It's a long name, but with the successful arrival of the Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) lander on Mars, we now go to work on the planet's deep interior. With Centauri Dreams' deep space perspective, my thoughts quickly turn to other stellar systems. We've all seen how hard it is to land on Mars, and have looked up into the night sky to find the ruddy pinprick that marks its naked eye presence. Given our Solar System's scale, the task of getting humans to Mars looms as a major challenge. Image: Who can resist the first clear photo from a Mars mission? Not me. Credit: NASA. But suppose we were on a planet in the TRAPPIST-1 system. Here we have roughly Earth-sized planets packed into tight proximity around the parent red dwarf. TRAPPIST-1b is at 0.011 AU, while TRAPPIST-1c is at 0.015 AU. Even the most distant from the star, TRAPPIST-1h, orbits at 0.062 AU, so that these seven worlds are all closer to the host than Mercury in our...

Some relatives of a friend recently made me realize how routine exoplanet discoveries have become to the public. These are anything but astronomy buffs, but they know that planets can be found without ever being seen. My acquaintances may not understand radial velocity or transits to any high degree, but they accept that the methods are there and have proven reliable. "Someday," said one, "I guess we'll actually see one of these planets." The image below came as a surprise when I showed it to them. Here we do see a planetary system, four actual planets around the star HR 8799 and not just jiggles in Doppler signals or dips in a lightcurve. For me, what's astonishing here is not only that we can see planets despite their proximity to the host, but that we've accomplished this with telescopes on the ground. Adaptive optics -- correcting for turbulence in the atmosphere that would distort an astronomical image, using a guide star as a reference -- is the tool that is opening a new era...

Even today, I can well understand the reaction that Dennis Conti had when confronted with the prospect of finding a planet around another star with nothing more than an amateur instrument. Conti, who founded and now chairs the Exoplanet Section of the American Association of Variable Star Observers, was a newcomer to the transit method just a few years ago. "I thought, there's no way for someone with a backyard telescope to detect a planet going around a distant star," he says, looking back from the vantage of one now immersed in such observations. My boyhood 3-inch reflector was not a backyard instrument -- too many trees back there. So it became a front-yard telescope. Absent the technological innovations of the past five decades, I could only imagine vast instruments for studying objects around other stars. The transit method in exoplanet detection was a long way off, but the idea of seeing not a planet itself but a change in starlight as the planet crossed the face of its host...

The detection of a planet around Barnard’s Star really hits home for me. No, this isn’t a habitable world, but the whole topic of planets around this star has resonance for those of us who remember the earliest days of exoplanet study, which could be extended back to Peter van de Kamp’s work at Swarthmore’s Sproul Observatory in Pennsylvania. The astronomer thought he had found evidence for a 1.6 Jupiter mass planet in a 4.4 AU orbit there, based on what he interpreted as telltale wobbles in photographic plates of the star taken between 1916 and 1962. This work, ending in the early 1970s, turned out to be the result of errors in the instrument van de Kamp was using, but the buzz about possible planets around Barnard’s Star had been sufficient to create a small crest of enthusiasm for exoplanet studies in general. The British Interplanetary Society saw in Barnard’s Star a target worth investigating, and designed their Daedalus star probe around a mission there. In any case, van de...

When astronomers talk about metals, they're using the term in a specific sense. A metal in stellar terms is any element heavier than helium. Thus iron, silicon, magnesium and carbon qualify, all elements that are components of small, rocky planets. It was iron that John Michael Brewer (Yale University), Debra Fischer and colleagues singled out as a proxy in their recent work on the metal content of exoplanet systems. The work focuses specifically on compact, multi-planet systems as one of several system architectures found in close orbit of a host star. What's interesting here is that these domains seem mutually exclusive, or almost so. Unlike our Solar System, a system with multiple planets on tight orbits can squeeze its worlds into a region as close as Mercury. Likewise near the host star, we sometimes find massive planets in close orbits, known as 'hot Jupiters.' Few of these have close planetary neighbors, and few compact multi-planet systems have massive planets. And there is...

