Paul Gilster | Centauri Dreams

Tuning Up for Europa

by Paul Gilster | Aug 23, 2022 | Outer Solar System | 17 Comments

The new Jupiter photos from JWST's Near Infrared Camera (NIRCam) are unusual, enough so that I decided to fold one into today's post. It's a pretty good fit because I had already put together most of the material I was going to use about Europa. It would have been an additional plus if Europa showed up in the image below, but even without it, note that we can see moons as small as Adrasta here. Imke de Pater (UC-Berkeley), who led the observations, noted that both tiny satellites and distant galaxies show up in the same image. And here's Thierry Fouchet, a professor at the Paris Observatory, who likewise worked on the observing effort: "This image illustrates the sensitivity and dynamic range of JWST's NIRCam instrument. It reveals the bright waves, swirls and vortices in Jupiter's atmosphere and simultaneously captures the dark ring system, 1 million times fainter than the planet, as well as the moons Amalthea and Adrastea, which are roughly 200 and 20 kilometers across,...

Mapping Out Interstellar Clouds

by Paul Gilster | Aug 19, 2022 | Interstellar Medium | 16 Comments

Although I've written on a number of occasions about the project called Interstellar Probe, the effort to create what we might call a next-generation Voyager equipped to study space beyond the heliosphere, it's always been in terms of looking back toward the Solar System. What is the shape of the heliosphere once we see it from outside, and how does it interact with the local interstellar medium? The Voyagers have given us priceless clues, but they were never designed for this environment and in any case will soon exhaust their energies. Pontus Brandt (JHU/APL), who is project scientist for the Interstellar Probe effort, takes us beyond these heliosphere-centric ideas as he talks to Richard Stone in a fine article about the mission called The Long Shot that ran recently in Science. Because when you launch something moving faster than Solar System escape velocity, you just keep going, and while 1000 AU is often cited as a target for this mission, it's really only a milestone marker...

Laser Communications: A Step at a Time to Deep Space

by Paul Gilster | Aug 16, 2022 | Communications and Navigation | 13 Comments

My last look at laser communications inside the NASA playbook was a year ago, and for a variety of reasons it's time to catch up with the Laser Communications Relay Demonstration (LCRD), which launched in late 2021, and the projects that will follow. LCRD has now been certified for its mission of shaking out laser systems in terms of effectiveness and potential for relay operations. Ideally, we’d like to receive data from other missions and relay to the ground in a seamless optical network. How close are we to such a result? Image: The Laser Communications Relay Demonstration payload. Credit: NASA Goddard Space Flight Center. LCRD is now in geosynchronous orbit almost 36,000 kilometers above the equator, poised for its two year mission, but before we proceed, note this. The voice is that of Rick Butler, project lead for the LCRD experimenters program at NASA GSFC: “We will start receiving some experiment results almost immediately, while others are long-term and will take time for...

Musings on Art, Brown Dwarfs & Galactic Disks

by Paul Gilster | Aug 12, 2022 | Culture and Society | 30 Comments

I was getting ready to start writing a story with implications for brown dwarfs and the galaxy’s ‘thick disk’ (as opposed to its ‘thin disk,’ about which more in a moment) when I ran across the artwork below. This is the work of French artist and astronomer Étienne Léopold Trouvelot (1827-1895), whose careful astronomical observations were rendered into illustrations and pastel drawings in the era before astrophotography. I learned from Maria Popova’s The Marginalian that Trouvelot produced 50 scientific papers, but almost 7000 works of art based on what he saw. Thus the study of part of the Milky Way below, evidently created somewhere between 1874 and 1876. Trouvelot’s work caught the attention of the director of the Harvard Observatory, who invited him to join its staff in 1872. The concept of his art was to get across to those without the privilege of seeing these objects through a telescope just how they looked to a trained scientist. He przed the value of human rendering over...

CNEOS 2014-01-08: Sampling the Interstellar Meteor

by Paul Gilster | Aug 9, 2022 | Astrobiology and SETI | 23 Comments

How unusual that the study of an interstellar object should receive a boost from the United States Space Command, which is responsible for US military operations off-planet. But that’s part of the story of CNEOS 2014-01-08, which is described in its discovery paper as “a meteor of interstellar origin.” The 2019 finding came from Harvard’s Avi Loeb, working with then undergraduate student Amir Siraj. Loeb had been examining a catalog containing data on meteors over the last three decades in terms of the strength of their fireball, prompted by a 2018 fireball off the Kamchatka peninsula. The Kamchatka meteor produced a blast with ten times the energy of the Hiroshima bomb, leading Loeb to put Siraj to work on calculating the past trajectories of the fastest meteors in the CNEOS catalog – CNEOS is NASA’s Center for Near Earth Object Studies. In an email yesterday morning, Loeb explained that numerous factors went into the study. Siraj was able to work with the position and velocity of...

