Host: Fraser Cain (@fcain) Special Guest:Andy Weir , author of “The Martian”
Andy was first hired as a programmer for a national laboratory at age fifteen and has been working as a software engineer ever since. He is also a lifelong space nerd and a devoted hobbyist of subjects like relativistic physics, orbital mechanics, and the history of manned spaceflight. “The Martian” is his first novel.
An artists illustration of the early Universe. Image Credit: NASA
There’s nothing more out of this world than quasi-stellar objects or more simply – quasars. These are the most powerful and among the most distant objects in the Universe. At their center is a black hole with the mass of a million or more Suns. And these powerhouses are fairly compact – about the size of our Solar System. Understanding how they came to be and how — or if — they evolve into the galaxies that surround us today are some of the big questions driving astronomers.
Now, a new paper by Yue Shen and Luis C. Ho – “The diversity of quasars unified by accretion and orientation” in the journal Nature confirms the importance of a mathematical derivation by the famous astrophysicist Sir Arthur Eddington during the first half of the 20th Century, in understanding not just stars but the properties of quasars, too. Ironically, Eddington did not believe black holes existed, but now his derivation, the Eddington Luminosity, can be used more reliably to determine important properties of quasars across vast stretches of space and time.
A quasar is recognized as an accreting (meaning- matter falling upon) super massive black hole at the center of an “active galaxy”. Most known quasars exist at distances that place them very early in the Universe; the most distant is at 13.9 billion light years, a mere 770 million years after the Big Bang. Somehow, quasars and the nascent galaxies surrounding them evolved into the galaxies present in the Universe today. At their extreme distances, they are point-like, indistinguishable from a star except that the spectra of their light differ greatly from a star’s. Some would be as bright as our Sun if they were placed 33 light years away meaning that they are over a trillion times more luminous than our star.
An artists illustration of the central engine of a quasar. These “Quasi-stellar Objects” QSOs are now recognized as the super massive black holes at the center of emerging galaxies in the early Universe. (Photo Credit: NASA)
The Eddington luminosity defines the maximum luminosity that a star can exhibit that is in equilibrium; specifically, hydrostatic equilibrium. Extremely massive stars and black holes can exceed this limit but stars, to remain stable for long periods, are in hydrostatic equilibrium between their inward forces – gravity – and the outward electromagnetic forces. Such is the case of our star, the Sun, otherwise it would collapse or expand which in either case, would not have provided the stable source of light that has nourished life on Earth for billions of years.
Generally, scientific models often start simple, such as Bohr’s model of the hydrogen atom, and later observations can reveal intricacies that require more complex theory to explain, such as Quantum Mechanics for the atom. The Eddington luminosity and ratio could be compared to knowing the thermal efficiency and compression ratio of an internal combustion engine; by knowing such values, other properties follow.
Several other factors regarding the Eddington Luminosity are now known which are necessary to define the “modified Eddington luminosity” used today.
The new paper in Nature shows how the Eddington Luminosity helps understand the driving force behind the main sequence of quasars, and Shen and Ho call their work the missing definitive proof that quantifies the correlation of a quasar properties to a quasar’s Eddington ratio.
They used archival observational data to uncover the relationship between the strength of the optical Iron [Fe] and Oxygen[O III] emissions – strongly tied to the physical properties of the quasar’s central engine – a super-massive black hole, and the Eddington ratio. Their work provides the confidence and the correlations needed to move forward in our understanding of quasars and their relationship to the evolution of galaxies in the early Universe and up to our present epoch.
Astronomers have been studying quasars for a little over 50 years. Beginning in 1960, quasar discoveries began to accumulate but only through radio telescope observations. Then, a very accurate radio telescope measurement of Quasar 3C 273 was completed using a Lunar occultation. With this in hand, Dr. Maarten Schmidt of California Institute of Technology was able to identify the object in visible light using the 200 inch Palomar Telescope. Reviewing the strange spectral lines in its light, Schmidt reached the right conclusion that quasar spectra exhibit an extreme redshift and it was due to cosmological effects. The cosmological redshift of quasars meant that they are at a great distance from us in space and time. It also spelled the demise of the Steady-State theory of the Universe and gave further support to an expanding Universe that emanated from a singularity – the Big Bang.
Dr. Maarten Schmidt, Caltech, with Donald Lynden-Bell, were the first recipients of the Kavli Prize in Astrophysics, “for their seminal contributions to understanding the nature of quasars”. While in high school, this author had the privilege to meet Dr. Schmidt at the Los Angeles Museum of Natural History after his presentation to a group of students. (Photo Credit: Caltech)
The researchers, Yue Shen and Luis C. Ho are from the Institute for Astronomy and Astrophysics at Peking University working with the Carnegie Observatories, Pasadena, California.
