Wednesday, July 16, 2014

Too Hot to Swallow

Too Hot to Swallow:

Wang
We are delighted to welcome Q. Daniel Wang as a guest blogger today. Daniel is the first author of a paper dissecting the X-ray-emitting gas around the center of our Galaxy, the subject of our latest press release. He is a professor in astronomy at University of Massachusetts Amherst. He was the Principal Investigator of the first large-scale Chandra and Hubble surveys of the Galactic center to explore various components of this exotic ecosystem. He recently enjoyed a four-month stay at University of Cambridge as a Beverley Sackler Distinguished Visiting astronomer, where much of the work reported in the paper was finished.

It has been known for a while that almost all massive galaxies contain a giant black hole at their centers. Most of such black holes, including the one at the center of our own Galaxy, are, however, far dimmer than quasars typically seen in the early universe. This dimness cannot simply be explained by decreasing amounts of material that the black holes could capture. Have the black holes lost their appetite? Or do they just swallow everything that is captured without much radiation? Many theories have been developed. But direct observational tests are hard to come by.


Sgr A*

Because of its proximity, our own giant black hole (or Sgr A*, discovered first in radio) allows for a unique close-up view of what might be going on. Indeed, very weak X-ray emission with occasional flaring has been detected from the Galaxy's center for years. But even the nature of this emission has remained greatly uncertain. In particular, it has recently been theorized that the emission may be largely due to stellar flares from a putative concentration of low-mass stars around Sgr A*, which are too faint to have been detected at other wavelengths. This theory was motivated by a marginal detection of a distinct fluorescent emission line – the absorption of radiation followed by emission at lower energies – in the spectrum of the center from early X-ray observations. The fluorescence of the stellar flaring radiation is expected to occur at the relatively cool surface of the stars, which are presumably more active because of their fast rotation caused by black hole tugging.

Black Hole

With the greatly improved counting statistics and spectral resolution, as well as the superb spatial resolution, of the three million seconds of Chandra observations (an X-ray Visionary Project), we can now rule out the stellar scenario. The fluorescent line is not detected in the spectrum of the quiescent or flare emission from the center. As detailed in a separate paper, about 40 or so flares are detected, which have very short time spans, typically lasting for about an hour or so, and can be isolated quite easily in the data stream. These flares account for about one third of the X-ray emission of the center and all seem to arise spatially from a point, or Sgr A*. We can further constrain and remove the residual point-like contribution, which is less than about 20% of the quiescent emission and can be explained at least partly by weak flares that are too faint to be identified individually in the observations.

We further find that the extended quiescent emission around Sgr A* has a shape and orientation similar to those of the surrounding disk of massive stars, providing direct evidence that stellar winds are being fed to Sgr A*. Because of high-speed collisions, wind material in this crowded central region is expected to be hot and thus hard for the black hole to capture. But more importantly, even the captured material appears to be too hot to swallow for the black hole. As the material flows inward, it inevitably becomes hotter and swirls faster because of the so-called energy and momentum conservations. The spectrum of the X-ray emission shows that the amount of the material decreases with the increasing temperature, suggesting that it is being removed from the flow. We infer that > 99% of the material needs to be thrown out or sacrificed to allow for a tiny fraction of it to reach the inner most region around the black hole, where the thermal energy generation is most efficient. The fraction of the material eventually falling into the black hole should then be even smaller, severely limiting its growth rate.

But, a black hole may occasionally capture large amounts of cold and dense gas, which is more plentiful in the early universe than at the present. Such gas tends to form an accretion disk around the black hole, allowing for effective dissipation of energy and angular momentum. As a result, a large fraction of the gas can reach the innermost region, which indeed dominates the emission as observed from a quasar, and can eventually fall into the black hole.



Posted by Nelio Inacio at 4:14 PM 0 comments

Clues to the Growth of the Colossus in Coma

Clues to the Growth of the Colossus in Coma:

Coma Cluster

A team of astronomers has discovered enormous arms of hot gas in the Coma cluster of galaxies by using NASA's Chandra X-ray Observatory and ESA's XMM-Newton. These features, which span at least half a million light years, provide insight into how the Coma cluster has grown through mergers of smaller groups and clusters of galaxies to become one of the largest structures in the Universe held together by gravity.

A new composite image, with Chandra data in pink and optical data from the Sloan Digital Sky Survey appearing in white and blue, features these spectacular arms. In this image, the Chandra data have been processed so extra detail can be seen.

The X-ray emission is from multimillion-degree gas and the optical data shows galaxies in the Coma Cluster, which contain only about one-sixth the mass in hot gas. Only the brightest X-ray emission is shown here, to emphasize the arms, but the hot gas is present over the entire field of view.

Researchers think that these arms were most likely formed when smaller galaxy clusters had their gas stripped away by the head wind created by the motion of the cluster through the hot gas, in much the same way that the headwind created by a roller coaster blows the hats off riders.

Coma is an unusual galaxy cluster because it contains not one, but two giant elliptical galaxies near its center. These two giant elliptical galaxies are probably the vestiges from each of the two largest clusters that merged with Coma in the past. The researchers also uncovered other signs of past collisions and mergers in the data.

More at http://chandra.harvard.edu/photo/2013/coma/

-Megan Watzke, CXC







Posted by Nelio Inacio at 4:13 PM 0 comments

NASA's Hubble and Chandra Find Evidence for Densest Nearby Galaxy

NASA's Hubble and Chandra Find Evidence for Densest Nearby Galaxy:

M60

The densest galaxy in the nearby Universe may have been found, as described in our latest press release. The galaxy, known as M60-UCD1, is located near a massive elliptical galaxy NGC 4649, also called M60, about 54 million light years from Earth.

This composite image shows M60 and the region around it, where data from NASA's Chandra X-ray Observatory are pink and data from NASA's Hubble Space Telescope (HST) are red, green and blue. The Chandra image shows hot gas and double stars containing black holes and neutron stars and the HST image reveals stars in M60 and neighboring galaxies including M60-UCD1. The inset is a close-up view of M60-UCD1 in an HST image.

