As we've been talking about the limitations of giant telescopes in recent days -- and a possible solution in David Kipping's idea of a 'terrascope' -- it pays to keep in mind how our ability to collect light has changed over the years. Thus the figure below, which is drawn from a new paper from Daniel Apai and Tom Milster (both at the University of Arizona) and colleagues. Here we see four centuries of evolution for light-collecting power through refracting and reflecting telescopes, with the introduction of segmented mirrors making larger apertures possible. Image: This is Figure 1 from the paper (click to enlarge). Caption: Evolution of light-collecting area of ground-based (blue, green) and space-based (red) telescopes. The evolution is characterized by alternating stages of slow growth (when existing technology is scalable) and pauses (when existing technology cannot be scaled up). The data points represent the installation of the largest telescopes in their era and are connected...

Yesterday I renewed our acquaintance with the idea that large natural objects can stand in for technologies we have previously been engineering into existence. The progression is a natural one. The early telescope work of Hans Lippershey and Galileo Galilei began with small instruments, but both refractor and later reflector designs would grow to enormous size, so that today, even with the best adaptive optics and segmented mirrors working together, we are pushing hard on what can be done. Not to mention the fact that controversies over land use can come into play with gigantic observatory installations, as we've seen recently in Hawaii. The fascination is that there is nothing in physical law to preclude ever increasing segmented mirror instruments, but we have to question their economic realities and their practicality. I think it's a nod to the sheer ingenuity involved in linking seemingly disparate phenomena that David Kipping could turn work on the 'green flash' seen at sunrise...

I'm always fascinated with ideas that do not disrupt the known laws of physics but imply an engineering so vast that it seems to defy practical deployment. Centauri Dreams readers are well aware by now of some of Robert Forward's vast mental constructions, including lightsails in the hundreds of kilometers and enormous lenses in the outer Solar System as big as some US states. But such notions abound in the realm of interstellar thinking. Thus Clifford Singer's ideas on pellet propulsion to a receding starship, which from the mathematical analysis require an accelerator 105 kilometers long, an engineering nightmare. But then, when we reach sizes like these, we might ask ourselves whether we're not overlooking the obvious. When Cornell's Mason Peck went to work on wafer-scale spacecraft, one futuristic notion that occurred to him was to charge swarms of tiny 'sprites' through plasma interactions and use Jupiter's magnetic field as a particle accelerator, pushing the chips to thousands...

Did huge fires several million years ago force a transition from forest to savanna in northeast Africa? It's a tantalizing thought, as such fires have been seen as a possible factor in driving the emergence of bipedalism in our remote ancestors. Adrian Melott (University of Kansas), who looks at the question in a new paper in the Journal of Geology, notes that our precursors would have adapted to such massive changes to their habitat, evolving to support life amidst the abundant grasslands that had replaced their former tree-filled environments. The conjecture about early hominins is receiving a lot of attention, but it plays only a small role in this paper, which focuses on the linkage between supernovae activity and the period in question. Just how do we make the call on a nearby supernova? Melott has been studying the question for some time, and refers back to 2016 studies of ancient seabed deposits of iron-60 isotopes that appeared in Nature. At that time, two supernovae events,...

Couple the beam from a 100 gigawatt laser with a single-layer lightsail and remarkable things can happen. As envisioned by scientists working with Breakthrough Starshot, a highly reflective sail made incredibly thin -- perhaps formed out of graphene and no thicker than a single molecule -- could attain speeds of 20 percent of c. That's good enough to carry a gram-scale payload to the nearest stars, the Alpha Centauri triple system, with a cruise time of 20 years, for a flyby followed by an agonizingly slow but eventually complete data return. A key element in the concept, as we saw yesterday, is the payload, which could take advantage of microminiaturization trends that, assuming they continue, could make a functional spacecraft smaller than a cell phone. The first iterations of such a 'starchip' are being tested. The Starshot work has likewise caught the attention of Bing Zhang, a professor of astrophysics at the University of Nevada, Las Vegas. Working with Kunyang Li (Georgia...

