Posted on by Nancy Atkinson

Phoenix Lander Couldn’t Sleep At All Last Night

TEGA oven doors wide open. Credit: NASA/JPL-Caltech/University of Arizona/Texas A&M University

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For the first time, the Phoenix lander stayed up all night. But there was no partying for the little lander, just hard work. Phoenix coordinated its schedule to work together with the Mars Reconnaissance Orbiter to make joint observations to study Mars’ atmosphere. More on that in a minute, but the other big news from the Phoenix lander is that the doors to the Thermal and Evolved Gas Analyzer (TEGA) oven successfully opened, and the device is now ready to accept a sample of icy soil. If you remember, way back in the beginning of the mission, on about Sol 8, the first time the science team relayed orders for the spring-loaded oven doors to open, the doors only opened partially and the team had to vibrate the oven to get the soil inside. But this time, the 10 cm (4 inch) doors stands wide open, and today Phoenix will perfect its techniques to quickly get the icy soil sample inside the oven before the ice sublimates.

Now, about those atmospheric observations: Phoenix used its weather station, stereo camera and conductivity probe to monitor changes in the lower atmosphere and ground surface at the same time MRO studied the atmosphere and ground from above. The orbiter flew repeatedly over Phoenix’s location last evening, so it was good timing for a coordinated effort.

“We are looking for patterns of movement and phase change,” said Michael Hecht, lead scientist for Phoenix’s Microscopy, Electrochemistry and Conductivity Analyzer, which includes the lander’s fork-like thermal and conductivity probe. “The probe is working great. We see some changes in soil electrical properties, which may be related to water, but we’re still chewing on the data.”

The probe was inserted into the soil Sunday for more than 24 hours of measurements coordinated with the atmosphere observations. One goal is to watch for time-of-day changes such as whether some water alters from ice phase to vapor phase and enters the atmosphere from the soil.

The Phoenix team’s plans also include commanding the lander to conduct additional testing of the techniques for collecting a sample of icy soil. When the team is confident about the collecting method, it plans to use Phoenix’s robotic arm to deliver an icy sample to an oven of TEGA.

The team wants to make sure their techniques will quickly bring the soil into the oven, as it’s possible the oven will only work for one more test. The vibrating done to get the soil into the oven for the previous test caused a short circuit that may happen again the next time the oven is activated. The short could be fatal to the oven, but of course, we’re all still holding out hope for a better case scenario.

Original News Source: Phoenix News site

Posted on by Nancy Atkinson

No Life Possible at Edges of the Pinwheel Galaxy

The bright red spots at the edge of the Pinwheel Galaxy means bad news for life. Image credit: NASA/JPL-Caltech/STScI

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Another beautiful image from the Spitzer Space Telescope; in this case, it’s Messier 101, more commonly known as the Pinwheel Galaxy. But the pretty red highlights at the edges of the galaxy are bad news for anyone looking for evidence of life. “If you were going look for life in Messier 101, you would not want to look at its edges,” said Karl Gordon of the Space Telescope Science Institute. “The organics can’t survive in these regions, most likely because of high amounts of harsh radiation.” The red color highlights a zone where organic molecules called polycyclic aromatic hydrocarbons (PAHs), which are present throughout most of the galaxy, suddenly disappear.

PAHs are dusty, carbon-containing molecules found in star nurseries. They’re also found on Earth in barbeque pits, exhaust pipes and anywhere combustion reactions take place. Scientists believe this space dust has the potential to be converted into the stuff of life.

The Pinwheel galaxy is located about 27 million light-years away in the constellation Ursa Major. It has one of the highest known gradients of metals (elements heavier than helium) of all nearby galaxies in our universe. In other words, its concentrations of metals are highest at its center, and decline rapidly with distance from the center. This is because stars, which produce metals, are squeezed more tightly into the galaxy’s central quarters.

Gordon’s team also wanted to learn more about the gradient of the PAHs. Using Spitzer’s Infrared Array Camera and the Infrared Spectograph to carefully analyze the spectra of the PAHs, astronomers can more precisely identify the PAH features, and even deduce information about their chemistry and temperature. The astronomers found that, like the metals, the polycyclic aromatic hydrocarbons decrease in concentration toward the outer portion of the galaxy. But, unlike the metals, these organic molecules quickly drop off and are no longer detected at the very outer rim.

