Can Aliens Receive Our Radar Transmissions?

  

One of the most fundamental questions that we as a civilization might ask concerns the possibility that other intelligent beings may also inhabit our galaxy. On November 16, 1974, a group of scientists led by Frank Drake and Carl Sagan sent a message towards a large star cluster in the constellation of Hercules. At a distance of 13,000 light years, the message is still a long way from getting there. That event is considered the beginning of our search for other civilizations.

 

Frank Drake, credit SETI Institute.                     Carl Sagan, credit NASA Science

SETI stands for Search for Extra-Terrestrial Intelligence. The two most active organizations doing this are the SETI Institute and the Breakthrough Listen program. Both primarily use sophisticated radio telescopes to search for artificial radio signals from other planets that could support life. The thinking behind these projects is that any other intelligent civilization is likely to use radio signals for communication and detection.

The Allen Telescope Array, used by the SETI Institute.

The Very Large Array radio telescopes used by Breakthrough Listen. 

We humans use radio for these very purposes. Civil and military airport radar represents our most powerful radio signals. We’ve been using this technology since World War 2, and today’s radars are far more powerful and sophisticated. They are so powerful that they can be detected by any civilization with radio telescope technology at the same level as our SETI searches use.

Ramiro Saide, a Ph.D. student at the University of Manchester, led a research project to calculate how far away our radar facilities could be detected by civilizations at least as advanced as us. Our radio telescopes are capable of detecting a signal like what we emit from our airport radars from 200 light years away. There are more than 120,000 stars within 200 light-years of Earth. Although we currently have no evidence that any of those stars are home to intelligent aliens, we do know that they likely have some 200,000 or more planets that orbit them. Most of those aren’t capable of supporting life as we know it, but some may well be able to.

Saide said of the study that our radar signals would appear “clearly artificial to anyone watching from interstellar distances with powerful radio telescopes. These military signals can appear up to a hundred times stronger from certain points in space, depending on the observer’s location. Our findings suggest that radar signals – produced unintentionally by any planet with advanced technology and complex aviation system – could act as a universal sign of intelligent life.”

While our efforts to detect other civilizations have not yet provided any absolute proof of their existence, at least we know that our equipment could detect their radar emissions. The SETI Institute and Breakthrough Listen will continue to monitor the skies for any neighbors we might have.

 

Each month, I write an astronomy-related column piece for the Oklahoman newspaper. After it is published there, I post that same column to my blog page.

This is reprinted with permission from the Oklahoman and www.Oklahoman.com.

Making Distances in Space a Bit Easier to Imagine

 Warning to my readers: I’ll be using some big numbers in this article. Hopefully, I have made it as painless as possible.

Distances to objects in space from Earth are, well, astronomical. The Moon is 239,000 miles away. We’d have to travel 93,000,000 miles to reach the sun. That may seem like a great distance, but the next closest star, Proxima Centauri, is 22,876,214,400,000 miles away. Proxima Centauri is the closest of a three-star system known as Alpha Centauri. Using miles as a distance measure in space is quite impractical. The numbers get very big very quickly. Instead, we use light-years, the distance light travels in one year.

Artist's rendering of the Alpha Centauri three-star system. Credit NASA's Goddard Space Flight Center Conceptual Image Lab

Light travels at the fastest possible speed, moving through space at 186,000 miles per second. That’s 669,600,000 miles/hour or 5,865,696,000,000 miles/year. We call that distance, 5,865,696,000,000 miles, one light-year. Proxima Centauri is 4.25 light-years away, which is easier to write.

Let’s think about those astronomical distances in terms we can more easily visualize. Imagine one light year equals one mile. We all have a good understanding of how long a mile is. On this scale, light travels 0.002 inches per second. That’s a big change from the actual speed of light. The moon is 1.3 light seconds from Earth, or 0.0026 inches with this new light-year. We would orbit the sun, 8.3 light minutes away, from a distance of just under an inch. Proxima Centauri is 4.25 light years away, which now equates to 4.25 miles. Now it’s a lot easier to imagine these distances.

