Month: March 2022

Exploring the Antennae

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Some 60 million light-years away in the southerly constellation Corvus, two large galaxies are colliding. Stars in the two galaxies, cataloged as NGC 4038 and NGC 4039, very rarely collide in the course of the ponderous cataclysm that lasts for hundreds of millions of years. But the galaxies’ large clouds of molecular gas and dust often do, triggering furious episodes of star formation near the center of the cosmic wreckage. Spanning over 500 thousand light-years, this stunning view also reveals new star clusters and matter flung far from the scene of the accident by gravitational tidal forces. The remarkably sharp ground-based image, an accumulation of 88 hours of exposure captured during 2012-2021, follows the faint tidal tails and distant background galaxies in the field of view. The suggestive overall visual appearance of the extended arcing structures gives the galaxy pair, also known as Arp 244, its popular name – The Antennae. via NASA https://ift.tt/QUdrJ1a

Animation: Odd Radio Circles

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What do you call a cosmic puzzle that no one expected to see? In this case, Odd Radio Circles, aka ORCs. ORC-1 typifies the enigmatic five objects, only visible at radio frequencies, that were serendipitously discovered in 2019 using the new Australian SKA Pathfinder radio array. The final image in the featured video uses 2021 data from the South African MeerKAT array to reveal more detail. The radio data, assigned turquoise colors, are combined with a Dark Energy Survey optical/IR map. The animated artist’s illustration explores just one idea about the ORCs’ origins. If two supermassive black holes merge in the center of a galaxy, the associated shockwaves could generate rings of radio radiation. These grow to fill the video frame. The video zooms out so the expansion the ORC can be tracked until it is about a million light-years across. Fortunately, the up-coming Square Kilometer Array can help test this and other promising scenarios. via NASA https://ift.tt/h1R8Atk

Venus and Mars: Passing in the Night

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When two planets pass on the night sky, they can usually be seen near each other for a week or more. In the case of this planetary conjunction, Venus and Mars passed within 4 degrees of each other earlier this month. The featured image was taken a few days prior, when Venus was slowing rising in the pre-dawn sky, night by night, while Mars was slowly setting. The image, a four-part mosaic, was captured in Brazil from the small town Teresópolis. Besides Venus and Mars, the morning sky now also includes the more distant planet Saturn. Of course, these conjunctions are only angular — Venus, Mars, and Saturn continue to orbit the Sun in very different parts of our Solar System. Next week, the angle between Saturn and Mars will drop to below a quarter of a degree. via NASA https://ift.tt/1sC0AOr

Gems of a Maldivean Night

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The southernmost part of the Milky Way contains not only the stars of the Southern Cross, but the closest star system to our Sun — Alpha Centauri. The Southern Cross itself is topped by the bright, yellowish star Gamma Crucis. A line from Gamma Crucis through the blue star at the bottom of the cross, Acrux, points toward the south celestial pole, located just above the small island in the featured picture — taken in early March. That island is Madivaru of the Maldives in the Indian Ocean. Against faint Milky Way starlight, the dark Coal Sack Nebula lies just left of the cross, while farther left along the Milky Way are the bright stars Alpha Centauri (left) and Beta Centauri (Hadar). Alpha Centauri A, a Sun-like star anchoring a three-star system with exoplanets, is a mere 4.3 light-years distant. Seen from Alpha Centauri, our own Sun would be a bright yellowish star in the otherwise recognizable constellation Cassiopeia. via NASA https://ift.tt/n0BFCMX

Titan Seas Reflect Sunlight

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Why would the surface of Titan light up with a blinding flash? The reason: a sunglint from liquid seas. Saturn’s moon Titan has numerous smooth lakes of methane that, when the angle is right, reflect sunlight as if they were mirrors. Pictured here in false-color, the robotic Cassini spacecraft that orbited Saturn from 2004 to 2017 imaged the cloud-covered Titan in 2014 in different bands of cloud-piercing infrared light. This specular reflection was so bright it saturated one of Cassini’s infrared cameras. Although the sunglint was annoying — it was also useful. The reflecting regions confirm that northern Titan houses a wide and complex array of seas with a geometry that indicates periods of significant evaporation. During its numerous passes of our Solar System’s most mysterious moon, Cassini has revealed Titan to be a world with active weather — including times when it rains a liquefied version of natural gas. via NASA https://ift.tt/SaREW8b