Massive elements can build up in celestial catastrophes like supernovae, with the rapid-, or r-process, producing neutrons at a high rate as elements much heavier than lead or even uranium emerge. But we’re learning that such events happen not just in supernovae but also in neutron star mergers, which are thought to occur only a few times per million years in the Milky Way. A new paper looks at meteorites from the early Solar System to study what the decay of their radioactive isotopes can tell us about the period in which they were created. Such isotopes have half-lives shorter than 100 million years, but we can determine their abundances in the early Solar System through meteorite studies like these. What Szabolcs Márka (Columbia University) and Imre Bartos (University of Florida) have done is to study how two of the short-lived r-process isotopes were produced, using simulations of neutron star mergers in the Milky Way to calculate the abundances of specific radioactive elements....

When it comes to matching what we know of the early universe, as seen in the Cosmic Microwave Background (CMB), with what we see today, astronomers have their work cut out for them. Edwin Hubble could demonstrate that the universe was expanding by studying the redshift of galaxies as they receded, but the rate of that expansion has been controversial. Now we have new work based on data from the Hubble Space Telescope as well as the Araucaria Project (about which more in a moment) that is helping us refine the Hubble constant (H0) to tighten the parameters on how the universe's expansion is accelerating. The result: The universe is expanding some 9 percent faster than we would expect based on observations by the European Space Agency's Planck satellite, which mined data from the CMB from 380,000 years after the Big Bang. Exactly what drives this accelerated expansion -- an enhanced interaction between matter and something we have yet to detect, 'dark' matter, or the as yet unknown...

The publication of a paper called "New Features of Parenago's Discontinuity from Gaia DR1 Data" by V. V. Vityazev and colleagues brought us a new look at an unusual observation. Parenago's Discontinuity refers to the fact that red, cooler stars move faster in the direction of galactic rotation than blue, hotter stars, based on Hipparcos data. But is the phenomenon just a chance, local observation? Fortunately, a much larger dataset from the Gaia mission has now become available, and it is this that the Vityazev paper addresses in terms of Parenago's finding. The following dialogue between Greg Matloff and Alex Tolley goes to work on the Vityazev document. Dr. Matloff has pointed to the Discontinuity as a possible marker of consciousness among low temperature stars, where molecular bonds can form. Could motion be a matter of agency in such stars? Greg explored the idea in his book StarLight, StarBright. Now Alex digs into the Vityazev paper and questions whether Greg is right that his...

About 250 light years away there is a faint object that is on the borderline between brown dwarf and star. Only a tenth of the radius of our Sun, ULAS J224940.13-011236.9 was actually too faint for most telescopes to observe until a huge flare lit it up, turning this L dwarf, among the lowest mass objects that can still be considered a star, 10,000 times brighter than it was before. Very cool compared to the average red dwarf, L dwarfs emit radiation primarily in the infrared. But this story also has to do with visible light, and the question of how such a small object can produce such a powerful explosion. This was a ‘white light’ flare, a type of flare that displays associated brightening in the visible light spectrum. Astronomers believe flares are driven by magnetic energy, the sudden release of which can cause charged particles to heat plasma. In this case the resulting optical, ultraviolet and X-ray radiation was copious. James Jackman, a PhD student in physics at the...

Messier 87, a massive elliptical galaxy in the Virgo cluster, is some 55 million light years from Earth, and even though the black hole at its center has a mass 6.5 billion times that of the Sun, it’s a relatively small object, about the size of our Solar System. Resolving an image of that black hole is, says the University of Arizona’s Dimitrios Psaltis, like “taking a picture of a doughnut placed on the surface of the moon." But the M87 black hole is one of the largest we could see from Earth, making it a natural target for observations, in this case using radio telescopes working at a frequency of 230 GHz, corresponding to a wavelength of 1.3mm. A decade ago, working with Avery Broderick, Harvard's Avi Loeb highlighted the advantages of M87 as an observational target, finding it in many ways preferable to the black hole at the heart of our own Milky Way: M87 provides a promising second target for the emerging millimeter and submillimeter VLBI capability. Its presence in the...

