Satellite imagery captured enormous pyrocumulonimbus clouds from the rapidly-growing Creek Fire in the Sierra National Forest.

We investigate the metal contents of Lyman-alpha clouds at 2.2

The observation of a 266.94 GHz feature in the Venus spectrum has been attributed to PH$_3$ in the Venus clouds, suggesting unexpected geological, chemical or even biological processes. Since both PH$_3$ and SO$_2$ are spectrally active near 266.94 GHz, the contribution to this line from SO$_2$ must be determined before it can be attributed, in whole or part, to PH$_3$. An undetected SO$_2$ reference line, interpreted as an unexpectedly low SO$_2$ abundance, suggested that the 266.94 GHz feature could be attributed primarily to PH$_3$. However, the low SO$_2$ and the inference that PH$_3$ was in the cloud deck posed an apparent contradiction. Here we use a radiative transfer model to analyze the PH$_3$ discovery, and explore the detectability of different vertical distributions of PH$_3$ and SO$_2$. We find that the 266.94 GHz line does not originate in the clouds, but above 80 km in the Venus mesosphere. This level of line formation is inconsistent with chemical modeling that assumes generation of PH$_3$ in the Venus clouds. Given the extremely short chemical lifetime of PH$_3$ in the Venus mesosphere, an implausibly high source flux would be needed to maintain the observed value of 20$pm$10 ppb. We find that typical Venus SO$_2$ vertical distributions and abundances fit the JCMT 266.94 GHz feature, and the resulting SO$_2$ reference line at 267.54 GHz would have remained undetectable in the ALMA data due to line dilution. We conclude that nominal mesospheric SO$_2$ is a more plausible explanation for the JCMT and ALMA data than PH$_3$.

All strong, 'dense core' sources and (2, 2)-line observations are mapped in the present results of a survey of about 100 visually opaque regions in nearby dark clouds in the 1.3-cm (J, K) = (1, 1) line of NH3. Line shapes are compared with cloud motion models, and source density, size, and temperature are compared with equilibrium and stability requirements. These are found to indicate that most dense cores are in the early stages of collapse, or in near-critical equilibrium. If the latter possibility is the case, support is probably furnished by a combination of thermal and subsonic turbulent motions. Positions of the 10 known dense cores in Taurus-Auriga are correlated with emission-line star group positions. The results obtained cumulatively suggest that most of the dense cores described will form low mass stars in the next one million years.

We present N-band photometry for a sample of 21 dust- enshrouded AGB stars in the Large Magellanic Cloud, and three additional sources in the Small Magellanic Cloud. Together with near-IR photometry, this is used to give a tentative classification into carbon and oxygen-rich atmospheres. Bolometric luminosities are also estimated for these stars. In addition, we present the results of a survey for OH masers in the LMC, which resulted in the discovery of OH maser emission from IRAS04407-7000. Spectra between 600 and 1000 nm have been obtained for two heavily obscured AGB stars in the LMC, confirming them to be highly reddened very late M-type giants. Because the dust-enshrouded stars are clearly undergoing heavy mass loss they are assumed to be very near the termination of their respective Asymptotic Giant Branch phases. The fraction of mass-losing carbon stars decreases with increasing luminosity, as expected from Hot Bottom Burning. The best candidate carbon star, with M_bol = -6.8 mag, is the most luminous mass-losing carbon star in the Magellanic Clouds, and amongst the most luminous AGB stars. At lower luminosities (M_bol = -5 mag) both oxygen and carbon stars are found. This may be explained by a range in metallicity of the individual mass-losing AGB stars.

Hazy clouds of smoke from dozens of wildfires darkened the sky to an eerie orange glow over much of the West Coast on Wednesday, keeping street lights illuminated during the day and putting residents on edge.

We use a sample of the 13 most luminous WMAP Galactic free-free sources, responsible for 33% of the free- free emission of the Milky Way, to investigate star formation. The sample contains 40 star forming complexes; we combine this sample with giant molecular cloud (GMC) catalogs in the literature, to identify the host GMCs of 32 of the complexes. We estimate the star formation efficiency epsilon_GMC and star formation rate per free-fall time epsilon_ff. We find that epsilon_GMC ranges from 0.002 to 0.2, with an ionizing luminosity-weighted average epsilon_GMC = 0.08, compared to the Galactic average = 0.005. Turning to the star formation rate per free-fall time, we find values that range up to epsilon_ff = 1. Weighting by ionizing luminosity, we find an average of epsilon_ff = 0.16 - 0.24 depending on the estimate of the age of the system. Once again, this is much larger than the Galaxy-wide average value epsilon_ff = 0.008. We show that the lifetimes of giant molecular clouds at the mean mass found in our sample is 17 plus or minus 4 Myr, about two free-fall times. The GMCs hosting the most luminous clusters are being disrupted by those clusters. Accordingly, we interpret the range in epsilon_ff as the result of a time-variable star formation rate; the rate of star formation increases with the age of the host molecular cloud, until the stars disrupt the cloud. These results are inconsistent with the notion that the star formation rate in Milky Way GMCs is determined by the properties of supersonic turbulence

Eggs. They’ve been over easy, scrambled, poached and boiled – you know, the usual. From sunny side up to frittatas, we’ve had this protein-packed breakfast star in every way possible – or have we? If you haven’t heard of “egg clouds” (also called “egg nests”), it’s an egg-citingly new and fun way to enjoy the first meal of the day.