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A Tour of Arp 299

Smithsonian Astrophysical Observatory
What would happen if you took two galaxies and mixed them together over millions of years? A new study using data from NASA's Chandra X-ray Observatory and other telescopes reveals the cosmic culinary outcome. Arp 299 is a system located about 140 million light years from Earth. It contains two galaxies that are merging, creating a partially blended mix of stars from each galaxy in the process. However, this stellar mix is not the only ingredient. Data from Chandra reveal 25 bright X-ray sources sprinkled throughout the Arp 299 concoction. Fourteen of these sources are such strong emitters of X-rays that astronomers categorize them as “ultra-luminous X-ray sources,” or ULXs. These ULXs are found embedded in regions where stars are currently forming at a rapid rate. Most likely, the ULXs are binary systems where a neutron star or black hole is pulling matter away from a companion star that is much more massive than the Sun. These double star systems are called high-mass X-ray binaries. This buffet of high-mass X-ray binaries is one of the richest in a galaxy located in the nearby universe, but Arp 299 contains relatively powerful star formation. This is due at least in part to the merger of the two galaxies, which has triggered waves of star formation. The formation of high-mass X-ray binaries is a natural consequence of the blossoming star birth in Arp 299 as some of the young massive stars, which often form in pairs, evolve into these systems. While Arp 299 is intriguing itself, this system also has similarities to more distant galaxies. This gives astronomers a chance to sample a local version of faraway cosmic creations, providing hints to the ingredients and recipe that created them.

A Tour of Cassiopeia A

Smithsonian Astrophysical Observatory
Where do most of the elements essential for life on Earth come from? The answer: inside the furnaces of stars and the explosions that mark the end of some stars' lives. Astronomers have long studied exploded stars and their remains — known as "supernova remnants" — to better understand exactly how stars produce and then disseminate many of the elements on Earth and throughout the cosmos. Cassiopeia A, or Cas A for short, is one of the most intensely studied of these supernova remnants. A new image from NASA's Chandra X-ray Observatory shows the location of different elements in the remains of the explosion: silicon, sulfur, calcium, and iron. Each of these elements produces X-rays within narrow energy ranges, allowing maps of their location to be created. Astronomers also see the blast wave from the explosion in the form of the blue outer ring. X-ray telescopes such as Chandra are important to study supernova remnants and the elements they produce because these events generate extremely high temperatures — millions of degrees — that remain even thousands of years after the explosion. This means that many supernova remnants, including Cas A, glow most strongly at X-ray wavelengths that are undetectable with other types of telescopes. Chandra's sharp X-ray vision helps astronomers not only determine what elements are present in Cas A, but also how much of each there is. For example, Cas A has dispersed about 10,000 Earth masses worth of sulfur alone, and about 20,000 Earth masses of silicon. The iron in Cas A weighs about 70,000 times that of the Earth, and astronomers detect a whopping one million Earth masses worth of oxygen being ejected into space from Cas A, equivalent to about three times the mass of the Sun. Chandra has repeatedly observed Cas A since the telescope was launched into space in 1999. It will continue to do so, revealing new information about the dense core left behind in the center of Cas A, details of the powerful explosion, and specifics of how the important debris is ejected into space.

A Tour of GSN 069

Smithsonian Astrophysical Observatory
There's an adage that it's not healthy to skip meals. Apparently, a supermassive black hole in the center of a galaxy millions of light years away has gotten the message. A team of astronomers found X-ray bursts repeating about every nine hours originating from the center of a galaxy called GSN 069. Obtained with NASA's Chandra X-ray Observatory and the European Space Agency's XMM-Newton, these data indicate that the supermassive black hole located there is consuming large amounts of material on a regular schedule. While scientists had previously found two "stellar-mass" black holes (those that weigh about 10 times the Sun's mass) occasionally undergoing regular outbursts before, this behavior has never been detected from a supermassive black hole until now. The black hole at the center of GSN 069, located 250 million light years from Earth, contains about 400,000 times the mass of the Sun. The researchers estimate that the black hole is consuming about four Moons' worth of material about three times a day. That's equivalent to almost a million billion billion pounds going into the black hole per feeding. ESA's XMM-Newton was the first to observe this phenomenon in GSN 069 with the detection of two bursts on December 24, 2018. Astronomers then followed up with more XMM-Newton observations on January 16 and 17, 2019, and found five outbursts. Observations by Chandra less than a month later, on February 14 and 15, revealed an additional three outbursts. The Chandra data were crucial for this study because they were able to show that the X-ray source is located in the center of the host galaxy, which is where a supermassive black hole is expected to be. The combination of data from Chandra and XMM-Newton implies that the size and duration of the black hole's meals have decreased slightly, and the gap between the meals has increased. Astronomers are planning future observations that will be crucial to see if the trend continues.

