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Explanation: Sit back and watch a star explode. The actual supernova occurred back when dinosaurs roamed the Earth, but images of the spectacular event began arriving last year. Supernova 2015F was discovered in nearby spiral galaxy NGC 2442 by Berto Monard in 2015 March and was unusually bright -- enough to be seen with only a small telescope. The pattern of brightness variation indicated a Type Ia supernova -- a type of stellar explosion that results when an Earth-size white dwarf gains so much mass that its core crosses the threshold of nuclear fusion, possibly caused by a lower mass...

Explanation: What's the closest active galaxy to planet Earth? That would be Centaurus A, only 11 million light-years distant. Spanning over 60,000 light-years, the peculiar elliptical galaxy is also known as NGC 5128. Forged in a collision of two otherwise normal galaxies, Centaurus A's fantastic jumble of young blue star clusters, pinkish star forming regions, and imposing dark dust lanes are seen here in remarkable detail. The colorful galaxy portrait is a composite of image data from space- and ground-based telescopes large and small. Near the galaxy's center, left over cosmic debris is steadily being consumed by a central black...

Explanation: Big, bright, and beautiful, spiral galaxy M83 lies a mere twelve million light-years away, near the southeastern tip of the very long constellation Hydra. Prominent spiral arms traced by dark dust lanes and blue star clusters lend this galaxy its popular name, The Southern Pinwheel. But reddish star forming regions that dot the sweeping arms highlighted in this sparkling color composite also suggest another nickname, The Thousand-Ruby Galaxy. About 40,000 light-years across, M83 is a member of a group of galaxies that includes active galaxy Centaurus A. In fact, the core of M83 itself is bright at x-ray energies,...

Explanation: What's happened to the center of this galaxy? Unusual and dramatic dust lanes run across the center of elliptical galaxy Centaurus A. These dust lanes are so thick they almost completely obscure the galaxy's center in visible light. This is particularly unusual as Cen A's red stars and round shape are characteristic of a giant elliptical galaxy, a galaxy type usually low in dark dust. Cen A, also known as NGC 5128, is also unusual compared to an average elliptical galaxy because it contains a higher proportion of young blue stars and is a very strong source of radio...

Explanation: What causes the surrounding shells in peculiar galaxy Cen A? In 2002 a fascinating image of peculiar galaxy Centaurus A was released, processed to highlight a faint blue arc indicating an ongoing collision with a smaller galaxy. Another interesting feature of Cen A, however, is the surrounding system of shells, better visible here in this recently released wider pan from the four meter Blanco telescope at Cerro Tololo Inter-American Observatory. Faint shells around galaxies are not unusual and considered by themselves as evidence of a previous galaxy merger, analogous to water ripples on a pond. An unexpected attribute of...

Explanation: What's the closest active galaxy to planet Earth? That would be Centaurus A, only 11 million light-years distant. Spanning over 60,000 light-years, the peculiar elliptical galaxy is also known as NGC 5128. Forged in a collision of two otherwise normal galaxies, Centaurus A's fantastic jumble of young blue star clusters, pinkish star forming regions, and imposing dark dust lanes are seen here in remarkable detail. The colorful galaxy portrait was recorded under clear Chilean skies at the Cerro Tololo Inter-American Observatory. Near the galaxy's center, left over cosmic debris is steadily being consumed by a central black hole with...

Explanation: A fantastic jumble of young blue star clusters, gigantic glowing gas clouds, and imposing dark dust lanes surrounds the central region of the active galaxy Centaurus A. This image from the Hubble Space Telescope has been processed to present a natural color picture of this cosmic maelstrom. Infrared images from the Hubble have also shown that hidden at the center of this activity are what seem to be disks of matter spiraling into a black hole with a billion times the mass of the Sun. Centaurus A itself is apparently the result of a collision of two galaxies and...

[Credit: ESO/WFI (visible); MPIfR/ESO/APEX/A. Weiss et al. (microwave); NASA/CXC/CfA/R. Kraft et al. (X-ray); Inset: NASA/TANAMI/C. Müller et al. (radio)] Explanation: Jets of streaming plasma expelled by the central black hole of a massive spiral galaxy light up this composite image of Centaurus A. The jets emanating from Cen A are over a million light years long. Exactly how the central black hole expels infalling matter is still unknown. After clearing the galaxy, however, the jets inflate large radio bubbles that likely glow for millions of years. If excited by a passing front, radio bubbles can even light up again after...

Astronomy Picture of the Day Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer. 2002 October 17 Centaurus A: Young Blue Star Stream Credit: E. Peng and H. Ford (JHU), K. Freeman (ANU), R. White (STScI), CTIO, NOAO, NSF Explanation: Almost lost in this cosmic jumble of stars, gas and dust is a faint but definite blue arc -- a stream of young stars whose formation was probably triggered as a small dwarf galaxy was torn apart approaching the giant elliptical galaxy...

Astronomy Picture of the Day Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer. 2002 August 12 The Colors and Mysteries of Centaurus A Credit: X-ray (NASA/CXC/M. Karovska et al.); Radio 21-cm image (NRAO/VLA/Schiminovich, et al.), Radio continuum image (NRAO/VLA/J.Condon et al.); Optical (Digitized Sky Survey, U.K. Schmidt Image/ STScI) Explanation: Why is spiral galaxy Centaurus A in so much turmoil? The above composite image shows different clues to the unusual galaxy's past in different bands of light. In low energy radio...