Author: Ghina M. Halabi

Dr Ghina Halabi is an astrophysicist at the University of Cambridge and Programme Director at Cambridge Judge Business School's Entrepreneurship Centre. Previously, she worked as a research scientist at the Institute of Astronomy and Junior Research Fellow at Wolfson College, University of Cambridge. Ghina is the first person to obtain a PhD in astrophysics from a Lebanese university, the American University of Beirut, where she worked as lecturer before moving to Cambridge. Her astrophysics research covered various areas of stellar evolution and she is a fellow of the Royal Astronomical Society and European Astronomical Society. Ghina is Founder and Executive Director of She Speaks Science, and an advisory board member for Public Engagement at Cambridge University. Ghina consults and leads training workshops on communication with storytelling. She is a public speaker at international conferences and global forums including UN and TEDx and is frequently featured in mainstream media including BBC Future and various podcasts.

Blackholes lurking in the shadow, ringing across the Universe

On a bleak December evening in 1915, a German lieutenant scribbled away in his notebook as the World War I raged outside the trench on the Russian front. The barrack reverberated with the noise of war; exploding of shells, shouting of orders, whistles and the cries of wounded men. As he pored over Einstein’s paper, he was more and more incredulous. What his calculation proved was that if any mass is compressed to fit a certain radius, something very strange happens; no known force would stop it from collapsing and nothing would be able to escape that radius. He had found the first exact solutions to Einstein’s equations of general relativity. He slams the papers down and sits back in his chair. “I must write to Einstein”, he thought.   

That 40 year old lieutenant was physicist and astronomer Karl Schwarzschild. The radius he conjured while bullets whizzed over his head later became to be known as the Schwarzschild radius. It defines a surface known as the black hole event horizon, a bottomless hole in space beyond which no information can escape and physics breaks down fundamentally.

The enigma of black holes exceeds the fact that they were worked out on the front line of World War I. Originally, they were merely a thought experiment on paper. Einstein loved thought experiments and although he found their mathematics accurate and beautiful, he brushed the idea off as an implausible concept thinking that nature would protect us from their formation. However, now we know that it doesn’t. Nature creates them by killing off stars, over and over again. As star matter collapses, it gets packed and a black hole forms.

Not only do black holes exist, but they’re also abundant in the Universe. Our galaxy alone is home to a few hundred billion stars. About 1% are big enough to collapse at the end of their lives and become blackholes. So that’s a lot of black holes already, not to mention the supermassive black hole that lurks at the centre of our galaxy and weighs a hefty equivalent of few million suns.

Black holes have starred two of the most exciting discoveries of our century. In 2015, two blackholes, each about 30 times the mass of the sun, crashed into each other creating a larger blackhole and sending mighty cosmic quivers through space and time. The “ringing sound” of this collision could be picked up by LIGO, the most sensitive measuring instrument ever created. The historic Nobel prize-winning detection revealed secrets about the origin and evolution of black holes, and about extreme cosmic neighbourhoods.

More recently the world saw the first picture ever of a blackhole. It was snapped by an Earth-sized virtual telescope made of connected radio dishes around the globe. This virtual telescope has the highest magnifying power of all devices ever devised by human beings. How do we image a blackhole if it’s inaccessibly hidden beyond our grasp of observation? As the black hole devours matter towards it from very far distances, gas crushes in at nearly the speed of light and its temperature rises to hundreds of billions of degrees. Thus we have this incredibly hot gas around the blackhole waiting for its turn to get in, long enough for us to observe it as a glowing ring. The black hole’s silhouette lingers at the centre of the ring, a black void that stares back blankly.     

One of the most intriguing aspects of a blackhole is that it doesn’t have anything physical at its surface. Thus all the information that a black hole can possibly contain is equivalent to the amount of information that can be packed on the surface of its event horizon. But things get even stranger. According to theorists, if an unfortunate astronaut falls into this cosmic abyss, to us outsiders her time will be observed to slow down, and it stops at the event horizon. So although to her it may seem that she has crossed it and met her fate, to us it will look like she is smeared on the outside of the event horizon and never gets inside.

What actually happens in their shadowy regions is a perennial mystery. Currently our laws of physics are incomplete and we just have no idea. It’s where two fundamental theories describing our world clash head on: quantum theory, the physics of the tiny, and the theory of Einstein’s theory of spacetime and gravity which describes the very largest scales.

Although they are firmly facts of science, blackholes can be stranger than fiction and what happens inside their event horizon, so far stays in the event horizon.