Packed with an extraordinary number of stars, M60-UCD1 is an "ultra-compact dwarf galaxy". It was discovered with NASA's Hubble Space Telescope and follow-up observations were done with NASA's Chandra X-ray Observatory and ground-based optical telescopes.

It is the most luminous known galaxy of its type and one of the most massive, weighing 200 million times more than our Sun, based on observations with the Keck 10-meter telescope in Hawaii. Remarkably, about half of this mass is found within a radius of only about 80 light years. This would make the density of stars about 15,000 times greater than found in Earth's neighborhood in the Milky Way, meaning that the stars are about 25 times closer.

The 6.5-meter Multiple Mirror Telescope in Arizona was used to study the amount of elements heavier than hydrogen and helium in stars in M60-UCD1. The values were found to be similar to our Sun.

Another intriguing aspect of M60-UCD1 is that the Chandra data reveal the presence of a bright X-ray source in its center. One explanation for this source is a giant black hole weighing in at some 10 million times the mass of the Sun.

More at http://chandra.harvard.edu/photo/2013/m60/

-Megan Watzke, CXC









Posted by Nelio Inacio at 4:13 PM 0 comments

Neutron Star Undergoes Wild Behavior Changes

Neutron Star Undergoes Wild Behavior Changes:

IGR J18245-2452

These two images from NASA's Chandra X-ray Observatory show a large change in X-ray brightness of a rapidly rotating neutron star, or pulsar, between 2006 and 2013. The neutron star - the extremely dense remnant left behind by a supernova - is in a tight orbit around a low mass star. This binary star system, IGR J18245-2452 (mouse over the image for its location) is a member of the globular cluster M28.


As described in a press release from the European Space Agency, IGR J18245-2452 provides important information about the evolution of pulsars in binary systems. Pulses of radio waves have been observed from the neutron star as it makes a complete rotation every 3.93 milliseconds (an astonishing rate of 254 times every second), identifying it as a "millisecond pulsar."

The widely accepted model for the evolution of these objects is that matter is pulled from the companion star onto the surface of the neutron star via a disk surrounding it. During this so-called accretion phase, the system is described as a low-mass X-ray binary because bright X-ray emission from the disk is observed. Spinning material in the disk falls onto the neutron star, increasing its rotation rate. The transfer of matter eventually slows down and the remaining material is swept away by the whirling magnetic field of the neutron star as a millisecond radio pulsar forms.

The complete evolution of a low-mass X-ray binary into a millisecond pulsar should happen over several billion years, but in the course of this evolution, the system might switch rapidly between these two states. The source IGR J18245-2452 provides the first direct evidence for such drastic changes in behavior. In observations from July 2002 to May 2013 there are periods when it acts like an X-ray binary and the radio pulses disappear, and there are times when it switches off as an X-ray binary and the radio pulses turn on.

The latest observations with both X-ray and radio telescopes show that the transitions between an X-ray binary and a radio pulsar can take place in both directions and on a time scale that is shorter than expected, maybe only a few days. They also provide powerful evidence for an evolutionary link between X-ray binaries and radio millisecond pulsars.

More at http://chandra.harvard.edu/photo/2013/igr/

-Megan Watzke, CXC







Posted by Nelio Inacio at 4:12 PM 0 comments

Discover and Explore with the Chandra Skymap

Discover and Explore with the Chandra Skymap:

American Archives Month (each October) is an exciting time around here. We spend a lot of time working through the Chandra archive to bring you the best and most interesting objects in the X-ray Universe that have made their way across space and time (via photons) to Chandra's detectors.

Skymap

It has been a personal goal of mine, since taking this job as Chandra science imager about four years ago, to create an interactive tool for the public to engage with the Chandra archive of released imagery in a new and innovative way. For this to work, a few pieces of the puzzle had to fall into place.

I've blogged about metadata before and -- as you might expect -- accurate, detailed and complete metadata for our entire archive of public images is the keystone to creating a tool such as the new Chandra Skymap. Metadata is what drives all of the content behind the application. Since there's no good way to automate the “retro-tagging” (that is, tagging images we’ve already released in the past) of our image archive, it took a few years to get through all of those images by hand. We finally completed that task at the end of last year and then set our sights upon creating the Skymap tool.

There were some false starts along the way, mainly due to limitations as a programmer, learning new languages and libraries. But as I was pulling my hair out trying to figure this out last summer, a colleague recommended utilizing javascript with the D3 (Data-Driven Documents) visualization library. I was vaguely familiar with D3, mainly from playing around with interactive data visualizations published by The New York Times and written by Mike Bostock (the creator of D3). D3 turned out to be the answer to the coding problems, but the new challenge was to learn javascript. Thankfully, the D3 documentation is extensive and Mike Bostock and many other programmers have provided a wealth of resources in the form of small bits of example code that could be utilized as part of a larger project. Through all of this, I developed two new skills: first, the ability to completely tax my computer by testing how many browser tabs I could hold open at once, and, second, honing the ability to construct the perfect Google query regarding a particular javascript or D3 question. Utilizing countless examples and answers to questions on StackExchange, I was able to build the Skymap I had pictured in my head years ago. This has been an extremely rewarding and fulfilling project and I'm very excited to share this new application with you today!

Here are some helpful tips to get you started using the new Chandra Skymap:

1. Everything about this tool is interactive. You can zoom into the map using your mouse scroll wheel, or by pinch-zoom, or using the buttons at the top left. You can also pan around by clicking and dragging while in zoom-mode.

2. You'll notice that as you hover over data points, the points are highlighted and a small information window pops up with a synopsis of the press release for that particular object. Each data point is also a link to the release for that object. Click on the point and you will go to its Photo Album page.