“There’s a threshold at the rim of this galaxy, where the organic material is getting destroyed,” said Gordon.

The findings also provide a better understanding of the conditions under which the very first stars and galaxies arose. In the early universe, there were not a lot of metals or PAHs around. The outskirt of the Pinwheel galaxy therefore serves as a close-up example of what the environment might look like in a distant galaxy.

In this image, infrared light with a wavelength of 3.6 microns is colored blue; 8-micron light is green; and 24-micron light is red. All three of Spitzer instruments were used in the study: the infrared array camera, the multiband imaging photometer and the infrared spectrograph.

Original News Source: JPL

Posted on by Ian O'Neill

Large Chunk of ISS Space Junk Becomes Easy to Observe (Video)

The Easy Ammonia Servicer (EAS) photographed on July 23rd, 2007, by ISS astronauts. Watch your heads, it's re-entering tomorrow! (NASA)

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A huge piece of space debris, weighing 1400 lb (635 kg) and the size of two refrigerators, is gradually falling to Earth, giving observers on the ground a great opportunity to see it. The junk was jettisoned from the International Space Station (ISS) in 2007 and it is expected to re-enter the atmosphere later this year or early 2009. The Early Ammonia Servicer (EAS) was dropped from the ISS after a seven hour spacewalk and pushed in the opposite direction of the space station’s orbit shortly before a re-boost by a Soyuz resupply vehicle. This ensured the EAS would pose no danger to the ISS or crew on future orbits. Now the container is beginning its final few months in space and the bets are on as to where it will crash to Earth…

When the EAS, filled with ammonia coolant, had served its purpose the ISS crew had little choice but to throw it overboard. Astronaut Clay Anderson led the July 23rd 2007 operation with the assistance of cosmonauts Fyodor Yurchikhin and robotic arm operator Oleg Kotov as they shoved the EAS Earth-ward along with a 212 lb (96 kg) stanchion used to attach a camera to the station. The whole EVA lasted 7 hours and 41 minutes and the EAS was noted as the largest single piece of junk dropped from the ISS. At the time, mission control estimated that the EAS would orbit the Earth for 300 days; obviously this was a huge underestimate as it continues to spiral closer to the atmosphere one year after the mission.

Observing the EAS (Marco Langbroek)
Observing the EAS (Marco Langbroek)

The EAS is a huge piece of debris and easily tracked from the ground and poses no threat to missions, but it may be a hazard if, as expected, a large portion of the equipment survives re-entry. Dangers aside for now, the EAS is providing amateur astronomers with a new target to point their telescopes at. When the EAS was jettisoned, it was barely visible to the naked eye as it sped overhead with a magnitude of +4 to +4.5. Two days ago on July 20th, veteran satellite observer Marco Langbroek of Leiden, the Netherlands reported observing the EAS at an observable magnitude of +2.0. But it is moving very fast due to its decreased altitude.

Watch the EAS pass Altair in this high quality piece of video astronomy by Kevin Fetter (July 15th, 2008) »

Currently, the EAS can be seen over Europe, and next week North America will be able to spot it. For information on where and when to look for a chance to observe this huge lump of waste from the ISS, check out SpaceWeather.com’s Simple Satellite Tracker before it starts to flirt with our upper atmosphere in the next few months.

Sources: Space Weather, NASA, Collect Space.

Posted on by Ian O'Neill

The Cosmic Void: Could we be in the Middle of it?

