Beyond “Fermi’s Paradox” III: What is the Great Filter?

In 1950, Italian-American physicist Enrico Fermi sat down to lunch with some of his colleagues at the Los Alamos National Laboratory, where he had worked five years prior as part of the Manhattan Project. According to various accounts, the conversation turned to aliens and the recent spate of UFOs. Into this, Fermi issued a statement that would go down in the annals of history: “Where is everybody?

This became the basis of the Fermi Paradox, which refers to the high probability estimates for the existence of extraterrestrial intelligence (ETI) and the apparent lack of evidence. Seventy years later, we still haven’t answered that question, which has led to many theories as to why the “Great Silence” endures. A popular one is that there must be “Great Filter” that prevents life from reaching an advanced stage of development.

Continue reading “Beyond “Fermi’s Paradox” III: What is the Great Filter?”

Could There Be Life in the Cloudtops of Venus?

In the search for life beyond Earth, scientists have turned up some very interesting possibilities and clues. On Mars, there are currently eight functioning robotic missions on the surface of or in orbit investigating the possibility of past (and possibly present) microbial life. Multiple missions are also being planned to explore moons like Titan, Europa, and Enceladus for signs of methanogenic or extreme life.

But what about Earth’s closest neighboring planet, Venus? While conditions on its surface are far too hostile for life as we know it there are those who think it could exist in its atmosphere. In a new study, a team of international researchers addressed the possibility that microbial life could be found in Venus’ cloud tops. This study could answer an enduring mystery about Venus’ atmosphere and lead to future missions to Earth’s “Sister Planet”.

The study, titled “Venus’ Spectral Signatures and the Potential for Life in the Clouds“, recently appeared in the journal Astrobiology. The study was led by Sanjay Limaye of the University of Wisconsin-Madison’s Space Science and Engineering Center and included members from NASA’s Ames Research Center, NASA’s Jet Propulsion Laboratory, California State Polytechnic University, the Birbal Sahni Institute of Palaeosciences, and the University of Zielona Góra.

Artist’s impression of the surface of Venus, showing its lightning storms and a volcano in the distance. Credit and ©: European Space Agency/J. Whatmore

For the sake of their study, the team considered the presence of UV contrasts in Venus’ upper atmosphere. These dark patches have been a mystery since they were first observered nearly a century ago by ground-based telescopes.  Since then, scientists have learned that they are made up of concentrated sulfuric acid and other unknown light-absorbing particles, which the team argues could be microbial life.

As Limaye indicated in a recent University of Wisconsin-Madison press statement:

“Venus shows some episodic dark, sulfuric rich patches, with contrasts up to 30 – 40 percent in the ultraviolet, and muted in longer wavelengths. These patches persist for days, changing their shape and contrasts continuously and appear to be scale dependent.”

To illustrate the possibility that these streaks are the result of microbial life, the team considered whether or not extreme bacteria could survive in Venus’ cloud tops. For instance, the lower cloud tops of Venus (47.5 to 50.5 km above the surface) are known to have moderate temperature conditions (~60 °C; 140 °F) and pressure conditions that are similar to that of Earth at sea level (101.325 kPa).

This is far more hospitable than conditions on the surface, where temperatures reach 737 K (462 C; 860 F) and atmospheric pressure is 9200 kPa (92 times that of Earth at sea level). In addition, they considered how on Earth, bacteria has been found at altitudes as high as 41 km (25 mi). On top of that, there are many cases where extreme bacteria here on Earth that could survive in an acidic environment.

A composite image of the planet Venus as seen by the Japanese probe Akatsuki. The clouds of Venus could have environmental conditions conducive to microbial life. Credit: JAXA/Institute of Space and Astronautical Science

As Rakesh Mogul, a professor of biological chemistry at California State Polytechnic University and a co-author on the study, indicated, “On Earth, we know that life can thrive in very acidic conditions, can feed on carbon dioxide, and produce sulfuric acid.” This is consistent with the presence of micron-sized sulfuric acid aerosols in Venus upper atmosphere, which could be a metabolic by-product.

In addition, the team also noted that according to some models, Venus had a habitable climate with liquid water on its surface for as long as two billion years – which is much longer than what is believed to have occurred on Mars. In short, they speculate that life could have evolved on the surface of Venus and been swept up into the atmosphere, where it survived as the planet experienced its runaway greenhouse effect.

This study expands on a proposal originally made by Harold Morowitz and famed astronomer Carl Sagan in 1967 and which was investigated by a series of probes sent to Venus between 1962 and 1978. While these missions indicated that surface conditions on Venus ruled out the possibility of life, they also noted that conditions in the lower and middle portions of Venus’ atmosphere – 40 to 60 km (25 – 27 mi) altitude – did not preclude the possibility of microbial life.

