White dwarfs have turned out to be more interesting than I had imagined. We know how they form: A star like the Sun exhausts the hydrogen in its core and swells into a red giant, a scenario that is a trope in science fiction, as it posits an Earth of the far-future incinerated by its star. Losing its outer layers near the end of nuclear burning, a red giant ultimately leaves behind an object with much of the mass of the Sun now crammed into a white dwarf that is about the size of the Earth. For years I assumed white dwarfs were dead ends, a terminus for life whose only function seemed to be in binary systems, where they could be the locus, through accretion from the other star, of a stellar explosion in the form of a nova. Lately we've been learning, though, that through analysis of their atmospheres, white dwarfs can yield information about objects that have fallen into them, such as remnants of the original stellar system. Some white dwarfs may have habitable zones lasting several...

Here's a story that's both mind-bending and light-bending. It involves a supernova that, on the one hand, happened 10 billion years ago, and on the other hand, has appeared in our skies not once but three times, with a fourth in the works. In play here is gravitational lensing, in which light from a background galaxy bends around a foreground galactic cluster known as MACS J0138.0-2155. Out of this we get multiple mirror images, and researchers predict another supernova appearance in the year 2037. Three of the appearances of the supernova, labeled AT 2016jka and nicknamed 'Requiem,' are in the image below, a Hubble view from 2016, all three circled for ease of identification. The light of the supernova has been split into different images by the lensing effect. Using archival data, researchers led by Steve Rodney (University of South Carolina) have analyzed differences in brightness and color that reflect different phases of the event as the supernova faded. "This new discovery is...

The brown dwarf WISEA J153429.75-104303.3 -- happily nicknamed ‘The Accident’ -- is peculiar enough that it may point to a rare population of extremely old brown dwarfs. Dan Caselden, a citizen scientist who built an online program to filter data from the NEOWISE spacecraft, is able to highlight brown dwarfs moving through the NEOWISE field with his software, and while looking at one, he caught a glimpse of another. Call that a lucky catch, because the object didn’t match his program’s profile of a conventional brown dwarf. We’ve found about 2,000 brown dwarfs thus far, many using data from WISE -- Wide Field Infrared Survey Explorer -- which was launched in 2009, placed into hibernation in 2011 after its primary mission ended, and then reactivated in 2013 as NEOWISE, a repurposed spacecraft given the new goal of tracking near-Earth objects. WISE 1534?1043 -- the shortened name of the object, used by the authors of a new paper on it -- stands out from all previously known brown...

Anomalies in our models are productive. Often they can be explained by errors in analysis or sometimes systematic issues with equipment. In any case, they force us to examine assumptions and suggest hypotheses to explain them, as in the case of the unusual acceleration of stars that has turned up in two areas. Greg Matloff has written about one of them in these pages, the so-called Parenago’s Discontinuity that flags an unusual fact about stellar motion: Cool stars, including the Sun, revolve around galactic center faster than hotter ones. This shift in star velocities occurs around (B-V) = 0.62, which corresponds to late F- or early G-class stars and extends down to M-dwarfs. In other words, stars with (B-V) greater than 0.61 revolve faster. The (B-V) statement refers to a color index that is used to quantify the colors of stars using two filters. One, the blue (B) filter, lets only a narrow range of wavelengths centered on blue colors through, while the (V) visual filter only...

Infrared imagery drawn from Spitzer Space Telescope data, coupled with the massive Gaia Early third Data Release (EDR3), have just given us a new insight into our galaxy's spiral structure. The Milky Way's Sagittarius Arm is now shown to have a 'spur' of star-forming gas and young stars emerging at a steep angle and stretching some 3,000 light years. The authors of the paper on this work refer to it as "unprecedented in the context of the generally adopted model of the Milky Way spiral structure." The spur was a tricky catch, because from our position within the galactic disk we can only see the full spiral structure in galaxies other than our own. But the authors point out that in these galaxies, spiral arms often show smaller-scale structures including 'spurs,' which are luminous groupings of stars, and 'feathers,' which are dust features. We also find branching in the main arms. Now we've identified a spur structure in the Milky Way. Image: Artist's concept of the Milky Way. The...

