Using Black Holes to Measure the Universe’s Rate of Expansion

Black Holes

A few years ago, researchers revealed that the universe is expanding at a much faster rate than originally believed — a discovery that earned a Nobel Prize in 2011. But measuring the rate of this acceleration over large distances is still challenging and problematic, says Prof. Hagai Netzer of Tel Aviv University’s School of Physics and Astronomy.

Now, Prof. Netzer, along with Jian-Min Wang, Pu Du and Chen Hu of the Institute of High Energy Physics of the Chinese Academy of Sciences and Dr. David Valls-Gabaud of the Observatoire de Paris, has developed a method with the potential to measure distances of billions of light years with a high degree of accuracy. The method uses certain types of active black holes that lie at the center of many galaxies. The ability to measure very long distances translates into seeing further into the past of the universe — and being able to estimate its rate of expansion at a very young age.

Published in the journal Physical Review Letters (citation below), this system of measurement takes into account the radiation emitted from the material that surrounds black holes before it is absorbed. As material is drawn into a black hole, it heats up and emits a huge amount of radiation, up to a thousand times the energy produced by a large galaxy containing 100 billion stars. For this reason, it can be seen from very far distances, explains Prof. Netzer.

Solving for unknown distances

Using radiation to measure distances is a general method in astronomy, but until now black holes have never been used to help measure these distances. By adding together measurements of the amount of energy being emitted from the vicinity of the black hole to the amount of radiation which reaches Earth, it’s possible to infer the distance to the black hole itself and the time in the history of the universe when the energy was emitted.

Getting an accurate estimate of the radiation being emitted depends on the properties of the black hole. For the specific type of black holes targeted in this work, the amount of radiation emitted as the object draws matter into itself is actually proportional to its mass, say the researchers. Therefore, long-established methods to measure this mass can be used to estimate the amount of radiation involved.

The viability of this theory was proved by using the known properties of black holes in our own astronomical vicinity, “only” several hundred million light years away. Prof. Netzer believes that his system will add to the astronomer’s tool kit for measuring distances much farther away, complimenting the existing method which uses the exploding stars called supernovae.

Illuminating “Dark Energy”

According to Prof. Netzer, the ability to measure far-off distances has the potential to unravel some of the greatest mysteries of the universe, which is approximately 14 billion years old. “When we are looking into a distance of billions of light years, we are looking that far into the past,” he explains. “The light that I see today was first produced when the universe was much younger.”

One such mystery is the nature of what astronomers call “dark energy,” the most significant source of energy in the present day universe. This energy, which is manifested as some kind of “anti-gravity,” is believed to contribute towards the accelerated expansion of the universe by pushing outwards. The ultimate goal is to understand dark energy on physical grounds, answering questions such as whether this energy has been consistent throughout time and if it is likely to change in the future.

Source: American Friends of Tel Aviv University

Reference:

Wang, J., Du, P., Valls-Gabaud, D., Hu, C., & Netzer, H. (2013). Super-Eddington Accreting Massive Black Holes as Long-Lived Cosmological Standards Physical Review Letters, 110 (8) DOI: 10.1103/PhysRevLett.110.081301

Space ‘Scale’ to Weigh Black Holes

black-hole

A new way of measuring the mass of supermassive black holes could revolutionize our understanding of how they form and help to shape galaxies.

The technique, developed by a team including Oxford University scientists, can spot the telltale tracer of carbon monoxide within the cloud of gas (mostly hydrogen) circling a supermassive black hole at the centre of a distant galaxy. By detecting the velocity of the spinning gas they are able to ‘weigh’ (determine the mass) of the black hole.

An image of NGC 4526 showing molecular gas. Image: NASA/ESA/Tim Davies

An image of NGC 4526 showing molecular gas. Image: NASA/ESA/Tim Davies

Detailed information on supermassive black holes, thought to be at the heart of most galaxies, is scarce: it has taken 15 years to measure the mass of just 60. The problem is that most other supermassive black holes are too far away to examine properly even with the Hubble Space Telescope.

The new method, when combined with new telescopes such as ALMA (Attacama Large Millimetre/submillimetre Array), promises to extend this black hole ‘weigh-in’ to thousands of distant galaxies. It will also enable the study of black holes in spiral galaxies (similar to our own Milky Way), which are hard to target using currently available techniques.

A report of the research is published in this week’s Nature (citation below).

The team demonstrated the new technique on the supermassive black hole at the centre of a galaxy, NGC 4526, in the constellation of Virgo. NGC 4526 was chosen as a test because it has been widely studied but the team believe the technique will work on a wide range of different galaxies.

Tim Davis of the European Southern Observatory, lead author of the paper, said, “We observed carbon monoxide molecules in the galaxy we were monitoring using the Combined Array for Research in Millimetre-wave Astronomy (CARMA) telescope. With its super-sharp images we were able to zoom right into the centre of the galaxy and observe the gas whizzing around the black hole. This gas moves at a speed which is determined by the black-hole’s mass, and the distance from it. By measuring the velocity of the gas at each position, we can measure the mass of the black hole.”

