Category Archives: Astronomy

When stars are swallowed by a supermassive black hole, do they go out like a candle or crash into a solid surface? The first option upholds general relativity as is, while the second relies on a modified version of this famous theory. Now, a group of astronomers has found a way to study what happens at a black holes event horizon, even though there are no images of this region of space. Their findings? General relativity is safe.

Pawan Kumar of The University of Texas at Austin, along with his graduate student Wenbin Lu and colleague Ramesh Narayan of the Harvard-Smithsonian Center for Astrophysics, found a unique way to determine just what happens to stars as they approach extremely massive objects i.e., black holes. Their results are published in Monthly Notices of the Royal Astronomical Society.

Nearly every galaxy in the universe, including our own, has a central massive object at its center. These massive objects are assumed to be supermassive black holes several millions or even billions of times the mass of our Sun. This is because according to general relativity, objects of a certain mass cannot be held up by any known force, and thus collapse into black holes.

Black holes are singularities with no physical surface area, surrounded by an event horizon. The event horizon acts like a one-way membrane material can fall in toward the black hole, but once it passes the event horizon, it can no longer send out light that is visible to the rest of the universe because the gravity of the black hole pulls the light back toward itself. Once past the event horizon, the material, in essence, disappears from view.

But what if general relativity isnt quite right? What if, instead, these central massive objects arent collapsed down to a point? If that were the case, the event horizon would have different properties. Kumar and his colleagues theorized that if the central massive object is not a black hole, then the event horizon would not act like a one-way membrane, but like some kind of solid surface against which any infalling material would smash. This would produce a visible effect as the infalling stars gas lit up as a result of the collision, enveloping the massive object and glowing visibly for months or even years.

Our whole point here is to turn this idea of an event horizon into an experimental science, and find out if event horizons really do exist or not, said Kumar in a press release announcing their results.

To test these competing ideas, the team turned to observations taken with the 1.8-meter Pan-STARRS telescope in Hawaii over the course of 3.5 years. By calculating how many stars should fall onto supermassive black holes in the nearby universe, the group could determine how many events they should see over the course of the 3.5 years the survey was active. If they saw signs of this theorized glow, it would signal that the event horizon was solid; if not, it would mean that general relativity is correct, and stars simply pass the event horizon and go dark.

Given the rate of stars falling onto black holes and the number density of black holes in the nearby universe, we calculated how many such transients Pan-STARRS should have detected over a period of operation of 3.5 years. It turns out it should have detected more than 10 of them, if the hard-surface theory is true, explained Lu.

Why is there any debate at all? Currently, telescopes are not able to resolve the region immediately around a compact object to directly observe the event horizon and its properties. But astronomers are continually pushing the boundaries of their instruments, seeking better, closer-in images of black holes.

The Event Horizon Telescope, a combination of several observatories, made its first observations of the area surrounding a supermassive black hole in April, though these data are still undergoing image processing and evaluation.

The Large Synoptic Survey Telescope, currently under construction, will perform surveys like those taken with the Pan-STARRS telescope, but with significantly greater sensitivity to events like the glow that would be left behind by collisions with a solid surface event horizon.

Because of this lack of direct evidence, the event horizon has remained mysterious in nature. And according to Kumar, Our motive is not so much to establish that there is a hard surface, but to push the boundary of knowledge and find concrete evidence that really, there is an event horizon around black holes.

After poring through the data returned from the Pan-STARRS telescope, Kumars group found no afterglow signature of any collisions.

In this case, a lack of signal is a good thing, if you support general relativity. Said Narayan, Our work implies that some, and perhaps all, black holes have event horizons and that material really does disappear from the observable universe when pulled into these exotic objects, as weve expected for decades. General relativity has passed another critical test.

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How do stars die when they fall into a supermassive black hole? - Astronomy Magazine

ALBERT LEA An Albert Lea High School educator is determined to spread the word about a total solar eclipse that will confuse nature at the end of summer.

On the first day of school this coming fall, Ken Fiscus, an earth and energy science teacher, will not be in school. He will be en route to a better view of the Great American Eclipse.

It is finally here, Fiscus said. The educator has not seen a total solar eclipse in 19 years.

Fiscus will travel to Pawnee County, Nebraska, where he grew up, to feast his eyes on the solar event at 1:03 p.m. Central Time on Aug. 21.

The 2017 total eclipse will only be visible for two minutes and 35 seconds.

A total eclipse, as Fiscus explained Tuesday night at the ALHS auditorium to a group of astronomy enthusiasts, is when the sun is completely blocked by Earths orbiting moon. This happens when the moon passes between the Earth and the sun at the exact right moment and angle, thereby totally or partially blocking someone on Earths view of the sun.

A total eclipse has not been visible from the United States since 1998 and after the Aug. 21 event, a total eclipse will not be visible again from the United States until 2024, Fiscus explained.