Is our region of space unique? As in there isn't much here? Credit: ESO. Edit: Ian O'Neill

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On large scales, the Universe is homogeneous and isotropic. This means that no matter where you are located in the cosmos, give or take the occasional nebula or galactic cluster, the night sky will appear approximately the same. Naturally there is some ‘clumpiness’ in the distribution of the stars and galaxies, but generally the density of any given location will be the same as a location hundreds of light years away. This assumption is known as the Copernican Principle. By invoking the Copernican Principle, astronomers have predicted the existence of the elusive dark energy, accelerating the galaxies away from one another, thus expanding the Universe. But say if this basic assumption is incorrect? What if our region of the Universe is unique in that we are sitting in in a location where the average density is a lot lower than other regions of space? Suddenly our observations of light from Type 1a supernovae are not anomalous and can be explained by the local void. If this were to be the case, dark energy (or any other exotic substance for that matter) wouldn’t be required to explain the nature of our Universe after all…

Dark energy is a hypothetical energy predicted to permeate through the Cosmos, causing the observed expansion of the Universe. This strange energy is believed to account for 73% of the total mass-energy (i.e. E=mc2) of the Universe. But where is the evidence for dark energy? One of the main tools when measuring the accelerated expansion of the Universe is to analyse the red-shift of a distant object with a known brightness. In a Universe filled with stars, what object generates a “standard” brightness?

NASA, ESA, and A. Field (STScI)
The progenitor of a Type Ia Supernova. Credit: NASA, ESA, and A. Field (STScI)

Type 1a supernovae are known as ‘standard candles’ for this very reason. No matter where they explode in the observable universe, they will always blow with the same amount of energy. So, in the mid-1990’s astronomers observed distant Type 1a’s a little dimmer than expected. With the basic assumption (it may be an accepted view, but it is an assumption all the same) that the Universe obeys the Copernican Principle, this dimming suggested that there was some force in the Universe causing not only an expansion, but an accelerated expansion of the Universe. This mystery force was dubbed dark energy and it is now a commonly held view that the cosmos must be filled with it to explain these observations. (There are many other factors explaining the existence of dark energy, but this is a critical factor.)

According to a new publication headed by Timothy Clifton, from the University of Oxford, UK, the controversial suggestion that the widely accepted Copernican Principle is wrong is investigated. Perhaps we do exist in a unique region of space where the average density is much lower than the rest of the Universe. The observations of distant supernovae suddenly wouldn’t require dark energy to explain the nature of the expanding Universe. No exotic substances, no modifications to gravity and no extra dimensions required.

Clifton explains conditions that could explain supernova observations are that we live in an extremely rarefied region, right near the centre, and this void could be on a scale of the same order of magnitude as the observable Universe. If this were the case, the geometry of space-time would be different, influencing the passage of light in a different way than we’d expect. What’s more, he even goes as far as saying that any given observer has a high probability of finding themselves in such a location. However, in an inflationary Universe such as ours, the likelihood of the generation of such a void is low, but should be considered nonetheless. Finding ourselves in the middle of a unique region of space would out rightly violate the Copernican Principle and would have massive implications on all facets of cosmology. Quite literally, it would be a revolution.

The Copernican Principle is an assumption that forms the bedrock of cosmology. As pointed out by Amanda Gefter at New Scientist, this assumption should be open to scrutiny. After all, good science should not be akin to religion where an assumption (or belief) becomes unquestionable. Although Clifton’s study is speculative for now, it does pose some interesting questions about our understanding of the Universe and whether we are willing to test our fundamental ideas.

Sources: arXiv:0807.1443v1 [astro-ph], New Scientist Blog

Posted on by Nancy Atkinson

NASA to Develop GPS-Like System for the Moon

Future astronauts may use GPS-like system. Credit: The Ohio State University

During the second moonwalk of the Apollo 14 mission, Alan Shepard and Edgar Mitchell were hoping to walk to the 300 meter (1,000 feet) wide Cone Crater on the moon, not far from their landing site. However, the two astronauts were not able to find the crater’s rim amid the rolling, repetitive terrain. Later analysis using pictures the two astronauts took determined they had come within 65 feet of the crater. People are used to having certain visual cues to judge distances, such as the size of a building or another car on the horizon, said Ron Li, who has been awarded a $1.2 million grant to develop a navigation system to be used on the moon. Since the moon has no landmarks or cues to help determine distance, getting lost, or misjudging a distant object’s size and location would be easy, and extremely dangerous. New technology like sensors, inertial navigation systems, cameras, computer processors, and image processors will make the next trip to the moon easier for astronauts.

