Archive for June, 2013
THE HUMAN BODY IN SPACE: 6 WEIRD FACTS
Get to know how your body could react to life in orbit with these 6 fun facts:
FIRST STOP: Astronauts Get Taller
The astronauts return to their preflight height after a few months of being back within the planet’s gravity.
NEXT: Puffy Faces and Skinny Legs
Credit: NASA TV
For the first few weeks of spaceflight, most astronauts appear to have a puffy head and skinny legs. The fluid in their bodies redistributes evenly when gravity isn’t playing a role in their biological systems. After a little time in orbit, however, the body adapts to the new distribution of fluids, and the astronauts don’t appear as puffy.
NEXT: Coordination Trouble on Earth
Sometimes, spaceflyers will drop things, forgetting that gravity is influential back on Earth. After six months in microgravity conditions, it is difficult to adjust to life in a place where materials fall if you drop them.
NEXT: Muscle Meltdown
Although this might be ideal in space, it’s problematic once back on Earth. Astronauts have to exercise for two hours a day on the space station just to maintain a healthy amount of muscle mass that they will need once they are back on the planet.
NEXT: My Aching Bones!
Credit: NASA TV.
There are two treadmills and two stationary bicycles on board the space station to help the residents keep in shape during their time in orbit.
NEXT: Tossing and Turning in Space
Credit: “Inside my Sleep Pod – it serves as my bedroom, recording studio, and twitter zone while on the Space Station. pic.twitter.com/Mw7FeHVB”
The flashes are actually from cosmic rays — high-energy particles that beam through the solar system — shooting through the orbiting outpost. Spaceflyers have described the flashes as “fireworks” or “streaks.” Although the radiation from the cosmic rays can build up over time, the particles don’t pose too much of a risk during the limited time that astronauts spend on the station.
Space Station Evolution: 6 Amazing Orbital Outposts
Diagram of the Soviet Salyut 1 space station (left), with a Soyuz spacecraft ready to dock.
A drawing of the Soviet space station Salyut 7 (right) and the Cosmos 1686 spacecraft.
Skylab astronauts took this photograph as they approached the orbiting laboratory on the the third and final mission in November 1973.
NEXT: Mir, Russia’s Long-Lived Outpost
The Mir Space Station and Earth limb observed from the Orbiter Endeavour during NASA’s STS-89 mission in 1998.
NEXT: Tiangong 1, China’s 1st Space Lab
Video still showing China’s Shenzhou 8 spacecraft docked with the Tiangong 1 lab module on Nov. 3, 2011.
Credit: China Central Television
This image from a NASA space shuttle mission shows the International Space Station in orbit. The space station is the size of a football field and home to six astronauts. Image taken: Feb. 10, 2010.
Built in sections, the station began in 1998 with the launch of Russia’s Zarya’s module. Today it spans the area of an American football field, possessing numerous pressurized and unpressurized modules.Humans have continuously occupied the International Space Station since Nov. 2, 2000. In that time, 204 individuals have visited it. As of July 2012, 125 vehicles have launched to the space station since the launch of the first module: 81 Russian vehicles, 37 space shuttle missions, the U.S. SpaceX Dragon commercial vehicle (several missions), three European and three Japanese vehicles. The first crews consisted of three-person teams, dropping to two after the Columbia shuttle disaster, but as of 2009, six people can stay aboard the station at one time. Two Russian Soyuz modules remain docked to the station for crew departures.
The ISS receives commands from mission control centers in Houston or Moscow. The station has funding to operate through 2020, though it may remain capable of usefulness through 2028. [Video Show: See Inside the International Space Station
Photos: Portraits of Shuttle Endeavour at Space Station
Five Years of Stereo Imaging for NASA’s TWINS
Since 2008, NASA’s two TWINS spacecraft have been providing a sterescopic view of the ring current — a hula hoop of charged particles that encircles Earth. Credit: J. Goldstein/SWRI
Surrounding Earth is a dynamic region called the magnetosphere. The region is governed by magnetic and electric forces, incoming energy and material from the sun, and a vast zoo of waves and processes unlike what is normally experienced in Earth-bound physics. Nestled inside this constantly changing magnetic bubble lies a donut of charged particles generally aligned with Earth’s equator. Known as the ring current, its waxing and waning is a crucial part of the space weather surrounding our planet, able to induce magnetic fluctuations on the ground as well as to transmit disruptive surface charges onto spacecraft.
On June 15, 2008, a new set of instruments began stereoscopic imaging of this mysterious region. Called Two Wide-angle Imaging Neutral-atom Spectrometers or TWINS, these satellites orbit in widely separated planes to provide the first and only stereo view of the ring current. TWINS maps the energetic neutral atoms that shoot away from the ring current when created by ion collisions.
In five years of operation, the TWINS maps have provided three-dimensional images and global characterization of this region. The observatories track how the magnetosphere responds to space weather storms, characterize global information such as temperature and shape of various structures within the magnetosphere, and improve models of the magnetosphere that can be used to simulate a vast array of events.
“With two satellites, with two sets of simultaneous images we can see things that are entirely new,” said Mei-Ching Fok, the project scientist for TWINS at NASA’s Goddard Space Flight Center in Greenbelt, Md. “This is the first ever stereoscopic energetic neutral atom mission, and it’s changed the way we understand the ring current.”
Each spacecraft is in a highly elliptical orbit called a Molniya orbit, during which the spacecraft spend most of their time around 20,000 miles above Earth, where they get a great view of the magnetosphere. Initially launched for a two-year mission, TWINS was formally extended in 2010 for three more years, with another multi-year extension pending. Over that time, TWINS has worked hand in hand with other NASA missions that provide information about Earth’s magnetosphere.
“We’ve done some fantastic new research in the last five years,” said David McComas, the principal investigator for TWINS at the Southwest Research Institute in San Antonio, Texas. “As a mission of opportunity, it is a very inexpensive mission and it continues to return incredible science.”