The fastest speed that any of our spacecraft has ever flown is the Parker Solar Probe. It used multiple gravity assists from Venus to get it close to the sun. It orbits so close to the sun that it passes through the sun’s outer atmosphere. In order to orbit the sun that closely, it has to move fast, achieving a maximum speed of 430,000 miles per hour. That’s really moving. But scaled to our new light speed of one mile per year, that corresponds to a mere 0.00064 miles per hour. At that speed, it would take 1,557 years to reach Proxima Centauri. Even in this shrunken universe, our Milky Way galaxy is 100,000 miles across, and our closest comparably large galactic neighbor, the Andromeda Galaxy, is still a mind-numbing 2,537,000 miles away.

As you can see, our universe is so incredibly large, even when shrunk by a factor of 5,865,696,000,000, it’s still huge beyond easy comprehension.

 

Each month, I write an astronomy-related column piece for the Oklahoman newspaper. After it is published there, I post that same column to my blog page.

This is reprinted with permission from the Oklahoman and www.Oklahoman.com.

Trees "Remember" Previous Eclipse and Warn Young Trees

 The amount of daylight we receive goes through cycles. Earth’s rotation creates day and night. Earth’s orbit around the sun, combined with its 23-degree tilt, causes our seasons, which in turn affect the amount of daylight we receive at different times of the year and, consequently, our weather patterns. Understanding these patterns was critical for early humans as they tracked animal migrations and allowed us to master agricultural practices. We developed clocks and calendars to tell us when these changes would occur.

These changes are regular and could be easily tracked and anticipated. To our early ancestors, there were unpredictable cycles that affected sunlight. Solar eclipses occur when our Moon passes between us and the sun. If you happen to be on the narrow eclipse path, you can experience a total solar eclipse. Sunlight levels will drop to a small fraction of the brightness of the normal daytime sun. Primitive cultures ascribed the loss of sunlight to a creature of some kind devouring the sun, or perhaps to some evil spirit stealing sunlight. They would make loud noises to scare off the creature or chant incantations to ward off the evil spirit.

The chances of a total eclipse occurring in a specific location are rather remote. A given location on Earth experiences a total solar eclipse only about once every 360 to 400 years, making them unpredictable. Anyone within a few hundred miles of the eclipse path will see a partial solar eclipse, but those are generally less dramatic and less cause for concern. For any given location, partial eclipses are far more common.

Biologists have studied the behavior of animals during a total solar eclipse. The rapid decrease in light level and the consequent drop in temperature cause animals to start nighttime activities. Birds start to roost. Many animals, like butterflies and bats, use sunlight for navigation and stop flying. Fireflies start flashing.

Until recently, virtually no studies existed of how plants might behave during an eclipse. We know that trees communicate via chemical methods transmitted between trees by an extensive network of underground fungi and bacteria, which biologists refer to as the “Wood Wide Web.” A group of scientists noted that an eclipse was to occur over the forests in the Dolomite Mountains in Italy on October 25, 2022.

The interdisciplinary team, consisting of researchers from Italy, the United Kingdom, Spain, and Australia, placed custom-built sensors throughout the forest. The team recorded simultaneous bioelectrical responses from the spruce trees starting a few hours before the eclipse and continuing throughout the eclipse. They found that electrical activity from individual trees became "significantly" more synchronized. Even more surprisingly, they found that the activity in older trees began earlier than in younger trees. This, the authors say, suggests the older trees hold ancient memories of past eclipses. When such an event is imminent, the old trees "remember" and inform younger trees.

A spruce tree with a recording unit attached in the Dolomite Mountains in Italy. Credit Monica Gagliano/Southern Cross University

Spruce trees do not possess a brain or a central nervous system, yet they recognized that the light would dim significantly, affecting photosynthesis, and warned the younger trees about what to expect.

 "By applying advanced analytical methods — including complexity measures and quantum field theory — we have uncovered a deeper, previously unrecognized dynamic synchronization not based on matter exchanges among trees," said Alessandro Chiolerio, Italian Institute of Technology and University of the West of England, and the study co-leader. "We now see the forest not as a mere collection of individuals, but as an orchestra of phase-correlated plants."

The next time you hear of an upcoming solar eclipse, you should have a greater appreciation of how amazing our planet is.

 Each month, I write an astronomy-related column piece for the Oklahoman newspaper. After it is published there, I post that same column to my blog page.

