The history of dust through space and time

What is dust

It is ridiculous to ask only this question in India. Dust is everywhere. On the streets, in your nose, in your lungs. They lock up your house, go on holiday for a month and come back, and there is a nice patina on the table. It's in your laptop and controls the fan nuts.

It's also in the atmosphere, in orbit around the earth, even in space. It makes nightmarish storms on Mars. Philip Pullman and Steven Erikson have written books about it. Dust is omnipresent. (The only dust-free spots I've seen are stock photos scattered across the internet.)

But what exactly is it and where does it all come from?

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earth

The Sahara dust cloud in June 2018. Photo credit: NASA / Earth Observatory

The Sahara dust cloud in June 2018. Photo credit: NASA / Earth Observatory

Dust is fine dust. It comes from a variety of sources. The atmospheric – or aeolian – dust that we know so well consists of small particles sheared off from solid objects. For example, fast-moving winds blow particles from loose, dry soil into the air and generate so-called volatile dust. Another source is the smoke from exhaust pipes.

Another are mites of the family Pyroglyphidae. They eat skin flakes, even those that are shed by humans, and digest them with enzymes that remain in their feces. In your home, exposure to their faeces (considered a form of dust) can trigger asthma attacks.

Winds remove particulate matter from the earth's surface and transport it into the troposphere. Once dust has appeared, it acts like an aerosol that traps the heat underneath and heats the earth's surface. Once it accumulates in sufficient quantity, it influences the weather of underlying regions, including the precipitation patterns.

Dust particles smaller than 10 microns will enter your lungs and affect your respiratory health. They conspire with other pollutants and stagnate during the winter in India's National Capital Region. Particles smaller than 2.5 microns will "increase the age-specific mortality risk" (source) and send hospital admissions higher.

There is also dust that covers thousands of miles to affect distant parts of the world. According to one study, "Sahara is the world's largest source of desert dust." In June of this year, the tropical area of ​​the Atlantic Ocean experienced its dustiest time in 15 years, when a tremendous wind from north-eastern Chad crashed into Central America. According to NASA's Earth Observation Center, Sahara dust "helps build beaches in the Caribbean and fertilize the Amazon."

But speaking of dust traveling over long distances, the transatlantic nebula seems to be less a journey than the dust meteorites have driven hundreds of thousands of miles through space. As these stones move towards the ground, the atmosphere burns dusty matter off their surfaces and lets them hang in the upper atmosphere.

Atoms released from these particles into the mesosphere drift into the planet's circulation system and move from pole to pole for months. They interact with other particles to leave a trail of charged particles. Scientists then use radar to track these particles to learn more about the circulation itself. Some dust particles of extraterrestrial origin also reach the Earth's surface over time. They could bring about physical and chemical reactions that they may have experienced in space billions of years ago.

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orbit

Dust in the Andromeda Galaxy, seen from the Spitzer Space Telescope. Credit: NASA / JPL-Caltech / K. Gordon (University of Arizona)

Dust in the Andromeda Galaxy, seen from the Spitzer Space Telescope. Credit: NASA / JPL-Caltech / K. Gordon (University of Arizona)

In the mid-twentieth century, researchers used optical data and mathematical arguments to determine that about four million tons of meteorite were thrown into the atmosphere of our planet each year. This was cause for concern: the number indicated that the number of meteorites in space was much higher than previously thought. Again, the threat to our satellites could have been underestimated. More careful judgments brought the number down later. A review from 2013 states that 10 to 40 tonnes of meteorites reach the Earth's atmosphere every day.

Yet, this number is not low – and its effects are exacerbated by the debris that puts humans themselves in orbit around the Earth. The Wikipedia article on "space debris" notes carefully: "By July 2016, the United States Strategic Command had tracked a total of 17,852 artificial objects in orbit above Earth, including 1,419 operational satellites." But only one line later, the number of objects smaller than 1 cm explodes 170 million.

