Archive for the ‘astronomy’ Category

Hubble images show a Neptune moon that may have been repeatedly reborn

February 20th, 2019
Image of a small, rocky body with Neptune in the background.

Enlarge / An artist's concept of the tiny moon Hippocamp. (credit: NASA, ESA, and J. Olmsted)

As the Voyager probes moved through the outer Solar System, they compiled a massive record of discovery. Among the newly found objects and phenomena were a large collection of small moons orbiting Jupiter, Saturn, Uranus, and Neptune. Most of these were beyond the ability of Earth-based hardware to image at the time—we actually had to be there to see them.

Since then, however, improvements in ground-based optics and the existence of the Hubble Space Telescope have enabled us to find a few small bodies that had been missed by the Voyagers, as well as other small objects elsewhere in the Solar System, such as the Kuiper Belt object recently visited by New Horizons. Now, researchers have found a way to use advances in computation to increase what we can do with imaging even further, spotting a tiny new moon at Neptune and possibly spotting another for the first time since Voyager 2 was there.

Finding moons

Given that Neptune has been visited by Voyager 2 and imaged frequently since then, any moons we haven't already spotted are going to be pretty hard to see, presumably because they're some combination of small and/or dim. The simplest way to see them is to increase the exposure time, allowing more opportunity for dim signals to emerge from the noise. This method won't work if there's a bright object nearby, which isn't so much of a problem with the outer planets.

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Posted in astronomy, Hubble, Neptune, planetary science, science | Comments (0)

Aluminum may be key to making exosolar systems with water worlds

February 13th, 2019
Should we expect all the planets of an exosolar system to have similar levels of water?

Enlarge / Should we expect all the planets of an exosolar system to have similar levels of water? (credit: NASA/JPL-Caltech)

Mini-Neptunes. Super-Earths. There's a huge diversity of exoplanets out there, many of them unlike anything we have in our Solar System. So how does a single physical process—the aggregation of bodies within a disk of gas and dust—produce so many different outcomes?

That's a question tackled by a paper in this week's Nature Astronomy. An international team of researchers has modeled the formation of planets early in the history of exosolar systems. And they find it's possible to radically change the water content of planets based on the amount of a radioactive element present in the material forming the exosolar system. The difference, they suggest, can determine whether a system is filled with ocean worlds or whether it winds up looking more like our own Solar System.

Wet or dry?

We already have some idea of what sets the level of water on a planet. The material in a planet-forming disk is heated both by collisions among its material and from the inside-out by the star once it ignites. Different materials will freeze out at specific distances from the star, creating multiple snow lines for water, carbon dioxide, methane, and more. Depending on which side of the snow lines an exoplanet forms, it will have more or less of these materials.

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Posted in astronomy, Physics, planet formation, science | Comments (0)

Inside-out dense iron planets probably the result of massive collision

February 5th, 2019
Inside-out dense iron planets probably the result of massive collision

Enlarge

How violent are the early histories of solar systems? Planets are built by the collisions of smaller bodies, so a certain amount of violence is probably unavoidable. Our own Earth-Moon system seems to have been formed by a smash-up of two planets, while Uranus seems to have been flipped on its side by a collision, and Mercury seems to have lost a lot of its material early in its history. Is this sort of history common as planets form?

Answering these questions requires a detailed understanding of the planets themselves, knowledge difficult to attain for any solar system but our own. But now, following up on observations made with the Kepler space telescope, researchers are suggesting they've found evidence of a smash-up in an exosolar system about 1,750 light years from Earth.

That's dense

Kepler-107 has a Sun-like star orbited by at least four planets. The planets are tightly packed around the star, with orbital periods ranging from three to 14 days. The lengths of the orbits of neighboring planets can be expressed as simple ratios of integers (5:2, 3:1, and so on). This creates what are called "resonant orbits," where the periodic alignment of the bodies helps stabilize and reinforce the orbits. Generally, this is thought to occur when planets that form farther from the star are migrating inward toward it; the resonances help balance things out and keep the planets from continuing on into the star.

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Posted in astronomy, boom, exoplanets, kepler, orbital mechanics, science | Comments (0)

The Earth has been experiencing more frequent asteroid strikes

January 18th, 2019
The craters used for this analysis and their locations.

Enlarge / The craters used for this analysis and their locations. (credit: Dr. A. Parker, Southwest Research Institute)

How often does a big rock drop on our planet from space? As we've gotten a better understanding of the impact that did in the dinosaurs, that knowledge has compelled people to take a serious look at how we might detect and divert asteroids that pose a similar threat of planetary extinction. But something even a tenth of the size of the dinosaur-killer could cause catastrophic damage, as you could easily determine by placing a 15km circle over your favorite metropolitan center.

So, what's the risk of having a collision of that nature? It's actually hard to tell. The easiest way to tell is to look for past impact craters and try to figure out the frequency of these impacts, but the Earth has a habit of erasing evidence. So, instead, a group of scientists figured out a clever way of looking at the Moon, which should have a similar level or risk. And they found that the rate of impacts went up about 300 million years ago.

Erasing history

Some impact craters on Earth are pretty obvious, but erosion and infilling with sediments make others much harder to find. We wouldn't have noticed Chicxulub or the Chesapeake Bay Crater were there if we hadn't stumbled across them for other reasons. As we go back in time, plate tectonics can erase evidence of impacts from the sea floor, as the rock they reside in gets subducted back into the mantle. And then, about 550 million years ago, the Great Unconformity wipes off any evidence of impacts that might have been left on land.