3. The controls at the bottom offer up various ways for you to filter the data to your liking. Also note that most of the text in the controls are actually links to more information -- click on them to find out more. If you're only interested in which distant galaxies Chandra has observed, de-select everything but "Galaxies & Galaxy Clusters" in the "Categories" panel and you'll only see distant galaxies in the Skymap.

4. If you would like to filter the data by the date of the release, click and drag to draw a box in the bottom panel "Release Date Filter" and then resize to your liking or drag it across the timeline to watch press releases pop into and out of the Skymap as you pan across time.

5. You might notice that some areas are clustered with overlapping data points. Some of these are multiple releases for the same object at different times, or closely spaced but separate objects. Careful use of the zoom feature and/or filters should allow you to uncover any data point. For example, if you happen to notice two data points from two different categories overlapping each other, you can toggle the category underneath off and then on to bring it to the front. Using the "Release Data Filter" can also help to uncover buried data points.

6. If you see a term on the map that you are unfamiliar with, click on the underlined link to find out more either from the Chandra site, or from Wikipedia.

Be sure to come back often, as the Chandra Skymap will instantly populate with new releases as they are published. We also envisioned some new features that will hopefully be added in the near future.

Enjoy discovering all that Chandra has to offer!

-Joe DePasquale, CXC



Posted by Nelio Inacio at 4:12 PM 0 comments

Preserving the Legacy of the X-ray Universe

Preserving the Legacy of the X-ray Universe:

Chandra Archive Collection

Every year, October is designated as American Archive Month. While many people may think "archive" means only dusty books and letters, there are, in fact, many other types of important archives. This includes the use of archives for major telescopes and observatories like NASA's Chandra X-ray Observatory.


The Chandra Data Archive (CDA) plays a central role in the mission by enabling the astronomical community - as well as the general public - access to data collected by the observatory. The primary role of the CDA is to store and distribute data, which the CDA does with the help of powerful search engines. The CDA is one of the legacies of the Chandra mission that will serve both the scientific community and the public for decades to come.

To celebrate and support American Archive Month, we have selected images from a group of eight objects in the CDA to be released to the public for the first time. These images represent the observations of thousands of objects that are permanently available to the world thanks to Chandra's archive.

More at http://chandra.harvard.edu/photo/2013/archives/

-Megan Watzke, CXC

Posted by Nelio Inacio at 4:11 PM 0 comments

FITS and Starts

FITS and Starts:

In continued recogintion of American Archives month, we've dusted off some raw data from recent Chandra press releases over the past year for inclusion in our openFITS collection. This brings the total collection up to 20 objects including supernova remnants, active galaxies, star forming regions, black holes, and pulsars and neutron stars. These data are ripe for exploration. The new data sets include the Vela Pulsar Jet, and supernova remnants

W49B and G1.9+0.3 (which also happens to be the Milky Way's most recent supernova remnant).

W49B



W49B is a special case for openFITS. We have somewhat broken with tradition and have provided more data than what was used in creating the press image (though technically, this isn't more data, just a different representation of the same data). W49B has been extensively observed with Chandra with over 2 days worth of observation time devoted to collecting information about this source. As a result, we have a very rich data set to work with, which can be sliced and diced into many different component images emphasizing different elements emitting X-ray light. I wrote a blog post about the quality of this data and provided some behind-the-scenes insight into the image earlier this year. In creating a multi-wavelength composite image, we decided to take a "less-is-more" approach and utilize two low and high energy, broad-band X-ray images colored green and blue in combination with radio and infrared data colored magenta and yellow respectively. This allowed for a dynamic, feature-rich and aesthetically pleasing image in which the component parts were clearly distinguishable, allowing the science behind this supernova remnant to shine through.

Well, now is your chance to dig in to the X-ray data and see what you can do with up to 6 different wavelengths of X-ray light!

-Joe DePasquale, Chandra Science Imager

Posted by Nelio Inacio at 4:11 PM 0 comments

Getting a Sense of Place in our Universe

Getting a Sense of Place in our Universe:

The biggest news this week, by far, has been a new study suggesting that Earth-sized planets in habitable zones may be very common. This is exciting news – who wouldn't want to have more cosmic planetary friends out there that maybe one day we'll be able to explore? By the latest accounts, there could be billions of Earth-like planets out there in our Milky Way galaxy.

Solar System

While this is indeed mind-boggling, it got us thinking about the sheer vastness and the enormous scale of the Universe that we can explore using modern telescopes. We live in one galaxy - the Milky Way - that astronomers estimate contains roughly 400 billion stars. The Earth is not in a particularly special place in this giant collection of stars. We're about two-thirds away from the center in one of the spiral arms, in the galactic suburbs, so to speak.

What's happening in the downtown where the supermassive black hole lies and the density of stars is much higher? Chandra and other telescopes have been looking to see. We've learned an incredible amount about this area over the years with Chandra including:

- How the black hole behaves,

- What it likes to eat,

- And even what it has done hundreds of years before we had the technology to observe it.

It's very humbling to consider our small place in the very big Galaxy. It's even more so when we think about our Galaxy being just one of billions of galaxies (each of which has its own billions of stars and probably planets). Most of these galaxies aren't alone in space. Rather, they belong to groups or clusters of galaxies that are bound together by gravity. Chandra has done some amazing work studying these collections of galaxies since most of them are filled with hot gas that emits X-rays. It's hard to summarize all that the mission has done in this area of astrophysics, but a decent snapshot can be found by perusing the images we've released on the subject.

And just when you think you've wrapped your head around what the cosmos has to offer, we have to throw in the mysteries of dark energy and dark matter that account for 96% of the Universe. That's right, all of the stuff we can see with telescopes - planets, stars, galaxies, clusters - account for a mere tiny fraction of what is out there in the Universe. So take a few minutes to enjoy the incredible work Kepler is doing in discovering planets in our Galaxy, and then maybe take another one to consider how much we still have yet to explore.

