Dawn of Aurora Season
Absinthe-green Auroras course across the Yukon sky in a picture featured March 11 on NASA's Astronomy Photo of the Day site. Captured around dawn on March 11 near Dawson City, Canada, the image is a digital combination of several exposures, which allowed both the northern lights and the paths of stars—which appear to be moving due to Earth's rotation—to shine.
With the vernal equinox, or spring equinox, arriving on Saturday, northern lights should be in abundance this week. For reasons that remain a mystery, the sky shows tend to proliferate around the first day of spring, according to NASA.
Auroras occur as particles from the sun speed toward Earth and become energized as they encounter with the planet's magnetic field lines. As the powered-up particles smash into oxygen and nitrogen in our atmosphere, the particles release their energy as red, green, and blue light. (See aurora pictures.)
(Related: "Giant 'Space Tornadoes' Spark Auroras on Earth.")
Space Photos This Week: Spring Auroras, Starlets, More
Auroras spring to life, the Milky Way enters middle age, a Mars moon gets its close-up, and more in the week's best space pictures.