Speaking of Hubble...

Archive: Ray Villard

The Lure of the Exoplanet Next Door

October 31, 2012 by Ray Villard
Artist’s impression of the the planet orbiting the star Alpha Centauri B. CREDIT: ESO/L. Calçada/N. Risinger

Artist’s impression of the the planet orbiting the star Alpha Centauri B. CREDIT: ESO/L. Calçada/N. Risinger

Despite the hundreds of extrasolar planets found so far, the discovery of a planet orbiting the nearest star to our Sun has extraordinary consequences for astronomers and the public alike.

The Sun’s nearest neighbor is a multiple star system that lies merely 4.3 light years away – a galactic stone’s throw.

Alpha Centauri is only clearly visible from southern skies as a brilliant white star (it is actually two stars that are too close together to be seen separately by the naked eye). The faint third member of the system, a red dwarf star Proxima Centauri, yields no evidence for planets and is so far from the binary pair as to be inconsequential.

The European Southern Observatory reported the planet discovery on October 17. An instrument called the High Accuracy Radial velocity Planet Searcher, or HARPS, precisely measured small wobbles in the slightly smaller companion star, Alpha Centauri B. This yielded telltale evidence for the presence of an Earth-sized world whirling around the star, completing an orbit every 3.2 days.

The bad news is that the planet is too close to the star to support life as we know it. The surface roasts at over 2,000 degrees Fahrenheit – hot enough for hellish oceans of molten magma.

Alpha Centauri A & B are separated by as much as two billion miles. According to models, they are each capable of forming terrestrial planets despite the perturbing influence of a binary companion. In fact, a companion star can be a gravitationally stabilizing influence, like massive Jupiter is in our solar system.

On the heels of this discovery, the Alpha Centauri system is ripe for far-future exploration. That’s because NASA’s planet-hunting Kepler observatory is showing us that entire planetary systems are common. Kepler has identified several thousand other exoplanets, though most remain to be confirmed by follow-up observations.

What’s more, Kepler is finding that rocky Earth-sized planets are increasingly common. (Kepler is monitoring over 150,000 stars in the constellation Cygnus for telltale planet transits, and Alpha Centauri is not in its field of view). Therefore, it’s probably only a matter of time before other observations turn up additional planets at Alpha Centauri.

It’s also possible that one or more planets could be in the stars’ habitable zones, where temperature are mild enough for stable oceans to exist. The discovery of such a world would eventually be followed by a large enough optical-infrared space observatory that could spectroscopically sample the planet’s atmosphere. Attempts would also be made with NASA’s upcoming 6.5 meter mirror James Webb Space Telescope.

If spectroscopic observations made perhaps with an 8- to 16-meter mirror space telescope confirmed that a planet’s atmosphere has biotracers – such as oxygen, ozone, nitrous oxide, methane, and chlorine – there would be motivation to build a dedicated interferometric array of optical space telescopes. Observations could reveal the waxing and waning of continents and oceans as the planet rotates, and the changing tapestry of weather patterns. SETI observations would monitor the planet for evidence of alien telecommunications.

Today’s fastest space probes would take 40,000 years to get to Alpha Centauri. But by the next century, there could be attempts to send a small probe to the system at extraordinarily faster speeds. Such a mission would have a cruise phase of only 40 years if the technology were to develop for extraordinarily powerful propulsion systems that could accelerate a probe for 10 percent the speed of light. That no small task, but it doesn’t require some imaginary warp drive, simply Newtonian physics. The builders of the spacecraft could live long enough to see data returned from Alpha Centauri.

An ambitious mission would enter orbit around any potentially habitable planet. Robotic landers would be dispatched to observe life up-close and personal. We could behold the effects of Darwinian evolution on an extraterrestrial Serengeti of unimaginably exotic creatures.  By the time we are ready for such a mission we will have matured the required artificial intelligence and nanomachine technology. The autonomous probe would direct its own exploration mission.

Because Alpha Centauri A and B are Sun-like in terms of age and temperature, there has been plenty of time for life to develop on any planets we might find in the habitable zones around either star.