 This is reprinted with permission from the Oklahoman and www.Oklahoman.com.

Do "Dark Comets" Pose a Danger to Earth?

 You have probably seen pictures of comets with their long tails of dust and ice sweeping majestically behind them. That tail is one of the defining characteristics of comets. Small objects orbiting the sun that do not sprout a tail have long been considered to be asteroids. While astronomers have found some “dead” comets, those with no tail being pushed off by the sun, they have become asteroids.

As the ice melts from the comet by the sun’s heat, it pushes off the comet with a small force. Think of a pot of water evaporating. Even though you can’t feel the “wind” caused by this water vapor leaving the water, it’s there, and it pushes back on the water with a tiny but persistent force. With comets, this force of the vaporized ice leaving the comet acts like a tiny rocket motor. It can push the comet in its orbit in a way that astronomers can measure. The orbit of a comet isn’t controlled solely by the gravity of the sun, planets, and other objects in our solar system, but also due to this outgassing. Asteroids don’t behave this way.

Or so astronomers thought.

In 2016, astronomer David Farnocchia, with NASA’s Center for Near-Earth Object Studies, discovered something quite puzzling. He found an asteroid, 2003 RM, whose motion through the solar system couldn’t be fully accounted for by the gravity of other bodies. It behaved like a comet shooting water vapor into space, except that he could find no evidence of that.

There is another force, known as the Yarkovsky effect, which can alter the orbit of small bodies around the sun. As photons from the sun impact a space rock, they deliver an almost imperceptible push on the rock. Though minuscule, it can, over time, affect the rock’s orbital path. Also, the sunward side heats up from the sun’s thermal energy. But, as the asteroid rotates, the heated side rolls into the dark and radiates the excess heat into space, again providing a tiny bit of thrust. Farnocchia took all of that into account for 2003 RM, yet it still couldn’t explain the small deviation of the asteroid’s orbit.

Comet Tsuchinshan-ATLAS credit Wladimir Bulgar - Science Photo Library via Getty Images

With all comets, as the ice is vaporized and outgassed from the sun’s heat, it also releases dust trapped in the ice. That beautiful tail we see coming from a comet is actually composed of dust. But even using our biggest and best telescopes, no one has found any dust trailing 2003RM. It behaved as if it had a tiny rocket engine attached to it. Eventually, Farnocchia and other astronomers found thirteen more such objects. They dubbed them “dark comets.”

This is more than just a curiosity for astronomers. Farnocchia’s job is to search for asteroids that have a possibility of hitting Earth. “My job,” he says, “is to predict how things move in space. So if there’s something novel or unexpected, that’s where the advance in the field lies for us.”

Current telescopes can easily see any dust that might be coming off of a comet, but none has been found to date. New telescopes planned or already under construction will be able to detect any tiny bits of water vapor that may be puffing off these dark comets. And since some are close enough that they might have a chance of collision with Earth down the road, being able to predict their position and movement may become more crucial in the future. For now, he will monitor them and track their movements, just in case one wanders too close to us.  

Do Cosmic Events Cause Mass Extinctions on Earth?

 Scientists recognize five major mass extinctions in Earth’s history, episodes when a large fraction of life all over our planet went extinct in a very short time on geological time scales. Scientists blame various causes for these extinctions. Climate change was often the real killer, but the cause of climate change varied.

The most recent mass extinction, the K-T extinction 66 million years ago, is perhaps the most famous and best understood of the major extinctions. It led to the end of the dinosaurs and most marine reptiles. At that time, an asteroid 6 miles in diameter slammed into Earth just off the coast of what is now the Yucatan Peninsula in Mexico. It threw hot ash and molten rock into the air that covered the planet, resulting in worldwide fires, killing off many species. The resulting cloud of debris and smoke then reduced sunlight from reaching the planet’s surface for a period of years, causing the death of many plant species which dramatically diminished the entire food chain.

A new study suggests an astronomical cause for two other extinction episodes. The Ordovician extinction event occurred 443.8 million years ago. This was a time known for rapid diversification in marine life and the appearance of the first plants on land. Scientists estimate that 71% of species disappeared during this event.

