Space at
your fingertips.
"I want to know why the universe exist, why there is something greater than nothing."
Steven Hawking
Scientist, Space Lover
How do stars form? Images of the star forming region W5 like those in the infrared by NASA's Wide Field Infrared Survey Explorer (WISE) satellite provide clear clues with indications that massive stars near the center of empty cavities are older than stars near the edges. A likely reason for this is that the older stars in the center are actually triggering the formation of the younger edge stars. The triggered star formation occurs when hot outflowing gas compresses cooler gas into knots dense enough to gravitationally contract into stars. In the featured scientifically-colored infrared image, spectacular pillars, left slowly evaporating from the hot outflowing gas, provide further visual clues. W5 is also known as IC 1848, and together with IC 1805 form a complex region of star formation popularly dubbed the Heart and Soul Nebulas. The above image highlights a part of W5 spanning about 2,000 light years that is rich in star forming pillars. W5 lies about 6,500 light years away toward the constellation of Cassiopeia. Now Available: APOD 2015 Wall Calendars
Looking toward the south from low Earth orbit, the crew of the Space Shuttle Endeavor made this stunning time exposure of the Aurora Australis or southern lights in April of 1994. Aurora are visible at high northern latitudes as well, with the northern lights known as Aurora Borealis. They are caused by high energy electrons from the Solar Wind which are funneled into the atmosphere near the poles by the Earth's magnetic field. The reddish colors occur at the highest altitudes (about 200 miles) where the air is least dense. At lower altitudes and greater densities green tends to dominate ranging to a pinkish glow at the lowest. The familiar constellation of Orion the Hunter is clearly visible above the dark horizon in the background. Because of the shuttle's orbital motion, the bright stars in Orion appear slightly elongated.
It's clear who is the biggest star in this binary system. Based on recent results, this artist's vision of the double star Phi Persei, 720 light years away, shows a bright, rapidly rotating massive star surrounded by a disk of gas. A small companion star orbits 100 million miles away. The bigger star is presently about 9 times more massive than the small one ... but it wasn't always this way. Ten million years ago the small companion was actually the most massive star in the system and because of its greater mass evolved into a giant star more quickly. After losing its swollen outer layers to the now massive star, all that remains is a stripped down, intensely hot core of about 1 solar mass. In another ten million years, the roles may reverse as the now massive star swells into its own giant phase "returning" mass to its companion. Will these stars end their lives as white dwarfs or supernovae? Astronomers consider the ultimate fate of such mass-exchanging, interacting binary systems an open question and a challenge for present theories of stellar evolution.
Expanse