-Megan Watzke, CXC







Posted by Nelio Inacio at 4:10 PM 0 comments

Exploring the Third Dimension of Cassiopeia A

Exploring the Third Dimension of Cassiopeia A:

Casa

One of the most famous objects in the sky - the Cassiopeia A supernova remnant – will be on display like never before, thanks to NASA's Chandra X-ray Observatory and a new project from the Smithsonian Institution. A new three-dimensional (3D) viewer, being unveiled today, will allow users to interact with many one-of-a-kind objects from the Smithsonian as part of a large-scale effort to digitize many of the Institutions objects and artifacts.


Scientists have combined data from Chandra, NASA's Spitzer Space Telescope, and ground-based facilities to construct a unique 3D model of the 300-year old remains of a stellar explosion that blew a massive star apart, sending the stellar debris rushing into space at millions of miles per hour. The collaboration with this new Smithsonian 3D project will allow the astronomical data collected on Cassiopeia A, or Cas A for short, to be featured and highlighted in an open-access program -- a major innovation in digital technologies with public, education, and research-based impacts.

To coincide with Cas A being featured in this new 3D effort, a specially-processed version of Chandra's data of this supernova remnant is also being released. This new image shows with better clarity the appearance of Cas A in different energy bands, which will aid astronomers in their efforts to reconstruct details of the supernova process such as the size of the star, its chemical makeup, and the explosion mechanism. The color scheme used in this image is the following: low-energy X-rays are red, medium-energy ones are green, and the highest-energy X-rays detected by Chandra are colored blue.

More at http://chandra.harvard.edu/photo/2013/casa/

-Megan Watzke, CXC







Posted by Nelio Inacio at 4:10 PM 0 comments

Carnival of Space #328

Carnival of Space #328:

Welcome to this week's Carnival of Space. It's been a busy Universe out there so let's jump right into it.

The Urban Astronomer has an excellent recap of Hubble's observations of a very unusual asteroid. This asteroid not only has a comet-like tail, it has six of them. Oh yeah, and they apparently change.

Over at the Smithsonian's Air & Space blog, they discuss a very provocative issue: if we go back to the Moon, where should we go and, maybe more importantly, where shouldn't we?

In advance of the recent Maven launch to Mars, the good folks over at Universe Today feature an excellent video that summarizes where the Curiosity rover has been and also where it will be heading in the future.

Here at the Chandra blog, we discuss how the 3D model of the Cassiopeia A supernova remnant is now being featured in an exciting new 3D viewer created by the Smithsonian that was just rolled out last week.

Casa

The Here, There, and Everywhere (HTE) project traveled to the Phillips Library in Aurora, Illinois, and you can find out the reaction to the exhibit at the HTE blog.

Saturn

The stunning new image of Saturn (and Mars, Venus, and the Earth too) is highlighted in this post of the Meridian Journal. Learn more about this image that made the rounds of many news outlets and websites last week.

The Next Big Thing (NBT) looks at current research and testing being done to determine the best ways to bring back sample returns from destinations such as the Moon and asteroids. The NBT also reports that NBC will follow Virgin Galactic's development of SpaceShipTwo and broadcast Richard Branson and his children going into orbit in August 2014.

Stay tuned for more news from our very own Universe.

-Megan Watzke, CXC
Posted by Nelio Inacio at 4:09 PM 0 comments

Getting the Upper Hand on Understanding Neutron Stars

Getting the Upper Hand on Understanding Neutron Stars:

posted by chandra
on Wed, 2013-12-11 16:30


PSR B1509-58

When we released Chandra’s image of the pulsar known as PSR B1509-58 (or, B1509, for short), it received a lot of attention. It's a fascinating object. The pulsar at the center of the image is a rapidly spinning dense star that is spewing out energetic particles into beautiful structures spanning trillions of miles that glow in X-ray light. And, it looks like a giant hand. This fact helped trigger a whole host of other comments about this object found some 17,000 light years from Earth.

This month, scientists announced that they've been studying B1509 for reasons that have nothing to do with its hand-shaped appearance. Rather, they are trying to figure out how such a tiny object (the 12-mile-wide pulsar) can be so powerful. Researchers at the Los Alamos National Laboratory in New Mexico put out a press release that talks about this fascinating work.

In short, neutron stars like the one found in B1509 give scientists an opportunity to study forces in nature so extreme that they are impossible to recreate here on Earth.

This is an exciting and important example of how science in space can help research here on the ground, and vice versa. That's just the hand we've been dealt in our Universe (ba-da-dum).

-Megan Watzke, CXC
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Doubling Down With Rare White Dwarf Systems

Doubling Down With Rare White Dwarf Systems:

amcvn

In the middle of the twentieth century, an unusual star was spotted in the constellation of Canes Venatici (Latin for "hunting dogs"). Years later, astronomers determined that this object, dubbed AM Canum Venaticorum (or, AM CVn, for short), was, in fact, two stars. These stars revolve around each other every 18 minutes, and are predicted to generate gravitational waves - ripples in space-time predicted by Einstein.

The name AM CVn came to represent a new class of objects where one white dwarf star is pulling matter from a very compact companion star, such as a second white dwarf. (White dwarf stars are dense remains of Sun-like stars that have run out of fuel and collapsed to the size of the Earth.) The pairs of stars in AM CVn systems orbit each other extremely rapidly, whipping around one another in an hour, and in one case as quickly as five minutes. By contrast, the fastest orbiting planet in our Solar System, Mercury, orbits the Sun once every 88 days.

Despite being known for almost 50 years, the question has remained: where do AM CVn systems come from? New X-ray and optical observations have begun to answer that with the discovery of the first known systems of double stars that astronomers think will evolve into AM CVn systems.

The two binary systems - known by their shortened names of J0751 and J1741 - were observed in X-rays by NASA's Chandra X-ray Observatory and ESA's XMM-Newton telescope. Observations at optical wavelengths were made using the McDonald Observatory's 2.1-meter telescope in Texas, and the Mt. John Observatory 1.0-meter telescope in New Zealand.