If a 0.00001 kg dust grain, which is carried by a breeze of 1.4 m / s, hits your face, you will feel nothing. This is because its momentum – the product of mass and velocity – is very low. However, when a one-hundredth gram heavy particle strikes a satellite at a relative speed of 1.5 km / s, its momentum jumps a thousandfold. Suddenly it can damage critical components and sensitively constructed surfaces, resulting in multi-year multi-year missions worth millions. One study suggests that if they are fast enough, such particles can also generate small shockwaves.

Before we stop on the Dust Voyage, we take a little break in the sci-fi. The overestimation of meteoric dust flow in the middle of the century may have led Arthur C. Clarke to write his 1961 novel: A case of moon dust, In history, a cruise ship called the Selene takes tourists over a basin of the finest dust, which is apparently of meteoric origin. But one day a natural disaster will cause that Selene sink into the dust and pin its passengers in life-threatening conditions. After much desperation, a rescue mission takes place when an astronomer from space discovers a heat trail pointing to the site of Selene from a spacecraft Lagrange II,

This name refers to the famous Lagrange points. As the earth orbits the sun and the moon circles the earth, their combined gravitational fields yield five points in space where the force acting on an object is just right to maintain its position relative to the earth and the sun. These are called L1, L2, L3, L4 and L5.

A contour plot of the effective potential of the Earth-Sun system with the five Lagrange points. Credit: NASA and Xander89, CC BY 3.0

A contour plot of the effective potential of the Earth-Sun system with the five Lagrange points. Credit: NASA and Xander89, CC BY 3.0

The Indian Space Research Organization (ISRO) plans to launch its Aditya satellite to study the Sun on L1. This is useful because at L1 the view from Aditya to the sun is not blocked by the earth. However, objects at L1, L2 and L3 have an unstable balance. Without occasionally stationary measures, they often fall out of their positions.

However, this is not the case for L4 and L5, where objects remain in a more stable equilibrium. And like everything that has been lying around for a while, they collect dust.

In the fifties, the Polish astronomer Kazimierz Kordylewski claimed to have discovered two dust clouds at L4 and L5. These mist-like accumulations of fine dust have since been referred to as Kordylewski clouds. Other astronomers, however, have denied their existence. For example, the Hitenite satellite did not find significant levels of dust in the L4 and L5 regions in 2009. Some argued that Hiten might have missed them because the dust clouds are too far apart.

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space

The impression of an artist of dust formation during a supernova explosion. Caption and credit: ESO / M. Kornmesser, CC BY 4.0

An artistic impression of dust formation during a supernova explosion. Caption and credit: ESO / M. Kornmesser, CC BY 4.0

Just two weeks ago, Hungarian astronomers claimed to have confirmed dust clouds in these regions (their papers here and here). As the L4 and L5 regions are of interest for future space missions, astronomers must now validate this finding and, if they do, assess the dust density and associated threat probabilities.

Unlike Kordylewski, who photographed from a mountain top, the Hungarian group relied on the ability of dust to polarize light. Light is electromagnetic radiation. Each light wave consists of an electric and a magnetic field, which oscillate perpendicular to each other. Imagine different waves of light approaching dust, and their electric fields point in any direction. However, after hitting the dust, the particles polarize the waves, causing all electric fields to align in a particular orientation.

When astronomers discover such light, they know that it has struck dust on its way. Using various instruments and analysis techniques, they can then image the dust distribution in the space through which the light has passed.

For example, the Planck telescope of the European Space Agency was able to detect dust in the vicinity of the Milky Way.

A dust map in and around the Milky Way, as observed by the ESA Planck telescope. Credit: NASA

A dust map in and around the Milky Way, as observed by the ESA Planck telescope. Credit: NASA

That's billions of billions of tons. Do not you compare your complaints about dust around the house?

And even on this scale, it was a nuisance. We do not know if the galaxy complains, but Brian Keating certainly did.

In March 2014, Keating and his team from the Center for Astronomy at Harvard University announced that they had found evidence that the volume of the universe had risen by a factor of ten80 in only 10-33 Seconds a moment after his birth in the Big Bang. About 380,000 years later, the radiation left over from the Big Bang – the so-called cosmic microwave background (CMB) – was created. Keating and co. used the BICEP2 detector at the South Pole to find cosmic inflation imprints on the CMB. The Smoking Cannon: Light of a specific wavelength polarized by gravitational waves from the early Universe.

