Archive for the ‘astronomy’ Category

Physicists detected gravitational waves from four new black-hole mergers

December 3rd, 2018
Artist's rendering of two merging black holes, producing telltale gravitational wave signatures that were picked up by the LIGO/VIRGO detectors..

Enlarge / Artist's rendering of two merging black holes, producing telltale gravitational wave signatures that were picked up by the LIGO/VIRGO detectors.. (credit: Aurore Simonnet/LIGO-Virgo Collaboration/Sonoma State University)

At a weekend workshop in Maryland, physicists from the LIGO and Virgo collaboration reported four previously unannounced detections of gravitational waves from merging black holes, including the biggest-known black-hole collision to date, roughly 5 billion years ago. That merger resulted in a new black hole that is a whopping 80 times larger than the sun.

All four are part of the first official catalog of gravitational wave events (called the Gravitational Wave Transient Catalog, or GWTC-1), listing all events detected to date. Their addition brings the total number to 11. Two scientific papers on the new findings have been posted to the arXiv preprint repository (here and here), pending publication.

LIGO detects gravitational waves via laser interferometry, using high-powered lasers to measure tiny changes in the distance between two objects positioned kilometers apart. (LIGO has detectors in Hanford, Washington, and in Livingston, Louisiana. A third detector in Italy, Advanced VIRGO, came online in 2016.) On September 14, 2015, at 5:51am EST, both detectors picked up signals within milliseconds of each other for the very first time—direct evidence for two black holes spiraling inward toward each other and merging in a massive collision event that sent powerful shockwaves across spacetime.

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Posted in astronomy, black hole mergers, black holes, gravitational waves, LIGO, neutron stars, Physics, science, VIRGO | Comments (0)

Nailing down the nature of ‘Oumuamua—it’s probably a comet, but…

November 29th, 2018
Image of an extraterrestrial spaceship from the film Close Encounters of the Third Kind.

Enlarge / I mean, maybe, right? Maybe? Probably not, though. Almost certainly not. (credit: Columbia Pictures)

Shortly before Halloween, the chairman of Harvard's astronomy department openly declared that an interstellar object hurtling through our Solar System might just be part of an extraterrestrial craft. And then…crickets.

The astrophysics blog Centauri Dreams broke the story to the cognoscenti three days later. It presented an informed survey of the academic paper which raised this brash possibility, bolstered with quotes and commentary from the paper's co-author (and noted department chair), Avi Loeb. It was well into November before outlets like CNN, Time, and The Washington Post picked up the story, replete with the inevitable sarcastic quotation marks and snarky headlines. The object, named 'Oumuamua, had a number of weird and seemingly contradictory properties; it could be that those properties appear the way they do because our observations weren't all that great. There are also other possibilities.

I read Loeb's paper—which by then had been speedily accepted for publication by the respected Astrophysical Journal. A few days later, Loeb and I sat down for the longest and—by Loeb's own account—the most serious and in-depth interview he's given on this subject. The embedded audio player following the colon at the end of this very sentence features an hour-ish edit of it, including all the highlights:

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Posted in ‘Oumuamua, aliens, astronomy, i'm not saying it was aliens but, NASA, Podcasts, rob reid, science, space | Comments (0)

Scientists spot two massive stars creating a pinwheel of dust

November 20th, 2018
Image of a complex pinwheel-shaped structure.

Enlarge / An image of Apep taken in the infrared. (credit: University of Sydney/European Southern Observatory)

Figuring out what powers the Universe's largest explosions can be a real challenge, as the explosion wipes out evidence of what caused it. Archival data can sometimes provide hints of what was in the area where things went boom, but a lot of the progress we've made comes down to physicists modeling some of the more extreme objects out there and seeing if they can recapitulate the details of the explosion.

That's where we're at with long gamma ray bursts (where "long" in this case means a couple of seconds). We've seen them happen, and astrophysicists have calculated that they could be emitted from a rapidly rotating, massive star. But we don't have a lot of examples of this sort of star to study in order to see if the physics of their explosions match up with our models. Now, a team of researchers thinks it has spotted one that, in combination with a second massive star, created the fantastic-looking pinwheel shown above. But detailed observations of the system suggest that the pinwheel is formed by materials that originated on a single star yet are moving at two different speeds—something we can't explain.

The serpent god

Technically, the new object goes by the absurdly memorable name 2XMM J160050.7–514245. Surveys spotted it because it was an oddity: unusually bright at certain infrared wavelengths. Follow-up observations revealed its sinuous form, which led the researchers to rename it from the "cumbersome" 2XMM J160050.7–514245 to Apep, which is the name of a serpent deity in Egyptian mythology.

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Posted in astronomy, astrophysics, Gamma ray bursts, science, Wolf-Rayet stars | Comments (0)

Enigmatic ridges on Pluto may be the remains of vanished nitrogen glaciers

November 17th, 2018
Image of Pluto's surface.