For years, Limaye has been revisiting the idea of exploring Venus’ atmosphere for signs of life. The inspiration came in part from a chance meeting at a teachers workshop with Grzegorz Slowik – from the University of Zielona Góra in Poland and a co-author on the study – who told him of how bacteria on Earth have light-absorbing properties similar to the particles that make up the dark patches observed in Venus’ clouds.

Aircraft like the Venus Atmospheric Maneuverable Platform (VAMP) could explore the cloud tops of Venus for possible signs of life. Credit: Northrop Grumman Corp

While no probe that has sampled Venus’ atmosphere has been capable of distinguishing between organic and inorganic particles, the ones that make up Venus’ dark patches do have comparable dimensions to some bacteria on Earth. According to Limaye and Mogul, these patches could therefore be similar to algae blooms on Earth, consisting of bacteria that metabolizes the carbon dioxide in Venus’ atmosphere and produces sulfuric acid aerosols.

In the coming years, Venus’ atmosphere could be explored for signs of microbial life by a lighter than air aircraft. One possibility is the Venus Aerial Mobil Platform (VAMP), a concept currently being researched by Northrop Grumman (shown above). Much like lighter-than-air concepts being developed to explore Titan, this vehicle would float and fly around in Venus’ atmosphere and search the cloud tops for biosignatures.

Another possibility is NASA’s possible participation in the Russian Venera-D mission, which is currently scheduled to explore Venus during the late 2020s. This mission would consist of a Russian orbiter and lander to explore Venus’ atmosphere and surface while NASA would contribute a surface station and maneuverable aerial platform.

Another mystery that such a mission could explore, which has a direct bearing on whether or not life may still exist on Venus, is when Venus’ liquid water evaporated. In the last billion years or so, the extensive lava flows that cover the surface have either destroyed or covered up evidence of the planet’s early history. By sampling Venus’ clouds, scientists could determine when all of the planet’s liquid water disappeared, triggering the runaway greenhouse effect that turned it into a hellish landscape.

NASA is currently investigating other concepts to explore Venus’ hostile surface and atmosphere, including an analog robot and a lander that would use a Sterling engine to turn Venus’ atmosphere into a source of power. And with enough time and resources, we might even begin contemplating building floating cities in Venus atmosphere, complete with research facilities.

Further Reading: Space Science and Engineering Center, Astrobiology

New Horizons Just Took a Record Breaking Image. No Camera Has Ever Taken a Picture From This Far From Earth

In July of 2015, the New Horizons mission made history by being the first spacecraft to rendezvous with Pluto. In the course of conducting its flyby, the probe gathered volumes of data about Pluto’s surface, composition, atmosphere and system of moons. It also provided breathtaking images of Pluto’s “heart”, its frozen plains, mountain chains, and it’s mysterious “bladed terrain”.

Since that time, New Horizons has carried on to the Kuiper Belt for the sake of conducting more historic encounters. In preparation for these, the probe also established new records when it used its Long Range Reconnaissance Imager (LORRI) to take a series of long-distance pictures. These images, which have since been released to the public, have set the new record for the most distant images ever taken.

At present, the New Horizons probe is at a distance of 6.12 billion km (3.79 billion mi) from Earth. This means that images taken at this point are at a distance of 40.9 Astronomical Units (AUs), or the equivalent of about 41 times the distance between Earth and the Sun. This it slightly farther than the “Pale Blue Dot” image of Earth, which was snapped by the Voyager 1 mission when it was at a distance of 6.06 billion km (3.75 billion mi; 40.5 AU) from Earth.

Image of the “Wishing Well” star cluster, taken Dec. 5, 2017, which temporarily broke the 27-year record set by Voyager 1. Credit: NASA/JHUAPL/SwRI

This historic picture was taken on February 14th, 1990 (Valentine’s Day) at the behest of famed astronomer Carl Sagan. At the time, Sagan was a member of the Voyager imaging team, and he recommended that Voyager 1 take the opportunity to look back at Earth one more time before making its way to the very edge of the Solar System. For more than 27 years, this long-distance record remained unchallenged.

However, in December of 2017, the New Horizons team began conducting a routine calibration test of the LORRI instrument. This consisted of snapping pictures of the “Wishing Well” cluster (aka. the “Football Cluster” or NGC 3532), an open galactic star cluster that is located about 1321 light years from Earth in the direction of the southern constellation of Carina.

