Bart and Bert were fascinated, and even a little scared, by the news on the newspapers of those days. It was the meeting of the century, as they reported, when a comet of enormous dimensions would hit the planet Jupiter. The meeting was scheduled for the middle of June in 1994, not far away, therefore.
- It's the end of the World! - Bart was pretty scared.
- No way! A simple comet, and at that distance, it cannot cause us any harm... Perhaps the shock can't even be seen here on Earth... - Bert, was calmer, and more thoughtful, tried to clarify, although with a certain insecurity , because astronomy was not his forte.
- I don't believe!
- Well, if you have doubts and in this case I do too, because astronomy isn't electronics, there is only one person left for us to talk to... - Bert didn't even finish because Bart completed the sentence:
- ... Professor Ventura!
For many students at the technical school, Professor Ventura was just an unusual master of electronics, computers and mechatronics, but for those who were fortunate enough to share his knowledge, it was in common agreement that what he knew went far beyond electronics! It was the case of astronomy, which the professor cultivated with a certain love, keeping in his home, in addition to a powerful 7.5 cm refracting telescope, powerful 10 x 50 binoculars, and a whole series of artifacts to locate the most diverse celestial "observable" objects from his city, and even a camera adaptable to the telescope and permanently "loaded" with a very sensitive film, especially for astronomical work. Few knew that the professor had even collaborated with articles and photos in specialized magazines ... (*)
Bart and Bert, however, knew that the professor knew much about astronomy as well as electronics, which meant he was the right person to answer their questions.
The professor welcomed them, and after hearing their doubts, he settled on an old chair in his laboratory. The two boys took up stools in front of him, ready to hear the explanations.
- I know the subject has nothing to do with electronics, but as we know that you can explain to us... - Bart did not finish his sentence. He was interrupted by the teacher.
- How on Earth it has nothing to do with electronics? Who said that? - The professor looked angry. The boys did not understand very well. How can such a distant cosmic event, a collision of a comet with a planet, has something to do with our "dear and well known" electronics!
The professor noticed the air of astonishment on both their look.
- Don't worry, I'll explain!
The two settled even better preparing to take in the explanation that was about to begin. The possibility of electronics being involved in their "business", made them even more interested. Slowly the teacher started his explanations and, as always, in a way that allowed everyone to understand everything. He really started from scratch:
- When we studied radio waves, we gave special emphasis to short waves, explaining how, thanks to the ionosphere, they could reflect back to the Earth and then back up, reaching huge distances. We also studied how the Earth's rotation movement creates a magnetic field. Do you remember that?
Bert then showed that he remembered the explanations perfectly:
- Yes, you explained that the hot, liquid metal in the Earth's interior produces a generator effect when it spins. The Earth's rotation movement, "carrying" this huge liquid metallic mass, causes intense electrical currents to appear, which in turn creates a magnetic field.
The teacher continued:
- Yes, and this magnetic field is what makes us have the orientation of the compass and, at the same time, the production of the aurora borealis. Around Earth, this field manifests itself by "directing" the particles charged with electricity, especially those coming from the sun, which then deviate along a spiral path towards the poles. Upon entering the upper atmosphere, these particles ionize the air, creating colored lights that we also call "the northern lights".
The two boys then remembered watching a film shot near the North Pole in which the natives (Eskimos) showed foreigners the wonders of colored fringes in the sky, during a phenomenon of the northern lights that is spectacularly more intense when occurs the phenomena of solar flares. When this happens, an enormous amount of charged particles of electricity are launched towards Earth.
The teacher continued:
- Both the ionosphere and the Earth's magnetic field have something to do with the fact that our planet has a hot, liquid metallic interior and rotates quickly.
- But aren't the other planets like that, too? - Bart, with little knowledge of astronomy, had his doubts.
The teacher, without being too bothered by it, went on:
- There it is: our Moon, which seems to, in addition to being small and slowly rotating around its axis (once every 28 days, as the rotation coincides with the translation), not have an important liquid core. Our satellite has a negligible magnetic field, and because it has no atmosphere it also has no ionosphere. The ionosphere is precisely formed by charged particles that come from space and penetrate the upper atmosphere, removing electrons from the air, that is, ionizing them. The same is true of the planet Mars.
