Daily Archives: June 1, 2017

Our sun was still dim. Waves crashed on martian beaches. Life was emerging on Earth.

Thats when the ghosts of two dead stars black holes dozens of times more massive than our sun merged in a far-off corner of the universe. In their final moments, these binary black holes were circling each other hundreds of times per second, as each one spun at 10 times that rate.

The rumbles of distant thunder from that collision reached Earth on Jan. 4 of this year, passing through the detector at the Laser Interferometer Gravitational-Wave Observatory (LIGO) in Hanford, Washington. Then, traveling at the speed of light, this wrinkle in space-time passed through LIGOs second detector in Livingston, Louisiana, just a fraction of a second later.

The results were published Thursday in the journalPhysical Review Letters.

Gravity is the weakest among natures four fundamental forces. So only extreme cosmic events like supernovas, neutron stars and merging black holes can make detectable gravitational waves. The waves are so weak that theyd warp the distance between Earth and sun by just the width of a hydrogen atom. But as these waves pass through LIGOs twin detectors, its enormous lasers can pick up on the truly tiny stretches and squeezes of space-time. You can think of it like a seismometer for measuring mini quakes in the cosmos gravitational fabric.

When LIGO gets a hit, the gravitational wave makes a characteristic signal that scientists call a chirp because of the sound it makes once translated into a format human ears can hear.

This was the third such detection since Albert Einstein first predicted gravitational waves a century ago as part of his general theory of relativity, or theory of gravity. Taken together, these observations form the first samples of a black hole census with far-reaching implications.

Before colliding, the binary black holes spotted earlier this year weighed in at 19 and 31 times our suns mass. After merging, the pair created a single black hole 49 times more massive than the sun. Einsteins equations tell us that energy and mass are interchangeable. And so the missing solar mass worth of energy was radiated out across the universe as gravitational waves.

And with this detection, scientists for the first time think the two black holes might have been spinning in opposite directions. That could reveal clues about the lives of the stars that formed them. Its possible that the two stars lived in a dense stellar cluster.

Before LIGO, astronomers didnt know that so-called solar mass black holes, which form when stars die, could reach such extreme sizes.

This census can also help explain an enduring mystery in astronomy. Scientists have seen supermassive black holes that dominate entire galaxies, as well as small black holes that form after stars die. We even now know about so-called intermediate mass black holes weighing as much as thousands of suns. But how do these all form? Do many small black holes combine intro larger and larger behemoths? LIGO is just starting to piece together this puzzle.

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3rd gravitational wave detection is about much more than black holes - Astronomy Magazine

When researchers want to take pictures of very small things, like individual molecules, they have to get creative.

When scales shrink to seemingly imperceivable levels, images must be captured usingindirect techniques that record how the subject being photographed interacts with its environment. One way to do this is byobserving how a beam of particles disperses around the object. Working backward, researchers can then infer what the object in question looks like.

The particle beams that do the heavy lifting for this kind of imaging require sophisticated equipment to create. At theSLAC National Accelerator Laboratoryat Stanford University, their linear accelerator stretches out for two miles, focusing beams of charged electrons onto minuscule targets at extremely intense energies. In apaperpublished Tuesday inNature,SLAC researchers observed peculiar behavior among atoms subjected to their X-ray beam, and theyre calling it a molecular black hole.

TheLinac Coherent Light Source (LCLS) at SLAC is used to take pictures of organic molecules and biological processes that take place at scales of only a few atoms. Abeam of electrons bounces off the molecules in a predictable way, giving researchers an idea of their structure. This happens in the brief instant before the sample is destroyed by the electron beams intense energy, something the researchers call diffraction before destruction. Understanding how the molecules behave as the beam passes through is critical to obtaining precise measurements.

Working with atoms of xenon and molecules containing iodine atoms, the researchers saw something unexpected occur. The beam ripped through the outer shells of the atoms and stripped away the innermost electrons, leaving a gaping void between the nucleus and the outer electrons. The overwhelmingly positive charge this created then sucked in all of the surrounding electrons with enough strength to not only gather its own electrons, but also steal them away from surrounding atoms.

