At this point in the exoplanet hunt, actual images of our quarry are uncommon, but few more so than today's image, made with the European Southern Observatory's Very Large Telescope. This is being billed as the first image ever taken of a young Sun-like star accompanied by multiple planets, in this case two gas giants. And I do mean young: At 17 million years old, this star has spawned planets recently enough that their hot glow makes the image possible. Image: First ever image of a multi-planet system around a Sun-like star. The arrows point to the planets; the other bright objects are background stars. Credit: European Southern Observatory. Designated TYC 8998-760-1, the host star is some 300 light years away in the southern constellation of Musca (The Fly), with a mass close to that of the Sun, described in the paper on this work as a solar analogue. The two gas giants orbit the star at 160 and 320 AU, and both are more massive than our Jupiter and Saturn, with the inner planet at...

It was hard enough to find ‘Oumuamua, the first object on an interstellar trajectory discovered within our own Solar System. The emergence of new resources like the Large Synoptic Survey Telescope (LSST) should help us develop a preliminary catalog of such interlopers, thought to be not uncommon if we can identify them. But tracking down objects that wandered from one star to another and found their way into residence in our system is another matter entirely. In April we looked at a study of an unusual set of Centaurs, asteroids whose orbit perpendicular to the orbital plane of the planets and other asteroids raises questions about their origin. A letter to Monthly Notices of the Royal Astronomical Society had appeared, written by Fathi Namouni (Observatoire de la Côte d’Azur, France) and Maria Helena Moreira Morais (Universidade Estadual Paulista, Brazil). The scientists identified what seems to be a population of asteroids that were probably drawn into the Sun’s gravitational pull...

In addition to being a rather well-known character on television, SPOCK also stands for something else, a software model its creators label Stability of Planetary Orbital Configurations Klassifier. SPOCK is handy computer code indeed, determining the long-term stability of planetary configurations at a pace some 100,000 times faster than any previous method. Thus machine learning continues to set a fast pace in assisting our research into exoplanets. At the heart of the process is the need to figure out how planetary systems are organized. After all, after the initial carnage of early impacts, migration and possible ejection from a stellar system, a planet generally settles into an orbital configuration that will keep it stable for billions of years. SPOCK is all about quickly screening out those configurations that might lead to collisions, which means working out the motions of multiple interacting planets over vast timeframes. To say this is computationally demanding is to greatly...

I hadn’t planned to write about the recent work out of the University of Exeter on Beta Pictoris, but yesterday’s article on KELT-9b dealt with planetary alignment, given that the planet shows marked spin-orbit misalignment. At Beta Pictoris, an international team of researchers led by Exeter’s Stefan Kraus has carried out measurements of the spin-orbit alignment of Beta Pictoris b, a gas giant orbiting a young star in an orbit about as distant as Saturn from the Sun. Here we have the first spin-orbit alignment measurement of a directly imaged planetary system. How such alignments occur is clearly relevant to planet formation theories. There’s a bit of astronomy history here, for spin-orbit issues became significant for both Immanuel Kant (1724-1804) and Pierre-Simon Laplace (1749-1827), who looked at spin-orbit alignment in our own Solar System. It was apparent to both that the planets known to them orbited the Sun not only in alignment with each other but in alignment with the...

Perhaps the hottest planet ever discovered spotlights yet another way to interpret light curves produced by transiting worlds. KELT-9b comes out of data gathered by the KELT transit survey, the acronym standing for Kilodegree Extremely Little Telescope. KELT consists of two robotic telescopes, one at Winer Observatory in southeastern Arizona, the other at the South African Astronomical Observatory in Sutherland, South Africa. The planet orbits an A-class star in Cygnus about 670 light years away and turned up in the KELT data in 2017. We’ve learned a lot more about KELT-9b thanks to the TESS mission, allowing us to understand just how unusual this planet is. 2.9 times as massive as Jupiter, the world orbits its star in 36 hours, receiving 44,000 times the energy from its host that Earth receives from the Sun. Reaching 4,300 degrees Celsius, this is a tidally locked planet whose dayside is hotter than the surfaces of some stars. Its orbital path takes it almost directly above both the...