Li, from The Ohio State University, developed software for the Mars rovers Spirit and Opportunity, which has helped him learn a lot about navigation. The navigation system to help future astronauts find their way around moon won’t use satellites; instead the system will rely on signals from a set of sensors including lunar beacons, stereo cameras, and orbital imaging sensors.

Images taken from orbit will be combined with images from the surface to create maps of lunar terrain. Motion sensors on lunar vehicles and on the astronauts themselves will allow computers to calculate their locations. Signals from lunar beacons, the lunar lander, and base stations will give astronauts a picture of their surroundings similar to what drivers see when using a GPS device on Earth. The researchers have named the entire system the Lunar Astronaut Spatial Orientation and Information System (LASOIS).

Astronauts will have a keypad and screen, possibly right on their spacesuits, to view their location and search for new destinations.

Keeping astronauts safe will be a top priority for Li’s team, which includes experts in psychology and human-computer interaction as well as engineering.

“We will help with navigation, but also with astronauts’ health as well,” Li said. “We want them to avoid the stress of getting lost, or getting frustrated with the equipment. Lunar navigation isn’t just a technology problem, it’s also biomedical.”

News Source: The Ohio State University

Posted on by Ian O'Neill

Successful Test Firing of Orion Jettison Motor (Video)

Successful test-firing of Orion's jettison engines (Aerojet)

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It looks like the hardware is gradually slotting into place for the development of the Orion capsule in NASA’s Constellation Program. On July 17th, the ultimate “ejection seat” was tested by NASA and rocket contractor Aerojet: The Orion jettison motor. Should there be an emergency during Ares rocket/Orion capsule during launch, the Orion capsule will have the capability to eject (whether it is on the launchpad or travelling through the atmosphere), ensuring the safety of the crew. This is the first safety measure of its kind, so a successful engine test can only help to boost confidence in the technology behind Orion…

Although there are concerns for the Constellation Program funding and technology-wise, there is good news coming from the development of NASA’s new Orion crew module. The first full-scale test firing of the jettison motor was successful, boosting confidence in the new safety system the capsule will have installed. Later this year, a full-scale “Pad Abort-1” test is scheduled in the New Mexico desert, where a mock Orion will be blasted clear of a model launchpad (up to a mile in altitude) to test the effectiveness of the system. Tests are already under way to deduce whether a dry or wet touch-down will be carried out by the Orion capsule using cadavers (human corpses) as crash-test dummies.

The jettison motor was tested at the Astrojet facility in Sacramento, California, which marks the start of a series of developmental tests before the finished article is integrated into the mock Orion module to begin the New Mexico tests. During last weeks test firing, engineers were testing acoustic, vibration and shock effects on the engines. It appears everything ran smoothly, indicating the jettison system is close to system-level demonstration.

View the test-firing on the Constellation Project site »

This is a critical stage in the development of Orion. Since the Columbia disaster in 2003, NASA has felt pressure to ensure the safety of their astronauts. Although strict guidelines are in place, space travel remains a risky business where tough decisions need to be made. Installing an Orion jettison system will be a huge piece of mind for mission controllers and Constellation astronauts should there be launch complications on the pad or as Ares powers through the atmosphere.

Source: NASA

Posted on by Tammy Plotner

The “Jewel Box” by Don Goldman

Jewel Box by Don Goldman

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Since it was first observed in a half inch diameter spy glass by Abbe Nicholas Louis de Lacaille during his visit to South Africa in 1751-2, the Kappa Crucis star cluster (NGC 4755) has intrigued and and confounded astronomers since. Today let’s open John Herschel’s ‘casket of variously coloured precious stones’ and take a closer look at the “Jewel Box”…

Situated about 7500 light years away near a vast, dark cosmic dust cloud known as the “Coal Sack”, the Kappa Crucis star cluster has a Bayer designation even though it is a cluster instead of an individual star. Just one look at this colorful array is to understand how it came to be known as the Jewel Box. Sprinkled across 20 light years of space and maybe perhaps only 7.1 million years old, it is home to red, white and blue giant stars alike. If its brightest star were at the center of our own solar system, it would shine 83,000 times brighter than Sol!

