Archive for the ‘Milky Way Galaxy’ Tag

Life in the Universe VI: Space, the Desert & Exoplanets   8 comments

The Milky Way may be home to million or billions of other living planets, but there are enormous empty spaces between us.

The Milky Way may be home to million or billions of other living planets, but there are enormous empty spaces between us.

Space is on my mind here in the deserts of southern Utah.  It isn’t so much that when the sun goes down in the desert the stars shine brightly.  It is the very nature of the desert itself.  The way small clusters of people and houses seem to occur randomly with huge empty spaces between them reminds me of the scarcity of life in an immense void.

And during this time of year at least, the way the temperature drops so quickly at night and rises almost as quick in the morning reminds me of being on an airless planet where the nearby star’s light brings intense heat during the day and biting cold at night.

The landscapes of the American southwest can often be mistaken for alien ones.  On this morning I watched a couple rock climbers scale this pinnacle.

The landscapes of the American southwest can often be mistaken for alien ones. On this morning I watched a couple rock climbers scale this pinnacle.

This is an ongoing series on my blog, believe it or not.  Like space, there are long journeys involved in going from one post to the next in the series.  The last installment, Part V, began to explore the question of life outside the solar system by highlighting the indomitable Carl Sagan.  Part IV discussed the search for life within our own solar system.  This part will continue to explore the idea of life out in the universe as a whole – a challenging subject I admit I’ve been avoiding.

The question that I posed to begin, the one which underpins the meaning of this series, is explained in Part I.

The large expanses of desert are accentuated by the lack of trees, the bare rock, and the big sky.

The large expanses of desert are accentuated by the lack of trees, the bare rock, and the broad skies.

The Milky Way rises over rock formations in Canyonlands National Park, Utah.

The Milky Way rises over rock formations in Canyonlands National Park, Utah.

The Quest for Exoplanets

Humans have found over 1000 planets outside our own solar system to date, with well over 3000 potential candidates.  In typical parochial fashion, we call these extra-solar worlds exoplanets.  The Kepler space telescope is one of the finest tools we have in the quest to find exoplanets.  It explores a constellation-sized area of the Milky Way Galaxy near Cygnus, the Swan (aka the Northern Cross).

Kepler continuously monitors the brightness of more than 145,000 stars.  It looks for a slight dimming in brightness indicative of a planet crossing between earth and the star. Think of trying to detect the dimming of a bright streetlight a mile away when a moth flies in front of it and you have the idea.

To find exoplanets, astronomers have traditionally used the slight wobble of a star that occurs when an orbiting planet tugs on it.  This gives us good information on the sizes of the planets, along with how close they orbit to their host stars.  More recently the Spitzer space telescope has detected, for the first time, actual light coming from an exoplanet.  This is key.  In order to find out anything about the surfaces of these worlds we need to examine the light bouncing off them or skimming through their atmospheres.  Spitzer and some ground-based telescopes can do the former while Kepler is uniquely suited for the latter.

Turret Arch greets a rising Orion the Hunter.

Turret Arch greets a rising Orion the Hunter.

Candidates for Life

Most of what we’ve found thus far have been very massive exoplanets the size of Jupiter and larger.  Many of these “hot Jupiters” orbit very close to their stars, closer even than our own Mercury.  As our techniques get more refined and as more time goes by (allowing the wobble method to work on exoplanet candidates orbiting further from their stars), we are finding more and more planets that are close to the size of Earth.

Crucially, we are now finding planets that orbit their stars at a distance which allows liquid water to exist.  This orbital distance, which in our solar system essentially extends from Venus to Mars, is the “habitable zone”, also known as the Goldilocks Zone. Combining these two factors that are relevant to the search for earth-like life (the planet’s size and distance to its parent star), we have found to date 12 earth-like exoplanets.

The size and brightness of the host star makes a big difference in how close a planet can orbit and still be cool enough for liquid water and possible life.  We have found only one earth-sized, rocky planet thus far (Gliese 581-g), and happily this planet orbits about the same distance from its star as earth does from the sun.  But there are two problems.  First, Gliese 581 is a much smaller and cooler star than the sun.  So its habitable zone, where water may exist, is presumably much closer in.  Gliese 581-g still would orbit within it, but depending on the shape of its orbit it may get too hot for liquid water.

