Quantum Astronomy: Information in the Universe

To quickly summarize the preceding series on the quantum astronomy, in the first article we looked at the double-slit experiment and how it appears to indicate that a single particle of light (a photon) travels through two slits (apertures) to make an interference pattern, apparently being in two places at once, and yet still be detected as a small particle when it registers on a detector screen. In the second article we looked at the uncertainty principle which requires that certain pairs of measurable quantities (position and momentum, for example) cannot both be measured accurately simultaneously. Time and energy are another such set of "complimentary pairs" so that if one measures the energy of a particle really well, one cannot tell very accurately at what time the particle had that energy. This uncertainty principle can be manipulated—one might say that one can trade off one kind of information for another, as long as ignorance is conserved.

In the third article we noted that waves associated with particles in quantum physics are waves of probability (not waves like ocean waves, although they do share many characteristics). So what one can know or cannot know about, for example, which path a photon took to a detector, actually determines what one will detect—for example whether an interference pattern is detected or not. If one cannot tell which path a photon took to a detector, one can get interference, but not otherwise. And finally, in the fourth article, we discussed doing a cosmic-scale double-slit experiment, first proposed by John Wheeler of Princeton University, where a decision about which path a photon takes around a gravitational lens (a galaxy aligned so it can bend light from a more distance quasar) can be decided long after—even billions of years after—the photon had supposedly already left the source and traveled along one path or the other. This was called the "cosmic-scale delayed-choice" experiment.

To review this experiment, John Wheeler (a colleague of Einstein's) proposed that light from a quasar about 7 billion light years away is split by a gravitational lens, and so we have light traveling to us along two paths—A (the shorter path) and B (the longer path, that encounters more of the gravitational lensing galaxy and whose path is "bent" toward us). If a fiber optics cable (trillions of miles long would be needed) could be used to make the distance along the shorter path A equal to the distance along path B, then one could get an interference pattern rather than just an image of A superimposed on an image of B at the detector. But, interestingly, at the detection rate of one photon at a time, that would mean one could decide to have the photon travel both paths at the last moment rather than just path A (or B) – deciding this 7 billion years after the photon supposedly left the quasar! Thus this experiment really meant delayed-choice, to the point where John Wheeler could talk about his hypothetical experiment in terms of altering "history." But it could only be thought at the time (such thought-only experiments were dubbed "gedanken" experiments by Albert Einstein).

Changing this experiment from a gedanken experiment to a performable experiment, my colleague Dr. David Carico and I proposed that one might actually utilize the uncertainty principle itself to replace the trillions-of-miles-long fiber optics cable. This notion was based on the idea that, since knowability or unknowability is the important consideration (rather than actual distances involved), we proposed not so much to make the two paths a photon traveled equal, but rather to just render any difference in the length of the two paths unmeasureable (i.e., unknowable). We proposed that by knowing the energy of the photon very well (by using a narrow band radio filter, for example) that the time that the photon actually had that energy would be unknowable (since time is the complimentary pair of energy). So, if the unknowability in the time is unmeasureably longer than the delay time between the light paths of the gravitational lens itself, then the two paths are, essentially, "unmeasureably equal," and one cannot tell which path the photon took. If one persists in thinking classically, the photon can then be said to have taken both paths then. To put it in physics-ese, we have used the uncertainty principle as a quantum eraser — it erases the quantum nature of a photon, making it a probability wave again, which can "exist" (if probability wave can be said to exist) along both possible paths again.

We did have to go through some mighty refereeing to get this paper in print, however. One of the biggest doubts about this experiment working was related to using it on extended objects in the sky. It was aid that one may measure a point source "traveling" along two paths then, but what if the source is a whole extended galaxy? Well, even galaxies can be thought of as being made up of a lot of "point" sources, so we argued that the technique would still nevertheless apply, as long as one could not tell what the extent of the actual galaxy (angular size on the sky) was. We did this by introducing what is called a "Mach-Zehnder Interferometer"(MZI) which, unlike a double-slit set-up, cannot tell the angular extent of a photon source because it does not produce an interference pattern – it only indicates whether interference is taking place or not. (For those familiar with the MZI, the gravitational lens itself is the first beam splitter in the system and has an effective refractive index so can change the phase of the light. For those of you not familiar with the MZI, thanks for hanging in there so far!)