In exoplanet research, 'deserts' are regions where things are not found. Thus the Neptunian Desert, which is a zone close to a star where planets of Neptune size only rarely appear. Deserts like this (there is also a Brown Dwarf Desert that we've examined in earlier posts) raise questions because we don't know why they occur. What is it we don't understand about planet formation that accounts for the lack of Neptune-mass planets in 2-4 day orbits? Exceptions tweak our thinking, and do have NGTS-4b, a world 20 percent smaller than Neptune and 20 times as massive as Earth in a 1.3-day orbit around a K-dwarf (see Into the Neptunian Desert for more on this one, which is now joined by an even more puzzling object). For today we learn of the discovery of a world of roughly Neptune's mass with an orbital period of a scant 18 hours, and researchers reporting the discovery in Nature suggest that we are actually looking at a 'failed' gas giant, an exposed planetary core. We can thank TESS...

Ramses Ramirez, whose work on what he calls the Complex Life Habitable Zone was the subject of a recent Alex Tolley essay (see Are Classic Habitable Zones Too Wide for Complex Life?), joins us today with a look back at Rare Earth on the occasion of the book's 20th anniversary. Written by Peter Ward and Donald Brownlee, Rare Earth examined a wide range of factors that argued against the ubiquity of complex life in the cosmos. I remember well when it came out, as I was in the midst of writing my Centauri Dreams book for Copernicus, Ward and Brownlee's publisher, and my editor (the brilliant Paul Farrell) and I had to wrestle with the question of whether Rare Earth rendered the search for intelligent life elsewhere irrelevant. Fortunately, we plunged ahead anyway. As Dr. Ramirez shows this morning, many of the factors put forward by Ward and Brownlee can be re-examined with new data as work on exoplanets continues. Ramses is a research scientist at the Earth-Life Science Institute...

The planet candidate KOI-456.04 strikes me as significant not so much because of the similarity of its orbit with that of Earth (a 378 day orbital period around a star much like the Sun), but because of the methods used to identify its possible presence. Make no mistake, this is still very much a planet candidate, as co-authors René Heller and Michael Hippke are at pains to explain, noting that systematic measurement errors cannot be ruled out, though they estimate an 85 percent likelihood that it is there. We don’t have many examples of small planets potentially in the habitable zone of a star like ours, and this is what has received the most media attention. So let’s look at this aspect of the story quickly, because I want to move past it. If this candidate is confirmed, it looks to be less than twice the radius of the Earth, receiving about 93 percent of Earth’s insolation from its star. Make assumptions about its atmosphere and you can arrive at a surface temperature averaging...

Selection is going to be a key issue for future ground- and space-based observatories. Given lengthy observing times for targets of high interest, we have to know how to cull from our exoplanet catalog those specific worlds that can tell us the most about life in the universe. Recently, Ramses Ramirez (Earth-Life Science Institute, Tokyo Institute of Technology) went to work on the question of habitable zones for complex life, which are narrower than the classic habitable zone defined by the potential for water on the surface. In today's essay, Alex Tolley looks at Ramirez' recent paper, which examines the question in relation to the solubility of gases in lipid membranes. What emerges in this work is a constrained habitable zone suited to complex life, with limits Alex explores. The model has interesting ramifications right here in the Solar System, but it also points the way toward constraining the list of planets upon which we'll apply our emerging tools for atmospheric...

55 Cancri e is a confirmed planet, and thus a departure from our topic of the last two days, which was the act of exoplanet confirmation as regards Proxima Centauri b and c, the latter still in need of further work before it can be considered confirmed. But 55 Cancri e has its uses in offering a tight orbit around a Sun-like star that can be detected using the transit method. That was just what was needed for ASTERIA (Arcsecond Space Telescope Enabling Research in Astrophysics), a technology demonstration mission involving a tiny CubeSat. Sara Seager (MIT) has been at the heart of the investigation of CubeSats as exoplanet research platforms. I think the idea is brilliant. If we want to mount the most effective search of nearby Sun-like stars for Earth analogs, multiple telescopes must be in use. CubeSats are cheap. Why not launch a fleet of them, each with the task of monitoring a single star at a time. Launched in 2017, ASTERIA was the prototype, a nanosatellite equipped with...

