Archives

Thoughts on Immensity

by Paul Gilster | Oct 8, 2020 | Deep Sky Astronomy & Telescopes | 39 Comments

The Hubble Deep Field images of 1995 and 1998 gave us an unprecedented look at a small patch of sky with few nearby bright objects, a region about one-tenth the diameter of the full Moon in the constellation Fornax. The ensuing Hubble Ultra Deep Field, released in 2004, contains as many as 10,000 individual galaxies. Hubble's Advanced Camera for Surveys (ACS) was deployed for this, as well as its Near Infrared Camera and Multi-object Spectrometer (NICMOS), producing a stunning harvest of elliptical and spiral galaxies, as well as oddly shaped collections of stars from the chaotic early days of the universe. Image: The original NASA release image of the Hubble Ultra Deep Field, containing galaxies of various ages, sizes, shapes, and colors. The smallest, reddest galaxies, of which there are approximately 10,000, are some of the most distant galaxies to have been imaged by an optical telescope, probably existing shortly after the Big Bang. Credit: NASA/ESA. I immediately thought of a...

Kuiper Belt Oddity? Explaining Arrokoth’s Shape

by Paul Gilster | Oct 7, 2020 | Outer Solar System | 14 Comments

Now and then people mention that our Pioneers and Voyagers made it through the Kuiper Belt on their long journey toward system's edge, though unfortunately without operational cameras to record what they saw. A missed opportunity? Not really. Think about how long it took to find a Kuiper Belt Object like Arrokoth, the first one ever seen close up thanks to the mighty work of the New Horizons team. Without a major search to find a target, a craft passing through the Kuiper Belt is almost certainly going to encounter no objects whatsoever within range to record the details. For now, Arrokoth, the object once known as Ultima Thule before running afoul of our times, has to serve as our example of what can emerge in this distant region, and an odd object it is. When its shape is compared to a flattened snowman, as it often is, the real story is in the word 'flattened.' How does this roughly 30-kilometer object emerge in the shape it's in, and under what conditions was it spawned out there...

The Best of All Possible Worlds

by Paul Gilster | Oct 6, 2020 | Exoplanetary Science | 74 Comments

I've always loved the notion of 'superhabitability,' which forces us to ask whether, in our search for planets like the Earth, we may in our anthropocentric way be assuming that our own planet is a kind of ideal. Some scientists have been asking for years whether it is possible that the Earth is not as 'habitable' as it might be (see What Makes a Planet 'Superhabitable'?). The question then becomes: What factors would make a planet a better place for life than our own? Now Dirk Schulze-Makuch (Washington State University), working with René Heller (Max Planck Institute for Solar System Research, Göttingen) and Edward Guinan (Villanova University) runs through the characteristics of superhabitability, which take in planets that are a bit warmer than ours, a bit larger, and somewhat wetter, not to mention those that circle stars that live longer than our G-class Sun. 24 interesting planets emerge, all more than 100 light years out, but none of those so far identified meet all...

Dark Skies: Space Expansionism, Planetary Geopolitics, and the Ends of Humanity: A Review

by Paul Gilster | Oct 2, 2020 | Culture and Society | 77 Comments

While we often discuss expansion into the Solar System as a step leading to interstellar flight, the movement into space has its dark side, as author Daniel Deudney argues in a new book. As Kenneth Roy points out in the review that follows, it behooves everyone involved in space studies to understand what the counter-arguments are. Ken is a newly retired professional engineer who is currently living amidst, as he puts it, "the relics of the Manhattan Project in Oak Ridge, Tennessee." His professional career involved working for various Department of Energy (DOE) contractors in the fields of fire protection and nuclear safety. As a long-time hobby, he has been working with the idea of terraforming, which he extended to the invention of the "Shell Worlds" concept as a way to terraform planets and large moons well outside a star's 'Goldilocks' zone [see Terraforming: Enter the Shell World]. In 1997, Ken made the cover of the prestigious Proceedings of the U.S. Naval Institute for his...