Approximately half the Earth's diameter, it apparently does not have a bulky liquid core (very little sign of active volcanoes exists on its surface, which would indicate the presence of a liquid core). Although its rotation period is more or less the same as the Earth's (24 hours), the lack of a nucleus and an atmosphere makes it have a very weak magnetic field and perhaps no ionosphere...
Bert interrupted for a moment:
- We are reaching Jupiter, which is next, and interests us.
- Yes, that's right! - continued the teacher - With Jupiter things are quite different. Jupiter is the largest of the planets. It belongs to the group of outer planets, or giants, which also have elements like Saturn, Uranus and Neptune. They are all larger than Earth, in reality much larger than our tiny Earth.
Bart liked this kind of reasoning and commented:
- What fascinates me about astronomy is that when we study it deeply, our Earth becomes increasingly small and miserable! Sometimes I wonder if astronomy doesn't make astronomers depressed: with each discovery, Earth becomes smaller and smaller ...
Maybe Bart was right, but the interesting thing about it is that every time that happens, we wonder why exactly do we have the gift of discovering all this? The teacher continued:
- Jupiter is a giant, with a diameter 11 times greater than the Earth's. Its volume is more than 1100 times that of our tiny planet. However, the material from which it is made as a whole is lighter. Thus, its mass is only a few hundred times greater. In fact, it is so light that if there was an even bigger planet in our imagination, with an ocean capable of containing Jupiter, it would float!
- What the hell is this material, to be so light? - Bart's question deserved an immediate answer:
- Actually, Jupiter has all the materials that Earth has, but the lighter ones are in greater quantity. Knowing the nature of a star that is more than 600 million kilometers from Earth is a difficult job, but thanks to the instruments and space probes sent to Jupiter, today we have an image close to the reality of what the Earth's big brother should be... Jupiter has a hot metallic core, perhaps similar to the Earth's, but warmer and larger, they even say that it may be a pre-star!
- Pre-star?
- Yes, a star whose interior is so hot that the nuclear reactions that produce light and heat almost occur, just like the Sun! But, going back to the constitution of Jupiter: around it, there must be the same lighter materials, such as silicon and aluminum, forming a still warm layer and then the elements that are not common here on Earth.
The teacher made a dramatic pause, and continued:
- On very large planets, such as Jupiter, Saturn, Uranus and Neptune, strong gravity can retain even the lightest gases, such as Helium and Hydrogen. Earth has lost almost all of these gases, leaving them to escape into space during its formation, and in the millions of years of its age, so that its atmosphere is made up of heavier gases, such as Nitrogen and Oxygen (which was released by the plants). Not on Jupiter: a lot of Helium and Hydrogen is the main feature, and these gases are combined, such as Oxygen, Nitrogen, and elements like Carbon, forming gases... methane, ammonia, formaldehyde, etc.
- Wow! An atmosphere of ammonia with formaldehyde! What a bad nasty place to be! - Bert's observation was interesting. The teacher took the opportunity to take a breath.
- In fact, there are many more unpleasant things for a terrestrial visitor on Jupiter. To begin with, the very gravity itself, as we descend towards the surface, becomes greater. A person, if one finds a solid surface on Jupiter, would weigh several tons and die crushed by their own weight!
- A mandatory diet planet! - Bart said that hitting Bert's bulging belly.
- Continuing... Jupter's atmosphere is very thick. In fact, we have no idea where it ends, because as we go deeper, the pressure is so great that the gases become liquid, perhaps existing, covering the surface of Jupiter, a huge ocean of ammonia with formaldehyde. Digging deeper, the pressure of millions of atmospheres may cause these materials to solidify, which would then form some kind of "crust".
- Wait a minute! - interrupted Bert trying to reason - But, where is electronics in all this?
The professor gestured to Bert calm down and explained:
- It enters right now: a gigantic planet, with a liquid metallic core, with violent phenomena, in a thick and fast-moving atmosphere (Jupiter rotates on its own axis every 6 hours, and as it is much larger than Earth's, meaning a much higher tangential velocity) has to present very important electrical phenomena, which are precisely the ones which interest us.
- Now I see! And... What are these phenomena? - Bart was now more curious.