The view from a terrestrial planet in an approximately Earth-sized orbit around Alpha Centauri would certainly be exotic to our experience.  At one point during the planet’s year, the two stars would be in conjunction – in other words, side-by-side in the sky. The closer star would have a glowing disk like the Sun; the other would be more star-like and far more brilliant than Venus.

A planet would be influenced by the radiation from both stars. Every 70 years Alpha Centauri A & B come closest to each other. Warming on an Earth-like world would be brief but intense, raising planet-wide temperature by a few degrees.

Given the awesome power of biological evolution, life would evolve to cope with living with a second star. Life on such a planet might develop two circadian rhythms corresponding to both the length of day on the planet, and orbital period of the binary stars.  There may be planet-wide migrations in anticipation of the approaching “super-summer.” And, there would be a variety of other novel coping mechanisms.

If there were intelligent life present out there, Alpha Centauri astronomers would routinely turn their attention on a bright first-magnitude star in the W-shaped constellation Cassiopeia. It would be our Sun. And the astronomers might muse on what life would be like around a single yellow dwarf star.

Can We Do Galactic Archeology?

September 21, 2012 by Ray Villard
The Whirlpool Galaxy

The Whirlpool Galaxy

When I was under the velvet-black skies of western Texas a few months ago, I had a magnificent view of the star-studded bulge of our galaxy in the direction of the summer constellation Sagittarius.

How many advanced alien civilizations might be in this crowded hub of the Milky Way, I pondered? The problem is that we are embedded in a thick forest of stars, and identifying the location of an extraterrestrial civilization – one that’s attempting to contact us – is the proverbial needle-in-a-haystack search, as the SETI scientists always say.

So instead of looking for signals, perhaps the way to find evidence of E.T. is to scrutinize the physical evidence in a neighboring “forest,” or rather nearby galaxy.

Because even the nearest galaxies are millions of light-years away, any idea of communicating with these aliens is unfeasible. Our observations would be made for purely identifying archeological evidence of the actions of a civilization.

For this to work you would have to look at the tallest trees in that forest, i.e. engineering activities on such a large scale they give an anomalous appearance to the galaxy that cannot be explained by known astronomical processes. The features would instead be the handiwork of super-duper civilizations that are leaving their ecological imprint on the galaxy at a mega-scale.

In 1964, the Soviet astronomer Nikolai Kardeschev hypothesized such extraterrestrial civilizations as Type II. They would surpass our energy production capabilities by a factor of approximately 10 billion. How? By capturing the total energy output of their parent star.

In the early 1960s, physicist Freeman Dyson proposed that a shell could be built around a star to trap much of its energy. The shell would be fabricated from dismantling a planet about the mass of Jupiter.

This so-called “Dyson sphere” is legendary, and there have even been searches for the signature of such artifacts in astronomical infrared databases. The problem is that a star enshrouded in dust would look pretty much like a Dyson sphere. In a survey of 250,000 infrared sky sources cataloged in the 1970s, 17 “quasi-plausible” Dyson sphere signatures came up, according to Richard Carrigan of Fermilab.

It’s imaginable that a super-civilization would begin a wave of colonization that spread out to neighboring solar type stars from its home base. Each offshoot would “astro-form” the colonized planetary system by constructing a Dyson sphere around the host star.

Carrigan envisions seeing “Dyson bubble” in nearby galaxies. These would be clusters of Dyson spheres that enclosed a grouping of stars colonized by a Type II Kardeschev civilization.  The logic is that after you’ve built a backyard fence, you can start to conceptualize building the Great Wall of China and still hope to gain perspective on the process, Carrigan says.

These Dyson bubbles would be detected as anomalous dark voids in a galaxy’s disk. When these voids were observed in infrared light they would glow brightly with the heat radiation from the surfaces of Dyson spheres. This would show that they are not simply voids where solar-type stars are conspicuously missing.

The Hubble Space Telescope is conducting a multi-year survey across a swath of the neighboring Andromeda galaxy. The images are filled with so many resolved stars that they look like grains of sand on a beach. This could make an excellent citizen science project, to scour the Andromeda fields for anomalous-looking regions.