The artist's illustration depicts what these systems are like now and what may happen to them in the future. The top panel shows the current state of the binary that contains one white dwarf (on the right) with about one-fifth the mass of the Sun and another much heavier and more compact white dwarf about five or more times as massive (unlike Sun-like stars, heavier white dwarfs are smaller).

More at http://chandra.harvard.edu/photo/2013/amcvn/

-Megan Watzke, CXC

Posted by Nelio Inacio at 4:08 PM 0 comments

Finding Patterns

Finding Patterns:

Clouds

Image: Frank Kovalchek, Wikimedia Commons

One of our favorite games to play with our kids is trying to find recognizable objects in clouds as they pass by on a sunny day. One cloud might look like an elephant, the next, a pirate ship.

The phenomenon where our brains find seemingly significant patterns in images or sounds has an actual name: pareidolia. For example, we might think we see a human on the face of the Moon, a lizard on Mars (see below) or recognize words when we play a recording in reverse. Even Leonardo da Vinci – a man of many talents - suggested that artists could use pareidolia as a creative exercise for painting.

NASA's Curiosity Image of Mars
pareidolia

Image: NASA/JPL-Caltech

One of our favorite places to experiment with pareidolia is in images from space. Take a look at this image of the object known as B1509-58, which was released from NASA's Chandra X-ray Observatory back in 2009.

B1509-58

Credit: NASA/CXC/SAO/P.Slane, et al.

Not surprisingly, this object was nicknamed the “Hand of God,” which quickly became a much more popular name than its slightly dull astronomical handle.

At the center of B1509 is a tiny dense spinning dead star known as a pulsar. This little dynamo is responsible for spewing energized particles that, in turn, are responsible for the “fingers” and other structures seen in this X-ray image. Even though scientists can explain this object’s shape without any references to extremities or deities, pareidolia is alive and well. http://chandra.harvard.edu/photo/2009/b1509/

There have been many posts about pareidolia in astronomy images and you can read some great examples here and here.

Here we present our version of cosmic cloud watching, but with Chandra, Spitzer or Hubble images. Starting at the top, we’ve placed the strongest visual objects (to us). Towards the end of the list, you might have to get more creative to find some shapes.

Horsehead Nebula

This object is probably the most obviously named. The image of a horse's head and neck is iconic and has been published in many forms over the past 100 years since its discovery. Hubble's latest image of the Horsehead Nebula shows it in infrared light where we get to see pillars of gas and dust formed by stellar winds and radiation.

What we see: a horse's head and neck.

Horsehead Nebula

Image: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

Circinus X-1

A system where a neutron star is in orbit around a star several times the mass of the Sun, about 20,000 light years from Earth, within our Milky Way Galaxy.

Circinus X-1

Image: X-ray: NASA/CXC/Univ. of Wisconsin-Madison/S.Heinz et al; Optical: DSS; Radio: CSIRO/ATNF/ATCA

What we see: A skull!

Colliding Galaxy Pair

What looks like a celestial hummingbird is really the result of a collision between a spiral and an elliptical galaxy at a whopping 326 million light- years away. The flat disk of the spiral NGC 2936 is warped into the profile of a bird by the gravitational tug of the companion NGC 2937. The object was first cataloged as a "peculiar galaxy" by Halton Arp in the 1960s. This interacting galaxy duo is collectively called Arp 142.

Arp 142

Image: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

What we see. Definitely a penguin’s head coming out of the water.

NGC 602

The Small Magellanic Cloud - also known as the SMC - is one of the closest galaxies to the Milky Way. Because the SMC is so close and bright, it offers a chance to study phenomena that are difficult to examine in more distant galaxies. This image, a composite of X-ray, infrared and optical data, shows a cluster of bright young stars with masses similar to that of our Sun.

NGC 602

Image: X-ray: NASA/CXC/Univ.Potsdam/L.Oskinova et al; Optical: NASA/STScI; Infrared: NASA/JPL-Caltech

What we see: Many people see a face, but we see a Pac man eating its dots.

Eta Carinae

Eta Carinae is a mysterious, extremely bright and unstable star located a mere stone's throw - astronomically speaking - from Earth at a distance of only about 7,500 light years. Eta Carinae is about 100 times bigger than our sun and is burning about one million times brighter than our own star. Radiation and stellar winds from Eta Carinae are sculpting and destroying the surrounding nebula, shown here in this infrared image of its gas and dust.

Eta Carinae

Image: NASA/JPL-Caltech

What we see. A person, in the carved out green areas inside the nebula.

W49b

Supernova remnants—that is, the debris field left behind after the explosion—are like snowflakes: No two are ever exactly the same. W49b has evolved into an unusual shape. Its expanding shell of gas contains important elements such as sulfur and silicon, oxygen and iron. These elements, which are critical to our existence here are Earth, were created both when the star was still living and in the explosion itself.

W49b

Image: X-ray: NASA/CXC/MIT/L.Lopez et al.; Infrared: Palomar; Radio: NSF/NRAO/VLA

What we see: Could be a flying bat.

On Pinterest? Pin horseheads and faces from http://www.pinterest.com/kimberlyarcand/2013-interesting-astronomy-images/

-Kim Arcand & Megan Watzke, CXC

Adapted from an earlier blog post at http://www.huffingtonpost.com/kimberly-k-arcand/i-spy-a-horses-head_b_45...
Posted by Nelio Inacio at 4:06 PM 0 comments

Extreme Power of Black Hole Revealed

Extreme Power of Black Hole Revealed:

RX J1532

Astronomers have used NASA's Chandra X-ray Observatory and a suite of other telescopes to reveal one of the most powerful black holes known. The black hole has created enormous structures in the hot gas surrounding it and prevented trillions of stars from forming.