A Tour of Mrk 1216

Smithsonian Astrophysical Observatory
Isolated for billions of years, a galaxy with more dark matter packed into its core than expected has been identified by astronomers using data from NASA's Chandra X-ray Observatory. The galaxy, known as Markarian 1216, contains stars that are within 10% the age of the universe. In other words, the stars are almost as old as the universe itself. Scientists have found that Markarian 1216 has gone through a different evolution than typical galaxies. This includes dark matter that, through gravity, holds the galaxy together. Dark matter is a mysterious substance that accounts for about 85% of the matter in the universe, yet does not give off or reflect light. Therefore, scientists have only been able to detect it indirectly so far, making it a challenge to learn about. Markarian 1216 belongs to a family of elliptically shaped galaxies that are more densely packed with stars in their centers than most other galaxies. Astronomers think they have descended from reddish, compact galaxies called "red nuggets" that formed about a billion years after the Big Bang, but then stalled in their growth about 10 billion years ago. If this explanation is correct, then the dark matter in Markarian 1216 and its galactic cousins should be tightly packed. To test this idea for the first time, a pair of astronomers studied the X-ray brightness and temperature of hot gas from Chandra at different distances from Markarian 1216's center. This allowed them to, in a sense, weigh, how much dark matter exists in the middle of the galaxy. The researchers found a high concentration of dark matter in the center of Markarian 1216, confirming that Markarian 1216 descended from a red nugget galaxy. This tells us about the evolution of Mrk 1216 going back in time about ten billion years. Further studies of this galaxy may provide astronomers with the opportunity to test ideas about the nature of dark matter.

A Tour of Cygnus A

Smithsonian Astrophysical Observatory
A ricocheting jet blasting from a giant black hole has been captured by NASA's Chandra X-ray Observatory. Chandra's data reveal the presence of a powerful jet of particles and electromagnetic energy that has shot out from the black hole and slammed into a wall of hot gas, then ricocheted to punch a hole in a cloud of energetic particles, before it collides with another part of the gas wall. Cygnus A is a large galaxy that sits in the middle of a cluster of galaxies about 760 million light years from Earth. A supermassive black hole at the center of Cygnus A is rapidly growing as it pulls material swirling around it into its gravitational grasp. During this process, some of this material is redirected away from the black hole in the form of a narrow beam, or jet. Such jets can significantly affect how the galaxy and its surroundings evolve. In a deep observation that lasted 23 days, scientists used Chandra to create a highly detailed map of both the jet and the intergalactic gas, which they used to track the path of the jets from the black hole. The jet expanded after ricocheting and created a hole in a nearby cloud of particles that is between 50,000 and 100,000 light years deep and 26,000 light years wide. For context, the Earth is located about 26,000 light years away from the center of the Milky Way galaxy. Energy produced by jets from black holes can heat intergalactic gas in galaxy clusters and prevent it from cooling and forming large numbers of stars in a central galaxy like Cygnus A. By studying Cygnus A, scientists can tell more about how jets from black holes interact with their surroundings.

A Tour of Lensed Quasars

Smithsonian Astrophysical Observatory
Like whirlpools in the ocean, spinning black holes in space create a swirling torrent around them. However, black holes do not create eddies of wind or water. Rather, they generate disks of gas and dust heated to hundreds of millions of degrees that glow in X-ray light. Using data from NASA's Chandra X-ray Observatory and chance alignments across billions of light years, astronomers have deployed a new technique to measure the spin of five supermassive black holes. The matter in one of these cosmic vortices is swirling around its black hole at greater than about 70% of the speed of light. The astronomers took advantage of a natural phenomenon called a gravitational lens. With just the right alignment, the bending of space-time by a massive object, such as a large galaxy, can magnify and produce multiple images of a distant object, as predicted by Einstein. In this latest research, astronomers used Chandra and gravitational lensing to study six quasars, each consisting of a supermassive black hole rapidly consuming matter from a surrounding accretion disk. Gravitational lensing of the light from each of these quasars by an intervening galaxy has created multiple images of each quasar. The key advance made by researchers in this study was that they took advantage of "microlensing," where individual stars in the intervening, lensing galaxy provided additional magnification of the light from the quasar. A higher magnification means a smaller region is producing the X-ray emission. How can these black holes spin so quickly? The researchers think that these supermassive black holes likely grew by accumulating most of their material over billions of years from an accretion disk spinning with a similar orientation and direction of spin, rather than from random directions. Like a merry-go-round that keeps getting pushed in the same direction, the black holes kept picking up speed. This information helps astronomers learn more about how these supermassive black holes grew and evolved in the early Universe.

A Tour of 3D Visualizations

Smithsonian Astrophysical Observatory
Since ancient times, the study of astronomy has largely been limited to the flat, two-dimensional projection of what appears on the sky. However, just like a botanist puts a plant under a microscope or a paleontologist digs for fossils, astronomers want more "hands on" ways to analyze objects in space. As one decade ends and another begins, astronomers are exploring ways to combine ingenious techniques with rich datasets from powerful modern telescopes to move from studying objects in two dimensions to studying them in three. These computer simulations represent an exciting step in that direction. Each of these is a three-dimensional (3D) visualization of an astronomical object based on data from NASA's Chandra X-ray Observatory and other X-ray observatories. While unable to fly to these distant objects and travel around them, astronomers have used the data they can gather from Chandra and other X-ray observatories to learn about the geometry, velocity, and other physical properties of each of these cosmic sources. Each of these computer simulations is available to the public on free software that is supported by most platforms and browsers and allows users to interact with and navigate 3D models as they choose. The objects include jets blasting away from infant stars, a star that changes its brightness wildly over time, and some of the most well-known supernova explosions such as Cassiopeia A and SN 1987A. We invite you to explore these cosmic objects like you never have before.