The magnificent face-on Whirlpool galaxy, M51, is an ideal place to go looking for Dyson bubbles. Hubble has photographed the entire galaxy down to a resolution of roughly 15 light-years across.  Present Hubble and Spitzer Space Telescope infrared photos of the Whirlpool reveal the typical galaxy’s intricate cobweb tracing in dusty filaments.

However, a rough qualitative estimate by Carrigan suggests that there are no unexplained bubbles or voids in M51. This analysis is complicated by the fact that the infrared light skeletal pattern of a spiral galaxy pattern itself is shaped by voids.

Gigantic elliptical galaxies, which are completely devoid of light-blocking dust, would look very odd indeed if dark voids were detected. However, the nearest ellipticals are 60 million light-years away and so would require a space telescope much larger than Hubble to yield enough resolution to detect anomalies.

An apparent lack of any evidence for large-scale artifacts in galaxies as old as ours begins to set an upper limit on just how technologically advanced alien civilizations can evolve.

Kardeschev hypothesized about Type III civilizations that would harness the entire energy of a galaxy. The observational evidence for astro-engineering an entire galaxy is lacking, and so it’s fair to say that Type III civilizations just don’t exist at all – or at least not yet.

The universe has had 12 billion years to evolve a Type II or Type III civilization. If there’s no obvious archeological evidence, than maybe intelligent beings don’t evolve all that far beyond our projected capabilities of perhaps mega-engineering on the scale of a single solar system.

Maybe extraterrestrials simply don’t have the motivation, know-how, or the budget.

Is Charon a Moon of Pluto Or a Binary Planet?

August 23, 2012 by Ray Villard
Artist's concept of Pluto and its moon Charon. (NASA)

Artist's concept of Pluto and its moon Charon. (NASA)

This month the infamous “un-planet” Pluto grabbed science headlines with the report of yet another moon whirling around it.

The Hubble Space Telescope discovery brings the tally of icy moons orbiting Pluto to five.

Or is it really four?

A reader wrote me to make the case that Pluto really has only four moons (all discovered by Hubble over the past seven years). He argued that the largest moon in the system, Charon (found in 1978), is really a planet in its own right.

Why? Because Charon is 12 percent the mass of Pluto. That may not seem like much, but our Moon is only .01 percent the mass of Earth.

The consequence is that Pluto and Charon pivot like a waltzing pair of ice skaters around a center of mass.  So do the Earth and Moon, but the center of mass, or barycenter, is inside Earth’s radius. However, alien astronomers watching Earth transiting the Sun would note the passage of our Moon as well. They might catalog Earth as a “double planet.”

That was the reader’s point. Pluto’s four outer satellites don’t really orbit the dwarf planet; they follow Keplerian orbits around the system’s center of mass, which lies between Pluto and Charon. Pluto and Charon complete one pivot around each other every 6.3 days.

When we see a pair of stars twirl around a barycenter, they are classified as binary stars. Binary systems account for at least half of the stars in our galaxy. Binary stars are born through the fragmentation of the collapsing nebula that condensed to form them.

Dozens of binary asteroids have been cataloged since 1993. They may form though the splitting of a single, fragile parent body.

So why not have binary planets too?

The popular theory is that a collision between Pluto and another icy dwarf planet spawned Charon and the other moons. A similar sort of collision has been theorized for the birth of Earth’s moon 4.4 billion years ago, though this theory has recently been questioned.

Other binary planets might be out there, though none have been uncovered in numerous surveys. They may be exceedingly rare outside of debris belts like our asteroid belt and Pluto’s Kupier belt.

Nevertheless, there could be binary planets out there that are inhabitable. The consequences would be extraordinary. The planet where intelligent life first arose would dominate the companion planet. There would be a “space race” to colonize the companion world – and no doubt the winners would subjugate whatever was living there. Travel and trade between the two worlds would become commonplace.

In 2006, the International Astronomical Union (IAU) initially considered characterizing Pluto-Charon as a binary planet.  But in all their hissy-fit fuss over what to call Pluto, Charon was simply left as a satellite of Pluto.

