a few centimeters deepending on the energy
About 10cm.
Just a few inches.
An alpha particle with energy of 4.0 MeV from Thorium-232 decay can travel less than 28 microns in body fluids.
Toliman (Alpha Centauri) is at a distance of 4.3 light-years. That means it would take a ray of light 4.3 years to travel from here to Toliman, or from Toliman to here.
There is not an Alpha Travel Agency in the UK (United Kingdom).
Alpha particles have a range of a few centimeters in air and are stopped by a sheet of paper or human skin. Their penetration range in tissue is limited to a few cells.
This depends on their energy. An alpha particle that comes from nuclear decay is usually only able to travel a short distance, a few centimeters, through air. Alpha particles as cosmic rays, however, are much more energetic, and can penetrate quite deeply, even through many meters of solid shielding. These can penetrate the atmosphere.
It Travels a few centimeters in air as the have weak energy.
The nearest star is more than 4 light-years away, we do not have the technology to travel that far within a human lifetime.
Alpha particles from Thorium-232 decay have very low penetration power and can typically travel only a few centimeters in body fluids. This means that the surrounding tissues within a short distance of the particle's source would be affected by its radiation.
"Too far to travel for you"
It is used in smoke detectors as it cannot travel far in air. Alpha radiation is emitted and as long as the detector in the device is receiving the alpha radiation, then no smoke is present. When smoke particles are present, they interrupt the radiation, and so the detector doesn't pick up the radiation, causing the alarm to go off.