A Tour of NGC 6231

Smithsonian Astrophysical Observatory
In some ways, star clusters are like giant families with thousands of stellar siblings. These stars come from the same origins — a common cloud of gas and dust — and are bound to one another by gravity. Astronomers think that our Sun was born in a star cluster about 4.6 billion years ago that quickly dispersed. By studying young star clusters, astronomers hope to learn more about how stars — including our Sun — are born. NGC 6231, located about 5,200 light years from Earth, is an ideal testbed for studying a stellar cluster at a critical stage of its evolution: not long after star formation has stopped. The discovery of NGC 6231 is attributed to Giovanni Battista Hodierna, an Italian mathematician and priest who published observations of the cluster in 1654. Sky watchers today can find the star cluster to the southwest of the tail of the constellation Scorpius. NASA's Chandra X-ray Observatory has been used to identify the young Sun-like stars in NGC 6231, which have, until recently, been hiding in plain sight. Young star clusters like NGC 6231 are found in the band of the Milky Way on the sky. As a result, interloping stars lying in front of or behind NGC 6231 greatly outnumber the stars in the cluster. These stars will generally be much older than those in NGC 6231, so members of the cluster can be identified by selecting signs of stellar youth. The Chandra data, combined with infrared data from the VISTA telescope, have provided the best census of young stars in NGC 6231 available. By studying this cluster and others like it, astronomers hope to better understand our Sun's origins and our shared cosmic ancestry with stars across the Galaxy.

A Tour of NGC 6357

Smithsonian Astrophysical Observatory
Although there are no seasons in space, this cosmic vista invokes thoughts of a frosty winter landscape. It is, in fact, a region called NGC 6357 where radiation from hot, young stars is energizing the cooler gas in the cloud that surrounds them. Located about 5,500 light years from Earth, NGC 6357 is actually a “cluster of clusters” containing at least three clusters of young stars, including many hot, massive, luminous stars. X-ray data from Chandra and ROSAT reveal hundreds of point sources, which are the young stars in NGC 6357, as well as diffuse X-ray emission from hot gas. There are bubbles, or cavities, that have been created by radiation and material blowing away from the surfaces of massive stars, plus supernova explosions. Researchers use Chandra to study NGC 6357 and similar objects because young stars are bright in X-rays. Also, X-rays can penetrate the shrouds of gas and dust surrounding these infant stars, allowing astronomers to see details of star birth that would be otherwise missed. For more information:

A Tour of Jupiter's Auroras

Smithsonian Astrophysical Observatory
On Earth, people at very high latitudes sometimes enjoy the spectacular light shows known as the auroras, also called the northern or southern lights. Our planet is not, however, the only world to experience auroras. For some time, scientists have observed high-energy auroras on Jupiter in the form of ultraviolet and X-ray light. A new study using data from NASA’s Chandra X-ray Observatory and ESA’s XMM-Newton shows that the auroras on Jupiter are significantly different than those on Earth. Scientists have discovered that Jupiter’s auroras behave independently of one another at each pole. This is unlike Earth, where the northern and southern lights tend to mirror one another. To understand how Jupiter produces its X-ray auroras, researchers plan to combine new and upcoming X-ray data from Chandra and XMM-Newton with information from NASA’s Juno mission, which is currently in orbit around the planet. If scientists can connect the X-ray activity with physical changes observed simultaneously with Juno, they may be able to determine the process that generates the Jovian auroras. There are many questions this new X-ray study pose: how does Jupiter’s magnetic field give particles the huge energies needed to make X-rays? Do these high-energy particles affect the Jovian weather and the chemical composition of its atmosphere? Can they explain the unusually high temperatures found in certain places in Jupiter’s atmosphere? These are the questions that Chandra, XMM-Newton, and Juno may be able to help answer in the future.

A Tour of GRB 150101B

Smithsonian Astrophysical Observatory
On October 16, 2017, astronomers excitedly reported the first detection of electromagnetic waves, or light, from a gravitational wave source. Now, a year later, researchers are announcing the existence of a cosmic relative to that historic event. The discovery was made using data from a host of telescopes including NASA’s Chandra X-ray Observatory. The object of the new study, called GRB 150101B, was first reported as a gamma-ray burst detected by Fermi in January 2015. This detection and follow-up observations show that this new object shares remarkable similarities to the neutron star merger and gravitational wave source discovered by the Advanced Laser Interferometer Gravitational Wave Observatory, and its European counterpart Virgo in 2017 known as GW170817. The latest study concludes that these two separate objects may, in fact, be related. The researchers think both GRB 150101B and GW170817 were most likely produced by the same type of event: the merger of two neutron stars. This is a catastrophic collision that generated a narrow jet, or beam, of high-energy particles. The jet produced a short, intense burst of gamma rays, a high-energy flash that can last only seconds. This was followed by an afterglow in optical light that lasted a few days and X-ray emission that lasted much longer. Scientists think both of these events involved kilonovas, that is, powerful explosions that release large amounts of energy and can produce elements like gold, platinum and uranium. Understanding these explosions helps astronomers trace our cosmic ancestry. There is still a lot to learn about these events, but Chandra is poised to help in this new era of combined gravitational wave and electromagnetic investigations into our Universe.