TWINS science is based on two instruments that can track neutral atoms. The first is a neutral atom imager that records the atoms that naturally stream away when a neutral atom collides with an ion. This allows the instrument to map the original ions from far away – as if it could see atoms the way we see light – instead of only collecting data from the areas of space it passes through.
“Over the course of the last 20 years a completely new technique evolved so we can observe charged particles, such as those in the ring current, remotely,” said McComas. “The charged particles sometimes collide with a slow-moving neutral particle, in this case from a population of neutrals from Earth’s highly extended atmosphere, the geocorona.”
When this happens, an electron hops from the slow neutral atom to the fast ion, so now the former becomes charged, and the latter neutral. That new neutral speeds off in a straight direction, unfazed by the magnetic field lines around Earth that guide and control the motion of charged particles. TWINS collects such fast neutral particles and from that data scientists can work backward to map out the location and movement of the original ions.
The other instrument on TWINS is a Lyman alpha detector, which can measure the density of hydrogen from afar, and in this case observes the hydrogen cloud around Earth, the geocorona.
Most importantly, these instruments exist on both of the TWINS spacecraft. Much of the successful research in the last five years relies on the ability to watch these neutrals from two viewpoints, allowing scientists to analyze not only speed and number of particles, but also to determine the angles at which the particles left their original collisions. The stereo vision contributed to the detailed perspectives on how the magnetosphere reacts to space weather storms: both those due to the impact of a coronal mass ejection that traveled from the sun toward Earth and due to an incoming twist in the solar wind known as a co-rotating interaction region. TWINS has also revealed that the pitch angle at which the ions travel around Earth is different on each side of the planet. Such information helps scientists determine whether the ions are more likely to escape from the ring current out into space or to ultimately funnel down toward Earth.
“TWINS is a stereo mission, providing the first observations of the neutral atoms from two vantage points, but two spacecraft give us another advantage,” said Natalia Buzulukova, a magnetospheric scientist at Goddard who works with TWINS data. “Two spacecraft provide continuous coverage of the ring current, as one set of instruments always has a view.”
Because the spacecraft orbits are not in sync they provide stereoscopic imaging for a few hours each day, but there is always at least one spacecraft keeping tabs on how events are unfolding. Prior to TWINS, a spacecraft might see a tantalizing process taking place in the ring current for only a short while before its orbit took it out of view. The event might well have finished before the spacecraft came back around for its second look.
Such continuity has proved useful to determine what governs whether particles in the ring current will precipitate downward toward Earth as well as to provide a global temperature map of the magnetic tail trailing behind Earth, the magnetotail. Such a map had only ever previously been inferred from models and statistical analysis, never from a comprehensive data set of what was actually observed.
The Lyman-alpha instrument has been used in two ways. For one thing, it quantifies the geocorona in order to better understand how it affects the collisions in the ring current. It also has taught us more about the geocorona itself. Previously, researchers believed it to be a fairly simple sphere around Earth. The two TWINS instruments have shown how asymmetric it is, changing with the solar cycle, seasons, and even the hours of the day.
A final important feature of this fire hose of TWINS data is how much it helps improve computer simulations of the ring current and the rest of the magnetosphere. With accurate computer models, scientists can better predict how the magnetosphere will react to any given space weather event.
“We get two really unique things with two spacecraft: stereo imaging and continuous coverage. Together the observations we get are fantastic,” said McComas. “It’s an incredibly powerful combination of tools.”
TWINS is an Explorer Mission of Opportunity. Southwest Research Institute leads TWINS with teams of national and international partners. Goddard manages the Explorers Program for NASA’s Science Mission Directorate in Washington, D.C.
For more information about TWINS science and mission, visit:
Karen C. Fox
NASA’s Goddard Space Flight Center, Greenbelt, Md.
IRIS (Interface Region Imaging Spectrograph )to Take Precise Look at Sun’s Energy
By Steven Siceloff,
NASA’s Kennedy Space Center
NASA’s IRIS spacecraft will use an ultraviolet telescope to look at a small area of the sun to answer detailed questions about the way the sun’
Researchers hope NASA’s latest solar observatory will answer a fundamental question of how the sun creates such intense energy.
Scheduled to launch June 26, the IRIS spacecraft will point a telescope at the interface region of the sun that lies between the surface and the million degree outer atmosphere called the corona. It will improve our understanding of how energy moves from the sun’s surface to the glowing corona, heating up from 6,000 degrees to millions of degrees.
The IRIS mission, short for Interface Region Imaging Spectrograph, calls for the 7-foot-long spacecraft to point its ultraviolet telescope at the sun to discern features as small as 150 miles across. It will look at about 1 percent of the sun’s surface.
“IRIS will show the solar chromosphere in more detail than has ever been observed before,” said Adrian Daw, deputy project scientist. “My opinion is that we are bound to see something we didn’t expect to see.”
IRIS is a NASA Small Explorer that will complement the Solar Dynamics Observatory and Hinode missions to explore how the solar atmosphere works and impacts Earth. SDO and Hinode will monitor the solar surface and outer atmosphere, with IRIS watching the region in between.
“IRIS almost acts as a microscope to SDO’s telescope,” said Jim Hall, mission manager for IRIS. “It’s going to look in closely and it’s going to look at that specific region to see how the changes in matter and energy occur in this region. It’s going to collectively bring us a more complete view of the sun.” IRIS improves our understanding of the interface region where most of the sun’s ultraviolet emission is generated that impacts the near Earth space environment and Earth’s climate. Solar activity such as coronal mass ejections and solar flares, also are of great interest to spacecraft designers who have to figure out ways to protect instruments and electronics from them.
“We’re always looking for the answers to why and everything starts at the root with the sun,” Hall said.
At the end of June 2013, NASA will launch its newest set of instruments to watch the sun: the Interface Region Imaging Spectrograph, or IRIS.
IRIS will ride into Earth orbit on an Orbital Sciences Pegasus XL rocket. The Pegasus is famous as the only winged launcher in NASA’s inventory. Though small compared to the gigantic boosters that send heavy satellites into orbit and probes to distant worlds, the Pegasus’ size and flexibility has allowed numerous missions to be launched that would have been too small for larger rockets.