The blazar 3C 454.3 photographed by the Sloan Digital Sky Survey. It's currently in bright outburst and nearly as bright as the star next to it. Both are about magnitude +13.6. Credit: SDSS
Have an 8-inch or larger telescope? Don’t mind staying up late? Excellent. Here’s a chance to stare deeper into the known fabric of the universe than perhaps you’ve ever done before. The violent blazer 3C 454.3 is throwing a fit again, undergoing its most intense outburst seen since 2010. Normally it sleeps away the months around 17th magnitude but every few years, it can brighten up to 5 magnitudes and show in amateur telescopes. While magnitude +13 doesn’t sound impressive at first blush, consider that 3C 454.3 lies 7 billion light years from Earth. When light left the quasar, the sun and planets wouldn’t have skin in the game for another two billion years.
If we could see the blazar 3C 354.3 up close it would look something like this. A bright accretion disk surrounds a black hole. Twin jets of radiation beam from the center. Credit: Cosmovision
Blazars form in the the cores of active galaxies where supermassive black holes reside. Matter falling into the black hole spreads into a spinning accretion disk before spiraling down the hole like water down a bathtub drain.
Superheated to millions of degrees by gravitational compression the disk glows brilliantly across the electromagnetic spectrum. Powerful spun-up magnetic fields focus twin beams of light and energetic particles called jets that blast into space perpendicular to the disk.
Blazars and quasars are thought to be one and the same, differing only by the angle at which we see them. Quasars – far more common – are actively- munching supermassive black holes seen from the side, while in blazars – far more rare – we stare directly or nearly so into the jet like looking into the beam of a flashlight.
An all-sky view in gamma ray light made with the Fermi Gamma-ray Space Telescope shows bright gamma-ray emission in the plane of the Milky Way (center), bright pulsars and super-massive black holes including the active blazar 3C 454.3 at lower left. Credit: NASA/DOE/International LAT Team
3C 454.3 is one of the top ten brightest gamma ray sources in the sky seen by the Fermi Gamma-ray Space Telescope. During its last major flare in 2005, the blazar blazed with the light of 550 billion suns. That’s more stars than the entire Milky Way galaxy! It’s still not known exactly what sets off these periodic outbursts but possible causes include radiation bursts from shocked particles within the jet or precession (twisting) of the jet bringing it close to our line of sight.
3c 454.3 is near the star Alpha Pegasi just to the west of the Great Square. Use this chart to star hop from Alpha to IM Peg (mag. ~ 5.7). Once there, the detailed map below will guide you to the blazar. Stellarium
The current outburst began in late May when the Italian Space Agency’s AGILE satellite detected an increase in gamma rays from the blazar. Now it’s bright visually at around magnitude +13.6 and fortunately not difficult to find, located in the constellation Pegasus near the bright star Alpha Pegasi (Markab) in the lower right corner of the Great Square asterism.
Using the wide view map, find your way to IM Peg via Markab and then make a copy of the detailed map below to use at the telescope to star hop to 3C 454.3. The blazar lies immediately south of a star of similar magnitude. If you see what looks like a ‘double star’ at the location, you’ve nailed it. Incredible isn’t it to look so far into space back to when the universe was just a teenager? Blows my mind every time.
Detailed map showing the location of the blazar 3C 454.3. I’ve drawn a small asterism using a group of brighter stars with their magnitudes marked. A scale showing 30 arc minutes (1/2 degree) is at right. Click to enlarge. Created with Chris Marriott’s SkyMap software
To further explore 3C 454.3 and blazars vs. quasars I encourage you to visit check out Stefan Karge’s excellent Frankfurt Quasar Monitoring site. It’s packed with great information and maps for finding the best and brightest of this rarified group of observing targets. Karge suggests that flickering of the blazar may cause it to appear somewhat brighter or fainter than the current magnitude. You’re watching a violent event subject to rapid and erratic changes. For an in-depth study of 3C 454.3, check out the scientific paper that appeared in the 2010 Astrophysical Journal.
Learn more about quasars and blazers with a bit of great humor
Finally, I came across a wonderful video while doing research for this article I thought you’d enjoy as well.
This photo combination shows the quasar RX J1131-1231 imaged by NASA's Chandra X-ray Observatory and the Hubble Space Telescope. Credit: X-ray: NASA/CXC/Univ of Michigan/R.C.Reis et al; Optical: NASA/STScI
The spin rate of the most distant supermassive black hole has been measured directly, and wow, is it fast. X-ray observations of RX J1131-1231 (RX J1131 for short) show it is whizzing around at almost half the speed of light. Through X-rays, the astronomers were able to peer at the rate of debris fall into the singularity, yielding the speed measurement.