The X-ray 'echoes' from the Seyfert galaxy I Zwicky 1 occupied us on Friday, but today I want to explore the larger content of black hole research following the news about the relatively nearby active galaxy called Centaurus A. Whereas the X-ray work took data from two X-ray telescopes, NuSTAR and XMM-Newton, the Centaurus A investigation gives us another startling image from the instrument that to my mind has the coolest name of them all when it comes to observing tools -- the Event Horizon Telescope. It was the virtual EHT, of course, that produced the first image of a black hole, the supermassive object at the center of M87. The same observing campaign in 2017 produced the data used in the new paper on Centaurus A. At some 10-13 million light years, Centaurus A is -- at radio wavelengths -- one of the largest and brightest objects in the sky. Its central black hole is thought to mass about 55 million suns. By contrast, the EHT researchers have estimated the black hole in M87's...

The first direct observation of light from behind a black hole has just been described in a paper in Nature. What is striking in this work is not so much the confirmation, yet again, of Einstein's General Relativity, but the fact that we can observe the effect in action in this environment. Having just read Heino Falcke's Light in the Darkness: Black Holes, the Universe, and Us (HarperOne 2021), I have been thinking a lot about observing what was once thought unobservable, as Falcke and the worldwide interferometric effort called the Event Horizon Telescope managed to do when they produced the first image of a black hole. The famous image out of that work that went worldwide in the media was of the supermassive black hole at the center of the galaxy M87, while the new paper -- which offers no image but rather data on telltale X-ray emissions -- covers a galaxy called I Zwicky 1 (I Zw 1), a Seyfert galaxy 800 million light years from the Sun. These are active galaxies with...

About 1,000 light years away in the constellation Perseus, the stellar nursery designated NGC 1333 is emerging as a priority target for astronomers planning to use the James Webb Space Telescope. Brown dwarfs come into play in the planned work, as do the free-floating 'rogue' planets we discussed recently. For NGC 1333 is a compact, relatively nearby target, positioned at the edge of a star-forming molecular cloud. It's packed with hundreds of young stars, many of them hidden from view by dust, a venue in which to observe star formation in action. Hoping to learn more about very low mass objects, Aleks Scholz (University of St Andrews, UK) lays out plans for using JWST to chart the distinctions between objects that emerge out of gravitational collapse of gas and dust clouds, and objects that grow through accretion inside a circumstellar disk. Says Scholz: "The least massive brown dwarfs identified so far are only five to 10 times heftier than the planet Jupiter. We don't yet know...

Hard to believe that Fast Radio Bursts (FRBs) were only discovered in 2007, as it seems we've been puzzled by them for a lot longer. Thus far about 140 FRBs have been detected, but now we have news that the Canadian Hydrogen Intensity Mapping Experiment (CHIME) has pulled in a total of 535 new fast radio bursts in its first year of operation between 2018 and 2019. The catalog growing from this work was presented this week at the annual meeting of the American Astronomical Society. "Before CHIME, there were less than 100 total discovered FRBs; now, after one year of observation, we've discovered hundreds more," says CHIME member Kaitlyn Shin, a graduate student in MIT's Department of Physics. "With all these sources, we can really start getting a picture of what FRBs look like as a whole, what astrophysics might be driving these events, and how they can be used to study the universe going forward." Image: The large radio telescope CHIME, pictured here, has detected more than 500...

If we assume that the Oort Cloud, that enveloping shroud of comets that surrounds our Solar System and extends to 100,000 AU or beyond, is a common feature of stellar systems, then it’s conceivable that objects are interchanged between the Sun and Alpha Centauri where the two clouds approach each other. That makes for the ‘slow boat to Centauri’ concept I’ve written about before, where travel between the stars essentially mines resources along the way in migrations lasting thousands of years. The resulting society would not be planet-oriented. When the Dutch astronomer Jan Hendrik Oort deduced the cloud’s existence, he theorized that there was an inner, disk-shaped component as well as an outer, spherical cloud, as shown in the image below. The outer cloud is only loosely bound to the Sun, making the interchange of cometary materials between stars a likely event over the aeons, while gravitational nudges from passing stars can dislodge comets in the other direction as well, causing...

