Wednesday, July 16, 2014

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
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Posted by Nelio Inacio at 4:01 PM 0 comments

Supernova Cleans Up its Surroundings

Supernova Cleans Up its Surroundings:

G352.7-0.1

Supernovas are the spectacular ends to the lives of many massive stars. These explosions, which occur on average twice a century in the Milky Way, can produce enormous amounts of energy and be as bright as an entire galaxy. These events are also important because the remains of the shattered star are hurled into space. As this debris field - called a supernova remnant - expands, it carries the material it encounters along with it.

Astronomers have identified a supernova remnant that has several unusual properties. First, they found that this supernova remnant - known as G352.7-0.1 (or, G352 for short) - has swept up a remarkable amount of material, equivalent to about 45 times the mass of the Sun.

Another atypical trait of G352 is that it has a very different shape in radio data compared to that in X-rays. Most of the radio emission is shaped like an ellipse, contrasting with the X-ray emission that fills in the center of the radio ellipse. This is seen in a new composite image of G352 that contains X-rays from NASA's Chandra X-ray Observatory in blue and radio data from the National Science Foundation's Karl G. Jansky Very Large Array in pink. These data have also been combined with infrared data from the Spitzer Space Telescope in orange, and optical data from the Digitized Sky Survey in white. (The infrared emission to the upper left and lower right are not directly related to the supernova remnant.)

A recent study suggests that, surprisingly, the X-ray emission in G352 is dominated by the hotter (about 30 million degrees Celsius) debris from the explosion, rather than cooler (about 2 million degrees) emission from surrounding material that has been swept up by the expanding shock wave. This is curious because astronomers estimate that G352 exploded about 2,200 years ago, and supernova remnants of this age usually produce X-rays that are dominated by swept-up material. Scientists are still trying to come up with an explanation for this behavior.

More at http://chandra.harvard.edu/photo/2014/g352/

-Megan Watzke, CXC
Posted by Nelio Inacio at 4:00 PM 0 comments

Professional and Amateur Astronomers Join Forces

Professional and Amateur Astronomers Join Forces:

Pro-Am

We are perhaps living in the midst of a new "Golden Age" of astronomy. In the four hundred years since Galileo first trained his refracting optical telescope on the Moon, and Jupiter and its moons, we've seen staggering advances in the technology of telescopes. We've also benefited from the discoveries of light beyond the visible portions of the electromagnetic spectrum and the development of instruments sensitive to those wavelengths.

NASA developed and implemented its Great Observatories program to extend our view of the Universe far beyond that which our human eyes can see, giving us glimpses of the cosmos beyond our ancestors' wildest dreams. Over the past two decades, advancements in professional-grade detectors, optics and computing power have been welcomed by amateur astronomers as well. With a modest investment and a great deal of patience, a dedicated amateur astronomer can produce images that rival those of professional ground-based observatories from just ten years ago. In the spirit of Global Astronomy Month 2014, we present four views of our cosmos brought to you by NASA and two very dedicated amateur astronomers, Detlef Hartmann and Rolf Olsen, in an Astro Pro-Am collaboration.

After I spoke at the NorthEast Astro Imaging Conference in 2013, I decided to further investigate the depth and quality of both professional and amateur data that is available to anyone willing to do a little digging. I chose this as an opportunity to help forge a relationship between amateur astrophotographers and NASA by identifying several high-quality images that would be ideal candidates for a multi-wavelength, professional-amateur (or “pro-am”) collaboration. This was also a great venue to raise interest and awareness among the amateur astronomer/astrophotographer community as to the wealth of data available in NASA's various mission archives. People are often surprised when they learn that data from NASA's Great Observatories program is free to use.

I sought out the work of talented astrophotographers on astrobin, which eventually led me to the work of Detlef Hartmann. I reached out to Detlef regarding a possible collaboration combining his excellent work with data from Chandra and possibly other NASA observatories. He was enthusiastic about the idea and so we got to work identifying potential image candidates, most of which had very good X-ray data from Chandra and infrared data from NASA's Spitzer Space Telescope available. Detlef utilizes his own remote observatory in the Austrian Alps, which affords him the ability to take very long exposures in very good seeing conditions thus producing stunning images. This is a common theme among amateur astrophotographers that sets them apart from the professional observatories that are often oversubscribed and for which it is difficult to devote large amounts of time to one research project; amateur astronomers have the luxury of time.

