NASA’s recently launched SPHEREx space telescope will map the entire celestial sky four times in two years, creating a 3D map of over 450 million galaxies. We can hope for new data on the composition of interstellar dust, among other things, so the mission has certain astrobiological implications. But today I’m focusing on the idea of maps of stars as created from our vantage here on Earth. How best to make maps of a 3D volume of stars? I’ve recently been in touch with Kevin Wall, who under the business name Astrocartics Lab has created the Astrocartics and Interstellar Surveyor maps he continues to refine. He explains the background of his interest in the subject in today’s essay while delving into the principles behind his work. by Kevin Wall The most imposing aspect of the universe we live in is that it is 3-dimensional. The star charts of the constellations that we are most familiar with show the 2-dimensional positions of stars fixed on the dome of the sky. We do not, however,...

As we’ve been examining the connections between nearby stars lately and the possibility of their exchanging materials like comets and asteroids with their neighbors, the effects of more distant events seem a natural segue. A new paper in Monthly Notices of the Royal Astronomical Society makes the case that at least two mass extinction events in our planet’s history were forced by nearby supernova explosions. Yet another science fiction foray turned into an astrophysical investigation. One SF treatment of the idea is Richard Cowper’s Twilight of Briareus a central theme of which is the transformation of Earth through just such an explosion. Published by Gollancz in 1974, the novel is a wild tale of alien intervention in Earth’s affairs triggered by the explosion of the star Briareus Delta, some 130 light years out, and it holds up well today. Cowper is the pseudonym for John Middleton Murry Jr., an author I’ve tracked since this novel came out and whose work I occasionally reread....

Peculiar things always get our attention, calling to mind the adage that scientific discovery revolves around the person who notices something no one else has and says “That’s odd.” The thought is usually ascribed to Asimov, but there is evidently no solid attribution. Whoever said it in whatever context, “that’s odd” is a better term than “Eureka!” to describe a new insight into nature. So often we learn not all at once but by nudges and hunches. This may be the case with the odd objects turned up by the Japanese infrared satellite AKARI in 2021. Looking toward the Scutum-Centaurus Arm along the galactic plane, the observatory found deep absorption bands of the kind produced by interstellar dust and ice. No surprise that a spectral analysis revealed water, carbon dioxide, carbon monoxide and organic molecules, given that interstellar ices in star-forming regions are rich in these chemicals, but the ‘odd’ bit is that these two objects are a long way from any such regions. Image:...

Work is healing, so let’s get back to it. I’m enthralled with what we’re discovering as we steadily build our catalog of fast radio bursts (FRB), close to 100 of which have now been associated with a galaxy. These are transient radio pulses of short duration (down to a fraction of a millisecond, though some last several seconds), the first being found in 2007 by Duncan Lorimer, an astronomer at West Virginia University. Sometimes FRBs repeat, although many do not, and one is known to repeat on a regular basis. What kind of astrophysical processes might be driving such a phenomenon? The leading candidate appears to be supernovae in a state of core collapse, producing vast amounts of energy as stars more massive than the Sun end their lives. Out of such catastrophic events a type of neutron star called a magnetar may be produced, its powerful magnetic field pumping out X-ray and gamma ray radiation. Young, massive stars and regions of active star formation are implicated under this...

Let’s make a quick return to the Magellanics after our recent look at WOH G64, a dying star imaged in the Large Magellanic Cloud (see Close-up of an Extragalactic Star). These satellite galaxies of the Milky Way have long proven useful in helping astronomers study the gravitational interactions that shape them, leading to further understanding of galactic structure. But today I want to focus on the star-forming cluster NGC 346, which presents us with something of a conundrum. Located in the Small Magellanic Cloud some 200,000 light years away, the cluster is massive and particularly lacking in the heavier elements beyond hydrogen and helium. Intensively studied by the Hubble Space Telescope in the mid-2000s, it has become a proxy for much more distant galaxies in the ancient universe, where metals were harder to find. Why, then, did the Hubble data show that while stars in NGC 346 were between 20 and 30 million years old, they were accompanied by planet-forming disks? A new study...