“Pegasus has been a tremendously successful launch vehicle for NASA,” said Tim Dunn, launch director for IRIS. “We have launched 18 successful missions on Pegasus. The team is very dynamic, very flexible. They’re able to accomplish a tremendous amount in a very short time.”
The Pegasus and its IRIS payload will be carried to about 39,000 feet under a modified L-1011 airliner taking off from Vandenberg Air Force Base in California. Over the Pacific Ocean off the California coast, the plane will drop the Pegasus to begin the launch.
The Pegasus will ignite its solid-fueled first stage five seconds into its fall and arch skyward with the main wing giving it lift and the three fins in the back steering it through the thick layers of Earth’s lower atmosphere.
The rocket will burn its load of fuel in 73 seconds and fall away. The second stage, which has no wings, will ignite 94 seconds into flight and push IRIS higher and faster into space. The third stage will take over after that, delivering IRIS into its orbit about 10 minutes after launch.
This is the last one scheduled for the Pegasus rocket because there are not any small spacecraft missions that fit the Pegasus niche.
The launch is taking place from the West Coast because IRIS will go into a roughly polar orbit, meaning it will cross over the north and south pole regions of Earth on each pass around the planet.
Understanding how energy travels through the lowest layers of the sun’s atmosphere is the goal of NASA’s Interface Region Imaging Spectrograph .
“Eight months out of the year, we are freely viewing the sun in that orbit,” Hall said.
Once IRIS is in space with its solar panels unfolded to provide electricity and the telescope flipped open, scientists expect to see intriguing data pretty quickly.
“I think the biggest surprise will come once the mission is launched and it starts to observe the sun,” Daw said. “We know to some extent what we hope to learn, what specific science questions we are going to answer, but there’s always that element of surprise.”
Chandra Latest News, Features and Photos
Data from NASA’s Chandra X-ray Observatory have been used to discover 26 black hole candidates in the Milky Way’s galactic neighbor, Andromeda, as described in our latest press release. This is the largest number of possible black holes found in a galaxy outside of our own.
A team of researchers, led by Robin Barnard of the Harvard-Smithsonian Center for Astrophysics, used 152 observations of Chandra spanning over 13 years to find the 26 new black hole candidates. Nine were known from earlier work. These black holes belong to the stellar-mass black hole category, which means they were created when a massive star collapsed and are about 5 to 10 times the mass of the Sun.
This wide-field view of Andromeda contains optical data from the Burrell Schmidt telescope of the Warner and Swansey Observatory on Kitt Peak in Arizona. Additional detail of the core and dust in the spiral arms comes from an image taken by astrophotographer Vicent Peris using data from two of his personal telescopes. In this combined optical image, red, green, and blue show different bands from the visible light portion of the electromagnetic spectrum.
The inset contains X-ray data from multiple Chandra observations of the central region of Andromeda. A larger view can be seen in the Chandra image at this link.
Seven of the 35 black hole candidates are within only 1,000 light years of the Andromeda Galaxy’s center. This is more than the number of black hole candidates with similar properties located near the center of our own Galaxy. This, however, does not take astronomers by surprise, since the bulge of stars in the middle of Andromeda is bigger, allowing more black holes to form.
Eight of the nine black hole candidates that were previously identified are associated with globular clusters, the ancient concentrations of stars distributed in a spherical pattern about the center of the galaxy. This also differentiates Andromeda from the Milky Way as astronomers have yet to find a similar black hole in one of the Milky Way’s globular clusters.
Andromeda, also known as Messier 31 (M31), is a spiral galaxy located about 2.5 million light years away. It is thought that the Milky Way and Andromeda will collide several billion years from now. The black holes located in both galaxies will then reside in the large, elliptical galaxy that results from this merger.
These results are available online and will be published in the June 20th issue of The Astrophysical Journal. Many of the Andromeda observations were made within Chandra’s Guaranteed Time Observer program.
Credits: X-ray: NASA/CXC/SAO/R. Barnard, Z. Lee et al.; Optical: NOAO/AURA/NSF/REU Program/B. Schoening, V. Harvey and Descubre Foundation/CAHA/OAUV/DSA/V. Peris
This graphic shows an exotic object in our galaxy called SGR 0418+5729 (SGR 0418 for short). As described in our press release, SGR 0418 is a magnetar, a type of neutron star that has a relatively slow spin rate and generates occasional large blasts of X-rays.
The only plausible source for the energy emitted in these outbursts is the magnetic energy stored in the star. Most magnetars have extremely high magnetic fields on their surface that are ten to a thousand times stronger than for the average neutron star. New data shows that SGR 0418 doesn’t fit that pattern. It has a surface magnetic field similar to that of mainstream neutron stars.
In the image on the left, data from NASA’s Chandra X-ray Observatory shows SGR 0418 as a pink source in the middle. Optical data from the William Herschel telescope in La Palma and infrared data from NASA’s Spitzer Space Telescope are shown in red, green and blue.
On the right is an artist’s impression showing a close-up view of SGR 0418. This illustration highlights the weak surface magnetic field of the magnetar, and the relatively strong, wound-up magnetic field lurking in the hotter interior of the star. The X-ray emission seen with Chandra comes from a small hot spot, not shown in the illustration. At the end of the outburst this spot has a radius of only about 160 meters, compared with a radius for the whole star of about 12 km.
The researchers monitored SGR 0418 for over three years using Chandra, ESA’s XMM-Newton as well as NASA’s Swift and RXTE satellites. They were able to make an accurate estimate of the strength of the external magnetic field by measuring how its rotation speed changes during an X-ray outburst. These outbursts are likely caused by fractures in the crust of the neutron star precipitated by the buildup of stress in the stronger magnetic field lying below the surface.
By modeling the evolution of the cooling of the neutron star and its crust, as well as the gradual decay of its magnetic field, the researchers estimated that SGR 0418 is about 550,000 years old. This makes SGR 0418 older than most other magnetars, and this extended lifetime has probably allowed the surface magnetic field strength to decline over time. Because the crust weakened and the interior magnetic field is relatively strong, outbursts could still occur.
