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Ken Tapping –
May 10, 2019 / 11h00 | story:
255938
Photo: sd.gsfc.nasa.gov
In the 1960s, Canada was the first country to successfully use a radio telescope several thousand kilometers in diameter.
A technique has been developed to ensure that several radio telescopes, separated by thousands of kilometers, act as if they were assembled.
This technique, called Very Long Base Interferometry (VLBI), was developed for one main reason: to find out what the quasars really are.
However, it also became very useful for something completely different: measuring the changing shape of the Earth.
The level of detail of an image is dictated by the size of the mirror or lens used to make it, compared to the length of the imaged waves.
As the light waves are very short, our ocular lenses, a few millimeters in diameter, allow us to see details representing only 1% of the surface of the lunar disk.
To record the same detail for waves of a few centimeters or several meters, the lenses or mirrors must be huge.
For example, our Synthesis radio telescope, which can produce radio images with levels of detail achievable with our eyes, consists of a row of antennas 600 meters long.
We can increase the ability of our eyes to discern details using a telescope or binoculars. These have the effect of making the pupils bigger. However, it is difficult to do with radio telescopes.
Modern science and engineering materials can provide us with satellite dishes up to about 100 meters in diameter, but not larger.
In the 1960s, a strange class of cosmic radio sources called quasars was detected. They were very small and looked like stars through our larger optical telescopes. They are millions, even billions of light years away.
Most of their strangeness lies in the radio programs they produce, so we wanted to make radio images of them. We now believe that they are driven by black holes.
Cosmic radio sources seem so small in the sky that most of them exceed the imaging capabilities of even the largest satellite dish telescopes. This has led to the development of techniques for combining groups of small radio telescopes into larger networks than any single radio telescope.
Over time, most radio sources were imaged, but the quasars remained unimaginable. We needed even bigger paintings. However, the telescopes of a network must be connected together, which limits these networks to perhaps a few kilometers in diameter.
Even the larger networks were inadequate to handle the quasars.
Something completely new was needed. Could we make tables without having to connect the antennas together? There was an international race to get there. Canada came first.
The idea was to record on videotape the signals received by different antennas. The bands of the different antennas would then be collected for processing.
To make this extremely accurate, timing signals have been added to the tapes. Antennas could now be anywhere on Earth.
A picture of the size of the Earth gave us usable images. This is the technique that recently gave us our very first images of a black hole.
A really useful byproduct of these VLBI experiments is a measure of the position of the antennas, including distances separating them, with an accuracy of a few millimeters.
By installing antennas on different continents, we can measure how fast the tectonic plates move and how the land masses stretch, twist, or change shape.
This works well because the small size of the quasars, which makes them extremely difficult to visualize, also make them ideal reference sources for measuring the position of the antennas.
Our obsession with quasars has given us the ultimate rule for measuring our world.
- Mars is very low and unobtrusive to the west, sinking slowly into the twilight.
- Jupiter, shining like a projector, rises around midnight
- Saturn rises at 2 am
- The moon will be full on the 18th.
Ken Tapping –
May 6, 2019 / 11h00 | story:
255516
Photo: extremetech.com
Until recently, one of the jokes twisted on Fast Radio Gusts (FRB) is that the number of theories attempting to explain them was larger than the number of FRBs detected.
The CHIME radio telescope (Canadian experience of hydrogen intensity mapping) is changing the game. This instrument has a huge field of vision – much of the sky – and captures a lot.
Hopefully this will lead us to have a better idea of what they are. All we know for the moment is that very short bursts (in milliseconds) of radio broadcasts reach millions, even billions of light years away.
The energy transmitted must be enormous, so big that the only engines we know can drive them are neutron stars and black holes. We hope that the number of theories will begin to diminish soon.
Theories are the currency of science. Coming up with a new theory is a lot more than having a casual idea to explain something we see. The first step is to observe something and imagine a physical process or a set of possible physical processes to explain it. This could be a casual idea.
Science begins at the next stage. This involves looking in the literature for further work on the subject, and then using them to flesh out the idea of generating a consistent set of physical and mathematical arguments to account for what has been observed. This is not the end of the story.
