2024 October 31
Explanation: By starlight, this eerie visage shines in the dark with a crooked profile evoking its popular name, the Witch Head Nebula. In fact, this entrancing telescopic portrait gives the impression that a witch has fixed her gaze on Orion's bright supergiant star Rigel. More formally known as IC 2118, the Witch Head Nebula spans about 50 light-years and is composed of interstellar dust grains reflecting Rigel's starlight. The color of the Witch Head Nebula is caused not only by Rigel's intense blue light, but because the dust grains scatter blue light more efficiently than red. The same physical process causes Earth's daytime sky to appear blue, although the scatterers in Earth's atmosphere are molecules of nitrogen and oxygen. Rigel and this dusty cosmic crone are about 800 light-years away. You may still see a few witches in your neighborhood tonight though, so have a safe and Happy Halloween!
2024 October 30
Explanation: What created this huge space bubble? Blown by the wind from a star, this tantalizing, head-like apparition is cataloged as NGC 7635, but known simply as the Bubble Nebula. The featured striking view utilizes a long exposure to reveal the intricate details of this cosmic bubble and its environment. Although it looks delicate, the 10 light-year diameter bubble offers evidence of violent processes at work. Seen here above and right of the Bubble's center, a bright hot star is embedded in the nebula's reflecting dust. A fierce stellar wind and intense radiation from the star, which likely has a mass 10 to 20 times that of the Sun, has blasted out the structure of glowing gas against denser material in a surrounding molecular cloud. The intriguing Bubble Nebula lies a mere 11,000 light-years away toward the boastful constellation Cassiopeia.
2024 October 29
Explanation: The stars are destroying the pillars. More specifically, some of the newly formed stars in the image center are emitting light so energetic that is evaporating the gas and dust in the surrounding pillars. Simultaneously, the pillars themselves are still trying to form new stars. The whole setting is the star cluster NGC 602, and this new vista was taken by the Webb Space Telescope in multiple infrared colors. In comparison, a roll-over image shows the same star cluster in visible light, taken previously by the Hubble Space Telescope. NGC 602 is located near the perimeter of the Small Magellanic Cloud (SMC), a small satellite galaxy of our Milky Way galaxy. At the estimated distance of the SMC, the featured picture spans about 200 light-years. A tantalizing assortment of background galaxies are also visible -- mostly around the edges -- that are at least hundreds of millions of light-years beyond.
2024 October 28
Explanation: Sometimes a river of hot gas flows over your head. In this case the river created a Strong Thermal Emission Velocity Enhancement (STEVE) that glowed bright red, white, and pink. Details of how STEVEs work remain a topic of research, but recent evidence holds that their glow results from a fast-moving river of hot ions flowing over a hundred kilometers up in the Earth's atmosphere: the ionosphere. The more expansive dull red glow might be related to the flowing STEVE, but alternatively might be a Stable Auroral Red (SAR) arc, a more general heat-related glow. The featured picture, taken earlier this month in Côte d'Opale, France, is a wide-angle digital composite made as the STEVE arc formed nearly overhead. Although the apparition lasted only a few minutes, this was long enough for the quick-thinking astrophotographer to get in the picture -- can you find him?