The bright orange star is Kappa Crucis, a standout amongst its hot, vivid blue members. A very young star gone into its red supergiant stage? During mid-1862 a man named Francis Abbott began studying the Jewel Box and his observing notes say; “Certain changes that are apparently taking place in the number, position, and colour of its component stars.” This was some pretty radical thinking since he was going up against the notes of the likes of John Herschel and George Airy. But, as so often is the case, sometimes one astronomer can spot what another one can’t and some 10 years later H.C. Russell took Abbott’s notes to heart – measuring and cataloging 130 of the cluster’s stars. Despite extreme criticism, another observer named R.T. Innes also claimed color change as noted in the classic work “Celestial Objects for Common Telescopes”.

Of course, study did not end there and it went into the early 1900s with Trumpler and then Harlow Shapley. The first significantly important astrophysical paper on this cluster appeared in 1958 and was published by Halton Arp and Cecil van Sant who were trying to find out more about galactic supergiant stars. “The three brightest stars are supergiants… and the red star, are all members of the cluster, then NGC 4755 must be somewhat like h and χ Persei… Since these types of clusters are rare, observational material sufficient to derive a colour-magnitude diagram was obtained.” However, as more stars were revealed and studied, the more confusing the designations became! The years progressed and NGC 4755 became even more understood – and better cataloged.

According to studies of helium, carbon, nitrogen and oxygen abundances done by G. Mathys (et al) “After consideration of the CN abundances in this sample, there is no clear evidence of internal mixing. Only three stars among the non-supergiants seem to show a nitrogen enhancement. Two of them have a fairly low projected equatorial velocity (admittedly, they may be rapid rotators seen pole-on); the third one is a definite fast rotator. In the lower gravity stars some kind of mixing has apparently occurred. The supergiants do not differ significantly from the other programme stars in their respective helium contents. The mean helium abundance for each cluster is close to the standard value, (He/H).”

Studying variable stars within open clusters is extremely important. They are clues as to distance and evolution! In young clusters like the Jewel box, the brighter stars should be variables and should be blue. They should also have started evolution away from main sequence, unlike the low mass stars who just quietly burn away their hydrogen. As we know, one of the principle variable types are the Beta Cepheid stars and studies done by Stankov (et al) show the detection of four new variable stars in NGC 4755. “We give frequency solutions as indicators of the time-scales and amplitudes of the pulsations. NGC 4755-116 is probably a B2 dwarf with a period of 4.2 d whose variability is caused by a spot or g-mode pulsation. NGC 4755-405 can be considered as a new β Cephei star with two pulsation frequencies. For NGC 4755-215 we found one frequency and for NGC 4755-316 three pulsation frequencies; we suggest that both are new slowly pulsating B stars of short period.” These variations may be caused by radial pulsations from an instable hydrogen core and even more studies are needed.

But is there more? Yes. Very recent studies done by C. Bonatto (et al) show the dynamical state of NGC 4755. “We explore the possibility that, at the cluster age, some main sequence and pre-main sequence stars still present infrared excesses related to dust envelopes and proto-planetary discs. The core is deficient in PMS stars, as compared with MS ones. NGC 4755 hosts binaries in the halo but they are scarce in the core. Compared to open clusters in different dynamical states studied with similar methods, NGC 4755 fits relations involving structural and dynamical parameters in the expected locus for its age and mass.”

Did NGC 4755 form from the same molecular cloud? Is it two overlapping clusters? Does the proximity of the Coal Sack influence its visual properties? No matter what the science is behind it, the light that you see now left about the same time the Great Pyramids of Egypt were being built. Let the words of Burnham ring the loudest: “…a brilliant and beautiful galactic duster ranking among the finest and most spectacular objects of the southern Milky Way… The cluster lies in a rich and remarkable region in the Heavens, well worth exploring with low power telescopes and instruments of the rich-field type.”

This week’s awesome image was done by Don Goldman and taken at Macedon Ranges Observatory. We thank you!