A Tour of Mrk 1216

Smithsonian Astrophysical Observatory
About a decade ago, astronomers discovered a population of small, but massive galaxies called "red nuggets." A new study using NASA's Chandra X-ray Observatory indicates that black holes have squelched star formation in these galaxies and may have used some of the untapped stellar fuel to grow to unusually massive proportions. Red nuggets were first discovered by the Hubble Space Telescope at great distances from Earth, corresponding to times only about three or four billion years after the Big Bang. They are relics of the first massive galaxies that formed within only one billion years after the Big Bang. Astronomers think they are the ancestors of the giant elliptical galaxies seen in the local Universe. The masses of red nuggets are similar to those of giant elliptical galaxies, but they are only about a fifth of their size. While most red nuggets merged with other galaxies over billions of years, a small number managed to slip through the long history of the cosmos untouched. These unscathed red nuggets represent a golden opportunity to study how the galaxies, and the supermassive black hole at their centers, act over billions of years of isolation. For the first time, Chandra has been used to study the hot gas in two of these isolated red nuggets, Mrk 1216, and PGC 032673. They are located only 295 million and 344 million light years from Earth respectively, rather than billions of light years for the first known red nuggets. This X-ray emitting hot gas contains the imprint of activity generated by the supermassive black holes in each of the two galaxies. The Chandra results show these supermassive black holes not only prevent new stars from forming, they might also swipe some of the stellar material to add bulk to themselves. This may have allowed the black holes in these two galaxies to swell to more five billion times the Sun. The Chandra data are helping to tell the story of what happens to these red nugget galaxies over their long, solitary journey through cosmic time.

A Tour of G11.2-0.3

Smithsonian Astrophysical Observatory
While they may sound like very different and distinct fields, astronomy and history can intersect in very interesting and important ways. Take, for example, historical supernovas and their remnants. These are objects that astronomers observe today and that can also be linked to recordings in previous centuries or even millennia. Being able to tie a credible historical event with a supernova remnant observed today provides crucial information about these explosive stellar events. Until now, the supernova remnant G11.2-0.3 was considered one of these historical supernova remnants. Previous studies have suggested that G11.2-0.3 was created in a supernova that was witnessed by Chinese astronomers in 386 CE. New Chandra data, however, of this circle shaped debris field, indicate that is not the case. The latest information from Chandra reveals that there are dense clouds of gas that lie between Earth and the supernova remnant. Therefore, it is not possible that much optical light from the supernova - the kind of light humans can see - would have penetrated the clouds and been visible with the naked eye at Earth. While it may no longer be a historical supernova remnant, G11.2-0.3 remains an intriguing and beautiful object that astronomers will continue to study. More information at

A Tour of the Teacup

Smithsonian Astrophysical Observatory
Fancy a cup of cosmic tea? This one isn't as calming as the ones on Earth. In a galaxy hosting a structure nicknamed the "Teacup," a galactic storm is raging. The source of the cosmic squall is a supermassive black hole buried at the center of a galaxy located about 1.1 billion light years from Earth. As matter in the central regions of the galaxy is pulled toward the black hole, it is energized by the strong gravity and magnetic fields near the black hole. The infalling material produces more radiation than all the stars in the host galaxy. This kind of actively growing black hole is known as a quasar. Located about 1.1 billion light years from Earth, the Teacup's host galaxy was originally discovered in visible light images by citizen scientists in 2007 as part of the Galaxy Zoo project, using data from the Sloan Digital Sky Survey. Since then, professional astronomers using space-based telescopes have gathered clues about the history of this galaxy with an eye toward forecasting how stormy it will be in the future. The "handle" of the Teacup is a ring of optical and X-ray light surrounding a giant bubble. This handle-shaped feature, which is located about 30,000 light-years from the supermassive black hole, was likely formed by one or more eruptions powered by the black hole. Radio emission also outlines this bubble, and a bubble about the same size on the other side of the black hole. New data from Chandra and ESA's XMM-Newton mission are giving astronomers an improved understanding of the history of this galactic storm.

