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.

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.

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.

The Amazing Hubble Telescope

 The Hubble Space Telescope has been and continues to be one of humanity’s greatest scientific instruments. With it, astronomers have already made 1.6 million observations and written more than 21,000 scientific papers. It added dramatically to our knowledge of the universe. Being such a complex instrument, NASA designed it so that it could be periodically serviced, replacing parts that wear out over time.  Five servicing missions visited Hubble. The most important was the very first one. It corrected a tiny mistake in the shape of its main mirror, which was off by less than the width of a human hair. The other four service missions replaced items such as batteries, gyroscopes, and electronic boxes, all of which have limited life. On some missions, astronauts installed state-of-the-art science instruments. Each service mission left Hubble a more capable and more productive observatory.

Hubble Space Telescope, credit STSCI, NASA, ESA

And capable it is. It showed us things astronomers never even guessed might be out there. Perhaps the most amazing science it produced came in the form of a series of long-exposure photographs, 342 in all, with a total exposure time of over 100 hours, known as the Hubble Deep Field. They pointed it to an apparently empty spot near the Big Dipper, a patch of sky about the equivalent of a pinhead at arm’s length.

Hubble Deep Field, credit NASA, ESA

Expecting to find maybe a few distant galaxies, the final combined images revealed more than 3,000 galaxies including what were at the time the most distant objects ever seen. The image amazed astronomers with the new data they obtained. That project was such a success that astronomers did another version from a spot in the southern hemisphere sky. With the success of those two images, astronomers then used Hubble to create the Ultra Deep Field image. It was a combination of 800 images taken over eleven and a half days, revealing more than 10,000 galaxies and again setting new distance records.

Hubble Ultra Deep Field, credit NASA, ESA

Hubble’s discoveries range far beyond simply observing thousands of galaxies in apparently empty patches of the sky. It was instrumental in discovering the existence and distribution of Dark Matter. The speed at which a planet orbits the sun depends on its distance from the sun, with planets farther out moving slower due to distance from the sun’s gravity. By the same token, stars at a galaxy’s edge should move slower than those closer in. But Hubble’s measurements showed that stars across the entire galaxy move at virtually the same speed, and move so fast that the gravity from all the matter of the galaxy couldn’t hold the galaxy together. Galaxies had to be embedded in a large shell of gravity-producing but invisible matter. Hubble was able to map the distribution of dark matter around the universe, helping to show it accounts for 85% of the matter in the universe. Using Albert Einstein's prediction that gravity can focus light, Hubble was used to take images of distant objects the light of which is focused by intervening sources of gravity. By studying these, they could measure the gravity from dark matter sources.

Gravitational Lensing from Dark Matter surrounding a galaxy cluster, credit Gravitational lensing, credit NASA, ESA, and J. Lotz

Hubble data measured the speed at which the universe expands, showing that the expansion is speeding up, leading to the discovery of Dark Energy. Hubble helped to verify the existence of exoplanets, those orbiting other stars. Astronomers used Hubble to study the formation and evolution of galaxies. Because of its keen vision, it helped astronomers better understand how stars change with age, the mechanics of supernovas, and the cause of short gamma-ray bursts, a subject that puzzled astronomers for many years. And this is only the tip of Hubble’s accomplishment iceberg.

We no longer have the space shuttle that flew astronauts on all the Hubble servicing missions. Now, it only has two functioning gyroscopes, which enable its precise pointing. Any observation it makes from now on will take more time. Hubble’s end is certainly in sight.

The Webb Space Telescope, Hubble’s successor, has taken the mantle as the best space telescope, but astronomers will still mourn Hubble’s passing whenever its mission finally ends.

 

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.

Our Closest Black Holes

 The Cosmic Zoo contains some really strange beasts. Stars that are fifty times larger than our sun with surface temperatures above 100,000 degrees, compared to our sun’s temperature of a measly 10,000 degrees. Tiny stars with less than a tenth the mass of our sun and surface temperatures cooler than lava. Supernovae that can outshine an entire galaxy. Neutron stars, large stars that collapsed down to the size of a small city, so dense that a teaspoonful can weigh millions of tons.

Perhaps the weirdest celestial inhabitants are black holes. These form from the remains of giant stars at least 25 times the mass of our sun. They warp space and time in their vicinity. They can devour entire stars and shoot our death rays of energy that can easily destroy a planet with a direct hit.