Ross 508 b: What We Can Learn from a Red Dwarf Super-Earth

by Paul Gilster | Aug 5, 2022 | Exoplanetary Science | 46 Comments

The discovery of a super-Earth around the M-dwarf Ross 508 gives us an interesting new world close to, if not sometimes within, the inner edge of the star’s habitable zone. This is noteworthy not simply because of the inherent interest of the planet, but because the method used to detect it was Doppler spectroscopy. In other words, radial velocity methods in which we study shifts in the spectrum of the star are here being applied to a late M-dwarf that emits most of its energies in the near-infrared (NIR). I usually think about transits in relation to M-dwarf planets, because our space-based observatories, from CoRoT to Kepler and now TESS, have demonstrated the power of these techniques in finding exoplanets. M-dwarfs are made to order for transits because they’re small enough to offer deep transits – the signature of the planet in the star’s lightcurve is more pronounced than a transit across a larger star. From a radial velocity perspective, planets in an M-dwarf habitable zone...

Interstellar Deceleration: Can We Ride the ‘Bow Shock’?

by Paul Gilster | Aug 2, 2022 | Deep Sky Astronomy & Telescopes | 25 Comments

Interesting things happen at the edge of the Solar System. Or perhaps I should say, at the boundary of the heliosphere, since the Solar System itself conceivably extends (in terms of possible planets) further out than the 100 or so AU that marks the heliosphere's boundary at its closest. The fact that the heliosphere is pliable and reacts among other things to the solar cycle in turns means that the boundary is a moving target. It would be useful if we could get something like JHU/APL's Interstellar Probe mission out well beyond the heliosphere to help us understand this morphology better. But let's think about the heliosphere's boundaries from the standpoint of incoming spacecraft. Because deceleration at the destination system is a huge problem for starship mission planning. A future crew, human or robotic, could deploy a solar sail to slow down, but a magsail seems better, as its effects kick in earlier on the approach. Looking at the image below, however, suggests another...

The Challenge of ‘Twilight Asteroids’

by Paul Gilster | Jul 29, 2022 | Asteroid and Comet Deflection | 13 Comments

We have the Zwicky Transient Facility at Palomar Observatory to thank for the detection of the strikingly named 'Ayló'chaxnim (2020 AV2). This is a large near-Earth asteroid with a claim to distinction, being the first NEO found to orbit inside the orbit of Venus. I love to explore the naming of things, and now that we have 'Ayló'chaxnim (2020 AV2), we have to name the category, at least provisionally. The chosen name is Vatira, which in turn is a nod to Atira, a class of asteroids that orbit entirely inside Earth's orbit. Thus Vatira refers to an Atira NEO with orbit interior to Venus. As to the 'Ayló'chaxnim, it's a word from indigenous peoples whose ancestral lands took in the mountainous region where the Palomar Observatory is located. I'm told by the good people at Caltech that the word means something like 'Venus Girl.' On June 7, people of Pauma descent gathered for a ceremony at the observatory, having been asked by the team manning the Zwicky Transient...

Getting There Quickly: The Nuclear Option

by Paul Gilster | Jul 26, 2022 | Advanced Rocketry | 38 Comments

Adam Crowl has been appearing on Centauri Dreams for almost as long as the site has been in existence, a welcome addition given his polymathic interests and ability to cut to the heart of any issue. His long-term interest in interstellar propulsion has recently been piqued by the Jet Propulsion Laboratory's work on a mission to the Sun's gravitational lens region. JPL is homing in on multiple sailcraft with close solar passes to expedite the cruise time, leading Adam to run through the options to illustrate the issues involved in so dramatic a mission. Today he looks at the pros and cons of nuclear propulsion, asking whether it could be used to shorten the trip dramatically. Beamed sail and laser-powered ion drive possibilities are slated for future posts. With each of these, if we want to get out past 550 AU as quickly as possible, the devil is in the details. To keep up with Adam's work, keep an eye on Crowlspace. by Adam Crowl The Solar Gravitational Lens amplifies signals from...

Solar Gravitational Lens: Sailcraft and In-Flight Assembly

by Paul Gilster | Jul 22, 2022 | Missions | 20 Comments

The last time we looked at the Jet Propulsion Laboratory’s ongoing efforts toward designing a mission to the Sun’s gravitational lens region beyond 550 AU, I focused on how such a mission would construct the image of a distant exoplanet. Gravitational lensing takes advantage of the Sun’s mass, which as Einstein told us distorts spacetime. A spacecraft placed on the other side of the Sun from the target exoplanetary system would take advantage of this, constructing a high resolution image of unprecedented detail. It’s hard to think of anything short of a true interstellar mission that could produce more data about a nearby exoplanet. In that earlier post, I focused on one part of the JPL work, as the team under the direction of Slava Turyshev had produced a paper updating the modeling of the solar corona. The new numerical simulations led to a powerful result. Remember that the corona is an issue because the light we are studying is being bent around the Sun, and we are in danger of...