Illustration: NASA-Langley.

Music of the Spheres

Humans have been in awe of the harmony of the heavens since times immemorial. Ancient Greeks believed that celestial bodies made music. In the clinging of hammers Pythagoras heard “a clue from God”, or so a folk myth goes. Stretching strings and plucking them, he discovered an intimate connection between mathematics and music, and that objects produced sound when in motion. He was thus convinced that planets moving in orbit should be humming a heavenly tune, and he sought to find the astronomical harmony of the cosmos.

In our modern times, another polymath longed for a similar fulfilment. In 1926 Arthur Eddington, an English astronomer lamented in his book The Internal Constitution of the Stars how the star’s deep interiors are further beyond the reach of human exploration than any other region in the Universe. As telescopes probe deeper and deeper into space, he beseeched to know how we can look beyond the barriers of the stellar surface. What instrument can pierce through and probe its hidden secrets, he wondered. Scientists now have the means to pierce through and see into a star. It’s called asteroseismology, the science of studying the music of the spheres. Pythagoras would have jumped in joy and elation.

Listening to the stars

Stars are not quiet, but rather giant musical instruments brimming with sound waves. High pressure inside the star ploughs through, compressing the gas as it propagates at the speed of sound. These pressure or sound waves wildly bounce inside the gaseous interiors, making stars quite noisy places. However, to us stars are mute because their sounds cannot travel in the vacuum that separates us.

These bouncing waves make the star quiver or “pulsate”. As it throbs, the swelling and contraction make the star cooler and hotter, causing periodic changes in its brightness which we can detect with our telescopes. Using basic physics and mathematics, these vibrations reveal secrets about the star’s interior in exquisite detail such as its rotation, magnetic fields, nuclear burning as well as its stage in life, mass, radius and age.

You are well aware, perhaps without realising, that the speed of sound is different according to the chemical medium it travels in. The hilarity of your voice as you breathe in helium at parties demonstrates exactly that. This is because sound travels three times faster through a vocal tract full of helium than it would through the heavier nitrogen-rich air we usually breathe. Thus the quality or timbre of your sound changes. The same thing happens in stars. As sound travels from a hydrogen-rich to a helium-rich medium, its speed -or the star’s voice- changes. This change tells us what the chemical makeup of its deep layers is. Just like your voice now is not the same as your voice when you were a toddler, a star’s voice changes too as it ages and its hydrogen transforms into helium.

A rhythmical throbbing

We see pulsating stars of different masses at essentially all stages in life. As a star swells and contracts, energy is damped and lost. So what feeds this relentless pulsation?

One driver of the continuous throbbing is heat. When a layer inside the star gets compressed by pressure, it heats up. It then converts its thermal energy to mechanical energy, acting as an engine that powers the pulsations.

Another driver is opaqueness. If a region in the star is particularly opaque, it blocks radiation from seeping through, so pressure builds up and the star swells. Its rising temperature reduces the opaqueness, allowing radiation to be released and the star deflates. Deflation increases opaqueness again and the same process repeats, quite periodically.

A third driver is resonance. It is thought that this type drives the Sun’s pulsations. Turbulent motions in its surface layers generate acoustic noise that can set it throbbing. Some scientists devote their research careers studying such oscillations. The Birmingham Solar Oscillations Network at the University of Birmingham, for example, runs a set of remote telescopes which monitor the oscillations of the Sun around the clock.

NASA’s Kepler mission, a highly accomplished planet-hunting machine, revolutionised asteroseismology by observing the minuscule dimming of the light of a wide variety of stars. It was retired only last October, when its science work was done and it ran out of fuel.

What do stars sound like?

That’s how we see the sounds of the stars, but can we actually hear them? You and Pythagoras would be thrilled to know that yes, we can. Just like we can’t normally hear bats but with the right detectors or “ultrasound ears” we can, shifting the sounds in the star by several octaves would make them audible. As intriguing as it is to eavesdrop on the stars, it remains an exercise for pleasure, not for science. You can hear a stellar music composition here.

Eavesdropping on Mars

Earlier this month, we experienced how deeply humanity resonates with the sounds of the Universe when NASA InSight lander picked up the eerie low rumble of the Martian wind. Its UK-developed ultra-sensitive seismometer includes sensors that can detect fluctuations at unimaginably small scales, shorter than the diameter of a hydrogen atom, or less than one-millionth the width of a human hair. Thus it could hear the wind on Mars, which is barely within the lower range of human hearing. The public heard it almost unadulterated, and it caused a stir. By stimulating a familiar sense, it establishes a human connection to this distant and vastly different environment.