Fortunately, there are no black holes close to us. At least that we know of. But you can easily spot the resting place of the closest black holes to us.

Stars are born in star clusters, typically a hundred or more at a time. We can identify a few dozen stars born with our sun four and a half billion years ago. All star clusters form lots of small stars, a moderate number of average stars around the size of our sun, and only a few very large stars. Large stars burn out quickly and, if large enough, form black holes.

Photograph of Hyades star cluster in Taurus with the bright star Aldebaran in the lower left. Credit Maurice Toet

The closest star cluster to us is the Hyades star cluster. It sits in the constellation of Taurus, the Bull. It makes the face of the bull with the bright star Aldebaran marking one of the bull’s eyes. The Hyades cluster is only 150 light years away, practically in our backyard as stellar distances go.

The constellations around the Hyades star cluster. It is visible near the eastern horizon at 11:00 p.m. in October, but high in the sky in early February evenings. Map produced using Night Vision star mapping software.

A research team led by Stefano Torniamenti from the University of Padua in Italy studied the distribution and dynamics of stars in the Hyades star cluster. “Our simulations can only simultaneously match the mass and size of the Hyades if some black holes are present at the center of the cluster today,” Torniamenti said.

That’s not surprising. Astronomer Simon Zwart of the University of Cambridge studies the dynamics of star clusters. Though not involved in the new study, he says “Every open cluster older than some 5 million years and containing over 1,000 stars is expected to host a few black holes.”

Taurus is highest in the sky in late winter and early spring but is visible around 11:30 p.m. in the eastern sky. The black holes themselves are invisible, but you can easily spy their home star cluster. 

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.

Surf's Up! In a BIG Way!

 As stars go, our sun is rather average in size. The smallest stars, called red dwarf stars, can be less than one-tenth the mass of our sun. The largest stars are fifty times our sun’s mass or more. Most stars are not single, like our sun. NASA estimates that more than half of all stars have one or more partners, where two or more stars are in orbit around each other. Some astronomers calculate that as many as 85% of stars in the universe are in multiple star systems.

Sometimes stars in a double star system can orbit quite close to each other. That can cause some strange effects.

When you hear the words tides and waves, you probably picture an ocean beach, perhaps with surfers. On Earth, our tides are caused by the gravitational pull of the Moon. But our tides are rather gentle, with the ocean’s edge slowly creeping up and down the beach twice a day.

If two stars orbiting each other come close together, each can pull tides on its companion. If those stars are really large, they can pull big tides. 

Stars orbiting close together can pull large tides on each other. Credit NASA, JPL

Astronomers describe a binary system in which the two stars have elongated orbits as “heartbeat stars.” Because of their orbits, the distance between the stars can vary dramatically. When the two stars are closest, they can cause huge tidal forces on each other, which causes large, regular brightness changes in the stars, such as a heartbeat might do on an electrocardiogram.

A heartbeat star (center of each image). Credit: NASA ESA CSA I. Labbé Swinburne University Of Technology Image Processing

One such binary star was first detected in the 1990s during a project known as MACHO which stands for Massive Compact Halo Objects. The ‘smaller’ star is ten times as massive as our sun, while the larger one is 35 times as massive as our sun and 24 times wider than our sun. The tidal force between them doesn’t just create gently moving tides as on Earth. The smaller star pulls tides on the larger star so hard it creates waves 3 times taller than the diameter of our sun.

"Each crash of the star's towering tidal waves releases enough energy to disintegrate our entire planet several hundred times over," says astrophysicist Morgan MacLeod, from the Harvard-Smithsonian Center for Astrophysics who studied the binary pair. "These are really big waves." The smaller star also makes tidal waves, but, being smaller, the waves on its surface are much smaller.

The energy of these gargantuan tides causes the two stars to slowly spiral closer together. Eventually, they will crash into each other and merge into one even larger star. The star system sits in the Large Magellanic Cloud, a satellite galaxy of your Milky Way 160,000 light years away. Too bad, as that collision would be a dramatic sight if it were closer.

Surfers may be desirous of such waves, but they would need to use a lot of sunscreen. The surface temperature of such stars can easily exceed 37 million degrees.

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.

Too Much of a Good Thing?

 Away from our city lights, the night skies over our planet glisten with thousands of stars. Those we can see with our eyes are only the tip of a nearly infinite stellar iceberg. While the starry night sky provides us with breathtaking beauty, astronomers with their telescopes study much more. They examine the stars, the galaxies that stars reside in, and the space between galaxies. They use these telescopes to peer billions of years back in time, all looking for clues to how the universe works, where it came from, how it’s changing, how we came to be.

