A planetary dynamo may be a key factor in creating the conditions needed for life. And creating that dynamo seems to depend on the radioactive decay of thorium and uranium, generating internal heating and driving plate tectonics. Let's carry this line of thought further, though, as the authors of a new paper out of UC-Santa Cruz do, and point out that these heavy elements are necessary to create a magnetic field like Earth's, which protects us from damaging radiation. In the rocky planets, magnetic fields are generated by convection in a metallic core, which in turn is driven by heat extracted into the mantle (Nimmo 2015; Labrosse 2015; Boujibar et al. 2020). Since mantle radiogenic heat production controls how much heat is extracted from the core, it will also influence the presence or absence of a dynamo. Similarly, heat production will control the mantle temperature and thus the rate of silicate melting and volcanism. That quote is from the paper, whose lead author is Francis...

The naming of names is quite a project when it comes to new astronomical objects, and given the sheer numbers -- 300 million habitable planets around G- and K-class stars, for example -- we might do better to stick with simple identifiers. On the other hand, it's a bit charming that a new brown dwarf known by its identifier as BDR J1750+3809 has been dubbed 'Elegast' by the discovery team. This is the first substellar object found through radio observations. The name is both appropriate and specific to the discovery space. Elegast appears in a poem in Middle Dutch (12th or 13th Century) called 'Karel ende Elegast,' with the character Elegast being a vassal of Charlemagne who seems to be king of the elves (Wikipedia to the rescue, vindicating once again my decision to send them a monthly donation). The Dutch connection is that the radio work comes out of LOFAR (Low-Frequency Array), which is currently the largest radio telescope operating at the lowest frequencies that we can observe...

We’ve talked about the Drake Equation a good deal over the years, but I may not have mentioned before that when Frank Drake introduced it in 1961, it was for the purpose of stimulating discussion at a meeting at the National Radio Astronomy Observatory in Green Bank, West Virginia that was convening to discuss the nascent field of SETI. This was in the era of Drake’s Project Ozma and the terms of the SETI debate were hardly codified. Moreover, as Nadia Drake recounts in this absorbing look back at her father’s work in that era, Drake had spent the time immediately before the meeting trying to line up Champagne for UC-Berkeley biochemist Melvin Calvin, who was about to win the Nobel Prize. So there was a certain ad hoc flavor to the equation, one that Drake assembled more or less on the fly to clarify the factors to be considered in looking for other civilizations. How Drake did all this while trying to locate a sufficient quantity of good Champagne in the rural West Virginia of 1961...

Yesterday’s paper from Matt Clement and team reminded us of the enormous transformation that can take place in a planetary system as it lurches toward eventual stability. Gas giants have so much to say about how this process occurs, with their gravitational interactions sometimes ejecting other worlds from the system. Ejected planets are often called ‘rogue’ planets because they wander the galaxy without orbiting a star. Their numbers may be vast. Clement and team think we may have ejected an ice giant from our early system, as we discussed yesterday. Whatever the case, I’ve been talking about rogue planets for about ten years, and as I look back, I run into intriguing finds like PSO J318.5-22, which is described in a 2013 paper from Michael Liu and colleagues (citation below). Says Liu (University of Hawaii): "We have never before seen an object free-floating in space that looks like this. It has all the characteristics of young planets found around other stars, but it is drifting...

Scientists have created the first global temperature map for a planet discovered by TESS, a ‘hot Neptune’ known as LTT 9779b. The first of two just released papers also notes that this is the first spectral atmospheric characterization of a TESS planet. That makes this unusual discovery (lead author Ian Crossfield calls it a “planet that shouldn’t exist”) a useful test case for future work, because the goal of finding the biosignatures of living worlds won’t be achieved without drilling down from inhospitable places like LTT 9779b. The atmospheres of hotter, larger and more readily characterizable planets let us hone our techniques and teach us how to proceed. Crossfield’s reference to the planet’s rarity draws on the fact that so few worlds like this occur close to their host stars, probably because their mass is low enough that the proximity to the star causes atmospheric evaporation. A larger gas giant like one of the ‘hot Jupiters’ we began finding in the beginning of the...

