Paul Gilster | Centauri Dreams

Juno at Jupiter: Extended Mission Flybys of Galilean Moons

by Paul Gilster | Jan 11, 2021 | Uncategorized | 21 Comments

The news that NASA will extend the InSight mission on Mars for two years, taking it through December of 2022, is not surprising, given the data trove the mission team has collected through operation of the mission seismometer. A live asset on Mars also deepens our knowledge of the planet's atmosphere and magnetic field, all reasons enough for pushing for another two years. But the extension of the Juno mission to Jupiter deserves more attention than it's getting, given that Juno's remit will be expanded deep into the Jovian system. Image: NASA has extended both the Juno mission at Jupiter through September 2025 and the InSight mission at Mars through December 2022. Credit: NASA/JPL-Caltech. For those of us fascinated with the outer system, this is good news indeed. I'm looking over two documents, the first being a presentation based on a report submitted to NASA' Outer Planets Assessment Group (thanks to Ashley Baldwin for passing this along). The OPAG document was produced by Scott...

Hayabusa2: Multiple Paths for Analyzing an Asteroid

by Paul Gilster | Jan 8, 2021 | Asteroid and Comet Deflection | 6 Comments

Ryugu is classified as a carbonaceous, or C-type asteroid, a class of objects thought to incorporate water-bearing minerals and organic compounds. Carbonaceous chondrites, the dark carbon-bearing meteorites found on Earth, are thought to originate in such asteroids, but it has been difficult if not impossible to determine the source of most individual meteorites. Hence the significance of the Hayabusa2 mission. JAXA's successful foray to Ryugu represents the first time we've been able to examine a sample of a C-type asteroid through direct collection at the site. Ralph Milliken is a planetary scientist at Brown University, where NASA maintains its Reflectance Experiment Laboratory (RELAB). The laboratory expects samples collected at Ryugu to arrive in short order. Milliken is interested in the history of water in the object: "One of the things we're trying to understand is the distribution of water in the early solar system, and how that water may have been delivered to Earth....

The Red Dwarf Habitable Zone Dilemma

by Paul Gilster | Jan 7, 2021 | Uncategorized | 44 Comments

Henry Cordova, whose recent critique of traditional SETI kicked off a lengthy discussion in these pages, has been mulling over issues of habitability in the galaxy's vast population of red dwarf stars. While we've focused on the questions raised by stellar flare activity and the climate challenges of tidal lock, the narrow band of habitability among the fainter M-dwarfs poses its own problems. How big a factor is a narrow circumstellar habitable zone? Henry comes by his interest in these matters by way of US Navy training in both astronomy and mathematics. A retired geographer and map maker now living in southeastern Florida, he's keeping up with exoplanetary issues as an active amateur astronomer and collector of star atlases. by Henry Cordova I am curious as to how the width of a star's habitable zone varies with respect to its luminosity. It would not be unreasonable to assume that the surface temperature of a planet is directly related to the radiant flux of its star....

A Statite ‘Slingshot’ for Catching Interstellar Objects

by Paul Gilster | Jan 5, 2021 | Missions | 17 Comments

I see that a white paper on Richard Linares' interesting 'statite' concept became available just before Christmas, and I want to call your attention to it (and thanks to Antonio Tavani for the pointer). Back in April, the idea received funding as a Phase 1 study in the NASA Innovative Advanced Concepts (NIAC) Program, renewing attention on the matter of interstellar objects (ISO) like 'Oumuamua. The notion is to deliver a payload to an object discovered entering our Solar System so that, unlike the two we've found thus far ('Oumuamua and 2I/Borisov), we can examine them up close before they depart. Statites are to be the enabling technology. So let's circle back to that concept, for statites are getting more interest these days given the plans for Solar Cruiser, NASA's solar sail mission that may experiment with maneuvers that allow it to act in non-Keplerian ways. The idea is that a solar sail can achieve 'station-keeping' -- hovering in place -- by using light pressure from the Sun...

Beamer Technology for Reaching the Solar Gravity Focus Line

by Paul Gilster | Jan 1, 2021 | Uncategorized | 50 Comments

Alex Tolley's essay on using beaming technology to reach the solar gravity focus (SGF) caught the eye of Jim Benford, who has been exploring the prospects for beamed sails for many years. Along with brother Greg, Jim did laboratory work at the Jet Propulsion Laboratory some 20 years ago to demonstrate the method, and in the years since has written extensively on the uses of beaming within the Solar System as well as on interstellar trajectories. But what kind of beam are we talking about? Benford, a plasma physicist and CEO of Microwave Sciences, has done recent work on a gravitational focus mission in connection with Breakthrough Starshot. He points to the maturity of microwave technology and the cost savings involved in using microwaves for a mission far faster than anything that has yet flown. by James Benford An intermediate destination for beamed energy interstellar probes, such as Starshot, is the Sun's Inner Gravitational Focus (SGF). Alex Tolley suggests using Beamer...