Pro-Am
Centaurus A - Optical

It was by chance that I came across this blog post by "Bad Astronomer" Phil Plait detailing an amazing optical image of Cen A by Rolf Olsen. This extremely deep image of Cen A teases out the faintest details in the extended structure of this galaxy - all from a 10" telescope that Rolf built himself! In an effort to extend this Pro-Am collaboration to other astrophotographers, I contacted Rolf to see if he would be interested in working together on a multi-wavelength image of Cen-A and was met with the same enthusiastic response as Detlef's. We iterated a few times on an image combining Rolf's amazing work with our newly updated, deeper X-ray image, and again infrared data from Spitzer. Cen A is famous for its bright X-ray jet, but if you look very closely at Rolf's image, he also managed to capture faint evidence of that same jet in optical wavelengths as well.

This image release is hopefully the beginning of a fruitful collaboration with amateur astronomers around the world. We hope to release more images in the future. In the meantime, enjoy these four images and keep looking up!

-Joe DePasquale, Chandra Science Imager
Posted by Nelio Inacio at 4:00 PM 0 comments

Core-Halo Age Gradients in Young Stellar Clusters

Core-Halo Age Gradients in Young Stellar Clusters:

We are delighted to welcome a trio of guest bloggers to discuss their work related to the newest Chandra press release on star clusters and star formation. Konstantin Getman, Eric Feigelson, and Michael Kuhn are colleagues at Penn State University and are all involved in the Massive Young Star-Forming Complex Study in Infrared and X-ray (MYStIX) project led from that institution.

Mike Eric Kosta
Figure 1: From left to right, Michael Kuhn, Eric Feigelson, and Konstantin Getman.

For decades there has been much debate about how clusters of stars form from molecular clouds. In the simplest case of a small gravitationally collapsing cloud, a single star cluster ’rapidly’ forms during a few hundred thousand years. But in the case of star formation distributed in a filamentary and turbulent cloud, which may be more realistic for giant molecular clouds, multiple small clusters may form over a period of million(s) of years, later interacting and merging to form a single massive star cluster.

Wide age spreads for young stars in clusters are found using traditional age methods, and would seem to support the slow mode of star formation. For instance, recent optical studies of the nearest rich young stellar cluster, the Orion Nebula Cluster (ONC), often considered to be a benchmark of star formation, based on the optical ground-based and Hubble Space Telescope data find that the cluster has a mean age of around 2 million years and an age spread of 2-3 million years around the mean. However, several problems affect the age estimate analysis in ONC. Firstly, the optical data are blinded by the bright gas near the cluster core, thus missing many stellar members in the center. Secondly, the age estimates for individual stars could be highly uncertain. It thus can be difficult to disentangle real astrophysical ages from the observed age spread in the cluster.

In this context, we present a new estimator of pre-main sequence stellar ages derived from X-ray and near-infrared (NIR) properties of young stars that can be applied to more distant and obscured clusters than the nearby ONC. The method is also less sensitive to Galactic field stars and bright background light from the nebula. When applied to the ONC, our Chandra-based sample has nearly uniform sensitivity to young stars across the entire cluster. And instead of evaluating the age spread for individual stars, we estimate median ages of stars in rings at different distances from the center of the cluster (Figure 2). By doing so we discover that the core of the ONC cluster is younger (1.2 million years old) than the halo of the cluster (about 2 million years old). We obtain even more dramatic results – with a core only 0.2 Myr old – for the second-richest cluster in the Orion Molecular Clouds, NGC 2024 associated with Flame Nebula.

