There are billions of stars and planets in the universe. And while a star is a flaming sphere of gas, planets like Earth are made up of solid elements. Planets form in clouds of dust that swirl around a newly formed star. In turn, the grains of this dust are composed of elements such as carbon, silicon, oxygen, iron and magnesium. But where do cosmic dust particles come from? A new study from the Niels Bohr Institute in Copenhagen shows that dust grains can not only form in giant supernova explosions, they can also survive the subsequent shock waves of various explosions that impact the dust.
A computer image of how cosmic dust is formed during supernova explosions. Source: ESO/M. Kornmesser
How cosmic dust was formed has long been a mystery to astronomers. The dust elements themselves form in flaming hydrogen gas in stars. Hydrogen atoms combine with each other to form increasingly heavier elements. As a result, the star begins to emit radiation in the form of light. When all the hydrogen is exhausted and it is no longer possible to extract energy, the star dies, and its shell flies off into outer space, which forms various nebulae in which young stars can again be born. Heavy elements are formed primarily in supernovae, the progenitors of which are massive stars that die in a giant explosion. But how single elements clump together to form cosmic dust remained a mystery.
“The problem was that even if dust were formed along with elements in supernova explosions, the event itself is so violent that these small grains simply should not survive. But cosmic dust exists, and its particles can be of completely different sizes. Our research sheds light on this problem,” Professor Jens Hjorth, head of the Center for Dark Cosmology at the Niels Bohr Institute.
A Hubble telescope image of the unusual dwarf galaxy that produced the bright supernova SN 2010jl. The image was taken before its appearance, so the arrow shows its progenitor star. The star that exploded was very massive, approximately 40 solar masses. Source: ESO
In cosmic dust studies, scientists are observing supernovae using the X-shooter astronomical instrument at the Very Large Telescope (VLT) facility in Chile. It has amazing sensitivity, and the three spectrographs included in it. can observe the entire range of light at once, from ultraviolet and visible to infrared. Hjorth explains that they initially expected a “proper” supernova explosion to occur. And so, when this happened, a campaign to monitor it began. The observed star was unusually bright, 10 times brighter than the average supernova, and its mass was 40 times that of the Sun. In total, observing the star took the researchers two and a half years.
“Dust absorbs light, and using our data we were able to calculate a function that could tell us about the amount of dust, its composition and grain size. We found something truly exciting in the results,” Krista Gaul.
The first step toward the formation of cosmic dust is a mini-explosion in which a star ejects material containing hydrogen, helium and carbon into space. This gas cloud becomes a kind of shell around the star. A few more such flashes and the shell becomes denser. Finally, the star explodes and a dense cloud of gas completely envelops its core.
“When a star explodes, the shock wave hits the dense gas cloud like a brick hitting a concrete wall. All this happens in the gas phase at incredible temperatures. But the place where the explosion hit becomes dense and cools to 2000 degrees Celsius. At this temperature and density, the elements can nucleate and form solid particles. We found dust grains as small as one micron, which is very large for these elements. With such dimensions, they will be able to survive their future journey through the galaxy.”
Thus, scientists believe that they have found the answer to the question of how cosmic dust is formed and lives.
Interstellar dust is a product of processes of varying intensity occurring in all corners of the Universe, and its invisible particles even reach the surface of the Earth, flying in the atmosphere around us.
It has been proven many times that nature does not like emptiness. Interstellar space, which appears to us as a vacuum, is actually filled with gas and microscopic, 0.01-0.2 microns in size, dust particles. The combination of these invisible elements gives rise to objects of enormous size, a kind of clouds of the Universe, capable of absorbing certain types of spectral radiation from stars, sometimes completely hiding them from earthly researchers.
What is interstellar dust made of?
These microscopic particles have a core that is formed in the gas envelope of stars and is completely dependent on its composition. For example, graphite dust is formed from grains of carbon stars, and silicate dust is formed from oxygen particles. This is an interesting process that lasts for decades: as stars cool, they lose their molecules, which, flying into space, join into groups and become the basis of the core of a dust grain. Next, a shell of hydrogen atoms and more complex molecules is formed. At low temperatures, interstellar dust occurs in the form of ice crystals. Wandering around the Galaxy, little travelers lose some of the gas when heated, but new molecules take the place of the departed molecules.
Location and properties
The bulk of the dust that falls on our Galaxy is concentrated in the Milky Way region. It stands out against the background of stars in the form of black stripes and spots. Despite the fact that the weight of dust is negligible compared to the weight of gas and is only 1%, it is capable of hiding celestial bodies from us. Although the particles are separated from each other by tens of meters, even in this quantity the densest regions absorb up to 95% of the light emitted by the stars. The size of the gas and dust clouds in our system is truly enormous, measured in hundreds of light years.
Impact on observations
Thackeray's globules make the area of the sky behind them invisible
Interstellar dust absorbs most of the radiation from stars, especially in the blue spectrum, and it distorts their light and polarity. The greatest distortion is experienced by short waves from distant sources. Microparticles mixed with gas are visible as dark spots in the Milky Way.
Due to this factor, the core of our Galaxy is completely hidden and accessible to observation only in infrared rays. Clouds with a high concentration of dust become almost opaque, so the particles inside do not lose their icy shell. Modern researchers and scientists believe that it is they, when sticking together, that form the nuclei of new comets.
Science has proven the influence of dust granules on the processes of star formation. These particles contain various substances, including metals, which act as catalysts for numerous chemical processes.
Our planet increases its mass every year due to falling interstellar dust. Of course, these microscopic particles are invisible, and to find and study them, they study the ocean floor and meteorites. The collection and delivery of interstellar dust has become one of the functions of spacecraft and missions.
