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What scientists found as they sift dust in space

Just as dust collects in the corners and on the bookshelves, dust also builds up in space. However, when the dust settles in the solar system, it is often in rings. Several dust rings orbiting the sun. The rings trace the orbits of planets whose gravity drags dust around the sun on their way to the center of the solar system.

The dust consists of compressed remnants of the formation of the sun system about 4.6 billion years ago – debris from asteroid collisions or crumbs of blazing comets. Dust is distributed throughout the solar system, but it collects on granular rings over the orbits of the Earth and Venus, rings that can be seen with telescopes on Earth. By studying this dust ̵

1; what it consists of, where it comes from and how it moves through space – scientists are looking for clues to understanding the birth of planets and the composition of what we see in the solar system.

Two recent studies report new discoveries of dust rings in the inner solar system. One study uses NASA data to establish evidence of Mercury dust around the Sun in orbit. NASA's second study identifies the probable source of the dust ring in the orbit of Venus: a group of asteroids that have never been discovered before and that congregate with the planet.

"It's not every day something new to discover the inner solar system," said Marc Kuchner, author of the Venus study and astrophysicist at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "That's right in our neighborhood."

In this illustration, several dust rings circle the sun. These rings form when the heaviness of the planets pull dust grains into orbit around the sun. Scientists recently discovered Mercury's dust orbit in orbit. Others suggest that the source of the dust ring of Venus is a group of asteroids that had never been discovered before.

[ Goddard Space Flight Center of NASA / Mary Pat Hrybyk-Keith]

Another ring around the sun

Guillermo Stenborg and Russell Howard, both solos at the Naval Research Laboratory in Washington, DC, did not want to find a dust ring. "We found it by accident," Stenborg said, laughing. The researchers summarized their findings in an article published in the Astrophysical Journal on November 21, 2018.

They describe the evidence of a fine veil of cosmic dust over Mercury's orbit, which forms a ring about 9.3 million kilometers wide. Mercury – 3,030 miles wide, just big enough for the continental United States to stretch across this huge dust path as it circles the sun.

Ironically, the two scientists were looking for dust on the dust ring region near the sun. At some distance from the sun, after a decade-long prediction, the powerful heat of the star should allow dust to evaporate, purifying the entire room. If you know where this limit lies, you can tell scientists about the composition of the dust itself and suggest how planets formed in the young solar system.

So far, no evidence for dust-free space has been found, but that is partly because it would be hard to spot from Earth. No matter what scientists look like from Earth, all the dust between us and the sun is in the way, making them imagine that space near the sun is dustier than it actually is.

Stenborg and Howard thought they could work around this problem by building a model based on images of interplanetary space from NASA's STEREO satellite – short for Solar and Terrestrial Relations Observatory.

According to scientists, planets begin with mere dust grains. They emerge from huge gas and dust disks, which orbit young stars. Gravity and other forces collide and fuse the material within the disc.

( NASA's Jet Propulsion Laboratory)

Ultimately, the two wanted to test their new model in preparation for the current NASA Parker solar probe, flying a highly elliptical orbit around the Sun and swinging over the next seven years getting closer to the star. They wanted to apply their technique to the images that Parker will send to Earth and see how dust near the sun behaves.

Scientists have never worked with data collected in this unexplored area near the Sun. Models such as those by Stenborg and Howard provide a crucial context for understanding the observations of Parker Solar Probe, as well as clues as to which space environment the spacecraft is in – sooty or sparkly clean.

There are two types of light in STEREO images: light from the radiant external atmosphere of the sun – the so-called corona – and light reflected from dust in space. The sunlight reflected from this dust slowly orbiting the sun is about 100 times brighter than coronal light.

"We're not really dusty people," said Howard, who is also the lead scientist for the STEREO cameras and is Parker Solar Probe, who photographed the Corona. "The dust near the sun is just showing in our observations, and generally we threw it away." Solar scientists like Howard, who study solar activity to predict, for example, the upcoming space weather, including giant explosions of solar material that sometimes sends the sun in our direction, have for years developed techniques to eliminate the effects of this dust. Only after the light soiling has been removed from dust, you can clearly see what the corona is doing.

The two scientists built their model as a tool for others to eliminate the annoying dust in STEREO – and finally Parker Solar Probe – images. The prediction of dust-free space remained in the back of their minds. If they could find a way to separate the two types of light and isolate the dust, they could figure out how much dust was really there. For example, finding that all the light in an image is from the corona may indicate that they finally found dust-free space.

Mercury's dust ring was a lucky find, a discovery that Stenborg and Howard had made during their stay worked on their model. As they used their new technique for the STEREO imagery, they noticed a pattern of increased brightness along Mercury's orbit – more dust – in the light they'd otherwise thrown away.

"It was not an isolated thing," Howard said. "Everywhere around the sun, regardless of the position of the spacecraft, we were able to increase the increase in dust brightness or density by five percent, the said something was there and something that extends around the sun."

Scientists have never considered that there could be a ring along Mercury's orbit, so it has remained undetected until now, Stenborg said. "People thought that Mercury, unlike Earth or Venus, is too small and too close to the sun to trap a dust ring," he said. "They expected the solar wind and magnetic forces of the sun to blow excess dust into Mercury's orbit."

With an unexpected discovery and a sensitive new tool under their belt, researchers are still interested in the dust-free zone. While the Parker Solar Probe continues exploring the corona, its model can help others discover other dust bunnies that are near the sun.

Asteroids hide in orbit of Venus

It's not the first time scientists have found a dust ring in the inner solar system. Twenty-five years ago, scientists discovered that the Earth is orbiting the Sun in a giant dust ring. Others discovered a similar ring near the Venus orbit. First, archive data of the German-American Helios spacecraft were used in 2007 and then confirmed in 2013 with STEREO data.