While working on a piece about interstellar migration as a response to the accelerating expansion of the universe for next week, I want to pause a moment on a just announced observation. I’ve always had a fascination with the Magellanics, those satellite galaxies that are so useful to astronomers because their gravitational interactions with the Milky Way render both of them irregular in shape. That triggers waves of star formation and tells us something about how galaxies assemble themselves. The Small Magellanic Cloud (SMC), about 200,000 light years away, shows little structure, while the Large Magellanic (LMC) is a bit more organized but lacks symmetry – no smooth disk apparent there. Image: This beautiful image taken at ESO's Paranal Observatory shows the four Auxiliary Telescopes of the Very Large Telescope (VLT) Array, set against an incredibly starry backdrop on Cerro Paranal in Chile. The Auxiliary Telescopes are each 1.8 metres in diameter and work with the four 8.2-metre...

A quick follow-up to yesterday’s post. The idea of a stream of debris or even large objects like comets or asteroids from another star continues to resonate with me. The odds on identifying such a stream in terms of origin seem stupendous, but the benefits of doing so would be obvious. I notice that another kind of stellar stream is in the news, one involving not debris but entire stars. The Icarus stream is a grouping of stars that seem to have been tidally disrupted by the Milky Way, probably from an earlier encounter between the parent galaxy and a dwarf galaxy. Digging a bit, I learned that we can carry the idea of stellar streams back to the work of Donald Lynden-Bell, who in 1995 proposed the stream concept to explain the long structure or filament of stars evidently tidally stripped from the Sagittarius Dwarf Spheroidal Galaxy, the latter being a satellite galaxy of the Milky Way. The Sgr dSph, as it is known, actually contains four globular clusters within it. It travels a...

In a tantalizing article in The Conversation, Robert Nichol (University of Surrey) offers a look at where new physics might just be emerging in conjunction with the study of dark energy. Nichol is an astronomer and cosmologist deeply experienced in the kind of huge astronomical surveys that help us study mind-boggling questions like how much of the universe is made up of matter, dark matter or dark energy. We’ve assumed we had a pretty good idea of their proportions but a few issues do arise. One of them seems particularly intriguing. Nichol’s article asks whether dark energy, regarded as a constant, may not actually vary over time. That’s quite a thought. The consensus over a universe made up of normal matter (5 percent), dark matter (25 percent) and dark energy (70 percent) came together early in our century, with dark energy taking the role of the cosmological constant Einstein once considered. Although he came to reject the idea, Einstein would doubtless take great interest in...

While I’m immersed in the mechanics of exoplanet detection and speculation about the worlds uncovered by Kepler, TESS and soon, the Roman Space Telescope (not to mention what’s coming with Extremely Large Telescopes), I’m daunted by a single fact. We keep producing great art showing what exoplanets in their multitudes look like, but we can’t actually see them. Or I should say that the few visual images we have captured thus far are less than satisfying blobs of light marking hot young worlds. Please don’t interpret this as in any way downplaying the heroic work of scientists like Anne-Marie Lagrange (LESIA, Observatoire de Paris) on Beta Pictoris b and all the effort that has gone into producing the 70 or so images of exoplanets thus far found. I’m actually just pointing out how difficult seeing an exoplanet close up would be, for the goal of interstellar flight that animates our discussions remains hugely elusive. The work continues, and who knows, maybe in a century we’ll get a...

I’ve reminisced before about crossing Lake George in the Adirondacks in a small boat late one night some years back, when I saw the Milky with the greatest clarity I had ever experienced. Talk about dark skies! That view was not only breathtaking on its own, but it also raised the point about what we can see where. Ponder the cosmic optical background (COB), which sums up everything that has produced light over the history of the universe. The sum of light can be observed with even a small telescope, but the problem is to screen out local sources. No telescope is better placed to do just this than the Long Range Reconnaissance Imager (LORRI) aboard the New Horizons spacecraft. Deep in the Kuiper Belt almost 60 AU from the Sun, the craft has a one-way light time of over eight hours (Voyager 1, by comparison, shows a one-way light time of almost 23 hours at 165 AU). It’s heartening that we’re continuing to keep the Voyagers alive even as the options slowly diminish, but New Horizons is...