Auditory stimulation, together with visual experiences, evoke feelings and make us aware about our position and movement in the spaces that we occupy. This is how we make meaning of ourselves, of each other and the Universe. This awareness informs our decisions and thus formulates our beliefs. Beliefs collectively shape our identity and our identity drives our behaviour. Perhaps we simply need to hear in order to thrive, believe and explore.

The Long Hand of Darkness

Mist lifts over the Boyne Valley in Ireland as the Sun dawns on the stone tomb Newgrange. A narrow sunbeam streams through the passage just above the entrance. It reaches the floor and slowly crawls towards the back of an ancient crossed-shaped chamber. The beam of the rising Sun expands, flooding the tomb of ancestral ashes and bones with light for 17 minutes. This Stone-age alarm announces the 355th day of Earth’s year-long journey around the Sun. Today darkness yawns and stretches over the North, its longest stretch of the year.

In a wheat field nearby, Aisling glances up to see the Sun tracing its shortest arc. It hasn’t escaped her that the arc has been steadily dropping lower and becoming shorter since June. Today it has reached its nadir, a point so low that it almost looks like the Sun rises and sets in the same place. The Sun seems to “be standing still” or “sol sistere” in Latin. It’s the solstice, the year’s shortest day.

Even though she’s occupied with fixing her tractor and preparing it for the coming spring, Aisling can’t help feeling low. It seems as if her mood is hanging on that arc the Sun traces as it crosses the sky. And the lower the arc gets the lower her mood drops. Yet today she knows she should be cheerful because it marks the beginning of the Sun’s steady climb towards the long, warm days of summer. On that bright note, she strolls back home to enjoy the warmth of her fire while she roasts some chestnuts. Having been in the crisp winter air for so long, sitting near the fire almost burns her face. So she tilts back on the back legs of her chair to distance herself from the flames.

Somewhere tens of thousands of kilometres above Aisling’s head, a satellite snaps photos of our planet which tilts on its axis away from the Sun, arrogantly distancing its northern cheeks from the blazing ball of fire.

The axis is an imaginary line going right through Earth’s centre from “top” to “bottom” around which the planet spins. This axis doesn’t stand up straight, it leans over about 23 degrees. At the winter solstice it happens that the North Pole is leaning back just like Aisling on her chair. As Earth orbits the Sun throughout the year, this tilted axis always points in the same direction, so a different part of Earth would receive direct sunshine. If Aisling’s dad comes and turns her tilted chair ninety degrees to either side, the side of her body would all be equally exposed to the fire. At some point during its trip around the Sun, both Earth’s hemispheres will be equally illuminated, like Aisling’s side. This is the equinox, when daytime and night-time are almost equal. If Aisling’s dad then rotates her chair another ninety degrees, the back of her head would be leaning towards the fire. When the North Pole is leaning as such towards the Sun, the northern hemisphere gets direct sunlight and it is the summer solstice. It marks its longest day of the year, around the twenty-first of June.

So today because the North Pole is leaning back about 23 degrees, the Sun stays below its horizon and it’s cloaked in a day-long shadow. This is as far south as the Sun ever gets and the northern hemisphere is cooler, thus winter arrives. The Sun spreads more light over the southern globe which is leaning towards it and celebrating the opposite extreme, its summer solstice.

This reduced exposure of the northern hemisphere to the Sun’s rays makes its winter solstice the darkest day of the year, but not the coldest. In a month or so, the oceans and the land slowly start to lose the heat that they stored during the warmer months, and a cold spell falls over the Northern land.

The winter solstice was a special day to ancient civilisations who revered the Sun. The ancient tomb Newgrange was built so that today its rays can stream in and light up the chamber of the dead where the nobles have been lain to rest. In the Karnak Temple in the Egyptian city Luxor it rises between the temple’s pillars and shines down on its shrine. And when the shortest day is over, the Sun sets over robe-clad pagan worshippers celebrating the day at Stonehenge, and Iranians eating pomegranates and watermelons while chanting Hafez poems to drive away the long night. Aisling slowly peels her chestnuts as the hand of darkness stretches long and heavy over the frosty night.

Image created by Amanda Smith.

Stellar atmospheres and their dietary requirements

Declaring that I’m an astronomer at social events never fails to cause a sensation.

Sat next to a starry-eyed historian at a College dinner last night, he asked: “how do we learn about stars?” as he picked through the salad vegetables on his plate.