The first implication of our results is that age spreads in young stellar clusters are real: they do not arise from a single nearly-instantaneous burst of star formation. If clusters truly formed exceedingly rapidly, our age estimates for different cluster subregions would be similar. Our results, however, do not specify a precise mechanism of asynchronous formation. Perhaps star formation continues longer in the core region, accelerating until the gas is depleted. Perhaps gaseous filaments feed material for continued star formation into the core. Perhaps older stars are ejected into the cluster halo during subcluster mergers. Or perhaps all of these mechanisms are involved.

We hope that computer simulations of the movement of cloud material and newborn stars can now focus on reproducing our results for the Orion and Flame Nebula clusters to give realistic understanding of cluster formation processes. And we will extend our empirical studies to other rich young stellar clusters in the solar neighborhood.

ONC

Figure 2: Chandra images of the ONC (left) and NGC 2024 (right) young stellar clusters. Rings at different distances from the centre of the cluster used in our age analysis are marked by the ellipses of different colors. The numbers state our derived median ages for the stars (in million years) within the different rings of the clusters.
Posted by Nelio Inacio at 3:59 PM 0 comments

NASA's Chandra Delivers New Insight into Formation of Star Clusters

NASA's Chandra Delivers New Insight into Formation of Star Clusters:

Flame Nebula

Stars are often born in clusters, in giant clouds of gas and dust. Astronomers have studied two star clusters using NASA's Chandra X-ray Observatory and infrared telescopes and the results show that the simplest ideas for the birth of these clusters cannot work, as described in our latest press release.

This composite image shows one of the clusters, NGC 2024, which is found in the center of the so-called Flame Nebula about 1,400 light years from Earth. In this image, X-rays from Chandra are seen as purple, while infrared data from NASA's Spitzer Space Telescope are colored red, green, and blue.

A study of NGC 2024 and the Orion Nebula Cluster, another region where many stars are forming, suggest that the stars on the outskirts of these clusters are older than those in the central regions. This is different from what the simplest idea of star formation predicts, where stars are born first in the center of a collapsing cloud of gas and dust when the density is large enough.

The research team developed a two-step process to make this discovery. First, they used Chandra data on the brightness of the stars in X-rays to determine their masses. Next, they found out how bright these stars were in infrared light using data from Spitzer, the 2MASS telescope, and the United Kingdom Infrared Telescope. By combining this information with theoretical models, the ages of the stars throughout the two clusters could be estimated.

According to the new results, the stars at the center of NGC 2024 were about 200,000 years old while those on the outskirts were about 1.5 million years in age. In Orion, the age spread went from 1.2 million years in the middle of the cluster to nearly 2 million years for the stars toward the edges.

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

-Megan Watzke, CXC
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Chandra "Enthusiastically Endorsed" for Extension in Senior Review

Chandra "Enthusiastically Endorsed" for Extension in Senior Review:

Peter Edmonds is the Chandra Press Scientist and, in addition to his work on publicizing Chandra science, has been heavily involved with the Chandra's Senior Review proposal since 2008.

In science, "peer review" is used to describe a process that determines whether a research paper should be published in a journal. One or more experts review the paper and determine its fate: are the results and discussion reliable and do they meet the publication standards of the journal?

This process plays a crucial role in advancing scientific research and accordingly it receives a lot of attention, especially in efforts to improve it. However, peer review is just one example, in science, where experts perform reviews. In astronomy there are committees that review telescope proposals and panels that review the performance and determine the fate of entire observatories. NASA's Senior Review is an important example of the latter. Last week the Chandra X-ray Observatory, along with the Hubble Space Telescope (HST) and many other NASA missions, received reports responding to their 2014 Senior Review proposals. We are delighted to report that the Chandra mission received a glowing endorsement.

The goal of Senior Review, according to NASA, is "to maximize the scientific return from these programs within finite resources". In other words, NASA wants to get the most science possible out of their limited budget. Chandra has gone through this process every two years since 2008 and has performed very well each time.

Senior Review
Figure: The cover page of the Chandra proposal to NASA’s Senior Review for 2014. Credit: NASA/CXC.

As with previous years, the 2014 Senior Review proposal included a science section describing research highlights since the last Senior Review and a discussion of likely future results; a technical section describing the status of functions such as mission operations, spacecraft health, data collection and archiving and a detailed budget. This year there was also a two-day long site visit.