Enlarge / Washboard terrain fills the basins in the right of this image. (credit: NASA/JHUAPL/SwRI)

As we've gathered more details about the other planets of the Solar System, we've largely managed to explain the geography we've found by drawing analogies to things we're familiar with from Earth. Glaciers and wind-driven erosion produce similar results both here and on Mars, for instance. But further out in the Solar System, the materials involved in the geology change—water ice becomes as hard as rock, and methane and nitrogen freeze—which raises the prospect of some entirely unfamiliar processes.

This week, scientists proposed that some weird terrain found on Pluto could be the product of large fields of nitrogen ice sublimating off into the atmosphere. While this explanation could account for some properties of Pluto's geography, it doesn't explain why the process resulted in a series of parallel ridges.

On the washboard

The strange terrain lies to the northwest of Sputnik Planitia, the heart-shaped plane that dominates the side of Pluto we have the best images of. Called "washboard" or "fluted," the area consists of large numbers of roughly parallel ridges with roughly a kilometer or two separating them. Aside from their appearance and general orientation, these ridges don't seem to have a lot in common. They're discontiguous and don't fill the entire region. They run down slopes and spread across valley floors—in some cases a single ridge will run down a slope and then flatten out. And in several cases, they create a starburst-like pattern on along the walls of craters.

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Posted in astronomy, glaciers, New Horizons, planetary science, Pluto, science | Comments (0)

“Wolf’s jaw” star cluster may have inspired parts of Ragnarok myth

November 16th, 2018
Only the onset of Ragnarok can defeat Hela, the goddess of death, in Marvel's <em>Thor: Ragnarok.</em>

Enlarge / Only the onset of Ragnarok can defeat Hela, the goddess of death, in Marvel's Thor: Ragnarok. (credit: Marvel Studios)

In Norse mythology, Ragnarok is a cataclysmic series of events leading to the death of Odin and his fellow Asgardian gods, and ultimately to the end of the world. Some iconographic details of this mythical apocalypse that emerged around 1000 AD may have been influenced by astronomical events—notably comets and total eclipses.

This is not to say that the myth of Ragnarok originated with such events; rather, they reinforced mythologies that already existed in the popular imagination. That's the central thesis of Johnni Langer, a historian specializing in Old Norse mythology and literature at the Federal University of Paraiba in Brazil. He has outlined his argument in detail in a recent paper (translated from the original Portuguese) in the journal Archeoastronomy and Ancient Technologies.

Langer's analysis is based on the relatively young field of archaeoastronomy: the cultural study of myths, oral narratives, iconographic sources, and other forms of ancient beliefs, with the aim of identifying possible connections with historical observations in astronomy. Both total eclipses and the passage of large comets were theoretically visible in medieval Scandinavia, and there are corresponding direct records of such events in Anglo-Saxon and German chronicles from around the same time period. These could have had a cultural influence on evolving Norse mythology, including the concept of Ragnarok.

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Posted in archaeoastronomy, astronomy, History, Norse mythology, Ragnarok, science | Comments (0)

Sun’s closest solo star may have company

November 14th, 2018
Diagram showing the location of nearby stars.

Enlarge / The position of Barnard's star relative to the Earth and its other neighbors. (credit: IEEC/Science-Wave/Guillem Ramisa)

From the phenomenal success of the Kepler mission and a proliferation of ground-based telescopes, we now know that planets are common in our galaxy. But the methods we've used to detect most of them are biased toward finding large planets that orbit close to their host stars. The farther a planet is, the less its gravity pulls at the star and the less light it blocks out when it passes between that star and Earth. Meanwhile, the focus has shifted to nearby stars, as astronomers have started building a catalog of targets for the next generation of telescopes.

These issues provide an intriguing backdrop for today's announcement that one of the closest stars to Earth has a super-Earth companion. Barnard's star is a red dwarf that is only six light years from our Solar System; only the three stars of the Centauri system are closer. But the new planet orbits far enough from Barnard's star that it had been missed by earlier attempts. The detailed follow-up that spotted it also hints at the possibility of a separate, more distant planet, and both could help inform our models of planet formation.

A new look

Barnard's star has been observed extensively over the years, partly because it's so close, partly because it's a prototypic example of a red dwarf star. These observations have included exoplanet searches, but nothing about the system stood out. But unless you observe a star regularly, there's a chance you won't happen to be looking at critical points in the planet's orbit.

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Posted in astronomy, barnyard's star, exoplanets, science | Comments (0)

Some good came out of 2018: Astronomy photos

November 11th, 2018

While we're big fans of images of the very small, as brought to us by the Nikon Microscopy Competition, we also admire the really big. And each year, that comes courtesy of the Insight Astronomy Photographer of the Year competition. This year's winners were recently announced and have gone on display a the Royal Observatory in Greenwich, UK. But if you can't make it to London, you can get a taste for what you're missing below.