Starlight which we observe using telescopes, I said, encodes a wealth of information about the star’s temperature, gravity, and chemical makeup. Telescopes collect parcels of light, called photons, like a bucket collects rain. In1610, Galileo used a simple tube with lenses which he called a spyglass to observe the sky and collect more light than his eyes could. Telescopes have developed a lot since then. Now they can be huge, costing up to hundreds of millions, even billions of dollars. The bigger the telescope, the more light it collects, thus the fainter the celestial objects it can detect such as planets, stars, and galaxies.

Starlight is made of photons with a spectrum of colours and wavelengths. An instrument attached to the telescope can sort incoming starlight by wavelength into a spectrum that we can study to decipher the information it encodes, using what is called spectroscopic analysis. Historically, the most prominent scientists in this field were women. This is because in the 1800s it was considered “inappropriate” for a woman to be using a telescope, so female astronomers were delegated indoor positions, like laboratories. Annie J. Cannon, alongside other female astronomers, spent almost an entire lifetime accurately analysing hundreds of thousands of stellar spectra at the observatory in Harvard. She manually classified a record of more than 200,000 stars.

How is a spectrum produced?

The star is encased in an atmosphere rich in elements that were either present when the star was born or formed later in its core and then surfaced. When starlight penetrates this atmosphere, the intensity of some of its components drops, and dark bands form in the spectrum.

Pointing to the plate of my historian friend, I said “So you have picked only the tomatoes from your salad”. “Yes I don’t eat leafy greens but I like tomatoes”, he replied.

I said “well then, next time if I have my back to the person dining next to me and I glance over and I see a plate with tomatoes missing and green leaves all piled up untouched, I suppose I would guess it’s highly likely that it’s you sitting next to me. Wouldn’t you agree?” He nodded expectantly as he munched the last tomato.

Similarly, the gas in the star’s atmosphere is relatively cool, thus hungry for light. It is ready to snatch a photon when it encounters one. It has a very particular taste, too. Hydrogen or sodium in the atmosphere, for example, would pick out specific photons from the spectrum. Hydrogen has a taste for photons in the red part of the spectrum, while sodium fancies the yellow type. Because we know the elements’ tastes from laboratory experiments, just like me knowing you fancy tomatoes, we can identify what’s in the stellar atmosphere simply from the missing photons in its spectrum, or its dark bands.

The chemical forensic evidence

This taste is as unique to each element as a fingerprint, there is no way we can get mixed up. Each element in the star’s atmosphere has atoms composed of nuclei orbited by electrons. An electron is like a highwayman. When it encounters a traveling photon with the exact energy it needs to promote itself to higher energy, it steals the photon and, understandably, gets excited. Thus the photon of that particular energy goes missing. This causes a dip in the light intensity or a dark band in the spectrum. The darker the band at a particular wavelength, the larger the concentration of the element “stealing it”. Thus this forensic evidence not only identifies the element but also its quantity.

The missing culprit

Now sometimes a problem arises. We observe a certain star and find things we do not expect.  For example, we observe a star that we know is not mature enough to have possibly made any barium. But we notice that the photons that barium likes are missing in large amounts from its spectrum! Where did the barium come from then? We suspect that it may be a contamination case, that the star has acquired it from a nearby mature star that produced it. This, in other words, indicates the presence of a hidden companion sharing its matter with the star we are studying.

At other times we find puzzling amounts of nitrogen for example. This makes us revisit the theory our models are based on and refine it for higher accuracy. Often we realise that we had oversimplified matters. For instance, we find that the fact that stars spin complicates the picture in ways we didn’t anticipate. This comparison between our model predictions and observations is a powerful tool to improve our understanding of how stars evolve. Still in some cases we would observe a chemical enrichment or depletion that we cannot yet explain. We call those “peculiar stars”.

“You are interested in the past human history”, I told my friend, “and I am interested in the past star history. By studying the chemical makeup of different populations of stars in the Milky Way, we construct the history of star formation across the entire Galaxy.”

My tale rested just as cheese and fruit were being served, with port of course, which is never to be put down during formal Cambridge college dinners, but passed along just like the hard-earned knowledge that we build up on every day.

“But wait, why only mature stars, as you called them, can make certain elements like barium?” he was curious to know. “That, my friend, is a tale for another long dinner”.

The life and fate of our mortal Sun

Today I woke up on the wrong side of the clouds. Having been graced with unusually genial sunshine for more than a month, today looks particularly grim.

“Return, alas! return, O radiance dear!