Occasionally when you share in the beauty of our night sky, you might see a “star” moving among all the others. These artificial satellites, the biggest of which is currently the International Space Station, might even elicit some level of excitement.

But, imagine you’re an astronomer studying a distant galaxy, looking for clues to how the universe came to be when one of these satellites slides across the view of your telescope disrupting the precious data your instruments are taking. That would be a big nuisance to that astronomer’s studies.

You might think, hey, it’s one little blip and there are so few, what harm can they do? But, for every satellite you notice at night, there are many more that you can’t see but which can interfere with astronomical data.

SpaceX, a private space launch company, uses its Falcon 9 rocket to launch satellites for private communications companies to orbit. One of its biggest customers, Starlink, uses thousands of satellites to provide internet access around the world. Each Falcon 9 can launch 50 or more Starlink satellites. It’s certainly a fascinating sight to watch this train of satellites traveling across your night sky as they slowly separate and move to their individual orbits. Such satellite trains initially led to many UFO reports, although the sight is common enough that they rarely generate such reports anymore. Once in their final orbit, they shine so faintly that the human eye can barely discern them.

But astronomical telescopes easily spy them. And they are more than just a nuisance. They produce bright trails on images taken by those telescopes. They can block out a star of particular interest or cause brief, transient phenomena, like the poorly understood gamma-ray bursts, to be totally missed.

Satellite tracks in an image from Cerro Tololo Inter-American Observatory in Chile 

Credit CTIO-NOIRLab-NSF-AURA

Recently, Amazon’s Blue Origin launched the first of one hundred, Blue Walker satellites. It is the largest commercial satellite ever launched, roughly half the size of a tennis court, and it rivals the brightest stars in the night sky. The fully operational Blue Walker satellites may be even larger and brighter.

I remember as a child how exciting it was to glimpse the rare satellites moving across my night sky. But for astronomers trying to understand the workings of our universe, these are becoming much more than an annoyance. All too often, they cause the loss of rare, often irretrievable astronomical data.

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 Oklahoman.com.

Is the Hypothesized "Planet Nine" Actually a Primordial Black Hole?

 On March 13, 1781, astronomer William Herschel pointed his telescope into the night sky and discovered the planet Uranus, the first such discovery in historical times. Over the next 45 years, as astronomers observed Uranus looking for possible moons, they realized its orbit didn’t follow the known laws of gravity. Some astronomers surmised that perhaps Newton’s gravitational laws didn’t work so far from the sun.

But two mathematicians decided that the discrepancy occurred due to the gravitational attraction of an eighth planet even farther out. Unbeknownst to each other, both French astronomer Rubin Le Perrier and British mathematician John Couch Adams began calculating the likely position of such a planet based on the aberrations of the orbit of Uranus. On September 23, 1846, French astronomer Johanne Galle found Neptune within one degree of the predicted position. The effect of Neptune’s gravitational pull on the orbit of Uranus led to its discovery.

In January 2015, Caltech astronomers Konstantin Batygin and Mike Brown noted some rather odd orbits of five asteroids in the far outer regions of our solar system. Using computer modeling, they predicted the presence of a ninth planet ten times larger than Earth whose gravity they theorized affected the asteroids. They dubbed it “Planet Nine.”

That planet has never been discovered even with today’s sophisticated telescopes, yet according to Brown and Batygin, new evidence continues to support their hypothesis. This negative result has led some astronomers to propose a radical idea: maybe the cause of the odd orbits isn’t a large planet but rather a small black hole.

Typically, black holes result from the death of massive stars and are typically five to ten times the mass of our sun. But the extreme conditions at the earliest stages of the formation of the universe could have created smaller, planet-sized black holes, called primordial black holes, although we’ve yet to find any. 

Primordial black holes may exist throughout the cosmos. Credit NASA

A planet ten times the size of Earth should have been found, many astronomers believe, but a black hole of the same mass would be tiny and impossible to see. The only way to discover one is to use the same method astronomers use to find any stellar-sized black hole, by way of its massive gravity. A planet-sized black hole might be invisible, but the gravity of one could certainly cause the observed effect.

I think the idea of a primordial black hole at the edge of our solar system is exciting. As long as it stays out there.

Alien Signals? Likely Not, But the Most Exciting Possibility Yet!