- As I said at the beginning, Earth has an ionosphere and a strong magnetic field, precisely because it has a thick atmosphere and because it rotates quickly. Multiply that a few dozen times and you have what happens on Jupiter. In addition to a gravity which attracts everything that passes close by in space, Jupiter also has a powerful magnetic field and perhaps a very important ionosphere. This strong magnetic field, and the existence of an ionosphere, make Jupiter behave like a gigantic spatial signal generator. Intense currents of electrons, and other particles, circulate around the planet generating radio waves. Jupiter is a gigantic radio transmitter which concentrates much of its energy from the 18 to 30 MHz range!
- Short Waves! I didn't know that! - Bert, always interested in telecommunications, expressed his astonishment.
- In fact, at certain times, the emission of signals from Jupiter, on this range, gets to be stronger than that of the Sun itself, which is thousands of times bigger and hotter! We can say that, here on Earth, the signals reaching us, most strongly at certain times, are precisely those emitted by Jupiter.
- Is it possible to pick up such signals? - Bart's curiosity increased, because he was now talking on radio waves.
- Yes! With a good directional antenna and a communication receiver, which has a sensitivity of at least 1 microvolt, it is possible to "hear" Jupiter.
The boys' surprise was great:
- Well, then, to capture Jupiter's signals, it is not necessary to have those big satellite dishes from radio telescopes.
Taking a book from the shelf, Professor Ventura brought some more news:
- Look! This is a Radio Astronomy book for amateurs, published in the United States (Radio Astronomy for The Amateur - TAB BOOKS N. 714), and shows how to adapt a simple "receiver" which has a short-wave range, and with an antenna system, which even fits in the backyard, to record the signals from Jupiter. Many amateur radio astronomers use simple techniques to explore waves from distant worlds, showing that Science can be done with simple resources!
At this point it seems that the two boys have woken up. The question was from Bart:
- But what does all this have to do with the comet?
- Add the ionosphere, the magnetic field, the thick atmosphere, the powerful gravity, powerful radio emissions to a comet that is passing by, carefree around, and things start to happen!
Bert made one more observation:
- Wow, I'm starting to understand! The comet is attracted, enters the atmosphere violently and, as a result, affects magnetic fields and Jupiter's own ionosphere causing also electrical phenomena, perhaps huge radio emissions, which will easily be captured on Earth, or perhaps interfere with our telecommunication systems, right?
Bert reasoned quickly, and this allowed him to reach conclusions easily. He was right again, but the final explanations had to come from Professor Ventura.
- Let's imagine then this sequence of facts, as if filmed by a camera placed on a spaceship at a safe distance. - The professor made a gesture, as if he had a video camera on his hands and continued:
- A comet is nothing more than a huge rock, some tens of kilometers in diameter and covered with certain "impurities", such as ordinary ice, dry ice, dust particles, etc. Since its diameter is small to have an important gravity, between a few hundred meters to a few hundred kilometers for the largest, this material remains agglomerated, more due to the low temperature than to anything else. But where do comets come from?
The teacher was abrupt in changing the subject, including a question, and looking at the boys who promptly answered:
- From space, of course!
- Yes, but where in space? - The teacher insisted, and as the two could not say, he explained:
- In space there is a large number of small bodies which can have the most diverse origins, according to astrophysicists, such as, for example, remains of the formation of our Solar System, remains of star explosions, etc. Most of these remains, which roam near stars or planets, end up losing their "light" part, that is, ice and dust, and become asteroids, eventually falling on planets and stars, or wandering around them like asteroids, planetoids and even satellites. Large planets like Jupiter have several satellites which may have this origin.
The professor got up and went to a blackboard where he sketched a representation of the Solar System, with the nearest stars. The Sun occupied, represented by a ball, a central position and, around it, the planets rotated. The distant stars were also polka dots, with some having their own planets around. Professor Ventura took a breath to continue:
- However, between the stars, that is, between the Sun and the nearest stars, beyond the confines of Pluto, at several tens of billions of kilometers, there is a region where the bodies in it are very loosely attached to the gravities of the bigger stars, a kind of spatial "limbo". A body in this region would be in an "indefinite" condition, in which it could not be said whether it belongs to the Solar System, or to the nearest star (Alpha Centauri), for example. The temperature in this place is also very low, as it would be very far from the heat of the sun or any other star. In other words, a comet in this region would remain intact or "frozen" for billions of years.
- A comet incubator! - joked Bart.
- Yes, that's right! A Dutch astronomer, named Oort, was the first to indicate the possibility that in this region of space there are millions of "frozen" comets, or in the process of "incubation", waiting for their turn to manifest.
