SPACE — NASA’s New Horizons mission, which discovered Pluto in 2015, is now traversing the depths of the Kuiper Belt. The cosmic dust storm it faced suggested there was more going on in the outer reaches of the solar system than astronomers imagined.
Space is filled with tiny dust particles that are only microns or one millionth of a meter in size. Most of the dust in our solar system is leftover from planet formation, a violent event that caused many objects to collide with each other.
Currently, this ancient dust is also accompanied by fresh dust scattered from the surfaces of asteroids and comets due to micrometeorite impacts. This dust content, both fresh and ancient, gives rise to the enigmatic ‘Zodiac light’.
The dust extends to the farthest regions of the solar system. Astronomers are still not completely sure of the final limit of the dust’s existence.
The Kuiper Belt or Kuiper–Edgeworth Belt, is named after the astronomers Gerard Kuiper and Kenneth Edgeworth who first hypothesized its existence. This belt is located very far away, and is on a very small and dim layer of ice. In 1992, the first Kuiper Belt Object (KBO) beyond Pluto was discovered.
The first KBO was discovered by University of Hawaii astronomers, Dave Jewitt and Jane Luu. But since then, thousands of other KBOs have been spotted, and astronomers have tentatively begun mapping the outer reaches of the solar system.
Outside the Kuiper Belt there is a Scattered Disk or disk distribution, which is inhabited by KBOs from the Kuiper Belt due to gravitational waves coming from the outermost planet of the solar system, Neptune. Objects in the Scattered Disk tend to have orbits that are highly elliptical and sharp relative to the plane of the solar system.
They can also be up to hundreds of AU from the sun. One AU or astronomical unit, is equal to the distance between the earth and the sun, which is 150 million kilometers.
Far beyond the Kuiper Belt and its scattered disk is the Oort Cloud, a vast spherical region of frozen objects that stretches more than a light year from the sun. Because of its distance, the Oort Cloud has never been observed directly until now.
However, scientists know about its existence because of the orbit of long-period comets. Now, new findings from New Horizons threaten to upend much of what was thought to be known about the outer solar system.
“New Horizons made the first direct measurements of interplanetary dust, far beyond Neptune and Pluto, so any observations could lead to (new) discoveries,” astronomer Alex Doner of the University of Colorado, Boulder said in a statement.
The distance between the outer edge of the Kuiper Belt and the sun is estimated to be about 50 AU. On January 1, 2019, New Horizons encountered a KBO named Arrokoth, located at a distance of 44.5 AU from the sun. Currently, New Horizons is at a distance of 58.25 AU from the Sun, after crossing the 50 AU barrier in April 2021.
Over the past five years, New Horizons should have sailed past the edge of the Kuiper Belt, if astronomers believe it is true. However, because the KBOs are millions of miles apart, New Horizons would not be visually aware that they had left them behind. Instead, the sign is a decrease in interplanetary dust levels.
However, the Venetia Burney Students Dust Counter (SDC) instrument, has not observed this decline. In fact, there is just as much dust out there, confusing astronomers.
The SDC is installed on the front of the New Horizons spacecraft. It consists of 14 plastic film detectors, each measuring 14.2 x 6.5 centimeters and only 28 microns thick.
A dozen detectors are exposed to space, while two others are protected inside New Horizons so they can act as reference detectors. They record any events unrelated to the dust impact to help rule out false positives.
Each time a dust particle hits one of the detectors, the impact leaves tiny holes in the plastic coating that subtly change the way the surface conducts electricity. One cause is excess dust produced near the Sun and blown out of the Kuiper Belt by the pressure of sunlight on some of these particles.
The Doner team considers the above theory impossible. “Instead, there are more interesting and favorable possibilities,” they said.
There may be more to the Kuiper Belt than astronomers realized so far. The continued presence of dust suggests New Horizons is still within the Kuiper Belt, and that the Kuiper Belt is much wider than anyone thought.
Allegedly, the belt stretches billions of miles farther from the sun than our current maps suggest. It’s not just the amount of dust that indicates that, astronomers have also used machine learning algorithms to search for more icy objects outside the solar system. They used the Subaru Telescope on Hawaii’s Mauna Kea and the Victor M Blanco Four-Meter Telescope in Chile.
So far, they’ve found 154 objects in the direction New Horizons is headed, including about 20 that New Horizons will hit within a few million miles. However, some of them appear to lie outside the Kuiper Belt, and not in eccentric orbits similar to the Scaterred Disk.
The question is, do they belong to the wider Kuiper Belt, or is there perhaps a second belt?
“The idea that we may have detected a vast Kuiper Belt, with a new population of objects colliding and producing more dust, provides another clue in solving the mystery of the solar system’s most distant regions,” Doner said.
New Horizons sails through the uncharted void of space. Only four spacecraft have traveled this path before, Pioneer 10 and 11, and Voyager 1 and Voyager 2. However, the other spacecraft were not equipped with dust counter instruments like New Horizons.
Even though Pioneer has been inactive for a long time and Voyager 1 is starting to fail to send data to Earth, New Horizons has enough fuel and power to last until the 2040s. When it finally does, it will be at a distance of more than 100 AU from the Sun.
By the time his power waned, he had most likely redrawn the entire map of the outer solar system. The new results from SDC were published in the Thursday, February 1, 2024 edition of the Astrophysical Journal Letters. Source: Space.com
2024-02-23 15:16:00
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