      Earth is a noisy planet. Not with sound waves, which never leave the atmosphere, but with all sorts of radio noise. Between radar beams from weather monitoring stations, airports and military use, TV and radio signals, and even deliberate attempts by astronomers to send messages to any listening aliens, our planet constantly announces its presence to the universe at large.

Because we are so radio noisy, astronomers have for decades tried to find such radio signals emanating from any other existing alien civilizations in our Milky Way, with little success. In 1977, astronomers performing such a search with a giant radio telescope run by Ohio State University detected a signal, a powerful radio burst, dubbed the “WOW!” signal. It never appeared again despite much searching.

In 2015, billionaire Yuri Milner donated $100M to create a program designed to search for extraterrestrial radio signals, the Breakthrough Listen Project. The project uses the Parke Radio Telescope in Australia, operated by the Commonwealth Scientific and Industrial Research Organization.

 Recently, news broke that the project detected a narrowly-focused beam of 980 MHz radio waves detected in April and May 2019. The signal came from the direction of our nearest stellar neighbor, Proxima Centauri, which has two planets orbiting it, and one is Earthlike. That frequency is important because human-made craft and satellites typically don’t use it, lending credence to the possibility of it coming from an alien civilization.

Parke Radio Telescope, credit Commonwealth Scientific and Industrial Research Organization

The powerful burst excited astronomers of the project. Sofia Sheikh, an astronomer at Penn State University, led the analysis of the signal. While the team has yet to release its full report, Scientific American interviewed Sheikh. She said, "It's the most exciting signal that we've found in the Breakthrough Listen project because we haven't had a signal jump through this many of our filters before.”

No repeat signal has been detected, and the team still must rule any natural signals, such as a distant comet or some other astronomical. But astronomers excitedly await the full report. We may have finally discovered that we have neighbors.

 

    Each month, I write an astronomy-related column piece for the Oklahoman newspaper. On the following day, I post that same column to my blog page.

    This is reprinted by permission from the Oklahoman and www.newsok.com.

Are We Close to Finding Earth 2?

 

NASA and other space agencies have launched several missions to search for exoplanets, planets that orbit other stars. The Holy Grail of such programs is finding an Earth-like planet orbiting a sun-like star at the right distance to allow liquid water on the surface. Such planets seem to be the most likely candidates to search for life.

While astronomers have yet to find a perfect Earth 2, statistical analysis of NASA’s most successful planet hunter, the Kepler Mission, uncovered some promising data. A study by NASA scientists alongside collaborators from around the world who worked on the Kepler mission came to an exciting conclusion. According to the research, about half the stars similar in temperature to our Sun could have a rocky planet capable of supporting liquid water on its surface.

Image Caption/Credit: NASA’s Kepler Planet Finder telescope, credit NASA

"Kepler already told us there were billions of planets, but now we know a good chunk of those planets might be rocky and habitable," said the lead author Steve Bryson, a researcher at NASA's Ames Research. "Though this result is far from a final value, and water on a planet's surface is only one of many factors to support life, it's extremely exciting that we calculated these worlds are this common with such high confidence and precision."

Kepler detected planets by continuously staring at thousands of stars, watching for a tell-tale drop in brightness caused by an orbiting planet crossing in front of a star. Such a method couldn’t detect planetary systems seen more face on, so astronomers had to use statistical methods to extrapolate from the Kepler data to all the other stars in our galaxy. Kepler discovered so many exoplanets from its limited mission that astronomers now believe that more than half of the four billion stars in the Milky planet possess planets, typically more than one.

Using their most conservative estimate, that 7% of all sun-like stars have Earth-like planets, meaning some 300 million exist in our Milky Way alone. Their most likely estimate states that Earth-like planets orbit 50% of sun-like stars, making more than 2 billion Earth-like planets. Since we know of only one planet with life, ours, those planets are the best place to begin to search for alien forms of life.

Each month, I write an astronomy-related column piece for the Oklahoman newspaper. On the following day, I post that same column to my blog page.

 This is reprinted by permission from the Oklahoman and www.newsok.com.

Where Did the Gold in Your Ring Come From?

 

Astronomers have a pretty good understanding of where the matter in our universe comes from. In the beginning, there was only hydrogen, helium, and a tiny smattering of lithium. Everything else, the oxygen we breathe, the carbon that makes up so much of our bodies, the silicon, magnesium, aluminum, and other elements that make up our planet, were all formed inside stars and released into the wider universe when stars explode.

