The International Space Station Transits the Sun - 2008-07-30

That's no sunspot. It's the International Space Station (ISS) caught by chance passing in front of the Sun. Sunspots, individually, have a dark central umbra, a lighter surrounding penumbra, and no solar panels. By contrast, the ISS is a complex and multi-spired mechanism, one of the largest and most sophisticated machines ever created by humanity. Also, sunspots occur on the Sun, whereas the ISS orbits the Earth. Transiting the Sun is not very unusual for the ISS, which orbits the Earth about every 90 minutes, but getting one's timing and equipment just right for a great image is rare. Strangely, besides that fake spot, the Sun, last week, lacked any real sunspots. Sunspots have been rare on the Sun since the dawn of the current Solar Minimum, a period of low solar activity. Although fewer sunspots have been recorded during this Solar Minimum than for many previous decades, the low solar activity is not, as yet, very unusual.  

Namibian Nights - 2013-02-04

Namibia has some of the darkest nights visible from any continent. It is therefore home to some of the more spectacular skyscapes, a few of which have been captured in the above time-lapse video. Visible at the movie start are unusual quiver trees perched before a deep starfield highlighted by the central band of our Milky Way Galaxy. This bright band of stars and gas appears to pivot around the celestial south pole as our Earth rotates. The remains of camel thorn trees are then seen against a sky that includes a fuzzy patch on the far right that is the Large Magellanic Cloud, a small satellite galaxy to the Milky Way. A bright sunlight-reflecting satellite passes quickly overhead. Quiver trees appear again, now showing their unusual trunks, while the Small Magellanic Cloud becomes clearly visible in the background. Artificial lights illuminate a mist that surround camel thorn trees in Deadvlei. In the final sequence, natural Namibian stone arches are captured against the advancing shadows of the setting moon. This video incorporates over 16,000 images shot over two years, and won top honors among the 2012 Travel Photographer of the Year awards. Poll: Choose your favorite January APODs  

Jupiter's Clouds from New Horizons - 2016-06-26

The New Horizons spacecraft took some stunning images of Jupiter on its way out to Pluto. Famous for its Great Red Spot, Jupiter is also known for its regular, equatorial cloud bands, visible through even modest sized telescopes. The featured image, horizontally compressed, was taken in 2007 near Jupiter's terminator and shows the Jovian giant's wide diversity of cloud patterns. On the far left are clouds closest to Jupiter's South Pole. Here turbulent whirlpools and swirls are seen in a dark region, dubbed a belt, that rings the planet. Even light colored regions, called zones, show tremendous structure, complete with complex wave patterns. The energy that drives these waves surely comes from below. New Horizons is the fastest space probe ever launched, has successfully complete its main flyby of Pluto in 2015, and is now heading further out and on track to flyby Kuiper belt object 2014 MU69 in 2019. In the near term, many space enthusiasts excitedly await Juno's arrival at Jupiter next Monday. APOD in Poster Format: PDF, JPG, Powerpoint  

Simulation: A Disk Galaxy Forms - 2023-05-31

How did we get here? We know that we live on a planet orbiting a star orbiting a galaxy, but how did all of this form? Since our universe moves too slowly to watch, faster-moving computer simulations are created to help find out. Specifically, this featured video from the IllustrisTNG collaboration tracks gas from the early universe (redshift 12) until today (redshift 0). As the simulation begins, ambient gas falls into and accumulates in a region of relatively high gravity. After a few billion years, a well-defined center materializes from a strange and fascinating cosmic dance. Gas blobs -- some representing small satellite galaxies -- continue to fall into and become absorbed by the rotating galaxy as the present epoch is reached and the video ends. For the Milky Way Galaxy, however, big mergers may not be over -- recent evidence indicates that our large spiral disk Galaxy will collide and coalesce with the slightly larger Andromeda spiral disk galaxy in the next few billion years. Open Science: Browse 3,000+ codes in the Astrophysics Source Code Library  

Black Holes in Galactic Centers - 1999-10-17

Do all galaxies have black holes at their centers? Although not even a single galaxy has yet been proven to have a central black hole, the list of candidates continues to increase. Results by astronomers using instruments like the Hubble Space Telescope now indicate that most - and possibly even all - large galaxies may harbor one of these dense beasts. In all the galaxies studied, star speeds continue to increase closer the very center. This in itself indicates a center millions of times more massive than our Sun is needed to contain the stars. This mass when combined with the limiting size make the case for the central black holes. Will we ever know for sure?