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Posted in asteroids, astronomy, impacts, planetary science, science | Comments (0)

System has four stars and a planet-forming disk oriented vertically

January 17th, 2019
Image of a dust disk surrounding two stars in mutual orbit.

Enlarge / Artist's conception of the B binary in the quad-star system HD 98000. (credit: University of Warwick/Mark Garlick.)

Models and observations indicate that both stars and planets form as a cloud of material collapses into a disk. If the process proceeds in an orderly manner, then the planets will all form from the same disk and thus orbit in the same plane. And—because material from the same disk will fall into the star, brining its momentum with it—the star will rotate with its equator along the same plane. That should lead to a tidy system with the equator of the star lined up with the plane of any planets orbiting it.

Except when it doesn't. Anything that upsets the even inflow of material—from clumping in disk to a passing star—can upset this process. We've seen the results: planet-forming disks and planetary orbits that don't line up with a star's equator.

Now, researchers are reporting a complex, four-star system where a planet-forming disk is lined up perpendicular to the stars, so that it orbits over their poles.

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Posted in astronomy, exosolar systems, planet formation, science | Comments (0)

New Canadian telescope spots a second repeating Fast Radio Burst

January 10th, 2019
Image of a series of metal troughs.

Enlarge / Yes, that's a telescope. (credit: CHIME)

Fast Radio Bursts were discovered about a decade ago and have remained enigmatic since. Over the course of a few milliseconds, something—we have no idea of what—releases a tremendous amount of energy at radio frequencies. With a single exception that launches repeated fast radio bursts, the sources are never heard from again.

When faced with an enigma like this, the standard scientific mantra applies: we need more data. So, in less than a decade, radio telescopes have been designed and built to identify more of these events. The latest entry, CHIME (for Canadian Hydrogen Intensity Mapping Experiment), has only just been built, but its builders started having it do science while still under construction. And CHIME quickly paid off by identifying the closest and lowest-frequency fast radio bursts yet found, along with only the second example of a repeating source.

A CHIME in progress

Just how unfinished was the new telescope? "New racks of compute nodes were being installed and the number of nodes operating, and hence beams on sky, varied from day to day," its scientists say. "Additionally, the number of compute nodes operating in the correlator, and hence the frequency coverage, also varied daily." Things were such that the data for a fast radio burst was lost, leaving scientists with only details from its metadata, like when and roughly where it occurred.

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Posted in astronomy, astrophysics, Canada, fast radio bursts, science | Comments (0)

Milky Way to face a one-two punch of galaxy collisions

January 5th, 2019
Image of a web of blue threads, representing dark matter, and orange galaxies that form along them.

Enlarge / A simulation of galaxies forming in the early Universe. By chance, some of them experience a history that's similar to the Milky Way's. (credit: The EAGLE Project)

If our knowledge of galaxy structures was limited to the Milky Way, we'd get a lot of things wrong. The Milky Way, it turns out, is unusual. It's got a smaller central black hole than other galaxies its size; its halo is also smaller and contains less of the heavier elements. Fortunately, we've now looked at enough other galaxies to know that ours is a bit of an oddball. What's been less clear is why.

Luckily, a recent study provides a likely answer: compared to most galaxies, the Milky Way's had a very quiet 10 billion years or so. But the new study suggests we're only a few billion years from that quiet period coming to an end. A collision with a nearby dwarf galaxy should turn the Milky Way into something more typical looking—just in time to have Andromeda smack into it.

Incoming

The researchers behind the new work, from the UK's Durham University, weren't looking to solve the mysteries of why the Milky Way looks so unusual. Instead, they were intrigued by recent estimates that suggest one of its satellite galaxies might be significantly more massive than thought. A variety of analyses have suggested that the Large Magellanic Cloud has more dark matter than the number of stars it contains would suggest. (Its stellar mass is estimated to only be five percent of the Milky Way's.)

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Posted in astronomy, black holes, galaxy formation, milky way, science | Comments (0)

New Horizons has a successful flyby of the Kuiper Belt’s bowling pin

January 1st, 2019
Image of a blurry bowling pin shape, as well as a drawing of its possible axis of rotation.

Enlarge (credit: NASA/JHUAPL/SwRI; sketch courtesy of James Tuttle Keane)

While people around the world were celebrating the arrival of 2019, people at the Johns Hopkins Applied Physics Laboratory in Maryland were hard at work. Billions of miles away, the New Horizons probe was flying past Ultima Thule, a small object in the Kuiper Belt. By Tuesday morning, the hardware had sent back a status report that indicated the flyby went as planned, and New Horizons now has lots of data from Ultima Thule that it will slowly send back to Earth over the coming months.

While we don't yet have any of the data that will tell us details about this relic of the Solar System's formation, images taken during the approach solved one of the mysteries that had arisen as New Horizons closed in. But one of the key questions—is Ultima Thule one object or two?—remains unanswered.

Prior to New Horizons' arrival at Ultima Thule, researchers obtained images as it eclipsed a background star. These suggested the body was oblong, rather than spherical. Yet, as the spacecraft got closer, it failed to detect any significant changes in brightness, as you'd expect if an oblong body was rotating.

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Posted in astronomy, NASA, New Horizons, planetary science, science, Ultima Thule | Comments (0)

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)