Fiscus has only seen two other total solar eclipses in his lifetime as an astronomy enthusiast. He traveled to Mexico in 1991 and Aruba in 1998 to see the rare events.

Albert Lea and its surrounding communities will not be as greatly affected by the solar event as some other Americans.

A total eclipse can only be seen from a certain strip of the United States. The strip is about 70 miles wide and will stretch from Oregon on the West Coast to South Carolina on the East Coast.

The closer people travel to the center of the strip, the darker the sky will become and the more vibrant and longer the eclipse will be, Fiscus said.

In Albert Lea, Fiscus explained that on the day of the total eclipse, the sky will be an odd blue color that people have not seen before. He said colors will seem more saturated in natural light, shimmering lines will cover the ground, contrast will be greater to the eye, shadows will be extremely crisp and the temperature will drop.

During a total eclipse, daytime instantly becomes a dark twilight and only the suns rays, or corona, is visible. The darkness that falls over the Earth during a total eclipse travels at the speed of a bullet, Fiscus said. The corona, or crown of the sun, shimmers bright in the night sky.

Fiscus explained that the sky in Albert Lea will not be as dark as certain parts of the country.

This instant darkness confuses nature Fiscus said he hopes someone brings a rooster to the event so he can hear a rooster crow in the middle of the afternoon.

Animals and people alike will be astounded by the beauty of the event, Fiscus outlined in his presentation.

During the total eclipse that Fiscus witnessed in Mexico in 1991, Fiscus said that even the dolphins surrounding the cruise ship were confused by nature. In Aruba in 1998, divers specifically traveled to the eclipse event to watch the state of confusion for animals underneath the surface of the water.

There are different types of eclipses, Fiscus said, however, the total eclipse is the most rare.

More information about the eclipse or traveling to view the eclipse can be found at eclipse2017.org.

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Astronomy enthusiast gears up for total solar eclipse - Southernminn.com

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

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

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

Astronomers from around the world, including South Africa, will attempt to study the rings of an exoplanet orbiting a star 63.4 light years away from earth.

The international programme, being conducted between April 2017 and January 2018, would have astronomers observing Beta Pictoris, the second brightest star in the constellation Pictor.

Beta Pictoris is a star visible to the naked eye that has a large planet orbiting around it, explained Dr Steve Crawford from the South African Large Telescope (SALT), who spoke about South Africas involvement in the 200-day observation at the South African Astronomical Observatory (SAAO) in Observatory, Cape Town, on Saturday.

This year the planet is expected to pass nearly in front of the star. If there are rings around the planet, we will have an excellent chance to detect them with how closely the planet is passing in front of the star.

According to Crawford, Beta Pictoris was still a young star and could give astronomers a glimpse of what the early solar system may have been like.

In particular, this might give us a chance to study how moons form around a planet which is a process that is not very well understood yet, explained Crawford.

In 1981, the brightness of Beta Pictoris diminished, which made astronomers think there must have been a huge object passing in front of the star, then the giant planet Pictoris b, was discovered in 2008.

We are hosting one of the telescopes at the Sutherland Observatory of the SAAO, said Crawford.

A small robotic all-sky monitor with two camera systems, named the Beta Pictoris b Ring project, would be dedicated to looking at Beta Pictoris at SAAO, in Sutherland, in the Northern Cape.

The b Ring monitor would take images, which would be analysed on a set of computers. If a change in brightness was detected, it would allow the triggering of a host of observations using larger telescopes and more advanced instrumentation to study the details of the suspected ring system in-depth.

University of Cape Town PhD student, Blaine Lomberg, would be responsible for the SALT spectroscopic follow-up if anything was detected.

If we detect a change in the flux coming from Beta Pictoris, it would trigger follow-up observations from a number of different observatories including SALT.

We are hoping to use the follow-up observations to determine the characteristics of the rings, like what they are composed of, said Crawford.

Crawford further explained that the area immediately around the vicinity of the planet would only take 2.5 days to cross in front of the star, but the total area where rings might be detected would take 270 days to pass in front of the star.

So we want to monitor over a full year to see if we detect any other changes due to the planet transiting the star, said Crawford.

The project was being led by Matt Kenworthy from Leiden University in the Netherlands, and the team also included a United States group that would be installing another monitoring station in Australia.

According to the National Aeronautical and Space Administration in the United States, more than 3,000 exoplanets (planets outside the solar system) have been discovered since 1988.

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South Africa participates in international astronomy programme - Creamer Media's Engineering News

On Friday evening, youll have the opportunity to see a few of our neighboring planets as well as the moon and the sunon through the lens of 20 expensive telescopes that you and I cannot afford. Fortunately, the D.C. area astronomers are willing to share, as they do every year at the annual Astronomy Night on the Mall.