The black hole is in a galaxy cluster named RX J1532.9+3021 (RX J1532 for short), located about 3.9 billion light years from Earth. The image here is a composite of X-ray data from Chandra revealing hot gas in the cluster in purple and optical data from the Hubble Space Telescope showing galaxies in yellow. The cluster is very bright in X-rays implying that it is extremely massive, with a mass about a quadrillion - a thousand trillion - times that of the sun. At the center of the cluster is a large elliptical galaxy containing the supermassive black hole.

The large amount of hot gas near the center of the cluster presents a puzzle. Hot gas glowing with X-rays should cool, and the dense gas in the center of the cluster should cool the fastest. The pressure in this cool central gas is then expected to drop, causing gas further out to sink in towards the galaxy, forming trillions of stars along the way. However, astronomers have found no such evidence for this burst of stars forming at the center of this cluster.

This problem has been noted in many galaxy clusters but RX J1532 is an extreme case, where the cooling of gas should be especially dramatic because of the high density of gas near the center. Out of the thousands of clusters known to date, less than a dozen are as extreme as RX J1532. The Phoenix Cluster is the most extreme, where, conversely, large numbers of stars have been observed to be forming.

More at http://chandra.harvard.edu/photo/2014/rxj1532/

-Megan Watzke, CXC
Posted by Nelio Inacio at 4:05 PM 0 comments

A New Look at an Old Friend

A New Look at an Old Friend:

Cena A

Astronomers have used NASA's Chandra X-ray Observatory and a suite of other telescopes to reveal one of the most powerful black holes known. The black hole has created enormous structures in the hot gas surrounding it and prevented trillions of stars from forming.

The black hole is in a galaxy cluster named RX J1532.9+3021 (RX J1532 for short), located about 3.9 billion light years from Earth. The image here is a composite of X-ray data from Chandra revealing hot gas in the cluster in purple and optical data from the Hubble Space Telescope showing galaxies in yellow. The cluster is very bright in X-rays implying that it is extremely massive, with a mass about a quadrillion - a thousand trillion - times that of the sun. At the center of the cluster is a large elliptical galaxy containing the supermassive black hole.

The large amount of hot gas near the center of the cluster presents a puzzle. Hot gas glowing with X-rays should cool, and the dense gas in the center of the cluster should cool the fastest. The pressure in this cool central gas is then expected to drop, causing gas further out to sink in towards the galaxy, forming trillions of stars along the way. However, astronomers have found no such evidence for this burst of stars forming at the center of this cluster.

This problem has been noted in many galaxy clusters but RX J1532 is an extreme case, where the cooling of gas should be especially dramatic because of the high density of gas near the center. Out of the thousands of clusters known to date, less than a dozen are as extreme as RX J1532. The Phoenix Cluster is the most extreme, where, conversely, large numbers of stars have been observed to be forming.

More at http://chandra.harvard.edu/photo/2014/cena/

-Megan Watzke, CXC
Posted by Nelio Inacio at 4:04 PM 0 comments

Runaway Pulsar Firing an Extraordinary Jet

Runaway Pulsar Firing an Extraordinary Jet:

IGR J11014

An extraordinary jet trailing behind a runaway pulsar is seen in this composite image that contains data from NASA's Chandra X-ray Observatory (purple), radio data from the Australia Compact Telescope Array (green), and optical data from the 2MASS survey (red, green, and blue). The pulsar - a spinning neutron star - and its tail are found in the lower right of this image (mouse over the image for a labeled version). The tail stretches for 37 light years , making it the longest jet ever seen from an object in the Milky Way galaxy, as described in our press release.

The pulsar, originally discovered by ESA's INTEGRAL satellite, is called IGR J1104-6103 and is moving away from the center of the supernova remnant where it was born at a speed between 2.5 million and 5 million miles per hour. This supersonic pace makes IGR J1104-6103 one of the fastest moving pulsars ever observed.

A massive star ran out of fuel and collapsed to form the pulsar along with the supernova remnant, the debris field seen as the large purple structure in the upper left of the image. The supernova remnant (known as SNR MSH 11-61A) is elongated along the top-right to bottom left direction, roughly in line with the tail's direction. These features and the high speed of the pulsar suggest that jets could have played an important role in the supernova explosion that formed IGR J1104-6103.

In addition to its exceptional length, the tail behind IGR J1104-6103 has other interesting characteristics. For example, there is a distinct corkscrew pattern in the jet. This pattern suggests that the pulsar is wobbling like a top as it spins, while shooting off the jet of particles.

More at http://chandra.harvard.edu/photo/2014/igrj11014/

-Megan Watzke, CXC
Posted by Nelio Inacio at 4:04 PM 0 comments

Life Is Too Fast, Too Furious for This Runaway Galaxy

Life Is Too Fast, Too Furious for This Runaway Galaxy:

posted by chandra
on Tue, 2014-03-04 16:57


ESO 137-001

The spiral galaxy ESO 137-001 looks like a dandelion caught in a breeze in this new composite image from the Hubble Space Telescope and the Chandra X-ray Observatory.

The galaxy is zooming toward the upper right of this image, in between other galaxies in the Norma cluster located over 200 million light-years away. The road is harsh: intergalactic gas in the Norma cluster is sparse, but so hot at 180 million degrees Fahrenheit that it glows in X-rays detected by Chandra (blue).

The spiral plows through the seething intra-cluster gas so rapidly - at nearly 4.5 million miles per hour - much of its own gas is caught and torn away. Astronomers call this "ram pressure stripping." The galaxy's stars remain intact due to the binding force of their gravity.

Tattered threads of gas, the blue jellyfish-tendrils sported by ESO 137-001 in the image, illustrate the process. Ram pressure has strung this gas away from its home in the spiral galaxy and out over intergalactic space. Once there, these strips of gas have erupted with young, massive stars, which are pumping out light in vivid blues and ultraviolet.