The implications of this result for understanding supernova explosions and the number and evolution of magnetars is discussed in the press release.
SGR 0418 is located in the Milky Way galaxy at a distance of about 6,500 light years from Earth. These new results on SGR 0418 appear online and will be published in the June 10, 2013 issue of The Astrophysical Journal. NASA’s Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA’s Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra’s science and flight operations from Cambridge, Mass.
Credits: X-ray: NASA/CXC/CSIC-IEEC/N.Rea et al; Optical: Isaac Newton Group of Telescopes, La Palma/WHT; Infrared: NASA/JPL-Caltech
This composite image of a galaxy illustrates how the intense gravity of a supermassive black hole can be tapped to generate immense power. The image contains X-ray data from NASA’s Chandra X-ray Observatory (blue), optical light obtained with the Hubble Space Telescope (gold) and radio waves from the NSF’s Very Large Array (pink).
This multi-wavelength view shows 4C+29.30, a galaxy located some 850 million light years from Earth. The radio emission comes from two jets of particles that are speeding at millions of miles per hour away from a supermassive black hole at the center of the galaxy. The estimated mass of the black hole is about 100 million times the mass of our Sun. The ends of the jets show larger areas of radio emission located outside the galaxy.
The X-ray data show a different aspect of this galaxy, tracing the location of hot gas. The bright X-rays in the center of the image mark a pool of million-degree gas around the black hole. Some of this material may eventually be consumed by the black hole, and the magnetized, whirlpool of gas near the black hole could in turn, trigger more output to the radio jet.
Most of the low-energy X-rays from the vicinity of the black hole are absorbed by dust and gas, probably in the shape of a giant doughnut around the black hole. This doughnut, or torus blocks all the optical light produced near the black hole, so astronomers refer to this type of source as a hidden or buried black hole. The optical light seen in the image is from the stars in the galaxy.
The bright spots in X-ray and radio emission on the outer edges of the galaxy, near the ends of the jets, are caused by extremely high energy electrons following curved paths around magnetic field lines. They show where a jet generated by the black hole has plowed into clumps of material in the galaxy (mouse over the image for the location of these bright spots). Much of the energy of the jet goes into heating the gas in these clumps, and some of it goes into dragging cool gas along the direction of the jet. Both the heating and the dragging can limit the fuel supply for the supermassive black hole, leading to temporary starvation and stopping its growth. This feedback process is thought to cause the observed correlation between the mass of the supermassive black hole and the combined mass of the stars in the central region or bulge or a galaxy.
These results were reported in two different papers. The first, which concentrated on the effects of the jets on the galaxy, is available online and was published in the May 10, 2012 issue of The Astrophysical Journal. It is led by Aneta Siemiginowska from the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, MA and the co-authors are Łukasz Stawarz, from the Institute of Space and Astronautical Science in Yoshinodai, Japan; Teddy Cheung from the National Academy of Sciences in Washington, DC; Thomas Aldcroft from CfA; Jill Bechtold from University of Arizona in Tucson, AZ; Douglas Burke from CfA; Daniel Evans from CfA; Joanna Holt from Leiden University in Leiden, The Netherlands; Marek Jamrozy from Jagiellonian University in Krakow, Poland; and Giulia Migliori from CfA. The second, which concentrated on the supermassive black hole, is available online and was published in the October 20, 2012 issue of The Astrophysical Journal. It is led by Malgorzata Sobolewska from CfA, and the co-authors are Aneta Siemiginowska, Giulia Migliori, Łukasz Stawarz, Marek Jamrozy, Daniel Evans, and Teddy Cheung.
NASA’s Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA’s Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra’s science and flight operations from Cambridge, Mass.
Credits: X-ray: NASA/CXC/SAO/A. Siemiginowska et al; Optical: NASA/STScI; Radio: NSF/NRAO/VLA
Scientists have used Chandra to make a detailed study of an enormous cloud of hot gas enveloping two large, colliding galaxies. This unusually large reservoir of gas contains as much mass as 10 billion Suns, spans about 300,000 light years, and radiates at a temperature of more than 7 million degrees.
This giant gas cloud, which scientists call a “halo,” is located in the system called NGC 6240. Astronomers have long known that NGC 6240 is the site of the merger of two large spiral galaxies similar in size to our own Milky Way. Each galaxy contains a supermassive black hole at its center. The black holes are spiraling toward one another, and may eventually merge to form a larger black hole.
Another consequence of the collision between the galaxies is that the gas contained in each individual galaxy has been violently stirred up. This caused a baby boom of new stars that has lasted for at least 200 million years. During this burst of stellar birth, some of the most massive stars raced through their evolution and exploded relatively quickly as supernovas.
The scientists involved with this study argue that this rush of supernova explosions dispersed relatively high amounts of important elements such as oxygen, neon, magnesium, and silicon into the hot gas of the newly combined galaxies. According to the researchers, the data suggest that this enriched gas has slowly expanded into and mixed with cooler gas that was already there.
During the extended baby boom, shorter bursts of star formation have occurred. For example, the most recent burst of star formation lasted for about five million years and occurred about 20 million years ago in Earth’s timeframe. However, the authors do not think that the hot gas was produced just by this shorter burst.
What does the future hold for observations of NGC 6240? Most likely the two spiral galaxies will form one young elliptical galaxy over the course of millions of years. It is unclear, however, how much of the hot gas can be retained by this newly formed galaxy, rather than lost to surrounding space. Regardless, the collision offers the opportunity to witness a relatively nearby version of an event that was common in the early Universe when galaxies were much closer together and merged more often.
In this new composite image of NGC 6240, the X-rays from Chandra that reveal the hot gas cloud are colored purple. These data have been combined with optical data from the Hubble Space Telescope, which shows long tidal tails from the merging galaxies, extending to the right and bottom of the image.