We also talked with many physicists about this idea and all were encouraging. Freeman Dyson of Princeton Institute for Advanced Studies told us, "I think you're OK." Andre Linde of Stanford University said, "These things are tricky." Daniel Greenberger of City College of New York said, "I think it is worth a try." And John Wheeler (at a scientific meeting on the occasion of his 90th birthday) said, "That's very interesting. I hope you succeed." Of course the actual referees for our paper were more detailed and the process did drag on for a couple of years. Scientists are usually very friendly and happy to discuss new ideas, but when something is going into the refereed scientific literature, that is a whole 'nother story.

One referee wrote, "The validity of the claim that interference would be observed between extended sources if observed through a sufficiently narrow band filter is absolutely critical....if it is right the implications would be extremely profound, and extend far beyond the narrow confines of measuring time delays in lensed systems, as it would completely undermine the conventional understanding of how interferometry works." I have to confess that as I read this at this point I thought "Gulp." But I also realized that—barring anything we and the referees and editors overlooked—on the other hand, if this experiment did not work it would be a more radical departure for physics than if it did. This is because it would imply that the quantum uncertainty principle itself did not apply in some circumstances—did not, for example, extend over macroscopic distances. So, with this argument, our paper was finally accepted.

The great quantum physicist, Richard Feynman, once said (to paraphrase); If you think you understand quantum physics then you don't understand enough to understand that you don't understand it! And Einstein himself once wrote, "I have thought a hundred times as much about the quantum problems as I have about general relativity theory." We can relate. And you are also most welcome to join Einstein's "hundred times" club. You, too, may begin thinking of the universe, not so much in terms of material objects, but rather in terms of information. And as quantum measurement begins to leave the laboratory and extend throughout space I think we're all in for a lot of surprises. And a lot of fun too.

Life's Evolution May Depend on Galaxy

Intelligent life beyond Earth might not be as dim a hope as many scientists think, according to a new study challenging a widely held anti-ET argument.

Many skeptics tout an idea called the anthropic argument that claims extraterrestrial intelligence must be very rare because the time it takes for intelligent life to evolve is, on the average, much longer than the portion of a star's existence that is conducive to such life.

But now astrobiologist Milan M. Cirkovic and colleagues say they've found a flaw in that reasoning.

The anthropic argument, proposed by astrophysicist Brandon Carter in 1983, following on his pioneering work on anthropic principles in 1970s, is built on the assumption that the two timescales - the lifecycle of a star and the time required for evolution of living and intelligent creatures - are completely independent. If this is true, Carter argued, it's extremely unlikely that these two windows of possibility would last roughly the same amount of time, and would occur at the same time.

But that mode of thinking is outdated, Cirkovic claims. In fact, he says the relevant timescales are not independent; they are deeply entwined. "There are many different ways in which planets in our solar system are not isolated," Cirkovic said. "We must not regard habitable planets as closed boxes. If you abandon that assumption of independence, then you have a whole new background in which you can set up various models of astrobiological development."

Cirkovic points to gamma ray bursts, nearby supernovae, and perturbations of comet clouds as possible events in the astrophysical environment of the star that can influence the biological environment on a planet. For example, when a star travels through one of the dense spiral arms of the Milky Way, both its own development and that of its planets could be disrupted by higher levels of interstellar electromagnetic radiation and cosmic rays, due to the higher frequency of star-forming regions and supernova explosions.

All these connections conspire to rule out the independence suggested by Carter and connect the life of a star and the evolution of life on a planet, Cirkovic argues.

Lucky Earth

In the case of the Earth, the two timescales have lined up fortuitously to enable life. Our Sun is about 4.6 billion years old, and Earth is just slightly younger, at 4.5 billion years old. The first, most basic cells are thought to have formed on our planet about 3.8 billion years ago, although the homo genus, to which humans belong, did not appear until about 2.5 million years ago. And modern humans are only about 200,000 years old.