The IAU missed a great opportunity here to break new ground in our classification of oddball planetary bodies.

Only Two Cosmic Disasters Are Certain

July 13, 2012 by Ray Villard
A Sun-like star ends its life by ejecting layers of gas into space.

A Sun-like star ends its life by ejecting layers of gas into space.

The sardonic proverb “nothing is certain but death and taxes,” can now be recast for the cosmos.

The inevitable collision of the Andromeda galaxy with the Milky Way is one of only two astronomical predictions with which we can be absolutely certain. The other is the death of our Sun.

There’s wonderful irony in the presence of Internet soothsayers predicting numerous impossible cosmic disasters this year, simply because the ancient Mayan Calendar “ends” in 2012, when we have real cosmic disasters to concern ourselves with in the future … even though the Milky Way’s “big bang-up” with Andromeda won’t happen for another 4 billion years, and the Sun won’t burn out for another 6 billion years.

In contrast, the eventual galaxy collision is solidly predictable. It will be the result of the inexorable pull of gravity between two heavyweight “island universes,” each weighing over 1 trillion times the mass of our Sun.

The Hubble Space Telescope’s detailed observations show that the Andromeda galaxy is heading straight toward us. Nearly 100 years ago, astronomers knew that Andromeda was coming this way, but they didn’t know if it would be a glancing blow or head-on collision. Hubble astronomers settled the question.

Ever since the nuclear fusion processes taking place deep inside the Sun have been understood, astrophysicists have been able to calculate the Sun’s age and longevity.

We know with absolute certainty that the Sun will burn out 6 billion years from now, leaving Earth a cold, barren cinder. And the Sun’s fate can be extrapolated to every other star in the universe. The very last star burns out 100 trillion years from now.

Hubble shows us the dramatic details of what happens when a Sun-like star burns out. Colorful, hot gases are ejected into space to form bubbles, butterfly shapes, and hourglass shape. We know that the Sun will flame out in a similarly spectacular fireworks display. It will mean the death of Earth, but may simply be another space photo in some extraterrestrial creature’s astronomy textbook 6 billion years from now.

Beyond these two irrevocable events, all other cosmic disasters are simply probabilistic rather than deterministic. You might want to take out homeowners’ insurance against them, but you can still hold out hope you’ll never need to cash in on your policy.

The broad spectrum of cosmic disasters bandied about on the Internet stretches from possible, to improbable, to utterly impossible.

Statistically a planet-killer class asteroid should whack us in less than 100 million years.

A nearby supernova could irradiate Earth within 250 million years.

Chaos theory allows for a small probability that the planets will become unstable in their orbits in a few billion years, and Earth will collide with Mars.

But by then Earth’s oceans will have been evaporated away under the warming sun.

There is an infinitesimally small chance a bypassing star or rogue black hole would run into the Sun. And those odds would slightly increase during the Milky Way collision.

The technological prowess of our civilization should allow humanity to avert many of these disasters. Frankly, we deserve to become extinct if we don’t have the wherewithal to come up with the money and technology to protect Earth from maundering asteroids.

What’s more, straightforward Newtonian physics could be applied to move Earth farther from the aging and warming Sun by setting up an interplanetary pinball game where we rob momentum from asteroids to widen Earth’s orbit.

Though we have evidence for the beginning of the universe, we can only speculate how it will  –or might –end someday.

Dark energy is the wild card here, because if it is unstable over time (which it doesn’t seem to be), it could rip the universe apart or even implode space and time.

Quantum physics allows for a “phase transition” where the universe abruptly ceases to exist into a wave of nothingness that propagates across space at the speed of light.

The Milky Way/Andromeda collision is unique in that it is probably the farthest we can extrapolate into the future with any certainty.

This event needs a name that’s as catchy as the Big Bang. Some ideas from my friends include: The Big Bang-up, The Milky Splay, The Milky Shakeup, and The Big Milky Spill.

But there’s no sense crying over it …

A Virtual Universe Awaits Future Astronomers

May 18, 2012 by Ray Villard
HubbleSite: NSF Grant to Fund "National Virtual Observatory"

Data from ground-based and orbiting telescopes will be united in the National Virtual Observatory.