The Late Devonian mass extinction occurred 372 million years ago leading to the extinction of nearly 70% of species. It is the least understood of the five major events, and scientists have offered several possible explanations for it. The new study provides plausible astronomical explanations for both of these events.

In both the Ordovician and late Devonian extinction events, there is evidence that Earth’s ozone layer was severely depleted. A new study led by Dr. Alexis Quintana at the University of Alicante in Spain, including other researchers from Keele University in England, puts the blame for both events on nearby supernovas.

When a massive star runs out of fuel, it explodes with so much energy that a single supernova can temporarily release more energy than its entire host galaxy. The debris includes not only high-energy radiation, like X-rays and gamma rays, it also includes cosmic rays, charged particles moving at nearly the speed of light. A nearby supernova can blast enough energy to destroy our ozone layer. With that protective shield gone, the high-energy cosmic rays and the deadly radiation can bathe Earth’s surface at lethal levels.

The Crab Nebula, a supernova remnant in the constellation of Taurus. 

Credit NASA, ESA, and the Hubble Space Telescope Institute.

Life on our planet owes its existence to supernovas, as all elements heavier than hydrogen and helium – including oxygen, carbon, calcium, iron, and all the chemical elements that make us up – are created in those stellar explosions. As the authors say in the study, it is "a great illustration for how massive stars can act as both creators and destructors of life".

Dr. Quintana states, "Supernova explosions bring heavy chemical elements into the interstellar medium, which are then used to form new stars and planets. But if a planet, including the Earth, is located too close to this kind of event, this can have devastating effects."

It seems the universe can give us life, but can also take it away.

 

Each month, I write an astronomy-related column piece for the Oklahoman newspaper. After it is published there, I post that same column to my blog page.

This is reprinted with permission from the Oklahoman and www.Oklahoman.com.

Are We Close to Finding Extraterrestrial Life?

 The topic of many of my articles involves the search for extraterrestrial life. I look at what conditions are needed to support life on Earth and see if such environments exist elsewhere. For example, we found seasonal variations of methane in the Martian atmosphere. On our planet, methane is almost exclusively associated with life. I’ve written about astronomers’ efforts to find and study planets orbiting other stars to determine if they orbit in the habitable zone where water can exist on the surface. On Earth, virtually wherever we find water, we find living creatures. That may only be microbial life, such as that found in acidic hot springs or water trapped far below the surface, but life nonetheless.

Even if we only find such microbial life, that would be an astounding discovery. It would tell us that life can develop in locations other than Earth which at the moment is the only location in the universe where life is known to exist.

Recently, a newsletter called The Conversation ran an article in which the authors polled astrobiologists and other scientists on their belief in extraterrestrial life. The Conversation is an online source of articles written by researchers and academics across all disciplines. It gives them a platform to present their work to the public. We often read articles that say finding extraterrestrial life is “only a matter of time”, or “we are close to finding alien life.” And yet, we still await that discovery.

Exoplanets in their star's habitable zone. Are we close to discovering exo-life?

In 2024, three researchers – Peter Vickers, a Professor in Philosophy of Science at Durham University, Henry Taylor an Associate Professor in the Department of Philosophy at the University of Birmingham, and Sean McMahon, of the University of Edinburgh – did surveys, polling a number of astrobiologists, those scientists who study and look for the chances of life elsewhere, and scientists in other fields on their beliefs of the existence of alien life. They asked about their beliefs, based on all the research to date, of the existence of basic lifeforms, i.e. microbial life, complex forms, i.e. multicellular life, and intelligent extraterrestrial life.

Altogether, they received responses from 521 astrobiologists and 534 non-astrobiologists. Of the astrobiologists, 86.6% said they “agree” or “strongly agree” that extraterrestrial life, at least at the basic level, exists elsewhere. Less than 2% disagreed with the sentiment and 12% claimed to be neutral on the possibility. Of the non-astrobiologists, 88.4% also marked “agree” or “strongly agree” with the question. Scientists who don’t study the possibility of extraterrestrial life are not more skeptical than those who do. The authors of the survey felt that to be a rather significant result.

The survey asked about each level of life – basic, complex, and intelligent – separately. The results when asked specifically about whether “intelligent” aliens exist were not quite as optimistic. Only 67.4% of astrobiologists and 58.2% of other scientists agreed, still more than half. Only 10.2% of astrobiologists disagreed with that statement.

