Thinking about Ursula Le Guin takes me to a single place. It is a snow-driven landscape, a glaciated world of constant winter called Gethen, whose name means 'winter' in the language of its people. I was reading The Left Hand of Darkness while snow pelted down outside one afternoon in upstate New York, waiting for my wife to get back from her teaching job, nursing a cup of tea and finding my mental location fusing with Le Guin's fascinating world. For The Left Hand of Darkness was a spectacular introduction to Le Guin. I had seen her name and even had, somewhere in the stacks, a copy of her first novel, Rocannon's World (1966), part of an Ace Double that I never got around to reading. The Left Hand of Darkness came out in 1969 but it was in the late 70's that I read it. I had been through "The Word for World is Forest" when reading Again, Dangerous Visions (1972), one of Harlan Ellison's anthologies, and although it won a Hugo Award in 1973, I hadn't found it as much compelling as...
M-Dwarf Planets: ExTrA and TRAPPIST-1
A new project called Exoplanets in Transits and their Atmospheres (ExTrA) has been set in motion at the European Southern Observatory’s site at La Silla (Chile). Funded by the European Research Council and the French Agence National de la Recherche, ExTrA’s three 0.6-metre telescopes will be operated remotely from Grenoble, France. This is an exoplanet transit effort centered around finding and characterizing Earth-sized planets orbiting M-dwarf stars. Not an easy task from the ground, as lead researcher Xavier Bonfils makes clear, though if you’re going to attempt it, northern Chile offers optimum conditions: “La Silla was selected as the home of the telescopes because of the site’s excellent atmospheric conditions. The kind of light we are observing — near-infrared — is very easily absorbed by Earth’s atmosphere, so we required the driest and darkest conditions possible. La Silla is a perfect match to our specifications.” To do its work, ExTrA weds spectroscopic information to...
Defining a Brown Dwarf / Planet Boundary
A paper that crossed my desk this morning proves timely in light of our recent discussions about brown dwarfs. Specifically, the question of when to declare an object a planet or a brown dwarf has come up, with the cutoff often cited at about 13 Jupiter masses. Now I see that Johns Hopkins’ Kevin Schlaufman is proposing a cutoff somewhere closer to 10 Jupiter masses, but the idea takes us beyond mass as the determinant of the object’s status. We tend to turn toward the IAU Working Group on Extrasolar Planets for our ideas on the planet/brown dwarf distinction, though the fact that we can find objects with 10 times Jupiter’s mass both in orbit around stars and also in isolation makes the definition a challenging one. The IAU has defined a planet as an object with a mass below the limiting mass for deuterium fusion that orbits a star or stellar remnant. Objects above this limiting mass have been defined as brown dwarfs, no matter how they formed or where they are located. This is where...
Planet Mimicry: Disk Patterns in Infant Systems
The wrong initial assumption can easily lead anyone down a blind alley. The problem comes across loud and clear in new work from Marc Kuchner (NASA GSFC) and colleagues, which Kuchner presented at the recent meeting of the American Astronomical Society in Washington. At issue is the matter of the disks of gas and dust around young stars, in many of which we can find patterns such as rings, arcs and spirals that suggest the formation of planets. But are such patterns sure indicators or merely suggestions? Kuchner's team has been looking at the question for several years now, presenting in a 2013 paper the possibility that a phenomenon called photoelectric instability (PeI) can explain the narrow rings we see in some disk systems. PeI happens when high-energy ultraviolet light strikes dust and ice grains, stripping away electrons. The electrons then strike and heat gas in the disk, causing gas pressure to increase and more dust to be trapped. Rings can form that begin to oscillate,...
K2-138: Multi-Planet System via Crowdsourcing
As Centauri Dreams readers know, I always keep an eye on the K2 mission, the rejuvenated Kepler effort to find exoplanets with a spacecraft that had originally examined 145,000 stars in Cygnus and Lyra. Now working with different fields of view, K2 has examined a surprisingly large number of stars, some 287,309, according to this Caltech news release. Digging around a bit, I discovered that each 80-day campaign brings in data on anywhere from 13,000 to 28,000 targets, all released to the public within three months of the end of the campaign. In the paper we'll discuss today, this influx is referred to as a 'deluge of data.' Our datasets just continue to grow in a time of exploration that seems unprecedented in scientific history. I've heard it compared to the explosion in knowledge of microorganisms after their detection by van Leeuwenhoek in the 17th Century, though of course it also conjures up thoughts of early exploratory voyages as humans pushed into hitherto unknown terrain....
