22.02.2024
NASA’s New Horizons Detects Dusty Hints of Extended Kuiper Belt
New observations from NASA’s New Horizons spacecraft hint that the Kuiper Belt – the vast, distant outer zone of our solar system populated by hundreds of thousands of icy, rocky planetary building blocks – might stretch much farther out than we thought.
Speeding through the outer edges of the Kuiper Belt, almost 60 times farther from the Sun than Earth, the New Horizons Venetia Burney Student Dust Counter (SDC) instrument is detecting higher than expected levels of dust – the tiny frozen remnants of collisions between larger Kuiper Belt objects (KBOs) and particles kicked up from KBOs being peppered by microscopic dust impactors from outside of the solar system.
The readings defy scientific models that the KBO population and density of dust should start to decline a billion miles inside that distance and contribute to a growing body of evidence that suggests the outer edge of the main Kuiper Belt could extend billions of miles farther than current estimates – or that there could even be a second belt beyond the one we already know.
The results appear in the Feb. 1 issue of the Astrophysical Journal Letters.
“New Horizons is making the first direct measurements of interplanetary dust far beyond Neptune and Pluto, so every observation could lead to a discovery,” said Alex Doner, lead author of the paper and a physics graduate student at the University of Colorado Boulder who serves as SDC lead. “The idea that we might have detected an extended Kuiper Belt — with a whole new population of objects colliding and producing more dust – offers another clue in solving the mysteries of the solar system’s most distant regions.”
Designed and built by students at the Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado Boulder under the guidance of professional engineers, SDC has detected microscopic dust grains produced by collisions among asteroids, comets and Kuiper Belt objects all along New Horizons’ 5-billion-mile, 18-year journey across our solar system – which after launch in 2006 included historic flybys of Pluto in 2015 and the KBO Arrokoth in 2019. The first science instrument on a NASA planetary mission to be designed, built and “flown” by students, the SDC counts and measures the sizes of dust particles, producing information on the collision rates of such bodies in the outer solar system.
The latest, surprising results were compiled over three years as New Horizons traveled from 45 to 55 astronomical units (AU) from the Sun – with one AU being the distance between Earth and Sun, about 93 million miles or 140 million kilometers.
These readings come as New Horizons scientists, using observatories like the Japanese Subaru Telescope in Hawaii, have also discovered a number KBOs far beyond the traditional outer edge of the Kuiper Belt. This outer edge (where the density of objects starts to decline) was thought to be at about 50 AU, but new evidence suggests the belt may extend to 80 AU, or farther.
As telescope observations continue, Doner said, scientists are looking at other possible reasons for the high SDC dust readings. One possibility, perhaps less likely, is radiation pressure and other factors pushing dust created in the inner Kuiper Belt out past 50 AU. New Horizons could also have encountered shorter-lived ice particles that cannot reach the inner parts of the solar system and were not yet accounted for in the current models of the Kuiper Belt.
“These new scientific results from New Horizons may be the first time that any spacecraft has discovered a new population of bodies in our solar system,” said Alan Stern, New Horizons principal investigator from the Southwest Research Institute in Boulder. “I can’t wait to see how much farther out these elevated Kuiper Belt dust levels go.”
Now into its second extended mission, New Horizons is expected to have sufficient propellant and power to operate through the 2040s, at distances beyond 100 AU from the Sun. That far out, mission scientists say, the SDC could potentially even record the spacecraft’s transition into a region where interstellar particles dominate the dust environment. With complementary telescopic observations of the Kuiper Belt from Earth, New Horizons, as the only spacecraft operating in and collecting new information about the Kuiper Belt, has a unique opportunity to learn more about KBOs, dust sources and expanse of the belt, and interstellar dust and the dust disks around other stars.
The Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, built and operates the New Horizons spacecraft and manages the mission for NASA’s Science Mission Directorate. Southwest Research Institute, based in San Antonio and Boulder, Colorado, directs the mission via Principal Investigator Alan Stern and leads the science team, payload operations and encounter science planning. New Horizons is part of NASA’s New Frontiers program, managed by NASA’s Marshall Space Flight Center in Huntsville, Alabama.
Quelle: NASA
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Update: 4.07.2025
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NASA’s New Horizons Demonstrates Deep-Space Navigation First
While spacecraft can use stars to get a sense of direction, figuring out how far and where a spacecraft has traveled from home usually requires accurate radio tracking from Earth. But members of NASA’s New Horizons team – using the mission’s spacecraft, now more than five billion miles from Earth – have demonstrated for the first time that it’s possible to determine direction and distance just by examining images the spacecraft snaps of star fields.
“As a spacecraft travels deeper into space, the positions of the stars seen from its location begin to shift from where they are seen from Earth,” explained Tod Lauer, an astrophysicist and New Horizons science team member from the National Optical-Infrared Astronomy Research Laboratory in Tucson, Arizona. “A spacecraft voyaging out into the Milky Way can measure these shifts, due to an effect called parallax, to locate where it is with respect to nearby stars. New Horizons has traveled far enough away that it can provide the first true demonstration of interstellar navigation.”
Since its launch in 2006, New Horizons has been on a trajectory that brought it past Pluto and then Kuiper Belt object Arrokoth and will eventually take it out of the solar system, into interstellar space over the next decade. In 2020, the New Horizons science team, in an effort led by Lauer, obtained images of the star fields around the nearby stars Proxima Centauri and Wolf 359 simultaneously from New Horizons and Earth. This program vividly demonstrated New Horizons’ change in perspective as it ventured from the inner to the outer solar system.