This image (shown above) was rather significant, given that this star cluster was the first target ever observed by the Hubble Space Telescope (on May 20th, 1990). While this image broke the long-distance record established by Voyager 1, the probe then turned its LORRI instrument towards objects in its flight path. As part of the probes mission to rendezvous with a KBO, the team was searching for forward-scattering rings or dust.

As a result, just two hours after it had taken the record-breaking image of the “Wishing Well” star cluster, the probe snapped pictures of the Kuiper Belt Objects (KBOs) known as 2012 HZ84 and 2012 HE85 (seen below, left and right). These images once again broke the record for being the most distant images taken from Earth (again), but also set a new record for the closest-ever images ever taken of KBOs.

False-color images of KBOs 2012 HZ84 (left) and 2012 HE85, taken by LORRI, are the farthest from Earth ever captured by a spacecraft. Credit: NASA/JHUAPL/SwRI

As Dr. Alan Stern, the Principle Investigator of the New Horizons mission at the Southwest Research Institute (SwRI), explained in a NASA press release:

“New Horizons has long been a mission of firsts — first to explore Pluto, first to explore the Kuiper Belt, fastest spacecraft ever launched. And now, we’ve been able to make images farther from Earth than any spacecraft in history.”

As one of only five spacecraft to travel beyond the Outer Planets, New Horizons has set a number of other distance records as well. These include the most-distant course-correction maneuver, which took place on Dec. 9th, 2017, and guided the spacecraft towards its planned flyby with the KBO 2014 MU69. This event, which will happen on Jan. 1st, 2019, will be the farthest planetary encounter in history.

In the course of its extended mission in the Kuiper Belt, the New Horizons team seeks to observe at least two-dozen other KBOs, dwarf planets and “Centaurs” – i.e. former KBOs that have unstable orbits that cause them to cross the orbit of the gas giants. At present, the New Horizons spacecraft is in hibernation and will be brought back online on June 4th, – when it will begin a series of checks to make sure it is ready for its planned encounter with MU69.

The spacecraft is also conducting nearly continuous measurements of the Kuiper Belt itself to learn more about its plasma, dust and neutral-gas environment. These efforts could reveal much about the formation and evolution of the Solar System, and are setting records that are not likely to be broken for many more decades!

Further Reading: NASA

Carl Sagan’s Crazy Idea: Life Inside A Comet?

Establishing a sustained human presence somewhere other than Earth is a vital part of humanity’s future, no matter what. We know that Earth won’t last forever. We don’t know exactly which one of the many threats that Earth faces will ultimately extinguish life here, but life will be extinguished completely at some future point.

Colonizing moons or planets is one way to do it. But that’s really hard. We may make it to Mars before too long, but we don’t know how successful we’ll be at establishing a presence there. There are an awful lot of ‘ifs’ when it comes to Mars.

The only other option is space habitats. That makes sense; there’s much more space out there than there is surface area on planets and moons. And space habitats have been on the minds of thinkers, writers, and scientists for a long time.

Gerard K. O’Neill is probably the most well-known thinker when it comes to space habitats. In 1977 he published the seminal book on space habitats, called “The High Frontier: Human Colonies in Space.” O’Neill in his time popularized what is now called the “O’Neill Cylinder.”

The O’Neill Cylinder

Interior view of an O'Neill Cylinder. There are alternating strips of livable surface and "windows" to let light in. Image: Rick Guidice, NASA Ames Research Center
Interior view of an O’Neill Cylinder. There are alternating strips of livable surface and “windows” to let light in. Image: Rick Guidice, NASA Ames Research Center

The O’Neill Cylinder lay the groundwork for space habitat design. It consisted of two counter-rotating cylinders, one nested inside the other. The counter-rotation provided stability and gravity. The atmosphere would be controlled, and the habitat would be powered by solar, and perhaps fusion.

An illustration of two O'Neill Cylinder's. Image: Rick Guidice NASA Ames Research Center
An illustration of two O’Neill Cylinder’s. Image: Rick Guidice NASA Ames Research Center

The McKendree Cylinder

Other designs from other people followed O’Neill’s. Notable among them is the McKendree Cylinder. The McKendree would be gargantuan compared to the O’Neill Cylinder. Thanks to carbon nanotubes, it would have more surface area than the United States. It was designed by NASA Engineer Tom McKendree and introduced in the year 2,000 at the NASA “Turning Goals into Reality Conference.”