A Beamed Sail to the Sun’s Gravity Focus

by Paul Gilster | Dec 29, 2020 | Missions | 69 Comments

Our recent discussions about Claudio Maccone's FOCAL mission to the Sun's gravitational focus, and the ongoing work at the Jet Propulsion Laboratory for NASA's Innovative Advanced Concepts office, have had Alex Tolley thinking about alternative scenarios. Yes, a spacecraft moving along the focal line extending from the solar gravitational lens (SGL) would be capable of extraordinary imaging, and could serve as a communications relay for interstellar probes, but that tricky Sundiver maneuver suggested by Slava Turyshev and team in their 'string of pearls' concept puts huge demands on sail materials. Moreover, we'd ideally like to be able to slow the craft as it moves along the focus, to allow maximum time for observations. To achieve both fast transit and maneuverability at the gravitational focus, Alex advocates beamed propulsion, a method whose advantages and consequences are discussed below. Synergies with the ongoing Breakthrough Starshot effort are apparent. by Alex Tolley The...

A Holiday Thought Looking Ahead

by Paul Gilster | Dec 25, 2020 | Uncategorized | 46 Comments

I want to send along best wishes for the season to all of you. Centauri Dreams started as a book and became a study guide for me as I tried to keep up with ongoing developments in deep space research. But turning the site into a community, which I did in 2005 by adding comments, has been what really made it go, as I've continued to learn from the discussions between readers, finding new resources and different insights I would never have achieved on my own. So thank all of you for this continuing gift, and may this holiday season be the prelude to great discoveries ahead.

Stellar Flares as an Aid to Life Detection

by Paul Gilster | Dec 23, 2020 | Exoplanetary Science | 11 Comments

The interesting transient associated with Proxima Centauri and monitored by Breakthrough Listen reminds us of a key fact about red dwarf stars and the planets around them. Such stars, especially in their youth, are prone to high flare activity, meaning violent, unpredictable emissions that can deplete atmospheric gases like ozone. Even if the atmosphere survives strong stellar winds, the loss of ozone can lead to high levels of ultraviolet radiation reaching the surface and compromising any life there. That stellar flares can be dramatic is captured in the image below, showing a filament eruption from the Sun and accompanying solar flares (credit: NASA/GSFC/SDO). As striking as the image is, it depicts activity on an older star less prone to strong flare activity than younger, smaller stars. We're also fortunate in having the shield offered by Earth's magnetic field, which can deflect the worst of the solar wind. Our G-class Sun lets us orbit at a comfortable distance, but planets in...

A Transient at Proxima Centauri?

by Paul Gilster | Dec 21, 2020 | Astrobiology and SETI | 187 Comments

I see there's now a Wikipedia page for BLC-1, the intriguing SETI detection made by Breakthrough Listen at the Parkes Observatory in Australia. The dataset in which the signal, found at 982 MHz, turned up comes from observations made in April and May of 2019, and it's good to know that Breakthrough is working up two papers on the signal and subsequent analysis, given that the public face of the detection was originally in the form of a story leaked to the British newspaper The Guardian before the backup research was available. Image: CSIRO's Parkes radio telescope in New South Wales, Australia. Credit: Shaun Amy. The first thing to say about BLC-1 is that the acronym stands for Breakthrough Listen Candidate 1, marking the first time a signal has made it through to actual 'candidate' status after five years of observations, which is itself noteworthy given the intensity of the effort. The second thing is that this is a transient, meaning it's short-lived, and it hasn't repeated. That...

JPL Work on a Gravitational Lensing Mission

by Paul Gilster | Dec 16, 2020 | Uncategorized | 41 Comments

Seeing oceans, continents and seasonal changes on an exoplanet pushes conventional optical instruments well beyond their limits, which is why NASA is exploring the Sun's gravitational lens as a mission target in what is now the third phase of a study at NIAC (NASA Innovative Advanced Concepts). All of this builds upon the impressive achievements of Claudio Maccone that we've recently discussed. Led by Slava Turyshev, the NIAC effort takes advantage of light amplification of 1011 and angular resolutions that dwarf what the largest instruments in our catalog can deliver, showing what the right kind of space mission can do. We're going to track the Phase III work with great interest, but let's look back at what the earlier studies have accomplished along the way. Specifically, I'm interested in mission architectures, even as the NASA effort at the Jet Propulsion Laboratory continues to consider the issues surrounding untangling an optical image from the Einstein ring around the Sun....