A paper describing these new results on NGC 6240 is available online and appeared in the March 10, 2013 issue of The Astrophysical Journal. The authors in this study were Emanuele Nardini (Harvard-Smithsonian Center for Astrophysics, or CfA, Cambridge, MA and currently at Keele University, UK), Junfeng Wang (CfA and currently at Northwestern University, Evanston, IL), Pepi Fabbiano (CfA), Martin Elvis (CfA), Silvia Pellegrini (University of Bologna, Italy), Guido Risalti (INAF-Osservatorio Astrofisico di Arcetri, Italy and CfA), Margarita Karovska (CfA), and Andreas Zezas (University of Crete, Greece and CfA).
NASA’s Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA’s Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra’s science and flight operations from Cambridge, Mass.
Credits: X-ray: NASA/CXC/SAO/E. Nardini et al; Optical: NASA/STScI
This year, astronomers around the world have been celebrating the 50th anniversary of X-ray astronomy. Few objects better illustrate the progress of the field in the past half-century than the supernova remnant known as SN 1006.
When the object we now call SN 1006 first appeared on May 1, 1006 A.D., it was far brighter than Venus and visible during the daytime for weeks. Astronomers in China, Japan, Europe, and the Arab world all documented this spectacular sight. With the advent of the Space Age in the 1960s, scientists were able to launch instruments and detectors above Earth’s atmosphere to observe the universe in wavelengths that are blocked from the ground, including X-rays. SN 1006 was one of the faintest X-ray sources detected by the first generation of X-ray satellites.
A new image of SN 1006 from NASA’s Chandra X-ray Observatory reveals this supernova remnant in exquisite detail. By overlapping ten different pointings of Chandra’s field-of-view, astronomers have stitched together a cosmic tapestry of the debris field that was created when a white dwarf star exploded, sending its material hurtling into space. In this new Chandra image, low, medium, and higher-energy X-rays are colored red, green, and blue respectively.
The new Chandra image provides new insight into the nature of SN 1006, which is the remnant of a so-called Type Ia supernova. This class of supernova is caused when a white dwarf pulls too much mass from a companion star and explodes, or when two white dwarfs merge and explode. Understanding Type Ia supernovas is especially important because astronomers use observations of these explosions in distant galaxies as mileposts to mark the expansion of the universe.
The new SN 1006 image represents the most spatially detailed map yet of the material ejected during a Type Ia supernova. By examining the different elements in the debris field — such as silicon, oxygen, and magnesium — the researchers may be able to piece together how the star looked before it exploded and the order that the layers of the star were ejected, and constrain theoretical models for the explosion.
Scientists are also able to study just how fast specific knots of material are moving away from the original explosion. The fastest knots are moving outward at almost eleven million miles per hour, while those in other areas are moving at a more leisurely seven million miles per hour. SN 1006 is located about 7,000 light years from Earth. The new Chandra image of SN 1006 contains over eight days worth of observing time by the telescope. These results were presented at a meeting of High Energy Astrophysics Division of the American Astronomical Society in Monterey, CA.
NASA’s Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA’s Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra’s science and flight operations from Cambridge, Mass.
Credits: NASA/CXC/Middlebury College/F.Winklerch
The Small Magellanic Cloud (SMC) is one of the Milky Way’s closest galactic neighbors. Even though it is a small, or so-called dwarf galaxy, the SMC is so bright that it is visible to the unaided eye from the Southern Hemisphere and near the equator. Many navigators, including Ferdinand Magellan who lends his name to the SMC, used it to help find their way across the oceans.
Modern astronomers are also interested in studying the SMC (and its cousin, the Large Magellanic Cloud), but for very different reasons. Because the SMC is so close and bright, it offers an opportunity to study phenomena that are difficult to examine in more distant galaxies.
New Chandra data of the SMC have provided one such discovery: the first detection of X-ray emission from young stars with masses similar to our Sun outside our Milky Way galaxy. The new Chandra observations of these low-mass stars were made of the region known as the “Wing” of the SMC. In this composite image of the Wing the Chandra data is shown in purple, optical data from the Hubble Space Telescope is shown in red, green and blue and infrared data from the Spitzer Space Telescope is shown in red.
Astronomers call all elements heavier than hydrogen and helium — that is, with more than two protons in the atom’s nucleus — “metals.” The Wing is a region known to have fewer metals compared to most areas within the Milky Way. There are also relatively lower amounts of gas, dust, and stars in the Wing compared to the Milky Way.
Taken together, these properties make the Wing an excellent location to study the life cycle of stars and the gas lying in between them. Not only are these conditions typical for dwarf irregular galaxies like the SMC, they also mimic ones that would have existed in the early Universe.
Most star formation near the tip of the Wing is occurring in a small region known as NGC 602, which contains a collection of at least three star clusters. One of them, NGC 602a, is similar in age, mass, and size to the famous Orion Nebula Cluster. Researchers have studied NGC 602a to see if young stars — that is, those only a few million years old — have different properties when they have low levels of metals, like the ones found in NGC 602a.
Using Chandra, astronomers discovered extended X-ray emission, from the two most densely populated regions in NGC 602a. The extended X-ray cloud likely comes from the population of young, low-mass stars in the cluster, which have previously been picked out by infrared and optical surveys, using Spitzer and Hubble respectively. This emission is not likely to be hot gas blown away by massive stars, because the low metal content of stars in NGC 602a implies that these stars should have weak winds. The failure to detect X-ray emission from the most massive star in NGC 602a supports this conclusion, because X-ray emission is an indicator of the strength of winds from massive stars. No individual low-mass stars are detected, but the overlapping emission from several thousand stars is bright enough to be observed.
The Chandra results imply that the young, metal-poor stars in NGC 602a produce X-rays in a manner similar to stars with much higher metal content found in the Orion cluster in our galaxy. The authors speculate that if the X-ray properties of young stars are similar in different environments, then other related properties — including the formation and evolution of disks where planets form — are also likely to be similar.
X-ray emission traces the magnetic activity of young stars and is related to how efficiently their magnetic dynamo operates. Magnetic dynamos generate magnetic fields in stars through a process involving the star’s speed of rotation, and convection, the rising and falling of hot gas in the star’s interior.