The event is free Friday from 6 to 11 p.m. All you have to do is show up on the northeast grounds of the Washington Monument. Youll see a lot of telescopes with lines of people trailing behind them. Each scope is usually trained on a specificspace object another planet, the moon, maybe a nearby comet.

The event will offerspace geeks hands-on activities, demonstrations, hand-outs, posters, banners, and videos; a planetarium show with a portable blow-up dome, speakers from scientific and educational organization, and a chance to mingle with astronomers.

The event is organized and hosted by Hofstra Universityalong with volunteers from all of the big science organizations the National Science Foundation, the Carnegie Institution for Science, the International Dark Sky Association, the American Association for the Advancement of Science, the Northern Virginia Astronomy Club and the American Geophysical Union. Scientists from these groups will be on hand tooffer demonstrations and discussion.

This is theeighth annual Mall event that organizer Don Lubowich, astronomy outreach coordinator at Hofstra University, Hempstead, N.Y., has assembled.

Rain location: School Without Walls High School, 2130 G St. NW.

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Space geeks: Astronomy Night on the Mall is Friday and it's free - Washington Post

Lia Halloran's exhibit "Your Body is a Space That Sees Us" features paintings and cyanotypes of cosmic objects in round frames. This is the largest piece in the exhibit, and is more than 10 feet wide.

Visual artist Lia Halloran's newest exhibit, "Your Body is a Space That Sees Us," features large-scale paintings of astronomical objects that were photographed and catalogued by women working at the Harvard Observatory in the late 1800s.

Those women, along with their male colleagues, took thousands of photographs, catalogued and characterized the cosmic objects therein, and changed the landscape of space science. Despite the impact their work had on the world, those women were left out of history for many decades, a fate suffered by many female scientists that is now being somewhat remedied.

Halloran's exhibit is partly about remembering those forgotten histories. It's a reminder that these women existed; that they took up physical space while they also literally uncovered new territory in outer space. [Walk Through "Your Body is a Space That Sees Us" Exhibit (Photos)]

"It's almost like a roll call; it's like saying they were there," Halloran told Space.com at the Luis de Jesus Los Angeles art gallery, where the work was previously on display. "This experience of the history of astronomy is theirs, is ours, is yours, and it is about kind of a physical experience. It's not just something that's at a distance."

The original painting of the Small Magellanic Cloud by Lia Halloran, in honor of Henrietta Swan Leavitt, an astronomer who studied variable stars in the cloud.

If those women are the "your" in the title of Halloran's exhibit "Your Body is a Space That Sees Us" then who is the "us"? Is the title spoken by the universe? Or is it the women who are talking to the current generation, calling on them to remember forgotten histories? Either way, the title calls out to the people who view Halloran's works; they are also bodies that fill a space as they observe the world around them. Observing the natural world requires a person's physical presence someone has to look through the telescope and photograph the sky. Those physical acts are what begin to illuminate the conceptual landscape; to identify new islands in a vast, unexplored ocean of knowledge.

The Harvard College Observatory's Astronomical Photographic Plate Collection contains over 500,000 photographs of sections of the night sky, captured by astronomers between 1882 and 1992. A large portion of those photographs were taken by female astronomers who worked at the observatory in the last 1800s. Led by astronomer Thomas Pickering, the women were at one point given the derogatory group title "Pickering's Harem." Later, the nickname changed to the "Harvard Computers," a name created at a time when computers were people and not machines.

The work of the Harvard Computers and some of the group's most influential members is detailed in the book "The Glass Universe: How the Ladies of the Harvard Observatory Took the Measure of the Stars" (Viking, 2016) by Dava Sobel. With a grant from the National Endowment for the Arts, Halloran visited Harvard and received access to the photographic plate collection around the time that Sobel was investigating the history of the people who created it. Halloran said she and Sobel began conversing as they both dug through the plate collection and the stories surrounding it.

There were three particularly influential astronomers who came out of this Harvard group: Henrietta Swan Leavitt, who figured out a way to measure distances to far-off objects and laid the groundwork for Edwin Hubble to discover that the universe is expanding; Cecilia Payne-Gaposchkin, who showed that hydrogen is by far the most common element in the universe; and Annie Jump Cannon, who came up with a classification system for stars that is still used today.

But Halloran said the works are meant to reflect the entire history of female astronomers, including Hypatia, an astronomer who lived in Greece around A.D. 415, and Jocelyn Bell Burnell, who identified the first pulsar but did not share the Nobel Prize in physics that was awarded for that discovery.

Your Body is a Space That Sees: The Magellanic Cloud from Lia Halloran on Vimeo.

For the exhibit, Halloran selected a few plates created by members of the Harvard Computers, and did paintings of these photographs. At the gallery, Halloran showed me one of the pieces that depicts the Small Magellanic Cloud, a dwarf galaxy that orbits the Milky Way. Halloran painted hundreds of dots representing stars.

