{"id":65037,"date":"2024-10-28T09:01:33","date_gmt":"2024-10-28T09:01:33","guid":{"rendered":"http:\/\/78d98345-2ada-454d-a368-9e7af7ed7e08"},"modified":"2024-10-28T09:39:37","modified_gmt":"2024-10-28T09:39:37","slug":"ever-seen-spikes-coming-from-stars-in-images-of-space-this-is-what-causes-them","status":"publish","type":"rss_feed","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/rss_feed\/ever-seen-spikes-coming-from-stars-in-images-of-space-this-is-what-causes-them\/","title":{"rendered":"Ever seen spikes coming from stars in images of space? This is what causes them"},"content":{"rendered":"

What causes the spikes seen around stars in images of space? <\/p>

By <\/p>

Published: Monday, 28 October 2024 at 09:01 AM<\/p>

\n\n

Diffraction spikes is the name given to the pointy spikes seen emanating from stars in images of space.<\/p>

When light from a bright object like a star<\/a> passes across any straight edge, it is bent or \u2018diffracted\u2019 very slightly.<\/p>

This diffraction is manifested in the form of bright spikes extending from the core at 180\u00b0 from one another.<\/p>

That’s what’s happening in the case of spikes around stars in images: it’s to do with how the light<\/a> from a star interacts with the optical structure of a reflecting telescope.<\/p>

The struts of a reflecting telescope are what causes diffraction spikes around stars in images of space. Credit: Peter Horrox \/ iStock \/ Getty Images Plus <\/figcaption> <\/figure>

A typical example is the bright lines produced by the spider vanes that support the secondary mirror in a Newtonian reflector, where each vane produces two spikes.<\/p>

Most secondary mirror supports have four vanes, but you only see four spikes because the second set are coincident with the first.<\/p>

However, a spider vane with only three vanes will clearly show the \u2018missing\u2019 spikes resulting in six spikes being visible.<\/p>

\"NASA
NASA infographic showing how different strut configurations in reflecting telescopes cause different shapes of diffraction spikes around stars. Credit: NASA <\/figcaption> <\/figure>

Wide-field images captured using a camera lens often show multiple diffraction spikes caused by the leaves of the camera\u2019s aperture iris, so a 7-leaf iris will produce 14 spikes.<\/p>

One of the key ways of telling a Hubble Space Telescope image from a James Webb Space Telescope image, for example, is the diffraction spikes.<\/p>

Hubble images show 4 diffraction spikes around stars, while Webb images have 8 diffraction spikes<\/a>.<\/p>

\"A
A typical Webb Telescope star, showing eight diffraction spikes. Credit: NASA, ESA, CSA. Science: Dan Coe (STScI\/AURA for ESA, JHU), Brian Welch (NASA-GSFC, UMD), Image Processing: Zolt G. Levay <\/figcaption> <\/figure>

How to create diffraction spikes in your images<\/strong><\/h2>

Diffraction spikes are created naturally by reflectors that employ spider vanes to hold the secondary mirror in place.<\/p>

However, some imagers like the effect of these spikes even though their telescopes don\u2019t produce them, and there are several ways of adding them to your images.<\/p>

Stretching two lines of fishing trace at right angles to one another across the front of a refractor will create diffraction spikes.<\/p>

Alternatively, a wide range of different diffraction effects can be added to any star image using the ProDigital StarSpikes Pro plugin for Adobe Photoshop, Corel PaintShop, Photo-Paint, ComputerInsel PhotoLine and other image processing software.<\/p>

Email your astronomy queries to Steve at contactus@skyatnightmagazine.com<\/a> and your question could be answered in a future issue of BBC Sky at Night Magazine.<\/strong><\/em><\/p> <\/body><\/html>\n

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