There’ve been other ideas for massive, high-tech space habitats, including the Bernal Sphere and the Stanford Torus. All of these designs are typical of engineers and technologists. Lots of high-tech, lots of steel, lots of machinery. But the engineers and scientists behind those designs weren’t the only ones thinking about humans in space.

Carl Sagan was too. And he had a very different idea of what space habitats could be.

So Crazy It Just Might Work

But the craziest idea for space habitats has got to be Carl Sagan’s, from his 1985 book “Comet.”In “Comet” Sagan suggested that humans could seek refuge in, and even colonize, actual comets travelling through our Solar System. Using all the advanced technologies thought about in Sagan’s time—but which don’t exist yet—comets could be transformed into humanity’s salvation. His idea is a world apart from the high-tech, highly-engineered, gleaming habitat designs that most people think of when they think of space habitats.

I’m a fan of Sagan’s. Like many in my generation, I was influenced by his TV series Cosmos. I loved it and it’s stuck with me. His book “The Demon-Haunted World” taught us what scientific skepticism can be, and how useful it is.

"Comet" was published only months before Halley's Comet arrived in our inner Solar System in 1986. Image: Jon Lomberg, Random House New York.
“Comet” was published only months before Halley’s Comet arrived in our inner Solar System in 1986. Image: Jon Lomberg, Random House New York.

Sagan’s is the most surprising—and perhaps bleakest—view of space habitats. Life inside comets sounds shocking, and maybe even foolish, but as Sagan explains, there is some reasoning behind the idea.

Remember that when Sagan wrote about this, thermonuclear war between the superpowers was a “thing,” and thinkers like Sagan felt a sense of imminent danger. That sense of foreboding may have contributed to his “comets-as-space-habitas” idea. Plus, he was just an innovative thinker.

Carl Sagan in 1980.
Carl Sagan in 1980.

Sagan’s thinking behind using comets as space habitats starts out something like this: if there are about a hundred thousand comets crossing Earth’s orbit, and another hundred trillion in the Oort Cloud, their combined surface area is roughly equal to about a hundred million Earths. And with advanced technology, Sagan proposed that these comets could be captured and colonized and sent on orbits and trajectories desirable to humans.

Comet Lovejoy and its spectacular "lively" ion tail photographed on January 8th by Nick Howes at Tzec Muan Network at Siding Spring Australia. Could Lovejoy and its brethren one day provide a home for humanity?
Comet Lovejoy and its spectacular “lively” ion tail photographed on January 8th by Nick Howes at Tzec Muan Network at Siding Spring Australia. Could Lovejoy and its brethren one day provide a home for humanity?

Comets are rich in minerals, water ice, and biological compounds. Or so it was thought at the time. That means raw material for manufacturing, water to drink and to supply oxygen, biological compounds for bio-engineering, and even the raw material for rocket fuel. Add a fusion reactor for power, and
comets could end up being the convenience stores of the Solar System.

Physicist Freeman Dyson, an innovative thinker himself, had something to add to Sagan’s comet idea. In “Comet,” Sagan tells of Dyson’s ideas around genetic engineering, and that one day we should be able to engineer forms of life that could thrive on comets, and meet some of our needs. Dyson talks about a giant, genetically engineered tree that could grow on a comet, planted in snow rich in organic chemicals. The tree would supply us with fresh oxygen.

The OSIRIS narrow-angle camera aboard the Rosetta spacecraft captured this image of comet 67P/Churyumov-Gerasimenko on September 30, 2016. Does it look habitable, or potentially habitable, to you? Credits: ESA/Rosetta/MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
The OSIRIS narrow-angle camera aboard the Rosetta spacecraft captured this image of comet 67P/Churyumov-Gerasimenko on September 30, 2016. Does it look habitable, or potentially habitable, to you? Credits: ESA/Rosetta/MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

This sounds extremely far-fetched: humans living inside comets travelling through space, with giant genetically engineered trees and fusion power plants. I try to remind myself that many things we take for granted now were once thought to be laughable. But even though parts of the comet-as-space-habitat idea sound fanciful—like the giant tree—there may be the seed of a practical idea here, with humans hitching rides on comets, molding them to our purposes, and extracting resources like minerals and fuel from them.

High cliffs on the surface of Comet Churyumov–Gerasimenko as imaged by the Rosetta spacecraft. Image Credit & Licence (CC BY-SA 3.0 IGO): ESA, Rosetta spacecraft, NAVCAM; Additional Processing: Stuart Atkinson
High cliffs on the surface of Comet Churyumov–Gerasimenko as imaged by the Rosetta spacecraft. Image Credit & Licence (CC BY-SA 3.0 IGO): ESA, Rosetta spacecraft, NAVCAM; Additional Processing: Stuart Atkinson

Sagan was an agile creative thinker. He’s clearly riffing when he outlines his ideas for life on comets. He’s like the John Coltrane of space science.