The combined X-ray, optical and infrared data also revealed, for the first time outside our Galaxy, objects representative of an even younger stage of evolution of a star. These so-called “young stellar objects” have ages of a few thousand years and are still embedded in the pillar of dust and gas from which stars form, as in the famous “Pillars of Creation” of the Eagle Nebula.
A paper describing these results was published online and in the March 1, 2013 issue of The Astrophysical Journal. The first author is Lidia Oskinova from the University of Potsdam in Germany and the co-authors are Wei Sun from Nanjing University, China; Chris Evans from the Royal Observatory Edinburgh, UK; Vincent Henault-Brunet from University of Edinburgh, UK; You-Hua Chu from the University of Illinois, Urbana, IL; John Gallagher III from the University of Wisconsin-Madison, Madison, WI; Martin Guerrero from the Instituto de Astrofísica de Andalucía, Spain; Robert Gruendl from the University of Illinois, Urbana, IL; Manuel Gudel from the University of Vienna, Austria; Sergey Silich from the Instituto Nacional de Astrofısica Optica y Electr´onica, Puebla, Mexico; Yang Chen from Nanjing University, China; Yael Naze from Universite de Liege, Liege, Belgium; Rainer Hainich from the University of Potsdam, Germany, and Jorge Reyes-Iturbide from the Universidade Estadual de Santa Cruz, Ilheus, Brazil.
Credits: X-ray: NASA/CXC/Univ.Potsdam/L.Oskinova et al; Optical: NASA/STScI; Infrared: NASA/JPL-Caltech
This composite image shows Spitzer infrared emission in pink and Chandra X-ray emission from iron in blue. The infrared emission is very similar in shape and location to X-ray emission (not shown here) from material that was expelled by the giant star companion to the white dwarf before the latter exploded. This material forms a disk around the center of the explosion as shown in the labeled version. This composite figure also shows a remarkably large and puzzling concentration of iron on the left side of the center of the remnant but not the right. The authors speculate that the cause of this asymmetry might be the “shadow” in iron that was cast by the companion star, which blocked the ejection of material. Previously, theoretical work has suggested this shadowing is possible for Type Ia supernova remnants.
Credits: X-ray: NASA/CXC/NCSU/M.Burkey et al; Infrared: NASA/JPL-Caltech.
This is the remnant of Kepler’s supernova, the famous explosion that was discovered by Johannes Kepler in 1604. The red, green and blue colors show low, intermediate and high energy X-rays observed with NASA’s Chandra X-ray Observatory, and the star field is from the Digitized Sky Survey.
As reported in our press release, a new study has used Chandra to identify what triggered this explosion. It had already been shown that the type of explosion was a so-called Type Ia supernova, the thermonuclear explosion of a white dwarf star. These supernovas are important cosmic distance markers for tracking the accelerated expansion of the Universe.
However, there is an ongoing controversy about Type Ia supernovas. Are they caused by a white dwarf pulling so much material from a companion star that it becomes unstable and explodes? Or do they result from the merger of two white dwarfs?
The new Chandra analysis shows that the Kepler supernova was triggered by an interaction between a white dwarf and a red giant star. The crucial evidence from Chandra was a disk-shaped structure near the center of the remnant. The researchers interpret this X-ray emission to be caused by the collision between supernova debris and disk-shaped material that the giant star expelled before the explosion. Another possibility was that the structure is just debris from the explosion.
The disk structure seen by Chandra in X-rays is very similar in both shape and location to one observed in the infrared by the Spitzer Space Telescope. This composite image shows Spitzer data in pink and Chandra data from iron emission in blue. The disk structure is identified with a label.
This composite figure also shows a remarkably large and puzzling concentration of iron on one side of the center of the remnant but not the other. The authors speculate that the cause of this asymmetry might be the “shadow” in iron that was cast by the companion star, which blocked the ejection of material. Previously, theoretical work has suggested this shadowing is possible for Type Ia supernova remnants.
The authors also produced a video showing a simulation of the supernova explosion as it interacts with material expelled by the giant star companion. It was assumed that the bulk of this material was expelled in a disk-like structure, with a gas density that is ten times higher at the equator, running from left to right, than at the poles. This simulation was performed in two dimensions and then projected into three dimensions to give an image that can be compared with observations. The good agreement with observations supports their interpretation of the data.
These results were published online and in the February 10th, 2013 issue of The Astrophysical Journal.
Credits: X-ray: NASA/CXC/NCSU/M.Burkey et al; Infrared: NASA/JPL-Caltech
The highly distorted supernova remnant shown in this image may contain the most recent black hole formed in the Milky Way galaxy. The image combines X-rays from NASA’s Chandra X-ray Observatory in blue and green, radio data from the NSF’s Very Large Array in pink, and infrared data from Caltech’s Palomar Observatory in yellow.
The remnant, called W49B, is about a thousand years old, as seen from Earth, and is at a distance about 26,000 light years away.
The supernova explosions that destroy massive stars are generally symmetrical, with the stellar material blasting away more or less evenly in all directions. However, in the W49B supernova, material near the poles of the doomed rotating star was ejected at a much higher speed than material emanating from its equator. Jets shooting away from the star’s poles mainly shaped the supernova explosion and its aftermath.
By tracing the distribution and amounts of different elements in the stellar debris field, researchers were able to compare the Chandra data to theoretical models of how a star explodes. For example, they found iron in only half of the remnant while other elements such as sulfur and silicon were spread throughout. This matches predictions for an asymmetric explosion. Also, W49B is much more barrel-shaped than most other remnants in X-rays and several other wavelengths, pointing to an unusual demise for this star.
The authors also examined what sort of compact object the supernova explosion left behind. Most of the time, massive stars that collapse into supernovas leave a dense spinning core called a neutron star. Astronomers can often detect these neutron stars through their X-ray or radio pulses, although sometimes an X-ray source is seen without pulsations. A careful search of the Chandra data revealed no evidence for a neutron star, implying an even more exotic object might have formed in the explosion, that is, a black hole.
