Astronomy Picture of the Day

Explanation: These Hubble Space Telescope (HST) images reveal glimpses of the dynamic atmosphere of Neptune, the Solar System's most distant gas giant planet. The first close-up of Neptune's clouds was provided by NASA's Voyager 2 spacecraft during its August 1989 flyby, giving a tantalizingly brief look. From its vantage point in Earth orbit, HST can patiently watch in detail as the planet's massive weather systems change over time. These three pictures, taken during October and November 1994 when Neptune was only 2.8 billion miles distant, show the planet's characteristic aqua-blue coloured atmosphere highlighted by pink, high altitude clouds and streaked with dark bands. The aqua-blue colour is caused by gaseous methane which absorbs red light. Here, the high altitude clouds were intentionally given a pink tint to indicate that they were imaged in near infrared light - in true colour images they would appear white.