The full report on Chandra is available here, including the membership of the expert panel that performed the review. I've picked out a few highlights of the report concerning the quality of Chandra’s scientific accomplishments and our communication efforts in Education and Public Outreach (EPO), and the high demand for Chandra observing time:

Chandra "has a large community of users who continue to produce groundbreaking scientific results. Chandra is the most powerful facility for X-ray astrophysics, and its unique capabilities have no likely successor in the foreseeable future."


"The prospects for further compelling science return in the future are excellent. This panel enthusiastically endorses the extension of the Chandra mission."

"Chandra discoveries continue to have an extraordinarily high impact on both the scientific and public understanding of our universe."

"The vast breadth of Chandra science reaches almost every area of astrophysics, including star and galaxy formation, the creation of the elements, the origin and evolution of black holes and galaxies and placing stellar activity in a cosmic context."

"The large number of Chandra proposals (636 in Cycle 16 in March 2014) indicates a very high demand for observing time, archival research and theoretical studies. Many proposals investigate new ideas that were not even imagined before launch. Many exciting results published in refereed journals are released to the public as press releases (~30 per year) with excellent illustrations that have high visibility in the media."

"The Panel recognizes the clear importance of communicating Chandra’s scientific results beyond the scientific community. The CXC staff members are to be commended for the extraordinary innovative methods and techniques they have employed in publicizing Chandra science and engaging the broader public."
These positive comments are gratifying for everyone associated with the Chandra mission, especially the many people who worked very hard on the Senior Review proposal, including several members of our EPO group.

The panel also listed six findings “that may be useful to enhance future returns from the observatory”, as listed in the Executive Summary and section seven of the report.

I'll note that a great deal of research performed with Chandra involves combining results with other observatories, both in space and on the ground. Therefore, I’d like to congratulate our Great Observatory cousins at Space Telescope Science Institute for the very positive report from Senior Review on HST, and our colleagues at other endorsed missions.

For more information about Senior Review, the Call for Proposals and the response by NASA to the Senior Review report are both publicly available.

-Peter Edmonds, CXC
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Chandra and the Camelopardalids

Chandra and the Camelopardalids:

Update (05.28.14): According to the team at the OCC, Chandra was unharmed during this new meteor shower. They report that passage through the stream was 'thankfully unremarkable.' According to all of their information, there was no evidence for any type of impact and it was 'smooth sailing.'

This week, sky watchers will be treated to a special event: a new meteor shower. Meteor showers occur when Earth, on its orbit around the Sun, passes through the debris left behind by a comet. There are some debris fields that Earth passes through every year and produce regular meteor showers that many people have heard of. These include the Leonids in November and the Perseids in July and August.

The meteor shower that will occur on May 23rd and 24th will be caused by the wake of Comet 209P/Linear and has been dubbed the Camelopardalids. (Meteor showers are named after the constellation that they appear to be coming from, which in this case is Cameloparadis, the giraffe.) Comet 209P/Linear was discovered in 2004, and it travels in an orbit that only crosses with Earth's once every five years as it loops around the Sun. This means that Earth only rarely crosses paths with the trail of material left behind it. Comet experts, however, calculate that this week Earth is due for an encounter with a clump of 209P/Linear's wake, perhaps for the first time ever.

Some researchers have predicted this will be a very active meteor shower that could produce up to 200 meteors an hour. While this could be an exciting early morning show for sky watchers who can get outside, a team at the Chandra X-ray Center's Operation Control Center (OCC) will be busy preparing for and dealing with the event inside.

Chandra

Even though much of the debris in meteor showers is very tiny, it can pose serious potential risks for spacecraft like Chandra. There are two main concerns: the first is that particles moving at very high speeds will generate electric fields that could disrupt the electronics aboard the spacecraft. The second big worry is that a particle would impact Chandra, causing damage to a key instrument or other important piece of the telescope.

While the team at the OCC has handled many meteor showers in Chandra's nearly 15 years of operations, the Camelopardalids are different because there is relatively little known about the stream of material that Earth (and Chandra) will pass through. Because of this uncertainty, the Mission Planning Team is taking extra precautions.