“We estimate that the X-rays are coming from a region in the disk located only about three times the radius of the event horizon — the point of no return for infalling matter,” stated Jon Miller, an an associate professor of astronomy at the University of Michigan and a co-author on the paper. “The black hole must be spinning extremely rapidly to allow a disk to survive at such a small radius.”
Supermassive black holes are embedded in the heart of most galaxies, and are millions or even billions of times for massive than the Sun. This makes the spin speed astonishingly fast, but also gives astronomers clues about how the host galaxy evolved.
“The growth history of a supermassive black hole is encoded in its spin, so studies of spin versus time can allow us study the co-evolution of black holes and their host galaxies,” stated Mark Reynolds, an assistant research scientist in astronomy at University of Michigan, another co-author on the study.
An artist’s conception of jets protruding from a quasar. Credit: ESO/M. Kornmesser
RX J1131 is six billion light-years away from Earth and classified as a quasar, a type of object that occurs when a lot of matter plunges into a supermassive black hole.
“Under normal circumstances, this faraway quasar would be too faint to study. But the researchers were able to take advantage of a sort of natural telescope effect known as gravitational lensing and a lucky alignment of the quasar and a giant elliptical galaxy to get a closer view,” the University of Michigan stated.
“Gravitational lensing, first predicted by Einstein, occurs when the gravity of massive objects acts as a lens to bend, distort and magnify the light from more distant objects as it passes.”
In this case, the researchers used the Chandra X-ray Observatory and the European Space Agency’s XMM-Newton Telescope to capture the X-ray images.
The research was led Rubens Reis, a postdoctoral research fellow in astronomy the University of Michigan. The paper is published today (March 5) in Nature.
Artist’s interpretation of ULAS J1120+0641, a very distant quasar with a supermassive black hole at its heart.
Credit: ESO/M. Kornmesser
Do you believe in free will? Are people able to decide their own destinies, whether it’s on what continent they’ll live, who or if they’ll marry, or just where they’ll get lunch today? Or are we just the unwitting pawns of some greater cosmic mechanism at work, ticking away the seconds and steering everyone and everything toward an inevitable, predetermined fate?
Philosophical debates aside, MIT researchers are actually looking to move past this age-old argument in their experiments once and for all, using some of the most distant and brilliant objects in the Universe.
Rather than ponder the ancient musings of Plato and Aristotle, researchers at MIT were trying to determine how to get past a more recent conundrum in physics: Bell’s Theorem. Proposed by Irish physicist John Bell in 1964, the principle attempts to come to terms with the behavior of “entangled” quantum particles separated by great distances but somehow affected simultaneously and instantaneously by the measurement of one or the other — previously referred to by Einstein as “spooky action at a distance.”
The problem with such spookiness in the quantum universe is that it seems to violate some very basic tenets of what we know about the macroscopic universe, such as information traveling faster than light. (A big no-no in physics.)
(Note: actual information is not transferred via quantum entanglement, but rather it’s the transfer of state between particles that can occur at thousands of times the speed of light.)
Then again, testing against Bell’s Theorem has resulted in its own weirdness (even as quantum research goes.) While some of the intrinsic “loopholes” in Bell’s Theorem have been sealed up, one odd suggestion remains on the table: what if a quantum-induced absence of free will (i.e., hidden variables) is conspiring to affect how researchers calibrate their detectors and collect data, somehow steering them toward a conclusion biased against classical physics?
“It sounds creepy, but people realized that’s a logical possibility that hasn’t been closed yet,” said David Kaiser, Germeshausen Professor of the History of Science and senior lecturer in the Department of Physics at MIT in Cambridge, Mass. “Before we make the leap to say the equations of quantum theory tell us the world is inescapably crazy and bizarre, have we closed every conceivable logical loophole, even if they may not seem plausible in the world we know today?”
A color composite image of the quasar in HE0450-2958 obtained using the VISIR instrument on the Very Large Telescope and the Hubble Space Telescope. Image Credit: ESO
So in order to clear the air of any possible predestination by entangled interlopers, Kaiser and MIT postdoc Andrew Friedman, along with Jason Gallicchio of the University of Chicago, propose to look into the distant, early Universe for sufficiently unprejudiced parties: ancient quasars that have never, ever been in contact.