As predicted by the laws of physics, this kind of electron theft doesnt happen in nature because the forcesinvolved are too great. Done fast enough, and with enough power, however, the naked nuclei overwhelm the grip of neighboring atoms and siphon off electrons, in a process, the researchers say, that is similar to a black hole consuming a star.

When we have really,really intenseXrays like we do theres enoughXrays that you knock outone electron andbefore theres time for recombination youknock off anotherand then knock offanother and so on and so forth, saysLCLS staff scientist and study co-author Sebastien Boutet. What that endsup doing is stripping most of the inner shells and then that very highly chargedmolecule unexpectedly suckedin a bunch of electrons from neighboring atoms as a consequence.

The molecular versiondoesnt work the same way as a cosmic black hole, which relies on immense gravitational forces to suck in matter, but the observed effect is similar. Understanding how the beam interacts with atoms of this size, which often show up in their experiments, will help researchers fine-tune their images. The accelerator is currently undergoing an upgrade which will allow for a drastic increase in the number of beam pulses per second, expanding the machines imaging capacity.

The more precision researchers can achievewhile working at scales of just a few hundred nanometers, the more they will see.

This article originally appeared on Discover.

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X-ray blast produces a 'molecular black hole' - Astronomy Magazine

SPECIAL TO THE ORACLE

From the twinkling lights of the stars to the glow of a full moon, students have the opportunity to enjoy the heavens with the astronomy club at Riverfront Park.

All students are welcome as prior knowledge of astronomy is not required.

It doesnt matter if youre a physics major, it doesnt matter if you have an astronomy minor, it doesnt matter if youre not a (science, technology, engineering and mathematics) major, said Kyle Denny, a junior majoring in physics and president of the astronomy club. You could be anything and you could come join the astronomy club. It is open to anyone who just wants to connect and learn about the universe and appreciate it.

We do a lot of events, too, when planets are in opposition, said Kami Malestein, a junior majoring in physics and astronomy club vice president.

The astronomy club hosts many activities such as stargazing, full moon watching and eclipse viewing. Students with telescopes or binoculars are encouraged to bring them.

One of Dennys favorite events was Mercurys transit in May of last year.

We watched the planet Mercury go in front of the sun, Denny said. we had a great turnout for that one.

The number of students at an event varies from five to 10 people on stormy nights to a hundred for occurrences such as the Mercury transit.

An even larger turnout is expected for the upcoming solar eclipse on Aug. 21 the viewing location on campus is yet to be determined.

Although it wont be a total eclipse visible over USF, there will be a partial phase. Eighty percent of the sun will be blocked out, and itll be on the very first day of school, Denny said. People are going to stop by and wonder whats going on with the sun, so they get a chance to look at the sun in a really spectacular event.

Most of the clubs events take place at Withlacoochee River Park or Riverfront Park, with transportation through students driving themselves or joining a carpooling list.

The astronomy club is one of a few clubs that remain active during the summer. Their next event is scheduled for the next full moon June 9 at Riverfront Park.

The times that there are not thunderstorms, the Milky Way is nice and prominent in the night sky. You can see it from horizon to horizon, Denny said. Its a really inspiring experience. So, the summer is probably the best time to really look up at the night sky and really appreciate it.

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Astronomy club to host full moon viewing - The Oracle

The University of the Virgin Islands College of Science and Mathematics, together with the Etelman Observatory, are organizing two upcoming astronomy conferences this summer. The first one, Generation-GW: Diving into Gravitational Waves will take place from June 5-9. The second conference, Unveiling the Physics Behind Extreme AGN Variability will take place from July 11-14. Both conferences will facilitate discussions about crucial breakthroughs in the field of astronomy over the last few years.

We are establishing a legacy, and these events will improve the recruitment of Virgin Islands students to study physics and astronomy at UVI, said Dr. Antonino Cucchiara, assistant professor of physics. The conferences will also demonstrate how research and activities undertaken at UVI can benefit the community.