And drive from me that foul, consuming Fear”

pleads Bradamante in 16th century “Orlando Furioso”.

This got me thinking about our 4.6 billion year-old beast and her glittering head. She bewitchingly promises warmth and cheer and when she’s beclouded our moods flop like a wet towel. But what’s going on in that head of hers? At times she scoffs and flares up, spewing fiery flames. She is spotty and certainly has her moods. Last month a scientist even suggested she may be having a midlife crisis. But we’re certainly lucky to be around when she’s at her best, because in a few billion years, she will unintentionally melt our planet into a sticky blob before meeting her final demise. It’s all quite dazzling, to say the least.

Hot and fiery

A powerful furnace, her core is 15 million degrees. Things cool off away from the core to 5500 degrees Celsius at her visible surface which we call the photosphere. This is the layer where parcels of light, or photons, escape freely to outer space. One would expect things to keep cooling down the farther one is from the Sun but in the atmosphere, something very odd happens. The temperature starts to increase and peaks to more than 8000 degrees Celsius. Even higher up above the solar atmosphere, called the corona, temperature soars to a million degrees! This is because the solar magnetic field affects the way energy is carried around and dissipated through her very sparse and diffuse atmosphere. Despite the searing temperature, it’s not really “hot” because the density is very low. It’s like getting in a car on a hot sunny day. While the dashboard may burn if touched, sitting in the car wouldn’t really burn you. But hey, I’m not suggesting you can go sit in the corona.

The Sun is not idle, she spins. Because she’s gaseous, she spins faster at the equator than at the poles. Rotating once every 25 days at the equator, she takes more than 30 days to rotate once at the poles. So her magnetic field, bundling in tubes just below the surface, gets twisted and tangled and bursts out through the surface at certain spots. This slows down the emergence of sizzling material from the inner parts, making these spots cooler, thus look darker compared to their surroundings. We call those the sun spots. Sometimes the magnetic field gets drastically distorted so its lines get sheared off causing the most violent eruptions in our solar system, called solar flares. These flares are often accompanied by streams of supersonic winds and produce as much energy as a billion hydrogen bombs. When the solar wind reaches Earth a few days later, it can sneak into the Earth’s natural shield through its magnetic funnel near the poles. The energetic particles of the wind blast the atoms and molecules in the air, exciting them into that magnificent spectacle, the northern lights.

A midlife crisis?

It has long been known that the Sun’s spinning and her magnetic field have a very intimate relationship. Remember the streams pouring out of the surface that I just talked about? The particles swimming in those streams follow the magnetic field lines like ants on a pheromone trail. Upon reaching a large enough distance, they break free and carry away the rotational momentum or oomph they’ve stolen from the Sun. This gradually slows the Sun down, and is aptly called magnetic braking.

However, this picture seems to have changed only last month. Turns out that the Kepler Space Telescope has been spying on thousands of stars, and a few clusters too. It revealed that in certain clusters young members are very well-behaved. However, the middle aged members, particularly those of the exact type as our Sun, were not acting their age! They were in fact spinning too fast for their old age. They don’t seem to be slowing down either.

Their brakes seem to have gone faulty, and scientists suspect this has to do with the motion lurking just underneath the stellar surface, or convection. Things may very well be more complicated than we had thought!

The Inescapable demise

She will shine normally for the next several billion years but for us earthlings, life will be far from normal. Earth’s temperature will steadily rise making life more challenging before the final cataclysm arrives. In about 1 or 2 billion years it will be hot enough to boil most of our water and seriously destabilise our biosphere, turning our planet into an arid desert. A few billion years later, whatever has remained of our oceans will evaporate and Earth will be a barren lifeless planet, like Venus.

Well perhaps that’s for the best, because what’s coming afterwards is a hellish ordeal no human would wish to witness. In about 6 billion years, the sun’s core runs out of hydrogen and she will swell up into an angry fiery giant, swallowing Mercury and Venus. She will melt our planet into a blob of magma, even Mars will not be habitable, and distant icy worlds like Uranus and Neptune will start to defrost.

Things will only continue hell-ward from there. Eventually the helium in her core, the product of burnt hydrogen, will run out too. Like a desperado with nothing left to lose, she’ll rage into a giant once again and that’s the point of no return. Ripping herself apart in despair, she will tear away her layers into glowing rings of gas and dust, or planetary nebula, that drift away in the wind. This tragedy will only spare her Earth-size beating heart, an abandoned naked inanimate object called a white dwarf. Left to its fate, it will cool and fade away into the dark as the solar system turns into a chilly, forsaken place.