When large particles enter the Earth's atmosphere, they lose their shell, and small particles circle around us invisibly for years. Cosmic dust is ubiquitous and similar in all galaxies; astronomers regularly observe dark features on the faces of distant worlds.
Where does cosmic dust come from? Our planet is surrounded by a dense air shell - the atmosphere. The composition of the atmosphere, in addition to the gases known to everyone, also includes solid particles - dust.
It mainly consists of soil particles that rise upward under the influence of the wind. During volcanic eruptions, powerful dust clouds are often observed. Entire “dust caps” hang over large cities, reaching a height of 2-3 km. The number of dust particles in one cubic meter. cm of air in cities reaches 100 thousand pieces, while in clean mountain air there are only a few hundred of them. However, dust of terrestrial origin rises to relatively low altitudes - up to 10 km. Volcanic dust can reach a height of 40-50 km.
Origin of cosmic dust
The presence of dust clouds has been established at altitudes significantly exceeding 100 km. These are the so-called “noctilucent clouds”, consisting of cosmic dust.
The origin of cosmic dust is extremely diverse: it includes the remains of disintegrated comets and particles of matter ejected by the Sun and brought to us by the force of light pressure.
Naturally, under the influence of gravity, a significant part of these cosmic dust particles slowly settles to the ground. The presence of such cosmic dust was discovered on high snowy peaks.
Meteorites
In addition to this slowly settling cosmic dust, hundreds of millions of meteors burst into our atmosphere every day - what we call “falling stars”. Flying at cosmic speeds of hundreds of kilometers per second, they burn out from friction with air particles before they reach the surface of the earth. The products of their combustion also settle on the ground.
However, among the meteors there are also exceptionally large specimens that reach the surface of the earth. Thus, the fall of the large Tunguska meteorite at 5 o’clock in the morning on June 30, 1908 is known, accompanied by a number of seismic phenomena noted even in Washington (9 thousand km from the place of fall) and indicating the power of the explosion when the meteorite fell. Professor Kulik, who with exceptional courage examined the site of the meteorite fall, found a thicket of windfall surrounding the site of the fall within a radius of hundreds of kilometers. Unfortunately, he was unable to find the meteorite. An employee of the British Museum, Kirkpatrick, made a special trip to the USSR in 1932, but did not even get to the site of the meteorite fall. However, he confirmed the assumption of Professor Kulik, who estimated the mass of the fallen meteorite at 100-120 tons.
Cloud of cosmic dust
An interesting hypothesis is that of Academician V.I. Vernadsky, who considered it possible that it was not a meteorite that would fall, but a huge cloud of cosmic dust moving at colossal speed.
Academician Vernadsky confirmed his hypothesis with the appearance these days of a large number of luminous clouds moving at high altitudes at a speed of 300-350 km per hour. This hypothesis could also explain the fact that the trees surrounding the meteorite crater remained standing, while those located further were knocked down by the blast wave.
In addition to the Tunguska meteorite, a number of craters of meteorite origin are known. The first of these craters to be surveyed can be called the Arizona crater in Devil's Canyon. It is interesting that not only fragments of an iron meteorite were found near it, but also small diamonds formed from carbon from high temperature and pressure during the fall and explosion of the meteorite.
In addition to the indicated craters, indicating the fall of huge meteorites weighing tens of tons, there are also smaller craters: in Australia, on the island of Ezel and a number of others.
In addition to large meteorites, quite a lot of smaller ones fall out every year - weighing from 10-12 grams to 2-3 kilograms.
If the Earth were not protected by a thick atmosphere, we would be bombarded every second by tiny cosmic particles traveling at speeds faster than bullets.
The science
Scientists have noticed a large cloud of cosmic dust created by a supernova explosion.
Cosmic dust may provide answers to questions about how life appeared on Earth- whether it originated here or was brought with comets that fell to Earth, whether water was here from the very beginning or was it also brought from space.
A recent image of a cloud of cosmic dust that occurred after a supernova explosion proves thatsupernovaecapable of producing enough cosmic dust to create planets like our Earth.
Moreover, scientists believe that this dust is enough to create thousands suchplanets like earth.
Telescope data shows warm dust (white) that survived inside the supernova remnant. The supernova remnant cloud Sagittarius A Vostok is shown in blue. Radio emission (red) indicates the collision of the expanding shock wave with surrounding interstellar clouds (green).
It is worth noting that cosmic dust participated in the creation of both our planet and many other cosmic bodies. Sheconsists of small particles up to 1 micrometer in size.
It is now known that comets contain primordial dust that is billions of years old and played a major role in the formation of the Solar System. By examining this dust you can learn a lot abouthow the Universe and our solar system began to be createdin particular, and also learn more about the composition of the first organic matter and water.
According to Ryan Lau of Cornell University in Ithaca, New York,flash,recentlycaptured by telescope, occurred 10,000 years ago, and the result was a cloud of dust large enough tothere are 7,000 planets similar to Earth.
Observations of a supernova (Supernova)
By using Stratospheric Observatory for Infrared Astronomy (SOFIA), scientists studied the intensity of the radiation and were able to calculate the total mass of cosmic dust in the cloud.
It is worth noting that SOFIA is a joint a project of NASA and the German Aviation and Space Center. The goal of the project is to create and use a Cassegrain telescope on board a Boeing 474 aircraft.
During the flight at an altitude of 12-14 kilometers, a telescope with a circumference of 2.5 meters is capable of creating photographs of space that are close in quality to the photographs taken by space observatories.
Led by Lau, the team used the SOFIA telescope with a special cameraFORCAST on board,to take infrared images of a cloud of cosmic dust, also known as the Sagittarius A Vostok supernova remnant. FORCAST isinfrared camera for detecting low-contrast objects.