A Tour of R Aquarii

Smithsonian Astrophysical Observatory
In biology, “symbiosis” refers to two organisms that live close to and interact with one another. Astronomers have long studied a class of stars — called symbiotic stars — that co-exist in a similar way. Using data from NASA’s Chandra X-ray Observatory and other telescopes, astronomers are gaining a better understanding of how volatile this close stellar relationship can be. R Aquarii is one of the best known of the symbiotic stars. Located at a distance of about 710 light years from Earth, its changes in brightness were first noticed with the naked eye almost a thousand years ago. Since then, astronomers have studied this object and determined that R Aqr is not one star, but two: a small, dense white dwarf and a cool red, giant star. Occasionally, enough material will be pulled from the red giant onto the surface of the white dwarf to trigger thermonuclear fusion of hydrogen. The release of energy from this process can produce a nova, an asymmetric explosion that blows off the outer layers of the star at velocities of ten million miles per hour or more, pumping energy and material into space. Since shortly after Chandra launched in 1999, astronomers began using the X-ray telescope to monitor the behavior of R Aquarii. Chandra’s data have provided new information about the details and timing of the explosions that occur in R Aquarii. Continued close monitoring of R Aquarii with Chandra and other telescopes in the future should give scientists more insight into this unusual stellar system.

A Tour of Abell 2142

Smithsonian Astrophysical Observatory
Astronomers have used data from NASA's Chandra X-ray Observatory to capture a dramatic image of an enormous tail of hot gas. This tail stretches for more than a million light years behind a group of galaxies that is falling into the depths of an even-larger cluster of galaxies. Discoveries like this help astronomers learn about the environment and conditions under which the Universe's biggest structures evolve. Galaxy clusters are the largest structures in the Universe held together by gravity. While galaxy clusters can contain hundreds or even thousands of individual galaxies, the lion's share of mass in a galaxy cluster comes from hot gas, which gives off X-rays, and unseen dark matter. How did these cosmic giants get to be so big? Scientists have discovered that one way galaxy clusters grow is by capturing other galaxies with their extraordinarily powerful gravity. Abell 2142 is a galaxy cluster that contains hundreds of galaxies immersed in giant reservoirs of multi-million-degree gas. A wide-field view including Chandra data shows that a much smaller group of galaxies is plummeting toward the center of Abell 2142, adding to the enormous heft of this cluster. Behind this diving galaxy group, astronomers found a remarkable long tail of X-rays that extends for hundreds of thousands of light years. This tail formed when hot gas from the group of galaxies falls is stripped off into Abell 2142, much like leaves from a tree in the fall during a strong gust of wind. The shape and length of the tail tells astronomers about certain properties in the system, such as the strength of the magnetic fields that may be wrapping about the tail. Galaxy clusters have been one of Chandra's most compelling targets over its nearly two decades of operations in space. Scientists look forward to studying many more in the years to come.

A Tour of Abell 1033

Smithsonian Astrophysical Observatory
Hidden in a distant galaxy cluster collision are wisps of gas resembling the starship Enterprise – an iconic spaceship from the "Star Trek" franchise. Galaxy clusters — cosmic structures containing hundreds or even thousands of galaxies — are the largest objects in the Universe held together by gravity. Multi-million-degree gas fills the space in between the individual galaxies. The mass of the hot gas is about six times greater than that of all the galaxies combined. This superheated gas is invisible to optical telescopes, but shines brightly in X-rays, so an X-ray telescope like NASA's Chandra X-ray Observatory is required to study it. By combining X-rays with other types of light, such as radio waves, a more complete picture of these important cosmic objects can be obtained. A new composite image of the galaxy cluster Abell 1033, including X-rays from Chandra (purple) and radio emission from the Low-Frequency Array (LOFAR) network in the Netherlands (blue), does just that. Optical emission from the Sloan Digital Sky Survey is also shown. The galaxy cluster is located about 1.6 billion light years from Earth. Using X-ray and radio data, scientists have determined that Abell 1033 is actually two galaxy clusters in the process of colliding. This extraordinarily energetic event, happening from the top to the bottom in the image, has produced turbulence and shock waves, similar to sonic booms produced by a plane moving faster than the speed of sound. In addition to the astrophysical value, the new Abell 1033 image also provides an excellent example of something that happens in another scientific field. Pareidolia is the psychological phenomenon where familiar shapes and patterns are seen in otherwise random data. In Abell 1033, the structures in the data create an uncanny resemblance — at least to some people — to many of the depictions of the fictional Starship Enterprise from Star Trek. Because of the abstract quality of data taken of space objects, pareidolia can happen quite frequently with astronomical images.

A Tour of XJ1417+52

Smithsonian Astrophysical Observatory
Black holes come in different sizes. The largest, or supermassive, black holes can contain hundreds of thousands times the mass of the Sun up to billions of times its mass and typically reside in the centers of galaxies. Sometimes, however, astronomers find black holes in somewhat unusual places. Take, for example, the object known as XJ1417+52. First discovered in observations from Chandra and XMM-Newton over a decade ago, this object has some interesting properties. To begin with, astronomers think this object may fall right at the boundary between supermassive black holes and the intermediate-mass category. As their name suggest, the latter class are black holes of medium size in between stellar mass black holes and supermassive ones. X-rays from both Chandra and XMM-Newton show that XJ1417+52 gave off an extraordinary amount of X-rays. This and other pieces of evidence suggest that XJ1417+52 contains about 100,000 times the mass of the Sun. What makes this object even more interesting is its location. Rather than being in the center of its host galaxy, it is located on its northern edge. Astronomers think this could have happened when a smaller galaxy with XJ1417+52 at its center collided with a larger galaxy. Since these two galaxies are still in the process of merging, the two black holes have yet to coalesce into one bigger black hole, but may do so millions or billions of years from now. More information at