It seems doubtful that we would go to the trouble to turn comets into actual habitats. It’s probably more science fiction that science. But the future is unwritten, and given enough time, almost anything might be possible.

Where Are All The Alien Robots?

If you’ve seen at least one other episode of the Guide to Space, you know I’m obsessed about the Fermi Paradox. This idea that the Universe is big and old, and should be teeming with life. And yet, we have no evidence that it exists out there. We wonder, where are all the aliens?

Ah well, maybe we’re in a cosmic zoo, or maybe the Universe is just too big, or the laws of physics prevent any kind of meaningful travel or communications. Fine. I doubt it, but fine.\

Continue reading “Where Are All The Alien Robots?”

Beyond “Fermi’s Paradox” II: Questioning the Hart-Tipler Conjecture

It’s become a legend of the space age. The brilliant physicist Enrico Fermi, during a lunchtime conversation at Los Alamos National Laboratory in 1950, is supposed to have posed a conundrum for proponents of the existence of extraterrestrial civilizations.

If space traveling aliens exist, so the argument goes, they would spread through the galaxy, colonizing every habitable world. They should then have colonized Earth. They should be here, but because they aren’t, they must not exist.

This is the argument that has come to be known as “Fermi’s paradox”. The problem is, as we saw in the first installment, Fermi never made it. As his surviving lunch companions recall (Fermi himself died of cancer just four years later, and never published anything on the topic of extraterrestrial intelligence), he simply raised a question, “Where is everybody?” to which there are many possible answers.

Continue reading “Beyond “Fermi’s Paradox” II: Questioning the Hart-Tipler Conjecture”

25 Years Since Voyager’s ‘Pale Blue Dot’ Images

A quarter of a century has passed since NASA’s Voyager 1 spacecraft snapped the iconic image of Earth known as the “Pale Blue Dot” that shows all of humanity as merely a tiny point of light.

The outward bound Voyager 1 space probe took the ‘pale blue dot’ image of Earth 25 years ago on Valentine’s Day, on Feb. 14, 1990 when it looked back from its unique perch beyond the orbit of Neptune to capture the first ever “portrait” of the solar system from its outer realms.

Voyager 1 was 4 billion miles from Earth, 40 astronomical units (AU) from the sun and about 32 degrees above the ecliptic at that moment.

The idea for the images came from the world famous astronomer Carl Sagan, who was a member of the Voyager imaging team at the time.

He head the idea of pointing the spacecraft back toward its home for a last look as a way to inspire humanity. And to do so before the imaging system was shut down permanently thereafter to repurpose the computer controlling it, save on energy consumption and extend the probes lifetime, because it was so far away from any celestial objects.

Sagan later published a well known and regarded book in 1994 titled “Pale Blue Dot,” that refers to the image of Earth in Voyagers series.

This narrow-angle color image of the Earth, dubbed "Pale Blue Dot," is a part of the first ever "portrait" of the solar system taken by Voyager 1 on Valentine’s Day on Feb. 14, 1990.  Credit: NASA/JPL-Caltech
This narrow-angle color image of the Earth, dubbed “Pale Blue Dot,” is a part of the first ever “portrait” of the solar system taken by Voyager 1 on Valentine’s Day on Feb. 14, 1990. Credit: NASA/JPL-Caltech

“Twenty-five years ago, Voyager 1 looked back toward Earth and saw a ‘pale blue dot,’ ” an image that continues to inspire wonderment about the spot we call home,” said Ed Stone, project scientist for the Voyager mission, based at the California Institute of Technology, Pasadena, in a statement.

Six of the Solar System’s nine known planets at the time were imaged, including Venus, Earth, Jupiter, and Saturn, Uranus, Neptune. The other three didn’t make it in. Mercury was too close to the sun, Mars had too little sunlight and little Pluto was too dim.

Voyager snapped a series of images with its wide angle and narrow angle cameras. Altogether 60 images from the wide angle camera were compiled into the first “solar system mosaic.”

Voyager 1 was launched in 1977 from Cape Canaveral Air Force Station in Florida as part of a twin probe series with Voyager 2. They successfully conducted up close flyby observations of the gas giant outer planets including Jupiter, Saturn, Uranus and Neptune in the 1970s and 1980s.

Both probes still operate today as part of the Voyager Interstellar Mission.

“After taking these images in 1990, we began our interstellar mission. We had no idea how long the spacecraft would last,” Stone said.