New Titan Findings from Topographical Map
Cassini's huge dataset will yield discoveries for many years, as witness the global topographical map of Titan that has been assembled by Cornell University astronomers. The map draws on topographical data of the moon from multiple sources by way of studying its terrain and the flow of its surface liquids. Bear in mind that only 9 percent of Titan has been observed at relatively high resolution, and another 25-30 percent at lower resolution. For the remainder, the team mapped the surface using an interpolation algorithm and a global minimization process described in the first of two papers in Geophysical Review Letters. The methods are complex and described in detail in the paper. For our purposes, let's look at the result: We present updated topographic and spherical harmonic maps of Titan making use of the complete Cassini RADAR data set for use by the scientific community. These maps improve on previous efforts (Lorenz et al., 2013; Mitri et al., 2014) through their increased...
Substellar Objects in Orion
Although I carry on about upcoming observatories on the ground and in space, I never want to ignore the continuing contribution of the Hubble telescope to our understanding of planet and star formation. As witness the latest deep survey made by team lead Massimo Robberto (Space Telescope Institute) and colleagues, which used the instrument to study small, faint objects in the Orion Nebula. At a relatively close 1,350 light years from Sol, the nebula is something of a proving ground for star formation, and now one that is yielding data on small stars indeed. Identifying some 1,200 candidate reddish stars, the survey tapped Hubble's infrared capabilities to extract 17 candidate brown dwarf companions to red dwarf stars, one brown dwarf pair and one brown dwarf with a planetary companion. We also learn that a planetary mass companion to a red dwarf has turned up as well as, interestingly enough, a planet-mass companion to another planet, the duo orbiting each other in the absence of a...
Pulsar Navigation: Mining Our Datasets
Science fiction dealt with interstellar navigation issues early on. In fact, Clément Vidal's new paper, discussed in these pages yesterday, notes a George O. Smith story called "Troubled Star," which originally ran in a 1953 issue of Startling Stories and later emerged as a novel (Avalon Books, 1957). Smith is best remembered for a series of stories collected under the title Venus Equilateral, but the otherwise forgettable Troubled Star taps into the idea of using an interstellar navigation network, one that might include our own Sun. The story includes this bit of dialogue between human and the alien being Scyth Radnor, the latter explaining why his civilization would like to turn our Sun into a variable star: "We use the three-day variable to denote the galactic travel lanes. Very effective. We use the longer variable types for other things - dangerous places like cloud-drifts, or a dead sun that might be as deadly to a spacecraft as a shoal is to a seagoing vessel. It's all...
Pulsar Navigation: Exploring an ETI Hypothesis
Pulsar navigation may be our solution to getting around not just the Solar System but the regions beyond it. For millisecond pulsars, a subset of the pulsar population, seem to offer positioning, navigation, and timing data, enabling autonomous navigation for any spacecraft that can properly receive and interpret their signals. The news that NASA's SEXTANT experiment has proven successful gives weight to the idea. Station Explorer for X-ray Timing and Navigation Technology is all about developing X-ray navigation for future interplanetary travel. At work here is NICER -- Neutron-star Interior Composition Explorer -- which has been deployed on the International Space Station since June as an external payload. NICER deploys 52 X-ray telescopes and silicon-drift detectors in the detection of the pulsing neutron stars called pulsars. Radiation from their magnetic fields sweeps the sky in ways that can be useful. A recent demonstration used four millisecond pulsar targets —...
SETI and Astrobiology: Toward a Unified Strategy
Will we recognize life if and when we find it elsewhere in the cosmos? It's a challenging question because we have only the example of life on our own world to work with. Fred Hoyle's The Black Cloud raised the question back in 1957, a great memory for me because this was one of the earlier science fiction novels that I ever read. I remember sitting there with it in my 5th grade class in St. Louis, Missouri, having been loaned the paperback that had begun to circulate among my fellow students. I was mesmerized by the account of life as I had never imagined it. Hoyle, you'll recall, creates a vast cloud of gas and dust that turns out to be a kind of super-organism, and I leave the rest of this tale to those fortunate enough to be coming to it for the first time. But we've had the same conversation about Robert Forward's 'Cheela' recently, living as they do on the surface of a neutron star. The question is one Jacob Bronowski circulated widely through his televised series The Ascent of...