In fact, it's the Mission Planners to think of everything that could possibly go wrong – and then have plans in place to prevent those things from happening. This includes having contingencies in place in case something unusual happens in the two days before the meteor shower even starts, just to make sure they can safeguard Chandra.

Several hours before the meteor shower is expected to begin, the team will make sure that the spacecraft is pointed in the opposite direction of where the meteors are coming from (that is known as the "radiant" of the meteor shower.) They will also feather, or turn, Chandra's solar arrays in a direction to minimize the amount of their surface area that will be exposed to the oncoming meteors.

Chandra

In 2011, the team at the OCC shifted its approach to meteor showers during the Draconids. They realized that only the very high-speed particles posed a threat to the electronics onboard. Rather than "safing" all of the instruments, they calculated they could continue have the telescope perform science observations as long as it was pointed away from the radiant.

The Camelopardalids are expected to have even slower moving particles than the Draconids, so the plan would have been to continue observations of the sky. Like most space-based telescopes, observing time on Chandra is very valuable so the team at the OCC is always looking to maximize it. Unfortunately, the peak of the meteor shower will begin when Chandra is traveling through the Earth’s radiation belts, as it does during one of its orbits that take it a third of the way to the Moon.

To protect the spacecraft during these regular trips through the potentially damaging radiation, Chandra does not perform science observations of the sky. Instead, the team uses this "down time" to conduct calibration observations of the instruments that can be done safely within the spacecraft. (Calibration observations are used to assess the state and performance of the instruments on board.)

Even though Chandra will exit the radiation belts several hours before the meteor shower is over and could theoretically begin science observations, the team decided against it. That's because the solar arrays would have to be moved, and the risk outweighed the potential reward of that observing time. The result is that one of Chandra’s instruments – known as the Advanced CCD Imaging Spectrometer, or ACIS -- will get a much longer calibration observation than usual. (That extra calibration time will be put to good use as scientists never complain about having too much data for anything.)

These are just some of the many details and plans that are being put into place by staff at the OCC to protect Chandra during this meteor shower. Comet forecasters think the peak of the Camelopardalids will be between 2:00 and 4:00am Eastern time. If there are clear skies in your area, try to get outside to take a look if you are awake. If you do, remember that there are many people hard at work trying to ensure the safety of our greatest telescopes in space.

-Megan Watzke, CXC
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Chandra Helps Explain "Red and Dead Galaxies"

Chandra Helps Explain "Red and Dead Galaxies":

Cold Gas

NASA's Chandra X-ray Observatory has shed new light on the mystery of why giant elliptical galaxies have few, if any, young stars. This new evidence highlights the important role that supermassive black holes play in the evolution of their host galaxies.

Because star-forming activity in many giant elliptical galaxies has shut down to very low levels, these galaxies mostly house long-lived stars with low masses and red optical colors. Astronomers have therefore called these galaxies "red and dead".

Previously it was thought that these red and dead galaxies do not contain large amounts of cold gas - the fuel for star formation - helping to explain the lack of young stars. However, astronomers have used ESA's Herschel Space Observatory to find surprisingly large amounts of cold gas in some giant elliptical galaxies. In a sample of eight galaxies, six contain large reservoirs of cold gas. This is the first time that astronomers have seen large quantities of cold gas in giant elliptical galaxies that are not located at the center of a massive galaxy cluster.

With lots of cold gas, astronomers would expect many stars to be forming in these galaxies, contrary to what is observed. To try to understand this inconsistency, astronomers studied the galaxies at other wavelengths, including X-rays and radio waves. The Chandra observations map the temperature and density of hot gas in these galaxies. For the six galaxies containing abundant cold gas, including NGC 4636 and NGC 5044 shown here, the X-ray data provide evidence that the hot gas is cooling, providing a source for the cold gas observed with Herschel. However, the cooling process stops before the cold gas condenses to form stars. What prevents the stars from forming?