…an experiment would go something like this: A laboratory setup would consist of a particle generator, such as a radioactive atom that spits out pairs of entangled particles. One detector measures a property of particle A, while another detector does the same for particle B. A split second after the particles are generated, but just before the detectors are set, scientists would use telescopic observations of distant quasars to determine which properties each detector will measure of a respective particle. In other words, quasar A determines the settings to detect particle A, and quasar B sets the detector for particle B.
By using the light from objects that came into existence just shortly after the Big Bang to calibrate their detectors, the team hopes to remove any possibility of entanglement… and determine what’s really in charge of the Universe.
“I think it’s fair to say this is the final frontier, logically speaking, that stands between this enormously impressive accumulated experimental evidence and the interpretation of that evidence saying the world is governed by quantum mechanics,” said Kaiser.
Then again, perhaps that’s exactly what they’re supposed to do…
The paper was published this week in the journal Physical Review Letters.
Want to read more about the admittedly complex subject of entanglement and hidden variables (which may or may not really have anything to do with where you eat lunch?) Click here.
The quasar QSO 0957+561 appears twice in the center of this image due to a phenomenon known as gravitational lensing, which takes place when light bends around another (massive) object. Credit: ESA/NASA
Optical illusions are awesome. In the center of this image are what appear to be two quasars (or galaxies with huge black holes). In fact, however, it’s the same quasar seen twice. So what’s going on?
QSO 0957+561, also called the “Twin Quasar”, was first spotted in 1979. It lies almost 14 billion light-years from Earth (making it about as old as the Universe itself). Initially, astronomers thought it was indeed two objects, but the distances and characteristics of the twins were too similar.
We “see” the quasar twice because of a ginormous galaxy called YGKOW G1. Its immense gravitational mass is bending the light of the quasar so that it appears twice from our perspective. This phenomenon is called “gravitational lensing”, and it turned out in 1979 that QSO 0957+561 was the first object ever confirmed to experience that. (You can read the original Nature research paper here.)
While the discovery is decades old, it’s still fun to turn telescopes in that direction once in a while to spot the illusion. This particular image is a new one from the Hubble Space Telescope.
A nebula (seen in cyan) that is about two million light-years across. It was found surrounding the bright quasar UM287 (center). Credit: S. Cantalupo (UCSC)
Funny how a single quasar can illuminate — literally and figuratively — some of the mysteries of the universe. From two million light-years away, astronomers spotted a quasar (likely a galaxy with a supermassive black hole in its center) shining on a nearby collection of gas or nebula. The result is likely showing off the filaments thought to connect galaxies in our universe, the team said.
“This is a very exceptional object: it’s huge, at least twice as large as any nebula detected before, and it extends well beyond the galactic environment of the quasar,” stated Sebastiano Cantalupo, a postdoctoral fellow at the University of California Santa Cruz who led the research.
The find illuminated by quasar UM287 could reveal more about how galaxies are connected with the rest of the “cosmic web” of matter, astronomers said. While these filaments were predicted in cosmological simulations, this is the first time they’ve been spotted in a telescope.
“Gravity causes ordinary matter to follow the distribution of dark matter, so filaments of diffuse, ionized gas are expected to trace a pattern similar to that seen in dark matter simulations,” UCSC stated.
A graphic showing how matter in the universe could be distributed. Some astronomers believe matter is sprinkled as a a “cosmic web” of filaments. The larger section shows a dark-matter simulation (by Anatoly Klypin and Joel Primack) and the inset a smaller portion, 10 million light-years across, from another simulation that also includes gas (S. Cantalupo). Credit: S. Cantalupo (UCSC), Joel Primack (UCSC) and Anatoly Klypin (NMSU).
Astronomers added that it was lucky that the quasar happened to be shining in the right direction to illuminate the gas, acting as a sort of “cosmic flashlight” that could show us more of the underlying matter. UM287 is making the gas glow in a similar way that fluorescent light bulbs behave on Earth, the team added.
“This quasar is illuminating diffuse gas on scales well beyond any we’ve seen before, giving us the first picture of extended gas between galaxies,” stated J. Xavier Prochaska, coauthor and professor of astronomy and astrophysics at UC Santa Cruz. “It provides a terrific insight into the overall structure of our universe.”
A quasar resides in the hub of the nearby galaxy NGC 4438. Credit: NASA/ESA, Jeffrey Kenney (Yale University), Elizabeth Yale (Yale University)
50 million light-years away a quasar resides in the hub of galaxy NGC 4438, an incredibly bright source of light and radiation that’s the result of a supermassive black hole actively feeding on nearby gas and dust (and pretty much anything else that ventures too closely.) Shining with the energy of 1,000 Milky Ways, this quasar — and others like it — are the brightest objects in the visible Universe… so bright, in fact, that they are used as beacons for interplanetary navigation by various exploration spacecraft.