Supernova Remnent Casseopeia A. Credit NASA

But there is one element that still has astronomers bumfuzzled: gold. There is too much of it. Supernova explosions can’t begin to account for the amount that we see because the gold is trapped in the neutron stars, the remnants of supernovas. Colliding neutron stars release prodigious amounts of gold, as do so-called magneto-rotational supernova. These rare supernovas spin so fast and generate such strong magnetic fields that they literally turn themselves inside out. This releases all of their trapped gold atoms. But while both produce extraordinary quantities of gold, they are extremely rare and cannot begin to account for all the gold we find here on Earth.

Chiaki Kobayashi is an astrophysicist at the University of Hertfordshire in the United Kingdom. She led the new study to determine the origin of gold. "There are two stages to this question," she said. "Number one: neutron star mergers are not enough. Number two: Even with the second source, magneto-rotational supernova, we still can't explain the observed amount of gold." Kobayashi and the other study authors accounted for the formation and relative abundance of all elements from carbon to uranium. All except for gold. Its abundance remains a mystery.

So, the next time you put on that gold ring or necklace, you can marvel that our Earth has as much gold as it does.

 

 Each month, I write an astronomy-related column piece for the Oklahoman newspaper. On the following day, I post that same column to my blog page.

 This is reprinted by permission from the Oklahoman and www.newsok.com.

 

Any Volunteers to Be the First to Travel Through a Wormhole?

Science fiction has long imagined wormholes as a means of traversing the great distances between the stars in short, by human standard, timespans. Such literary devices allow spaceships, in essence, to cover great distances in hours or days instead of centuries that normal space travel would require. Wormholes connect two points in space in a way that the distance between them through the wormhole is much shorter than the distance between them in normal space, like taking a cosmic shortcut.

General relativity tells us that to make a wormhole requires enormous amounts of negative energy which, according to Einstein’s equations, isn’t possible. But, the other grand realm of physics, quantum mechanics, says not so fast.

In a study titled “Humanly traversable wormholes,” Juan Maldacena of the Princeton Institute of Advanced Study and Alexey Milekhin, a graduate of astrophysics student also at Princeton University, claim that we can make such wormholes. They base their calculations on the Randall-Sundrum II model, a theory that postulates a five-dimensional, warped geometry for the universe instead of the one we are familiar with that contains only normal four dimensions. Maldecena and Milekhin claim, using that theory, stable, person-sized wormholes could be created.

                                             Spaceship entering a wormhole. Credit NASA

You have to start, the researchers say, with a black hole that has a large magnetic charge. Such a special wormhole would allow spacefarers to traverse, say, 10,000 lightyears, one-tenth of the way across our galaxy, in a second. The only problem is that to the people at either end of the wormhole, that trip would appear to take 10,000 years, meaning these special wormholes really create shortcuts through time rather than space.

I bet they could still find volunteers willing to take that trip.

  

Each month, I write an astronomy-related column piece for the Oklahoman newspaper. On the following day, I post that same column to my blog page.

 This is reprinted by permission from the Oklahoman and www.newsok.com. 

Two Celestial Visitor over Next Two Months

Two celestial visitors grace our skies over the next couple of months. The first one is a 2-mile-wide asteroid that, if it struck Earth, would cause significant damage. The second is a comet that, if it keeps getting brighter at the rate it is now, will become bright enough to cast shadows at night.

The first cosmic guest comes calling on April 29^th when asteroid 1998 OR2 passes by. The size of a small city, and therefore quite destructive should it ever strike Earth, it was discovered on July 24^th, 1998, by the now-defunct Near Earth Asteroid Tracking program, funded by NASA and operated jointly through several major U.S. observatories.

NASA classifies 1998 OR2 a “potentially hazardous asteroid.” To receive that designation, an asteroid must be at least 500 feet across and pass within 4,650,000 miles of Earth. While an asteroid at that distance poses absolutely no threat to Earth, its orbit could be altered by gravitational tugs from other planets or moons in our solar system so that, on a future orbit, it might pass much closer to Earth or even impact our planet.

The closest approach of 1998 OR2 occurs at 4:56 CDT in the morning of the 29^th. At that time, it will still be 3.9 million miles away, or 16 times the average distance between Earth and the Moon. Even with its relatively close proximity, it won’t be visible to the naked eye. But if you have a telescope and a clear, dark sky you can spot it. Go to https://earthsky.org/astronomy-essentials/asteroid-52768-1998-or2-april-2020-how-to-see#tips for tips and charts to locate it.

