{"id":26381,"date":"2021-11-11T13:29:04","date_gmt":"2021-11-11T13:29:04","guid":{"rendered":"https:\/\/www.skyatnightmagazine.com\/?p=101890"},"modified":"2021-11-11T13:43:14","modified_gmt":"2021-11-11T13:43:14","slug":"how-to-observe-and-photograph-lunar-ray-ejecta-systems","status":"publish","type":"rss_feed","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/rss_feed\/how-to-observe-and-photograph-lunar-ray-ejecta-systems\/","title":{"rendered":"How to observe and photograph lunar ray ejecta systems"},"content":{"rendered":"

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By Will Gater\n \t\t<\/p>

Published: Thursday, 11 November 2021 at 12:00 am<\/p>

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T<\/span>he face of the Moon records hundreds of millions of years\u2019 worth of asteroid and comet impacts. Its disc is peppered with countless craters and large basins, where immense collisions punched deep into the lunar crust.<\/p>\n

But scattered across the Moon\u2019s pockmarked highlands and the smooth basalt lunar seas<\/a>, emanating from some craters are also striking, bright features.<\/p>\n

They are cosmic splashes of rock and dust that give a hint of the dynamic and tumultuous past of our nearest neighbour.<\/p>\n

Astronomers call these surface features \u2018ray ejecta\u2019: the material thrown out from the impacts that made their parent craters.<\/p>\n

For more on getting the best out of our lunar companion, read our guides on how to observe the Moon<\/a> and how to photograph the Moon<\/a>.<\/strong><\/em><\/p>\n

\u00a0<\/p>\n

\""Crater\"<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>
Crater Tycho, as seen by the Hubble Space Telescope. Credit: NASA, ESA, and D. Ehrenreich (Institut de Plan\u00e9tologie et d\u2019Astrophysique de Grenoble (IPAG)\/CNRS\/Universit\u00e9 Joseph Fourier)<\/span><\/figcaption><\/div>\n

These dazzling ray systems are generally associated with younger craters. Tycho, for example, is thought to have formed around 109 million years ago.<\/p>\n

The bright streaks are in essence \u2018fresher\u2019 material that hasn\u2019t experienced the same level of space weathering as its surroundings (a process that typically darkens the surfaces of Solar System bodies).<\/p>\n

The impact events that created these ray systems must have been breathtaking.<\/span><\/p>\n

Though we can\u2019t see <\/span>those cataclysms today, viewing some of the ejecta they left behind through a telescope or a good pair of binoculars can still give one an appreciation of the immense energy involved.<\/p>\n

\""New\"<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>
Ray ejecta systems can be seen clearly during a full Moon. Credit: Sarah & Simon Fisher, Bromsgrove, Worcestershire, UK.<\/span><\/figcaption><\/div>\n

How to observe Moon ejecta systems<\/strong><\/h2>\n

Ray ejecta on the Moon come to prominence at a time during the cycle of lunar phases<\/a> when other targets are poorly illuminated for observation or imaging.<\/p>\n

Craters, mountains and rilles appear most spectacular when they\u2019re obliquely lit: something that accentuates surface textures and differing heights with deep shadows.<\/p>\n

Ray systems, though, appear at their most impressive when the Sun is high over their location on the lunar surface.<\/p>\n

In fact, most ray systems become almost invisible when their parent craters are lit from a shallow angle.<\/p>\n

\""Crater\"<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>
Crater Copernicus + Montes-Carpatus by Marc Delaney, Barry, Wales, UK. Equipment: Meade-LS-ACF-6\u2033, ZWO-178MC<\/span><\/figcaption><\/div>\n

This means that full Moon<\/a> and the late gibbous Moon<\/a> phases, when features on the far eastern or far western side of the lunar disc are lit from above, are the best times to see these enigmatic ray ejecta.<\/p>\n

Some ray ejecta systems, like the sprawling mass that surrounds the crater Copernicus, can just be made out with the naked eye on a clear night. A good pair of binoculars is also a wonderful way to explore them.<\/p>\n

At full Moon, when the air is still, the view of Tycho\u2019s extraordinary rays in 10\u00d750 binoculars gives a real sense of the huge streaks of ejecta material wrapping \u2018around\u2019 the three-dimensional hemisphere of the Moon\u2019s nearside.<\/p>\n

Indeed, their ease of viewing is something that makes the ray systems unlike many of the smaller features on the lunar disc.<\/p>\n