Cometary Alignments and the Galactic Tide

by Paul Gilster | Oct 1, 2020 | Outer Solar System | 5 Comments

A second ecliptic? What an interesting notion, referred to in a new paper from Arika Higuchi as an 'empty ecliptic,' constituting a second alignment plane for the Solar System. This is lively stuff, examined in a new paper in the Astronomical Journal that focuses on the aphelia of long-period comets, the points where they are farthest from the Sun in their orbit. The solutions arrived at through the paper's dense mathematics show that the aphelia fall close to one or the other of the ecliptic planes, and offer insights into comet formation. Higuchi (University of Occupational and Environmental Health, Japan) has previously been a part of the National Astronomical Observatory of Japan's RISE project, RISE standing for Research of Interior Structure and Evolution of solar system bodies. Her work on the orbital evolution of planetesimals goes back at least to 2007 in a paper on the formation of the Oort Cloud, considering the effects of interactions with the 'galactic tide,' a reference...

WASP-189b: An Impressive Debut for CHEOPS

by Paul Gilster | Sep 30, 2020 | Exoplanetary Science | 10 Comments

The European Space Agency’s CHaracterising ExOPlanet Satellite (CHEOPS) space telescope reached space in December of 2019, achieving a Sun-synchronous orbit some 700 kilometers up. The instrument has begun its observations of stars near the Sun that are already known to have planetary companions. The idea is to use the 30 cm optical telescope to constrain radius information for these worlds, previously identified in transit and radial velocity studies. Transiting planets are particularly useful here, because tightening up their radius measurements means we get a better idea of their density, factoring in mass estimates provided by subsequent radial velocity follow-ups. It’s great to see the instrument already hard at work, with measurements of the giant planet WASP-189b, some 325 light years from the Sun, showing us a world that is one of the hottest known, with a likely temperature around 3400?. By comparison, the surface temperature of the Sun is about 6000 ?, while smaller M...

New Approaches to the Age of Saturn’s Moons

by Paul Gilster | Sep 29, 2020 | Outer Solar System | 6 Comments

The presence of the always intriguing Titan brings into sharper focus recent work on the age of the moons of Saturn conducted by Samuel Bell (Planetary Science Institute). Given the active weathering visible on Titan, the assumption that it is at least four billion years old, which draws on earlier work on the age of Saturn’s moon system, is challenged by the lakes, mountains, riverbeds and dunes we see in the Cassini data. Bell argues that an older Titan would have to be one with an extremely low erosion rate and minimal resurfacing. But maybe Titan is younger than we’ve thought. Bell assembles the context of Titan in the overall system at Saturn by studying the cratering rate on the various moons. Determining the age of a planetary surface -- think Mars or the Moon -- is generally done by counting the impact craters and weighing this against the cratering rate. At Saturn, the problem is that the cratering rate is not known. It would be one value if, as previous work has assumed,...

The Technological Indispensability Hypothesis: An Addendum to ‘Bound in Shallows’

by Paul Gilster | Sep 25, 2020 | Culture and Society | 125 Comments

Is there a single technology that can take us from being capable of reaching space to actually building an infrastructure system-wide? Or at least getting to a tipping point that makes the latter possible, one that Nick Nielsen, in today's essay, refers to as a 'space breakout'? We can think of game-changing devices like the printing press with Gutenberg's movable type, or James Watt's steam engine, as altering — even creating — the shape and texture of their times. The issue for space enthusiasts is how our times might be similarly altered. Nick here follows up an earlier investigation of spacefaring mythologies with this look at indispensable technologies, forcing the question of whether there are such, or whether technologies necessarily come in clusters that enforce each other's effects. The more topical question: What is holding back a spacefaring future that after the Apollo landings had seemed all but certain? Nielsen, a frequent author in these pages, is a...