The FOCAL Radio Bridge

by Paul Gilster | Dec 14, 2020 | Missions | 14 Comments

Getting a probe to another star is a big enough problem, but woven inextricably through it is the issue of communications. Adding payload steepens the propulsion curve in dramatic fashion, which is why recent thinking has dwelled so firmly on miniaturizing the spacecraft. Thus Breakthrough Starshot, which envisions payloads roughly on the order of a computer chip. No wonder, with spacecraft of that size, getting data back to Earth is such a daunting challenge. Can gravitational lensing help? We've seen that the Sun's mass shapes spacetime around it, bending light from targets on the other side so that electromagnetic waves come to a focal point about 550 AU out. The implications for imaging are under intense study at the Jet Propulsion Laboratory, where Slava Turyshev's team, working with a Phase III NIAC grant, is exploring "Direct Multipixel Imaging and Spectroscopy of an Exoplanet with a Solar Gravitational Lens Mission," taking two prior studies, a Phase I and II at NIAC, forward...

Developing FOCAL Mission Concepts

by Paul Gilster | Dec 10, 2020 | Missions | 33 Comments

In the early summer of 2005, I found myself, thanks to the efforts of Greg Matloff and Princeton's Ed Belbruno, in Princeton for a conference called New Trends in Astrodynamics and Applications II, which Dr. Belbruno had organized. I was to give a brief talk at the end of the session summarizing what was going on in the interstellar travel community. Two days of chill rain didn't dampen my enthusiasm at seeing Greg and his wife, the artist C Bangs, as well as Belbruno himself, who had been a great help as I put together my Centauri Dreams book. And on the morning of the first day of the conference, I joined Greg, C and Claudio Maccone for breakfast at the Nassau Inn, Princeton's lovely colonial era hostelry. I've since had the opportunity to talk with Dr. Maccone many times at conferences, and one year enjoyed memorable meals with him in the Italian Alps, but that first encounter really sticks in my mind. I had been thinking about gravitational lensing for several years, but it was...

Claudio Maccone: A Deep Dive into Gravitational Lensing

by Paul Gilster | Dec 9, 2020 | Astrobiology and SETI | 10 Comments

Sorry for the server problems the last few days, which resulted in some tinkering under the hood by people far more skilled at such things than I am. Meanwhile, those experiencing deja vu at seeing this post should take heart -- there is a simple explanation. Last week I posted an earlier article about Claudio Maccone's upcoming presentation on gravitational lensing and the FOCAL mission to exploit it, but had to withdraw the post when I realized the live session, a 'webinar' organized by Ravi Kumar Kopparapu (NASA GSFC) and Jacob Haqq Misra (Blue Marble Space Institute of Science), might not be available beyond a restricted audience. Once that was straightened out, the meeting had already occurred, but fortunately Dr. Maccone's session was recorded and is now available here. I'm going to go ahead and run the rest of that earlier post now, because most people didn't see it. Even so, and despite the fact that it was only up on the site for a few minutes, that turned out to be long...

Server Problems Resolved

by Paul Gilster | Dec 7, 2020 | Administrative | 4 Comments

I'm going to keep Alex Tolley's fine essay (below) at the top for another day, in hopes of re-starting the comment thread that was going along so nicely before the site went down. Then tomorrow we'll start talking about gravitational lensing, in the first of a series that may extend until next week.

Distinguishing Between Biological and Machine Civilization Techno-signatures

by Paul Gilster | Dec 4, 2020 | Astrobiology and SETI | 96 Comments

If we ever make a SETI detection, will it be of biological beings or machine intelligence? As Alex Tolley explains in today's essay, there are reasons for favoring the latter possibility, leading our author to compose what he calls a 'light-hearted speculation' about machines searching for other civilizations of their own kind. Life seems to be easy compared to this. We are developing the tools to delve into planetary atmospheres in search of biosignatures, hoping to cull out ambiguities. But is there an equivalent in the machine world of a biosignature, and how would it be found? Interesting implications arise, some of them seemingly close to home. by Alex Tolley Curiosity Rover. Credit Nasa. Terry Bisson's amusing short sci-fi story "They're made Out of Meat" [4], is a communication between two individuals who express their disbelief that a biological species (detected on Earth by a galactic survey) can possibly be intelligent. The denouement is to erase the record of discovery...

