Potentially Hazardous Asteroids (PHAs) are space rocks larger than approximately 100m that can come closer to Earth than 0.05 AU. None of the known PHAs is on a collision course with our planet, although astronomers are finding new ones all the time. On April 16, 2017 there were 11 potentially hazardous asteroids.
Radiation therapy is often delivered from a machine outside the body. One of the most common side effects is a skin condition called radiation dermatitis, which can range from a mild, red rash (erythema) and itchy, peeling or flaking skin (dry desquamation) to a more severe reaction with blisters and wet, peeling skin (moist desquamation).
Sunburn blisters are a result of overexposure to the UVA and UVB rays in the sun. These harmful rays penetrate deep into the bottom skin layers and damage the production of new skin cells. High doses of UVA rays will cause sunburn blisters. Regular exposure to UVA rays will result in wrinkles and dry skin.