This new theory must make predictions. If that is the case, other consequences may be sought. The theory must predict things that can be tested. If this is not the case, it is not an appropriate theory and is useless.
If a theory survives a long period of extensive testing and testing, it can finally be recognized as a "law" – one of the fundamental rules Mother Nature uses to manage the universe.
Isaac Newton has provided us with good examples. He proposed a simple theory. I
If you push something with constant force, an object will accelerate at a constant speed.
If you double the mass of the item, it will speed up to half that rate.
On the other hand, if you push with twice as much force, the object will accelerate twice as fast.
The consequences of this simple idea are now recognized as the laws of Newton's movement.
He also theorized that objects attract with a force related to their masses and the distance that separates them. He had the idea of gravity.
Expressed mathematically, Newton's laws of motion and gravity have been successfully tested and used, and are now recognized as fundamental laws of nature.
This is why scientists are so unhappy about dark matter concepts and black energy.
When we have seen that in most galaxies, orbiting stars are moving too fast, we have concluded that galaxy masses are much larger than we thought. However, we can not see this missing mass.
Someone has suggested that this invisible mass is made up of dark matter, a "something" otherwise totally invisible invented to make sense of our measurements.
The expansion of the universe is accelerating. It does not make sense. If all objects in the universe fire on all other objects, gravity should slow down the expansion.
The only way to accelerate expansion is if an unknown external force is at work.
Enter the idea of black energy. As in the case of Dark Matter, we have just given a name to something, we have no explanation or line of analysis to follow.
It could change. The CHIME radio telescope is intended to map hydrogen in the very young universe. This is when black energy would be very active in creating the first galaxies to form.
This will not necessarily lead us directly to a theory, but at least it could give us a way forward.
- Mars lies to the west after sunset.
- Jupiter gets up around midnight
- Saturn rises at 2 am
- The Moon will reach the first quarter on the 11th.
Ken Tapping –
April 29, 2019 / 3pm | story:
254936
Photo: peterlachnewinsky.wordpress.com
Dust may not seem like a very exciting topic compared, say, to black holes, but in reality, that's it.
It is not only the raw material for creating new planets, asteroids and other bodies, but also an environment conducive to all kinds of other important and fascinating things.
Most of us have suffered from sunburn. This is because overexposure to the sun's ultraviolet rays damages the complex organic molecules that make up our skin. Moreover, it is after our atmosphere has filtered most of these dangerous radiation.
However, in recent decades we have discovered that space can be loaded with rather complex organic molecules.
How can this happen?
In addition to being very cold and near vacuum, the space is flooded with ultraviolet rays. The answer is surprising, dust.
In most places, the space is clear enough, which allows our telescopes to reach far into the space and back in time until almost the beginning of the year. # 39; universe.
However, in some directions, we see large clouds of dust, thick enough to block the light from the stars behind.
It's summer, if you are somewhere with a dark and clear sky, look in the southern sky. You will see the Milky Way apparently split into two streams. Of course, there is actually only one stream, but there is a thick belt of dust in the middle that blocks the stars.
Inside these clouds of dust, the ultraviolet is blocked and it is very dark and very cold. Through previous generations of stars, clouds are loaded with all the elements produced as waste by these stars.
This makes clouds of excellent places for chemistry. At such low temperatures, chemicals react very slowly, but there is still a lot of time – billions of years. The result is an incredible infusion of organic chemicals.
Ultraviolet light penetrating the outer part of a cloud can break a molecule into fragments. When this occurs in the warm and dense atmosphere of the Earth, these fragments will not last long.
Inside these dark, cold clouds, things are moving slowly and the risk of colliding with something is low. Thus, fragments can slowly diffuse deeper into the cloud.
If, by chance, two fragments meet, they will certainly snap up, like billiard balls.
In this scenario, with collisions infrequent and unlikely to result in the formation of larger molecules, reaction rates would be very low. This is where the dust comes in.
It provides some chemical reactions somewhere. The rough surfaces of the dust grains provide many opportunities for the fragments of molecules to bounce off until they settle on the surface.
There they sit while other molecular fragments accumulate slowly. Chemical reactions take place and the grain is covered with complex organic molecules.