The galaxy UGC 10738 resonates with the galaxy described yesterday -- BRI 1335-0417 -- in that it raises questions about how spiral galaxies form. In fact, the team working on UGC 10738 thinks it goes a long way toward answering them. That's because what we see here is a cross-sectional view of a galaxy much like the Milky Way, one that has both 'thick' and 'thin' disks like ours. The implication is that these structures are not the result of collisions with smaller galaxies but typical formation patterns for all spirals. Nicholas Scott and Jesse van de Sande (ASTRO 3D/University of Sydney) led the study, which used data from the European Southern Observatory's Very Large Telescope in Chile. As you can see from the image below, the galaxy, some 320 million light years away, presents itself to us edge on, offering a cross-section of its structure. Key to the work was the team's assessment of stellar metallicity, as van de Sande explains: "Using an instrument called the multi-unit...

My fascination with the earliest era of star and galaxy formation leads me to a new paper on an intriguing find. The authors describe the distant object BRI 1335-0417 as "an intensely star-forming galaxy," and its image as captured by the Atacama Large Millimeter/submillimeter Array (ALMA) is striking. This is a galaxy that formed a mere 1.4 billion years after the Big Bang, making it the most ancient galaxy with spiral structure ever observed. Spirals make up perhaps 70 percent of the galaxies in our catalogs, but how they form is an open question. Indeed, the proportion of spiral galaxies declines the further back in the evolution of the universe we observe. The spiral structure observed here extends 15,000 light years from the center of the galaxy (about a third the size of the Milky Way), while the total mass of stars and interstellar matter roughly equals our own galaxy. Image: ALMA image of a galaxy BRI1335-0417 in the Universe 12.4 billion years ago. ALMA detected emissions...

As we follow the progress of the James Webb Space Telescope through performance tests in preparation for launch, Robert Zubrin has been thinking of far larger instruments. The president of Pioneer Astronautics and founder of the Mars Society thinks we can create telescopes of extremely large aperture -- and sharply lower cost -- by using the physics of spinning gossamer membranes, a method suitable for early testing as a CubeSat demonstration mission. In today's essay, Dr. Zubrin explains the concept and considers how best to deploy next generation space telescopes reaching apertures as large as 1000 meters. We can't know what new phenomena such an instrument would find, but the Enormous Space Telescope fits the theme of breakthrough discovery outlined in his latest book, The Case for Space: How the Revolution in Spaceflight Opens Up a Future of Limitless Possibility (Prometheus, 2020). by Robert Zubrin Abstract This paper presents a method for creating Enormous Space Telescopes...

This seems to be the week of unusual configurations. Following up on TRAPPIST-1 and TOI-178 comes TYC 7037-89-1, where we have fully six stars in a single system, all of which participate in eclipses. In other words, what TESS has revealed is a system consisting of three eclipsing binaries. It's located about 1,900 light years out in Eridanus, and if it doesn't remind you of Isaac Asimov's "Nightfall," nothing will. In the story (published in the September 1941 issue of Astounding Science Fiction), the planet Lagash is illuminated almost constantly by one of the six stars in its system. The discovery of what happens when it is not -- which occurs every 2,000 years or so -- drives the plot of one of Asimov's best tales. TYC 7037-89-1 (also known as TIC 168789840), marks the first time a six-star system has been found where all the stars are involved in eclipses as seen from our vantage point. This leads to complicated orbital dynamics. With the three binaries designated A, B and C, we...

Something to note about the brown dwarfs we looked at yesterday: Our views on how they would appear to someone nearby in visible light are changing. It’s an interesting issue because these brown dwarfs exist in more than a single type. If you’ll have a look at the image below, you’ll see a NASA artist conception of the three classes of brown dwarf, all of these being objects that lack the mass to burn with sustained fusion. Image: This artist's conception illustrates what brown dwarfs of different types might look like to a hypothetical interstellar traveler who has flown a spaceship to each one. Brown dwarfs are like stars, but they aren't massive enough to fuse atoms steadily and shine with starlight -- as our sun does so well. Our thoughts on how these objects appear are evolving quickly, as witness yesterday’s discussion, and we’re likely to need another visual rendering of brown dwarf classes soon. Credit: NASA/JPL-Caltech. One thing should jump out to anyone who read...