There’s a much bigger potential problem, however.  The very existence of Gliese 581-g is disputed by some astronomers.  Its discovery is somewhat clouded and controversial.  Confirmation of Gliese 581-g may take some time.

A survivor in Arches National Park overlooks a desolate valley at dusk.

A survivor in Arches National Park overlooks a desolate valley at dusk.

An exoplanet called Kepler 22-b is also interesting.  The Kepler space telescope caught it passing in front of its star on just the third day of the spacecraft’s operation.  Though 22-b is some 2.5 times bigger than Earth, its parent star is very similar to the Sun (G type).  Also, 22-b orbits at an average distance very similar to Earth’s, and so its year is similar to ours.  The only problem with Kepler 22-b is that we know so little about it.  For instance, we don’t know how elliptical its orbit is.  If it is highly elongated (as most explanets’ orbits are) it might spend part of its year very very close to the star and part very far away.  Earth’s orbit is nearly circular.

The closest potentially habitable exoplanet to us is Tau Ceti-e, only 12 light years away.  That is still much too far for us to visit in anything close to a human lifetime, so we need to temper our enthusiasm.  Also, Tau Ceti-e is yet another unconfirmed exoplanet.

The Milky Way Galaxy rises vertically over Canyonlands National Park.

The Milky Way Galaxy rises vertically over Canyonlands National Park as Venus sets.

Are We on the Right Track?

You might be questioning the importance of looking for exoplanets that are earth-like, orbiting sun-like stars at earth-like distances.  You might wonder why we don’t also look for life forms that aren’t anything like ours, life that perhaps does not rely on water or based on carbon.  Also you might notice that we always speak of planets.  We know from the search for life within our own solar system that the moons around planets are in some cases better candidates for life than are the planets themselves.  Finally, life in the cosmos may in some cases be decoupled from planets or moons, living instead in space, perhaps close to large energy sources (such as quasars).

You’re right to question.  Definite biases exist in the search for extraterrestrial life.  To some extent they are unavoidable.  But consider two facts: First, it is easiest to look for earth-like planets and life.  And this is not an easy enterprise to begin with.  Second, our sort of life is all that we know for certain can exist.  Again, it is hard enough to look for our type of life trillions of miles away let alone other types.  These sound like excuses for our bias, but there it is.

And so the hunt continues for exoplanets that are candidates for earth-like life.  Based on the Kepler space telescope’s findings, astronomers estimate that perhaps as many as 20% of the sun-like stars in the our galaxy have habitable planets orbiting them.  This is a stunning estimate because it suggests that there are nearly 9 billion habitable planets in the Milky Way Galaxy.  If even a tiny percentage of these planets have developed intelligent life, then we have plenty of company in our galaxy. 

Arches National Park under the winter stars.

Arches National Park under the winter stars.

 

 

 

 

 

Life in the Universe V: The Influence of Carl Sagan   5 comments

The moon sets behind the Tetons as the Milky Way soars over Jackson Lake, Wyoming.

The moon sets behind the Tetons as the Milky Way soars over Jackson Lake, Wyoming.

I have neglected this series for far too long, I’m sorry to say.  Check out the previous posts for some background and for some of my best starscape images.  Part I discusses how science has tackled the biggest questions we ask about the Universe and how life fits into the picture.  Part II continues by touching on the idea of the universe having a consciousness, or even some sort of creator; it also discusses how quantum theory fits into things.  Part III goes into what we know thus far about life’s origins.  And Part IV highlights the incredible progress we’ve made in the exploration of our solar system, with the not always explicit goal of finding life on other planets.