Hard on the heels of the confirmation of Proxima Centauri b, we get news of Proxima c, which has now been analyzed in new work by Fritz Benedict (McDonald Observatory, University of Texas at Austin). Benedict has presented his findings at the ongoing virtual meeting of the American Astronomical Society, which ends today. The work follows up and lends weight to the discovery of Proxima c announced earlier this year by a team led by Mario Damasso of Italy's National Institute for Astrophysics (INAF), which had used radial velocity methods to observe the star. We need further work, however, to say that Proxima c has been confirmed, as Dr. Benedict explained in an email this morning. But first, let's straighten out a question of identity. Yesterday, when discussing the confirmation of habitable zone world Proxima b, we talked about a second signal in data culled by the ESPRESSO spectrograph. If the second ESPRESSO signal does turn out to be a planet, it will be a third Proxima Centauri...

I’ve always liked the image of Proxima Centauri b that the ESO’s Martin Kornmesser has conjured directly below, and have used it in a couple of previous articles about the planet. Indeed, you’ll see it propagated widely when the topic comes up. But like all of these exoplanet artist impressions, it’s made up of educated guesses, as it has to be. We don’t even know, for example, whether the world we see here even has an atmosphere, as depicted. Whether or not it does is important because it affects the possibilities for life around the star nearest to our own. Twenty times closer to its star than the Earth is to the Sun, Proxima b nonetheless receives roughly the same energy, meaning we could have surface temperatures there that would support liquid water on the surface. But the planet also receives 400 times more X-rays than the Earth, which leads the University of Geneva’s Christophe Lovis to ask: “Is there an atmosphere that protects the planet from these deadly rays? And if this...

Studying the atmospheres of exoplanets is a process that is fairly well along, especially when it comes to hot Jupiters. Here we have a massive target so close to its star that, when a transit occurs, we can look at the star's light filtering through the atmosphere of the planet. Even so, clouds are a problem because they prevent accurate readings of atmospheric composition below the upper cloud layers. Aerosols -- suspended solid particles or droplets in a gas -- are common, range widely in composition, and make studying a planet's atmosphere harder. We'd like to learn more about which aerosols are where and in what kind of conditions, for we have a useful database of planets to work with. Over 70 exoplanets currently have transmission spectra available. A wide range of cloud types, many of them exotic indeed, have been proposed by astronomers to explain what they are seeing. Imagine clouds of sapphire, or rubies, which is essentially what we get with aerosols of aluminum oxides...

You would think that the orbits of planets would align closely with the spin of their star, since they emerged from the same primordial disk. Many planets do just that, and in our own system, the orbits of the planets are aligned within 6 degrees of the Sun's rotation. But the numerous cases of star-planet orbital misalignment around other stars cause us to question whether these systems formed out of alignment or were influenced by later perturbations. A massive companion in a wide orbit could do the trick, and other mechanisms to tilt the orbital or spin axes are discussed in the literature. To examine the question, the Rossiter-McLaughlin effect comes into play. Discovered by studying binary stars, the effect is named after the two University of Michigan graduate students who figured it out back in the 1920s. They realized that as a star rotates, part of it seems to be coming toward the observer, creating a blueshift, while the other side seems to be moving away, producing a...

It will surprise few Centauri Dreams readers that at least some brown dwarfs have bands of clouds, just as we see similar bands on our Solar System's largest planet. In fact, three brown dwarfs have recently shown signs of cloud banding, and today's subject, Luhman 16, has previously been analyzed in terms of large cloud patches. I think new work based on data from the European Southern Observatory's Very Large Telescope (VLT) in Chile may be less significant for what it says about brown dwarfs than what it says about how we study them. Image: Illustration comparing the masses of planets, brown dwarfs, and stars. Credit: NASA/JPL-Caltech/R. Hurt (IPAC). For the work in question, reported in a paper from Maxwell Millar-Blanchaer (Caltech) and colleagues, is the first time polarimetry has been put to work to infer bands in brown dwarf clouds. Polarization tells us the direction that a light wave oscillates. Millar-Blanchaer likens polarimetric instruments to polarized sunglasses --...