Being an astronomer in the year 2030 will be notably different than it is today. Yes, scientists will still be pondering, among other mysteries, the evolving universe, life on other worlds, and the nature of dark energy.

But how they explore the universe is already changing. This is partly driven by the fact that we are riding an exponential curve of increasing telescope size and detector sensitivity, but much more importantly, huge amounts of observational data are being harvested and archived faster than astronomers can analyze.

In addition, amateur astronomers are becoming more heavily involved in this analysis than in recent decades because of the “democratization” of space via huge, publicly accessible astronomical databases.

The consequences are that we are on the cusp of a knowledge explosion in astronomy, where discoveries expand at an unprecedented rate across the globe. Our knowledge of the universe is becoming, well, inflationary.

One prime example is the Barbara A. Mikulski Archive for Space Telescopes (MAST), housed at the Space Telescope Science Institute. This remarkably vast database contains astronomical observations from 15 NASA space astronomy missions, including the Hubble Space Telescope and the James Webb Space Telescope.

MAST presently contains approximately 200 terabytes of data that are used and reused many times by astronomers. New data are constantly flowing into the archive, but even more data is flowing out. Today, more than half of published scientific papers containing Hubble data used archival observations. This number has increased steadily over the past five years.

Facilities like MAST will lead to a new breed of “office-chair astronomer” who explores a “virtual universe” of vast, interconnected online databases. This is called the Virtual Observatory, and it is now in its developmental period.

What’s more, “citizen scientists” — those without formal degrees in astronomy — will have open and free access to the same data mines to make their own discoveries.

In 2030, a typical day for an astronomer on a university campus will have her start her work by looking at a list of science papers that have been intelligently selected by a software tool that surfed the Internet overnight. She clicks on an object in an online science paper and the Virtual Observatory database delivers views in X-ray, visible light, and infrared and radio observations. She queries the archive to perform an intelligent search, pulling up information relevant to the questions she’s asking about the object.

She never goes to a mountain top observatory to do follow-up observations of the object. Instead this is all carried out autonomously, following acceptance of her observing proposal. Automatically processed and calibrated observations are quickly delivered for high-level analysis after the observation. This online pipeline processing of data is a procedure pioneered on the Hubble Space Telescope mission, which has amassed 60 terabytes of observations to date.

Her observation goes into the Virtual Observatory archive after a brief proprietary period. Her unrefereed science results are soon published online. Peers and lay readers comment on the results, which are disseminated through social media. Her formally accepted paper is next published freely in an open-access online journal. Students in impoverished third-world universities have the same access to her results as a Harvard astrophysicist does.

Armchair astronomers will focus on complex and innovative queries of the Virtual Observatory to automatically search and extract precise sets of observations made by a variety of telescopes. Researchers will make new discoveries purely by being able to cleverly combine data from different wavelengths, spectra, and transient changes in space.

Many thousands more inquiring minds will be able to explore the databases, too. A prototype for this is the Galaxy Zoo project, where members of the public classify galaxies found in astronomical data. In 2007, Dutch schoolteacher Hanny van Arkel was participating in the Galaxy Zoo project when she found a huge, ghostly, glowing blob of gas, an oddity illuminated by a beam of light from a black hole in the core of a nearby galaxy.

We are just beginning to ride the wave of incredible new insights into our universe.

How Can Planets Get Their Water?

April 19, 2012 by Ray Villard
Artist’s view of super-Earth GJ1214b orbiting a red dwarf star

Super-Earth GJ1214b orbits a red dwarf star (artist’s view).

Over the past year there has been a string of breathless news stories about astronomers finding extrasolar planets in the habitable zone around their star. This is the “Goldilocks zone” where temperatures are not too hot, and not too cold, but just right for surface water to remain liquid and presumably nurture life as we know it.

Astronomers with the Search for Extraterrestrial Intelligence (SETI) are firing up their Allen Array telescope to check out these worlds for signs of intelligent life.

But using the term Earth-like for these planets is stretch at best, and misleading at worst. We don’t have a clue about the physical nature or processes on these worlds, any more than an air traffic control radar blip tells you what meals are being served on a commercial flight.

