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Atmospheric Evolution on Hot Super-Earths

by Paul Gilster | Sep 29, 2021 | Exoplanetary Science | 7 Comments

Hot Jupiters (notice I’ve finally stopped putting the term into quotation marks) were the obvious early planets to detect, even if no one had any idea whether such things existed. I suppose you could say Greg Matloff knew, at least to the point that he helped Buzz Aldrin and John Barnes come up with a plot scenario involving a planet that fit the description in their novel Encounter with Tiber (Grand Central, 1996), which was getting published just as the hot Jupiter 51 Pegasi b was being discovered. Otto Struve evidently predicted the existence of gas giants close to their star as far back as 1952, but it’s certainly true that planets like this weren’t in the mainstream of astronomical thinking when 51 Pegasi b popped up. Selection effect works wonders, and it makes sense that radial velocity methods would bear first fruit with a large planet working its gravitational effects on the star it orbits closely. Today, using transits, gravitational microlensing, astrometry and even direct...

Hit-and-Run: Earth, Venus and Planet-Shaping Impacts

by Paul Gilster | Sep 28, 2021 | Exoplanetary Science | 23 Comments

The gradual accretion of material within a protoplanetary disk should, in conventional models, allow us to go all the way from dust grains to planetesimals to planets. But a new way of examining the latter parts of this process has emerged at the University of Arizona Lunar and Planetary Laboratory in Tucson. There, in a research effort led by Erik Asphaug, a revised model of planetary accretion has been developed that looks at collisions between large objects and distinguishes between ‘hit-and-run’ events and accretionary mergers. The issue is germane not just for planet formation, but also for the appearance of our Moon, which the researchers treat in a separate paper to extend the model for early Earth and Venus interactions that appears in the first. In the Earth/Venus analysis, an impact might be a glancing blow that, given the gravitational well produced by the Sun, could cause a surviving large part of an Earth-impactor (the authors call this a ‘runner’) to move inward and...

Cloud Layers at WASP-127b

by Paul Gilster | Sep 24, 2021 | Exoplanetary Science | 19 Comments

A 'hot Saturn' with a difference, that's WASP-127b. Although it's 525 light years away, we've learned a surprising amount about the planet's atmosphere. Details come via the ongoing Europlanet Science Congress 2021, now being held virtually for pandemic reasons, at which Romain Allart (iREx/Université de Montréal and Université de Genève) spoke this week. WASP-127b is quite an unusual planet with or without cloud cover. It's orbiting its star in a scant four days, amped up by stellar irradiation levels 600 times what the Earth receives from the Sun. That would, the researcher points out, produce temperatures in the range of 1100 degrees Celsius (over 1370 Kelvin). The result of all these factors is a world with a fifth the mass of Jupiter actually inflating into a radius 1.3 larger than Jupiter. The word in vogue among astrophysicists for a planet like this seems to be 'fluffy,' which pretty much describes it. Image: WASP-127b compared with planets of our Solar...

Keeping an Eye on Psyche

by Paul Gilster | Sep 23, 2021 | Asteroid and Comet Deflection | 8 Comments

What makes the asteroid 16 Psyche interesting is that it may well be the exposed core of a planet from the early days of Solar System formation, a nickel-iron conglomeration that normally would lie well below a surface mantle and crust. It's also an M-class asteroid, a category of which it is the largest known sample. These are mostly made of nickel-iron and thought to be fragmented cores, though many have a composition that has not yet been determined. Image: Deep within the terrestrial planets, including Earth, scientists infer the presence of metallic cores, but these lie unreachably far below the planets' rocky mantles and crusts. Because we cannot see or measure Earth's core directly, asteroid Psyche offers a unique window into the violent history of collisions and accretion that created the terrestrial planets. Credit: University of Arizona. M-class asteroids have been imaged before -- the Rosetta spacecraft imaged the non-metallic 21 Lutetia in 2010, and 216 Kleopatra has been...

Pondering SETI Strategy

by Paul Gilster | Sep 21, 2021 | Astrobiology and SETI | 78 Comments

I try to keep my ear to the ground (rather than my eye to the sky) when it comes to SETI. What I mean is that there are enough scientists working SETI issues that it's a challenge to know who is doing what. I try to track ongoing discussions even when, as at a conference, people keep ducking into and out of audibility. Hence the possibility of overlap in SETI efforts and, as Jason Wright points out in a discussion on his AstroWright site, the circulation of the same ideas without moving the ball forward. This is hardly a new phenomenon, as a look back at my own grad school experience in a much different area reveals. I was a medievalist with an ear for language, and I was always struck by how compartmentalized we tended to be when discussing medieval linguistics. At that time, northern European tongues like Gothic, Old Icelandic, Anglo-Saxon and Old Saxon formed a scholarly thicket I happily wandered through, but in the absence of computerized resources back in the day, the Gothic...