Posted on by Nancy Atkinson

NASA’s Use of Cadavers to Test the Orion Capsule

Orion Crew Capsule. Credit: Howstuffworks.com

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NASA is debating whether the new Orion capsule should land in the water, like Apollo, or on land, similar to how the Russian Soyuz capsule returns to Earth. To help them determine the potential for human injuries with each possible landing scenario, NASA has used human cadavers during their tests. At first, this revelation may seem quite morbid or even gruesome. But as Keith Cowing said in his expose article on Space Ref and NASA Watch on this subject, “Given the potentially hazardous nature of the tests required, cadavers must be used in the place of living persons.” Sometimes, crash-test dummies or computer simulations don’t provide the crucial information needed, such as the forces on the spinal cord or internal organs. If NASA doesn’t have that information, they can’t get accurate test results. Living test subjects could possibly be killed during the landing tests. Imagine the headlines if that happened. So they have used cadavers. The cadavers NASA used were donated to science to be used for exactly this type of purpose, and NASA, of course, went through the proper channels to obtain the cadavers and treats them in an ethical manner. So while this may seem a little grisly, NASA is doing the right thing.

Marc Carreau from the Houston Chronicle also wrote an article on this subject, and he interviewed David Steitz, a spokesman for NASA’s medical division. “It’s a socially awkward topic,” Steitz said. “The bodies are all carefully handled through all of the tests. We follow ethical medical procedures with these bodies that have been donated for science.”

Three human bodies were used during testing last year, said NASA seat engineer Dustin Gohmert, to help determine the potential for serious human injury during descent and landing. “The interface between the spacesuit and the seats is relatively complex, much more so than in an automobile, even one from the racing industry,” Gohmert said. “The (forces) we anticipate have never been studied before. We are using this research to help define and refine the suits and the seats.”

Tests using human bodies has been done for previous spacecraft, as well.

Cowing received this statement from NASA on the use of cadavers:

“In limited cases, postmortem human subject tests may be performed when insufficient data are available from simulations that use dummies or from mathematical modeling of the human body responses. This is particularly critical where the dynamic responses of internal organs and soft tissue must be evaluated. Using a combination of test methods, the engineering and scientific teams at NASA are able to enhance astronaut safety by designing landing attenuation systems that will minimize accelerations imparted to the crew and significantly reduce the potential for injuries.”

Personally, I could imagine donating my body for this type of research. Even if I never get to fly to space when I’m alive, I’d be proud to help the rest of the human race get there and return safely by giving my body for tests such as this.

News Sources: NASA Watch, Space Ref, Houston Chronicle

Posted on by Nancy Atkinson

Hubble Survey of Gravitational Lenses Yields Measure of Dark Matter in Distant Galaxies

Hubble Space Telescope image shows Einstein ring of one of the SLACS gravitational lenses, with the lensed background galaxy enhanced in blue. A. Bolton (UH/IfA) for SLACS and NASA/ESA.

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An international team of astronomers have compiled the largest-ever single collection of “gravitational lens” galaxies, and their survey yielded information on the masses of galaxies, including an inference of the amount of dark matter. Gravitational lensing occurs when two galaxies happen to aligned with one another along our line of sight in the sky. The gravitational field of the nearer galaxy distorts the image of the more distant galaxy into multiple arc-shaped images. Sometimes this effect even creates a complete ring, known as an “Einstein Ring.” The findings of this survey helps settle a long standing debate over the relationship between and mass and luminosity in galaxies.

Using the Advanced Camera for Surveys on the Hubble Space Telescope to image galaxies that had been identified as gravitational lens galaxies by the Sloan Digital Sky Survey, the team was able to measure the distances to both galaxies in each “lensing” set, as well as measure the masses of each galaxy.

Gravitational lensing creates a “mirage” of a ring, and the Einstein ring images can be up to 30 times brighter than the image of the distant galaxy would be in the absence of the lensing effect. By combining Hubble and Sloan data into the Sloan Lens ACS (or SLACS) Survey, the team was able to make a mathematical model describing the lensing effect and use that model to illustrate what we would see if we could remove the lensing effect.