A strong clue comes from the Chandra images. The hot gas in the center of the six galaxies containing cold gas appears to be much more disturbed than in the cold gas-free systems. This is a sign that material has been ejected from regions close to the central black hole. These outbursts are possibly driven, in part, by clumpy, cold gas that has been pulled onto the black hole. The outbursts dump most of their energy into the center of the galaxy, where the cold gas is located, preventing the cold gas from cooling sufficiently to form stars.

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

-Megan Watzke, CXC
Posted by Nelio Inacio at 3:57 PM 0 comments

Chandra Captures Galaxy Sparkling in X-rays

Chandra Captures Galaxy Sparkling in X-rays:

M51

Nearly a million seconds of observing time with NASA's Chandra X-ray Observatory has revealed a spiral galaxy similar to the Milky Way glittering with hundreds of X-ray points of light.

The galaxy is officially named Messier 51 (M51) or NGC 5194, but often goes by its nickname of the "Whirlpool Galaxy." Like the Milky Way, the Whirlpool is a spiral galaxy with spectacular arms of stars and dust. M51 is located about 30 million light years from Earth, and its face-on orientation to Earth gives us a perspective that we can never get of our own spiral galactic home.

By using Chandra, astronomers can peer into the Whirlpool to uncover things that can only be detected in X-rays. In this new composite image, Chandra data are shown in purple. Optical data from the Hubble Space Telescope are red, green, and blue.

Most of the X-ray sources are X-ray binaries (XRBs). These systems consist of pairs of objects where a compact star, either a neutron star or, more rarely, a black hole, is capturing material from an orbiting companion star. The infalling material is accelerated by the intense gravitational field of the compact star and heated to millions of degrees, producing a luminous X-ray source. The Chandra observations reveal that at least ten of the XRBs in M51 are bright enough to contain black holes. In eight of these systems the black holes are likely capturing material from companion stars that are much more massive than the Sun.

Because astronomers have been observing M51 for about a decade with Chandra, they have critical information about how X-ray sources containing black holes behave over time. The black holes with massive stellar companions are consistently bright over the ten years of Chandra observations. These results suggest that the high-mass stars in these X-ray sources also have strong winds that allow for a steady stream of material to flow onto the black hole.

More at http://chandra.harvard.edu/photo/2014/m51/

-Megan Watzke, CXC
Posted by Nelio Inacio at 3:57 PM 0 comments

Visualizing the X-ray Universe: Stories About Science

Visualizing the X-ray Universe: Stories About Science:

Telling a story about science can come in many different shapes, from an image of the area around a black hole, to a three-dimensional model of the remains of an exploded star, to something as simple as a tweet about a planet. Working for the Chandra X-ray Observatory, one of NASA's “Great Observatories” that studies extremely hot regions in space such as colliding galaxies and neutron stars, there is no shortage of data to tell stories about. Chandra orbits about 1/3 of the way to the Moon so it can take long exposures of cosmic objects. This year, Chandra marks its 15th anniversary of science operations out in the cold, dark and somewhat dangerous void of space.

Perhaps 50% of the job of “visualizing the X-ray Universe” is figuring out how we need to look at Chandra’s X-ray data and asking ourselves: what questions are this data trying to answer? what do experts see in this data? how will non-experts view and understand the data? The remaining 50% of the job is then what to do with that data, to make it both accessible and understandable.

Chandra

Data Challenges

When looking at the Universe in X-ray light, it’s all about making the invisible into something visible. Human eyes evolved to see and make sense of so-called visible light, but visible, or optical light, makes up a small percentage of all the available light in the Universe. The other task, when looking at the Universe in a different type of light such as X-rays, is to help make the concepts of high-energy astrophysics relatable for readers with all kinds of different knowledge bases.

Astronomy is fortunately blessed with a wealth of data to work with. Professional astronomers have many different kinds of observatories and telescopes to utilize. These telescopes look at many different kinds of light or different kinds of objects. There are also many astrophotographers and amateur astronomers working on the ground. So we have terabytes upon terabytes of information to sort and analyze. Of course, the Universe is unimaginably big, so we need all of that data to try and figure things out.

One of the biggest challenges in telling these stories then is how to make meaning out of so much data. And we need to figure out how to communicate that meaning in a transparent way.