The scientific breakthrough to be discussed by groups of international astrophysicists from around the world at the June conference is Gravitational Waves. Widely considered to be the greatest discovery of 21st century astronomy, this phenomenon describes ripples in the curvature of space-time that propagate at the speed of light, outward from their source.

The other discovery to be discussed by more than 50 astronomers at the July conference is Fast Variable Active Galactic Nuclei (AGN). The center of every galaxy has a super massive black hole which is millions of times heavier than our sun. Everything that gets too close to it or falls in is destroyed, explained Cucchiara. That destruction produces energy that is observable in optical, X-ray, gamma-ray radiation producing an AGN. The July conference will focus on Fast Variable AGNs, which radiation changes quickly in time and are therefore difficult to observe in detail.

Both conferences will include an undergraduate mentoring component with question and answer sessions, as well as a talk that will be open to the public. The public talk for the June conference is set for 7 p.m. on Thursday, June 8, in the Administration and Conference Center (ACC). It will feature Professor Alberto Sesana from the University of Birmingham in the United Kingdom, and Professor Jillian Bellovary from Queensborough Community College in New York. The public talk in July will also be held on a Thursday; details to be announced.

UVI and the Etelman Observatory are establishing a path forward to become an astronomy research hub, said Cucchiara. It is important for us to involve not just UVI physics faculty, but also international partners, undergraduate researchers and federal agencies. Eight UVI students will be at the National Aeronautics and Space Administration (NASA) working on a variety of projects, from building the new generation of microsatellite, to studying planets around other stars, to studying the most powerful stellar explosions known in the Universe. Some of these projects relate to research that is currently being pursued at UVI, representing the strong connection between both institutions.

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UVI To Host Two Astronomy Conferences Showcasing Major Discoveries - VI Consortium (press release)

[Artist's conception of a black with material swirling around it in an accretion disk, and also a jet of matter blasting away from it. Until recently, it was thought that a star had to supernova to create a black hole, but evidence is mounting it may not. Credit:NASA/JPL-Caltech]

One of the basic truisms in astronomy is that, when a massive star ends its life, it goes out with a bang. A big one. A supernova.

This titanic explosion is triggered when the star runs out of nuclear fuel in its core. The core collapses in a heartbeat, and the energy generated in that collapse is so immense that it blows the outer layers off. This explosion is so colossal it can outshine an entire galaxy! In the meantime,the collapsed core can form an exotic neutron star, or may even squeeze itself down into a black hole.

Now, Ive skipped some steps there, but thats the general picture (if you want more, check out my Crash Course Astronomy episode on high mass stars and supernovae). If you want a black hole, you have to blow up a massive star.

Except, maybe not. It turns out theres a loophole that could allow a star to bypass the supernova part. It collapses directly down to a black hole without the explosion. Some energy is released, but not much compared to a supernova, and in the end what you get is a now-you-see-it-now-you-dont situation: The star is there, and then suddenly ... it isnt.

The idea of a failed supernova is an interesting theoretical astrophysical problem, and one scientists have been working on for a while now. But theres been a new an exciting development: Astronomers now think theyve seen one!

The star in question is called N6946-BH1, and it was found in a very cool survey specifically designed to look for failed supernovae. Using the Large Binocular Telescope in Arizona, 27 galaxies all within about 30 million light-years of Earth were observed over and over again. Each image was painstakingly compared to the others to look for transients: objects that have changed brightness. Even using rather stringent criteria, thousands were found stars change brightness for a lot of reasons,but most are not due to them going supernova ... or, in this case, failing to supernova.

Eventually,the number of interesting objects was whittled down to just 15. Six of them turned out to be run-of-the-mill exploding stars (if the titanic explosion of a few octillion tons of star screaming outward at a substantial fraction of the speed of light can be called ho-hum), but nine of them turned out to be more interesting.

Of these, all but one were likely unusual events, like two stars merging, which can cause a very big (and very pretty) eruption, but again falls short of the outcome of a massive star dying. When all was said and done, after searching 27 galaxies for seven years, only one object was left: N6946-BH1.