I keep hoping we'll find a brown dwarf closer to us than Alpha Centauri, but none have turned up yet despite the best efforts of missions like WISE (Wide-Field Infrared Survey Explorer). If there's something out there, it's dim indeed. Of course, I wouldn't be surprised at finding rogue planets between us and the nearest stars. Maybe some will be more massive than Jupiter, but evidently not massive enough to throw an infrared signature of the sort that defines a brown dwarf. Just what lies outside our system's edge always makes for interesting speculation. The beauty of finding an actual brown dwarf as opposed to a rogue planet is that we might be dealing with a planetary system in miniature, a fine target in our own backyards. Lacking that, the closest brown dwarf we know is the Luhman 16 AB system, a binary in the southern constellation of Vela some 6.5 light years from the Sun (a little further than Barnard's Star, making this the third closest known system to the Sun). Here we...

The evolving system known as [BHB2007] 1 is a part of the Pipe Nebula (also called Barnard 59), about 600 light years away in the constellation Ophiuchus. It is part of a binary star system in formation that has been studied with the Atacama Large Millimeter Array (ALMA). Both protostars show disks in formation around them, surrounded by filaments of gas and dust drawn from the larger disk that are being referred to as 'feeding filaments.' Paola Caselli (Max Planck Institute for Extraterrestrial Physics, Germany), who made that reference in 2019, is co-author of new work on the stellar object, which gives us an unusual look at early system formation. Image: This false-color image shows the filaments of accretion around the protostar [BHB2007] 1. The large structures are inflows of molecular gas (CO) nurturing the disk surrounding the protostar. The inset shows the dust emission from the disk, which is seen edge-on. The "holes" in the dust map represent an enormous ringed cavity seen...

A sequence of new observations gives us a leading candidate to explain Fast Radio Bursts (FRBs). These powerful bursts of radio waves, lasting but milliseconds, first turned up in our data in 2007 and have been a mystery ever since. As they were found in other galaxies, it has been difficult to determine their exact location, and they were impossible to predict as most seemed to be one-off events, although astronomers have subsequently found some that do repeat. Among the possible causes of FRBs, stellar remnants have been put forward, with the kind of highly magnetic neutron stars called magnetars receiving close scrutiny because their magnetic fields could be the engine driving the bursts. We now have three papers in Nature that give us tight observational evidence of the kind that has been lacking. Between the three, we have data that for the first time link an FRB in our own galaxy to a magnetar, the object known as SGR 1935+2154, located in the constellation Vulpecula. Image:...

Discussions of the Milky Way's center have always attracted me. Here we find ancient stars, with all that suggests about the possibility of long-lived civilizations, but occurring in a place where ionizing radiation associated with the galaxy's supermassive black hole (Sagittarius A*) may push the habitable regions out into the galactic suburbs. And then there are all those supernovae to contend with! Maybe life in these parts is, if present, single-celled, perhaps underwater, with brief land colonization before new extinction events erase it. Whatever the case, I'm learning that the galaxy's central bulge is inspiring a new wave of study. A survey of millions of stars there is producing insights into how the bulge originally formed. We can look at spiral galaxies near and far and find commonality in their central bulge of stars surrounded by the familiar disk, but if the bulge stars formed in a single burst of activity, we could be seeing a population as old as 10 billion years in...

The Hubble Deep Field images of 1995 and 1998 gave us an unprecedented look at a small patch of sky with few nearby bright objects, a region about one-tenth the diameter of the full Moon in the constellation Fornax. The ensuing Hubble Ultra Deep Field, released in 2004, contains as many as 10,000 individual galaxies. Hubble's Advanced Camera for Surveys (ACS) was deployed for this, as well as its Near Infrared Camera and Multi-object Spectrometer (NICMOS), producing a stunning harvest of elliptical and spiral galaxies, as well as oddly shaped collections of stars from the chaotic early days of the universe. Image: The original NASA release image of the Hubble Ultra Deep Field, containing galaxies of various ages, sizes, shapes, and colors. The smallest, reddest galaxies, of which there are approximately 10,000, are some of the most distant galaxies to have been imaged by an optical telescope, probably existing shortly after the Big Bang. Credit: NASA/ESA. I immediately thought of a...