VISTA (Visible and Infrared Survey Telescope for Astronomy) is a near-infrared instrument located at the European Southern Observatory's Paranal site, and is by all accounts the world's largest survey telescope, with extremely wide field of view and sensitive detectors. On the peak next to ESO's Very Large Telescope (VLT), VISTA shares its exceptional viewing conditions using a 4.1-meter primary mirror and a three-tonne camera with 16 infrared detectors. With its time devoted to six surveys ranging from complete southern sky coverage to small patches of sky looking for extremely faint objects, VISTA was bound to come up with interesting data, especially in the survey known as VVV, which stands for VISTA Variables in Via Láctea. Here, astronomers are homing in on regions that are obscured by dust in the bulge and southern Galactic disk, using pulsating RR Lyrae and Cepheid variables as distance indicators, with a focus on microlensing events, eclipsing binaries and pre-main sequence...

Backyard Worlds: Planet 9 is a project worth investigating. Using a database drawn from NASA's Wide-field Infrared Survey Explorer (WISE), Backyard Worlds: Planet 9 is probing the cosmos at infrared wavelengths. Volunteers search the WISE data in a 'citizen science' effort that has already discovered more than 1,000 likely brown dwarfs. Now we have news of an intriguing white dwarf showing apparently multiple rings of gas and dust. A ringed white dwarf isn't unique. In fact, dust and rings have been observed around white dwarfs that were considerably younger than the one in question, J0207. As described in a paper in Astrophysical Journal Letters, the object is about 145 light years away in the constellation Triangulum and is thought to be about 3 billion years old. With a temperature of 5,800 degrees Celsius (10,500 degrees Fahrenheit), J0207 produced a strong infrared signal. Bear in mind that a white dwarf is a remnant, a star left behind when its Sun-like predecessor, running out...

Recently we've talked about 'standard candles,' these being understood as objects in the sky about which we know the total luminosity because of some innate characteristic. Thus the Type 1a supernova, produced in a binary star system as material from a red giant falls onto a white dwarf, causing the smaller star to reach a mass limit and explode. These explosions reach roughly the same peak brightness, allowing astronomers to calculate their distance. Even better known are Cepheid variables, stars whose luminosity and variable pulsation period are linked, so we can measure the pulsation and know the true luminosity. This in turn lets us calculate the distance to the star by comparing what we see against the known true luminosity. This is helpful stuff, and Edwin Hubble used Cepheids in making the calculations that helped him figure out the distance between the Milky Way and Andromeda, which in turn put us on the road to understanding that Andromeda was not a nebula but a galaxy....

Figuring out the shape of things -- where to place what we see in the sky in a 3-D representation -- has always been challenging. We're looking out at a disk of stars from well within it, and it wasn't until the 1920s and the work of Edwin Hubble that we began to see there were other such disks, not nebulae at all but galaxies in their own right, some bigger than ours. Interestingly, Immanuel Kant had speculated about this as far back as 1755. About our own galaxy, we still have much to learn, as I am once again reminded by a paper by authors from Macquarie University (Australia) and the Chinese Academy of Sciences. The Milky Way turns out to be not as flat as many depictions would have us believe. In fact, our galaxy shows distinct signs of warping, a spiral pattern that appears to be the result of torque produced by the Milky Way's massive inner disk of closely packed stars. In the outer regions of the galaxy's neutral hydrogen disk, the warp becomes readily apparent. We wind up...

The rate of star formation in our galaxy is about two new stars per year, a sedate pace that may play its role in the emergence of life. A new study out of Australian National University looks at the factors that can slow star formation, particularly in galaxies and star clusters still young enough to contain large amounts of dusty gas. What ANU's Roland Crocker and colleagues want to determine is an upper limit on how quickly stars can form in any giant gas cloud. It's an issue because conditions inside a tightly bound cluster could be inimical to life. Consider RMC 136, a concentration of stars at the heart of the Tarantula Nebula in the Large Magellanic Cloud. Here we have a cluster with an estimated mass of 450,000 solar masses, with a central concentration about 2 parsecs across. Star formation in this tightly crowded part of the cluster NGC 2070 is intense, but the tight quarters might turn out to be a serious issue. "If star formation happened rapidly, all stars would be bound...

