Astronomy and Planetary Science Thread

Flyaway

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WASP-127b: A misaligned planet with a partly cloudy atmosphere and tenuous sodium signature seen by ESPRESSO

The study of exoplanet atmospheres is essential to understand the formation, evolution and composition of exoplanets. The transmission spectroscopy technique is playing a significant role in this domain. In particular, the combination of state-of-the-art spectrographs at low- and high-spectral resolution is key to our understanding of atmospheric structure and composition. Two transits of the close-in sub Saturn-mass planet,WASP-127b, have been observed with ESPRESSO in the frame of the Guaranteed Time Observations Consortium. Transit observations allow us to study simultaneously the system architecture and the exoplanet atmosphere. We found that this planet is orbiting its slowly rotating host star (veq sin(i)=0.53+/-0.07 km/s) on a retrograde misaligned orbit (lambda=-128.41+/-5.60 deg). We detected the sodium line core at the 9-sigma confidence level with an excess absorption of 0.3+/-0.04%, a blueshift of 2.7+/-0.79 km/s and a FWHM of 15.18+/-1.75 km/s. However, we did not detect the presence of other atomic species but set upper-limits of only few scale heights. Finally, we put a 3-sigma upper limit, to the average depth of the 1600 strongest water lines at equilibrium temperature in the visible band, of 38 ppm. This constrains the cloud-deck pressure between 0.3 and 0.5 mbar by combining our data with low-resolution data in the near-infrared and models computed for this planet. To conclude, WASP-127b, with an age of about 10 Gyr, is an unexpected exoplanet by its orbital architecture but also by the small extension of its sodium atmosphere (~7 scale heights). ESPRESSO allows us to take a step forward in the detection of weak signals, thus bringing strong constraints on the presence of clouds in exoplanet atmospheres. The framework proposed in this work can be applied to search for molecular species and study cloud-decks in other exoplanets.

 

Rhinocrates

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Better than a lava lamp.


(Paywalled)

Preprint here:


This is about hot Jupiters, but it's interesting because if there's an atmosphere, the climate models of tidally-locked planets being 'too hot on the day side, too cold on the night side, thin habitable ring in the twilight zone' are way too simplistic, so there might be some application to studies of hypothetical 'mearths' - earthlike planets around red dwarfs. Models I have seen for mearths generally show complementary polar vortices feeding a stream that whips around to the nightside, delivering warm air and possibly moisture there.
 

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Flyaway

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Study Finds Photosynthesis in Venus’ Clouds Could Support Life

New data analysis has found that the sunlight filtering through Venus’ clouds could support Earth-like photosynthesis in the cloud layers and that chemical conditions are potentially amenable to the growth of microorganisms.


Potential for Phototrophy in Venus' Clouds

Abstract

We show that solar irradiances calculated across Venus' clouds support the potential for Earth-like phototrophy and that treatment of Venus' aerosols containing neutralized sulfuric acid favor a habitable zone. The phototrophic potential of Venus' atmosphere was assessed by calculating irradiances (200–2000 nm, 15° solar zenith angle, local noon) using a radiative transfer model that accounted for absorption and scattering by the major and minor atmospheric constituents. Comparisons to Earth's surface (46 W m−2, 280–400 nm) suggest that Venus' middle and lower clouds receive ∼87% less normalized UV flux (6–7 W m−2) across 200–400 nm, yet similar normalized photon flux densities (∼4400–6200 μmol m−2 s−1) across 350–1200 nm. Further, Venus' signature phototrophic windows and subwindows overlap with the absorption profiles of several photosynthetic pigments, especially bacteriochlorophyll b from intact cells and phycocyanin. Therefore, Venus' light, with limited UV flux in the middle and lower clouds, is likely quite favorable for phototrophy. We additionally present interpretations to refractive index and radio occultation measures for Venus' aerosols that suggest the presence of lower sulfuric abundances and/or neutralized forms of sulfuric acid, such as ammonium bisulfate. Under these considerations, the aerosols in Venus' middle clouds could harbor water activities (≥0.6) and buffered acidities (Hammett acidity factor, H0 -0.1 to -1.5) that lie within the limits of acidic cultivation (≥H0 -0.4) and are tantalizingly close to the limits of oxygenic photosynthesis (≥H0 0.1). Together, these photophysical and chemical considerations support a potential for phototrophy in Venus' clouds.

 

Flyaway

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GW Ori: circumtriple rings and planets

ABSTRACT
GW Ori is a hierarchical triple star system with a misaligned circumtriple protoplanetary disc. Recent Atacama Large Millimeter/submillimeter Array observations have identified three dust rings with a prominent gap at 100au
and misalignments between each of the rings. A break in the gas disc may be driven by the torque from either the triple star system or a planet that is massive enough to carve a gap in the disc. Once the disc is broken, the rings nodally precess on different time-scales and become misaligned. We investigate the origins of the dust rings by means of N-body integrations and 3D hydrodynamic simulations. We find that for observationally motivated parameters of protoplanetary discs, the disc does not break due to the torque from the star system. We suggest that the presence of a massive planet (or planets) in the disc separates the inner and outer discs. We conclude that the disc breaking in GW Ori is likely caused by undetected planets – the first planet(s) in a circumtriple orbit.

 

Flyaway

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View: https://twitter.com/SpcPlcyOnline/status/1442908742635298818


Hertz [NASA astrophysics division director Paul Hertz] says everyone is "eagerly" awaiting the astrophysics Decadal Survey, but NASA had to move on w/o it. Had to formulate FY2023 budget req already, so it obviously doesn't contain $ for anything it. Hope it's out in time to guide next call for tech proposals in mid-Dec.