Hurtling along at a distance of 130 astronomical units from the sun, Voyager 1 is the farthest human-made object from Earth.

Solar System Portrait - 60 Frame Mosaic. The cameras of Voyager 1 on Feb. 14, 1990, pointed back toward the sun and took a series of pictures of the sun and the planets, making the first ever "portrait" of our solar system as seen from the outside.   Missing are Mercury, Mars and Pluto Credit:  NASA/JPL-Caltech
Solar System Portrait – 60 Frame Mosaic. The cameras of Voyager 1 on Feb. 14, 1990, pointed back toward the sun and took a series of pictures of the sun and the planets, making the first ever “portrait” of our solar system as seen from the outside. Missing are Mercury, Mars and Pluto. Credit: NASA/JPL-Caltech

Voyager 1 still operates today as the first human made instrument to reach interstellar space and continues to forge new frontiers outwards to the unexplored cosmos where no human or robotic emissary as gone before.

Here’s what Sagan wrote in his “Pale Blue Dot” book:

“That’s here. That’s home. That’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. … There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world.”

Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news.

Ken Kremer

What Does It Mean To Be ‘Star Stuff’?

At one time or another, all science enthusiasts have heard the late Carl Sagan’s infamous words: “We are made of star stuff.” But what does that mean exactly? How could colossal balls of plasma, greedily burning away their nuclear fuel in faraway time and space, play any part in spawning the vast complexity of our Earthly world? How is it that “the nitrogen in our DNA, the calcium in our teeth, the iron in our blood, the carbon in our apple pies” could have been forged so offhandedly deep in the hearts of these massive stellar giants?

Unsurprisingly, the story is both elegant and profoundly awe-inspiring.

All stars come from humble beginnings: namely, a gigantic, rotating clump of gas and dust. Gravity drives the cloud to condense as it spins, swirling into an ever more tightly packed sphere of material. Eventually, the star-to-be becomes so dense and hot that molecules of hydrogen in its core collide and fuse into new molecules of helium. These nuclear reactions release powerful bursts of energy in the form of light. The gas shines brightly; a star is born.

The ultimate fate of our fledgling star depends on its mass. Smaller, lightweight stars burn though the hydrogen in their core more slowly than heavier stars, shining somewhat more dimly but living far longer lives. Over time, however, falling hydrogen levels at the center of the star cause fewer hydrogen fusion reactions; fewer hydrogen fusion reactions mean less energy, and therefore less outward pressure.

At a certain point, the star can no longer maintain the tension its core had been sustaining against the mass of its outer layers. Gravity tips the scale, and the outer layers begin to tumble inward on the core. But their collapse heats things up, increasing the core pressure and reversing the process once again. A new hydrogen burning shell is created just outside the core, reestablishing a buffer against the gravity of the star’s surface layers.

While the core continues conducting lower-energy helium fusion reactions, the force of the new hydrogen burning shell pushes on the star’s exterior, causing the outer layers to swell more and more. The star expands and cools into a red giant. Its outer layers will ultimately escape the pull of gravity altogether, floating off into space and leaving behind a small, dead core – a white dwarf.

Lower-mass stars like our sun eventually enter a swollen, red giant phase. Ultimately, its outer layers will be thrown off altogether, leaving nothing but a small white dwarf star. Image Credit: ESO/S. Steinhofel
Lower-mass stars like our sun eventually enter a swollen, red giant phase. Ultimately, its outer layers will be thrown off altogether, leaving nothing but a small white dwarf star. Image Credit: ESO/S. Steinhofel

Heavier stars also occasionally falter in the fight between pressure and gravity, creating new shells of atoms to fuse in the process; however, unlike smaller stars, their excess mass allows them to keep forming these layers. The result is a series of concentric spheres, each shell containing heavier elements than the one surrounding it. Hydrogen in the core gives rise to helium. Helium atoms fuse together to form carbon. Carbon combines with helium to create oxygen, which fuses into neon, then magnesium, then silicon… all the way across the periodic table to iron, where the chain ends. Such massive stars act like a furnace, driving these reactions by way of sheer available energy.

But this energy is a finite resource. Once the star’s core becomes a solid ball of iron, it can no longer fuse elements to create energy. As was the case for smaller stars, fewer energetic reactions in the core of heavyweight stars mean less outward pressure against the force of gravity. The outer layers of the star will then begin to collapse, hastening the pace of heavy element fusion and further reducing the amount of energy available to hold up those outer layers. Density increases exponentially in the shrinking core, jamming together protons and electrons so tightly that it becomes an entirely new entity: a neutron star.