For more than 80 percent of the Sun's existence, life has existed in some form on Earth. It seems the timescales of biology and astrophysics have favorably aligned in our case. According to the anthropic argument, this coincidence means that Earth, and its life, are unique. But Cirkovic thinks the two timescales may not have overlapped by chance. Instead, they may be part of a complex history, involving interdependence of the Earth system with the rest of the Milky Way.

Clocking Catastrophes

Cosmic events like gamma ray bursts or nearby supernovae could reset the astrobiological clock to give a planet and star a second chance to sync up and try again to produce life. Gamma ray bursts are mysterious explosions that release huge amounts of energy, occurring either as the dying explosions of super-massive stars (like Eta Carinae) or collisions of neutron stars in close binary systems. If a gamma ray burst occurred in a large region near a planetary system, it might cause a flash of radiation and possibly cosmic-ray jets that could disrupt life on planets. Supernova explosions, though not quite as energetic as gamma ray bursts (but much more frequent overall), pack quite a wallop as well, and could send a shock of energy to any nearby planets.

"A gamma ray burst won't affect whether life will begin at some particular point in time, but it would affect how quickly life develops or takes hold by causing changes in atmospheric chemistry on the planet," Cirkovic said. "This can be interpreted as resetting astrobiological clocks which tick on each habitable planet in the Milky Way."

This idea leads to a new way of thinking about the origin of life. Instead of a long, gradual evolution, a catastrophic event could spur development of a complex biosphere and intelligent beings, much like the evolutionary theory of punctuated equilibrium predicts that species will undergo long periods of slow evolution punctuated by brief bouts of drastic change.

For instance, paleontologists say that human beings evolved to our present state only thanks to an asteroid impact 65 million years ago that wiped out the planet's primary predator – the dinosaur. Earth has over the course of its history experienced many mass extinctions that had various causes. While extinctions wipe out life, they are also a "reset" button that alters the environment and allows other types of life to emerge. Overall, this is part of a complex set of astrobiological histories that Cirkovic and colleagues dub the "astrobiological landscape" of our Galaxy.

"The speed of evolution is very variable," Cirkovic said. "There is no reason to think that life on Earth has only one single origin. It is quite possible that there were several beginnings of life on Earth."

Cirkovic also notes that the evolution of intelligent life could occur slower or faster in different settings, and need not follow the astrobiological history of the Milky Way.

"Large-scale correlations might cause more such SETI targets to be contemporary with us than would be expected on the basis of planetary age distribution only," Cirkovic said.

NASA Budget Too Slim to Reach Moon by 2020, Panel Says

A White House panel charged with reviewing NASA's exploration plans has dropped any hope of sending astronauts directly to Mars and found the space agency's budget too slim to accomplish its goal of returning humans to the moon by 2020.

After more than six hours of public deliberation on Wednesday, the 10-member committee overseeing the Review for U.S. Human Space Flight Plans decided not to include a plan to send astronauts straight to Mars - called Mars Direct - on its list of options to be considered by President Barack Obama because of its daunting challenges and cost.

"We think Mars Direct is a mission that we're really not prepared to take on technically or financially, and it would likely not succeed," said the committee's chairman Norman Augustine, a former Lockheed Martin CEO, late Wednesday after the televised meeting in Washington, D.C. "I really want to emphasize that we're not giving up on Mars at all."

A manned Mars mission is the ultimate goal, but shifting all of NASA's focus on getting there as soon as possible is not feasible, he added.

The committee is expected to present its initial report to NASA Administrator Charlie Bolden and White House science adviser John Holdren on Friday and file a final version for President Obama's review by the end of the month.

Funding woes

Augustine's committee is reviewing NASA's plan to retire its aging space shuttle fleet and replace it with a capsule-based Orion spacecraft as part of a larger effort to return astronauts to the moon by 2020. But NASA's current budget for human spaceflight through 2020 is not enough to cover the costs of achieving its baseline lunar goal, let alone other alternative options, the committee found.

"This budget is just simply not friendly to exploration," said committee member Sally Ride, a former astronaut and the first American woman in space. "It's very difficult to find an exploration scenario that actually fits within this very restrictive budget guidance that we've been given."