Something interesting is going on in the galaxy NGC 6240, some 400 million light years from the Sun in Ophiuchus. Rather than sporting a single supermassive black hole at its center, this galaxy appears to have two, located about 3000 light years from each other. A merger seems likely, or is it? Centauri Dreams regular Don Wilkins returns to his astronomical passion with a look at why multiple supermassive black holes are puzzling scientists and raising questions that may even involve new physics. By Don Wilkins Super massive black holes (SMBH), black holes with a mass exceeding 100,000 solar masses, don’t behave as expected. When these galaxies collide, gas and dust smash into each other forming new stars. Existing stars are too far apart to collide. The two SMBH of the galaxies converge. Intuition foresees the two massive bodies coalescing into a single giant, Figure 1. The Universe, as frequently happens, ignores our intuition. The relevant force is dynamical friction. [1-4] As a...

I hardly need to run through the math to point out how utterly absurd it would be to have two civilizations develop within a few light years of each other at roughly the same time. The notion that we might pick up a SETI signal from a culture more or less like our own fails on almost every level, but especially on the idea of time. A glance at how briefly we have had a technological society makes the point eloquently. We can contrast it to how many aeons Earth has seen since its formation 4.6 billion years ago. Brian Lacki (UC-Berkeley) looked into the matter in detail at a Breakthrough Discuss meeting in 2021. Lacki points out that our use of radio takes up 100,000,000th of the lifespan of the Sun. We must think, he believes, in terms of temporal coincidence, as the graph he presented at the meeting shows. Note the arbitrary placement of a civilization at Centauri B, and others at Centauri A and C, along with our own timeline. The thin line representing our civilization actually...

Put two massive galaxy clusters into collision and you have an astronomical laboratory for the study of dark matter, that much discussed and controversial form of matter that does not interact with light or a magnetic field. We learn about it through its gravitational effects on normal matter. In new work out of Caltech, two such clusters, each of them containing thousands of galaxies, are analyzed as they move through each other. Using data from observations going back decades, the analysis reveals dark and normal matter velocities decoupling as a result of the collision. Collisions on galactic terms have profound effects on the vast stores of gas that lie between individual galaxies, causing the gas to become roiled by the ongoing passage. Counter-intuitively, though, the galaxies themselves are scarcely affected simply because of the distances between them, and for that matter between the individual stars that make up each. We need to keep an eye on work like this because...

Our recent discussions of X-ray beaming to propel interstellar lightsails seem a good segue into Don Wilkins’ thoughts on the Chandra mission. Chandra, of course, is not a deep space probe but an observatory, and a revolutionary one at that, with the capability of working at the X-ray wavelengths that allow us to explore supernovae remnants, pulsars and black holes, as well as making observations that advance our investigation of dark matter and dark energy. This great instrument swims into focus today because it faces a funding challenge that may result in its shutdown. It’s a good time, then, to take a look at what Chandra has given us since launch, and to consider its significance as efforts to save the mission continue. We should get behind this effort. Let's save Chandra. by Don Wilkins On July 23, 1999, the Chandra X-ray Observatory deployed from Space Shuttle Columbia. Chandra along with the Hubble Space Telescope, Spitzer Space Telescope (decommissioned when its liquid helium...

Don’t you love the way the cosmos keeps us from getting too comfortable with our ideas? The Hubble Constant (H0), which tells us about the rate of expansion of the universe, is still a hot issue because observations from both the Hubble Space Telescope and JWST don’t tally with what the European Space Agency’s Planck mission concluded from its data on the Cosmic Microwave Background (CMB). How exactly do we fine tune the standard model of cosmology to make sense of this? The so-called Hubble Tension is hardly the only issue raised by the acquisition of new and better data, although it may be the biggest. All kinds of questions linger about what dark energy is, not to mention dark matter. Of course, challenging observations are hardly limited to cosmology. Dialing down to the stellar level, new work has emerged challenging the way white dwarf stars evolve. Contrary to all expectation, some white dwarfs seem to stop cooling, and can indeed live to a satisfying old age. A white dwarf is...

