by NASA on New Vision mission, which is Pluto in 2015 is now riding through the deepest depth of the Kuiper beltencountering a cosmic dust storm that suggests there may be more going on in the outermost reaches of the Solar system than we imagine.
Space is filled with dust made up of tiny particles only microns — millionths of a meter — in size. Much of the dust in our solar system was left over from the formation of the planets, which must have been there when many objects collided. Today, fresh dust is sputtered out from surfaces in addition to this ancient dust asteroids and Comets through micrometrite impacts. This dust material, both fresh and ancient, gives the enigmatic “Zodiacal Light”. The dust extends into the farthest reaches of the solar system. Astronomers are still not entirely sure of the composition of this final boundary.
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The Kuiper Belt (or Kuiper-Edgeworth Belt, named after the astronomers Gerard Kuiper and Kenneth Edgeworth, who independently proposed its existence) is so far away, and its icy inhabitants so small and faint, that it was not it was not until 1992 that the first Kuiper Belt Object (KBO) was discovered over Pluto. That discovery was made by University of Hawaii astronomers Dave Jewitt and Jane Luu. But since then, thousands of KBOs have been observed, and astronomers have tentatively begun to map the outer solar system.
Beyond the Kuiper Belt is the Scattered Disk, in which KBOs are scattered from the Kuiper Belt by gravitational tides coming from the outermost planets of the solar system, Neptune. Objects in the Scattered Disk tend to have highly elliptical orbits that are sharply inclined to the plane of the solar system and can go out to 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 Disk is the Oort cloud, a vast spherical region of frozen matter that stretches over a light-year from the sun. Although its distance means the Oort Cloud has never been directly observed, scientists know it exists because the orbits of long-period comets can be traced back to it.
Now, however, new results from New Horizons risk throwing much of what we knew about the solar system out to begin with.
“New Horizons is making the first direct measurements of interplanetary dust well beyond Neptune and Pluto, so each observation could lead to a discovery,” said astronomer Alex Doner of the University of Colorado, Boulder in a. statement.
The distance between the outer edge of the Kuiper Belt and the sun was thought to be about 50 astronomical units (one AU is equal to 149.5 million kilometers, or 93 million miles.) On January 1, 2019, New Horizons encountered the designated KBO Arrokoth, which sits at a distance of 44.5 AU from the sun; today, New Horizons is 58.25 AU from the Sun, after reaching the 50 AU mark in April 2021. In the last five years, New Horizons should have passed the edge of the Kuiper Belt. With KBOs separated by millions of miles, however, New Horizons would not visually detect that it had left them behind. Instead the signal would be a decrease in interplanetary dust levels.
However, the Venetia Burney Student Dust Counter (SDC) has the spacecraft named after her the little girl named Pluto in 1930, he did not notice this fall. In fact, there is as much dust as ever out there, bewildering astronomers.
The SDC is located on the front face of the New Horizons spacecraft. It consists of 14 plastic film detectors, each 14.2 by 6.5 centimeters (5.6 by 2.6 inches) in size and just 28 microns thick. A dozen of the detectors are exposed to space, and the other two are shielded so they can act as reference detectors, recording 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 that slightly changes the way their surfaces conduct electricity.
One possibility is that the excess dust was actually produced closer to the sun and was blown out of the Kuiper Belt by the pressure of sunlight acting on the particles. However, Doner’s team considered this theory unlikely. Instead, more tempting odds are in favor, they say.
Perhaps there is more to the Kuiper Belt than astronomers realized.
The continued presence of dust suggests that New Horizons is still within the Kuiper Belt, and that the Kuiper Belt is much more extensive than anyone knew, stretching across billions of miles further from the sun than thought our current maps.
It’s not just the dust counts that tell us this. Astronomers are using it machine learning algorithms to search for observations made by the Subaru 8.2-meter Telescope on Mauna Kea in Hawaii, and the Victor M. Blanco Four-Meter Telescope at the Cerro Tololo Inter-American Observatory in Chile to look for more icy objects that New Horizons could investigate . . So far they’ve found 154 objects in the direction New Horizons is headed, including about 20 that the spacecraft will come within a few million miles of, close enough for some basic observations. But some of those 154 objects appear to be located outside the Kuiper Belt, and not on the type of eccentric orbit suggested by the Scattered Disk, but in the ecliptic plane shared by the Kuiper Belt as well.
Are they members of the wider Kuiper Belt, or perhaps even a second belt?
“The idea that we might have discovered an extended Kuiper Belt – with a whole new population of objects colliding and producing more dust – adds another clue to solving the mysteries of the outermost regions of the solar system,” Doner said. .
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New Horizons is sailing through uncharted waters. Only four spacecraft have passed this way before – Pioneers 10 and 11, and Voyager 1 and Game Voyager 2; none were equipped with a dust counter like New Horizons.
Although the Pioneers have been inactive for as long as the Voyager 1 spacecraft starting to fall, New Horizons has enough fuel and power to survive well into the 2040s, when it could be well beyond 100 AU from the Sun. By the time its power declines, it will likely have completely retracted the map of the outer solar system.
The new results from the SDC were published on 1 February Astrophysical Journal Letters.