This survey cannot in any way offer proof of life elsewhere, but the preponderance of scientific research and evidence leads most scientists, at least in these fields, to accept the likelihood. Astronomers estimate that in our galaxy alone a trillion extrasolar planets, those orbiting other stars, exist. They further estimate that billions of Earth-like planets orbit in the habitable zone of their parent star.

Life on Earth is proving to be far more robust than we previously thought. Microbes called extremophiles can survive in all kinds of environments once thought unable to support any kind of life. Creatures called tardigrades, or water bears, have even been shown to survive in airless, radiation-filled outer space beyond our planet. I suspect that the existence of such extremophiles that survive in these hazardous or toxic locations is a large part of the thought processes of these scientists.

Perhaps it really is only a “matter of time” before we discover alien life forms. And. Some scientists say we may not even recognize alien creatures as living at first. We have no idea if “life as we know it” is all that there can be.

 

Each month, I write an astronomy-related column piece for the Oklahoman newspaper. After it is published there, I post that same column to my blog page.

This is reprinted with permission from the Oklahoman and www.Oklahoman.com.

Did Planets from the Inner Disk of the Milky Way Become Rogue Planets?

 We think of a planet as a non-luminous body that orbits a star, like the planets of our solar system. But that’s not always the case.

All stars form from clouds of gas and dust that collapse inward due to the pull of gravity. The pressure caused by the gravitational crunch squeezes gas in the center of each cloud so tightly that it heated the gas to extreme temperatures, generating thermonuclear reactions, and a new star is born. Our sun flared into existence four and a half billion years ago, far younger than the oldest stars, which are born in other parts of the galaxy.

But there was still quite a bit of leftover gas and dust surrounding the young sun which formed a disk around the new star. This leftover bit eventually becomes all of the planets, moons, comets, and asteroids that orbit our sun.

Our solar system lives in the spiral arms of the Milky Way galaxy. Most of the galaxy’s younger stars like our sun are in the spiral arms. Astronomers estimate that virtually all of these stars have planets, an average of two and a half planets per star.

The older stars of our galaxy mostly reside in a bulge surrounding the center of the Milky Way. Stars there have on average barely one planet per star.  MIT astrophysicist Tim Hallatt thinks he knows why. “The puzzle is, these planets (in the spiral arms) are very common,” Hallatt says. “And yet when we look at this other dominant population of stars in the Milky Way, they’re less common. So what’s going on?”

As is the case with all large galaxies like ours, when the Milky Way first formed some 12 billion years ago, star formation was fast and furious, a time Hallatt describes as galactic chaos, what astronomers generally refer to as “cosmic noon.” Also, the stars there were more closely bunched together than the stars in our neighborhood. The greater levels of energetic radiation from the process of rapid star formation plus the relative proximity of stars meant that the stars during cosmic noon experienced ten million times greater levels of radiation. This intense radiation would have heated the gas surrounding all these rapidly forming stars. The greater levels of radiation and heat blew away much of the remaining gas, leaving less raw material for planets.

When astronomers search for planets beyond our own solar system, they look at other stars. We currently know of more than 5000 such exoplanets, and the more we look, the more we find. Astronomers also find lots of rogue planets, planets that don’t orbit any star. They may have formed around a star but were ejected from their home stellar system, perhaps due to close passage of another star. The gravity of the passing star can rip a planet away from its home. Astronomers estimate that perhaps as many as four trillion rogue planets exist in our galaxy alone. That’s a huge number.

Artist's conception of a Rogue Planet

It’s likely that some of those rogue planets formed on their own, not as part of a stellar system. Perhaps some of the gas and dust blown out by the stars formed during the crowded cosmic noon eventually coalesced into rogue planets. Many of these rogue planets could have orbited a star but for the early period of rapid star growth.

Rogue planets may easily outnumber the stars in our galaxy. And some of those rogue stars may be causalities of the cosmic noon timeframe of our Milky Way galaxy.

Each month, I write an astronomy-related column for the Oklahoman newspaper. After it is published there, I post that same column to my blog page.

This is reprinted with permission from the Oklahoman and Oklahoman.com.