This may be the youngest black hole formed in the Milky Way galaxy, with an age of only about a thousand years, as viewed from Earth (i.e., not including the light travel time). A well-known example of a supernova remnant in our galaxy that likely contains a black hole is SS433. This remnant is thought to have an age between 17,000 and 21,000 years, as seen from Earth, making it much older than W49B.
The new results on W49B, which were based on about two-and-a-half days of Chandra observing time, appear in a paper in the Feb. 10, 2013 issue of the Astrophysical Journal. The authors of the paper are Laura Lopez, from the Massachusetts Institute of Technology (MIT), Enrico Ramirez-Ruiz from the University of California at Santa Cruz, Daniel Castro, also of MIT, and Sarah Pearson from the University of Copenhagen in Denmark.
Credits: X-ray: NASA/CXC/MIT/L.Lopez et al; Infrared: Palomar; Radio: NSF/NRAO/VLA
This composite image shows the superbubble DEM L50 (a.k.a. N186) located in the Large Magellanic Cloud about 160,000 light years from Earth. Superbubbles are found in regions where massive stars have formed in the last few million years. The massive stars produce intense radiation, expel matter at high speeds, and race through their evolution to explode as supernovas. The winds and supernova shock waves carve out huge cavities called superbubbles in the surrounding gas.
X-rays from NASA’s Chandra X-ray Observatory are shown in pink and optical data from the Magellanic Cloud Emission Line Survey (MCELS) are colored in red, green and blue. The MCELS data were obtained with the University of Michigan’s 0.9-meter Curtis Schmidt telescope at Cerro Tololo Inter-American Observatory (CTIO). The shape of DEM L50 is approximately an ellipse, with a supernova remnant named SNR N186 D located on its northern edge.
Like another superbubble in the LMC, N44, DEM L50 gives off about 20 times more X-rays than expected from standard models for the evolution of superbubbles. A Chandra study published in 2011 showed that there are two extra sources of the bright X-ray emission: supernova shock waves striking the walls of the cavities, and hot material evaporating from the cavity walls.
The Chandra study of DEM L50 was published in the Astrophysical Journal in 2011 and was led by Anne Jaskot from the University of Michigan in Ann Arbor. The Chandra study of DEM L50 was led by Anne Jaskot from the University of Michigan in Ann Arbor. The co-authors were Dave Strickland from Johns Hopkins University in Baltimore, MD, Sally Oey from University of Michigan, You-Hua Chu from University of Illinois and Guillermo Garcia-Segura from Instituto de Astronomia-UNAM in Ensenada, Mexico.
Credits: X-ray: NASA/CXC/Univ of Michigan/A.E.Jaskot, Optical: NOAO/CTIO/MCELS
This movie from NASA’s Chandra X-ray Observatory shows a fast moving jet of particles produced by a rapidly rotating neutron star, and may provide new insight into the nature of some of the densest matter in the universe.
The star of this movie is the Vela pulsar, a neutron star that was formed when a massive star collapsed. The Vela pulsar is about 1,000 light years from Earth, spansis about 12 miles in diameter, and makes over 11 complete rotations every second, faster than a helicopter rotor. As the pulsar whips around, it spews out a jet of charged particles that race out along the pulsar’s rotation axis at about 70% of the speed of light. In this still image from the movie, the location of the pulsar and the 0.7-light-year-long jet are labeled.
The Chandra data shown in the movie, containing eight images obtained between June and September 2010, suggest that the pulsar may be slowly wobbling, or precessing, as it spins. The shape and the motion of the Vela jet look strikingly like a rotating helix, a shape that is naturally explained by precession, as shown in this animation [link to mathematica animation from Oleg K]. If the evidence for precession of the Vela pulsar is confirmed, it would be the first time that a jet from a neutron star has been found to be wobbling, or precessing, in this way.
One possible cause of precession for a spinning neutron star is that it has become slightly distorted and is no longer a perfect sphere. This distortion might be caused by the combined action of the fast rotation and “glitches”, sudden increases of the pulsar’s rotational speed due to the interaction of the superfluid core of the neutron star with its crust.
A paper describing these results will be published in The Astrophysical Journal on January 10, 2013.
This is the second Chandra movie of the Vela pulsar, with the original having been released in 2003. The first Vela movie contained shorter, unevenly spaced observations so that the changes in the jet were less pronounced and the authors did not argue that precession was occurring. However, based on the same data, Avinash Deshpande of Arecibo Observatory in Puerto Rico and the Raman Research Institute in Bangalore, India, and the late Venkatraman Radhakrishnan, argued in a 2007 paper that the Vela pulsar might be precessing.
The Earth also precesses as it spins, with a period of about 26,000 years. In the future Polaris will no longer be the “north star” and other stars will take its place. The period of the Vela precession is much shorter and is estimated to be about 120 days.
The supernova that formed the Vela pulsar exploded over 10,000 years ago. This optical image from the Anglo-Australian Observatory’s UK Schmidt telescope shows the enormous apparent size of the supernova remnant formed by the explosion. The full size of the remnant is about eight degrees across, or about 16 times the angular size of the moon. The square near the center shows the Chandra image with a larger field-of-view than used for the movie, with the Vela pulsar in the middle.
Credits: X-ray: NASA/CXC/Univ of Toronto/M.Durant et al; Optical: DSS/Davide De Martin
The black hole at the center of this galaxy is part of a survey of 18 of the biggest black holes in the universe. This large elliptical galaxy is in the center of the galaxy cluster PKS 0745-19, which is located about 1.3 billion light years from Earth.. X-ray data from NASA’s Chandra X-ray Observatory are shown in purple and optical data from the Hubble Space Telescope are in yellow.
The researchers found that these black holes may be about ten times more massive than previously thought, with at least ten of them weighing between 10 and 40 billion times the mass of the sun.
All of the potential “ultramassive” black holes found in this study lie in galaxies at the centers of galaxy clusters containing huge amounts of hot gas. This hot gas produces the diffuse X-ray emission seen in the image. Outbursts powered by the central black holes create cavities in the gas preventing it from cooling and forming enormous numbers of stars. To generate the outbursts, the black holes must swallow large amounts of mass. Because the largest black holes can swallow the most mass and power the biggest outbursts, ultramassive black holes had already been predicted to exist to explain some of the most powerful outbursts seen.
