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#exoplanet

10 posts8 participants0 posts today
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Mikko Tuomi

Much smaller than gas-giants and typically cooler than hot Jupiters, sub-Neptunes were extremely challenging to observe before the launch of #JWST.

Though they appear to be the most common type of #exoplanet in our galaxy, you won’t find them in our solar system.

Astronomers are trying to understand how these planets formed and evolved, why they are so common, and why they don’t orbit our Sun.

#astronomers #exoplanets
webbtelescope.org/contents/new

Public
Daniel Fischer

Thermal Emission and Confirmation of the Frigid White Dwarf #Exoplanet WD 1856+534b: arxiv.org/abs/2504.16982 -> Exoplanet discovered in 2020 has the coldest temperatures ever measured, scientists say: abcnews.go.com/Technology/exop

arXiv.orgThermal Emission and Confirmation of the Frigid White Dwarf Exoplanet WD 1856+534bWe report the detection of thermal emission from and confirm the planetary nature of WD 1856+534b, the first transiting planet known to orbit a white dwarf star. Observations with JWST's Mid-Infrared Instrument (MIRI) reveal excess mid-infrared emission from the white dwarf, consistent with a closely-orbiting Jupiter-sized planet with a temperature of $186^{+6}_{-7}$ K. We attribute this excess flux to the known giant planet in the system, making it the coldest exoplanet from which light has ever been directly observed. These measurements constrain the planet's mass to no more than six times that of Jupiter, confirming its planetary nature and ruling out previously unexcluded low-mass brown dwarf scenarios. WD 1856+534b is now the first intact exoplanet confirmed within a white dwarf's "forbidden zone", a region where planets would have been engulfed during the star's red giant phase. Its presence provides direct evidence that planetary migration into close orbits, including the habitable zone, around white dwarfs is possible. With an age nearly twice that of the Solar System and a temperature akin to our own gas giants, WD 1856+534b demonstrates JWST's unprecedented ability to detect and characterize cold, mature exoplanets, opening new possibilities for imaging and characterizing these worlds in the solar neighborhood.
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HistoPol (#HP) 🏴 🇺🇸 🏴

@mina @admin @evelynefoerster

... may be #Habitable (have conditions favorable to life). Whether our definitions of #Planet can be applied to these newly found objects remains to be seen."

science.nasa.gov/solar-system/planets/what-is-a-planet/#h-the-new-definition-of-planet

s/: Ich mein', #ExoPLANET, wie schwierig kann da eine Klassifikation schon sein? /s 🤦‍♀️🤦‍♂️🤦

Im Übrigen muss ein #Planet auch nicht bewohnbar sein! --sonst hätte das #Solarsystem nur einen einzigen. Und überhaupt:...

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Six Grandfathers Mountain

@badibulgator @bigiain @scalzi
RE
#Mars is the third one which is (sometimes) easy to spot even from very light-polluted places

Sure, I see that slight red, pink small non-twinking Mars, sometimes. I know it takes 9 months to get there with current tech. That's a big event, like the time it takes to have a baby

I'm always amazed that some/many non scientific folks used to be on the fence in the past where #UFOs were a thing. ZERO chance to the nearest #exoplanet, about 300,000 yr travel time

Public
Daniel Fischer

"We show that numerous alternative models without potential biosignature gases provide equivalent or better fits to the observations" of #exoplanet K2-18 b by the JWST: "We demonstrate that the significance of a claimed detection relies on the choice of models being compared, and that model preference does not necessarily imply the presence of any specific gas." Says the new paper arxiv.org/abs/2504.21788 "The Challenges of Detecting Gases in Exoplanet Atmospheres" - d'oh ...

arXiv.orgThe Challenges of Detecting Gases in Exoplanet AtmospheresClaims of detections of gases in exoplanet atmospheres often rely on comparisons between models including and excluding specific chemical species. However, the space of molecular combinations available for model construction is vast and highly degenerate. Only a limited subset of these combinations is typically explored for any given detection. As a result, apparent detections of trace gases risk being artifacts of incomplete modeling rather than robust identification of atmospheric constituents, especially in the low signal-to-noise regime. We illustrate these challenges using the sub-Neptune K2-18~b, where recent claims of a potential biosignature detection vanish when the considered model space is expanded. We show that numerous alternative models without potential biosignature gases provide equivalent or better fits to the observations. We demonstrate that the significance of a claimed detection relies on the choice of models being compared, and that model preference does not necessarily imply the presence of any specific gas.
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