Animation of the lensing effect.

“The SLACS collection of lenses is especially powerful for science,” said Adam Bolton from the University of Hawaii, lead author of two papers describing these latest results. “For each lens, we measured the apparent sizes of the Einstein rings on the sky using the Hubble images, and we measured the distances to the two galaxies of the aligned pair using Sloan data. By combining these measurements, we were able to deduce the mass of the nearer galaxy.”

By considering these galaxy masses along with measurements of their sizes, brightnesses, and stellar velocities, the SLACS astronomers were able to infer the presence of “dark matter” in addition to the visible stars within the galaxies. Dark matter is the mysterious, unseeable material that is the majority of matter in the universe. And with such a large number of lens galaxies across a range of masses, they found that the fraction of dark matter relative to stars increases systematically when going from galaxies of average mass to galaxies of high mass.

Mosaic of the SLACS galaxies. Credit: SLACS and NASA/ESA.
Mosaic of the SLACS galaxies. Credit: SLACS and NASA/ESA.

Albert Einstein predicted the existence of gravitational lenses in the 1930’s, but the first example was not discovered until the late 1970s. Since then, many more lenses have been discovered, but their scientific potential has been limited by the disparate assortment of known examples. The SLACS Survey has significantly changed this situation by discovering a single large and uniformly selected sample of strong lens galaxies. The SLACS collection promises to form the basis of many further scientific studies.

Original News Source: University of Hawaii

Posted on by Ian O'Neill

How do you Weigh a Supermassive Black Hole? Take its Temperature

A composite image of Chandra and Hubble Space Telescope observations of giant elliptical galaxy NGC 4649 (ASA/STScI/NASA/CXC/UCI/P. Humphrey et al.)

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Working out the mass of huge black holes, like the ones hiding in the centre of galactic nuclei, is no easy task and attempts are being made to find novel ways to weigh them. Using data from the Chandra X-ray Observatory, two scientists have confirmed a theory they conceived ten years ago, that the supermassive black holes in the centre of galaxies strongly influence the nature of the gases surrounding them. So, acting like a remote thermometer, Chandra is being used to probe deep into the neighbourhood of these exotic objects, gauging their masses very accurately…

The supermassive black hole at the centre of NGC 4649 is a monster. It is about 3.4 billion times the mass of the Sun and a thousand times bigger than the black hole at the centre of the Milky Way. This fact makes it an ideal candidate to test new methods of measuring the mass of black holes to see how the results correlate with traditional methods. With a high degree of accuracy, scientists have proven that a previously untested theory of weighing black holes works by using the Chandra X-ray telescope.

Until now, supermassive black hole masses have been measured by observing the motions of stars and gas deep inside galactic nuclei, now astronomers are using the gravitational influence of the black hole over the hot gas trapped around the singularity. As the gas is pulled slowly toward the black hole, it is compressed and heated. The bigger the black hole, the higher the peak temperature. Chandra has been used to measure the peak temperature of the gas right in the centre of NGC 4649 to find the derived mass is identical to the mass previously measured by traditional means.

Fabrizio Brighenti from the University of Bologna in Italy, and William Mathews from the University of California at Santa Cruz have been working on this research for the past decade. It is only now, with the availability of a telescope as powerful as Chandra that these observations have been possible.

“It was wonderful to finally see convincing evidence of the effects of the huge black hole that we expected. We were thrilled that our new technique worked just as well as the more traditional approach for weighing the black hole.” – Fabrizio Brighenti

The black hole inside NGC 4649 appears to be in a dormant state; it doesn’t seem to be pulling in material toward its event horizon very rapidly and it isn’t generating much light as it slowly grows. Therefore, using Chandra to indirectly measure its mass by sensing the peak temperature of surrounding matter is required to weigh it. In the early universe, huge black holes such as these will have generated dramatic displays of light. Now, in the local Universe, such black holes lead a more retiring life, making them difficult to observe. This prospect excites the lead scientist on the project, Philip Humphrey. “We can’t wait to apply our new method to other nearby galaxies harboring such inconspicuous black holes,” he said.

Source: Physorg.com