The progress of this series has been generally outward, from our beloved Earth (which remains the only place we know that hosts life) and out to the solar system.  My goal (at least metaphorically) is to go out to the stars, our galaxy, then finally the larger Universe.  Then I’d like to come back to the original two-part question discussed in Part I: how did we come to be and why?  In this post however, I’m going to take a short detour and speak about a scientist who greatly influenced how we have tackled these questions.  He is Carl Sagan, an astronomer from the United States.  Now passed away, he was widely known as a popularizer of astronomy.  He influenced NASA policy along with millions of people who watched his Cosmos TV series.  He had a significant effect on me.

In Little Ruin Canyon the moon illuminates Square Tower, with Hovenweep Castle visible on the rim beyond.

In Little Ruin Canyon the moon illuminates Square Tower, with Hovenweep Castle visible on the rim beyond.

SAGAN 101

Carl Sagan Planetary Society.JPGWhile he was charismatic and very good at getting all sorts of people enthusiastic about space science, he was also a very good scientist.  Among the general public in the U.S., he was mostly known for going on the Johnny Carson Show and expounding on astronomy.  Of course everyone knew that Johnny would eventually get him to say the word “billions”.  In Sagan’s landmark TV series Cosmos and in lectures, he often referred to billions (of stars, years, miles) with a definite, purposeful emphasis on the b.  With his great voice, the b literally boomed.  Comedians of the day had a great time imitating it.

Sagan started out as a planetary scientist, studying under the great Gerard Kuiper at University of Chicago and going on to make important contributions.  For example, he put together observations from the early Venus probes to demonstrate that the reason our sister planet is an incredibly hot, dry place is that it suffers from a runaway greenhouse effect.  He was first to suggest that Jupiter’s moon Europa has an enormous subsurface ocean and that Saturn’s moon Titan is bathed in an organic-rich atmosphere and had liquid organics on its surface.  He was a key figure in several important NASA missions, including the Viking robotic mission to Mars.  He led a small team that designed humanity’s first (and 2nd & 3rd as well) message to the stars.

Carl Sagan and Frank Drake came up with the idea to send messages to the stars on the Pioneer space probes.  Pioneer 10 and 11 were launched in the early 1970s to pass close to Jupiter and Saturn and then head out of the solar system into outer space.  These space-ready plaques, these cosmic messages in a bottle, had very simple messages inscribed on them.  There was a map showing where our solar system was located, along with figures of male and female human beings waving a greeting.  Five years later, the Voyager probes (which are now passing into interstellar space) carried a much more involved package.  It included a gold-plated record of pictures plus sounds from Earth (music, frogs croaking, volcanic action, human greetings in many languages, etc.).  This time capsule was designed by a team led by Sagan.

Also, in 1974, Carl Sagan and Frank Drake sent for the first time in human history a deliberate radio message out to the stars.  Aimed at the enormous globular cluster in the constellation Hercules, it was a coded radio transmission sent from the huge Arecibo dish in Puerto Rico.  It was not approved or sponsored by NASA, and drew great criticism.  Some prominent astronomers complained that it was arrogant and stupid for Sagan to advertise our presence to potentially hostile aliens.  Sagan countered that we have been broadcasting into space for generations, though the messages which continue to be broadcast (radio programs, TV sitcoms, etc.) may not be putting humanity’s best foot forward.

Wandering around Monument Valley during a full moon is a special experience.

Wandering around Monument Valley during a full moon is a special experience.

SAGAN & ET

Carl Sagan believed deeply in both the existence of extraterrestrial intelligence and in the many benefits that contact with them would provide humanity.  Do not misunderstand, however.  He was not a believer in ancient aliens or even that UFOs were evidence that we are being visited in recent times.  He simply believed that life had not only gotten started in many many places throughout the galaxy, but that it had progressed far beyond our level in a significant number of star systems.  He believed that if we made contact with any aliens, it would be near certain that their technology and culture would be far more sophisticated than ours.

This makes perfect sense if you believe that the Drake Equation (which estimates the chances of extraterrestrial intelligence) strongly suggests there are very many instances of intelligent civilizations in our galaxy.  Sagan combined that conclusion with the Fermi Paradox.  In 1950, Enrico Fermi famously asked of his colleagues (including Edward Teller, the father of the hydrogen bomb) “where are they?”  If there are so many potentially life-friendly star systems and literally billions of years to play with, why haven’t we seen any evidence of aliens, present or past?  Sagan took these two factors, plus the fact that we are in the infancy of space exploration ourselves, and concluded that any civilizations which do exist have somehow avoided having destroyed themselves, and are thus greatly advanced both technologically and culturally.