A Tour of IC 10

Smithsonian Astrophysical Observatory
Long before Starburst® became a popular brand of candy, starbursts were known to astronomers. In 1887, American astronomer Lewis Swift discovered a glowing cloud, or nebula, that turned out to be a small galaxy about 2.2 million light years from Earth. Today, it is known as the “starburst” galaxy IC 10, referring to the intense star formation activity occurring there. More than a hundred years after Swift’s discovery, astronomers are studying IC 10 with the most powerful telescopes of the 21st century. New observations with NASA’s Chandra X-ray Observatory reveal many pairs of stars that may one day become sources of perhaps the most exciting cosmic phenomenon observed in recent years: gravitational waves. By analyzing Chandra observations of IC 10 spanning a decade, astronomers found over a dozen black holes and neutron stars feeding off gas from young, massive stellar companions. Such double star systems are known as “X-ray binaries” because they emit large amounts of X-ray light. As a massive star orbits around its compact companion, either a black hole or neutron star, material can be pulled away from the giant star to form a disk of material around the compact object. Frictional forces heat the infalling material to millions of degrees, producing a bright X-ray source. When the massive companion star runs out fuel, it will undergo a catastrophic collapse that will produce a supernova explosion, and leave behind a black hole or neutron star. The end result is two compact objects: either a pair of black holes, a pair of neutron stars, or a black hole and neutron star. If the separation between the compact objects becomes small enough as time passes, they will produce gravitational waves. Over time, the size of their orbit will shrink until they merge. LIGO has found three examples of black hole pairs merging in this way in the past two years. Astronomers will continue to study IC 10 and other similar galaxies to better understand more about X-ray binaries and their connection to the exciting and evolving field of gravitational wave astronomy.

A Tour of ASASSN14-li

Smithsonian Astrophysical Observatory
In November 2014, a network of optical telescopes picked up a bright outburst from a galaxy about 290 million light years from Earth. Scientists determined that this was a so-called tidal disruption event, where a star wandered too close to a black hole and was ripped apart by immense gravitational forces. Astronomers used other telescopes including a flotilla of high-energy telescopes in space — NASA's Chandra X-ray Observatory, ESA's XMM-Newton and NASA's Neil Gehrels Swift observatory — to study the X-rays emitted as the remains of a star swirled toward the black hole at the center of the galaxy. Some of the remains of the star are pulled into a disk where they circle the black hole before passing over the "event horizon," the boundary beyond which nothing, including light, can escape. The tidal disruption in ASASSN-14li allowed astronomers to estimate the spin rate of the black hole. A black hole has two fundamental properties: mass and spin. While it has been relatively easy for astronomers to determine the mass of black holes, it has been much more difficult to get accurate measurements of their spins. This debris from the shredded star gave astronomers an avenue to directly estimate the black hole's spin in ASASSN-14li. They found that the event horizon around this black hole is about 300 times the diameter of the Earth, yet rotates once every two minutes (compared to the 24 hours it takes to complete one rotation). This means that the black hole is spinning at least about half as fast as the speed of light. These results will likely encourage astronomers to observe future tidal disruption events for long durations to look for similar, regular variations in their X-ray brightness.

A Tour of GJ 176

Smithsonian Astrophysical Observatory
As astronomers discover more planets outside the Solar System, they are examining what conditions can foster or stifle the habitability of planets. A new study suggests that X-rays emitted by a planet's host star may provide critical clues to just how hospitable a star system could be. A team of researchers used data from NASA's Chandra X-ray Observatory and ESA's XMM-Newton to look at the X-ray brightness of 24 stars with masses similar to the Sun that were at least a billion years old. Since stellar X-rays mirror magnetic activity, X-ray observations can tell astronomers about the high-energy environment around the star. In the new study the X-ray data from Chandra and XMM-Newton revealed that stars like the Sun and their less massive cousins calm down surprisingly quickly after a turbulent youth. This is good news for the future habitability of planets orbiting Sun-like stars, because the amount of harmful X-rays and ultraviolet radiation from stellar flares striking planets in orbit around them would be less than scientists used to think. Astronomers will continue to look at many factors that they think play into the habitability of planets around the thousands of exoplanets that have been discovered. Studies like these show that X-rays can play a critical role in the ultimate question of where life might exist elsewhere in the Universe.

A Tour of XJ1500+0154

Smithsonian Astrophysical Observatory
Every so often, an object will pass too close to a black hole and be ripped apart by its intense gravitational forces. As the object, such as a star, approaches the danger zone of the black hole, its stellar debris is flung outward at high speeds, while the star's material falls towards the black hole. This in-falling material becomes hotter and hotter until it generates a signature outburst of X-rays. Astronomers call these "tidal disruption events," or TDEs, and they can be used to better understand how black holes grow and affect their environments. While astronomers have seen multiple examples of TDEs in recent years, a new discovery stands out among the rest. Using data from three X-ray telescopes: Chandra, Swift, and XMM-Newton, researchers have found a TDE that has lasted about ten years, much longer than other events. What could cause this decade-long meal by the black hole? There are a couple of possibilities. The first is that this black hole, located in a galaxy about 1.8 billion light years from Earth, completely shredded the largest star astronomers have known to be destroyed in a TDE. The other, also intriguing, possibility is that in previous TDEs the star wasn't completely ripped apart, but in this event it was. While astronomers continue to study this source and look for others like it, we are reminded just how amazing black holes can be.