PicSat: Eye on Beta Pictoris
To understand why Beta Pictoris is receiving so much attention among astronomers, particularly those specializing in exoplanets, you have only to consider a few parameters. This is a young star, perhaps 25 million years old, one with a well observed circumstellar disk, the first actually imaged around another star. We not only have a large gas giant in orbit here, but also evidence of cometary activity as seen in spectral data. ? Pic is also relatively nearby at 64 light years. Image: This composite image represents the close environment of Beta Pictoris as seen in near infrared light. This very faint environment is revealed after a careful subtraction of the much brighter stellar halo. The outer part of the image shows the reflected light on the dust disc, as observed in 1996 with the ADONIS instrument on ESO's 3.6 m telescope; the inner part is the innermost part of the system, as seen at 3.6 microns with NACO on the Very Large Telescope. The newly detected source is more than 1000...
Exploring Origins of a Fast Radio Burst
Fast Radio Bursts (FRBs) continue to intrigue us given their energy levels. You may recall FRB 121102, which was revealed at a press conference almost exactly one year ago to be located in a radio galaxy some 3 billion light years away. This is a repeating FRB (the only repeating source yet found), making its study an imperative as we try to characterize the phenomenon. With data from Arecibo, the Very Large Array and the European VLBI network, astronomers determined its position to within a fraction of an arcsecond, where a source of weak radio emission is also traced. Today, drawing on new observations from Arecibo and the Green Bank instrument in West Virginia, we learn something about the source of these bursts. The energies we are talking about are obviously titanic. Given the distance between the source and us, researchers have calculated that each burst throws as much energy in a single millisecond as our Sun releases in an entire day. And as we learn in the latest issue of...
Exoplanet Prospects at Earth-based Observatories
Although I often write about upcoming space missions that will advance exoplanet research, we're also seeing a good deal of progress in Earth-based installations. In the Atacama Desert of northern Chile, the Extremely Large Telescope is under construction, with first light planned for 2024. With 256 times the light gathering area of the Hubble instrument, the ELT is clearly going to be a factor in not just exoplanet work but our studies of numerous other astronomical phenomena, from the earliest galaxies in the cosmos to the question of dark energy. Today we learn that the first six hexagonal segments for the ELT's main mirror have been cast by the German company SCHOTT at their facility in Mainz, Germany. We're just at the beginning of the process here, for the primary mirror is to be, at 39 meters, the largest ever made for an optical-infrared telescope. 798 individual segments -- each 1.4 meters across and 5 centimeters thick -- will go into it, working together as a single...
Tightening the Focus on Brown Dwarfs
Among the many indicators that we have much to learn about brown dwarfs is the fact that we don't yet know how frequently they form. Recent work from Koraljka Muzic (University of Lisbon) and colleagues has pointed, however, to quite a robust galactic population (see How Many Brown Dwarfs in the Milky Way?). Working with observations at the Very Large Telescope, the study pegged the brown dwarf population at 25 billion, with a potential of as many as 100 billion. Image: Stellar cluster NGC 1333 is home to a large number of brown dwarfs. Astronomers will use Webb's powerful infrared instruments to learn more about these dim cousins to the cluster's bright newborn stars. Credit: NASA/CXC/JPL. Likewise in need of further data is our understanding of how brown dwarfs form, especially in the region where planet and star overlap. Recall that brown dwarfs are not main sequence stars, as they are not massive enough to ignite hydrogen fusion, even if deuterium and lithium fusion may occur. If...
2017 from an Interstellar Perspective
The recent burst of interest in interstellar flight has surely been enhanced by the exoplanet discoveries that have become almost daily news. Finding interesting planets, some of them with the potential for water on their surfaces, inevitably raises the question of how we might find a way to get there. We can only imagine this accelerating as missions like the Transiting Exoplanet Survey Satellite (TESS) and the James Webb Space Telescope begin to fill in not just our inventory of nearby planets but our understanding of their compositions. Find a terrestrial class planet around another star -- we may find that there is more than one around the Alpha Centauri stars -- and the interstellar probe again becomes a topic of lively conversation. Breakthrough Starshot, the hugely ambitious attempt to develop a concept for tiny payloads being delivered through beamed laser propulsion to a nearby star, is by now a major part of the discussion. And as I said in my closing remarks at the recent...
