Sunspots are much cooler than the surrounding solar surface because the magnetic fields that create them reduce convective heating. But you knew that. So why are the regions above them hundreds of times hotter? To wit:
To help find the cause, NASA directed the Earth-orbiting Nuclear Spectroscopic Telescope Array (NuSTAR) satellite to point its very sensitive X-ray telescope at the Sun. Featured here is the Sun in ultraviolet light, shown in a red hue as taken by the orbiting Solar Dynamics Observatory (SDO). Superimposed in false-coloured green and blue is emission above sunspots detected by NuSTAR in different bands of high-energy X-rays, highlighting regions of extremely high temperature. Clues about the Sun’s atmospheric heating mechanisms come from NuSTAR images like this and shed light on solar nanoflares and microflares as brief bursts of energy that may drive the unusual heating.
(Image: NASA, NuSTAR, SDO)
Behold: the Cat’s Eye, aka NGC 6543 – one of brightest and most detailed planetary nebula known – composed of gas expelled in the brief, glorious death throes of a Sun-like star. To wit:
This nebula‘s dying central star may have produced the outer circular concentric shells by shrugging off outer layers in a series of regular convulsions. The formation of the beautiful, complex-yet-symmetric inner structures, however, is not well understood. The featured image is a composite of a digitally sharpened Hubble Space Telescope image with X-ray light captured by the orbiting Chandra Observatory. The exquisite floating space statue spans over half a light-year across. Of course, gazing into this Cat’s Eye, humanity may well be seeing the fate of our sun, destined to enter its own planetary nebula phase of evolution … in about 5 billion years.
(Image: NASA, ESA, Hubble Legacy Archive; Chandra X-ray Obs.; Processing & Copyright: Rudy Pohl)
Behold: the Milky Way and a waterfall. Seems like a simple enough juxtaposition, but not so. To wit:
The dream was to capture both the waterfall and the Milky Way together. Difficulties included finding a good camera location, artificially illuminating the waterfall and the surrounding valley effectively, capturing the entire scene with numerous foreground and background shots, worrying that fireflies would be too distracting, keeping the camera dry, and avoiding stepping on a poisonous snake. […] The waterfall is the picturesque Zhulian waterfall in the Luoxiao Mountains in eastern Hunan Province, China. The central band of our Milky Way Galaxy crosses the sky and shows numerous dark dust filaments and colourful nebulas. Bright stars dot the sky — all residing in the nearby Milky Way — including the Summer Triangle with bright Vega visible above the Milky Way’s arch. After capturing all 78 component exposures for you to enjoy, the photographer and friends enjoyed the view themselves for the rest of the night.
(Image: Xie Jie)
Behold: the vast cosmic bubble of Sharpless 2-308, aka, the Dolphin Head nebula – blown by fast winds from a hot, massive star. To wit:
…it lies some 5,000 light-years away toward the constellation of the Big Dog (Canis Major) and covers slightly more of the sky than a Full Moon. That corresponds to a diameter of 60 light-years at its estimated distance. The massive star that created the bubble, a Wolf-Rayet star, is the bright one near the center of the nebula. Wolf-Rayet stars have over 20 times the mass of the Sun and are thought to be in a brief, pre-supernova phase of massive star evolution. Fast winds from this Wolf-Rayet star create the bubble-shaped nebula as they sweep up slower moving material from an earlier phase of evolution. The windblown nebula has an age of about 70,000 years. Relatively faint emission captured by narrowband filters in the deep image is dominated by the glow of ionised oxygen atoms mapped to a blue hue.
(Image: Nik Szymanek)
Behold: lovely spiral galaxy NGC 289 – about 70 million light-years away and much larger than our own dear Milky Way. To wit:
Seen nearly face-on, its bright core and colourful central disk give way to remarkably faint, bluish spiral arms. The extensive arms sweep well over 100 thousand light-years from the galaxy’s centre. At the lower right in this sharp, telescopic galaxy portrait the main spiral arm seems to encounter a small, fuzzy elliptical companion galaxy interacting with enormous NGC 289. Of course spiky stars are in the foreground of the scene. They lie within the Milky Way toward the southern constellation Sculptor.