"As much as I can, I try to represent the [stellar] density," she said. "I'm not gridding it out, so if someone were to compare this with the actual image, they wouldn't find the exact number of stars [in the painting], but the density would be equivalent."

Halloran uses a type of paint that is "highly volatile," meaning it doesn't settle on the paper until the liquid in it evaporates. The effect is similar to how coffee rings dry on paper the solids that float around in the liquid move to the outer edge of the ring, so that edge is usually darker than the inner edge.

Similarly, in Halloran's paintings, a single dot of the paint isn't a solid circle; instead, the coloring moves to the outside of the dot, creating an ombr effect all by itself. Broad, sweeping brush strokes around the edges of the panting look like the curling patterns of a gas cloud or smoke rising from a fire. These monochrome paintings are simpler versions of actual telescopic images, and the works capture the serenity of a star-filled sky and the fluid movement of cosmic structures. They may inspire a Zen-like trance in the observer.

But many of the pieces in the gallery are not just paintings; creating them involves another, much more complicated step. In the gallery, Halloran and I stand before two square pieces that both show a dense cluster of stars. One of them looks as though she used blue paint on white paper, while the other looks as though it was done with white paint on blue paper. Halloran is pointing to one and then the other, saying, "This is that." I think she must mean she's painted the same object twice, but after a few confused minutes I realize she's being literal. The piece that looks as though it was done with blue paint is actually a negative of the other painting.

The image on the right is a cyanotype of the painting on the left. Cyanotyping creates a negative image of the original, similar to how photographs are made from film.

To achieve this effect, Halloran did her original paintings on a semitransparent paper, which was then placed on top of watercolor paper inside a darkroom, and brushed over with a light-sensitive paint, a process called cyanotyping. When the sandwiched works are brought out of the darkroom and into the light, the light-sensitive paint creates a negative of the original painting, so that where the original was white the new one is dark, hence the new pieces looking like photo negatives of the originals. (In the past, cyanotyping was used to make copies of drawings.) The video above shows how Halloran and colleagues carried out this process.

Halloran assures me I'm not the only person who didn't immediately understand the connection between these pieces. But that's part of engaging her audience, she told me; it's her way of pushing them to more actively engage with the works, and to "have an experience."

"I like that you look at this and you dont totally know what you're looking at," she said. "I like that there's something that makes you stay a little longer. You have to explore a little bit, to dig deep, to get in there. And that can be frustrating for the viewer. But I want them to have to have a dedicated look, and take time. [The art works] evolve and they give a little more the longer you take with them."

Another way that the pieces engage with the viewer is how they are framed: the starry landscapes are bordered by round frames, which give the impression that the viewer is looking down the tube of a telescope its a reminder that the viewer's body occupies a space that sees these starry scenes. Halloran and I walk over to one of the largest pieces in the exhibit, which has a horizontal oval frame.

"When I hung this up in my studio the first time I was like, 'Oh my gosh, I'm in a spaceship and I'm looking through this porthole!'" she said. "I didn't intend for that. But they become experiential and not just a large version of another image."

Some of the more vertically oriented oval frames even look like mirrors. Either way, they highlight the act of observation, not just by long-dead astronomers but by the people standing in the gallery.

The cyanotyping that Halloran uses to create her works is similar to how photographs are developed, and serves as one more link to the Harvard Computers. The photographic plates are extremely fragile and would have been somewhat labor-intensive to make, but they allowed astronomers of the day to study a huge number of night-sky objects in detail, and to catalogue and characterize them without having to look into a telescope.

Two cyanotype works appear in Lia Halloran's exhibit "Your Body is a Space That Sees Us."

"It was really important that to me that, these aren't just images from history, but the process itself sort of reflects that history," Halloran said.

The Harvard plate collection has also provided a historical record of cosmic objects unlike anything else that exists in astronomy. Astronomers in the 21st century have used the plates to look for objects that have moved across the sky in the last 100 years or so. The background stars are so distant that even over the course of a century, they will appear to be in the same place relative to each other. But nearer objects like asteroids or objects in the Kuiper Belt (the region of the solar system beyond Neptune) could move relative to those background stars over decades or centuries; therefore, by comparing two images of the same patch of sky, taken 50 or 100 years apart, astronomers could identify those moving, nearby bodies.

In another 100 years, scientists will have plenty of digitized sky observations to comb through, but for now, the glass plates are a rare gift to modern astronomers. Halloran thinks that's a contribution that's worth remembering, and worth honoring through art.

Follow Calla Cofield@callacofield.Follow us@Spacedotcom,FacebookandGoogle+. Original article onSpace.com.

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Artist's Stunning New Exhibit Celebrates Harvard's 'Hidden' Female Astronomers - Space.com