NASA’s new horizons mission encountered Pluto In 2015, we are now passing through the deepest depths of the earth Kuiper Beltis facing a cosmic dust storm, hinting that more may be happening in the farthest reaches of the universe solar system than we imagine.
Space is full of dust, which consists of tiny particles only microns (millionths of a meter) in size. Most of the dust in our solar system is leftover from the formation of planets, a violent event in which large numbers of objects crash into each other. Today, this old dust is joined by fresh dust bouncing off the surfaces. asteroids And comets With micrometeorite impacts. This dust content, both fresh and old, causes the mysterious “Zodiac light” to emerge. Dust extends to the farthest reaches of the solar system. Astronomers are still not entirely sure of the nature of this final frontier.
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The Kuiper Belt (or the Kuiper-Edgeworth Belt, named after astronomers Gerard Kuiper and Kenneth Edgeworth, who independently proposed its existence) is so distant and its icy inhabitants so small and faint that it was not until 1992 that the first Kuiper Belt Object (KBO) beyond Pluto was detected. ) was discovered. This discovery was made by University of Hawaii astronomers Dave Jewitt and Jane Luu. But since then, thousands of KBOs have been detected, and astronomers have been able to tentatively begin to map the outer solar system.
Beyond the Kuiper Belt is the Scattered Disc, populated by KBOs dispersed from the Kuiper Belt due to gravitational tides from the solar system’s outermost planet. Neptune. Objects in the Scattered Disc tend to have highly elliptical orbits that are inclined perpendicular to the plane of the solar system and can travel hundreds of AU from the sun. One AU, or astronomical unit, is equal to the distance between the Earth and the sun.
Far beyond the Kuiper Belt and the Scattered Disc Oort CloudA vast spherical region of frozen objects extending up to a light-year from the Sun. Although its remoteness means the Oort Cloud has never been directly observed, scientists know it exists because the orbits of long-period comets can be traced to it.
But now New Horizons’ new findings threaten to upend much of what we thought we knew about the outer solar system.
“New Horizons makes the first direct measurements of interplanetary dust far beyond Neptune and Pluto, so each observation could lead to a discovery,” said astronomer Alex Doner of the University of Colorado, Boulder. expression.
The distance between the outer edge of the Kuiper Belt and the sun was thought to be approximately 50 astronomical units (one AU also equals 149.5 million kilometers or 93 million miles). On January 1, 2019, New Horizons faced the KBO. named ArrokothLocated 44.5 AU from the Sun; Today New Horizons is located 58.25 AU from the Sun. Having passed the 50 AU limit in April 2021. For the last five years, New Horizons was supposed to pass through the edge of the Kuiper Belt. But since the KBOs are millions of kilometers apart, New Horizons would not visually notice that it had left them behind. Instead, the sign would be a drop in interplanetary dust levels.
But the Venetia Burney Student Dust Counter (SDC), named after the spacecraft The little girl who gave her name to Pluto This decline was not observed in 1930. In fact, there is more dust than ever before, which has baffled astronomers.
The SDC is mounted on the front of the New Horizons spacecraft. It consists of 14 plastic film detectors, each measuring 14.2 x 6.5 centimeters (5.6 x 2.6 inches) and only 28 microns thick. A dozen detectors are exposed to space, while the other two are shielded so they can serve as reference detectors and record any events unrelated to dust impacts to help eliminate false positives. Whenever a dust particle hits one of the detectors, the impact leaves a small dent in the plastic film, which slightly changes the way the surfaces conduct electricity.
One possibility is that the excess dust was actually produced closer to the Sun and was expelled from the Kuiper Belt by the pressure exerted by sunlight on the particles. However, Doner’s team thinks this theory is unlikely. Instead, they say, a more attractive possibility was preferred.
There may be more to the Kuiper Belt than astronomers think.
The continued presence of dust indicates that New Horizons is still within the Kuiper Belt, and that the Kuiper Belt is much larger than anyone knew, currently extending billions of miles further from the sun than our maps predict.
It’s not just the dust count that tells us this. Astronomers use machine learning algorithms Exploring observations made by the 8.2-meter Subaru Telescope on Mauna Kea in Hawaii and the Victor M. Blanco Four-Meter Telescope at the Cerro Tololo Inter-American Observatory in Chile, and hunting for more icy objects that New Horizons can investigate. So far they’ve found 154 objects in the direction New Horizons is heading; About 20 of these will come within a few million miles of the spacecraft, close enough for some basic observations. However, some of these 154 objects appear to be located beyond the Kuiper Belt, not in the eccentric orbit resembling the Scattered Disc, but in the ecliptic plane shared by the Kuiper Belt.
Are these members of a broader Kuiper Belt, or perhaps even a second generation?
“The idea that we may have detected an expanded Kuiper Belt, where a whole new population of objects are colliding and producing more dust, offers another clue in unraveling the mysteries of the solar system’s most distant regions,” Doner said.
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New Horizons is navigating uncharted waters. Only four spacecraft have passed this route before: Pioneer 10 and 11, and Traveler 1 And Traveler 2; none were equipped with a dust counter like New Horizons.
While the Pioneers have been inactive for a long time and are with the Voyager 1 spacecraft begins to falterNew Horizons has enough fuel and power to survive until the 2040s, when it can travel well beyond 100 AU from the Sun. When its power wanes, it will have completely redrawn the map of the outer solar system.
The new results of the SDC were published on February 1. Astrophysics Journal Letters.