The first interstellar object detected in our own Solar System, 'Oumuamua has a pleasing name, translating from the Hawaiian as something like 'far visitor first to arrive,' or words to that effect. It's also proven a frustrating catch ever since detected by the University of Hawaii's Pan-STARRS 1 telescope on Haleakala, Hawaii during a search for near-Earth asteroids. We've put telescope resources on Earth and in space on the object, but our observing time is up. For 'Oumuamua is now well on its way out of the Solar System, so we're left to massage the data we have in hopes of gaining new insights. Davide Farnocchia (Center for Near Earth Object Studies, JPL) encapsulates the issue: "Usually, if we get a measurement from a comet that's kind of weird, we go back and measure it again until we understand what we're seeing. But this one is gone forever; we probably know as much about it as we're ever going to know." Thus Avi Loeb's recent paper with Shmuel Bialy discussing the object's...

If you’ve given some thought to the Fermi question lately -- and reading Milan ?irkovi?’s The Great Silence, I’ve been thinking about it quite a bit -- then today’s story about an ancient star is of particular note. Fermi, you’ll recall, famously wanted to know why we didn’t see other civilizations, given the apparent potential for our galaxy to produce life elsewhere. Now a paper in The Astrophysical Journal adds punch to the question by making the case that the part of the galaxy in which we reside may be older than we have thought. Finding that our Sun is younger than many nearby stars, an issue that Charles Lineweaver (Australian National University), among others, has examined, would allow even more time for civilizations to have emerged in the galactic neighborhood. But let’s now leave Fermi behind to look at the tiny star that prompts these ruminations (and to be sure, the paper on this star makes no mention of Fermi, but does tell us something quite interesting about the...

Long-time Centauri Dreams readers know that I love things that challenge our sense of scale, the kind of comparison that, for example, tells us that if we traveled the distance from the Earth to the Sun, we would have to repeat that distance 268,770 times just to reach the nearest star. It’s much simpler, of course, to say that Proxima Centauri is 4.25 light years from us, but it’s the relating of distances to things that are closer to us that gets across scale, especially for those who are just beginning their astronomical explorations. And I have to admit that the scales involved in going interstellar still pull me up short at times when I ponder them. So how about this for scale: We have somewhere between 200 billion and 300 billion stars in our galaxy (the number is flexible enough that you’ll see a wide range in the literature). Relate that to the Local Group, the gathering of galaxies that includes both the Milky Way and M31, the Andromeda Galaxy. These are the two most massive...

These days we take in data at such a clip that a mission like New Horizons will generate papers for decades. The same holds true for our burgeoning databanks of astronomical objects observed from the ground. So it only makes sense that we begin to recover older datasets, in this case the abundant imagery -- photographs, radio maps, telescopic observations -- collected in the pre-digital archives of scientific journals. The citizen science project goes by the name Astronomy Rewind, and it's actively resurrecting older images for comparison with new data. Launched in 2017, Astronomy Rewind originally classified scans in three categories: 1) single images with coordinate axes; 2) multiple images with such axes; and 3) single or multiple images without such axes. On October 9, the next phase of the project launched, in which visitors to the site can use available coordinate axes or other arrows, captions and rulers to work out the precise location of each image on the sky and fix its...

The much discussed interstellar wanderer called 'Oumuamua made but a brief pass through our Solar System, and was only discovered on the way out in October of last year. Since then, the question of where the intriguing interloper comes from has been the object of considerable study. This is, after all, the first object known to be from another star observed in our system. Today we learn that a team of astronomers led by Coryn Bailer-Jones (Max Planck Institute for Astronomy) has been able to put Gaia data and other resources to work on the problem. The result: Four candidate stars identified as possible home systems for ‘Oumuamua. None of these identifications is remotely conclusive, as the researchers make clear. The significance of the work is in the process, which will be expanded as still more data become available from the Gaia mission. So in a way this is a preview of a much larger search to come. What we are dealing with is the reconstruction of ‘Oumuamua’s motion before it...