Asteroid 1998 OR2 Image credit Gianluca Masi and The Virtual Telescope Project

Comet C/2019 Y4 ATLAS may become a spectacular sight in our night sky in late May. It was discovered on December 28, 2019 by the Asteroid Terrestrial-impact Last Alert System (ATLAS, hence the name), another NASA-funded program, operated by the University of Hawaii. As astronomers tracked it after the discovery, the comet brightened at an unprecedented rate. While astronomers expect that rate of brightening to slow down, if it were it continue to brighten as it has been, it will rival a crescent Moon in our night sky.

One major hurdle exists before the comet can bloom into a bright, beautiful sight in our night sky. The comet will pass closer to the sun than Mercury. Bright comets passing close to the sun often break into pieces or even disintegrate altogether. But if it survives that close pass, it could become the brightest comet since Comet Hale-Bopp, which passed by in 1997.

ATLAS C2019Y4_200318_FB credit  Rolando Ligustri

These two should excite amateur astronomers and all those who wonder at the night sky.

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

This is reprinted by permission from the Oklahoman and www.newsok.com.

Did NASA Already Find Martian Life?

In 1992, astronomers discovered three objects roughly the size of Earth orbiting another star, the first known exoplanets. No one expected life on those objects because the star was a pulsar, the remains of a star that blew up as a supernova, and the “planets” had actually formed from the debris of that explosion.

Three years later, astronomers found the first true exoplanets orbiting the sun-like star 51 Pegasi. Now, the NASA Exoplanet Archive lists 4113 confirmed exoplanets with more than 3600 exoplanet candidates awaiting confirmation. Astronomers believe that we have only touched the tip of the exoplanet iceberg. Data suggests that our Milky Way galaxy alone contains some two hundred billion planets. As of now, there’s no solid evidence suggesting that life exists on any of them.

But some scientists believe that we already found life on another planet, one much closer to home. In 1976, NASA landed twin spacecraft on Mars, Viking 1 and 2. Each included automated laboratories designed to search for microscopic life on the Red Planet.

Both craft, which landed 4000 miles apart, included a simple test called the Labeled Release experiment. It added a nutrient broth to a small amount of Martian soil and checked to see if any metabolic byproducts, like carbon dioxide, were released. Every test by both landers reported positive results. However, the other experiments on both landers found no organic chemicals, which seemed to preclude any lifeforms. Since then, most scientists decided that some odd chemistry in the Martian soil falsely mimicked those life signs.

Viking Lander, credit NASA

But not all scientists. Gilbert Levin was the principal investigator for the Labeled Release experiment for both landers. In a recent article in Scientific American, he wrote “The Viking LR (experiment) sought to detect and monitor ongoing metabolism, a very simple and fail-proof indicator of living microorganisms. Several thousand runs were made, both before and after Viking, with terrestrial soils and microbial cultures, both in the laboratory and in extreme natural environments. No false positive or false negative result was ever obtained. This strongly supports the reliability of the LR Mars data.”

It may be decades or centuries before we confirm life on an exoplanet, if we ever do. But we may have already discovered life on another planet, right next door.

Killer Asteroid? Not This Time.

Sixty-six million years ago, a 6-mile-wide asteroid smashed into what is now the Gulf of Mexico. Red-hot debris blasted into the atmosphere and fell back to Earth, causing planet-wide fires. After that, dust and soot filled the air for years, blocking most of the sunlight from the surface of the planet. The net result is that some 75% of life on Earth, including all dinosaurs, went extinct.

On September 9^th this year, asteroid 2006 QV89 will come calling. While its size, a mere 130 feet across, makes it far less dangerous than the dinosaur killer, if it hit a major city, it would certainly destroy most or all of it and kill perhaps millions of people. But you probably don’t need to worry too much. NASA and the European Space Agency (ESA) estimates there is only a 1 in 7,299 chance it will strike Earth. Their best estimate is that it will miss Earth by more than 4 million miles. That’s more than 16 times the Moon’s distance from us.

Artist rendering. Credit NASA

ESA keeps a tally of known asteroids that pose a collision risk with Earth. You can find it at http://neo.ssa.esa.int/risk-page. While this 1 in 7,300 risk isn’t very high, an asteroid designated 2010 RF12 poses a 1 in 16 chance of collision with Earth on September 5^th,, 2095. While that asteroid is less than 35 feet across, it will create a spectacular sight if it does enter our atmosphere, and can still cause considerable damage.