NASA has a budget of about $80 billion for human spaceflight through 2020, about $28 billion less than projected when it first chose the Orion spacecraft and its Ares rockets to succeed the space shuttle fleet. Orion spacecraft are not expected to begin operational flights until 2015, the committee said.

Augustine said that NASA's exploration budget has been cut repeatedly since announcing the new space exploration plan in 2005, hindering its progress. Technical and other delays have also led to the current shortfall, he added. Still he and his committee were surprised none of their options fit in NASA's current budget.

"I did think that one of the current options would fit under the present funding budget," he said. "I thought it might be quite a while before you really got into space and do those exciting things that we were talking about ... I guess I should have realized that it wasn't possible."

Narrowing options

Last week, the committee culled a list of 3,000 options for human spaceflight down to about seven different scenarios.

On Wednesday, committee members refined that list down to four general scenarios that include more funding. They include building Orion spacecraft for eventual manned mission to the moon, as well as options for sending astronauts farther out into deep space to visit near-Earth asteroids or the stable Lagrange points around Earth by the mid- to late-2020s or 2030.

"We very much like the deep space option," Augustine said, adding that his committee is not endorsing one option over another. "It's a doable, viable option."

Only one of the four scenarios includes NASA's planned Ares I rocket, the booster designed to launch Orion capsules into space. Some included extending the International Space Station's lifetime beyond 2016 to 2020.

The committee strongly favored encouraging commercial vehicles for launching astronauts into orbit and suggested setting $2.5 billion aside between 2011 and 2014 to spur development in those spacecraft. It also included options that included spacecraft more heavily derived from current space shuttles, as well as current unmanned heavy-lift rockets like the Delta 4 Heavy and variants of NASA's giant Ares V rocket envisioned to launch lunar landers into orbit.

The potential for in-orbit refueling was cited as a key technological goal for some committee members. But adequate funding is key if NASA is to tackle an innovative, inspiring program that can capture the attention of the American public, committee members said.

"Our view is that it will be difficult with the current budget to do anything that's terribly inspiring in the human spaceflight area," Augustine said.

NASA Needs More Money to Hunt Killer Space Rocks, Report Says

NASA needs more cash in order to meet its goal of finding nearby space rocks that could hit Earth in a devastating impact, a new report says.

Congress ordered NASA in 2005 to find and track 90 percent of the large asteroids near Earth by 2020, but did not set aside the necessary funds required to do the job, according to a report released Wednesday by the National Academy of Sciences.

Without that funding, NASA will not be able to build the new facilities and telescopes required to track potentially threatening asteroids down to the size of about 460 feet (140 meters) across, according to the interim report.

"I think they're pretty much right on," said Lindley Johnson, NASA's manager of the Near-Earth Objects program at the agency's headquarters in Washington.

Johnson told SPACE.com Wednesday that NASA has estimated it needs between $800 million and $1 billion over the course of 12 to 15 years to build and support the more sensitive telescopes required to meet its goal of tracking most of the near-Earth objects.

Astronomer Donald Yeomans, manager of NASA's Near-Earth Object program office at the Jet Propulsion Laboratory in Pasadena, Calif., has said that about 15 percent of the objects 460 feet wide and larger have been found, and only 5 percent of objects down to about 164 feet (50 meters) in size.

One of the top space rocks under observation is 2007 VK184, a 425-foot-wide (130 meters) asteroid that has a 1-in-2,940 chance of hitting Earth sometime between 2048 and 2057. An impact, if it occurred, would cause an explosion roughly equivalent to 150 million tons of TNT, or more than 10,000 times that of the atom bomb dropped on Hiroshima.

NASA is just about 85 percent complete with tracking asteroids about a half-mile (1 km) in size, Johnson said.

Hunting asteroids near Earth

Scientists estimate there are about 100,000 asteroids and comets near Earth, but only about 20,000 are expected to pose any risk of impact. As of Monday, NASA has found 6,330 of those objects, 1,000 of them flying in orbits that could potentially threaten the Earth in the future, Johnson said.