If individual star systems show us a wide variety of formation scenarios – and we just examined recent ESO work on circumstellar disks in different star-forming regions – the variety in galaxy evolution is even more spectacular. I’m reminded here of an unusual find when my uncle Roland died unexpectedly and I became his executor. Clearing out his house preparatory to sale, I discovered a series of astronomy photographs that he had blown up to huge scale. An image of M31, the great spiral of Andromeda, was fully six feet long and gorgeously mounted. I remembered nights as a child when he would visit from Florida and point out celestial objects for me to observe with my 3-inch reflector. M31, he told me then, was considerably wider than the Moon in the sky. When I checked, I found that Andromeda had an angular size of 3 degrees, as opposed to about half a degree for the Moon. Even so, our spectacular sister galaxy is actually a difficult catch, with only its brighter central region...

A kilonova at the wrong place and time would spell trouble for any lifeforms emerging on a planetary surface. Just how we found out about kilonovae and the conditions that create them, not to mention their hypothesized effects, is the subject of Don Wilkins’ latest, a look at Cold War era surveillance that wound up pushing astronomy’s frontiers. That work now causes us to ponder the formation of an ‘island of stability’ in which exists a set of superheavy element isotopes with unique properties. It also raises interesting questions about our Solar System's history and possible exposure to a nearby event. Based at Washington University in St. Louis, Don’s interest in deep space exploration here probes the formation and structure of matter in processes we’re only beginning to unlock. by Don Wilkins Setting out to discover something on Earth can sometimes reveal an unexpected result from a far more interesting source. As a case in point, consider what happened in August of 1963, when...

I hadn’t intended to return so quickly to the issue of high-redshift galaxies, but SPT0418-47 jibes nicely with last week's piece on 13.5 billion year old galaxies as studied by Penn State’s Joel Leja and colleagues. In that case, the issue was the apparent maturity of these objects at such an early age in the universe. Today’s work, reported in a paper in The Astrophysical Journal Letters, comes from a team led by Bo Peng at Cornell University. It too uses JWST data, in this case targeting a previously unseen galaxy the instrument picked out of the foreground light of galaxy SPT0418-47. In both cases, we’re seeing data that challenge conventional understanding of conditions in this remote era. This is evidence, but of what? Are we wrong about the basics of galaxy formation? Do we need to recalibrate the models we use to understand astrophysics at high-redshift? SPT0418-47 is the galaxy JWST was being used to study, an intriguing subject in its own right. This is an infant galaxy...

When something turns up in astronomical data that contradicts long accepted theory, the way forward is to proceed with caution, keep taking data and try to resolve the tension with older models. That would of course include considering the possibilities of error somewhere in the observations. All that is obvious enough, but a new paper on JWST data on high-redshift galaxies is striking in its implications. Researchers examining this primordial era have found six galaxies, from no more than 500 to 700 million years after the Big Bang, that give the appearance of being massive. We’re looking at light from objects 13.5 billion years old that should be anything but mature, if compact, galaxies. That’s a surprise, and it’s fascinating to see the scrutiny to which these findings have been exposed. The editors of Nature have helpfully made available a peer review file containing back and forth comments between the authors and reviewers that give a jeweler’s eye look at how intricate the...

Some years back, I reminisced in these pages about reading Poul Anderson’s World Without Stars, an intriguing tale first published in 1966 about a starship in intergalactic space that was studying a civilization for whom the word ‘isolation’ must have taken on utterly new meaning. Imagine a star system tens of thousands of light years away from the Milky Way, a place where an entire galaxy is but a rather dim feature in the night sky. Poul Anderson discussed this with Analog editor John Campbell: One point came up which may interest you. Though the galaxy would be a huge object in the sky, covering some 20? of arc, it would not be bright. In fact, I make its luminosity, as far as this planet is concerned, somewhere between 1% and 0.1% of the total sky-glow (stars, zodiacal light, and permanent aurora) on a clear moonless Earth night. Sure, there are a lot of stars there — but they’re an awfully long ways off! For more on galactic brightness, see The Milky Way from a Distance. The...