- But how does a comet "wake up" from hibernation?
- A small gravitational disturbance in Oort's region and that's it: a sleeping comet "falls" towards the nearest star, accelerating more and more as gravity becomes stronger.
- Wow! Coming from so far, the speed it can acquire is enormous! - Bert's statement had its logic. The teacher did not stop with the sequence of explanations.
- It is easy to calculate the speed that the comet reaches the Sun, it is the escape velocity of the system. In Jupiter's region, this speed is between 80,000 and 200,000 kilometers per hour!
- Wow, it's a huge speed!
- If no planet "attracts" the comet, making it its own satellite, the comet has two possibilities: it falls in the Sun, being destroyed, or makes a quick turn in its vicinity to return to space. Depending on this turn, it can start rotating periodically, approaching the Sun, as Halley does, or it can return to the ends of the universe and never come back. The Sun functions as a gravitational "catapult" in this case.
The teacher raised his finger for an interesting warning:
- A third important possibility that occurs in this "visit" of a comet is that if it gets too close to a planet of great gravity, like our Jupiter, it can be captured or destroyed, that is, it breaks into many pieces. The comet that will now fall on Jupiter, in its previous orbit, has already shattered, and what we will now have in reality will be a "rain" of fragments and not exactly a direct impact!
All comets have a tail, or at least they must have, and this detail was not overlooked by Bart, who was impatient, as the professor had said nothing about it.
- But what about the tail?
- Yes, we got there: when the comet is frozen, nothing happens, but as it approaches the Sun its temperature increases, and the material on its surface begins to detach itself, evaporating or being pulverized. The traditional tail is then formed.
- Really! Every comet leaves a tail behind! - Bart's statement led the professor to a censure:
- Not behind! The sunlight exerts pressure, and the material detached is "pushed" away from the Sun. When the comet approaches the Sun, the tail really stays behind, but when it goes away, the tail goes ahead! Have you ever heard of the "solar wind"?
Bart gave a negative nod. The teacher continued.
- So, in our case it matters what will happen to this comet that is going towards Jupiter. Let's shoot the scene!
The professor shifted his position on the chair:
- Attracted by the Sun, our comet left Oort's region a few thousand or even millions of years ago and has already made some orbits around the Sun. However, with an extraordinary gravitational force, Jupiter ended up changing that comet's "route". The change was such that in a first pass very close to Jupiter and after the Sun, it shattered and was "captured" by the Solar System. A recent photograph taken by the Hubble Observatory, in orbit around Earth, showed that the comet is actually made up of more than 20 pieces. Then, in a second orbit, the possibility of a shock was discovered! And, this shock is scheduled for a date between the 18th and 21st of June, 1994!
- It's the end of the World! - Bart joked.
The boys then imagined the scene, perhaps as in a George Lucas film, with many explosions and fragments launched into space. The teacher continued:
- Evidently, as the comet comes from the ends of our system, its shock on Jupiter must be "behind" in relation to us, since Jupiter is an external planet.
- I did not understand! - Bart was unable to follow the reasoning. The teacher decided to explain better:
- Jupiter is between us and the comet. This means that the comet coming from far away towards the Sun will hit it, not on the face that faces us but on the other side.
By making gestures and showing the drawing, the teacher managed to convey the idea. He continued:
- When the comet approaches a few hundred thousand kilometers from Jupiter, things will already start happening. At this stage, it will have some tail, resulting from the evaporation of the lighter gases, which also help to expel some dust.
- The comet, or better saying its pieces, as the Hubble photographs showed, still has a lot of gases and dust remaining from the last passage. - Bart interfered, because he had read this in the newspaper.
The professor continued, not bothering much with the observation:
- When the fragmented comet reaches the upper layers of Jupiter's atmosphere, friction will heat up and ignite these pieces which will tend to explode, fragmenting further. This heating ionizes the gases in the atmosphere, thus producing a true "short circuit" in the planet's ionosphere, due to the dimensions of the phenomenon. The signals produced, due to their intensity, may already be detected on Earth, considering the time it takes to get here, of some tens of minutes.
- So, it would be very important, not only to observe the phenomenon visually, but also to be attentive to the electromagnetic signals on the short wave band emitted by the planet at this time.