Saying that water could exist is OK, but to imply it does exist with the phrase “Earth-like planet” is very presumptive.

The bottom line is that we don’t know how Earth got tanked-up with its water supply. So how might we guess what’s happening on worlds thousands of light-years away?

“If we need exotic mechanisms to get water onto Earth, then maybe it suggests life is not prevalent in these exoplanetary systems,” says astrobiologist Karen Meech of the University of Hawaii.

The oceans account for merely one-quarter of one percent of Earth’s mass. Another one-tenth of a percent of water may be in Earth’s mantle. If we could probe deeper, down into the core, Earth could conceivably have 50 oceans worth of water locked away from the days of our planet’s formation. (This is somewhat bemusing, considering Jules Vern wrote about a great subterranean ocean in the 1864 “A Journey to the Center of the Earth.”)

With water potentially so locked away, “we may never know how much water Earth really has,” says Meech.

This complicates several competing theories for how Earth got its water supply in the first place. We know water is everywhere in the solar system, especially among the planets and moons of the outer solar system. They lie beyond the “frost line” where water can remain a solid. By comparison, the baked, rocky planets Mercury and Venus seem bone-dry, and Mars looks arid at best.

From the geologic record we do know that oceans were here on Earth just a few hundred million years after our planet’s formation 4.6 billion years ago.

Recent computer simulations show that all hell would have broken loose in our solar system if the outer planets had ever migrated in their orbits – a phenomenon commonly seen in exoplanetary systems that may also have happened here. Earth would have been pelted with water-bearing asteroids that were thrown into Earth-crossing elliptical orbits. This would explain a late, heavy asteroid bombardment 3.9 billion years ago, as recorded on the moon and other solar system bodies.

Or perhaps water was transported to the early Earth by a class of object that no longer exists? And did the water appear late, early or in intermediate episodes in Earth’s formative years?

The picture is so complicated that it’s safest to say that water came to Earth from many sources: comets, hydrated asteroids, solar nebula gasses, and chemical processing on Earth’s surface.

Because we don’t even know how much water Earth has, we don’t know if our planet is a comparatively dry or wet planet. Now astronomers using Hubble have found a new class of planet that may truly be a water world. Zachory Berta of the Harvard-Smithsonian Center for Astrophysics (CfA) and colleagues have uncovered a new class of planet where a very large fraction of its mass is water. A thick, steamy atmosphere enshrouds it. But don’t plan on going surfing; the surface temperature is 450 degree Fahrenheit.

The waterworld, called GJ1214b, is 2.7 times Earth’s diameter and orbits a red dwarf star every 38 hours at a distance of 1.3 million miles.

In 2010, CfA scientist Jacob Bean and colleagues reported that they had measured the atmosphere of GJ1214b, finding it likely that the atmosphere was composed mainly of water. However, a hazy atmosphere could also explain their observations.

The infrared capabilities of Hubble’s Wide Field Camera 3 were used to study the planet at infrared wavelengths when it passed in front of its star. The team essentially used Hubble to measure the infrared color of sunset on this world. Hazes are more transparent to infrared light than to visible light, so the Hubble observations help tell the difference between a steamy and a hazy atmosphere.

The astronomers found the spectrum of GJ1214b to be featureless over a wide range of colors. The atmospheric model most consistent with the Hubble data is a dense atmosphere of water vapor.

The planet could only have amassed so much water if the planet had formed farther away from its star, beyond the frost line where water ice would be abundant. The planet then migrated inward toward the star, either through friction with gas in the disk or by gravitational interactions with other planetary bodies.

In the process, the wandering planet would have passed through the star’s habitable zone. Therefore, long ago it would have had a balmy ocean like Earth’s. But was the planet there long enough for life to start? The water planet is a prime candidate for further observations with the infrared capabilities of the upcoming James Webb Space Telescope.

We Live in a Compulsive Universe

March 6, 2012 by Ray Villard
An impression of how common planets are around the stars in the Milky Way

An impression of how common planets are around the stars in the Milky Way

There is a “big bang” going on in the search for planets outside of our solar system.