Dr Michele Cappellari of Oxford University’s Department of Physics, an author of the paper, said, “Because of the limitations of existing telescopes and techniques we had run out of galaxies with supermassive black holes to observe. Now with this new technique and telescopes like ALMA we will be able to examine the relationship between thousands of more distant galaxies and their black holes giving us an insight into how galaxies and black holes co-evolve. Importantly our ‘weigh-in’ technique will work for all kinds of galaxies, including spiral galaxies which are particularly difficult to observe with previous techniques.”

Dr Martin Bureau of Oxford University’s Department of Physics, an author of the paper, said: “The ALMA telescope is now in the final stages of construction and our team is currently bidding for time to use it for our black hole survey. If all goes according to plan we could begin our survey by the end of this year.”

Source: University of Oxford

Reference:

Davis, T., Bureau, M., Cappellari, M., Sarzi, M., & Blitz, L. (2013). A black-hole mass measurement from molecular gas kinematics in NGC4526 Nature DOI: 10.1038/nature11819

Black Holes as Garbage Dumps

Some commentaries on black holes focus on their form being similar to the initial state of the universe. Since electromagnetic radiation can’t even escape their gravitational pull, John Wheeler decided to apply the name black hole to these objects in 1969. According to some studies, they might very well account for the majority of occupied space.

Assuming that they exist, there might be other uses for them. Black holes are remarkably common, in one manner of thinking. Nothing could escape them, since it’s not possible to exceed the speed of light. Faster than light travel may be theoretically possible by certain means, but nothing could easily get out of a black hole.

That’s why some people have theorized that future societies could use them to dispose of trash. While it might sound absolutely ridiculous, black holes could be the ultimate recycling facilities. Any matter inserted into the event horizon would be turned into some sort of energy at a distant point in the universe.

Disposing of trash this way could also be the ultimate example of mankind’s self-indulgence. After all, no one would ever bother to find out where the matter stream ends up. Humanity could be dumping its trash everywhere in the universe.

Image Credit: StarCraft II

How Black Holes Grow

A study (referenced below) led by a University of Utah astrophysicist found a new explanation for the growth of supermassive black holes in the center of most galaxies: they repeatedly capture and swallow single stars from pairs of stars that wander too close.

Using new calculations and previous observations of our own Milky Way and other galaxies, “we found black holes grow enormously as a result of sucking in captured binary star partners,” says physics and astronomy Professor Ben Bromley, lead author of the study, which is set for online publication April 2 in Astrophysical Journal Letters. Read More →

NuSTAR Mission Update and Overview

Image credit: NASA

On Friday NASA announced that the launch of its newest spacecraft from California will unfortunately be delayed a bit longer. Regardless, I thought I’d post about the mission as this is a project I’m eagerly awaiting. The mission, known as NuSTAR, will map areas of the Milky Way Galaxy. This particular project is one of the least expensive NASA has ever deployed. NASA has announced that launch will hopefully occur within the next two months.

NuStar Mission Overview

One mission objective is to count collapsed stars and black holes near the center of the Milky Way. Scientists also hope to get a closer look at young supernova to understand the formation process as well as  how the different elements of supernovas are created. Furthermore, the mission team hopes to develop a deeper understanding of what powers the jets of particles streaming from the largest black holes. Scientists also hope the mission will encounter a few gamma ray bursts leading to a deeper understanding of them as well.

This will be the first time the new NuSTAR telescope will be used. The folding telescope is at least 10 times stronger than previous telescopes employed on the Chandra and XMM projects. The telescope will be folded until the rocket reaches low earth orbit where it will proceed to unfold. Mission specialists say that the time the telescope takes to unfold will be the scariest aspect of the launch. This will be one of the first times that a folding telescope has been deployed in an unmanned spacecraft.

NuSTAR is a Small Explorer mission led by the California Institute of Technology and managed by NASA’s Jet Propulsion Laboratory, both in Pasadena, Calif., for NASA’s Science Mission Directorate. The spacecraft was built by Orbital Sciences Corporation, Dulles, Va. Its instrument was built by a consortium including Caltech; JPL; the University of California, Berkeley; Columbia University, New York; NASA’s Goddard Space Flight Center in Greenbelt, Md.; the Danish Technical University in Denmark; Lawrence Livermore National Laboratory, Calif.; and ATK Aerospace Systems, Goleta, Calif. NuSTAR will be operated by UC Berkeley, with the Italian Space Agency providing its equatorial ground station located at Malindi, Kenya. The mission’s outreach program is based at Sonoma State University, Calif. NASA’s Explorer Program is managed by Goddard. JPL is managed by Caltech for NASA.

The mission is expected to last two years and results will be published as they become available from this exciting project.

