NASA DART mission and planetary defense.

"This illustration depicts NASA’s Double Asteroid Redirection Test (DART) spacecraft prior to impact at the Didymos binary asteroid system." 

"NASA’s Double Asteroid Redirection Test (DART) mission is a pioneering planetary defense initiative aimed at testing methods for preventing a potentially hazardous asteroid from colliding with Earth. Launched in November 2021, DART was designed to target the asteroid moonlet Dimorphos, which orbits the larger asteroid Didymos. The mission involved navigating a spacecraft to intentionally collide with Dimorphos at high speed in September 2022. " (https://scitechdaily.com/tag/dart/)

"This kinetic impact technique was intended to slightly alter the asteroid’s trajectory, demonstrating a viable method to deflect objects that could pose a future threat to Earth. The mission’s success was confirmed when telescopic observations showed that DART had successfully changed Dimorphos’s orbit around Didymos. This experiment marked the first time humanity has altered the dynamics of a celestial body in a measurable way, providing valuable data for developing strategies against potential asteroid threats." (https://scitechdaily.com/tag/dart/)

"On Sept. 26, 2022, DART impacted the asteroid moonlet Dimorphos, a small body just 530 feet (160 meters) in diameter. It orbits a larger, 2,560-foot (780-meter) asteroid called Didymos." 

The idea was to effect asteroid trajectory through its moon. The DART impacts the asteroid moon, and then the moon's gravity effect changes the asteroid and its moon's trajectory. 

The planetary defense against asteroids is one of the most important things for safety on Earth. The small asteroids with a size of less than 200 meters are a big threat to people if some of them fall on the cities. And those asteroids are sometimes noticed after they bypass Earth. Some of those asteroids travel through inside the satellite trajectories, and that causes a situation where the asteroid almost hits to satellites. Or even jumps out from the atmosphere, and some satellites see the asteroid. 

Above: DART mission profile. 

The NASA Double Asteroid Redirection Test, DART mission had the purpose of testing the kinetic energy penetrators that should push asteroids out from their trajectory. The DART pushed the asteroid moonlet Dimorphos out from the trajectory. 

That helps to avoid those destructive impacts. Some people are afraid that the penetrators crush the asteroid. The small bites are safer for people on Earth. But they can cause large-scale damage to satellites that orbit outside the atmosphere. 

In some visions the rocket engine will dock to asteroid, and it will push it away from the trajectory. The small asteroid can be put into the mylar bag, that is used in solar sails. And then the space rocket pulls it into a safer trajectory. In some proposes the laser ray will shoot to the asteroid, and then it pushes that asteroid away. 

All those proposes require that somebody notices that asteroid early enough. The last possibility is to shoot that asteroid with missiles that can break it into smaller parts. The problem is that the same systems that are used for planetary defense are capable of the antisatellite, ASAT weapons. The DART collided with the asteroid's moonlet, but that kind of system could also shoot metal rods at the cities if it wanted to use them as an orbital bombardment system. 

"Artist's conception of a Jupiter-size rogue planet."

The rogue planets are also one threat. 

The JWST telescope found six new rogue planets from the Milky Way. Most of those starless planets that travel around space might be remnants of the solar systems their supernova or nova pushed them away to space.  There are lots of late M, like M9, Y, and T spectral class sub-brown dwarfs. But when we look at those brown dwarfs most of them produce thermal energy sometimes. And that keeps their surface quite warm. That makes it possible to see those rogue objects using infrared telescopes. 

The rogue dwarf planets are also a big threat. If a 400-kilometer-size rogue dwarf planet hits some other planet in our solar system, that thing can push debris all around the solar system. Those small dwarf planets can also travel in the Milky Way. 

But those objects that produce their own thermal energy forming the model, there are lots of large, smaller objects that travel away from solar systems. Some of those objects can be icy Jupiters, that the explosion of the star threw out to space. And there is much more moon- or Earth-size clod objects that we cannot see. 

The size of Earth is here because Earth is the largest rocky planet in our solar system. But those small icy exoplanets or dwarf exoplanets can be the size of the moon or maybe the size of the Ceres or Vesta. The small 400-kilometer size exoplanets can cause very bad problems if they travel into our solar system. 

"NASA’s DART mission disrupted the asteroid moon Dimorphos, reshaping its trajectory and form, revealing new insights into asteroid behavior and providing critical data for future asteroid deflection strategies. Credit: NASA" 

"NASA’s DART spacecraft is due to collide with the smaller body of the Didymos binary asteroid system in October 2022. ESA’s Hera mission will survey ‘Didymoon’ post-impact and assess how its orbit has been changed by the collision, to turn this one-off experiment into a workable planetary defense technique. Credit: ESA–ScienceOffice.org

Maybe someday antimatter will save us. 

Those rogue dwarf planets can require more powerful systems than DART. In some visions, the antimatter bombs or antimatter cannons can someday save the world. The antimatter bomb or Teller's bomb is the magnet chamber. The antimatter hovers in those chambers. And when those anti-particles interact with the material, that causes detonation. The problem is that the 1g of antimatter can destroy Earth. The energy impact simply vaporizes Earth and transforms it into a molecular cloud.

The antimatter cannon is the particle accelerator or ion cannon that shoots antimatter ions like antiprotons or positrons into the target. Researchers can install that system into the ion cannon. The laser beam can give more speed and energy to those ions that travel in the laser ray. The antimatter system can turn even large-size incoming objects into a molecular cloud. Unlike hydrogen bombs, the antimatter system doesn't form debris. And that makes the system effective to use as a planetary defense. But the problem is that some people see this kind of system as doomsday weapons.  And in the wrong hands, they are horrible. 

https://dart.jhuapl.edu/

https://science.nasa.gov/mission/dart

https://scitechdaily.com/nasas-dart-crashing-into-discovery-with-worlds-first-planetary-defense-test/

https://scitechdaily.com/nasas-dart-impact-asteroid-moon-permanently-transformed/

https://scitechdaily.com/nasas-dart-impact-changed-asteroids-shape-and-orbit/

https://scitechdaily.com/rogue-worlds-webb-telescope-discovers-6-starless-planets-in-the-milky-way/

https://scitechdaily.com/tag/dart/

https://techcrunch.com/2021/10/04/nasas-armageddon-style-asteroid-deflection-mission-takes-off-in-november/

https://en.wikipedia.org/wiki/Brown_dwarf

https://en.wikipedia.org/wiki/Rogue_planet

https://en.wikipedia.org/wiki/Stellar_classification