Tommy Eliassen

Astronomy images span a phenomenal range scale, from things that would fit neatly on Earth (like comets or features on local bodies) to the mind-bogglingly large (like stellar nurseries or entire galaxies). And we frequently observe these objects by using wavelengths the human eye can't see. So there's a lot of room for artistic choices about how to make these things both understandable and beautiful. In many cases, this year's winners have also humanized things by placing the night sky in context, framed by other figures admiring it, or nestled among familiar-looking landscapes.

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Hawaiian Supreme Court gives go-ahead to giant telescope

November 1st, 2018
Two large white domes on a barren reddish landscape.

Enlarge / Keck 1 and Keck 2, near the summit of Mauna Kea. (credit: Eric Berger)

The giant volcanoes of Hawaii's Big Island held a special place for the Polynesians who first settled there, with the peak of Mauna Kea being reserved for that society's elite. But in recent years, they've become home to a new kind of elite: some of the best telescopes humanity has designed. For the past several years, those legacies have clashed through a mix of protests, hearings, and legal maneuvers.

Scientists wanted to build one of our next-generation giant telescopes on Mauna Kea and received approval from the state to do so. But native Hawaiians and their supporters, disturbed by the ever-growing population of observatories and poor past stewardship of the mountain, protested and appealed. Now, the state's Supreme Court has issued what appears to be a comprehensive ruling that upholds the latest construction approval from the Board of Land and Natural Resources. This appears to clear the last hurdle astronomers faced before starting construction.

A contentious history

Scientists have been building telescopes with state approval on top of Mauna Kea for decades, despite its significance to the Polynesians who first settled the islands. Over time, however, three trends set the stage for the current controversy. One was that a telescope, once built, tended not to come down, and the people doing the building didn't always plan to keep the hardware unobtrusive or minimize the environmental damages of construction. At the same time, cultural awareness among those who could trace their ancestry to the first Hawaiians increased, as did our knowledge of their political and religious practices. Work on Mauna Kea identified many shrines and features that are of cultural and/or religious significance.

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Posted in 30 meter telescope, astronomy, Hawaii, mauna kea, Policy, science, telescopes | Comments (0)

Atoms may come apart as the Universe’s biggest stars explode

October 24th, 2018
This is what a quark-gluon plasma looks like when you don't have several Suns' worth of mass crushing it back together.

Enlarge / This is what a quark-gluon plasma looks like when you don't have several Suns' worth of mass crushing it back together. (credit: Brookhaven National Lab)

The building blocks of atoms, protons and neutrons, are composed of a collection of particles called quarks and gluons. Shortly after the Big Bang, however, the Universe was too energetic and dense for the quarks and gluons to form stable interactions. Instead, the Universe was filled with a form of matter called a quark-gluon plasma, where the particles could interact with each other promiscuously.

Billions of years later, a bunch of primates figured out how to re-create a quark-gluon plasma by smashing heavy atoms together. It was the first time the material is known to have existed since the Universe's first moments. But a group of astrophysicists is now suggesting that the biggest stars in the Universe also form something like a quark-gluon plasma as they explode, and these researchers use this to explain why we see so many distinct-looking supernovae.

It goes boom

Physical models of stellar explosions have done remarkably well at explaining what we see out in the Universe. They have helped us understand the amount of mass needed before a star will explode (as opposed to forming a white dwarf) and can describe the differences among a number of classes of supernovae. But something rather embarrassing happens as we move on to larger stars. For blue supergiants, with dozens of times the Sun's mass, the models stop exploding.

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Posted in astronomy, astrophysics, gluons, particle physics, quarks, science, supernova | Comments (0)

Conditions like those inside Neptune cause diamond formation

August 27th, 2017

Enlarge / That lovely blue exterior could be hiding a heart of diamond. (credit: NASA)

Carbon, oxygen, and nitrogen are some of the easiest heavier elements to form through fusion. As a result, they’re common in our Solar System, typically found combined with hydrogen to make ammonia, water, and methane. In the gas and ice giants of the outer Solar System, however, these chemicals are placed under extreme pressures, where chemistry starts to get a bit weird. Do these chemicals survive the crushing interiors of these planets?

One intriguing idea is that methane doesn’t survive. As pressure and temperature increase, methane should start condensing into more complex hydrocarbons. Then, as pressures increase further, calculations indicate the hydrogen and carbon should separate out, leaving pure carbon to sink to the depths of these planets. As a result, it’s been hypothesized that, close to their core, planets like Neptune and Uranus have a layer of pure diamond.

While some evidence supporting this theory has surfaced over the years, it’s been hard to precisely replicate the temperatures and pressures found inside the planets. Now, new work done at the SLAC X-ray laser facility supports the idea that these planets are full of diamonds. But the work indicates the diamonds only form at greater depths than we’d previously thought.

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Posted in astronomy, chemistry, diamonds, laser, materials science, planetary science, science | Comments (0)