A Tour of CL J1001

Smithsonian Astrophysical Observatory
Galaxy clusters are incredibly important objects in the Universe since they are the largest objects in the Universe held together by gravity. Many galaxy clusters contain hundreds or even thousands of galaxies, enormous amounts of hot gas, and giant reservoirs of dark matter. For as much as they already know about galaxy clusters, astronomers are still seeking to learn more. This includes learning about how galaxy clusters first formed in the early Universe. A new discovery by a team of researchers may represent an important step in that direction. Using NASA's Chandra X-ray Observatory and several other telescopes on the ground and in space, researchers recently found a galaxy cluster that is about 11.1 billion light years from Earth. In addition to its remarkable distance, this cluster, known as CL J1001+0220, also displays some intriguing qualities. For example, astronomers find that the core of this cluster is ablaze with star formation. This is quite different from other galaxy clusters observed by astronomers, where star formation rates are very low. It may be that this galaxy cluster represents a brief, but important, stage of the evolution where a cluster transitions from a still-forming cluster into a mature one. Astronomers hope that they will learn a lot about the formation of clusters and the galaxies they contain by studying this object. More information at

How to Tour Michelangelo’s Rome

Smithsonian Magazine

Michelangelo had been on his back for 20 months, resting sparingly, and sleeping in his clothes to save time. When it was all over, however, in the fall of 1512, the masterpiece that he left behind on the ceiling of the Sistine Chapel in Rome would leave the world forever altered.

Born in 1475 to an impoverished but aristocratic family in Caprese, a hillside town near Florence, Michelangelo Buonarroti grew up with an innate sense of pride, which as he aged, would feed his volatile temperament. When he failed to excel at school, his father apprenticed him to Domenico Ghirlandaio, a Florentine frescoist. Cocky from the start, the 13-year-old Michelangelo succeeded in irritating his fellow apprentices, one so badly that the boy punched him in the face, breaking his nose. But in Ghirlandaio’s workshop, Michelangelo learned to paint; in doing so, he caught the attention of Florence’s storied Medici family, whose wealth and political standing would soon put Michelangelo on the map as an artist and, in 1496, chart his course south, to Rome.

“It’s almost as if Michelangelo goes from zero to 65 miles per hour in a second or two,” says William Wallace, an art history professor at Washington University in Saint Louis. “He was 21 when he arrived in Rome, and he hadn’t accomplished a lot yet. He went from relatively small works to suddenly creating the Pietà.” 

It was the Rome Pietà (1499), a sculpture of the Virgin Mary cradling the body of her son Jesus in her lap, and the the artist’s next creation in Florence, the nearly 17-foot-tall figure of David (1504) that earned Michelangelo the respect of the greatest art patron of his age: Pope Julius II. The 10-year partnership between the two men was both a meeting of the minds and a constant war of egos and would result in some of the Italian Renaissance’s greatest works of art and architecture, the Sistine Chapel among them. 

“Pope Julius had, in some ways, an even larger vision—of putting the papacy back on a proper footing. Michelangelo had the ambition to be the world’s greatest artist,” says Wallace. “Both were somewhat megalomaniacal characters. But I think [the relationship] was also deeply respectful.”

Julius II died in 1513, and in 1515, Michelangelo moved back to Florence for nearly two decades. When he returned to Rome in 1534, the Renaissance man had largely moved away from the painting and sculpting that had defined his early career, instead filling his days with poetry and architecture. Michelangelo considered his work on the dome of St. Peter’s Basilica, which dominated his time beginning in 1546, to be his greatest legacy; the project, he believed, would ultimately offer him salvation in Heaven.

Michelangelo Buonarroti died in Rome following a brief illness in 1564, just weeks before his 89th birthday. When a friend questioned why he had never married, Michelangelo’s answer was simple: “I have too much of a wife in this art that has always afflicted me, and the works I shall leave behind will be my children, and even if they are nothing, they will live for a long while.”

St. Peter’s Basilica: Rome Pietà and Dome

Michelangelo was just 24 when he was commissioned to create the Rome Pietà or “pity.” Unveiled during St. Peter’s Jubilee in 1500, it was one of three Pietà sculptures the artist created during his lifetime. When asked why he chose to portray Mary as a young woman, Michelangelo replied, “Women who are pure in soul and body never grow old.” Legend has it that when Michelangelo overheard admirers of the statue attributing it to another artist, he decided to inscribe his name on the Virgin Mary’s sash. It seems he regretted it, since he never signed another work again.

Forty-seven years later, riddled with kidney stones, Michelangelo once again set his sights on St. Peter’s, this time as chief architect of the basilica’s dome. Visitors to St. Peter’s can climb the 320 steps (or take the elevator) to the top of the dome, with views of the Pantheon and Vatican City.