Getting Down to Business with JWST

by Paul Gilster | Jul 19, 2022 | Exoplanetary Science | 32 Comments

So let’s get to work with the James Webb Space Telescope. Those dazzling first images received a gratifying degree of media attention, and even my most space-agnostic neighbors were asking me about what exactly they were looking at. For those of us who track exoplanet research, it’s gratifying to see how quickly JWST has begun to yield results on planets around other stars. Thus WASP-96 b, 1150 light years out in the southern constellation Phoenix, a lightweight puffball planet scorched by its star. Maybe 'lightweight' isn’t the best word. Jupiter is roughly 320 Earth masses, and WASP-96b weighs in at less than half that, but its tight orbit (0.04 AU, or almost ten times closer to its Sun-like star than Mercury) has puffed its diameter up to 1.2 times that of Jupiter. This is a 3.5-day orbit producing temperatures above 800 ?. As you would imagine, this transiting world is made to order for analysis of its atmosphere. To follow JWST's future work, we’ll need to start learning new...

Spatial-Temporal Variance Explanation for the Fermi Paradox

by Paul Gilster | Jul 14, 2022 | Astrobiology and SETI | 73 Comments

Just how likely is it that the galaxy is filled with technological civilizations? Kelvin F Long takes a look at the question using diffusion equations to probe the possible interactions among interstellar civilizations. Kelvin is an aerospace engineer, physicist and author of

Probing the Galaxy: Self-Reproduction and Its Consequences

by Paul Gilster | Jul 12, 2022 | Culture and Society | 35 Comments

In a long and discursive paper on self-replicating probes as a way of exploring star systems, Alex Ellery (Carleton University, Ottawa) digs, among many other things, into the question of what we might detect from Earth of extraterrestrial technologies here in the Solar System. The idea here is familiar enough. If at some point in our past, a technological civilization had placed a probe, self-replicating or not, near enough to observe Earth, we should at some point be able to detect it. Ellery believes such probes would be commonplace because we humans are developing self-replication technology even today. Thus a lack of probes would indicate that there are no extraterrestrial civilizations to build them. There are interesting insights in this paper that I want to explore, some of them going a bit far afield from Ellery's stated intent, but worth considering for all that. SETA, the Search for Extraterrestrial Artifacts, is a young endeavor but a provocative one. Here...

Two Close Stellar Passes

by Paul Gilster | Jul 8, 2022 | Deep Sky Astronomy & Telescopes | 31 Comments

Interstellar objects are much in the news these days, as witness the flurry of research on ‘Oumuamua and 2I/Borisov. But we have to be cautious as we look at objects on hyperbolic orbits, avoiding the assumption that any of these are necessarily from another star. Spanish astronomers Carlos and Raúl de la Fuente Marcos dug several years ago into the question of objects on hyperbolic orbits, noting that some of these may well have origins much closer to home. Let me quote their 2018 paper on this: There are mechanisms capable of generating hyperbolic objects other than interstellar interlopers. They include close encounters with the known planets or the Sun, for objects already traversing the Solar system inside the trans-Neptunian belt; but also secular perturbations induced by the Galactic disc or impulsive interactions with passing stars, for more distant bodies (see e.g. Fouchard et al. 2011, 2017; Królikowska & Dybczy?ski 2017). These last two processes have their sources beyond...

The Great Venusian Bug Hunt

by Paul Gilster | Jul 5, 2022 | Astrobiology and SETI | 31 Comments

Our recent focus on life detection on nearby worlds concludes with a follow-up to Alex Tolley's June essay on Venus Life Finder. What would the sequence of missions look like that resulted in an unambiguous detection of life in the clouds of Venus? To answer that question, Alex takes the missions in reverse order, starting with a final, successful detection, and working back to show what the precursor mission to each step would have needed to accomplish to justify continuing the effort. If the privately funded VLF succeeds, it will be in the unusual position of making an astrobiological breakthrough before the large space organizations could achieve it, but there are a lot of steps along the way that we have to get right. by Alex Tolley In my previous essay, Venus Life Finder: Scooping Big Science, I introduced the near-term, privately financed plan to send a series of dedicated life-finding probes to Venus' clouds. The first was a tiny atmosphere entry vehicle with a dedicated...

