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How far can you see? Everything you can see, and everything you could possibly see, right now, assuming your eyes could detect all types of radiations around you — is the observable universe. In light, the farthest we can see comes from the cosmic microwave background, a time 13.8 billion years ago when the universe was opaque like thick fog. Some neutrinos and gravitational waves that surround us come from even farther out, but humanity does not yet have the technology to detect them. The featured image illustrates the observable universe on an increasingly compact scale, with the Earth and Sun at the center surrounded by our Solar System, nearby stars, nearby galaxies, distant galaxies, filaments of early matter, and the cosmic microwave background. Cosmologists typically assume that our observable universe is just the nearby part of a greater entity known as „the universe“ where the same physics applies. However, there are several lines of popular but speculative reasoning that assert that even our universe is part of a greater multiverse where either different physical constants occur, different physical laws apply, higher dimensions operate, or slightly different-by-chance versions of our standard universe exist. via NASA https://ift.tt/2ypYohd

In this image from August 2021, NASA astronaut Mark Vande Hei sits and reads while on the International Space Station. via NASA https://ift.tt/BmPCMJw

Pictured — a very scenic road to the stars. The road approaches La Silla Observatory in Chile, with the ESO’s 3.6-meter telescope just up ahead. To the left are some futuristic-looking support structures for the planned BlackGEM telescopes, an array of optical telescopes that will help locate optical counterparts to gravitational waves detections by LIGO and other detectors. But there is much more. Red airglow illuminates the night sky on the right, while the central band of our Milky Way Galaxy slants across the image center. Jupiter can be seen just above the band near the image center, while Saturn is visible just above the 3.6-meter telescope dome. The two largest satellite galaxies of our Milky Way Galaxy, the LMC and SMC, are seen on the far right. The featured image panorama was built up from multiple 15-second exposures that were captured on 2019 June 30. Two days later, La Silla experienced a rare total eclipse of the Sun. via NASA https://ift.tt/PKCks3u

Today is Pi Day! via NASA https://ift.tt/EiQGU35

Where do stars form? One place, star forming regions known as „EGGs“, are being uncovered at the end of this giant pillar of gas and dust in the Eagle Nebula (M16). Short for evaporating gaseous globules, EGGs are dense regions of mostly molecular hydrogen gas that fragment and gravitationally collapse to form stars. Light from the hottest and brightest of these new stars heats the end of the pillar and causes further evaporation of gas and dust — revealing yet more EGGs and more young stars. This featured picture was created from exposures spanning over 30 hours with the Earth-orbiting Hubble Space Telescope in 2014, and digitally processed with modern software by experienced volunteers in Argentina. Newborn stars will gradually destroy their birth pillars over the next 100,000 years or so — if a supernova doesn’t destroy them first. via NASA https://ift.tt/5WDKAzu

Why would the sky glow like a giant repeating rainbow? Airglow. Now air glows all of the time, but it is usually hard to see. A disturbance however — like an approaching storm — may cause noticeable rippling in the Earth’s atmosphere. These gravity waves are oscillations in air analogous to those created when a rock is thrown in calm water. Red airglow likely originates from OH molecules about 87-kilometers high, excited by ultraviolet light from the Sun, while orange and green airglow is likely caused by sodium and oxygen atoms slightly higher up. While driving near Keluke Lake in Qinghai Provence in China a few years ago, the photographer originally noticed mainly the impressive central band of the Milky Way Galaxy. Stopping to photograph it, surprisingly, the resulting sensitive camera image showed airglow bands to be quite prominent and span the entire sky. The featured image has been digitally enhanced to make the colors more vibrant. via NASA https://ift.tt/LgRqhXu

Northern winter constellations and a long arc of the Milky Way are setting in this night skyscape looking toward the Pacific Ocean from Point Reyes on planet Earth’s California coast. Sirius, alpha star of Canis Major, is prominent below the starry arc toward the left. Orion’s yellowish Betelgeuse, Aldebaran in Taurus, and the blue tinted Pleiades star cluster also find themselves between Milky Way and northwestern horizon near the center of the scene. The nebulae visible in the series of exposures used to construct this panoramic view were captured in early March, but are just too faint to be seen with the unaided eye. On that northern night their expansive glow includes the reddish semi-circle of Barnard’s Loop in Orion and NGC 1499 above and right of the Pleiades, also known as the California Nebula. via NASA https://ift.tt/iZe5cyX

An energetic outburst from an infant star streaks across this image from the NASA/ESA Hubble Space Telescope. via NASA https://ift.tt/qTpQP46

Want to see a rainbow smile? Look near the zenith (straight up) when the sun is low in the sky and you might. This example of an ice halo known as a circumzenithal arc was captured above a palm tree top from Ragusa, Sicily on February 24. The vividly colorful arcs are often called smiling rainbows because of their upside down curvature and colors. For circumzenithal arcs the zenith is at the center and red is on the outside, compared to rainbows whose arcs bend toward the horizon after a downpour. True rainbows are formed by water droplets refracting the sunlight to produce a spectrum of colors, though. Circumzenithal arcs are the product of refraction and reflection in flat hexagonal ice crystals, like the ice crystals that create sundogs, formed in high thin clouds. via NASA https://ift.tt/ubIESMO