Taking advantage of the fact that most major bodies in our Solar System orbit in roughly the same plane around the Sun, Cornell's Lisa Kaltenegger, working with Joshua Pepper (Lehigh University), has gone on to ponder the implications of the ecliptic plane, traced out as the plane of Earth's orbit around the Sun, for exoplanet studies. We're in the realm of transit detection here, because what the authors want to know is not what we see on the ecliptic so much as what extraterrestrial observers would see if they were on the same plane. Says Kaltenegger: "Let's reverse the viewpoint to that of other stars and ask from which vantage point other observers could find Earth as a transiting planet. If observers were out there searching, they would be able to see signs of a biosphere in the atmosphere of our Pale Blue Dot, And we can even see some of the brightest of these stars in our night sky without binoculars or telescopes." Kaltenegger is director of Cornell's Carl Sagan Institute and...

The SAINT-EX telescope, operated by NCCR PlanetS, produces a nice resonance as I write this morning. The latter acronym stands for the National Centre of Competence in Research PlanetS, operated jointly by the University of Bern and the University of Geneva. The former, SAINT-EX, identifies a project called Search And characterIsatioN of Transiting EXoplanets, and the team involved explicitly states that they shaped their acronym to invoke Antoine de Saint-Exupéry, legendary aviator and author of, among others, Wind, Sand and Stars (1939), Night Flight (1931) and Flight to Arras (1942). I’ve talked about Saint-Exupéry now and again throughout the history of Centauri Dreams, not only because he was an inspiration for my own foray into flying, but also because for our interstellar purposes he is credited with this inspirational thought: “If you want to build a ship, don’t drum up the men to gather wood, divide the work and give orders. Instead, teach them to yearn for the vast and...

Gas giant planets in orbits similar to Jupiter's are a tough catch for exoplanet hunters. They're far enough from the star (5 AU in the case of Jupiter) that radial velocity methods are far less sensitive than they would be for star-hugging 'hot Jupiters.' A transit search can spot a Jupiter analogue, but the multi-year wait for the proper alignment is obviously problematic. Still, we'd like to know more, because the gravitational influence of Jupiter may have a crucial role in deflecting asteroids and comets from the inner system, thus protecting terrestrial worlds like ours. If this is the case, then we need to ask whether we just lucked out by having Jupiter where it is, or whether there is some mechanism that makes the presence of a gas giant in a kind of 'protective' outer orbit likely when rocky worlds inhabit the inner system. Enter the computer simulations run by Martin Schlecker at the Max Planck Institute for Astronomy (MPIA) in Heidelberg. Working with scientists at the...

I'm startled by the findings in a new paper from Dominique Segura-Cox (Max Planck Institute for Extraterrestrial Physics), who argues that based on the evidence of one infant system, we may have planet formation all wrong, at least in terms of when it occurs. The natural assumption is that the star appears first, the planets then accruing mass from within the circumstellar disk. But Segura-Cox and team have found a system in which planet and star seem to be forming all but simultaneously. IRS 63 is a protostar about 470 light years out that is less than half a million years old. Swathed in gas and dust, the star is still gathering mass, but evidence from the disk suggests that the planets have already begun to form. One reason for the surprise factor here is that we've looked at many young stellar systems and their disks, most of them at least one million years old, and the assumption has been that the stars were well along in their own formation process before the planets began to...

We could use a lot more information about flare activity on M-dwarf stars, which can impact planetary atmospheres and surfaces and thus potential habitability. Thus far much has been said on the subject, but what has been lacking are details about the kinds of flares in question. It’s a serious issue given that, in order to be in the liquid water habitable zone, an M-dwarf planet has to orbit in breathtaking proximity to the host star. Flares occur through a star’s magnetic field re-connection, which releases radiation across the electromagnetic spectrum. While flares can erode atmospheres and bathe the surface in UV flux, too few flares could actually be detrimental as well, providing as a new paper on the matter suggests, “insufficient surface radiation to power prebiotic chemistry due to the inherent faintness of M-dwarfs in the UV.” The paper is out of the University of North Carolina, measuring a large sample of superflares in search of a clearer picture of their effect. Flares...