3200 Phaethon: Arecibo Back at Work
With the holidays behind us (alas), I want to be sure to cover the Arecibo observations of asteroid 3200 Phaethon, not only for their intrinsic interest but as a nod to the restoration of operations at the Puerto Rico observatory. We are fortunate indeed that the structural damage Arecibo suffered on September 20 because of hurricane Maria was relatively minor. Radio astronomy work was back in progress within days of the storm, though it took until early December before commercial power was restored and radar work could resume. If you're interested in radar astronomy, have a look at Alessondra Springmann's How Radar Really Works: The Steps Involved Before Getting an Image, which is available via The Planetary Society. Springmann offers a detailed overview of radar operations with a splash of humor: Arecibo Observatory is known for its 305-meter (1000-foot) diameter telescope and its appearances in Goldeneye and Contact. Aside from battling Bond villains and driving red diesel Jeeps...
KIC 8462852: A Dusty Solution?
Research into Boyajian's Star, otherwise known as KIC 8462852 or 'Tabby's Star,' has continued in robust fashion even as many of us were distracted by that other curiosity with a faint SETI potential, the interstellar asteroid `Oumuamua. In both cases, a highly interesting object provoked speculation as to its origins, with Boyajian's Star getting the lion's share of attention because the unusual dips in its lightcurve proved hard to explain. Now a team of more than 200 researchers led by Tabetha Boyajian herself is drawing useful conclusions about the star. Also on the team is Penn State's Jason Wright, whose interest in possible SETI signatures led him to point out that engineering on a vast scale could not immediately be ruled out. The paper now being made available in The Astrophysical Journal Letters shows that the star dims more at some wavelengths than at others. And that is, to say the least, problematic for the idea that an artificial megastructure orbits Boyajian's Star....
The Plasma Magnet Drive: A Simple, Cheap Drive for the Solar System and Beyond
Can we use the outflow of particles from the Sun to drive spacecraft, helping us build the Solar System infrastructure we'll one day use as the base for deeper journeys into the cosmos? Jeff Greason, chairman of the board of the Tau Zero Foundation, presented his take on the idea at the recent Tennessee Valley Interstellar Workshop. The concept captured the attention of Centauri Dreams regular Alex Tolley, who here analyzes the notion, explains its differences from the conventional magnetic sail, and explores the implications of its development. Alex is co-author (with Brian McConnell) of A Design for a Reusable Water-Based Spacecraft Known as the Spacecoach (Springer, 2016), focusing on a new technology for Solar System expansion. A lecturer in biology at the University of California, he now takes us into a different propulsion strategy, one that could be an enabler for human missions near and far. by Alex Tolley Suppose I told you that a device you could make yourself would be a...
Solar System Formation near a Massive Star
An unusual type of star may be showing us something about the origin of our own Solar System. Wolf-Rayet stars display unusual spectra, prominent in which are heavy elements as well as broad emission lines of ionized helium, nitrogen and carbon. These are massive objects 40 to 50 times the size of our Sun, with surface temperatures ranging up to 200,000 K. Have a look at one of these, showing another Wolf-Rayet trait, the strong stellar winds ejecting material into nearby space. A bubble with a dense shell forms around such stars, trapping gas and dust that could form into new stars. Image: Here we see the spectacular cosmic pairing of the star Hen 2-427 — more commonly known as WR 124 — and the nebula M1-67 which surrounds it. Both objects, captured here by the NASA/ESA Hubble Space Telescope, are found in the constellation of Sagittarius and lie 15,000 light-years away. The star Hen 2-427 shines brightly at the very centre of this explosive image and around the hot...
Dragonfly: Contemplating a Return to Titan
Our continuing interest in Titan as a possible venue for life was energized last year with the publication of a paper by Martin Rahm and Jonathan Lunine, working with colleagues David Usher and David Shalloway (all at Cornell University). I've written about this one before (see Prebiotic Chemistry on Titan?) and won't revisit the details, but the gist is that hydrogen cyanide produced in Titan's atmosphere can condense into aerosols that are transformed into interesting polymers on the surface. Of these, the most intriguing seems to be polyimine. The authors see polyimine as capable of producing complex, ordered structures that absorb light, producing energy that can be used to catalyze prebiotic chemistry. Rather than looking in Titan's seas, the authors think we'll find hydrogen cyanide reactions in tidal pools on the shores near seas and lakes. It's an interesting proposition, and like so many notions about Titan, it requires us to get a payload back to the surface, as we did in...