- Yes, that's right Bart! But the phenomenon does not end there. Penetrating deeply into Jupiter's atmosphere, the pieces of the comet cause immense shock and heat waves which can be compared to many atomic bombs bursting simultaneously and, who knows how, they reach the liquid and then solid part of the planet. A mark or more, perhaps similar to Jupiter's famous "red spot" is produced.
- Red spot? What is it? - Bart, knowing little about astronomy, had never heard of Jupiter's most famous "landform".
- Jupiter has a thick atmosphere and nothing can be seen from its surface, which we barely know if it has liquid and solid regions, and to what depth. So, all we see on that planet are bands of clouds that constantly change. There is no fixed detail on Jupiter, such as the contours of continents, such as on land, mountains and valleys in the light, etc. However, there is a single object that has remained constant on Jupiter's surface for many years: a red-orange stain, some tens of times larger than the Earth's, and whose origin we cannot fully explain.
- A huge stone? - It was Bart's guess.
- Evidently not! It is not believed that on the surface of Jupiter a structure of such dimensions can remain solid and visible in that way. The assumptions are that it is an "opening" in the atmosphere which allows us to see the hot interior of the planet, or turbulence in the lower layers of the atmosphere, where a comet might have fallen thousands of years ago.
- And... Can the phenomenon repeat itself now?
- Exactly! Bert is right, and that justifies our interest on this impact. Then returning to the comet's fall, which we interrupted "in the middle", what can happen is that this shock wave "opens a hole" in the atmosphere, exposing the point of impact thousands of kilometers below, where a fantastic explosion is going to occur with the production of lots of heat.
- And we won't see that! - Bart's disappointment had an explanation. Again, the teacher came into action:
- Yes, but not now. As I explained, the impacts occur on the face which is opposite to the Earth's. But the fantastic results of the explosion will remain for a long time, and in less than 3 hours, with the rapid rotation of the planet, the site of the impacts will be appearing to us. Then it will be possible to see what happened: probably, a huge opening in the atmosphere, with an emission of light due to the remaining heat, and the results of the shock wave which will propagate throughout the planet!
- What about the electrical phenomena?
- They will certainly be phenomenal! - commented the professor - A huge, short circuit in the ionosphere, and the turbulence of atmospheric currents, should generate monumental electrical discharges, that is, lightning. These will be accompanied by the emission of waves across the spectrum, of course with a concentration on the lowest frequencies that will reach us. This turbulence should last for days, weeks or even years, with intense electrical activity.
- But what about the destruction of Jupiter? Is there any possibility?
- Of course not! The integrity of the planet is in no danger. Even hitting Earth, a much smaller planet, a comet like this could at most shake life, and it is what is thought to have occurred when the dinosaurs were destroyed. Jupiter, however, has no known life, and very little permanent solid to be destroyed. We will only have the movement of large masses of matter and a lot of energy, which will certainly have some effect on us.
- Like a shot in a jelly ball! - Bart's comment worked very well to describe what was likely to happen in general terms.
The observation of all this, in practice, however, is what most affected Bart and Bert's curiosity.
- And what would be the chance to see all this?
The professor gave some hopes:
- Even though it is a phenomenon of enormous dimensions, the distance from Jupiter to us cannot be considered small. The six hundred million kilometers we have there, in the best conditions, and now it is a little further away, does not make things much easier for those who want to make an observation.
- What kind of instruments do we need?
- With a small telescope, enlarging it about 30 times, and with a 5 cm lens, Galileo discovered Jupiter's 4 largest moons! A small telescope already allows you to see Jupiter as a pea or even a marble, and in very favorable conditions we can, with an increase of 100 to 200 times, and an objective of at least 7.5 cm to see some bands of clouds because it is difficult to predict exactly what can happen. The observation of details, however, must be left to the large instruments of the observatories.
- Does that mean we have more chances with the radio? - Bart could be right.
- To tell you the truth, I think we would have a better chance of discovering something by connecting a good shortwave receiver to an antenna and tuning it out of station, connecting it to a graphic recorder or an ADC, analog-to-digital converter, at the input of a computer, with a data acquisition program, than looking up, even with a good telescope. (*)
(*) The article is from 1994
- Wow!
Professor Ventura's explanations were more than enough to give a real picture of what was going to happen. If this was really the case, and what results science had with the observation of the phenomenon, it is up to the reader who can prove what we said in this written story a few months before the scheduled day of the real impact.