Tracking Missing Ammonia on the Ice Giants

by Paul Gilster | Sep 20, 2021 | Outer Solar System | 4 Comments

Something interesting always comes out of the Europlanet Science Congress (probably better known to Centauri Dreams readers under its former name, the European Planetary Science Congress), and this year is no exception. This is the largest planetary science meeting in Europe, normally drawing about 1000 participants, though last year and this year as well have been virtual meetings, the latter ongoing as I write this and running until September 24. As the conference proceeds, my eye was drawn to a study by Tristan Guillot on the ice giants Uranus and Neptune, targets of (let’s hope) future space missions that can help us resolve the differences between this class of world and gas giants like Jupiter and Saturn. Guillot (CNRS, Laboratoire Lagrange, Nice) targets the odd fact that both of these planets have recently been found to be deficient in ammonia in their atmospheres as compared to the gas giants. Astronomers are puzzled because other compounds such as methane, found in the...

Adjusting the Clock: Hydrogen Burning in White Dwarfs

by Paul Gilster | Sep 17, 2021 | Deep Sky Astronomy & Telescopes | 15 Comments

White dwarfs have turned out to be more interesting than I had imagined. We know how they form: A star like the Sun exhausts the hydrogen in its core and swells into a red giant, a scenario that is a trope in science fiction, as it posits an Earth of the far-future incinerated by its star. Losing its outer layers near the end of nuclear burning, a red giant ultimately leaves behind an object with much of the mass of the Sun now crammed into a white dwarf that is about the size of the Earth. For years I assumed white dwarfs were dead ends, a terminus for life whose only function seemed to be in binary systems, where they could be the locus, through accretion from the other star, of a stellar explosion in the form of a nova. Lately we've been learning, though, that through analysis of their atmospheres, white dwarfs can yield information about objects that have fallen into them, such as remnants of the original stellar system. Some white dwarfs may have habitable zones lasting several...

Predicting a Supernova in 2037

by Paul Gilster | Sep 16, 2021 | Deep Sky Astronomy & Telescopes | 7 Comments

Here's a story that's both mind-bending and light-bending. It involves a supernova that, on the one hand, happened 10 billion years ago, and on the other hand, has appeared in our skies not once but three times, with a fourth in the works. In play here is gravitational lensing, in which light from a background galaxy bends around a foreground galactic cluster known as MACS J0138.0-2155. Out of this we get multiple mirror images, and researchers predict another supernova appearance in the year 2037. Three of the appearances of the supernova, labeled AT 2016jka and nicknamed 'Requiem,' are in the image below, a Hubble view from 2016, all three circled for ease of identification. The light of the supernova has been split into different images by the lensing effect. Using archival data, researchers led by Steve Rodney (University of South Carolina) have analyzed differences in brightness and color that reflect different phases of the event as the supernova faded. "This new discovery is...

Exomoons: The Binary Star Factor

by Paul Gilster | Sep 14, 2021 | Uncategorized | 2 Comments

Centauri Dreams readers will remember Billy Quarles’ name in connection with a 2019 paper on Alpha Centauri A and B, which examined not just those stars but binary systems in general in terms of obliquity -- axial tilt -- on potential planets as affected by the gravitational effects of their systems. The news for habitability around Centauri B wasn’t good. Whereas the Moon helps to stabilize Earth’s axial tilt, the opposite occurs on a simulated Centauri B planet. And without a large moon, gravitational forcing from the secondary star still causes extreme obliquity variations. Orbital precession induced by the companion star is the problem, and it may be that Centauri A and B are simply too close together, whereas more widely separated binaries are less disruptive. I’ll send you to the paper for more (citation below), but you can get an overview with Axial Tilt, Habitability, and Centauri B. It’s exciting to think that our ongoing investigations of Centauri A and B will, one of these...

SETI as a Central Project: An Addendum to Space Development Futures

by Paul Gilster | Sep 10, 2021 | Culture and Society | 58 Comments

How does SETI fit into the long-term objectives of a civilization? To a society whose central project is communication, the 'success' of the project in detecting intelligence around another star is obviously not assured, but if it does find a signal, would it eventually receive an Encyclopedia Galactica? There is much to ponder here, and Nick Nielsen today tackles the question from the standpoint of not one but many Encylopedia Galacticas, spread out through cosmological time as opposed to the 'snapshot' version a finite species sees. Read on to consider the kinds of civilizations that might practice or be discovered by SETI and how they might formulate their listening and communications strategy. SETI is analyzed here as one of a variety of central projects Nielsen has examined in these pages and elsewhere. For more of his work, consult Grand Strategy: The View from Oregon, and Grand Strategy Annex. by J. N. Nielsen 1. Variations on the Theme of Spacefaring Civilization 2. A Missed...