We’ve long been interested in how the Earth got its oceans, with possible purveyors being comets and asteroids. The idea trades on the numerous impacts that occurred particularly during the Late Heavy Bombardment some 4.1 to 3.8 billion years ago. Tuning up our understanding of water delivery is important not only for our view of our planet’s development but for its implications in exoplanet systems with a variety of different initial conditions. Image: This view of Earth’s horizon was taken by an Expedition 7 crewmember onboard the International Space Station, using a wide-angle lens while the Station was over the Pacific Ocean. Credit: NASA. But the picture becomes more complex when we compare regular hydrogen atoms (one proton, one electron) with ‘heavy hydrogen,’ or deuterium atoms. The latter have a neutron in addition to a proton in the nucleus. A recent paper in the Journal of Geophysical Research digs into isotope ratios, the ratio of deuterium to ordinary hydrogen atoms,...

The Kepler spacecraft has been with us long enough (it launched in 2009) and has revealed so much about the stars in our galaxy that its retirement -- Kepler lacks the fuel for further science operations -- is cause for reflection. The end of great missions always gives us pause as we consider their goals and their accomplishments, and offer up our gratitude to the many people who made the mission happen. Let's try to back up and see things in their totality. Image: An artist's conception of Kepler at work. Credit: NASA/Ames/Dan Rutter. Kepler's job was essentially statistical, an attempt to look at as many stars as possible in a particular field of stars, so that we could gain insights into the distribution of planets there, and thus deduce something about likely conditions galaxy-wide. We didn't know in 2009 that there was statistically at least one planet around every star, nor did we know just how diverse the worlds Kepler found, more than 2,600 of them, would be. Moreover,...

Earlier in the week I talked about Astronomy Rewind, an ambitious citizen science project dedicated to recovering old astronomical imagery and digitizing it for comparison with new data. Now I’ve learned that another citizen science effort, Planet Finders, is working with simulated data from the Transiting Exoplanet Survey Satellite (TESS), planning to transition into real TESS data as soon as they become available. Have a look at this effort here if you are interested in becoming a beta tester. TESS will be a hugely significant exoplanet mission particularly in terms of nearby stars, so becoming a part of this project should be an exciting venture indeed. On with today’s post, which I would have actually run yesterday if I had read the paper soon enough, as it offers insights into Wednesday’s entry on protoplanetary disks. As we’ve seen, these can become the discovery grounds for young planets. In the case of the 2-million year old CI Tau, that meant an already confirmed gas giant...

Given their ubiquity in the Milky Way, red dwarfs would seem to offer abundant opportunities for life to emerge. But we're a long way from knowing how habitable the planets that orbit them might be. While mechanisms for moderating the climate on tidally locked worlds in tight habitable zones continue to be discussed, the issue of flares looms large. That makes a new survey of 12 young red dwarfs, and the project behind it, of unusual interest in terms of astrobiology. What jumps out at the reader of Parke Loyd and team's paper is the superflare their work caught that dwarfed anything ever seen from our own Sun, a much larger star. It was enough to set Loyd, a postdoctoral researcher at Arizona State University, back on his heels. "When I realized the sheer amount of light the superflare emitted, I sat looking at my computer screen for quite some time just thinking, 'Whoa.'" He adds: "With the Sun, we have a hundred years of good observations. And in that time, we've seen one, maybe...

We’ve never found a ‘hot Jupiter’ around a star as young as CI Tau. This well studied system, some 2 million years old, has drawn attention for its massive disk of dust and gas, one that extends hundreds of AU from the star. But radial velocity examination recently revealed CI Tau b, a hot Jupiter that in and of itself raises questions. Couple that to the likelihood of three other gas giant planets emerging in the disk with extreme differences in orbital radii and it’s clear that CI Tau challenges our ideas of how gas giants, especially hot Jupiters, emerge and evolve. Can a hot Jupiter form in place, or is migration from a much more distant orbit the likely explanation? The latter seems likely, and in that case, what was the mechanism here around such a young star? Most hot Jupiter host stars have lost their protoplanetary disks, which means that astronomers have been working with theoretical formation models to produce the observed tight orbits. And because about 1 percent of main...