At this point, the core cannot get any denser. The star’s massive outer shells – still tumbling inward and still chock-full of volatile elements – no longer have anywhere to go. They slam into the core like a speeding oil rig crashing into a brick wall, and erupt into a monstrous explosion: a supernova. The extraordinary energies generated during this blast finally allow the fusion of elements even heavier than iron, from cobalt all the way to uranium.

Periodic Table of Elements
Periodic Table of Elements. Massive stars can fuse elements up to Iron (Fe), atomic number 26. Elements with atomic numbers 27 through 92 are produced in the aftermath of a massive star’s core collapse.

The energetic shock wave produced by the supernova moves out into the cosmos, disbursing heavy elements in its wake. These atoms can later be incorporated into planetary systems like our own. Given the right conditions – for instance, an appropriately stable star and a position within its Habitable Zone – these elements provide the building blocks for complex life.

Today, our everyday lives are made possible by these very atoms, forged long ago in the life and death throes of massive stars. Our ability to do anything at all – wake up from a deep sleep, enjoy a delicious meal, drive a car, write a sentence, add and subtract, solve a problem, call a friend, laugh, cry, sing, dance, run, jump, and play – is governed mostly by the behavior of tiny chains of hydrogen combined with heavier elements like carbon, nitrogen, oxygen, and phosphorus.

Other heavy elements are present in smaller quantities in the body, but are nonetheless just as vital to proper functioning. For instance, calcium, fluorine, magnesium, and silicon work alongside phosphorus to strengthen and grow our bones and teeth; ionized sodium, potassium, and chlorine play a vital role in maintaining the body’s fluid balance and electrical activity; and iron comprises the key portion of hemoglobin, the protein that equips our red blood cells with the ability to deliver the oxygen we inhale to the rest of our body.

So, the next time you are having a bad day, try this: close your eyes, take a deep breath, and contemplate the chain of events that connects your body and mind to a place billions of lightyears away, deep in the distant reaches of space and time. Recall that massive stars, many times larger than our sun, spent millions of years turning energy into matter, creating the atoms that make up every part of you, the Earth, and everyone you have ever known and loved.

We human beings are so small; and yet, the delicate dance of molecules made from this star stuff gives rise to a biology that enables us to ponder our wider Universe and how we came to exist at all. Carl Sagan himself explained it best: “Some part of our being knows this is where we came from. We long to return; and we can, because the cosmos is also within us. We’re made of star stuff. We are a way for the cosmos to know itself.”

Bill Nye on Taking Astronomy with Carl Sagan

“This is how we know nature. It is the best idea humans have ever come up with.”
– Bill Nye, Science Guy and CEO of The Planetary Society

In this latest video from NOVA’s Secret Life of Scientists and Engineers, science guy Bill Nye talks about the incredible influence that Carl Sagan had on his life, from attending his lectures on astronomy at Cornell University to eventually becoming CEO of The Planetary Society, which was co-founded by Sagan in 1980.

“I took astronomy from Carl Sagan.” Now there’s a statement that’ll get people’s attention. (It got mine, anyway.)

See more videos in NOVA’s Secret Life series here.

‘Cosmos’ Reboot Starts With a (Big) Bang

With much anticipation from the astronomy and science community, the opening episode of the new and updated version of Carl Sagan’s “Cosmos” series premiered to the masses on television in North America last night. This reboot – this time hosted by astrophysicist Neil de Grasse Tyson — did a wonderful job of paying homage to Sagan while showcasing the grandeur of space, as well as portraying the infinitesimally small amount of time that humanity has existed. Like its original counterpart, the first episode of the series takes viewers on a quick tour of the Solar System and Universe, showing our cosmic “address” as it were, going back to the Big Bang, but also touching on multiverses and a potentially infinite Universe.

As de Grasse Tyson said at the beginning, “from the infinitesimal to the infinite; from the dawn of time to the distant future.”

There were also – seemingly – an infinite number of commercial interruptions. You can watch the episode in its entirety below, without commercials, thankfully. Watching it on television last night was disappointing because of those commercial interruptions – sometimes only a couple of minutes apart — making one wish for the PBS-commercial-free version of the original Cosmos with Sagan.

And I wasn’t the only one feeling those sentiments:

(Yes, I watched the show while keeping an eye on what the Twitterverse had to say about it.)