The type of images we create or work with are not created with the click of a camera like a great big selfie of the sky. It’s the result of a process of translation. A CCD in the telescope records the photons (or packets of energy), and the 1s and 0s are sent down to Earth. From there, they’re processed into an events table, and then translated into a visual representation of the object (see events table and image of Cassiopeia A, below). The next step is to turn the image from black and white into color.

There are many human steps in there, and we each have bias. We are making many choices, decisions, along the way. Our aim in all of this is to increase the information quotient of the image, by adding color for example to pull out scientific details we could not otherwise make out visually. But we are still making a series of choices.

CasA

Adding Context

It takes a lot of time to collect those high-energy photons that Chandra detects – more time than it does for the Hubble Space Telescope to make an image, for example – because there are fewer of them being emitted from most of the Universe. Sometimes the visual representations of the X-ray data are more abstract or esoteric looking. The results are perhaps not as recognizable an object to us. We are more familiar with, say, a visible light view of a planet or galaxy. For many, a more exotic-looking nebulous structure doesn’t necessarily communicate that this is an image of space.

How do we anchor the necessary information in a context that makes sense for our audiences? One thing we can do is to add data from a different wavelength, such as optical or infrared, that does have a more recognizable shape. This adds an extra layer of information.

We may start off showing the remains of an exploded star that, if seen alone, might resemble something from a microbiology class. But then you include the optical star field of that same area of the sky to the X-ray data and our brains can more immediately understand, this is a celestial object. One important corollary to this is that we always make sure we are transparent as possible with whatever we do to create the image. On the Chandra web site for example we have a “build a bear” like function, a simple script that lets the visitor see and click through the individual layers of data that were collated into the resulting image.

Tycho's SNR

But again, the parameters around what to include or exclude are always based on: what is the science? what is the story? what might people see, ask or question when they see the result?

Experts vs Non-Experts

To further help us understanding our audiences, and study how best to tell a science story through images and text, we have been running a research program called "Aesthetics & Astronomy" that studies the perception of astronomical images and their captions across the novice-expert spectrum of users.

We’ve learned that, starting with visual processing, what an expert sees when looking at an astronomical image is not necessarily what the novice sees. The expert tends to move from the astronomy first to aesthetics last – e.g. first he or she is commenting on what kind of data are in the image, what is meant to be shown, then the expert moves on to statements such as “this is pretty cool” or “that’s a lovely image of a galaxy”. In our studies, we’ve seen that the non-expert often moves from aesthetics to astronomy. For example, he or she might start with, “wow, that’s beautiful” and “intense and colorful” before eventually questioning “what does it mean?” “what does a scientist see when he or she looks at this?”

So, novices might begin with a sense of awe and wonder, and focus first on the aesthetic qualities of the astronomical image being shown. Experts, however, often will first inquire how the image was produced, what information is being presented in the image, and what the creators of the image wanted to convey.

Another area where the experts and non-experts differ is in color. Not many non-experts consider blue to be hot. But scientists often do. Because of this, experts tend to visualize blue as hot and red as cool in the making of an image. In contrast, about 80% of novices see red as hot compared to 60% of experts. We’ve never heard a parent say to his or her child “Don’t touch that, it’s blue hot”. So when you have an astronomical image that shows hot material around a galaxy, do you color that hotter area blue or red? The primarily red image might actually convey the information of the object better even though its color mapping would be considered non-standard for a scientist (for example, see below for blue and red versions of galaxy NGC 4696).

NGC 4696

To sum up, astronomy images are not like a snapshot from an iPhone. Everything we see in these images is real, but the data have to be translated into the image through a series of steps. How a telescope "sees" is very different than how our human eyes work. Modern telescopes give us super-human vision that enable us to explore the Universe in ways unimaginable just a few decades ago. In most cases they literally make the invisible visible and help us tell better stories about the science.

Note: This blog originally appeared at Innovation Insights on May 29, 2014

-Kim Arcand

Visualization Lead, Chandra
Posted by Nelio Inacio at 3:56 PM 0 comments
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