Deep Future: The Next Supercontinent

by Paul Gilster | Dec 2, 2020 | Astrobiology and SETI | 24 Comments

Science fiction writers range freely through time, making many scientific papers fertile ground for plot ideas and settings. So here's an extraordinary one. We know that Earth's continents used to be packed into a single large land mass called Pangaea, which is thought to have broken apart about 200 million years ago as tectonic plates shifted. Interestingly, we can expect a remote future in which the continents will have once again come together, as Michael Way (NASA GSFC) has pointed out at an online poster session at the ongoing virtual meeting of the American Geophysical Union. And such a supercontinent has ramifications for habitability. Let's talk about those because they have a bearing on astrobiology as we examine exoplanets and consider their suitability for life. We're a decade or so (at minimum) away from being able to determine how land and sea are distributed on a nearby world, but climate modeling is useful as we look toward estimating habitability. That involves, as...

Musings on Fusion and the Interstellar Ramjet

by Paul Gilster | Dec 1, 2020 | Advanced Rocketry | 23 Comments

Proton-proton fusion produces 99 percent of the Sun's energy, in a process that begins with two hydrogen nuclei and ends with one helium nucleus, releasing energy along the way. We'd love to exploit the fusion process to create energy for our own directed uses, which is what Robert Bussard was thinking about with his interstellar ramjet when he published the idea in 1960. Such a ship might deploy electromagnetic fields thousands of kilometers in diameter to scoop up atoms from the interstellar medium, using them as reaction mass for the fusion that would drive it. Carl Sagan was a great enthusiast for the concept, and would describe it vividly in the book he wrote with Russian astronomer and astrophysicist Iosif S. Shklovskii. In Intelligent Life in the Universe (1966), the authors discuss a journey that takes advantage of time dilation, allowing a lightspeed-hugging starship powered by these methods to reach galactic center in a mere 21 years of ship-time; i.e., time as perceived by...

A Centaur in Transformation

by Paul Gilster | Nov 30, 2020 | Outer Solar System | 11 Comments

There was a time when the Solar System seemed relatively well defined, with nine planets including Pluto and an asteroid belt that orbited in a niche between Mars and Jupiter. These days, in addition to the Kuiper Belt and Oort Cloud, we have to factor in all the objects that move on unusual orbits. We have a mission in the works, called Lucy, to the Jupiter Trojans, those asteroids that share the giant planet's orbit around the Sun. And today we're looking at Centaurs, which cross the orbits of giant planets and are in rapid dynamical evolution. The subject comes up because a newly discovered comet -- 2019 LD2 (ATLAS) -- is not only a Centaur, but a Centaur that is rapidly on its way to becoming another class of object, a Jupiter Family Comet (JFC). The latter are short-period comets with an orbital period of less than 20 years, largely under the influence of Jupiter. A paper by Jordan Steckloff (Planetary Science Institute) and team lays out the case: Centaurs are objects in...

Exoplanet Imaging via a Fast New Camera

by Paul Gilster | Nov 25, 2020 | Exoplanetary Science | 13 Comments

The world's largest superconducting camera by pixel count has been deployed at the Subaru Telescope at Mauna Kea in Hawaii. This is a technology we'll want to watch, for it assists the effort to image exoplanets directly from the surface of the Earth, a goal that not so long ago would have seemed impossible. But it can be done, and we have a new generation of extremely large telescopes (ELTs) on the way, so the progress in support technology for such installations is heartening. The new device is called the MKID Exoplanet Camera (MEC), with the four-letter acronym standing for Microwave Kinetic Inductance Detector. A superconducting photon detector was first developed as far back as 2003 at Caltech and the Jet Propulsion Laboratory, paving the way for devices that can operate at wavelengths ranging from the far-infrared to X-rays. The MEC comes out of the laboratory of Ben Mazin at the University of California at Santa Barbara as part of an effort that includes contributions from...

Simultaneous Growth of Star and Planet?

by Paul Gilster | Nov 24, 2020 | Deep Sky Astronomy & Telescopes | 1 Comment

The evolving system known as [BHB2007] 1 is a part of the Pipe Nebula (also called Barnard 59), about 600 light years away in the constellation Ophiuchus. It is part of a binary star system in formation that has been studied with the Atacama Large Millimeter Array (ALMA). Both protostars show disks in formation around them, surrounded by filaments of gas and dust drawn from the larger disk that are being referred to as 'feeding filaments.' Paola Caselli (Max Planck Institute for Extraterrestrial Physics, Germany), who made that reference in 2019, is co-author of new work on the stellar object, which gives us an unusual look at early system formation. Image: This false-color image shows the filaments of accretion around the protostar [BHB2007] 1. The large structures are inflows of molecular gas (CO) nurturing the disk surrounding the protostar. The inset shows the dust emission from the disk, which is seen edge-on. The "holes" in the dust map represent an enormous ringed cavity seen...

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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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