Have you seen a great image or video somewhere that you think would make a great APOD? Nominate it for APOD! Please post as much information here as you have about the image/video with a link to any source(s) for it you know of here, and the editors will take a look.
When posting the image itself, please do not post anything larger than a thumbnail here; please honor the copyright holder's copyright.
I love this picture! What splendid colors! Note the faint extended outer spiral arms of M100, made of old stars. Note the numerous satellite galaxies, most of them "red and dead", but one, at 3 o'clock, faint and blue.
Astronomers using the ESO observatories might be a common sight in the Chilean Atacama Desert these days, but they were by no means the first people to call the area home.
Although the desert is now dry and inhospitable, it once experienced more abundant rainfall and possessed a far more diverse flora. It has hosted various human civilisations, from the El Molle culture of 700–800 CE through to the Las Ánimas (800–1200 CE) and Diaguita (1200 CE to mid-15th century) peoples. Following the 15th-century Peruvian Inca conquests, the local culture became a mix of Inca and Diaguita. This lasted until the onset of the Spanish conquest in the 1530s, which put an end to an indigenously inhabited Atacama.
Signs of this past can be found throughout the area surrounding ESO’s La Silla Observatory. Numerous rocks boasting thousand-year-old carvings — petroglyphs — can be found scattered throughout the region, thought to be remnants of the El Molle complex. While some drawings depict humans and animals, usually llamas, most show abstract geometrical figures including rectangles, maze-like designs, circles, and circles with rays.
This seemingly unspectacular series of dots with varying distances between them actually shows the slow waltz of two brown dwarfs. The image is a stack of 12 images made over the course of three years with the NASA/ESA Hubble Space Telescope. Using high-precision astrometry, an Italian-led team of astronomers tracked the two components of the system as they moved both across the sky and around each other.
The observed system, Luhman 16AB, is only about six light-years away and is the third closest stellar system to Earth — after the triple star system Alpha Centauri and Barnard’s Star. Despite its proximity, Luhman 16AB was only discovered in 2013 by the astronomer Kevin Luhman. The two brown dwarfs that make up the system, Luhman 16A and Luhman 16B, orbit each other at a distance of only three times the distance between the Earth and the Sun, and so these observations are a showcase for Hubble’s precision and high resolution.
The astronomers using Hubble to study Luhman 16AB were not only interested in the waltz of the two brown dwarfs, but were also searching for a third, invisible, dancing partner. Earlier observations with ESO’s Very Large Telescope indicated the presence of an exoplanet in the system. The team wanted to verify this claim by analysing the movement of the brown dwarfs in great detail over a long period of time, but the Hubble data showed that the two dwarfs are indeed dancing alone, unperturbed by a massive planetary companion.
Hubble Space Telescope astrometry of the closest brown dwarf binary system --
I. Overview and improved orbit - L. R. Bedin et al
The Longmore catalogue of planetary nebulae was compiled by the astronomer Andrew Longmore in 1977 who can be seen in this photo with the telescope that was used to take the photographic plates. The galaxy to the left of Iota Centauri at top is NGC 5102, which hosts an ionized outflow. The galaxy to the right of Longmore 8 is NGC 5121 and can be seen more closely in this image by Steve Crouch.
This image shows three different ejecta events. The brightest and most obvious is the Crescent Nebula on the right, which is produced by interstellar material ejected by a Wolf Rayet type star. Much more elusive is the spherical Soap Bubble Nebula hiding near the middle, which is a planetary nebula formed by the outer layers of a small dying star being ejected. Finally, a faint ejecta nebula can be seen around the luminous blue variable (LBV) star P Cygni, the bright star near the left surrounded by a blue OIII cloud. A closer view of P Cygni by Martin Rusterholz can be seen here.
Since 2003 the nebula, located about 5000 light-years from Earth, has held the record for the coldest known object in the Universe. The nebula is thought to have formed from the envelope of a star in its later stages of life which engulfed a smaller, binary companion. It is possible that this is the cause of the ultra-cold outflows, which are illuminated by the light of the central, dying star.
ALMA looked at the nebula’s central dusty disc and the outflows further out, which span a distance of almost four light-years across the sky. These outflows are even colder than the cosmic microwave background, reaching temperatures below –270 °C. The outflows are also expanding at a speed of 590 000 kilometres per hour.
A century ago, Albert Einstein published his famous theory of relativity. He proposed that all objects physically warp the fabric of space, with larger masses producing a more pronounced effect, and very massive objects (such as the Sun) causing light to travel along curved paths through space. Such an effect was first observed during the 1919 solar eclipse by English astronomer Arthur Eddington.
Researchers had to wait a century, however, to get a telescope powerful enough to detect this gravitational microlensing caused by a star outside the Solar System. Even around objects with very large masses, such as stars, this effect is very slight, making such detections extremely challenging for ground-based telescopes. It is, however, within the capabilities of the NASA/ESA Hubble Space Telescope, which gathered the data comprising this Picture of the Week.
The bright star in the centre of the image is the nearby white dwarfStein 2051B, only 17 light-years from Earth. The smaller star below is about 5000 light-years away. Astronomers observed Stein 2051B eight times within two years while the white dwarf travelled in front of of the distant background star. During the close alignment, the white dwarf’s gravity bent the light from the distant star, making it appear offset by about 2 milliarcseconds from its actual position. This deviation is so small that it is equivalent to observing an ant crawl across the surface of a 1€ coin from 2300 kilometres away.
The observed system, Luhman 16AB, is only about six light-years away and is the third closest stellar system to Earth — after the triple star system Alpha Centauri and Barnard’s Star. Despite its proximity, Luhman 16AB was only discovered in 2013 by the astronomer Kevin Luhman. The two brown dwarfs that make up the system, Luhman 16A and Luhman 16B, orbit each other at a distance of only three times the distance between the Earth and the Sun, and so these observations are a showcase for Hubble’s precision and high resolution.
<<A study by Gillon et al. (2013) found that Luhman 16B exhibited uneven surface illumination during its rotation. On 5 May 2013, Crossfield et al. (2014) used the European Southern Observatory's Very Large Telescope (VLT) to directly observe the Luhman 16 system for five hours, the equivalent of a full rotation of Luhman 16B. Their research confirmed Gillon et al.'s observation, finding a large, dark region at the middle latitudes, a bright area near its upper pole, and mottled illumination elsewhere. They suggest this variant illumination indicates "patchy global clouds", where darker areas represent thick clouds and brighter areas are holes in the cloud layer permitting light from the interior. Gillon et al. determined that Luhman 16B's illumination patterns change rapidly, on a day-to-day basis. Although Luhman 16A has also been observed in the same fashion as 16B, no similar variance in illumination was found.>>