Image by Wikimedia Commons & © Ocean / Corbis. Michelangelo Buonarroti (above, left) moved from Caprese to Rome when he was 21 years old. At age 24, he was asked to create the Rome Pietà, found in St. Peter's Basilica (above, right). (original image)

Image by Flickr user serguei_2k. Michelangelo designed Pope Julius II's tomb, originally intended for St. Peter's Basilica but later reassigned to the church of San Pietro in Vincoli, shown here. (original image)

Image by Flickr user sgatto. In 1561, the artist was hired to convert Diocletian's bath hall into Santa Maria deli Angeli e die Martiri, a church named for the Virgin Mary. His main focus was the central corridor and its eight granite columns. (original image)

Image by Flickr user jscoke. Michelangelo's 12,000-square-foot masterpiece on the ceiling of the Sistine Chapel portrays 343 human figures and nine stories from the Book of Genesis. (original image)

Image by Wikimedia Commons. The Rome Pietà , located at St. Peter's, depicts the Virgin Mary as a young woman. The piece is the only one ever to be signed by Michelangelo. His name can be found on Mary's sash. (original image)

Image by Flickr user johnmaschak. Late in life, Michelangelo became the chief architect for the dome at St. Peter's Basilica. (original image)

Image by Wikimedia Commons. Michelangelo's plans for the Piazza del Campidoglio were carried out after his death in 1564. Benito Mussolini added the artist's final element, a starburst pattern in the pavement, in 1940. (original image)

Image by Flickr user serguei_2k. Michelangelo's sculpture, Moses, is the clear scene-stealer at San Pietro in Vincoli. (original image)

San Pietro in Vincoli

Pope Julius II recruited Michelangelo to design his tomb at St. Peter’s Basilica in 1505, but the work would go on for almost 30 years. Although the structure was supposed to include dozens of statues by the artist and more than 90 wagonloads of marble, after Julius’ death, Pope Leo X—who hailed from a rival family—kept Michelangelo busy with other plans. Only three statues were included in the final product, which was reassigned to the more modest church of San Pietro in Vincoli.  Among them, the artist’s rendering of Moses is the clear scene-stealer. With his penchant for drama, Michelangelo referred to San Pietro as, “the tragedy at the tomb,” since he had “lost his youth” in the creation of it.

Sistine Chapel, the Vatican

Michelangelo considered himself to be foremost a sculptor, not a painter, and when Julius II asked him to decorate the ceiling of the Sistine Chapel in May of 1508—tearing him away from his work at the pope’s tomb—the artist was less than pleased. A mildew infestation threatened a portion of the work, and Michelangelo pressed his advantage, telling Julius, “I already told your holiness that painting is not my trade; what I have done is spoiled; if you do not believe it, send and see.” The issue was eventually resolved; Michelangelo set back to work on the 343 human figures and nine stories from the Book of Genesis that the 12,000-square-foot masterpiece would eventually comprise.

Michelangelo often locked horns with the Pope about money and sometimes referred to him as “my Medusa,” while Julius, on at least one occasion, allegedly threatened to beat or throw the artist from the scaffolding of the Sistine Chapel if he did not finish his work more quickly. This abuse aside, the painting eventually took its toll on the artist, who suffered a leg injury when he fell from the scaffolding and partial blindness—a result of staring upwards at the ceiling for so long—which forced him to read letters by raising his arms above his head. In 1536, Michelangelo was summoned back to the chapel to paint The Last Judgment above the altar, this time for Pope Paul III.

Piazza del Campidoglio

Campidoglio, or Capitoline Hill, is one of the seven hills Rome was founded upon and has been central to the city’s government for more than 2,000 years. In 1538, when Michelangelo was asked to put a new face on the ancient site, the task was great: it had been used as headquarters for the Roman guilds during the Middle Ages, and required a major overhaul. The artist set to work on the main square, reshaping it as an oval to create symmetry; adding a third structure, the Palazzo Nuovo; and re-sculpting the base of the 2nd century A.D. statue of Marcus Aurelius (which has since been moved to the Capitoline Museums, nearby). Although the piazza wasn’t finished at the time of Michelangelo’s death, it was completed in various stages during the next 100 years using the artist’s designs. In 1940, Benito Mussolini installed the final element, Michelangelo’s brilliant starburst pattern in the pavement. 

Santa Maria degli Angeli e dei Martiri

As a humanist, Michelangelo believed in the preservation of Rome’s ancient ruins. It was a task he took to heart in 1561, when the artist was hired to convert Diocletian’s massive bath hall, erected in 300 A.D., into a church named for the Virgin Mary. Ironically, the facility’s new destiny was at odds with its original means of construction, which is said to have required the forced labor (and frequent deaths) of 40,000 Christian slaves. The artist’s mission centered on the bath hall’s central corridor, the Terme di Diocleziano, with its eight red granite columns that still remain today. Although Michelangelo died before the church was finished, his pupil, Jacopo Lo Duca, saw the project through to completion.

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