“I must go down to the seas again, to the lonely sea and the sky,
And all I ask is a tall ship and a star to steer her by.”
Deep-space missions require precise navigation, especially when approaching bodies such as Mars, Venus, or comets. It’s often necessary to pinpoint a spacecraft traveling 100 million km from Earth to within just 1 km. To achieve this level of accuracy, experts use quasars – the most luminous objects known in the Universe – as beacons in a technique known as Delta-Differential One-Way Ranging, or delta-DOR.
How delta-DOR works (ESA)
Delta-DOR uses two antennas in distant locations on Earth (such as Goldstone in California and Canberra in Australia) to simultaneously track a transmitting spacecraft in order to measure the time difference (delay) between signals arriving at the two stations.
Unfortunately the delay can be affected by several sources of error, such as the radio waves traveling through the troposphere, ionosphere, and solar plasma, as well as clock instabilities at the ground stations.
Delta-DOR corrects these errors by tracking a quasar that is located near the spacecraft for calibration — usually within ten degrees. The chosen quasar’s direction is already known extremely well through astronomical measurements, typically to closer than 50 billionths of a degree (one nanoradian, or 0.208533 milliarcsecond). The delay time of the quasar is subtracted from that of the spacecraft’s, providing the delta-DOR measurement and allowing for amazingly high-precision navigation across long distances.
“Quasar locations define a reference system. They enable engineers to improve the precision of the measurements taken by ground stations and improve the accuracy of the direction to the spacecraft to an order of a millionth of a degree.”
– Frank Budnik, ESA flight dynamics expert
So even though the quasar in NGC 4438 is located 50 million light-years from Earth, it can help engineers position a spacecraft located 100 million kilometers away to an accuracy of several hundred meters. Now that’s a star to steer her by!
I love it when scientists discover something unusual in nature. They have no idea what it is, and then over decades of research, evidence builds, and scientists grow to understand what’s going on.
My favorite example? Quasars.
Astronomers first knew they had a mystery on their hands in the 1960s when they turned the first radio telescopes to the sky.
They detected the radio waves streaming off the Sun, the Milky Way and a few stars, but they also turned up bizarre objects they couldn’t explain. These objects were small and incredibly bright.
They named them quasi-stellar-objects or “quasars”, and then began to argue about what might be causing them. The first was found to be moving away at more than a third the speed of light.
But was it really?
An artist’s conception of jets protruding from an AGN.Maybe we were seeing the distortion of gravity from a black hole, or could it be the white hole end of a wormhole. And If it was that fast, then it was really, really far… 4 billion light years away. And it generating as much energy as an entire galaxy with a hundred billion stars.
What could do this?
Here’s where Astronomers got creative. Maybe quasars weren’t really that bright, and it was our understanding of the size and expansion of the Universe that was wrong. Or maybe we were seeing the results of a civilization, who had harnessed all stars in their galaxy into some kind of energy source.
Then in the 1980s, astronomers started to agree on the active galaxy theory as the source of quasars. That, in fact, several different kinds of objects: quasars, blazars and radio galaxies were all the same thing, just seen from different angles. And that some mechanism was causing galaxies to blast out jets of radiation from their cores.
But what was that mechanism?
This artist’s concept illustrates a quasar, or feeding black hole, similar to APM 08279+5255, where astronomers discovered huge amounts of water vapor. Gas and dust likely form a torus around the central black hole, with clouds of charged gas above and below. Image credit: NASA/ESAWe now know that all galaxies have supermassive black holes at their centers; some billions of times the mass of the Sun. When material gets too close, it forms an accretion disk around the black hole. It heats up to millions of degrees, blasting out an enormous amount of radiation.
The magnetic environment around the black hole forms twin jets of material which flow out into space for millions of light-years. This is an AGN, an active galactic nucleus.
When the jets are perpendicular to our view, we see a radio galaxy. If they’re at an angle, we see a quasar. And when we’re staring right down the barrel of the jet, that’s a blazar. It’s the same object, seen from three different perspectives.
Supermassive black holes aren’t always feeding. If a black hole runs out of food, the jets run out of power and shut down. Right up until something else gets too close, and the whole system starts up again.
The Milky Way has a supermassive black hole at its center, and it’s all out of food. It doesn’t have an active galactic nucleus, and so, we don’t appear as a quasar to some distant galaxy.
We may have in the past, and may again in the future. In 10 billion years or so, when the Milky way collides with Andromeda, our supermassive black hole may roar to life as a quasar, consuming all this new material.
