The newly found planet K2-315b catches the eye because of its 3.14-day orbit, a catch from the K2 extension of the Kepler Space Telescope mission that reminds us of a mathematical constant. As I’m prowling through David Berlinski’s Infinite Ascent (Modern Library, 2011), a quirky and quite lively history of mathematics at the moment, the references to ‘pi in the sky’ that I’m seeing in coverage of the discovery are worth a chuckle. Maybe the Pythagoreans were right that everything is number. Pythagoras would have loved K2-315b and would have speculated on its nature. After all, as Berlinski notes about Pythagoras (ca. 570 to ca. 490 BCE) and his followers, they were devoted to what he calls ‘a higher spookiness”: The Pythagoreans never succeeded in explaining what they meant by claiming that number is the essence of all things. Early in the life of the sect, they conjectured that numbers might be the essence of all things because quite literally “the elements of numbers were the...

So often a discovery sets off a follow-up study that strikes me as even more significant in practical terms. This is not for a moment to downplay the accomplishment of Andrew Vanderburg (University of Wisconsin - Madison) and team that discovered a planet in close orbit around a white dwarf. This is the first time we've found a planet that has survived its star's red giant phase and remains in orbit around the remnant, and quite a tight orbit at that. Previously, we've had good evidence only of atmospheric pollution in such stars, indicating infalling material from possible asteroids or other objects during the primary's cataclysmic re-configuration. The white dwarf planet, found via data gathered from TESS (Transiting Exoplanet Survey Satellite) and the Spitzer Space Telescope, makes for quite a discovery. But coming out of this work, I also love the idea of studying such a world with tools we're likely to have soon, such as the James Webb Space Telescope, and on that score, Lisa...

This morning we have two interesting and complementary studies of GW Orionis to look at, both analyzing what is apparently a planet-forming disk with multiple, misaligned rings around this triple star system some 1300 light years from the Sun. In the more recent of the two, Stefan Kraus (University of Exeter) and colleagues used data from both the Atacama Large Millimeter/submillimeter Array (ALMA) and the European Observatory's Very Large Telescope (VLT) in detecting warm gas at the inner edge of the misaligned ring, which has broken away from the larger disc, and scattered light from the warped disk surface. So what could be going on at GW Orionis? What the images reveal is an evolving young system much different from our own. Consider: The inner stars GW Ori A and GW Ori B orbit each other at a separation of a scant 1 AU, while the third star, GW Ori C, orbits the inner stars at a distance of roughly 8 AU, the latter in an orbit that is not aligned with the plane of the inner duo....

SPARCS is the name of a CubeSat-based space mission out of Arizona State University, the acronym standing for Star-Planet Activity Research CubeSat, with astronomer Evgenya Shkolnik as principal investigator. The idea here is to look at ultraviolet flare activity on M-dwarf stars, a wavelength about which we could do with a great deal more information. The plan is to target specific stars that will be observed continuously over at least one complete stellar rotation, which could be anything from five to forty-five days. That this is a good idea is borne out by what we are learning about GJ 887, also known as Lacaille 9352 and known to be orbited by at least two planets. Located in the southern constellation of Piscis Austrinus, the star has the fourth highest known proper motion, with parallax measurements indicating it is a bit less than 11 light years from the Sun. It is one of the brightest M-dwarfs in our sky. When TESS (Transiting Exoplanet Survey Satellite) fixed its gaze on GJ...

The boundary between planet and star is hard enough to pin down without thinking of some recently discovered brown dwarfs that are cool enough to approach Earth temperatures. Yet worlds/stars like these are among the haul assembled by volunteers working data for Backyard Worlds: Planet 9, a citizen science project whose latest findings include 95 cool brown dwarfs in the Sun's neighborhood, as reported in the Astrophysical Journal. Despite a determined search, we've yet to find such an object closer than the nearest stars at Alpha Centauri. But 23 light years out -- the distance of the closest of these brown dwarfs -- is definitely close in galactic terms, and most of the brown dwarfs tracked in the new work are between 30 and 60 light years from Earth. That makes sense, for objects like these are faint enough that identifying them at greater range is all but impossible. The data used in the brown dwarf collection come from a range of observatories including W. M. Keck, Mont...

When it comes to detecting life on planets around other stars, my guess is that what will initially appear to be a life signature will quickly become controversial. We might, for example, find ozone in an exoplanet atmosphere with a space telescope like HabEX (Habitable Exoplanet Observatory). That would lead to hyperbolic news stories, to be sure, but ozone can happen when nitrogen and oxygen are exposed to ultraviolet light. The presence of ozone makes no definitive statement about life. In fact, definitive statements about life may take more than a few decades to achieve. If ozone seems like a good catch, that's because it implies oxygen, which makes us think of photosynthesis, but oxygen itself is hardly infallible as a biosignature. Oxygen-rich atmospheres can be completely abiotic, with UV from the host star breaking down carbon dioxide. For that matter, an atmosphere rich in water vapor can produce oxygen and hydrogen through the effects of UV radiation. Better, then, to look...

The exoplanet K2-25b, a young world in the Hyades cluster orbiting an M-dwarf star, raises intriguing questions. We’d like to know how it formed, for K2-25b is much more dense than we would expect for a world slightly smaller than Neptune. Planets in a range between Earth and Neptune seem to be common around other stars, although we have none in our Solar System unless we make an interesting discovery about putative Planet 9. But let lead author Gudmundur Stefánsson (Princeton University) point out the unusual nature of K2-25b:: “The planet is dense for its size and age, in contrast to other young, sub-Neptune-sized planets that orbit close to their host star. Usually these worlds are observed to have low densities — and some even have extended evaporating atmospheres. K2-25b, with the measurements in hand, seems to have a dense core, either rocky or water-rich, with a thin envelope.” Image: New detailed observations with NSF’s NOIRLab facilities reveal a young exoplanet, orbiting a...

Under other circumstances, the red dwarf TVLM 513-46546 would not cause a ripple in news coverage of exoplanets. What astronomers have found there is a planet of Saturn mass in a 221 day orbit, raising eyebrows only in that while planets are common around M-dwarfs, they are usually smaller, rocky worlds. But the TVLM 513-46546 story gains weight when we consider the methods used to find this planet, which have implications for studying system architectures around many stars as we refine our techniques and new instruments come online. The star in question is 35 light years from Earth, and we've found the planet through astrometry, a method that tracks a star's position in the sky to an extreme precision and detects the minute variation in motion caused by the gravitational effect of the planet. If this sounds a bit like radial velocity methods, the difference is that with astrometry we are measuring tiny changes in the stars position in the sky, as opposed to the Doppler shift of...

How many habitable planets should we expect in the average stellar system? One sounds like a good number to me, even an optimistic one. But it’s a tough question because we don’t exactly know what an ‘average’ stellar system is, there being such a wide range currently being discovered. There was a time less than a century ago when the idea that there might be three habitable planets -- i.e., habitable by humans -- in the Solar System was current. Imagine Venus as something like French Polynesia, or maybe what was then the Belgian Congo. Imagine Mars with a thicker atmosphere and ancient seas, Edgar Rice Burroughs territory. Today we think of multiple habitability here in the Solar System as perhaps including ocean life under the ice of the moons of giant planets, but we’ve ruled out anything a human could walk around on in relative comfort. The question of what makes our Solar System able to support just one planet in the human habitability range bothered Stephen Kane (UC-Riverside)...

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...