But airing the series on the Fox Network and its affiliated channels (I watched it on the National Geographic Channel) was a calculated move by the series’ producer Seth MacFarlane to showcase the series and the science to a population that may not otherwise be exposed to science at this “popular” level. And clearly, science and the scientific method gets top billing in this series:

“This adventure is made possible by generations of searchers strictly adhering to a general set of rules: test ideas by experiment and observation … follow the evidence where it leads and question everything,” said Tyson.

This planetary nebula's simple, graceful appearance is thought to be due to perspective: our view from Earth looking straight into what is actually a barrel-shaped cloud of gas shrugged off by a dying central star. Hot blue gas near the energizing central star gives way to progressively cooler green and yellow gas at greater distances with the coolest red gas along the outer boundary. Credit: NASA/Hubble Heritage Team
This planetary nebula’s simple, graceful appearance is thought to be due to perspective: our view from Earth looking straight into what is actually a barrel-shaped cloud of gas shrugged off by a dying central star. Hot blue gas near the energizing central star gives way to progressively cooler green and yellow gas at greater distances with the coolest red gas along the outer boundary. Credit: NASA/Hubble Heritage Team

With a combination of real images from telescopes and spacecraft, computer generated imagery and surprisingly watchable animations, most intriguing for me was the “cosmic calendar.” Those who have seen Sagan’s original series will remember his version of the cosmic calendar as a way to conceptualize the age of the Universe, compressing 13.9 billion years down to one year. Tyson’s flashier calendar also showed how January 1 would mark the Big Bang and December 31 would be the present – making each day represent about 40 million years. At this rate, humanity’s entire recorded history only occupies just the last 14 seconds of the year.

But as Tyson noted, science has provided unmatched discoveries during that short span of time: “The scientific method is so powerful that in a mere four centuries, it has taken us from Galileo’s’ first look through the telescope to knowing our place in the Universe.”

Giordano Bruno in Cosmos. Image courtesy of Fox.
Giordano Bruno in Cosmos. Image courtesy of Fox.

When I heard there were going to be animated sequences of historical events (the original series used actor portrayals) I was disappointed, but the animations in this series premiere surprised me by being quite engaging.

They told the story of Giordano Bruno, the 16th century Italian monk turned astronomer. He had theorized that other planets existed with other lifeforms like ours. In his 1584 book “On the Infinite Universe and Worlds,” Bruno wrote : “… there is a single general space, a single vast immensity which we may freely call Void; in it are innumerable globes like this one on which we live and grow. This space we declare to be infinite… In it are an infinity of worlds of the same kind as our own.”

This was controversial for his time, but even in a church-dominated society, it wasn’t grounds for being declared a heretic. But later Bruno followed his argument to its logical conclusion: if there are an infinity of worlds, and if some worlds have sentient beings created by God, then wouldn’t these planets also need to be saved by God? The notion other Jesuses was not viewed well, and the church convicted him of heresy, and burned him at the stake.

Phil Plait talked more about this today in his review of “Cosmos” and I agree with him that this wasn’t really about showing religion in a bad light, but about making “a bigger point about suppression of thought and the grandeur of freedom of exploration of ideas.”

Other fun moments were when a CGI (but quite realistic) dinosaur fish named a Tiktaalik crawled out of the sea right next to Tyson, depicting the evolution of life on Earth. Most endearing was perhaps Tyson’s claim that “we are ALL descended from astronomers;” how our ancestors depended on the stars to know the change of seasons.

While this series premier was a quick overview, one surprise is that it showed just one theory – and the oldest and perhaps outdated — of how our Moon was formed, by a conglomeration of the same debris that make up Earth. These days it seems the theory of a Mars-sized planetary collision is the most accepted theory.

The show began and ended with the voice and words of Carl Sagan, and Tyson shared his story about his own personal interactions with Sagan. This was a very authentic part of the show, and allowed the torch to be passed from Sagan to Tyson.

And then there was Tyson using Sagan’s famous “we are made star stuff” quote:

“They get so hot that the nuclei of the atoms fuse together deep within them to make the oxygen with breathe, the carbon in our muscles, the calcium in our bones, the iron in our blood,” Tyson said. “You, me, everyone: We are made of star stuff.”

This series premiere was a rousing tribute to science and I am definitely looking forward to more. Here’s hoping this series does what MacFarlane had in mind: get the general public to start talking about science again.

If you are feeling the need for more “Cosmos” you can watch the original series at Hulu Plus, and at the Carl Sagan website, learn more about the legend.

There is “The Seth MacFarlane collection of the Carl Sagan and Ann Druyan archive, 1860-2004” at the Library of Congress. MacFarlene supported this new Carl Sagan archive.

See more at the Cosmos Online website (there’s even an app for it.)