While the announcement was made with great enthusiasm – as a "discovery of the decade" and what not, their claim quickly became suspect. Data from the Planck telescope and other observatories soon showed that the team found by Keating was actually light polarized by galactic dust. Her ambition to win a Nobel Prize collapsed. Ashes to Ashes dust to dust.

You probably ask: Did not do enough? Can we stop now? "No. We must persevere because dust has done more and we have come so close. Take a look at the dust map of the Milky Way, for example. Where could all this dust come from?

Here the history of the dust takes a more favorable turn. We all heard that it is stardust. It would be futile to try to track where the dust comes from, but to understand dust itself, we have to look at the stars.

The storms on Earth or on Mars, which stir dust in the air, are weak breaths against the colossal turbulence of the destruction of the stars. Stars can die in many different ways, depending on their size. The supernovae are the most spectacular. In a standard supernova type 1a, a whole white dwarf star undergoes a nuclear fusion that completely dissolves and expels at over 5,000 km / s. More massive stars suffer a nuclear collapse, which pushes their outermost layers into a sinking death into space, before what is left implodes into a neutron star or a black hole.

However, the material released into space forms huge clouds that slowly spread over millions of years. When they are near a black hole, they are trapped in an accretion disk, accelerated, heated and excited by radiation and magnetic fields. The happier motives can fly away to hit other stars, planets, or other objects, or even collide with other dust and gas clouds. Such interactions are very difficult to model-but there is no doubt that these interactions are all essentially determined by the four fundamental forces of nature.

One of them is gravity. If a cloud of gas / dust becomes so great that its collective appeal does not dissipate it, it could collapse into another star and experience a different era.

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Together

The cat's pocket fog, pictured here by NASA's Spitzer Space Telescope, is located in the Milky Way and is located in the constellation Scorpius. The distance from Earth is estimated at 4,200 and 5,500 light-years. The green areas indicate areas where the radiation of hot stars collided with large molecules and small dust grains called polycyclic aromatic hydrocarbons, causing them to fluoresce. Caption and credit: NASA / JPL-Caltech, Wikimedia Commons

The Cat Paw Nebula pictured here by the NASA Spitzer Space Telescope is between 4,200 light years and 5,500 light years from Earth. The green areas indicate areas where the radiation of hot stars collided with large molecules and small dust grains called polycyclic aromatic hydrocarbons, causing them to fluoresce. Caption and credit: NASA / JPL-Caltech, Wikimedia Commons

In this way, stars are cosmic engines. They keep matter – including dust – in motion. They may not be the only ones doing this, but given the presence of stars in the (observable) universe, they certainly play a big role. When they are not brought to life or come out of it, their attraction affects the trajectories of other, smaller bodies around them, including comets, asteroids, and other space rocks.

The solar system itself is considered compacted out of a large dust and dust disk formed of various elements around a young sun – a disc of remnants since the birth of the star. Different planets have been formed based on the availability of different volumes of different materials at different times. It is believed that Jupiter is in the first place and the inner planets, including the earth, are the last.

But no problem; Life here had everything it took to take root. Scientists still know what these ingredients could be and what their origins might be. One theory is that they contained compounds of carbon and hydrogen, called polycyclic aromatic hydrocarbons, and that they first formed, as you suspected, under the dust that winds through space.

They could then have been brought to Earth by meteors and comets, perhaps swung by the gravitational force of the Sun towards Earth's orbit. For example, when a comet approaches a star, the material begins to evaporate on its surface, forming a streak of gas and dust. When the earth passes through a region where the remains of the tail and other small, stony debris have remained, they enter the atmosphere as a meteor shower.

Dust is really everywhere, and he rarely gets the credit he deserves. It was and is an annoying part of everyday life. However, unlike our quest for extra-terrestrial comradeship, we are not alone in feeling burdened with dust.

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