Since then scientists have determined the dust ring in Earth orbit. It originates mainly from the asteroid belt, the wide, donut-shaped region between Mars and Jupiter, where most of the solar system's asteroids live. These rocky asteroids are constantly bumping against each other, hurling dust that drifts deeper into the gravitational pull of the sun, unless the earth's gravity pulls the dust into the orbit of our planet.

At first it seemed as if the dust ring of Venus had formed like Earth's. of dust that arises elsewhere in the solar system. When Goddard's astrophysicist Petr Pokorny whirled dust from the asteroid belt toward the sun, his simulations generated a ring that matched the observations of the Earth Ring – but not Venus.

This discrepancy made him wonder where else does the asteroid belt get the dust in orbit of Venus? After a series of simulations, Pokorny and his research partner Marc Kuchner suspected that it was a group of asteroids that had never been discovered before and that orbited the sun next to Venus. They published their work in The Astrophysical Journal Letters on March 12, 2019.

"The most exciting thing about this result is that it suggests a new population of asteroids that are likely to provide clues as to how the solar system formed." said Kuchner. If Pokorny and Kuchner are able to watch them, this asteroid family could shed light on the early stories of Earth and Venus. With the right tools, the asteroids could also provide clues to the chemical diversity of the solar system.

The Venus Dust Ring, which is spread over a larger orbit, is much larger than the newly discovered ring at Mercury. About 16 million miles from top to bottom and 6 million miles wide, the ring is dotted with dust, the largest grains of which are about the size of those in coarse sandpaper. It is about 10 percent thicker with dust than the surrounding space. Still, it's diffuse – pack all the dust in the ring and all you would get is an asteroid two kilometers across.

With a dozen different modeling tools to simulate how dust moves in the solar system, Pokorny modeled all dust sources he could think of, looking for a simulated Venus ring that matched the observations. The list of all the sources he has tried sounds like an appeal from all the rocky objects in the solar system: main belt asteroids, Oort cloud comets, Halley-type comets, comets of the Jupiter family, recent collisions in the asteroid belt. [19659002 "But none of them worked," said Kuchner. "So we started building our own dust sources."

Perhaps, the two scientists said, the dust came from asteroids much closer to Venus than the asteroid belt. There might be a group of asteroids orbiting the sun with Venus – that is, they share the orbit of Venus, but they remain far away from the planet, often on the other side of the sun. Pokorny and Kuchner argued that a group of asteroids in Venus' orbit could have gone undetected until now, as it is difficult to direct Earthbound telescopes in that direction so close to the Sun without disturbing the Sun's light.

Asteroids represent building blocks of the rocky planets of the solar system. When they collide in the asteroid belt, they shed dust that is scattered throughout the solar system, and can inspect scientists for clues to the early history of planets.

[ The NASA (Conceptual Image Lab) Goddard Space Flight Center

Asteroids with orbit are an example of what is referred to as resonance, an orbit pattern that connects different orbits, each after how their gravitational influences meet. Pokorny and Kuchner modeled many potential resonances: asteroids orbiting the Sun twice for every three of Venus' orbits, nine times for Venus, ten and one for Venus. Of all the possibilities, one group alone produced a realistic simulation of the Venus dust ring: a pack of asteroids that occupy the orbit of Venus, bringing together the Venus journeys around the Sun for one person.

But scientists could not just call It was a day after finding a hypothetical solution that worked. "We thought we had discovered this asteroid population but had to prove it and show that it works," Pokorny said. "We were excited, but then you realize," Oh, there is so much to do. "

They had to show that the existence of the asteroids in the solar system makes sense, and it was unlikely, she found, that asteroids in those special circular orbits near Venus were arriving there from other places like the asteroid belt, their hypothesis It would make more sense if the asteroids had been there since the beginning of the solar system.

The scientists built a different model, this time with a total of 10,000 asteroids near Venus, letting the simulation go through 4.5 billion years of history Flowing through the solar system, taking into account all the gravitational effects of all planets, around 800 of their test asteroids survived the test of time as the model reached today.

Pokorny sees this as an optimistic survival rate, indicating that asteroids could have formed near the Venus orbit in the chaos of the early solar system, and egg niger could stay there today and feed the nearby dust ring.

The next step is to observe and observe the elusive asteroids. "If there is anything, we should be able to find it," Pokorny said. Their existence could be demonstrated using spaceborne telescopes such as Hubble or perhaps interplanetary space imagers such as STEREOs. Then the scientists will answer further questions: How many are there and how big are they? Do you constantly spill dust, or was there only a departure event?

Dust rings around other stars

In this illustration, an asteroid breaks apart under the strong gravitational force of LSPM J0207 + 3331, a white dwarf star that is about 145 light-years away. Scientists believe that crumbling asteroids provide the dust rings around this ancient star. NASA / Scott Wiessinger's Goddard Space Flight Center

The dust rings that Mercury and Venus Shepherd are only one or two planets away are scientists have discovered many other dust rings in distant star systems. Large dust rings are easier to detect than exoplanets and could be used to deduce the otherwise hidden planets and even their orbits.

However, the interpretation of extrasolar dust rings is not easy. "To be able to model and accurately read the dust rings around other stars, we first need to understand the physics of the dust in our own backyard," Kuchner said. By studying neighboring dust rings on Mercury, Venus, and Earth, where dust traces the lasting effects of gravity in the solar system, scientists can develop reading techniques between the near and far dust rings.

This article originally appeared on NASA. Follow @NASA on Twitter.

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