K2-315b: Tight Orbits and the Joy of Numbers

by Paul Gilster | Sep 23, 2020 | Exoplanetary Science | 31 Comments

The newly found planet K2-315b catches the eye because of its 3.14-day orbit, a catch from the K2 extension of the Kepler Space Telescope mission that reminds us of a mathematical constant. As I’m prowling through David Berlinski’s Infinite Ascent (Modern Library, 2011), a quirky and quite lively history of mathematics at the moment, the references to ‘pi in the sky’ that I’m seeing in coverage of the discovery are worth a chuckle. Maybe the Pythagoreans were right that everything is number. Pythagoras would have loved K2-315b and would have speculated on its nature. After all, as Berlinski notes about Pythagoras (ca. 570 to ca. 490 BCE) and his followers, they were devoted to what he calls ‘a higher spookiness”: The Pythagoreans never succeeded in explaining what they meant by claiming that number is the essence of all things. Early in the life of the sect, they conjectured that numbers might be the essence of all things because quite literally “the elements of numbers were the...

Radar for a Giant Planet’s Moons

by Paul Gilster | Sep 22, 2020 | Outer Solar System | 15 Comments

One of my better memories involving space exploration is getting the chance to be at the Jet Propulsion Laboratory to see the Mars rovers Spirit and Opportunity just days before they were shipped off to Florida for their eventual launch. Being near an object that, though crafted by human hands, is about to be a presence on another world is an unusual experience, one that made me reflect on artifacts from deep in the human past and their excavation by archaeologists today. Will future humans one day recover our early robotic explorers? That reflection was prompted by news from JPL that engineers have delivered the key elements of a critical ice-penetrating radar instrument for the European Space Agency's mission to three of Jupiter's icy moons. JUICE -- JUpiter ICy moons Explorer -- is scheduled for a launch in 2022, with plans to orbit Jupiter for three years, involving multiple flybys of both Europa and Callisto, with eventual orbital insertion at Ganymede. Analyses of the interiors...

On White Dwarf Planets as Biosignature Targets

by Paul Gilster | Sep 21, 2020 | Exoplanetary Science | 24 Comments

So often a discovery sets off a follow-up study that strikes me as even more significant in practical terms. This is not for a moment to downplay the accomplishment of Andrew Vanderburg (University of Wisconsin - Madison) and team that discovered a planet in close orbit around a white dwarf. This is the first time we've found a planet that has survived its star's red giant phase and remains in orbit around the remnant, and quite a tight orbit at that. Previously, we've had good evidence only of atmospheric pollution in such stars, indicating infalling material from possible asteroids or other objects during the primary's cataclysmic re-configuration. The white dwarf planet, found via data gathered from TESS (Transiting Exoplanet Survey Satellite) and the Spitzer Space Telescope, makes for quite a discovery. But coming out of this work, I also love the idea of studying such a world with tools we're likely to have soon, such as the James Webb Space Telescope, and on that score, Lisa...

SETI and Altruism: A Dialogue with Keith Cooper

by Paul Gilster | Sep 18, 2020 | Astrobiology and SETI | 72 Comments

Keith Cooper's The Contact Paradox is as thoroughgoing a look at the issues involved in SETI as I have seen in any one volume. After I finished it, I wrote to Keith, a Centauri Dreams contributor from way back, and we began a series of dialogues on SETI and other matters, the first of which ran here last February as Exploring the Contact Paradox. Below is a second installment of our exchanges, which were slowed by external factors at my end, but the correspondence continues. What can we infer from human traits about possible contact with an extraterrestrial culture? And how would we evaluate its level of intelligence? Keith is working on a new book involving both the Cosmic Microwave Background and quantum gravity, the research into which will likewise figure into our future musings that will include SETI but go even further afield. Keith, in our last dialogue I mentioned a factor you singled out in your book The Contact Paradox as hugely significant in our consideration of SETI and...