Thus the tragedy unfurls and the rest is silence..

The dawn has now cracked and its light is streaming in through my window. I shall soon stroll to the beach and bask in the golden shimmer of our Sun, before it’s too late.

Image credit: The Economist

A journey from your backyard to the stars

Last time you lay down in your backyard gazing at a night sky studded with twinkling lights, could you imagine them being born, living eventful lives then fading away and donating matter back to the Universe, matter which may form new stars and planets one day?

As you lay there, did you wonder why some people spend their lives studying stars?

I’ve been studying them for the past ten years. True story! Tax money pays my salary, so I can’t help but wonder, how does society feel about the stars? Does society even care at all?

If you’re undecided, here are a couple of interesting facts that perhaps you never thought of before..

In the spiral arms of a galaxy far, far away, lives a giant cold cloud of gas and molecules called a nebula, hundreds of thousands the mass of our Sun. The nebula gets blasted by a shock wave from a nearby star or event which sends things tumbling. Over millions of years this giant cloud fragments itself into smaller clouds of dust and gas which collapse and get pulled closer and closer by gravity. The core of a cloud gets denser and hotter and eventually becomes the kernel of a new-born star. This settling core radiates in the infrared, before it gets smothered by new layers of infalling matter which increases its mass.

Meanwhile, the cloud continues to churn around the young forming star. As it collapses it swirls faster and faster much like an ice-skater as she pulls in her arms closer to her. It eventually flattens out into a thin disk of gas and dust called a “circumstellar” or “protoplanetary” disk, because it’s a source of planetary systems. It hosts swarms of clumps of matter that sweep up surrounding material which grow into embryonic planets or “planetesimals” and later become mature planets that go on hugging close to their parent star. A planetary system is thus born.

So you see, stars are the birthplace of planets, of fascinating new worlds. By studying the star one can learn about the history of its planets, their nature, chemistry and the atmospheres they are likely to have. Are they habitable? Can they sustain liquid water on their surfaces? Are they tucked under a stable atmosphere? Do they harbour a biosphere or are they barren lands, torched by their host star’s activity?

All these answers require a careful understanding of the host star. Even more, the evolution of life on planets, or abiogenesis, needs the light of the star!

The planets scientists have found so far seem to be vastly diverse. We have no reason to think otherwise, but we’ll leave that for another story.

As stars mature over billions of years, they become beacons in the darkness of the Universe. They illuminate their surroundings and are easy to detect in the Galaxy, even in outer galaxies millions of light years away.

While they illuminate our Universe, they unleash their energy and radiation into their surroundings. Fast winds and streams of charged particles traveling at several million miles an hour energise their host environments. If embedded within a larger cloud, the scorching ultraviolet stellar radiation blasts loitering gas and dust and sculpts them into huge fertile pillars which mediate the creation of new stars. Their winds spew enormous amounts of material synthesised in their hot interiors and infused with chemical elements. This enriches their medium with elements heavier than the hydrogen and helium of which they are mostly made.

In order to survive, stars need to counterbalance gravity by burning nuclear fuel in their cores. Their generated energy seeps to the surface in two ways: radiation and the physical motion of charged stellar material, called convection. This motion of plasma weaves strong magnetic fields.

This is why stars are threaded with magnetic field lines.

A magnetic field pushes stellar material to the photosphere, creating coronal loops and star spots like those observed on our Sun. This magnetic activity affects space weather which influences our planet, electronic equipment and astronauts in space, and even staffed missions to the moon or to Mars.

Ending our journey in the stellar core, we reach the origin of our stellar ancestry. This is where stars forge all the chemical elements found in the Universe except for hydrogen. The Big Bang created the hydrogen, most of the helium and traces of lithium. Everything else is the making of stars, including the carbon and oxygen which make all living organisms.

Thus stars are our intimate connection with the cosmos and exploring them is an exploration of our own cosmological heritage.

Stars never cease to fascinate. When you study them, you can make predictions about their lives, and the life of the Sun and the galaxies.

Can you now see how stars are the atoms of our Universe and the core of most of its events? Do you now care slightly more about them? Can you feel our curious and fascinating connection? I bet you will never see them the same way again.

They are certainly not boring balls of fire. They have their own lifestyles, relationships, and body language. If you only knew the secrets of their lives, you’d be orbiting them endlessly like a planet. But that’s a different story, for the next time our star goes down…

Image: NASA-Langley.