But more recent and sophisticated analyses of the exact positions of the two stars in those 2020 images allowed Lauer, working with retired Lawrence Livermore National Laboratory researcher David Munro, as well as members of the New Horizons team and external collaborators, to deduce New Horizons’ three-dimensional position relative to nearby stars – accomplishing the first use of stars imaged directly from a spacecraft to provide its navigational fix, and the first demonstration of interstellar navigation by any spacecraft on an interstellar trajectory.
The team published the results of its investigation June 30 in The Astronomical Journal; the paper is also available on the arXiv website.
“This pioneering interstellar navigation demonstration and its accompanying publication show that a deep-space mission can use its onboard imaging system to find its way among the stars,” said Alan Stern, principal investigator for New Horizons from the Southwest Research Institute in Boulder, Colorado. “While for New Horizons, this method isn’t as accurate as NASA’s sophisticated tracking from Earth, it could be highly useful for future deep space missions in the far reaches of the solar system and in interstellar space.”
Navigating from Earth
Most interplanetary spacecraft, including New Horizons, are tracked by NASA’s Deep Space Network (DSN) of radio telescopes. Engineers use the precise time it takes DSN signals, traveling at the speed of light, to reach the spacecraft to make highly accurate distance measurements. Simultaneous ranging from two DSN stations, located 180 degrees apart on Earth, provides a precise direction to the spacecraft.
Separately, obtaining precise positions with respect to X-ray pulsars in the Milky Way had been demonstrated for spacecraft navigation in low-orbit around the Earth, but not (yet) for a deep space mission.
While in standard celestial navigation the stars are assumed to be in fixed locations, in interstellar navigation, one determines how the nearby stars have appeared to shift against more distant stars to establish the spacecraft’s location in all three dimensions. In contrast, for navigation with DSN, the position of the spacecraft remains linked to and dependent on knowing the location of Earth.
Pure interstellar navigation, like what New Horizons demonstrated, is based on the ultra-precise 3D map of the Milky Way provided by ESA’s (European Space Agency’s) Gaia mission. Images obtained with New Horizons’ Long Range Reconnaissance Imager (LORRI) captured the positions of Proxima Centauri and Wolf 349 relative to much more distant background stars. Two stars are required to determine position; significantly, Proxima Centauri and Wolf 349 are positioned almost 90 degrees apart in the sky, providing nearly optimal leverage to determine New Horizons’ location.
During the April 2020 demonstration, New Horizons was 46.9 times the distance of the Earth to the Sun – about 4.36 billion miles (7.02 billion kilometers) – and would appear to be in the constellation of Sagittarius, close to the center of the Milky Way, as seen from Earth.
In 2020, the New Horizons science team obtained images of the star fields around the nearby stars Proxima Centauri (top) and Wolf 359 (bottom) simultaneously from New Horizons and Earth. More recent and sophisticated analyses of the exact positions of the two stars in these images allowed the team to deduce New Horizons’ three-dimensional position relative to nearby stars – accomplishing the first use of stars imaged directly from a spacecraft to provide its navigational fix, and the first demonstration of interstellar navigation by any spacecraft on an interstellar trajectory.
Learn more about these images and the parallax effect here.
Credit: NASA/Johns Hopkins APL/SwRI
Lauer’s team cautions that the accuracy of this first demonstration of interstellar navigation is limited by LORRI’s relatively low angular resolution, since it was not developed to obtain ultra-precise positions of stars. The range to New Horizons estimated from the stellar imagery was roughly close to the actual distance – 47.1 times the Earth-Sun distance, compared to the DSN-derived distance of 46.9 times – and its direction on the sky was accurate to a patch a little smaller than the scale of the full Moon as seen from Earth.
“The measurements were within our expected range of uncertainty for LORRI, but future deep space missions with high-resolution navigation imagers should be able to achieve dramatically better positions, using this same technique” Lauer added.
The Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, designed, built, and operates the New Horizons spacecraft and manages the mission for NASA's Science Mission Directorate and the mission’s principal investigator. Southwest Research Institute, based in San Antonio, Texas, directs the mission via Principal Investigator Alan Stern, who leads the mission for NASA. NASA Marshall Space Flight Center’s Planetary Management Office in Huntsville, Alabama, provides NASA oversight for New Horizons.
Location of NASA’s New Horizons spacecraft on April 23, 2020, derived from the spacecraft’s own images of the Proxima Centauri and Wolf 359 star fields. The positions of Proxima Centauri and Wolf 359 are strongly displaced compared to distant stars from where they are seen on Earth. The position of Proxima Centauri seen from New Horizons means the spacecraft must be somewhere on the red line, while the observed position of Wolf 359 means that the spacecraft must be somewhere on the blue line – putting New Horizons approximately where the two lines appear to “intersect” (in the real three dimensions involved, the lines don’t actually intersect, but do pass close to each other). The white line marks the accurate Deep Space Network-tracked trajectory of New Horizons since its launch in 2006.
The lines on the New Horizons trajectory denote years since launch. The orbits of Jupiter, Saturn, Uranus, Neptune and Pluto are shown. Distances are from the center of the solar system in astronomical units, where 1 AU is the average distance between the Sun and Earth.
Credit: NASA/Johns Hopkins APL/SwRI/Matthew Wallace
Quelle: NASA