Odds and Ends on the Clouds of Venus

by Paul Gilster | Sep 17, 2020 | Astrobiology and SETI | 55 Comments

James Gunn may have been the first science fiction author to anticipate the 'new Venus,' i.e., the one we later discovered thanks to observations and Soviet landings on the planet that revealed what its surface was really like. His 1955 tale "The Naked Sky" described "unbearable pressures and burning temperatures" when it ran in Startling Stories for the fall of that year. Gunn was guessing, but we soon learned Venus really did live up to that depiction. I think Larry Niven came up with the best title among SF stories set on the Venus we found in our data. "Becalmed in Hell" is a 1965 tale in Niven's 'Known Space' sequence that deals with clouds of carbon dioxide, hydrochloric and hydrofluoric acids. No more a tropical paradise, this Venus was a serious do-over of Venus as a story environment, and the more we learned about the planet, the worse the scenario got. But when it comes to life in the Venusian clouds -- human, no less -- I always think of Geoffray Landis, not only because...

What Phosphine Means on Venus

by Paul Gilster | Sep 15, 2020 | Astrobiology and SETI | 82 Comments

A biosignature is always going to create a rolling discussion that gradually homes in on a consensus. Which is to say that the recent discovery of phosphine in the upper atmosphere of Venus has inspired a major effort to figure out how phosphine could emerge abiotically. After all, the scientists behind the just published paper on the phosphine discovery seem to be saying something to the community like "We can't come up with a solution other than life to explain this. Maybe you can." The 'maybes' are out there and they include life, but what a tough spot for life to develop, for obvious reasons, not the least of which is the hyper-acidic nature of its clouds. So let's dig into the story a bit more. The idea of life in the cloud layers of an atmosphere has a long pedigree, even on Venus, where discussions go back at least to the 1960s. Harold Morowitz and Carl Sagan examined the matter in a paper in Science in 1967, a speculation that led them to conclude "it is by no means difficult...

Exploring Tidal Heating in Large Moons

by Paul Gilster | Sep 14, 2020 | Outer Solar System | 7 Comments

Io, Jupiter’s large, inner Galilean moon, is the very definition of a tortured surface, as seen in the image below, taken by the Galileo spacecraft in 1997. Discovering volcanic activity -- and plenty of it -- on Io was one of the early Voyager surprises, even if it didn’t surprise astrophysicist Stanton Peale (UC-Santa Barbara) and colleagues, who predicted the phenomenon in a paper published shortly before Voyager 1’s encounter. We now know that Io is home to over 400 active volcanoes, making it the most geologically active body in the Solar System. We’re a long way from the Sun here, but we know to ascribe Io’s surface upheaval to tidal heating forced by the presence of Jupiter as the gravitational forces involved stretch and squeeze not just Io but, of course, Europa, Ganymede and Callisto, all of them interesting because of the possibility of liquid oceans beneath the surface. Io is close enough to the giant world that rock can be melted into magma, but it’s the ice under more...

Janus: Twin Spacecraft to Study Binary Asteroids

by Paul Gilster | Sep 11, 2020 | Outer Solar System | 8 Comments

When we looked earlier this week at the Solaris mission, a concept designed to study the Sun's polar regions, I commented on another early concept called the Auroral Reconstruction CubeSwarm (ARCS). The mission intrigued me because it consisted of CubeSats in swarm formation, working together with numerous ground observatories, to study the Earth's auroras. The paradigm of miniaturization, low cost and creative design surfaces yet again in Janus, a proposal out of the University of Colorado at Boulder and Lockheed Martin that would involve twin spacecraft studying twin targets, the binary asteroids 1996 FG3 and 1991 VH. Daniel Scheeres (CU-Boulder) is principal investigator for Janus, the plan being for the university to handle the analysis of data and images from the mission, with Lockheed Martin building and operating the two spacecraft. It should be a familiar role for both entities, as Lockheed Martin supports operations for OSIRIS-REx at asteroid Bennu, while Scheeres leads the...