Then, when a cloud becomes unstable, collapsing under its own gravity and forming a new planetary system, these planets receive a ration of organic molecules that can, under good conditions, form the basis of life.
This is why there are more hours devoted to the study of dust in the optical and radio telescope than those devoted to research or black holes.
We search for the radio and infrared signatures of organic molecules in clouds and try to deduce the reactions that occur slowly, then we examine these clouds of dust when they form protoplanetary disks, the beginnings of new systems. planetary.
The current situation is that we find many more molecular signatures in these clouds that we have managed to identify. Whatever the recipe of life to which we think, the ingredients are probably present, provided that the conditions of the new planet allow it.
We know that it happened at least once.
- Mars is low and unobtrusive to the west, sinking slowly into the twilight as he heads to the other side of the sun.
- Jupiter, shining like a searchlight, gets up around 1am.
- Saturn gets up at 3 am
- The moon will be new on the 4th.
Ken Tapping –
April 22, 2019 / 11:00 | story:
254451
Photo: Horizon telescope of the event
This is an image and not a photograph, created by the Event Horizon Telescope project of the Messier 87 black hole. Using a network of eight telescopes On the ground around the world, EHT has collected data to produce the image.
We have just seen one of the most important astronomical images come out in years: the image of a black hole.
It shows a black and circular drop surrounded by a shiny ring of hot material. The calculations of Albert Einstein and others suggest their existence, and we have indirect astronomical evidence, but this is the first time we see one.
This triumph is the result of an international effort involving eight radio telescopes. The black hole of the image is 55 million light years away, at the heart of the 87 Messier galaxy, in the constellation Virgo.
It has a mass of about 6.5 billion times that of the sun and is bigger than the solar system. Black holes exist because of two things:
- a process called gravitational collapse
- space-time is considerably deformed by strong gravitational fields.
Matter, as we see it every day around us, is composed of atoms. Each of these consists of a nucleus, a collection of protons and neutrons, surrounded by a cloud of electrons.
However, the main ingredient is simply an empty space. Here on Earth, atoms are not usually compressible. However, in stars and galaxies, this is not true.
When small stars like the sun run out of fuel, they collapse and the weight of the infiltrating matter compresses their heart so that the atoms contract as much as they can while remaining atoms.
The result is a body the size of the Earth made of so heavy materials that a teaspoon weighs a few tons. The star has become a white dwarf.
Big stars die more dramatically. They explode, producing shock waves that project materials in the space, as well as shock waves going inward. These can compress the nuclei so that the atoms collapse into neutrons.
The star is reduced to an object of a few kilometers, where a teaspoon can weigh about one billion tons. We have a neutron star.
If the star is really big, the shock waves in its death explosion can push the core material past the trigger point of the gravitational collapse. Drawn by its own gravity, the nucleus will then shrink without limit, in an infinitely small and infinitely dense: a singularity.
However, when this happens, the increasing intensity of its gravitational field will distort the space-time to form an envelope containing completely the singularity. Light and material will come in, but nothing can come out of it.
The horizon of events, containing most of the mass of the star, appears dead black. We have a black hole.
These black holes are too small to give an image unless we approach it dangerously. However, black holes can be formed in another way, in the nuclei of galaxies, and can be much larger.
Most galaxies, including ours, have black holes in the center. They are probably there since the galaxies were formed from collapses of gas and dust clouds in the young universe.
These can be very big, millions or more times the mass of the sun. They probably formed when the accumulations of gas and dust were so great that the pressure exerted on their hearts by the weight of the overlying materials pushed them above the trigger point of the gravitational collapse.
It would be easier to try to image one of these.
The one at the heart of our galaxy is an obvious target, but for the first black hole image, it pays to look for a big picture. It has long been suspected that the Messier 87 galaxy hosts a particularly large black hole.
This is why it was selected for the first attempt at image creation. Fascinating, the result gives rather what we expected: a dark object with a hot material that spiraled up, so even if there is still much science to do before understanding the black holes it seems we are going in the right direction.
- Mars is low and invisible in the west after dark.
- Jupiter, shining like a searchlight, gets up around 1am.
- Saturn rises 3 a, m.
- The moon will reach the last quarter on the 26th.
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