(Image: Mike Selby)
Behold: a meteor, but an especially bright one (even brighter in reality than seen here), and therefore entitled to a more vivid descriptor. To wit:
The International Astronomical Union defines a fireball as a meteor brighter than apparent magnitude -4, which corresponds (roughly) to being brighter than any planet — as well as bright enough to cast a human-noticeable shadow. Pictured, an astrophotographer taking a long-duration sky image captured by accident the brightest meteor he had ever seen. Clearly a fireball, the disintegrating space-rock created a trail so bright it turned night into day for about two seconds earlier this month. The fireball has been artificially dimmed in the featured image to bring up foreground Lake Louise in Alberta, Canada. Although fireballs are rare, many people have been lucky enough to see them. If you see a fireball, you can report it. If more than one person recorded an image, the fireball might be traceable back to the Solar System body from which it was ejected.
(Image: Hao Qin)
space jellyfish! dark streams of dust in the Orion Nebula. But what are they and where do they come from? Answer me, damn you! To wit:
This part of the Orion Molecular Cloud Complex, M43, is the often imaged but rarely mentioned neighbour of the more famous M42. M42, seen in part to the upper right, includes many bright stars from the Trapezium star cluster. M43 is itself a star forming region that displays intricately-laced streams of dark dust — although it is really composed mostly of glowing hydrogen gas. The entire Orion field is located about 1600 light years away. Opaque to visible light, the picturesque dark dust is created in the outer atmosphere of massive cool stars and expelled by strong outer winds of protons and electrons.
(Image: Jari Saukkonen)
Behold: NGC 4676 – two mighty galaxies pulling each other apart having passed through each other, leaving long tails behind. That’s why they’re called ‘The Mice’. To wit:
The long tails are created by the relative difference between gravitational pulls on the near and far parts of each galaxy. Because the distances are so large, the cosmic interaction takes place in slow motion — over hundreds of millions of years. NGC 4676 lies about 300 million light-years away toward the constellation of Bernice’s Hair (Coma Berenices) and are likely members of the Coma Cluster of Galaxies. The featured picture was taken with the Hubble Space Telescope‘s Advanced Camera for Surveys in 2002. These galactic mice will probably collide again and again over the next billion years so that, instead of continuing to pull each other apart, they coalesce to form a single galaxy.
(Image: NASA, ESA, Hubble; Processing & Copyright: William Ostling (The Astronomy Enthusiast)
Behold: M33, also known as NGC 598, also known as the Triangulum Galaxy – a mere three million light years away and well supplied with clouds of glowing hydrogen gas. But how to tell one rosy-cheeked rascal from the next? To wit:
Sprawling along loose spiral arms that wind toward the core, M33’s giant HII regions are some of the largest known stellar nurseries, sites of the formation of short-lived but very massive stars. Intense ultraviolet radiation from the luminous massive stars ionises the surrounding hydrogen gas and ultimately produces the characteristic red glow. To highlight the HII regions in this telescopic image, broadband data used to produce a colour view of the galaxy were combined with narrowband data recorded through a hydrogen-alpha filter, transmitting the light of the strongest hydrogen emission line. Close-ups of cataloged HII regions appear in the sidebar insets. Use the individual reference number to find their location within the Triangulum Galaxy. For example, giant HII region NGC604 is identified in an inset on the right and appears at position number 15. That’s about 4 o’clock from galaxy centre in this portrait of M33.
Full sized image here.
(Image: Luca Fornaciari)
Behold: one of the most famous of many pictures taken during the Apollo 11 moon landing in the summer of ’69 – a shot of Buzz Aldrin taken by Neil Armstrong. Also in reverse. To wit:
The original image (top pic) captured not only the magnificent desolation of an unfamiliar world, but Armstrong himself reflected in Aldrin’s curved visor. Enter modern digital technology. In the featured image (pic 2), the spherical distortion from Aldrin’s helmet has been reversed. The result is the famous picture — but now featuring Armstrong himself from Aldrin’s perspective. Even so, since Armstrong took the picture, the image is effectively a five-decade old lunar selfie. The original visor reflection is shown on the left, while Earth hangs in the lunar sky on the upper right. A foil-wrapped leg of the Eagle lander is prominently visible. Preparations to return humans to the Moon in the next few years include the Artemis program, an international collaboration led by NASA.
(Image: NASA, Apollo 11, Neil Armstrong; Processing: Michael Ranger)