In addition to the X-rays from Chandra, the new study also uses radio data from the NSF’s Karl G. Jansky Very Large Array (JVLA) and the Australia Telescope Compact Array (ATCA) and infrared data from the 2 Micron All-Sky Survey (2MASS). These results were published [link to press release] in the July 2012 issue of The Monthly Notices of the Royal Astronomical Society.
Credits: X-ray: NASA/CXC/Stanford/Hlavacek-Larrondo, J. et al; Optical: NASA/STScI
The spiral galaxy NGC 3627 is located about 30 million light years from Earth. This composite image includes X-ray data from NASA’s Chandra X-ray Observatory (blue), infrared data from the Spitzer Space Telescope (red), and optical data from the Hubble Space Telescope and the Very Large Telescope (yellow). The inset shows the central region, which contains a bright X-ray source that is likely powered by material falling onto a supermassive black hole.
A search using archival data from previous Chandra observations of a sample of 62 nearby galaxies has shown that 37 of the galaxies, including NGC 3627, contain X-ray sources in their centers. Most of these sources are likely powered by central supermassive black holes. The survey, which also used data from the Spitzer Infrared Nearby Galaxy Survey, found that seven of the 37 sources are new supermassive black hole candidates.
Confirming previous Chandra results, this study finds the fraction of galaxies found to be hosting supermassive black holes is much higher than found with optical searches. This shows the ability of X-ray observations to find black holes in galaxies where relatively low-level black hole activity has either been hidden by obscuring material or washed out by the bright optical light of the galaxy.
The combined X-ray and infrared data suggest that the nuclear activity in a galaxy is not necessarily related to the amount of star-formation in the galaxy, contrary to some early claims. In contrast, these new results suggest that the mass of the supermassive black hole and the rate at which the black hole accretes matter are both greater for galaxies with greater total masses.
A paper describing these results was published in the April 10, 2011 issue of The Astrophysical Journal. The authors are Catherine Grier and Smita Mathur of The Ohio State University in Columbus, OH; Himel GHosh of CNRS/CEA-Saclay in Guf-sur-Yvette, France and Laura Ferrarese from Herzberg Institute of Astrophysics in Victoria, Canada.
Credits: NASA/CXC/Ohio State Univ./C.Grier et al.; Optical: NASA/STScI, ESO/WFI; Infrared: NASA/JPL-Caltech
n this holiday season of home cooking and carefully-honed recipes, some astronomers are asking: what is the best mix of ingredients for stars to make the largest number of plump black holes?
They are tackling this problem by studying the number of black holes in galaxies with different compositions. One of these galaxies, the ring galaxy NGC 922, is seen in this composite image containing X-rays from NASA’s Chandra X-ray Observatory (red) and optical data from the Hubble Space Telescope (pink, yellow and blue).
NGC 922 was formed by the collision between two galaxies – one seen in this image and another located outside the field of view. This collision triggered the formation of new stars in the shape of a ring. Some of these were massive stars that evolved and collapsed to form black holes.
Most of the bright X-ray sources in Chandra’s image of NGC 922 are black holes pulling material in from the winds of massive companion stars. Seven of these are what astronomers classify as “ultraluminous X-ray sources” (ULXs). These are thought to contain stellar-mass black holes that are at least ten times more massive than the sun, which places them in the upper range for this class of black hole. They are a different class from the supermassive black holes found at the centers of galaxies, which are millions to billions of times the mass of the sun.
Theoretical work suggests that the most massive stellar-mass black holes should form in environments containing a relatively small fraction of elements heavier than hydrogen and helium, called “metals” by astronomers. In massive stars, the processes that drive matter away from the stars in stellar winds work less efficiently if the fraction of metals is smaller. Thus, stars with fewer of these metals among their ingredients should lose less of their mass through winds as they evolve. A consequence of this reduced mass loss is that a larger proportion of massive stars will collapse to form black holes when their nuclear fuel is exhausted. This theory appeared to be supported by the detection of a large number (12) of ULXs in the Cartwheel galaxy, where stars typically contain only about 30% of the metals found in the sun.
To test this theory, scientists studied NGC 922, which contains about the same fraction of metals as the sun, meaning that this galaxy is about three times richer in metals than the Cartwheel galaxy. Perhaps surprisingly, the number of ULXs found in NGC 922 is comparable to the number seen in the Cartwheel galaxy. Rather, the ULX tally appears to depend only on the rate at which stars are forming in the two galaxies, not on the fraction of metals they contain.
One explanation for these results is that the theory predicting the most massive stellar-mass black holes should form in metal poor conditions is incorrect. Another explanation is that the metal fraction in the Cartwheel galaxy is not low enough to have a clear effect on the production of unusually massive stellar-mass black holes, and therefore will not cause an enhancement in the number of ULXs. Recent models incorporating the evolution of stars suggest that a clear enhancement in the number of ULXs might only be seen when the metal fraction falls below about 15% of the Sun’s value. Astronomers are investigating this possibility by observing galaxies with extremely low metal fractions using Chandra. The number of ULXs is being compared with the number found in galaxies with higher metal content. The results of this work will be published in a future paper.
A paper describing the results for NGC 922 was published in the March 10, 2012 issue of the Astrophysical Journal. The authors were Andrea Prestwich and Jose Luis Galache of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, MA; Tim Linden from University of Santa Cruz in Santa Cruz, CA; Vicky Kalogera from Northwestern University in Evanston, IL; Andreas Zezas from CfA and University of Crete in Crete, Greece; Tim Roberts from University of Durham in Durham, UK; Roy Kilgard from Wesleyan University in Middletown, CT; Anna Wolter and Ginevra Trinchieri from INAF in Milano, Italy. NASA’s Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA’s Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra’s science and flight operations from Cambridge, Mass.
Credits: X-ray: NASA/CXC/SAO/A. Prestwich et al; Optical: NASA/STScI