It was back in 2012 that Eric Mamajek (University of Rochester) and team discovered a possible ring system around the star J1407 in lightcurves originally taken in 2007, spawning subsequent work with Leiden Observatory's Matthew Kenworthy. And what a ring system it would be if confirmed. The diameter, based on the lightcurve, would be nearly 120 million kilometers. This would be a ring system nearly 200 times larger than the rings of Saturn, one containing an Earth's mass of dust particles, and in early studies, one housing over thirty separate rings. Image: Artist's conception of the extrasolar ring system circling the young giant planet or brown dwarf J1407b. The rings are shown eclipsing the young sun-like star J1407, as they would have appeared in early 2007. Credit: Ron Miller. The possible J1407 ring system provides a nice segue from yesterday's post on recovering astronomical images from a century's worth of scientific journals, as Centauri Dreams reader Andrew Tribick was...

8,000 light years from Earth in the constellation Cygnus, the star designated Kepler 1625 may be harboring a planet with a moon. The planet, Kepler 1625b, is a gas giant several times the mass of Jupiter. What David Kipping (Columbia University) and graduate student Alex Teachey have found is compelling though not definitive evidence of a moon orbiting the confirmed planet. If we do indeed have a moon here, and upcoming work should be able to resolve the question, we are dealing, at least in part, with the intriguing scenario many scientists (and science fiction writers) have speculated about. Although a gas giant, Kepler 1625b orbits close to or within the habitable zone of its star. A large, rocky moon around it could be a venue for life, but the moon posited for this planet doesn't qualify. It's quite large -- roughly the size of Neptune -- and like its putative parent, a gaseous body. If we can confirm the first exomoon, we'll have made a major advance, but the quest for...

I like nautical metaphors as applied to the stars, my favorite being the words attributed to Antoine de Saint-Exupéry, French writer/aviator and author of poetic works about flight like Wind, Sand and Stars (1939), and a work familiar to most American students of French, Vol de nuit, published in English as Night Flight (1931). I think the Saint-Exupéry quote captures what it takes to contemplate far voyaging: "If you want to build a ship, don't drum up the men to gather wood, divide the work and give orders. Instead, teach them to yearn for the vast and endless sea." Image: Antoine de Saint-Exupery, whose work inspired, among many other things, my own decision to take up flying. I had to track down the quote because the last time it appeared in these pages, a reader wrote to tell me he had never found it in Saint-Exupéry. I hadn't either, which bothered me because I am a huge fan of the man's work. It certainly sounded like him. So I did some digging and turned...

Proxima Centauri b is back in the news, although I'll confess that in my case, it's rarely out of my thoughts -- I've been obsessed with the Alpha Centauri system since my youth. The latest comes through work by Anthony Del Genio and colleagues (NASA GSFC), who describe in Astrobiology their new simulations with regard to potential habitability. You'll recall the issues here. A planet this close to its host star may well be tidally locked, with one side always facing the M-dwarf Proxima Centauri. Martin Turbet (Sorbonne Universités, Paris) and colleagues described possible climates on Proxima b in a 2016 paper, using a 3D climate model (GCM) to simulate the atmosphere and water cycle of the planet for its two possible rotation modes, a 1:1 and a 3:2 spin resonance (in other words, gravitational forces could keep Centauri b locked to Proxima or rotating 3 times for every 2 orbits of the star). The Solar System offers analogues: The Moon is in a 1:1 spin resonance with the...

Thinking about supplying a young planet with water, the mind naturally heads for the outer reaches of the Solar System. After all, beyond the 'snowline,' where temperatures are cold enough to allow water to condense into ice grains, volatiles are abundant (this also takes in methane, ammonia and carbon dioxide, all of which can condense into ice grains). The idea that comets or water-rich asteroids bumping around in a chaotic early Solar System could deliver the water Earth needed for its oceans makes sense, given our planet's formation well inside the snowline. We've just looked at Ceres, in celebration of the Dawn mission's achievements there, and we know that Ceres has an icy mantle and perhaps even an ocean beneath its surface. At 2.7 AU, the dwarf planet is right on the edge of traditional estimates for the snowline as it would have occurred in the early days of planet formation. Obviously, the snowline has a great deal to do with various models about the accretion of solid...

