely because of its youth — at just 30 million years old, these planets still radiate leftover heat from their births, which JWST was able to observe in wavelengths that tease out the specific gases and other atmospheric details.
Links:
James Webb Space Telescope sees four giant alien planets circling nearby star

Strongest hints yet of biological activity outside the solar system / New Constraints on DMS and DMDS in the Atmosphere of K2-18 b from JWST MIRI - publication
2025-04-17
Astronomers have detected the most promising signs yet of a possible biosignature outside the solar system, although they remain cautious.
Using data from the James Webb Space Telescope (JWST), the astronomers, led by the University of Cambridge, have detected the chemical fingerprints of dimethyl sulfide (DMS) and/or dimethyl disulfide (DMDS), in the atmosphere of the exoplanet K2-18b, which orbits its star in the habitable zone. On Earth, DMS and DMDS are only produced by life, primarily microbial life such as marine phytoplankton. While an unknown chemical process may be the source of these molecules in K2-18b’s atmosphere, the results are the strongest evidence yet that life may exist on a planet outside our solar system. The observations have reached the ‘three-sigma’ level of statistical significance – meaning there is a 0.3% probability that they occurred by chance. To reach the accepted classification for scientific discovery, the observations would have to cross the five-sigma threshold, meaning there would be below a 0.00006% probability they occurred by chance. The researchers say between 16 and 24 hours of follow-up observation time with JWST may help them reach the all-important five-sigma significance. Their results are reported in The Astrophysical Journal Letters. Earlier observations of K2-18b — which is 8.6 times as massive and 2.6 times as large as Earth, and lies 124 light years away in the constellation of Leo — identified methane and carbon dioxide in its atmosphere. This was the first time that carbon-based molecules were discovered in the atmosphere of an exoplanet in the habitable zone.
Those results were consistent with predictions for a ‘Hycean’ planet: a habitable ocean-covered world underneath a hydrogen-rich atmosphere. However, another, weaker signal hinted at the possibility of something else happening on K2-18b. To determine the chemical composition of the atmospheres of faraway planets, astronomers analyse the light from its parent star as the planet transits, or passes in front of the star as seen from the Earth. As K2-18b transits, JWST can detect a drop in stellar brightness, and a tiny fraction of starlight passes through the planet’s atmosphere before reaching Earth. The absorption of some of the starlight in the planet’s atmosphere leaves imprints in the stellar spectrum that astronomers can piece together to determine the constituent gases of the exoplanet’s atmosphere. The earlier, tentative, inference of DMS was made using JWST’s NIRISS (Near-Infrared Imager and Slitless Spectrograph) and NIRSpec (Near-Infrared Spectrograph) instruments, which together cover the near-infrared (0.8-5 micron) range of wavelengths. The new, independent observation used JWST’s MIRI (Mid-Infrared Instrument) in the mid-infrared (6-12 micron) range. DMS and DMDS are molecules from the same chemical family, and both are predicted to be biosignatures.
Both molecules have overlapping spectral features in the observed wavelength range, although further observations will help differentiate between the two molecules. However, the concentrations of DMS and DMDS in K2-18b’s atmosphere are very different than on Earth, where they are generally below one part per billion by volume. On K2-18b, they are estimated to be thousands of times stronger – over ten parts per million. Madhusudhan says that while the results are exciting, it’s vital to obtain more data before claiming that life has been found on another world. He says that while he is cautiously optimistic, there could be previously unknown chemical processes at work on K2-18b that may account for the observations. Working with colleagues, he is hoping to conduct further theoretical and experimental work to determine whether DMS and DMDS can be produced non-biologically at the level currently inferred. While he is not yet claiming a definitive discovery, Madhusudhan says that with powerful tools like JWST and future planned telescopes, humanity is taking new steps toward answering that most essential of questions: are we alone? The James Webb Space Telescope is a collaboration between NASA, ESA and the Canadian Space Agency (CSA). The research is supported by a UK Research and Innovation (UKRI) Frontier Research Grant.
Links:
Strongest hints yet of biological activity outside the solar system
Wetenschappers vinden ‘sterkste tekenen tot nu toe’ van mogelijk buitenaards leven
Er is geen Planet K2-18B! bescherm het buitenaardse leven!