Nearly 2,500 have been discovered so far. And galactic survey estimates have skyrocketed to 100 billion. That’s one planet for every person who has ever lived on the Earth.

Many of the discoveries have come from NASA’s Kepler space observatory. Kepler’s ongoing planet discoveries have overwhelmed the astronomy community.

Gravitational lensing surveys, which look for the distortion of light by an invisible foreground planet, have lead us to the conclusion that planets equal or outnumber the stars in our Milky Way galaxy. This means that within 50 light-years of Earth there could be several dozen habitable planets.

Unlike the Kepler planets, which are very far away, these nearby worlds will be ripe for further scrutiny by the Hubble Space Telescope and its successor, the James Webb Space Telescope. Hubble and Webb will be able to study the structure and chemical content of these planets’ atmospheres. If they have oceans, Webb should be able to detect them.

Kepler’s jaw-dropping observations show that the types of planets and planetary systems out there are so varied that just about anything is possible. The far-flung worlds certainly do not fit our textbook definition of our solar system. Our neighborhood is beginning to look like the oddball.

“Nature must like to form planets because it’s forming them in places that are kind of difficult to do,” says William Welsh of San Diego State University.

If you can imagine it, it exists somewhere, adds Virginia Trimble of the University of California at Irvine. “Exoplanet discoveries have shown us that if it isn’t forbidden by the laws of thermodynamics and Newtonian physics, then it is compulsive.”

The idea of a compulsive universe is as old as Greek philosophy. “There are infinite worlds both like and unlike this world of ours . . .we must believe that in all worlds there are living creatures . . .” wrote Epicurus in 200 B.C.

Galileo’s contemporary, Giordano Bruno, correctly predicted that planets orbiting other stars were too faint to be seen by the newly invented telescope.

But just three decades ago notion of the planets around other stars was still dismissed by some astronomers as unscientifically presumptive. A colleague of mine was almost fired from his planetarium job by an astronomy professor because he wrote a program script that speculated about visiting worlds around other stars. (No doubt the professor was no fan of the “Star Trek” TV series.)

Even in 1980, estimates for the chances for planet around stars ranged from zero to 100 percent.

Things started to shift with discoveries in the 1990s. In 1995, Hubble captured images of the long-hypothesized, planet-forming dust disks around newborn stars, and astronomers found a Jupiter-sized planet orbiting the Sun-like star 51 Pegasi.

The giant planet orbits its star much closer that Mercury does to our Sun, the first hint that the possibilities for exoplanets characteristics might outstrip our imaginations.

At first the planet’s strange orbit seemed like a fluke. It was just some extremely odd happenstance in nature that a giant planet would wind up so close to its star. We expected to find more solar systems like ours, in which the giant planets reside farther away from their stars, and the small, rocky planets hover closer to the center.

But within a decade astronomers were estimating there are nearly 10 billion of these “hot Jupiters” across the galaxy.

Kepler and other searches have now shown that planets can orbit binary stars, that they can whip around their star in very eccentric orbits, and that planets can have the anemic density of Styrofoam or be tougher than solid steel.

Still, there are hardcore skeptics dismissing the possibility of extraterrestrial life on these worlds, even in light of our planet bonanza.

“Extrasolar systems are far more diverse than we expected, and that means very few are likely to support life,” insists Howard Smith of the Harvard Smithsonian Center for Astrophysics. Smith believes that we are the only intelligent life in the universe. But are we really the best that nature can do?

Radio astronomer Seth Shostak, on the other hand, estimates that there are at least 10 trillion trillion Earth-like planets in the entire universe. “You would have to believe in miracles if E.T. did not exist,” he asserts.

I agree with Shostak. Anything is possible in a compulsive universe.

Reflections on Beta Pictoris

April 13, 2011 by Ray Villard
This Hubble Space Telescope view of Beta Pictoris shows a main dust disk and a much fainter secondary dust disk.

This 2003 Hubble view of the area surrounding Beta Pictoris shows a main dust disk and a much fainter secondary disk. (A coronagraph was used to block out the light from the bright star in the center.)