In earlier images, the star is there, clearly seen in the galaxy NGC 6946, a lovely face-on spiral galaxy roughly 20 million light-years away (and one that has had no fewer than 10 recorded supernovae in the past century; by coincidence one was seen just this year). Then, in later images, its gone. Like, gone: Disappeared. Poof.

If it had exploded as a supernova it wouldve been seen in the images. Instead, in 2009, it briefly got somewhat brighter, glowing at about a million times brighter than the Sun; then it faded so much it was only about 2% of its previous brightness (that is, pre-collapse) by 2015. And yes, in human terms, a million times the Suns luminosity is terrifyingly bright, but in terms of a supernova, its barely worth mentioning; a typical one will shine many billions of times brighter than the Sun! So this was, at best, a bit of a pop.

So, how do we know it wasnt some sort of weird supernova, maybe obscured by lots of dust in the host galaxy? This material is dark and opaque, and can completely block the light from even a normal supernova. Follow-up observations using Spitzer Space Telescope should reveal that, because infrared light can pierce through the dust. Spitzer did see some IR light from the event, roughly 20003000 times the Suns luminosity. Again, thats a lot, but nowhere near what youd expect from a supernova. Even a stellar merger would produce more than that.

It really looks like whats left is what the astronomers had been looking for all along: a failed supernova.

If true, this is very interesting, indeed. Why? Because of physics.

It takes a massive star to explode; it has to have enough pressure in the core (caused by the mass of the star above it squeezing down on it) to fuse successively heavier elements over time. First,hydrogen fuses into helium.Then, when that runs out, helium is fused into carbon, and so on, until the core builds up iron. When iron fuses, it doesnt release energy; it absorbs it. Thats a big problem, because its that release of fusion energy that holds the star up (in a similar fashion that hot air causes a balloon to expand). Once the star tries to fuse iron, the core collapses. If the core has a mass up to about 2.8 times that mass of the Sun, it forms a neutron star, but if it has more, it forms a black hole.

And in general, either way, the core collapse triggers the supernova in the outer layers, and kaboom.

But thats where this gets funny. It may not always happen that way. For a range of core masses, theoretical calculations show that the explosion may stall. The outer layers get a decent kick, but not a huge one. They blow off, but its a more gentle event than the unfettered violence of a supernova.

That depends on a lot of factors, actually, but it tends to happen when the total star mass is roughly 25 times that of the Sun. Looking at the observations of N6946-BH1, thats just about the mass it had.

And theres more. We see lots of high-mass stars in galaxies being born, but there arent enough supernovae seen to account for them all. That implies failed supernovae happen relatively often.

Also, when we look at the masses of neutron stars and black holes, we find theres a gap between them; the lowest-mass black holes are still considerably more massive than the highest-mass neutron stars. If all these compact objects formed from regular supernovae, youd expect there to be a smooth transition. Thats because, in a supernova, a lot of the material in the star still lingers near the core, and that can fall back on the newly formed neutron star. If theres enough, the neutron star will then collapse to form a low-mass black hole. So youd expect to see lots of black holes right at the lower mass limit. But we dont.

Ah, but in the failed supernova scenario, theres a lot more material left over there wasnt enough energy in the event to blow away all the outer layers. This comes crashing back down and adds its mass to the neutron stars, making a far more massive black hole. So, in reality, the existence of failed supernovae explains a lot of different phenomena.

And now, very likely, weve seen one! More observations would be nice, though. For example, a newly formed black hole should emit lots of X-rays, as material heats up before falling in. If we see those X-rays, that would go a long way in understanding what were seeing.

And again, this is the first one that weve seen. Given the number of supernovae that were detected in the survey, it implies that something like 14% of all high-mass star deaths result in failed supernovae. If thats the case, then we need more eyes on the sky looking for these events. Supernovae are what create and distribute elements literally vital to our existence: iron, calcium and more. Without them, you and I would literally not exist.

In my opinion, that makes these events very much worthy of our study. Even when they fail.

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Bad Astronomy | Astronomers may have seen a star collapse directly ... - Blastr