VPRO #Tegenlicht – Zo ontrafelt deze wetenschapper het geheim van exoplaneten (TV internet)
2025-09-07
Tegenlicht is een informatief televisieprogramma van de VPRO via het internet.
Door de VPRO wordt het programma bestempeld als documentaire op het vlak van politiek, economie, sociologie en wetenschap. Het programma stelt zich ten doel inzicht in de werking van de samenleving te verschaffen.
In deze aflevering zoeken we mee met sterrenkundige Casper Farret Jentink, die diep in de bossen boven Genève werkt aan een van de grootste vragen die de mensheid zich ooit stelde: zijn we alleen in het universum? We worden alleen geboren, we sterven alleen, en daartussenin proberen we te begrijpen wat het betekent om er überhaupt te zijn. In een werkplaats, half sterrenwacht, half sciencefiction-decor, bouwt sterrenkundige Casper Farret Jentink met Zwitserse precisie instrumenten die het licht van verre sterren tot op vijf siliciumatomen nauwkeurig kunnen meten, op zoek naar een tweede aarde. Exoplaneten, planeten die draaien om een andere ster dan de zon, zijn onzichtbaar voor het oog, maar traceerbaar via de dure speeltjes van onder andere Jentink. Er werden er al duizenden gevonden, maar geen enkele zoals onze eigen aarde. Jentink is vastbesloten daar verandering in te brengen, via zelfgebouwde instrumenten met namen als Ristretto en Espresso. Want als we leven vinden, of juist niet, zegt dat iets over onszelf. Zijn we een uniek en kwetsbaar kosmisch toeval? Of zijn we een van de velen, omdat het leven ondanks alle uitdagingen taai en volhardend is. En dat, zegt Jentink, zou nog het geruststellendste antwoord zijn dat de wetenschap ons ooit heeft gegeven.
Links:
Hoe je met zelfgebouwde machines het geheim van exoplaneten kunt ontrafelen

The Eschatian Hypothesis - publication
2025-12-10
The research article titled “The Eschatian Hypothesis” explains that the first detection of an astrophysical object is usually not representative of the overall type.
Instead, we first tend to detect things with large observational signatures, due to our detection methods and their biases. The history of astronomy is full of examples. The history of exoplanet detection illustrates the phenomenon. The very first exoplanets were found in the early 1990s orbiting pulsars. But now we know that those were not representative. In the NASA Exoplanet Archive of more than 6,000 exoplanets, fewer than 10 were found around pulsars. They were detected because pulsars are like exquisitely timed cosmic lighthouses, and orbiting exoplanets altered that exquisite timing noticeably. It had nothing to do with how plentiful these types of planets are. For decades, science fiction writers have tried their best to prepare us for eventual contact with aliens. Their efforts are dominated by several recurrent tropes. There’s the invasion by a warlike species, there’s the highly evolved species trying to communicate with our primitive species, there’s the benevolent aliens come to save us from ourselves, and there’s the mischievous anal-probers and medical experimenters. But those examples are highly unlikely to represent first contact, according to new thinking and research. Not just because they may be totally unrealistic, but because of what might motivate another species to contact us, and how that alters the observational signal they use to announce their presence.

Links:
First Contact With an Alien Civilization Could Be ‘Loud’. Here’s Why

Babelsberger Sternennächte – Exoplaneten-Atmosphären - Von regnenden Rubinen bis zur Suche nach Leben | Dr. Fabio Lesjak (TV webcast)
2026-04-16 20:00 - 21:00
Die Leibniz-Instituts für Astrophysik Potsdam (AIP) Babelsberger Sternennächte finden online statt, in der Regel gibt es immer am 3. Donnerstag im Monat einen neuen Vortrag einer Wissenschaftlerin oder eines Wissenschaftlers des AIP, der ab 20 Uhr auf dem YouTube-Kanal von Urknall, Weltall und das Leben ausgestrahlt wird.
Dr. Fabio Lesjak, Wissenschaftler in der Forschungsgruppe Sternphysik und Exoplaneten am AIP, spricht zu „Exoplaneten-Atmosphären – Von regnenden Rubinen bis zur Suche nach Leben“. Ähnlich wie die Planeten in unserem Sonnensystem sind viele Exoplaneten von Atmosphären umgeben. Durch die Untersuchung dieser Atmosphären mit Hilfe hochauflösender Spektroskopie können Forschende Rückschlüsse auf die Zusammensetzung der Atmosphäre, ihre Temperatur und sogar über vorherrschende Winde ziehen.

Links:
Babelsberger Sternennächte
Babelsberger Sternennächte – playlist