No other known asteroid poses a significant risk in the near future, so this upcoming near-miss will be our closest dance with asteroid destruction for a while.

Until the next asteroid with a high collision risk is discovered.

On or about the first Tuesday of each month, I write an astronomy-related column piece for the Oklahoman newspaper. On the following day, I post that same column to my blog page. This is reprinted by permission from the Oklahoman and www.newsok.com.

Measurements Give New Insight into the Structure of the Lunar Crust

Everyone has seen the full Moon in the night sky. The familiar dark splotches called ‘maria,’ Latin for seas, create patterns on the lunar surface. Some people see a man’s face, the Man in the Moon. Others imagine a frog or a rabbit. Whatever you might picture when you look at the full Moon, the pattern of large, dark areas overlying lighter material is quite obvious. The maria are composed of lava that poured out from asteroid impacts and covered the lighter surface material.

The Lunar Nearside, credit NASA

From Earth, we only see the one side of the Moon, so you might assume this arrangement of maria over lighter material continues on the far side of the Moon. Astronomers assumed that, too, until the Russian Luna 3 spacecraft sent back the first, grainy pictures of the lunar far side in 1959. Although there were a few dark patches, they were quite a bit smaller than the familiar maria of the near side and didn’t cover much of the far side surface.

The Lunar Farside, credit NASA

Subsequent studies of the Moon revealed that the crust on the far side is as much as 10 miles (ca. 16 km) thicker than the near side crust. Because of this, asteroids can’t so easily puncture the far side crust, so fewer and smaller maria formed there. For decades, astronomers puzzled as to what might have caused this. Until recently, the best idea was that we originally had two moons. Very early on, the two collided at low speed on the far side. The material from the smaller impacting moon flowed over that side, creating the thicker crust.

Measurements made by the Gravity Recovery and Interior Laboratory (GRAIL) mission in 2012 provided more data, suggesting an impact from an outsider. "The detailed gravity data obtained by GRAIL has given new insight into the structure of the lunar crust underneath the surface," said Meng Hua Zhu, a co-author on the new paper on the subject and a scientist at Macau University of Science and Technology in China. Using computers, the researchers modeled 360 different collisions and compared all the results to what we know about the moon today. The best fit with our Moon suggests that a collision of an object 500-560 miles (ca. 805-901 km) across could have done the trick.

Artists concept of Lunar Farside collision, credit NASA

Luckily for us, there are no other such large objects wandering around near our orbit today.

On or about the first Tuesday of each month, I write an astronomy-related column piece for the Oklahoman newspaper. On the following day, I post that same column to my blog page.

This is reprinted by permission from the Oklahoman and www.newsok.com.

Beaches. And Deserts and Sandboxes.

Perhaps you’ve heard this before: There are more stars in the universe than all the grains of sand in all the beaches, desserts and sandboxes on Earth.

There are a lot of sand grains on Earth. Sand constitutes a major fraction of the makeup of Earth. Scientists estimate the number by measuring the average size of a sand grains, then calculating how many sand grains it would take to fill, say, a gallon jug. Using the latest geological studies, they calculate the total volume of sand on Earth. Scientists estimate that Earth contains 7.5 sextillion sand grains. That is 75 followed by 17 zeros. That’s a lot of sand.

Astronomers calculate the total number of stars in the universe by studying nearby galaxies, ones in which we can count the stars, to see how many it takes to make a galaxy shine. Then, based on detailed counts of galaxies we can see, and making conservative estimates of how many we can’t see, they estimate the total number of stars in the universe. Our universe contains at least 70 septillion stars, 7 followed by 23 zeros.

Astronomers estimate there exist roughly 10,000 stars for each grain of sand on Earth. That’s a lot of stars.

Credit NASA-ESA

Astronomers recently discovered the origin of sand grains. For years, they believed that only sun-like stars created lots of carbon and silicon dust, and the silicon dust is the source of sand. That meant that the universe had to evolve to the point where there were lots of sun-like stars before lots of sand could accumulate. Recently, astronomers discovered the galaxies that formed very early in the universe, before many sun-like stars could form, contained a lot of dust. Long before stars like our sun were common, planets like Earth may have formed.

There may be a huge number of planets in our universe capable of supporting life.