Q-if Decadal recommends new flagship can it launch in 2030s?
Hertz-priority is launching the 2 flagships we already have, JWST and Roman, & demonstrate to stakeholders we can do these missions. Then will decide right time to start a new one. Don't know what'll be recommended.
 

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Flyaway

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Energy burst from most distant known galaxy might have been a satellite orbiting Earth

Gamma rays are one of the most energetic forms of light, and gamma ray bursts release almost unimaginable quantities of them. First discovered during the cold war – by military satellites searching for the signs of nuclear tests in the upper atmosphere – gamma ray bursts are now thought to be caused by massive stars undergoing huge explosions when they run out of fuel. These events are rare, but so energetic they can be seen in galaxies many billions of light years away.

Recently, astronomers thought they had seen evidence for one of these explosions from the most distant galaxy every seen. But a recently published paper casts doubt on these claims, suggesting it might have been caused by a more mundane source much closer to home.

Around the time that the original team were studying the sky, a Russian proton rocket reached low Earth orbit and released its upper stages (dubbed Breeze-M), which then became space junk, orbiting the Earth. By looking at the orbit of the space debris and matching with the observations taken in the original study, the new team found the flash could be simply explained by the upper stage falling past the part of the sky the telescope was observing.


Related paper:

GN-z11-flash from a man-made satellite not a gamma-ray burst at redshift 11

 

Flyaway

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Astronomers discover 'extraordinary' unknown radio signal from heart of Milky Way

Across the vast desert plains of Western Australia, on the lands of the Wajarri Yamatji people, lies one of the most capable radio telescope arrays in the world. Containing 36 dish antennas, the Australian Square Kilometre Array Pathfinder, ASKAP, is an eye to the universe. The three dozen antennas watch for radio waves that crash over the Earth.

Over the last two years the antennas have, on occasion, been pointed toward the heart of the Milky Way, our home galaxy. And, on occasion, they've detected a highly unusual radio signal -- one that does not seem to fit with any object we currently know is lurking in the cosmos.

The detection of the signal appears in the Astrophysical Journal on Oct. 12. It was first published as a preprint on arXiv in September.

The name of the strange signal is a mouthful: ASKAP J173608.2-321635. We're going to call it the Ghost. Between April 2019 and August 2020, the Ghost was spotted 13 times but without any consistent timing.


Here’s the related paper:

 

Flyaway

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The population of M dwarfs observed at low radio frequencies

Abstract
Coherent low-frequency (≲200 MHz) radio emission from stars encodes the conditions of the outer corona, mass-ejection events and space weather1,2,3,4,5. Previous low-frequency searches for radio-emitting stellar systems have lacked the sensitivity to detect the general population, instead largely focusing on targeted studies of anomalously active stars5,6,7,8,9. Here we present 19 detections of coherent radio emission associated with known M dwarfs from a blind flux-limited low-frequency survey. Our detections show that coherent radio emission is ubiquitous across the M dwarf main sequence, and that the radio luminosity is independent of known coronal and chromospheric activity indicators. While plasma emission can generate the low-frequency emission from the most chromospherically active stars of our sample1,10, the origin of the radio emission from the most quiescent sources is yet to be ascertained. Large-scale analogues of the magnetospheric processes seen in gas giant planets3,11,12 probably drive the radio emission associated with these quiescent stars. The slowest-rotating stars of this sample are candidate systems to search for star–planet interaction signatures.


Source: https://www.popsci.com/space/radio-signals-exoplanets/
 

Flyaway

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Probably stretching the terms of this thread but I thought this was interesting.

In A.D. 993, a storm on the sun released an enormous pulse of radiation that was absorbed and stored by trees all over the Earth. Now, that solar event has proved a critical tool in pinpointing an exact year the Vikings were present in the Americas.
There was one more thing that stood out: Three of the wood samples were from trees alive during the solar event of 993, when the cosmic storm released a pulse of radiation so powerful that it was recorded in the rings of the world’s trees. Referred to by researchers as a “cosmogenic radiocarbon event,” the phenomenon has only happened twice in the last 2,000 years.
 
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Flyaway

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A Stable H2O Atmosphere on Europa’s Trailing Hemisphere From HST Images

Abstract​

Previous studies of the global intensities of the oxygen emissions at 1,356 Å and 1,304 Å revealed molecular oxygen (O2) in Europa's atmosphere. Here we investigate the relative changes of the two oxygen emissions when Europa emerges from eclipse as well as the radial profiles of the relative emissions across the sunlit disk in Hubble Space Telescope observations taken in 1999, 2012, 2014, and 2015 while the moon was at various orbital positions. The eclipse observation constrains the atomic oxygen (O) column density to
urn:x-wiley:00948276:media:grl63016:grl63016-math-0001
urn:x-wiley:00948276:media:grl63016:grl63016-math-0002
or lower. We then find that the OI1356-Å/OI1304-Å ratio systematically decreases towards the disk center on the trailing hemisphere. The observed emission ratio pattern and the persistence of it from 1999 to 2015 imply a stable H2O abundance in the central sunlit trailing hemisphere with an H2O/O2 ratio of 12–22. On the leading hemisphere, the emissions are consistent with a pure O2 atmosphere everywhere across the moon disk.

Plain Language Summary​

Observations by the Hubble Space Telescope in far-ultraviolet light of Jupiter's icy moons were used in the past to detect their oxygen atmospheres. Results of a new analysis of images and spectra of the moon Ganymede have recently shown that the same observations also contain information that water vapor is abundant in the atmosphere in addition to oxygen. We use the same analysis here for Europa and find a water vapor atmosphere as well, but only above the orbital trailing hemisphere of the moon.

 

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