Drilling into Icy Moon Oceans

by Paul Gilster | Jul 1, 2022 | Outer Solar System | 52 Comments

While we talk often about subsurface oceans in places like Europa, the mechanisms for getting through layers of ice remain problematic. We'll need a lot of data through missions like Europa Clipper and JUICE just to make the call on how thick Europa's ice is before determining which ice penetration technology is feasible. But it's exciting to see how much preliminary work is going into the issue, because the day will come when one or another icy moon yields the secrets of its ocean to a surface lander. By way of comparison, the thickest ice sheet on Earth is said to reach close to 5,000 meters. This is at the Astrolabe Subglacial Basin, which lies at the southern end of Antarctica's Adélie Coast. Here we have glacial ice covering continental crust, as opposed to ice atop an ocean (although there appears to be an actively circulating groundwater system, which has been recently mapped in West Antarctica). The deepest bore into this ice has been 2,152 meters, a 63 hour continuous...

Biofinder: A Remote Sensing Solution for Detecting Life

by Paul Gilster | Jun 28, 2022 | Astrobiology and SETI | 19 Comments

My prediction that we're going to find evidence for exo-life around another star before we find it in our own Solar System is being challenged from several directions. Alex Tolley recently looked at the Venus Life Finder mission, a low-cost and near-term way to examine the clouds of the nearest planet for evidence of biology (see Venus Life Finder: Scooping Big Science). Now we learn of advances in a ten-year old project at the University of Hawai'i at Manoa, where Anupam Misra and team have been working on remote sensing instruments to detect minute biomarkers. This one looks made to order for Mars, but it also by extension speaks to future rovers on a variety of worlds. Image: This artist's impression shows how Mars may have looked about four billion years ago. The young planet Mars would have had enough water to cover its entire surface in a liquid layer about 140 m deep, but it is more likely that the liquid would have pooled to form an ocean occupying almost half of Mars's...

Of Algorithms and Hidden Planets

by Paul Gilster | Jun 24, 2022 | Exoplanetary Science | 24 Comments

It’s hard to imagine what the field of exoplanet discovery will look like in a hundred years. Just as difficult as it is to imagine what might happen if we do get to a ‘singularity’ in machine intelligence beyond which we humans can’t venture. Will the study of other stellar systems become largely a matter of computers analyzing data acquired by AI, with human operators standing by only in case of equipment failure? Or will the human eye for pattern and detail so evident in many current citizen science projects always be needed to help us piece together what the machines find? I wonder this when I read about the effort going into teasing new data out of older observations, as we saw recently in VASCO, a project to study old astronomical photographic plates looking for possible technosignatures. And I suspect we’ll always need human/machine collaboration to draw maximum knowledge out of our data. Today let’s look at how useful software tools are illuminating what we’ve already learned...

White Dwarfs: Planetary System Rebirth?

by Paul Gilster | Jun 21, 2022 | Exoplanetary Science | 21 Comments

Let's catch up with white dwarfs, a kind of star that may spawn planetary systems of its own. For I've just found another case of archival data being put to good use in the form of a study of a white dwarf system called G238-44. Here, the data come from the Hubble instrument (specifically, its Cosmic Origins Spectrograph and Space Telescope Imaging Spectrograph), the Far Ultraviolet Spectroscopic Explorer (FUSE), and the Keck Observatory's High Resolution Echelle Spectrometer (HIRES) in Hawaii. What astronomers presented at a recent AAS conference is a picture of a system severely disrupted by its star's transition to white dwarf status. Moreover, this is a star in the process of accretion with a distinct twist from earlier such discoveries. For the white dwarf - the remnant left behind after the system's star went through its red giant phase - is actively drawing rocky and metallic material as well as ices from the debris of the disrupted system. These are the stuff of planet...

‘Lurker’ Probes & Disappearing Stars

by Paul Gilster | Jun 17, 2022 | Astrobiology and SETI | 39 Comments

We've looked before at the growing interest in exploring near-Earth space for evidence of probes from other civilizations that may have been sent in the distant past to monitor and report home on the progression of life in our Solar System. If extraterrestrial civilizations exist, the idea that one of them might have explored our system and left behind what Jim Benford calls a 'lurker' probe is sensible enough. We send probes to places we want to learn more about, and we would certainly have probes around the nearest stars if we had the means. Breakthrough Starshot is an example of such interest. A century from now, human probes to other stars may be commonplace. Various places to search for lurker probes have been suggested, from Lagrange points - where objects placed there tend to stay put, with minimal need for fuel consumption - to barely studied Earth co-orbitals to the surface of the Moon. But what about Earth orbit? Surveillance of the Earth could involve probes in long-term...

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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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