On the first Tuesday of each month, I write an astronomy-related column piece for the Oklahoman newspaper. On the following day, I post that same column to my blog page.

This is reprinted by permission form the Oklahoman and www.newsok.com.

First Generation Stars

When the universe began 13.7 billion years ago, the only hydrogen and helium plus a tiny smattering of lithium existed. All other elements, like carbon, nitrogen, oxygen, gold, platinum, all the stuff we and our planet are made of, was created in the nuclear furnaces that power stars.

A star forms when gravity causes a cloud of gas to collapse until the central region is dense enough to support that nuclear fusion which converts hydrogen and helium into other elements. To do that, the cloud must shed heat or the thermal pressure halts the collapse. Hydrogen and helium can’t lose heat very efficiently, so the very first stars had to be huge, with a gravitational pull strong to overpower the thermal pressure. Those first stars were 200 to 400 times the size of our sun.

Huge stars live very short lives, and after only a few million years at best, these stars explode in supernova explosions more powerful than anything this side of the Big Bang. The heavier elements created then blast into space to help form the second generation of stars. Heavier elements shed thermal heat at a higher efficiency, so second generation can be small, even smaller than our sun.

Astronomers have looked for stars as close as possible to that first generation of giant stars. They judge closeness to first generation by the amount of elements heavier than helium, “metals” to astronomers.

A team of astronomers from Johns Hopkins University recently announced the discovery of a star with the lowest known amount of heavy elements of any known star. The star is 13.5 billion years old, and may well be a second generation star. Lead author, Dr. Kevin Schlaufman, commented “The discovery of this star means more stars with very low mass and very low metal content are likely out there – perhaps even the universe’s very first stars.”

The next big step would be discovering a star containing nothing but hydrogen and helium, a first generation star.

On the first Tuesday of each month, I write an astronomy-related column piece for the Oklahoman newspaper. On the following day, I post that same column to my blog page.

This is reprinted by permission form the Oklahoman and www.newsok.com.

Is This the Way the World Ends?

Astrophysicists feel like they have a pretty good handle on how the universe began. Nearly 14 billion years ago, a quantum fluctuation randomly popped into being and expanded rapidly, at times even faster than the speed of light. All matter and energy and the laws of physics for the entire universe came into being with that quantum fluctuation, that we now call the Big Bang.

While there is debate on some of the details of this Big Bang theory, the basic picture is accepted by the vast majority of scientists. The ending of the universe is open to far more speculation. Our universe is still growing larger from that Big Bang beginning. And evidence points to the expansion rate increasing, due to some mysterious, unknown force we call Dark Energy. Some astrophysicists think it may expand forever, galaxies simply moving farther and farther apart until our Milky Way becomes totally isolated in the universe. Others think that expansion force is so great, it will eventually rip the galaxy apart, then our solar system, ourselves and, finally, atoms themselves. Ultimately, those scientists say, the universe will consist nothing but a very cold sea of low energy photons.

Some astrophysicists argue that the expansion eventually halts, and the universe starts to collapse, perhaps back to the singularity it all started with. Some think the universe will bounce from that collapse, leading to another Big Bang, one of an infinite successions of such beginnings.

In a recent study led by Anders Andreassen, a physicist at Harvard University, the study scientists claim the universe’s final moment will be triggered by bizarre consequence of subatomic physics called an instanton. An instanton is one solution to equations governing the motions of subatomic particles. An instanton can create a tiny bubble that will expand throughout the universe at the speed of light, swallowing everything in its path. Instantons create this bubble in the Higgs field, the quantum field that gives us the newly discovered Higgs boson and which imparts mass to all subatomic particles.

"At some point you will create one of these bubbles," Andreassen says. "It will be very unpleasant." For ‘unpleasant’ read ‘the end to all life and all chemistry as we know it.’

No need to sit and worry about it, though. Although it could occur tomorrow, the odds are that the universe has a lifetime of somewhere between 10 octodecillion years (one with 58 zeros after it) and 10 quinquadragintillion years (one with 139 zeros after it). Just like the world-busting, giant killer asteroid with Earth in its crosshairs, it’s not likely to happen in our lifetime. It likely won’t occur within in the lifetime of our solar system, probably not even in the lifetime of the Milky Way galaxy.

But it is coming, sometime, to a universe near you.

On the first Tuesday of each month, I write an astronomy-related column piece for the Oklahoman newspaper. On the following day, I post that same column to my blog page.

This is reprinted by permission form the Oklahoman and newsok.com.