Not long ago, Ramses Ramirez (Earth-Life Science Institute, Tokyo) described his latest work on habitable zones to Centauri Dreams readers. Our own Alex Tolley (University of California) now focuses on Dr. Ramirez' quest for 'a more comprehensive habitable zone,' examining classical notions of worlds that could support life, how they have changed over time, and how we can broaden current models. We can see ways, for example, to extend the range of habitable zones at both their outer and inner edges. A look at our assumptions and the dangers implicit in the term 'Earth-like' should give us caution as we interpret the new exoplanet detections coming soon through space- and ground-based instruments. by Alex Tolley The Plains of Tartarus - Bruce Pennington In 1993, before we had detected any exoplanets, James Kasting, Daniel Whitmire, and Ray Reynolds published a modeled estimate of the habitable zone in our solar system [1]. They stated: "A one-dimensional climate model is used to...

Who among us hasn't speculated about the ultimate fate of the Solar System? The thought of our Sun growing into a vast red giant has preoccupied writers and readers since the days when H. G. Wells so memorably captured a far future scene through the eyes of his Time Traveler. And what a scene that was: "I cannot convey the sense of abominable desolation that hung over the world. The red eastern sky, the northward blackness, the salt dead sea, the stony beach crawling with these foul, slow-stirring monsters, the uniform poisonous-looking green of the lichenous plants, the thin air that hurts one's lungs: all contributed to an appalling effect. I moved on a hundred years, and there was the same red sun—a little larger, a little duller—the same dying sea, the same chill air, and the same crowd of earthy crustacea creeping in and out among the green weed and the red rocks. And in the westward sky, I saw a curved pale line like a vast new moon." Wells was working on a...

We've recently looked at gas giant planet formation, and specifically the stages in which Jupiter seems to have formed -- this is the work of Thomas Kruijer (University of Münster) and colleagues as summarized in A Three Part Model for Jupiter's Formation. Whether or not the details of Kruijer and team's model are correct, it seems evident that gas giants must form quickly, based on current theories. These involve the formation of a large solid core, with gas accretion building up a thick atmosphere at a time when the disk around the parent star is still rich in materials. In this thinking, planets like the Earth come along much later than the gas giants that are the first to form. Get a few million years into the evolution of a stellar system and there should be evidence of a gas giant, if one is going to form, but terrestrial worlds can take up to 100 million years to emerge. This has captured the interest of Nader Haghighipour (University of Hawaii), whose work was presented at...

One of the memorable things about 1995 (and this was also the year of the first detection of an exoplanet around a main sequence star) was the release of the Galileo spacecraft's descent probe. Dive into that howling maelstrom, it would seem, and instant obliteration should follow. But the probe had been designed with a heavy duty heat shield to protect it during its journey. It kept transmitting after scorching its way into Jupiter's atmosphere at 47 kilometers per second, 30 km/sec faster than Voyager 1. The probe returned data for fully 58 minutes before its demise. Here's how two science fiction novelists handle a descent into the Jovian clouds: Slowly, the fine fretwork of the ammonia cirrus clouds above him became obscured by brown and salmon layers of intervening chemistry, the air stained a nicotine-coloured haze of complex carbon molecules. Soon it was warmer than a summer's day out there, and already the gondola was enduring more than ten atmospheres of pressure, the...

How close would a passing star have to come to produce drastic results on the outer Solar System? According to researchers at the Max Planck Institute for Radio Astronomy in Bonn, roughly 3 times Neptune's distance would be disruptive enough to explain what we see beyond that planet's orbit today. Led by Susanne Pfalzner, the scientists have been modeling close stellar flybys of other planetary systems for years, but have only recently turned their attention to the eccentricities of our own system, where conditions beyond Neptune pose questions. Image: Artist's concept of a stellar system in the making with a protoplanetary disk surrounding a young star. Credit: NASA JPL-Caltech. A look at the Solar System's formation highlights the problematic nature of the process. Out to the orbit of Neptune, planets, dwarf planets and asteroids orbit with only small differences in orbital inclination, indicative of the flatness of the original disk from which all these objects drew their birth...