These two mighty galaxies are pulling each other apart. Known as the « Mice » because they have such long tails, each spiral galaxy has likely already passed through the other. 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. via NASA https://ift.tt/2Ybs5w4

Sure, you can see the 2D rectangle of colors, but can you see deeper? Counting color patches in the featured image, you might estimate that the most information that this 2D digital image can hold is about 60 (horizontal) x 50(vertical) x 256 (possible colors) = 768,000 bits. However, the yet-unproven Holographic Principle states that, counter-intuitively, the information in a 2D panel can include all of the information in a 3D room that can be enclosed by the panel. The principle derives from the idea that the Planck length, the length scale where quantum mechanics begins to dominate classical gravity, is one side of an area that can hold only about one bit of information. The limit was first postulated by physicist Gerard ‘t Hooft in 1993. It can arise from generalizations from seemingly distant speculation that the information held by a black hole is determined not by its enclosed volume but by the surface area of its event horizon. The term « holographic » arises from a hologram analogy where three-dimension images are created by projecting light through a flat screen. Beware, some people staring at the featured image may not think it encodes just 768,000 bits — nor even 2563,000 bit permutations — rather they might claim it encodes a three-dimensional teapot. via NASA https://ift.tt/3B9bkAq

Posing as a brilliant evening star, Venus lies near the western horizon in this southern hemisphere, early spring, night skyscape. To create the composite view exposures tracking the sky and fixed for the foreground were taken on September 25 from Cascavel in southern Brazil. In view after sunset, Venus appears immersed in a cone of zodiacal light, sunlight scattered from dust along the Solar System’s ecliptic plane. In fact from either hemisphere of planet Earth, zodiacal light is most visible after sunset near a spring equinox, (or before sunrise near an autumn equinox) when its luminous arc lies at steep angles to the horizon. Extending above the sunset on this night, the zodiacal light reaches toward rich starfields and immense interstellar dust clouds in the bulge of the central Milky Way. Follow along the Milky Way from the central bulge back toward the horizon and you’ll spot the closest star system to the Sun, Alpha Centauri, a mere 4.37 light-years away. via NASA https://ift.tt/3orHLqi

Dark markings and colorful clouds inhabit this stellar landscape. The deep and expansive view spans more than 30 full moons across crowded star fields toward the center of our Milky Way Galaxy. Cataloged in the early 20th century by astronomer E. E. Barnard, the obscuring interstellar dust clouds seen toward the right include B59, B72, B77 and B78, part of the Ophiuchus molecular cloud complex a mere 450 light-years away. To the eye their combined shape suggests a pipe stem and bowl, and so the dark nebula’s popular name is the Pipe Nebula. Three bright nebulae gathered on the left are stellar nurseries some 5,000 light-years distant toward the constellation Sagittarius. In the 18th century astronomer Charles Messier included two of them in his catalog of bright clusters and nebulae; M8, the largest of the triplet, and colorful M20 just above. The third prominent emission region includes NGC 6559 at the far left. Itself divided by obscuring dust lanes, M20 is also known as the Trifid. M8’s popular moniker is the Lagoon Nebula. via NASA https://ift.tt/3CW3nyO

Gorgeous spiral galaxy M33 seems to have more than its fair share of glowing hydrogen gas. A prominent member of the local group of galaxies, M33 is also known as the Triangulum Galaxy and lies a mere 3 million light-years away. 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 ionizes 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 color 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 center in this portrait of M33. via NASA https://ift.tt/3okq9MP

Have you ever seen a gigantic jet? They are extremely rare but tremendously powerful. Gigantic jets are a type of lightning discharge documented only this century that occur between some thunderstorms and the Earth’s ionosphere high above them. Pictured above is the middle and top of one such jet caught last week by a lightning and meteor camera from Puerto Rico, USA. The jet traversed perhaps 70 kilometers in just under one second. Gigantic jets are much different from regular cloud-to-cloud and cloud-to-ground lightning. The bottoms of gigantic jets appear similar in appearance to another type cloud-to-above strike called blue jets, while the tops appear similar to upper-atmosphere red sprites. Although the mechanism and trigger that causes gigantic jets is a topic of research, it is clear that the jets reduce charge imbalance between different parts of Earth’s atmosphere. A good way to look for gigantic jets is to watch a powerful but distant thunderstorm from a clear location. via NASA https://ift.tt/2ZuWzd1

Have you ever experienced a meteor shower? To help capture the wonder, a video was taken during the peak of the recent Perseid meteor shower above the Indian Astronomical Observatory in Hanle, India, high up in the Himalayan mountains. Night descends as the video begins, with the central plane of our Milky Way Galaxy approaching from the left and Earth-orbiting satellites zipping by overhead. During the night, the flash of meteors that usually takes less than a second is artificially extended. The green glow of most meteors is typically caused by vaporizing nickel. As the video continues, Orion rises and meteors flare above the 2-meter Himalayan Chandra Telescope and the seven barrels of the High Energy Gamma Ray Telescope (Hagar). The 2 minute 30 second movie ends with the Sun rising, preceded by a false dawn of zodiacal light. via NASA https://ift.tt/39IeLSl

Here is one of the most famous pictures from the Moon — but digitally reversed. Apollo 11 landed on the moon in 1969 and soon thereafter many pictures were taken, including an iconic picture of Buzz Aldrin taken by Neil Armstrong. The original image 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, 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. via NASA https://ift.tt/3kIK31E

How did a round star create this square nebula? No one is quite sure. The round star, known as MWC 922 and possibly part of a multiple star system, appears at the center of the Red Square Nebula. The featured image combines infrared exposures from the Hale Telescope on Mt. Palomar in California, and the Keck-2 Telescope on Mauna Kea in Hawaii. A leading progenitor hypothesis for the square nebula is that the central star or stars somehow expelled cones of gas during a late developmental stage. For MWC 922, these cones happen to incorporate nearly right angles and be visible from the sides. Supporting evidence for the cone hypothesis includes radial spokes in the image that might run along the cone walls. Researchers speculate that the cones viewed from another angle would appear similar to the gigantic rings of supernova 1987A, possibly indicating that a star in MWC 922 might one day itself explode in a similar supernova. via NASA https://ift.tt/3zHnAGJ

To the eye, this cosmic composition nicely balances the Bubble Nebula at the right with open star cluster M52. The pair would be lopsided on other scales, though. Embedded in a complex of interstellar dust and gas and blown by the winds from a single, massive O-type star, the Bubble Nebula, also known as NGC 7635, is a mere 10 light-years wide. On the other hand, M52 is a rich open cluster of around a thousand stars. The cluster is about 25 light-years across. Seen toward the northern boundary of Cassiopeia, distance estimates for the Bubble Nebula and associated cloud complex are around 11,000 light-years, while star cluster M52 lies nearly 5,000 light-years away. The wide telescopic field of view spans about 1.5 degrees on the sky or three times the apparent size of a full Moon. via NASA https://ift.tt/3kHb6e2