OSIRIS-REx: Tracking Bennu’s Unusual Activity

by Paul Gilster | Sep 10, 2020 | Asteroid and Comet Deflection | 10 Comments

OSIRIS-REx, the little spacecraft with the big acronym (standing for Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer) has been on station for a year and a half at asteroid Bennu, monitoring the unexpected activity that distinguishes the object. Particle ejection from the surface is the subject of a revised special issue of the Journal of Geophysical Research: Planets collecting 10 papers on the matter. Specifically, the spacecraft has found that particles of rock mostly of pebble-size are being ejected repeatedly -- one or two per day -- from the asteroid’s surface, some of them escaping into space, some moving into a temporary orbit, with the rest falling back onto the surface. Just days after entering orbit on December 31 of 2018, OSIRIS-REx began to spot the activity, which the introduction to the special issue refers to as “ongoing mass shedding” involving millimeter- to centimeter-scale particles. What we have on our hands here is an...

A SETI Search of 10 Million Star Systems

by Paul Gilster | Sep 9, 2020 | Astrobiology and SETI | 27 Comments

As it is considered a precursor installation, the Murchison Widefield Array (MWA) in Western Australia doesn't get the press that its proposed successor, the Square Kilometer Array (SKA) regularly receives. That's to be expected, given the scope of the SKA, which will involve telescopes in both Australia and South Africa. 14 member countries are developing a project that is to reach over a square kilometer of collecting area, containing thousands of dishes and up to a million low-frequency antennas. If it is built, SKA's angular resolution and survey speed will allow surveys thousands of times faster than those now being conducted. But the Murchison precursor is alive and well, working the 70-300 MHz range and mapping the radio sky. Established by a consortium of universities -- MIT, Swinburne, Curtin and Australian National University -- the telescope is located on a site selected by these universities and managed by Curtin University. CSIRO, Australia's national science agency,...

Solaris: To the Sun’s High Latitudes

by Paul Gilster | Sep 8, 2020 | Missions | 34 Comments

I can think of more than one way to get a good look at the Sun's polar regions. After all, we've done it before, through the Ulysses spacecraft, which passed over the Sun's north and south poles in 1994-1995. A gravity assist at Jupiter was the key to the mission, allowing Ulysses to arc out of the ecliptic and inward to the Sun. But Ulysses lacked the kind of remote-sensing instruments we'd like to use to compile an extensive dataset on the polar magnetic field and, as Don Hassler (SwRI) adds, "the surface/sub-surface flows" we might find in the polar regions. It's good to see a mission designed for that purpose. For Hassler is principal investigator on a concept that has just been approved for further study by NASA, with the haunting name Solaris. I say 'haunting' because it's hard for this Stanislaw Lem reader to forget the novel of the same name, published in 1961, that explores the implications of a vast intelligence on a planet far from Earth. I realize this has been done as a...

A Deformed Protoplanetary Disk in a Triple Star System

by Paul Gilster | Sep 4, 2020 | Exoplanetary Science | 8 Comments

This morning we have two interesting and complementary studies of GW Orionis to look at, both analyzing what is apparently a planet-forming disk with multiple, misaligned rings around this triple star system some 1300 light years from the Sun. In the more recent of the two, Stefan Kraus (University of Exeter) and colleagues used data from both the Atacama Large Millimeter/submillimeter Array (ALMA) and the European Observatory's Very Large Telescope (VLT) in detecting warm gas at the inner edge of the misaligned ring, which has broken away from the larger disc, and scattered light from the warped disk surface. So what could be going on at GW Orionis? What the images reveal is an evolving young system much different from our own. Consider: The inner stars GW Ori A and GW Ori B orbit each other at a separation of a scant 1 AU, while the third star, GW Ori C, orbits the inner stars at a distance of roughly 8 AU, the latter in an orbit that is not aligned with the plane of the inner duo....

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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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