Aside from efforts to launch space-based missions to track incoming asteroids by Germany and Canada, the United States is carrying the bulk of the asteroid watch work, the new report stated. NASA currently has three separate search teams running five different telescopes to hunt for potentially threatening objects near Earth.

The recent impact on Jupiter last month of a previously unknown object has brought Earth's risk of a similar hit back to the forefront. If such an impact occurred on Earth, the results would be catastrophic, scientists have said.

"It caught us a little bit by surprise," Johnson said of the Jupiter impact, which scientists believe was caused by an asteroid or comet.

Johnson said that scientists plan to use data from NASA's new Wide-field Infrared Survey Explorer spacecraft, which is slated to launch in late 2009 to map the night sky in more detail than ever before, to expand their search for near-Earth objects. He and his team are looking forward to the final version of the National Academy of Sciences report.

A final version of the report is slated to be completed by the end of the year.

In the meantime, NASA recently launched a new "Asteroid Watch" Web site (http://www.jpl.nasa.gov/asteroidwatch/) to keep the public current on its work to track near-Earth objects. The Web site launched July 29 to post updates and alert the public to new research and findings via updates, Twitter and an asteroid tracking widget.

Johnson said the Web site was in development long before the Jupiter impact, which occurred just over a week earlier.

"We had actually started work to bring up that Web site a couple of months ago," Johnson said. "That was just another event out of the blue."

Major Breakthrough: First Photos of Planets Around Other Stars

Astronomers have taken what they say are the first-ever direct images of planets outside of our solar system, including a visible-light snapshot of a single-planet system and an infrared picture of a multiple-planet system.

Earth-like worlds might also exist in the three-planet system, but if so they are too dim to photograph. The other newfound planet orbits a star called Fomalhaut, which is visible without the aid of a telescope. It is the 18th brightest star in the sky.

The massive worlds, each much heftier than Jupiter (at least for the three-planet system), could change how astronomers define the term "planet," one planet-hunter said.

Breakthrough technology

Until now, scientists have inferred the presence of planets mainly by detecting an unseen world's gravitational tug on its host star or waiting for the planet to transit in front of its star and then detecting a dip in the star's light. While these methods have helped to identify more than 300 extrasolar planets to date, astronomers have struggled to actually directly image and see such inferred planets.

The four photographed exoplanets are discussed in two research papers published online today by the journal Science.

"Every extrasolar planet detected so far has been a wobble on a graph. These are the first pictures of an entire system," said Bruce Macintosh, an astrophysicist from Lawrence Livermore National Laboratory in California, and part of the team that photographed the multi-planet system in infrared light. "We've been trying to image planets for eight years with no luck and now we have pictures of three planets at once."

Astronomers have claimed previously to have directly imaged a planet, with at least two such objects, though not everybody agreed the objects were planets. Instead, they may be dim, failed stars known as brown dwarfs.

Multi-planet snapshots

Macintosh, lead researcher Christian Marois of the NRC Herzberg Institute of Astrophysics in Canada, and colleagues used the Gemini North telescope and W.M. Keck Observatory on Hawaii's Mauna Kea to obtain infrared images. Infrared radiation represents heat and, along with everything from radio waves to visible light and X-rays, is part of the electromagnetic spectrum.

The trio of worlds orbits a star named HR 8799, which is about 130 light-years away in the constellation Pegasus and about 1.5 times as massive as the sun. The planets are located at distances from their star of 24, 38 and 68 astronomical units (AU). (An astronomical unit equals the average Earth-sun distance of 93 million miles, or about 150 million km.) Other planet-finding techniques work out to only about 5 AU from a star.

The planet closest to the star weighs in at 10 times the mass of Jupiter, followed by another 10 Jupiter-mass planet and then, farther out, a world seven times the heft of Jupiter.

By astronomical standards, the planets are fresh out of the oven, forming about 60 million years ago. That means the orbs are still glowing from heat leftover from their formation. Earth, by comparison, is about 4.5 billion years old.

The most distant planet orbits just inside a disk of dusty debris, similar to that produced by the icy objects of the solar system's Kuiper belt, which lies just beyond the orbit of Neptune.