More at http://chandra.harvard.edu/photo/2014/eso137/

-Megan Watzke, CXC
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Posted by Nelio Inacio at 4:03 PM 0 comments

Chandra & XMM-Newton Provide Direct Measurement of Distant Black Hole's Spin

Chandra & XMM-Newton Provide Direct Measurement of Distant Black Hole's Spin:

RX J1131

Multiple images of a distant quasar are visible in this combined view from NASA's Chandra X-ray Observatory and the Hubble Space Telescope. The Chandra data, along with data from ESA's XMM-Newton, were used to directly measure the spin of the supermassive black hole powering this quasar. This is the most distant black hole where such a measurement has been made, as reported in our press release.

Gravitational lensing by an intervening elliptical galaxy has created four different images of the quasar, shown by the Chandra data in pink. Such lensing, first predicted by Einstein, offers a rare opportunity to study regions close to the black hole in distant quasars, by acting as a natural telescope and magnifying the light from these sources. The Hubble data in red, green and blue shows the elliptical galaxy in the middle of the image, along with other galaxies in the field.

The quasar is known as RX J1131-1231 (RX J1131 for short), located about 6 billion light years from Earth. Using the gravitational lens, a high quality X-ray spectrum - that is, the amount of X-rays seen at different energies - of RX J1131 was obtained.

The X-rays are produced when a swirling accretion disk of gas and dust that surrounds the black hole creates a multimillion-degree cloud, or corona near the black hole. X-rays from this corona reflect off the inner edge of the accretion disk. The reflected X-ray spectrum is altered by the strong gravitational forces near the black hole. The larger the change in the spectrum, the closer the inner edge of the disk must be to the black hole.

The authors of the new study found that the X-rays are coming from a region in the disk located only about three times the radius of the event horizon, the point of no return for infalling matter. This implies that the black hole must be spinning extremely rapidly to allow a disk to survive at such a small radius.

More at http://chandra.harvard.edu/photo/2014/rxj1131/

-Megan Watzke, CXC
Posted by Nelio Inacio at 4:03 PM 0 comments

What Makes an Astronomical Image Beautiful?

What Makes an Astronomical Image Beautiful?:

Submitted by chandra on Wed, 03/12/2014 - 14:19.

Astronomy is renowned for the beautiful images it produces. It's not hard to be impressed by an image like the Pillars of Creation or the Bullet Cluster, and the more eye-catching an image is, the bigger an audience it can potentially reach. So, as part of our job in astronomy outreach, we have each spent time thinking about what makes an astronomy image beautiful. As professionals, we’d like to go well beyond the intuition of the person who says, "I don't know anything about art, but I know what I like". One approach(1) is to list the key elements that make an image beautiful.

Two famous images, the Pillars of Creation from the Hubble Space Telescope on the left and the Bullet Cluster from the Chandra X-ray Observatory, Hubble and ground-based observatories on the right. Credit: left: NASA, ESA, STScI, J. Hester and P. Scowen (Arizona State University); right: X-ray: NASA/CXC/CfA/M.Markevitch et al.; Optical: NASA/STScI; Magellan/U.Arizona/D.Clowe et al.; Lensing Map: NASA/STScI; ESO WFI; Magellan/U.Arizona/D.Clowe et al.

Lars Lindberg Christensen and collaborators have done just that, in an excellent paper in the most recent issue of the open journal "Communicating Astronomy with the Public". After years of experience working with images from the Hubble Space Telescope, they have defined a set of 6 criteria that are important in determining the appeal of an astronomical image. These 6 criteria are photogenic resolution (equivalent to the number of stars which can fit side by side across an image), definition (the amount of structure or contrast in an image), color, composition (how the object or objects of interest fill the field of view), signal-to-noise ratio, and how well instrumental artifacts have been removed.

Here, I'll highlight a few of these criteria and how they relate to the images we make with Chandra data. There are some key differences between the optical or infrared data obtained with telescopes like Hubble or the Spitzer Space Telescope, and the X-ray data obtained with Chandra.

For the photogenic resolution they define a quantity rphoto that is the number of effective resolution elements across the field of view (FOV). The equation is rphoto=FOV/θeffective, where θeffective is the effective angular resolution. A higher rphoto results in a better quality image. So one tactic is to push for a very large FOV by making a mosaic of a large number of adjacent images, as some amateur astronomers do, or as Chandra users did to make a large mosaic of the Carina Nebula. The other option is to use data from a telescope with a very small θeffective, where Hubble is unsurpassed at optical wavelengths and Chandra is unsurpassed at X-ray wavelengths.



A mosaic of Chandra images of the Carina Nebula. Credit: NASA/CXC/PSU/L.Townsley et al.

The authors point out that the domain with high values of the photogenic resolution - between 1000 and 10,000 - was dominated for many years by Hubble, but that more recently other observatories such as Chandra, the MPG/ESO 2.2-meter telescope, the Canada France Hawaii Telescope and ESO's VISTA and VST telescopes have joined Hubble. We're happy to have been included in this elite group.

To make a color image using optical or infrared data, observations have to be made using different filters chosen in advance, such as B (blue), V (visual) and R (red). A color is then assigned to the image obtained with each filter – in this case blue, green and red are the obvious choices – and the images are combined to make a color image. With Chandra, the energy (or wavelength) of individual photons is recorded, so different wavelength ranges can be chosen afterwards, giving us extra flexibility in making an image. By picking out different wavelength ranges the same dataset can be used to show different features, so we can experiment to see what makes the most striking image, or the most useful one to explain a particular science result. The greatest flexibility with choosing different wavelength ranges comes when the signal-to-noise ratio is high.

This leads me to describe the main challenge for producing beautiful Chandra images: sometimes the signal-to-noise ratio isn't high. X-ray photons trace energetic events, such as regions close to a black hole, or the exploded guts of a massive star, but they tend to arrive from the cosmos in a trickle, rather than a flood. This limitation was most apparent early in the mission, when lots of different targets were observed and Chandra's observations usually involved short exposures. Later in the mission much deeper observations have been done, giving much higher signal-to-noise ratios and better images. For example, you can see the dramatic difference between these two images of the supernova remnant Cassiopeia A. The early Chandra image shown on the left had an exposure time of only 2 hours and doesn't look nearly as photogenic as a later image shown on the right, with an exposure time of 11 1/2 days.

