Sensitivity to habitable planets in the Roman microlensing survey

We study the Roman sensitivity to exoplanets in the Habitable Zone (HZ). The Roman efficiency for detecting habitable planets is maximized for three classes of planetary microlensing events with close caustic topologies. (a) The events with the lens distances of Dl ≳ 7 kpc, the host lens masses of Mh ≳ 0.6 M⊙. By assuming Jupiter-mass planets in the HZs, these events have q ≲ 0.001 and d ≳ 0.17 (q is their mass ratio and d is the projected planet-host distance on the sky plane normalized to the Einstein radius). The events with primary lenses, Mh ≲ 0.1 M⊙, while their lens systems are either (b) close to the observer with Dl ≲ 1 kpc or (c) close to the Galactic bulge, Dl ≳ 7 kpc. For Jupiter-mass planets in the HZs of the primary lenses, the events in these two classes have q ≳ 0.01, d ≲ 0.04. The events in the class (a) make larger caustics. By simulating planetary microlensing events detectable by Roman, we conclude that the Roman efficiencies for detecting Earth- and Jupiter-mass planets in the Optimistic HZs (OHZs, which is the region between [0.5, 2] AU around a Sun-like star) are $0.01{{\ \rm per\ cent}}$ and $5{{\ \rm per\ cent}}$, respectively. If we assume that one exoplanet orbits each microlens in microlensing events detectable by Roman ( i.e. ∼27000 ), this telescope has the potential to detects 35 exoplanets with the projected planet-host distances in the OHZs with only one having a mass ≲ 10M⊕. According to the simulation, 27 of these exoplanets are actually in the OHZs.

On Being Late: Cruising Mauna Kea and Unsettling Technoscientific Conquest in Hawai‘i

Conquest of new frontiers in the universe requires the colonization of old ones. This article interrogates technoscience desires to explore outer space, and how time and territory for discovering extraterrestrials and habitable planets are organized through settler colonialism on our own. Examining modern astronomy at Mauna Kea, I argue the technoscientific promise of the Thirty Meter Telescope hinges on a temporality of lateness—late to show up and late in time—that contributes to the dehumanization, elimination, and dispossession of Kanaka Maoli, the Indigenous people of Hawai‘i. I demonstrate further that kia‘i—mountain protectors—unsettle technoscientific conquest by cruising Mauna Kea as an alternative tempo that disrupts the pace of building the observatory.

Origin of Life

Our knowledge of our solar system has passed the point of no return. Increasingly, it seems possible that scientists will soon discover how life is created on habitable planets like Earth and Mars. Scientists have responded to a renewed public interest in the origin of life with research, but many questions still remain unanswered in the broader conversation. Other questions can be answered by the laws of chemistry and physics, but questions surrounding the origin of life are best answered by reasonable extrapolations of what scientists know from observing the Earth and its solar system. Origin of Life: What Everyone Needs to Know® is a comprehensive scientific guide on the origin of life. David W. Deamer sets out to answer the top forty questions about the origin of life, including: Where do the atoms of life come from? How old is Earth? What was the Earth like before life originated? Where does water come from? How did evolution begin? After he provides the informational answer for each question, there is a follow-up: How do we know? This question expands the horizon of the whole book, and provides scientific reasoning and explanations for hypotheses surrounding the origin of life. How scientists come to their conclusions and why we can trust these answers is an important question, and Deamer provides answers to each big question surrounding the origin of life, from what it is to why we should be curious.

Origin of Life

Our knowledge of our solar system has passed the point of no return. Increasingly, it seems possible that scientists will soon discover how life is created on habitable planets like Earth and Mars. Scientists have responded to a renewed public interest in the origin of life with research, but many questions still remain unanswered in the broader conversation. Other questions can be answered by the laws of chemistry and physics, but questions surrounding the origin of life are best answered by reasonable extrapolations of what scientists know from observing the Earth and its solar system. Origin of Life: What Everyone Needs to Know® is a comprehensive scientific guide on the origin of life. David W. Deamer sets out to answer the top forty questions about the origin of life, including: Where do the atoms of life come from? How old is Earth? What was the Earth like before life originated? Where does water come from? How did evolution begin? After he provides the informational answer for each question, there is a follow-up: How do we know? This question expands the horizon of the whole book, and provides scientific reasoning and explanations for hypotheses surrounding the origin of life. How scientists come to their conclusions and why we can trust these answers is an important question, and Deamer provides answers to each big question surrounding the origin of life, from what it is to why we should be curious.

The most common habitable planets – II. Salty oceans in low-mass habitable planets and global climate evolution

ABSTRACT Global climate evolution models for habitable Earth-like planets do not consider the effect of ocean salinity on land ice formation through the hydrological cycle. We consider two categories of such planets: planets with deep oceans, but intrinsically high salinities due to the weaker salt removal process by hydrothermal vents; and planets with shallow oceans, where the increase in salt content and decrease in ocean area during the onset of glaciation cause a negative feedback, helping delay the spread of land ice. We developed a toy climate model of a habitable planet on the verge of an ice age, using a range of initial salt concentrations. Planets with deep oceans and high salinity show considerable increase in the time necessary to fill arctic land with ice sheets, up to 23 per cent considering the maximum salinity range. For planets with shallow oceans, the effect of intrinsic high salinity is reinforced by the negative feedback, counteracting positive feedbacks like the ice–albedo and Croll–Milankovitch perturbations, to the point of effectively terminating land ice sheet growth rate during the simulated time-scale. We also apply this model to the putative ocean of early Mars, finding intermediate results: salinity probably did not play a role in the evolution of Mars´ climate, considering the time-scale of its ice ages. We conclude that this phenomenon is essentially an abiotic self-regulation mechanism against ice ages and should be regarded in the context of habitable planets smaller and drier than the Earth, which may well represent the bulk of habitable planets.

The habitability of large elliptical galaxies

ABSTRACT Based on numbers of stars, supernova rates, and metallicity, a prior study concluded that large elliptical galaxies contain up to 10 000 times more habitable planets than the Milky Way and are thus the ‘cradles of life’. Using the results of their model and taking into account galactic number distributions and supernova rates, I argue here that this result constitutes a violation of the principle of mediocrity as applied to the reference class of all extant technological species. Assuming that we are a typical technological species in the attribute of inhabiting a relatively large disc-dominated galaxy, I outline two hypotheses that could significantly limit the habitability of large elliptical galaxies: (1) massive galactic sterilization events associated with quasar/active galactic nucleus activity and starburst supernovae that occurred when the antecedents of today’s large elliptical galaxies were much more compact; and (2) the probability of habitable planet formation in large elliptical galaxies may be small since a disproportionately larger number of gaseous planets are expected to form as a result of the generally higher metallicity in large elliptical galaxies. Consequently, fewer habitable planets will accrete if the gaseous planets' inward migrations are sufficiently slow. The sterilization events of hypothesis (1) occurred at earlier epochs ($z$ ≥ 1) and so they must be effectively permanent, implying two possible scenarios regarding the origin and evolution of life. In connection with one of these scenarios, independent applications of the principle of mediocrity suggest that M-dwarf stars are not significant hosts of technological life.