Transit timing variations are useful to astronomers trying to learn what forces are acting upon a known exoplanet. They could eventually help us ferret out the existence of a sufficiently large moon, for example, though we have yet to confirm one. But they also show us how much impact other planets in the same system can have upon the planet being observed. All this is why the Kepler-88 system has been high on the list of interesting targets for astronomers. Before the recent discovery of a new gas giant, we knew about Kepler-88 b and c, one of them (the outer world Kepler-88 c) about 20 times more massive than Kepler-88 b, a planet less massive than Neptune. The story here was the mean motion resonance, in which planet c, a Jupiter-mass world, orbits the star in 22 days while Kepler-88 b orbits in 11: Two orbits of b in the time it takes c to make a single orbit. Planet b is the only transiting planet in this system; Kepler-88 c was confirmed by radial velocity methods. The mass...

We may be measuring planetary temperatures with less than optimum tools. Calling it a "new phenomenon," Cornell University's Nikole Lewis described the background of a just published paper looking into hot Jupiter temperatures. Lewis had been increasingly puzzled by earlier work on the matter, which produced temperatures colder than scientists expected. The deputy director of the Carl Sagan Institute, Lewis joined colleagues Ryan MacDonald and Jayesh Goyal in looking for the reason, reporting their results in Astrophysical Journal Letters. What emerged was the need to fine-tune our analysis of exoplanet atmospheres, as delivered by the technique called transmission spectroscopy, in which the light of a parent star is filtered through a planetary atmosphere during a transit. Have a look, for example, at an illustration of the hot-Jupiter WASP-43b as it transits its star. Scientists have been able to construct temperature maps for the planet as well as probing its atmosphere to...

Objects of interstellar origin in our own Solar System continue to draw attention. Comets from other stars like 2I/Borisov give us the chance to delve into the composition of different stellar systems, while the odd ‘Oumuamua still puzzles astronomers. Comet? Asteroid? Now we have a paper from Fathi Namouni (Observatoire de la Côte d'Azur, France) and Maria Helena Morais (Universidade Estadual Paulista, Brazil) targeting what the duo believe to be a population of asteroids captured from other stars in the distant past. Published in Monthly Notices of the Royal Astronomical Society, the paper relies on a high-resolution statistical search for stable orbits, ‘unwinding’ these orbits back in time to explain the location of certain Centaurs, asteroids moving perpendicular to the orbital plane of the planets and other asteroids. Centaurs, most of which do not occupy such extreme positions, are a population of asteroids moving between the outer planets in what have until now been...

I'm keeping an eye on the recent attention being paid to Proxima Centauri c, the putative planet whose image may have been spotted by careful analysis of data from the SPHERE (Spectro-Polarimetric High-Contrast Exoplanet Research) imager mounted on the European Southern Observatory's Very Large Telescope. A detection by direct imaging of a planet found first by radial velocity methods would be a unique event, and the fact that this might be a planet in the nearest star system to our own makes the story even more interesting. I hasten to add that this is not Proxima b, the intriguing planet in the star's habitable zone, but the much larger candidate world, likely a mini-Neptune, that has been identified but not yet confirmed. Proxima Centauri c could use a follow-up to establish its identity, and this direct imaging work would fit the bill if it holds up. But for now, the planet is still a candidate rather than a known world. From the paper: While we are not able to provide a firm...

What an exceptional system the one around HD 158259 is! Here we have six planets, uncovered with the SOPHIE spectrograph at the Haute-Provence Observatory in the south of France, with the innermost world also confirmed through space-based TESS observations. Multiple things jump out about this system. For one thing, all six planets are close to, but not quite in, a 3:2 resonance. That 'close to' tells the tale, for researchers believe there are clues to the formation history of the system within their observations of this resonance. Image: In the planetary system HD 158259, all pairs of subsequent planets are close to the 3:2 resonance : the inner one completes about three orbits as the outer completes two. Credit & Copyright: UNIGE/NASA. The primary, HD 158259, is itself interesting, in that it's a G-class star about 88 light years out, an object just a little more massive than our Sun. But tucked well within the distance of Mercury from the Sun we find all six of the thus far...