The recent announcement of the discovery of over 1,200 worlds whirling around other stars has accustomed us to the reality of our Milky Way galaxy being chock full of planets. These exoplanets, as they’re called, were discovered by NASA’s Kepler space observatory.

But the granddaddy of the ballooning field of exoplanet research is the blazing star Beta Pictoris, located 63 light-years away in the far southern sky.

Thirty eight years ago — long before exoplanets were ever discovered — the star got astronomers’ attention because it has an odd excess of infrared radiation (IR) for a star of its temperature.

This was identified as the IR glow of a warm dust disk encircling the star. Astronomers know that newborn planets generate dust through collisions. Take a look at our solar system: The Moon was born from a grazing blow to the Earth by a Mars-sized embryonic planet.

Where there’s dust, there could be planets too, astronomers reasoned.

In the early 1980s, a ground-based telescope revealed a pair of spike-like appendages on either side of the star. This was interpreted as an edge-on dust disk.

Beta Pic immediately became the poster child for the possibility of exoplanets (which weren’t first discovered until 1995). All through the 1980s, the somewhat abstruse Beta Pictoris photo appeared in nearly every introductory astronomy textbook and popular space books.

Through the 1990s, the Hubble Space Telescope gleaned spectroscopic evidence for a snowstorm of comets whirling around Beta Pictoris. Soon, crisp Hubble pictures showed there were in fact two disks around the star, perhaps altered by the gravitational tug of an unseen planet. Hubble had accomplished far more than anyone could have ever imagined when the Beta Pictoris disk was first imaged.

In 2009, astronomers at the European Southern Observatory photographed a planet near the star.

Now, new observations show that the planet is indeed orbiting the star according to laws of planetary motion formulated by Johannes Kepler nearly 400 years ago.

Today the much-lauded Beta Pictoris system is like an aging movie star whose celebrity status has been diminished. The Hubble Space Telescope made similar observations in 2004 and 2006 when it photographed a hot, young, Jupiter-sized planet orbiting the star Fomalhaut. The planet was seen moving along its orbit at a rate that Kepler himself would have easily calculated.

Phantom Planet

October 20, 2010 by Ray Villard
TMR-1C appears to lie at the end of a strange filament of light.

TMR-1C appears to lie at the end of a strange filament of light.

Hundreds of planets have been found beyond our solar system. Of these “extrasolar planets,” or “exoplanets” for short, one has remained perplexing and infamous 12 years after its purported discovery.

The object’s formal designation is TMR-1c. It lies about 450 light-years away in the Taurus molecular cloud.  Back in 1998, astronomer Susan Tereby announced that this could be the first exoplanet directly photographed. At the time, Tereby cautiously called it a “candidate planet.”

Hubble’s  infrared image was compellingly believable.  A very red — and therefore cool — pinpoint object was at the end of a ghostly finger of illuminated dust stretching 135 billion miles from a young binary star system. The telltale finger was interpreted as being formed after the planet was gravitationally ejected from the binary system.

But it was not clear if the object was actually co-moving along with the double star, or whether it was actually even in the Taurus star-forming region. The object might look red only because its light is scattered by dust — as we seen in sunsets.

A year after the front-page news announcement of the first snapshot of an exoplanet, Tereby reported that follow-up spectroscopy showed the object was a likely a background star.

But now we have even more data spanning a decade since the Hubble observation. A team of astronomers using the Canada-France-Hawaii telescope looked at the object in 2009. They found it had gotten brighter and bluer — a trick a star could never perform on such a short timescale unless it exploded.

They propose it is a young protoplanet surrounded by a thick, spinning disk of dust. This might explain the variability of the planet’s light. The dust only periodically reddens the starlight when the disk is tilted at the right orientation to us.  The researchers say they support Tereby’s initial analysis, that the object could have been “kicked off the island” by gravitational pinball in the young binary system.

Another team using the European Southern Observatory’s Very Large Telescope in Chile maintains that the object is 5,000 degrees Fahrenheit — way too hot for a planet. But they too think the very red color is produced by a dusty disk scattering light.

There is still a lot more to be learned about TMR-1c, whatever it is.