New evidence for the nature of interstellar object ‘Oumuamua is in, making it far more likely that the unusual interloper is a comet rather than an asteroid. The data come from an array of instrumentation -- the Hubble Space Telescope, the Canada-France-Hawaii Telescope, ESO’s Very Large Telescope and the Gemini South Telescope -- and show that `Oumuamua is slowing down slightly less than expected. We are talking about a tiny force, about 1/1000 as strong as the pull of the Sun’s gravity, according to this overview of new work in Nature. The science paper on this work, which also appears in Nature, looks at a variety of possible explanations for the velocity change. The one the authors think most likely is that `Oumuamua (pronounced “oh-MOO-ah-MOO-ah”), now moving at some 114,000 kilometers per hour, has vented material during its pass through our system, behaving the way many comets do. Marco Micheli (ESA), lead author of the paper, puts it this way: “We can see in the data that its...

Some 150 globular clusters are associated with the Milky Way, great collections of stars inhabiting the galactic halo. Their stars have long been assumed to be ancient, making the question of life there intriguing: If life caught hold in these tightly packed clusters early in the universe’s evolution, could ancient civilizations have formed that might persist even today? I know of only one planet that has yet been found in a globular cluster, but we’re obviously early in the game, and planets have been discovered in open clusters, which are much less densely packed. Just how little we know about globular clusters, though, is made apparent by the work of Elizabeth Stanway (University of Warwick), whose new paper argues that such clusters could be billions of years younger than we have thought. Working with JJ Eldridge (University of Auckland), Stanway invokes a model called Binary Population and Spectral Synthesis (BPASS). In play here is the evolution of binary stars within globular...

When life first arose in the universe is a question to which we have no answer. A key problem here is that without knowing how rare -- or common -- life's emergence is, we can't draw conclusions about where (or when) to find it. One thing that is accessible to us, though, is information about when stars began the process of producing the elements beyond hydrogen and helium that are constituents of our own living systems. And on that score, we have interesting news from an international team of scientists about extremely old galaxies. Led by Takuya Hashimoto and Akio Inoue (Osaka Sangyo University), the researchers have gone to work on a galaxy known as MACS1149-JD1, using data acquired from the Atacama Large Millimetre/Submillimetre Array (ALMA) and the European Southern Observatory's Very Large Telescope (VLT). The team's paper in Nature confirms that the galaxy is some 13.28 billion light years away. Thus we see it as it appeared when the universe was about 500 million years old....

It's conceivable that getting humans to an interstellar object may not involve journeying all the way to another star. We've learned that wandering asteroids and comets move between stars, as the case of 'Oumuamua demonstrated, and early research offers the possibility that such objects exist in large numbers. Now we have (514107) 2015 BZ509, which is conceivably an interloper into our system of another sort. Two researchers believe that this asteroid near the orbit of Jupiter is not just passing through, but a captured object from another stellar system. A comparison with Triton seems apt. One of the most compelling pieces of evidence that Neptune's largest moon is actually a Kuiper Belt Object is its retrograde orbit. We see the same thing with 2015 BZ509, and for Fathi Namouni (Observatoire de la Côte d'Azur) and Helena Morais (Universidade Estadual Paulista), that sends a clear message. The researchers have offered their work in a new paper in Monthly Notices of the Royal...

Back in the late 1970s I didn't know anything about star catalogs. I suppose that, if asked, I would have assumed they were out there -- how otherwise could astronomers do their jobs? But the first catalog of stars that came into my life emerged when I was writing an article about SETI, a field I developed an intense interest in and at that time knew very little about. For the article I needed to identify the closest stars, and thus I stumbled upon the Gliese Catalog of Nearby Stars, and over the course of time became absorbed by the idea of exoplanets. In many ways my first dip into the Gliese catalog began the journey that continues here, because that first SETI article was the forerunner of the kind of writing I have been doing since the turn of the century. In that time our catalogs have grown more and more interesting to me, but none can match today's, the all-sky view of almost 1.7 billion stars that is the result of the European Space Agency's Gaia mission. The second Gaia...