The Lamar River Valley in Yellowstone National Park is a peaceful place at dusk.

The Lamar River Valley in Yellowstone National Park is a peaceful place at dusk.

He had faith that we would eventually make contact with an advanced intelligence.  He also believed that their success in handling increasingly sophisticated, potentially destructive technology meant that they would be peaceful and non-aggressive.  Further, he thought they could teach us how to avoid destroying ourselves through technology, wars or ecological collapse, and that this would be the greatest discovery in the history of humanity.  This is why in the latter part of his career he focused intensively on making contact with extraterrestrial intelligence, and on convincing the general public that this was a worthwhile endeavor.

Some criticized this belief as not only quasi-religious, but as out-of-date and quasi-colonial.  They thought Sagan’s beliefs smacked of the justification for imperial powers of the west conquering primitive peoples in order to provide them with the benefits of the modern world (all the while stealing their resources and infecting them with disease).  In this cosmic case, those backward beings would be us Earthlings, and the “benevolent” conquerors would be extraterrestrials.  Many people who think about this stuff believe that contact with aliens would bring a similar fate:  exotic disease, theft of the Earth’s resources, and similar bad outcomes.  I think this criticism of Sagan is unfair.

A full moon illuminates Ship Rock in New Mexico.

A full moon illuminates Ship Rock in New Mexico.

SAGAN & SETI

The movie Contact is based on Sagan’s book of the same name, where SETI’s Jill Tarter (played by Jodi Foster) makes first contact with aliens.  SETI (Search for Extraterrestrial Intelligence), the effort that Frank Drake, Guiseppe Cocconi and Philip Morrison started is now a very mature organization.  Basically an effort to detect alien transmissions, SETI was kept alive during the 1960s by the Russians.  Carl Sagan, during the Cold War, collaborated with the Russians on SETI.  Now an American organization run by Seth Shostak, with both Frank Drake and Jill Tarter still involved, SETI is carried out by an international cast of scientists.  They conduct highly sophisticated monitoring of our galactic neighborhood.  Still looking primarily for alien radio transmissions, SETI incorporates sophisticated computer-assisted arrays of telescopes and also looks for optical signals (such as messages carried on laser beams).

SAGAN & MARS

Carl Sagan has been criticized for his almost religious zeal and optimism surrounding the existence of life on other planets.  He was very adamant that cameras on the Viking Lander be capable of sweeping the area in case any intelligent creatures show up to check out the intruder.  He endorsed a theory by the Russian Iosof Shklovsky which proposed that Phobos and Deimos (the two small moons of Mars) were artificial satellites created by Martians to escape a deteriorating climate on the planet’s surface.  Regarding the controversial “face” on Mars, Sagan parted ways with mainstream astronomers when he supported further study of it.  But he believed it was probably natural, a fact that was confirmed during subsequent flybys.

Sagan has been likened to that controversial icon of early 20th century Mars exploration, Percival Lowell.  Lowell was the dogmatic scientist who was convinced up to his death that Mars was laced with canals.  Sagan criticized Lowell for his refusal to accept evidence against the canal theory, but it is said secretly admired him for his belief in intelligent Martians.  Lowell was a tireless promoter of the theory for an advanced Martian society and, at least in part, so was Carl Sagan.  I think it’s a stretch, however, to label Sagan as Percival Lowell’s successor.

The full moon as viewed through a translucent veil formed by geothermal steam at Firehole Lake in Yellowstone National Park.

The full moon as viewed through a translucent veil formed by geothermal steam at Firehole Lake in Yellowstone National Park.