Images of the supernova remnant Cassiopeia A. A comparison is shown between an early, short exposure (2 hr) Chandra image (left) and a later, deeper exposure (11.5 days; right). Credit: left: NASA/CXC/SAO/Rutgers/J.Hughes; right: NASA/CXC/MIT/UMass Amherst/M.D.Stage et al.

The signal-to-noise ratio is connected to the 2nd criterion, the definition in an image. If the signal-to-noise ratio is low because few counts have been detected, then this can seriously limit the amount of detailed structure that you can see in an image. Think about how much detail you can see in a painting that is well lit, compared to looking at one in the dark. Again, deep exposures help a lot. The deep observation of Cas A has significantly sharper features and more complicated structure than the shallow one.

Only a limited number of very deep observations can be made with Chandra each year. This means there is intense competition between astronomers to convince the members of the Chandra Time Assignment Committee to approve any observing proposals requiring a lot of observing time. Therefore, the science case has to be particularly strong, which becomes an advantage for us, because it means that we can publicize interesting science at the same time as showing off beautiful new images.

When we have only low signal-to-noise X-ray data to work with, we sometimes combine it with optical or infrared images, to capitalize on the high signal-to-noise in these other wavelengths. This can give a striking image, such as in this view of NGC 602.



A composite image of the star-forming region NGC 602, with Chandra X-ray data shown in purple, Hubble optical data shown in red, green and blue, and Spitzer infrared data shown in red. Credit: X-ray: NASA/CXC/Univ.Potsdam/L.Oskinova et al; Optical: NASA/STScI; Infrared: NASA/JPL-Caltech.

The final criterion is instrumental artifact removal, where the relatively low count rates for Chandra are an advantage. When you detect a lot of very bright objects you tend to accumulate a lot of artifacts, so optical observations can require a lot of clean-up work. According to Christensen et al., one to two hundred hours can be spent manually cleaning a large image. Chandra images aren't free of artifacts, but they're not as much of a problem.

In their conclusion, Christensen et al. explain that the ideal case is for all six criteria to be fulfilled, giving a great image. It’s still possible to produce a great image with less, but it becomes more difficult and compromises have to be made, as they note.

Having explained some of the factors that help us produce beautiful Chandra images, we invite you to explore our photo album of images or our 3D image wall.

----------------------------

(1): In this blog post I've discussed only one approach for thinking about how beautiful an image is. There are other approaches that consider aesthetics in general. My colleague Kimberley Arcand is involved in a project called "Aesthetics and Astronomy" which studies “the perception of multi-wavelength astronomical imagery and the effects of the scientific and artistic choices in processing astronomical data.”

-Peter Edmonds, CXC
Posted by Nelio Inacio at 4:02 PM 0 comments

Hardy Star Survives Supernova Blast

Hardy Star Survives Supernova Blast:

Submitted by chandra on Thu, 03/20/2014 - 14:01.

deml241

When a massive star runs out fuel, it collapses and explodes as a supernova. Although these explosions are extremely powerful, it is possible for a companion star to endure the blast. A team of astronomers using NASA's Chandra X-ray Observatory and other telescopes has found evidence for one of these survivors.

This hardy star is in a stellar explosion's debris field - also called its supernova remnant - located in an HII region called DEM L241. An HII (pronounced "H-two") region is created when the radiation from hot, young stars strips away the electrons from neutral hydrogen atoms (HI) to form clouds of ionized hydrogen (HII). This HII region is located in the Large Magellanic Cloud, a small companion galaxy to the Milky Way.

A new composite image of DEM L241 contains Chandra data (purple) that outlines the supernova remnant. The remnant remains hot and therefore X-ray bright for thousands of years after the original explosion occurred. Also included in this image are optical data from the Magellanic Cloud Emission Line Survey (MCELS) taken from ground-based telescopes in Chile (yellow and cyan), which trace the HII emission produced by DEM L241. Additional optical data from the Digitized Sky Survey (white) are also included, showing stars in the field.

More at http://chandra.harvard.edu/photo/2014/deml241/

-Megan Watzke, CXC
Posted by Nelio Inacio at 4:01 PM 0 comments

Monster "El Gordo" Galaxy Cluster is Bigger than Thought

Monster "El Gordo" Galaxy Cluster is Bigger than Thought:

posted by chandra
on Thu, 2014-04-03 11:22


El Gordo

This is a composite image of X-rays from Chandra and optical data from Hubble of the galaxy cluster ACT-CL J0102-4915, located about 7 billion light years from Earth. This cluster has been nicknamed "El Gordo" (or, "the fat one" in Spanish) because of its gigantic mass.

Scientists first announced the discovery of El Gordo with Chandra and ground-based optical telescopes in 2012. They determined that El Gordo is the most massive, the hottest, and gives off the most X-rays of any known galaxy cluster at its distance or beyond.

New data from the Hubble Space Telescope suggests El Gordo weighs as much as 3 million billion times the mass of our Sun. This is about 43 percent higher than the original estimate based on the X-ray data and dynamical studies.

More at http://chandra.harvard.edu/photo/2014/elgordo/

-Megan Watzke, CXC
Disclaimer: This service is provided as a free forum for registered users. Users' comments do not reflect the views of the Chandra X-ray Center and the Harvard-Smithsonian Center for Astrophysics.

Please note this is a moderated blog. No pornography, spam, profanity or discriminatory remarks are allowed. No personal attacks are allowed. Users should stay on topic to keep it relevant for the readers.

Read the privacy statement
Posted by Nelio Inacio at 4:01 PM 0 comments
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