With TESS going into a 60-day period of calibration and testing, I'll turn this morning to a different kind of survey. GALAH is an acronym for Galactic Archaeology, a term I've generally associated with so-called Dysonian SETI, where data is mined in a search for signs of advanced engineering or any anomalies that could signify an extraterrestrial civilization at work. But GALAH has a different object: It has examined some 340,000 stars enroute to 1 million. A just published paper on GALAH states the goal succinctly: The overarching goal of the GALAH survey is to acquire high-resolution spectra of a million stars for chemical tagging, in order to investigate the assembly history of the Galaxy. The survey was launched in 2013 as a deep study of galactic formation and evolution, using the HERMES spectrograph at the Australian Astronomical Observatory's 3.9-meter Anglo-Australian Telescope near Coonabarabran, NSW. Now coming online is a major data release, the second from GALAH, that...

Here's an interesting situation: Around a star designated GSC 07396-00759, a member of a multiple star system, astronomers have found an edge-on disk. Such disks are helpful ways of studying planetary evolution, as we're looking at gas, dust and planetesimals that represent a planetary system in the process of formation. But at GSC 07396-00759, the disk is more evolved than the gas-rich disk around the T Tauri star in the same system. In other words, we have two stars evidently of the same age whose disks show a different evolutionary pace. Elena Sissa (INAF-Osservatorio Astronomico di Padova) is lead author of a new paper on this find, in press at Astronomy & Astrophysics. The paper puts the matter this way: Even if there is no "smoking gun" proof, the system characteristics all together tend to favor an evolved/debris disk nature for GSC 07396-00759 over a primordial/gas-rich disk. If confirmed, this is a very interesting discovery since this star and V4046 Sgr form a coeval...

The fleeting interstellar visitor we call 'Oumuamua is back in the news, an object whose fascination burns bright given its status as a visitor from another star system. Just what kind of system is the subject of a new letter just published in Monthly Notices of the Royal Astronomical Society, in which Alan Jackson and colleagues argue that the star-crossed wanderer is most likely the offspring of a binary stellar system, these being far more likely to eject rocky objects. Our first confirmed interstellar asteroid just grows in interest. Jackson (University of Toronto - Scarborough) is quoted in this news release from the Royal Astronomical Society as saying that the odds didn’t favor the first interstellar object detected in our system being an asteroid. Comets are more likely to be spotted, and our system is more efficient at ejecting comets than asteroids. But 'Oumuamua is what we got, and its eccentricity of 1.2 and 30 km/sec speed pegged its orbit as hyperbolic, clearly not...

Simon Lock and Sarah Stewart are intent upon revising our views on how the Moon was formed. Lock is a Harvard graduate student who last year, in company with Stewart (UC-Davis) presented interesting work on what the duo are calling a 'synestia,' which is the kind of 'structure' resulting from the collision of huge objects. Current thinking about the Moon is that it formed following the collision of a Mars-sized object with the Earth, two huge objects indeed. What Lock and Stewart asked is whether this formation scenario can produce the result we see today. What it calls for is the ejection of material that forms into a disk and, through processes of accretion, gradually becomes the Moon. The problem with it, says Lock, is that it's a very hard trick to pull off: "Getting enough mass into orbit in the canonical scenario is actually very difficult, and there's a very narrow range of collisions that might be able to do it. There's only a couple-of-degree window of impact angles and a...

"Wherever you go, there you are." So goes an old saw that makes a valid point: You can't escape yourself by changing locations. Translating the great Greek poet C. P. Cavafy, Lawrence Durrell tweaked the language of "The God Abandons Antony" to come up with these closing lines: Ah! don't you see Just as you've ruined your life in this One plot of ground you've ruined its worth Everywhere now — over the whole earth? All this in the service of Durrell's Alexandria Quartet, noting the fact that not even a Roman autocrat could escape his fate. Bear with me -- I think about stuff like this when I'm out walking late at night and the stars are particularly stunning. Before my walk, I had been looking at images of M31, the Andromeda galaxy, and doing my usual "What would it be like to be there" routine. Minus Durrell/Cavafy's dark vision, I might still ask myself what had changed. From a vantage in the Andromeda galaxy, there would be a Milky Way in my sky. And what else? Then David...

The behavior of distant galaxies may tell us much about our own Milky Way’s evolution, as well as alerting us to the differing outcomes possible as galaxies mature. This morning we look at a galaxy labeled eMACSJ1341-QG-1, one that puts on display the phenomenon of gravitational lensing. We may one day use the distortion of spacetime caused by massive objects much closer to home to study nearby stars and their planets, assuming we can learn to exploit the natural gravitational lensing effect that occurs at 550 AU from the Sun. But back to the galactic perspective. Lined up with a massive galaxy cluster called eMACSJ1341.9-2441, the light from the much more distant galaxy is magnified by 30 times as the gravity of the intervening cluster -- its presumed dark matter, gas and thousands of individual galaxies -- distorts spacetime. Gravitational lensing was confirmed during a solar eclipse in 1919, when background stars were found to be offset in precisely the way Albert Einstein had...