1001 Near-Earth Objects for Planetary Radar

by Paul Gilster | Sep 9, 2021 | Asteroid and Comet Deflection | 9 Comments

A century ago, when American magazine science fiction was developing, the Solar System seemed a relatively tidy place. At least, it did in comparison to today. The first issue of Hugo Gernsback's Amazing Stories serialized a reprint of Jules Verne's 1877 novel Off on a Comet and, indeed, in those days comets were the objects most likely to move around the system. The asteroids seemed distant in their belt and in stable orbits and there was little else between the planets. There was no Pluto. Today, of course, we seem to have debris everywhere. The main belt asteroids are joined by trojan objects like the large population around Jupiter, and there is another belt of ancient material out beyond Neptune, the Kuiper Belt. In Earth's neighborhood, interesting objects like 2021 PJ1, whose approach to our planet occurred on August 14 at 1.7 million kilometers, remind us that there is a large population of asteroids that move in orbits well inside the main belt, and could conceivably present...

The Unusual Prescience of Edgar Allan Poe

by Paul Gilster | Sep 7, 2021 | Culture and Society | 27 Comments

Writing about Karel ?apek, as Milan ?irkovi? did in our last entry, spurs me to note that the BBC has an interesting piece out on ?apek called The 100-year-old fiction that predicted today. It’s a fine essay delivered by Dorian Lynskey on both ?apek and the Russian writer Yevgeny Zamyatin, whose influential novel We shared a birth year of 1921 with ?apek’s R.U.R. If ?apek gave us robots, it could be said that Zamyatin gave us the modern dystopia. “If you have had any experience with science fiction,” writes Lynskey, “you will probably have imbibed some trace elements of RUR and We.” I will defer on Zamyatin, for I suspect that Dr. ?irkovi? has thoughts about him that will appear in a future essay here. However, looking toward the origins of ideas has me thinking about another literary figure, the American writer and critic Edgar Allan Poe. Always known for his tales of the macabre, Poe (1809-1848) more or less invented the detective story, but he was also influential in the origins...

Robot at 100

by Paul Gilster | Sep 3, 2021 | Culture and Society | 83 Comments

If biological life gives way to its own creations, should we adjust our SETI outlook to include entire civilizations composed of artificial intelligences? A postbiological culture was certainly on the mind of the Czech writer Karel ?apek (1890-1938), whose work is the subject of today's essay by Milan ?irkovi?. It's a good time to reassess this author as we careen toward what may or may not be a 'singularity,' when digital intelligence eclipses our own. As ?irkovi? explains, ?apek was an utterly indefatigable writer whose work is less well known in the west than it should be given its significance not only to science fiction but the study of the future. Dr. ?irkovi? is a research professor at the Astronomical Observatory of Belgrade, the author of numerous research and professional papers as well as three research monographs and four books, the most recent of which is The Great Silence: The Science and Philosophy of Fermi’s Paradox (Oxford University Press). Read on to learn about...

Deep Space Network: A Laser Communications Future

by Paul Gilster | Sep 2, 2021 | Communications and Navigation | 10 Comments

Recent updates to the Deep Space Network have me thinking about the data capabilities of laser communications, and how they will change the way missions operate. In late October, a payload called the Laser Communications Relay Demonstration (LCRD) is scheduled for launch aboard an Atlas V from Cape Canaveral. LCRD will begin its work by receiving radio frequency test signals from the mission operations center and responding with optical signals. Ultimately, the mission should be able to receive data from other missions and relay to the ground. What we have here is NASA’s first technology demonstration of a two-way laser relay system, one that will test laser capabilities to find out, for example, about the potentially disruptive effect of clouds. Because optical signals cannot penetrate them, plans are for LCRD to transmit data from missions to separate ground stations, one in Table Mountain, California and the other at Haleakal? in Hawaii, both chosen because of their low degree of...

Odd Find: An Ancient Brown Dwarf?

by Paul Gilster | Sep 1, 2021 | Deep Sky Astronomy & Telescopes | 6 Comments

The brown dwarf WISEA J153429.75-104303.3 -- happily nicknamed ‘The Accident’ -- is peculiar enough that it may point to a rare population of extremely old brown dwarfs. Dan Caselden, a citizen scientist who built an online program to filter data from the NEOWISE spacecraft, is able to highlight brown dwarfs moving through the NEOWISE field with his software, and while looking at one, he caught a glimpse of another. Call that a lucky catch, because the object didn’t match his program’s profile of a conventional brown dwarf. We’ve found about 2,000 brown dwarfs thus far, many using data from WISE -- Wide Field Infrared Survey Explorer -- which was launched in 2009, placed into hibernation in 2011 after its primary mission ended, and then reactivated in 2013 as NEOWISE, a repurposed spacecraft given the new goal of tracking near-Earth objects. WISE 1534?1043 -- the shortened name of the object, used by the authors of a new paper on it -- stands out from all previously known brown...

Charter

In Centauri Dreams, Paul Gilster looks at peer-reviewed research on deep space exploration, with an eye toward interstellar possibilities. For many years this site coordinated its efforts with the Tau Zero Foundation. It now serves as an independent forum for deep space news and ideas. In the logo above, the leftmost star is Alpha Centauri, a triple system closer than any other star, and a primary target for early interstellar probes. To its right is Beta Centauri (not a part of the Alpha Centauri system), with Beta, Gamma, Delta and Epsilon Crucis, stars in the Southern Cross, visible at the far right (image courtesy of Marco Lorenzi).

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