Right now I just hope NASA get things worked out and gets this up in the sky sooner rather than later.

http://www.nasa.gov/mission_pages/nustar/overview/index.html

Supermassive Black Holes May be Shaping Galaxies Faster

Image Credit: Artist concept credit: ESA/AOES Medialab)

The understanding of the way in which supermassive black holes shape galaxies is quickly changing, considering that new data is helping astrophysicists to grasp ultra-fast outflows. There is apparently a correlation between central black holes in galaxies and the velocity of stars in the system. An international team at the Goddard Space Flight Center believes that they have identified a particular outflow model that forges a link between black holes and these velocities.

The current understanding is that supermassive black holes make up the center of most decent sized galaxies. Galatic systems that have additional large black holes seem to have bulges where there are faster-moving stars. There seems to be some sort of a feedback loop between star formation and the black hole. However, as of yet, there is no real solid correlation for why this is.

Recent data that was collected by the project, though, explains that ultra-fast outflows might be speeding up these processes. While they’re not as fast as particle jets, ultra-fast outflows are probably making quicker star formation systems. One can hope that the Astro-H X-ray telescope project will help people better understand these concepts when it is presumably launched in 2014. Until that time, the Goddard Center will continue to look into the physical models behind the outflows.

Reference:
Tombesi, F., Cappi, M., Reeves, J., & Braito, V. (2012). Evidence for ultrafast outflows in radio-quiet AGNs – III. Location and energetics Monthly Notices of the Royal Astronomical Society: Letters DOI: 10.1111/j.1745-3933.2012.01221.x

Tombesi, F., Cappi, M., Reeves, J., Palumbo, G., Braito, V., & Dadina, M. (2011). EVIDENCE FOR ULTRA-FAST OUTFLOWS IN RADIO-QUIET ACTIVE GALACTIC NUCLEI. II. DETAILED PHOTOIONIZATION MODELING OF Fe K-SHELL ABSORPTION LINES The Astrophysical Journal, 742 (1) DOI: 10.1088/0004-637X/742/1/44

Tombesi, F., Cappi, M., Reeves, J., Palumbo, G., Yaqoob, T., Braito, V., & Dadina, M. (2010). Evidence for ultra-fast outflows in radio-quiet AGNs Astronomy and Astrophysics, 521 DOI: 10.1051/0004-6361/200913440

ResearchBlogging.org

Chandra Discovers the Fastest Wind From a Stellar-Mass Black Hole

Making use of NASA’s Chandra X-ray Observatory, astronomers recently announced that they have recorded the quickest wind ever recorded coming off of a stellar-mass black hole. This discovery has important implications for how exactly these type of black holes work.

This record-breaking wind was found to be moving at about 20 million mph, which is about three percent of the speed of light. This is about ten times as fast as astronomers have ever witnessed coming off of a stellar-mass black hole.

Stellar-mass black holes, such as this one, become formed when large stars reach their end and collapse. They have an approximate mass of five to ten times that of our sun. The stellar-mass black hole that produced these particular winds was IGR J17091-3624. These winds are the equivalent of a cosmic category five hurricane, which took astronomers by surprise to see such powerful winds coming from a stellar-mass black hole such as this one. This black hole is relatively small compared to some of the other black holes astronomers have discovered, yet it has produced winds that far exceed that of the larger black holes.

Unlike winds found on Earth, the winds found in the black hole blow in various directions rather then in a single direction. This would send you on quite a ride!

Image Credit: NASA/CXC/M.Weiss

Reference: http://astronomy.com/News-Observing/News/2012/02/Chandra finds fastest wind from stellar-mass black hole.aspx

Milky Way’s Black Hole Devouring Asteroids?

At the center of the Milky Way galaxy (encompasses our solar system) there is a black hole that features a mass of more than three million times that of the sun at its center. This black hole, known as Sagittarius A (SGR A for short), has been detected through various sources of radiation that stem from the direction of the center of the galaxy. However, SGR A has now been found to be grazing and vaporizing asteroids that pass near it according to recent data released from NASA’s Chandra X-ray Observatory. This discovery comes with the finding that there is a cloud of trillions of asteroids and comets hovering around the black hole. Such a finding redefines the current environmental criteria for an asteroid or comet to form in space.

SGR A has likely been consuming tremendous numbers of asteroids as of late as the black hole has been emanating x-ray radiation in larger quantities than usual. Black holes hold true to the notion that ‘what goes in must come out,’ so they often spit out high amounts of radiation as they consume stellar objects. The asteroids and comets from the nearby cloud that pass within approximately 100 million miles of SGR A are likely hopelessly shredded. The space rocks are destroyed due to the high tidal forces associated with the black hole’s mass which creates enormous friction. The asteroids and comets are ripped apart in a similar fashion by which Saturn forms its rings with the exception that these rocks burn up like a meteor. This discovery is just one more clue to the overall mystery of the Milky Way galaxy.

Image credit: universetoday.com