An absorption nebula, or 'dark' nebula, is a dense cloud of interstellar dust that can block the visible light from objects within or behind it. Today's image shows a striking cloud in the star-forming region Lupus 3, a dazzling view that simply demanded placement on Centauri Dreams. If you're looking for an interstellar flight angle, think about the issue of shielding a relativistic starship in regions so dense with gas and dust, zones that can stretch for hundreds of light years. But I need no other angle here -- the image is majestic in and of itself. Image: A dark cloud of cosmic dust snakes across this spectacular wide field image, illuminated by the brilliant light of new stars. This dense cloud is a star-forming region called Lupus 3, where dazzlingly hot stars are born from collapsing masses of gas and dust. This image was created from images taken using the VLT Survey Telescope and the MPG/ESO 2.2-metre telescope and is the most detailed image taken so far of this region....

When you think about what a space telescope goes through to get out of the gravity well and into its planned position, it's a wonder that instruments this exacting can survive the journey. Launch vibration can reach six times Earth gravity and higher, while temperatures are all over the place as the launch vehicle moves from a temperate climate into the deep chill of space. Countering all this while ever tightening the parameters of our instruments is a herculean challenge, but there is good news out of Goddard Space Flight Center, where Babak Saif and Lee Feinberg have gone to work on the problem. Working with Perry Greenfield at the Space Telescope Science Institute in Baltimore, the duo have been using an instrument called the High-Speed Interferometer (HSI), developed in Arizona by 4D Technology, to measure the changes that can occur over the surface of a spare 5-foot mirror segment, along with its support hardware, from the James Webb Space Telescope. The HSI was designed to...

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...

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...

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...

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...

Another of those 'new eras' I talked about in yesterday's post is involved in the latest news on gravitational waves. Let's not forget that it was 50 years ago -- on November 28, 1967 -- that Jocelyn Bell Burnell and Antony Hewish observed the first pulsar, now known to be a neutron star. It made the news at the time because the pulses, separated by 1.33 seconds, raised a SETI possibility, leading to the playful designation LGM-1 ('little green men') for the discovery. We've learned a lot about pulsars emitting beams at various wavelengths since then and the SETI connection is gone, but before I leave the past, it's also worth recognizing that our old friend Fritz Zwicky, working with Walter Baade, first proposed the existence of neutron stars in 1934. The scientists believed that a dense star made of neutrons could result from a supernova explosion, and here we might think of the Crab pulsar at the center of the Crab Nebula, an object whose description fits the pioneering work of...

We seem to be entering 'new eras' faster than I can track. Certainly the gravitational wave event GW170817 demonstrates how exciting the prospects for this new kind of astronomy are, with its discovery of a neutron star merger producing a heavy-metal seeding 'kilonova.' But remember, too, how early we are in the exoplanet hunt. The first exoplanets ever detected were found as recently as 1992 around the pulsar PSR B1257+12. Discoveries mushroom. We've gone from a few odd planets around a single pulsar to thousands of exoplanets in a mere 25 years. We're seeing changes that propel discovery at an extraordinarily fast pace. Look throughout the spectrum of ideas and you can also see that we're applying artificial intelligence to huge datasets, mining not only recent but decades-old information for new insights. Today's problem isn't so much data acquisition as it is data storage, retrieval and analysis. For the data are there in vast numbers, soon to be augmented by huge new telescopes...

I had thought to go straight back into current news after Centauri Dreams' recent hiatus, but that's never a fully satisfactory solution, especially when major events happen while I'm away. I don't want to simply repeat what everyone has already read about the gravitational wave event GW170817, but there are a few things that caught my eye that we can discuss this morning. After all, we're dealing with a new phenomenon -- kilonovae -- that has been predicted but never observed. Nor have we ever before tied gravitational wave events to visible light. Image: Artist's impression of merging neutron stars. Credit: ESO. Now we're seeing the combination of gravitational wave and electromagnetic astronomy in what promises to be a fertile new ground of study. The fifth GW event ever observed, GW170817 was detected on August 17 of this year by the Laser Interferometer Gravitational-Wave Observatory (LIGO) in the US, working with the Virgo Interferometer in Italy. In less than two seconds, the...