Paul Gilster | Centauri Dreams

Was the Wow! Signal Due to Power Beaming Leakage?

by Paul Gilster | Jan 22, 2021 | Administrative | 62 Comments

The Wow! signal has a storied history in the SETI community, a one-off detection at the Ohio State 'Big Ear' observatory in 1977 that Jim Benford, among others, considers the most interesting candidate signal ever received. A plasma physicist and CEO of Microwave Sciences, Benford returns to Centauri Dreams today with a closer look at the signal and its striking characteristics, which admit to a variety of explanations, though only one that the author believes fits all the parameters. A second reception of the Wow! might tell us a great deal, but is such an event likely? So far all repeat observations have failed and, as Benford points out, there may be reason to assume they must. The essay below is a shorter version of the paper Jim has submitted to Astrobiology. by James Benford In 1977 the Big Ear radio telescope (Ohio State University Radio Telescope) recorded the famous Wow! Signal, which is the most serious contender for artificial interstellar radiation. It is called the...

Propulsion for Satellite ‘Constellations’

by Paul Gilster | Jan 21, 2021 | Advanced Rocketry | 15 Comments

A French company called Exotrail has been working on electric propulsion systems for small spacecraft down to the CubeSat level. As presented last week at the 13th European Space Conference in Brussels, the ExoMG Hall-effect electric propulsion system was flown in a demonstration orbital mission in November, launched to low-Earth orbit by a PSLV (Polar Satellite Launch Vehicle) rocket. A brief nod to the PSLV: These launch vehicles were developed by the Indian Space Research Organisation (ISRO), and are being used for rideshare launch services for small satellites. Among their most notable payloads have been the Indian lunar probe Chandrayaan-1, and the Mars Orbiter Mission called Mangalyaan. Hall-effect thrusters (HET) trap electrons emitted by a cathode in a magnetic field, ionizing a propellant to create a plasma that can be accelerated via an electric field. The technology has been in use in large satellites for many years because of its high thrust-to-power ratio. What catches...

TOI-1259A: Implications of a White Dwarf Companion

by Paul Gilster | Jan 19, 2021 | Exoplanetary Science | 11 Comments

TESS, our Transiting Exoplanet Survey Satellite, continues to roll up interesting planet candidates, with over 2450 TESS Objects of Interest (TOI) thus far identified. The one that catches my eye this morning showed up in the lightcurve of TOI-1259A, a K-dwarf some 385 light years away. The planet designated TOI-1259Ab is Jupiter-sized but some 56 percent less massive, with a 3.48 day orbit at 0.04 AU, and an equilibrium temperature of 963 K. This system gets interesting, though, not so much for the planet but the other star, a white dwarf (TOI-1259B) in a wide orbit at 1648 AU from the K-dwarf. A team of astronomers led by David Martin (Ohio State University) finds an effective temperature of 6300 K, a radius of 0.013 solar radii and a mass of 0.56 solar masses, a set of characteristics that allow the team to estimate that the system is just over 4 billion years old. Image: SDSS image of the planet host TOI-1259A and its bound white dwarf companion TOI-1259B. Credit: Martin et al.,...

Recovering a Triple Star Planet with New Data

by Paul Gilster | Jan 18, 2021 | Exoplanetary Science | 4 Comments

The Kepler mission produced so much data -- 2394 exoplanets, 2366 candidates by the end of spacecraft operations in 2018 -- that we might forget how quickly all this came about. The first Kepler results started being announced in 2010. One of these, the second candidate to emerge, was KOI-5Ab, which was a tough pick in the early going given its position within a triple star system. An ambiguous detection, it was soon left behind, its status uncertain, as the numbers of more definitive candidates swelled. Caltech's David Ciardi, who discussed this elusive system at the recent virtual meeting of the American Astronomical Society, says this about it: "KOI-5Ab got abandoned because it was complicated, and we had thousands of candidates. There were easier pickings than KOI-5Ab, and we were learning something new from Kepler every day, so that KOI-5 was mostly forgotten." Ciardi, who is chief scientist at NASA's Exoplanet Science Institute, has now pulled KOI-5Ab back to vibrant life....

Across the Brown Dwarf Palette

by Paul Gilster | Jan 14, 2021 | Deep Sky Astronomy & Telescopes | 44 Comments

Something to note about the brown dwarfs we looked at yesterday: Our views on how they would appear to someone nearby in visible light are changing. It’s an interesting issue because these brown dwarfs exist in more than a single type. If you’ll have a look at the image below, you’ll see a NASA artist conception of the three classes of brown dwarf, all of these being objects that lack the mass to burn with sustained fusion. Image: This artist's conception illustrates what brown dwarfs of different types might look like to a hypothetical interstellar traveler who has flown a spaceship to each one. Brown dwarfs are like stars, but they aren't massive enough to fuse atoms steadily and shine with starlight -- as our sun does so well. Our thoughts on how these objects appear are evolving quickly, as witness yesterday’s discussion, and we’re likely to need another visual rendering of brown dwarf classes soon. Credit: NASA/JPL-Caltech. One thing should jump out to anyone who read...

What Does the Closest Brown Dwarf Look Like?

by Paul Gilster | Jan 13, 2021 | Deep Sky Astronomy & Telescopes | 13 Comments

I keep hoping we'll find a brown dwarf closer to us than Alpha Centauri, but none have turned up yet despite the best efforts of missions like WISE (Wide-Field Infrared Survey Explorer). If there's something out there, it's dim indeed. Of course, I wouldn't be surprised at finding rogue planets between us and the nearest stars. Maybe some will be more massive than Jupiter, but evidently not massive enough to throw an infrared signature of the sort that defines a brown dwarf. Just what lies outside our system's edge always makes for interesting speculation. The beauty of finding an actual brown dwarf as opposed to a rogue planet is that we might be dealing with a planetary system in miniature, a fine target in our own backyards. Lacking that, the closest brown dwarf we know is the Luhman 16 AB system, a binary in the southern constellation of Vela some 6.5 light years from the Sun (a little further than Barnard's Star, making this the third closest known system to the Sun). Here we...

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.

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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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