The setup of this planetary system, along with its dusty belt, suggests it is a scaled-up version of our solar system, Macintosh said. That means other planets closer in to the host star could be waiting for discovery.

"I think there's a very high probability that there are more planets in the system that we can't detect yet," Macintosh said. "One of the things that distinguishes this system from most of the extrasolar planets that are already known is that HR 8799 has its giant planets in the outer parts — like our solar system does — and so has 'room' for smaller terrestrial planets, far beyond our current ability to see, in the inner parts."

Hubble's discovery

University of California, Berkeley, astronomer Paul Kalas led the team of astronomers who took the visible-light snapshot of the single-planet system. The exoplanet has been named Fomalhaut b, and is estimated to weigh no more than three Jupiter masses.

The Hubble Space Telescope's Advanced Camera for Surveys was used to make the image. The camera is equipped with a coronagraph that blocks out the light of the host star, allowing astronomers to view a much fainter planet.

"It's kind of like if driving into the sun and suddenly you flip down your visor, you can see the road easier," Kalas said during a telephone interview. In fact, Fomalhaut b is 1 billion times fainter than its star. "It's not easy to see. That kind of sensitivity has never been seen before," he added.

Fomalhaut b is about 25 light-years from Earth. Photos taken in 2004 and 2006 show the planet's movement over a 21-month period and suggest the planet likely orbits its star Fomalhaut every 872 years at a distance of 119 astronomical units (AU), or 11 billion miles (nearly 18 billion km). That's about four times the distance between Neptune and the sun.

Kalas suspected the planet's existence in 2004 (published in 2005) after Hubble images he had taken revealed a dusty belt that had a sharp inner edge around Fomalhaut. The sculpted nature of the ring suggested a planet in an elliptical orbit was shaping the belt's inner edge. And it was.

"The gravity of Fomalhaut b is the key reason that the vast dust belt surrounding Fomalhaut is cleanly sculpted into a ring and offset from the star," Kalas said. "We predicted this in 2005, and now we have the direct proof."

Kalas' team also suspects that the planet could be surrounded by a ring system with the dimensions of Jupiter's early rings, before the dust and debris coalesced into the four Galilean moons.

What's a planet?

The successful image results could change how planets are defined, said Sara Seager, an astrophysicist at MIT who was not involved in the discoveries.

Until now, mass has been one of the critical pieces of information that could place an object into or out of the planet club. Objects that are too massive, above about 13 Jupiter masses, are considered brown dwarfs. But now formation could also be part of the formula. Both of the new planetary systems revealed dusty disks and suggest the planets must have formed similar to how planets in our solar system and elsewhere are thought to have formed.

So, most astronomers would call the four objects planets, although their masses are only inferred from the luminosities seen in the images.

"Taken together, these discoveries are going to change what we call a planet," Seager told SPACE.com. "Until now people have been arguing about how big can an object be and still be a planet."

Seager added, referring to the multi-planet system, "People want to call the upper mass 12 Jupiter masses. I think it's going to force us to reconsider what a planet is, because even if they are more massive than what we want to call a planet, they're in a disk." In addition, she said, nobody has ever spotted three stars orbiting a host star, as would have to be the case if you were to call the three planets something other than planets.

Aiming for Earth-like planets

These recent direct images reveal giant, gaseous exoplanets in a new light for the first time, revealing not the effects of the planets but the planets themselves. The next goal would be direct images of an Earth-like planet, the astronomers say.

"The discovery of the HR 8799 system is a crucial step on the road to the ultimate detection of another Earth," Macintosh said.

The problem is that terrestrial (Earth-like) planets are orders of magnitude fainter than the giant Jupiter-like worlds, and they are much closer in to their host stars. That means the glare from the star would be overwhelming with today's technology.

The pay-off could be big, though, as such rocky planets could orbit within their habitable zones (where temperatures would allow the existence of liquid water).

"There is plenty of empty space between Fomalhaut b and the star for other planets to happily reside in stable orbits," Kalas said. "We'll probably have to wait for the James Webb Space Telescope to give us a clear view of the region closer to the star where a planet could host liquid water on the surface."