SAGAN THE SCIENTIST & AUTHOR

While it’s true that Carl Sagan had a strong belief in alien intelligence, possibly nearby, I regard him as a very good scientist, a straight thinker who could never ignore evidence that contradicted his beliefs.  He famously said “Extraordinary claims require extraordinary evidence.”  Although he though the study of UFOs was a legitimate effort, he debunked the famous alien abduction of d considered the chances of alien visitation to be extremely small.  For years he taught a course at Cornell on critical thinking.  But there’s no getting around the fact that Sagan’s interest in astronomy was stoked at an early age by the science fiction of H.G. Wells and Edgar Rice Burroughs.

Sagan was a well-trained astronomer who had a huge diversity of scientific interest and knowledge.  I have read quite a few of his books, and they are diverse.  Cosmos, The Pale Blue Dot, Cosmic Connection, Comet and Intelligent Life in the Universe are all great astronomy reads.  But he also wrote The Dragons of Eden, which explores the evolution of human intelligence.  Shadows of Forgotten Ancestors, about human evolution, is a fascinating book.  He worked for some years with famous biologists and geneticists, including Harold Urey and H.J. Muller.  He also worked with famous physicist George Gamow.  In a book called Demon-Haunted World, he defends science as a way to counter the chaos and misery of totalitarianism and war, along with ignorance.

The starry sky on a clear evening is reflected in the aptly-named Reflection Lakes at Mount Rainier National Park in Washington.

The starry sky on a clear evening is reflected in the aptly-named Reflection Lakes at Mount Rainier National Park in Washington.

SAGAN & FAITH

Sagan claimed that he was agnostic.  Based on some of his statements (“The idea that God is an oversized white male with a flowing white beard is ludicrous.”) many considered him an atheist.  But others thought he brought a religious bias into his science.  He believed that “Not only is Science compatible with pirituality, it is a profound source of spirituality.”   I believe he was somebody who welcomed that soaring elation that comes with scientific discovery, and that he regarded this as a deep spiritual experience with the nature of the universe, a sort of God.  I don’t think he was an atheist.  In fact, he once said:

An atheist is someone who is certain that God does not exist, someone who has compelling evidence against the existence of God. I know of no such compelling evidence. Because God can be relegated to remote times and places and to ultimate causes, we would have to know a great deal more about the universe than we do now to be sure that no such God exists. To be certain of the existence of God and to be certain of the nonexistence of God seem to me to be the confident extremes in a subject so riddled with doubt and uncertainty as to inspire very little confidence indeed.

In eastern Washington state stands a replica of Stonehenge, here viewed just before complete darkness descends with the stars coming out.

In eastern Washington state stands a replica of Stonehenge, here viewed just before complete darkness descends with the stars coming out.

Sagan was in some ways a child of the 1960s.  He was strictly anti-war, a staunch environmentalist, a believer in a woman’s right to equality and access to birth control (including abortion).   He smoked marijuana, and did little to hide the fact.  He married three very talented, intelligent and strong women throughout his life.  I believe Sagan’s most important legacy is what he did to make astronomy (and science in general) understandable and exciting to the public.  Sagan really believed science was a spiritual quest, but not in the strictly religious sense in which the word spirituality is often used.  Many people think his belief in extraterrestrial intelligence had strong religious elements.  But I think that he simply wasn’t conflicted about his science, and that he really was agnostic.  I believe that many of his critics mistook his spiritual-like enthusiasm (especially evident when he talked to the public about science) for some sort of religiosity.

Carl Sagan died in 1996 from pneumonia (of all things).  It was related to a disease he had called MDS, a condition that destroys a person’s bone marrow.   He was only 62, with plenty more to contribute to science and society.  Among many scientists and science enthusiasts, and nearly all science educators, he is sorely missed.  The movie Contact, an adaptation of his novel, came out in 1998.  If we do make contact with intelligent aliens within what would have been his natural lifetime (to the late 2020s, say), it will be a true shame he did not live to see it.

An old abandoned schoolhouse out on the Oregon prairie is illuminated by a crescent moon.  The Milky Way glows pink in the coming dawn.

An old abandoned schoolhouse out on the Oregon prairie is illuminated by a crescent moon. The Milky Way glows pink in the coming dawn.

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