Pointed Perfection

Did you notice anything other than their appearance in these images taken by the James Webb Space Telescope? absolutely incrediblewell?

If these photos look somehow different from other deep space photos, you’re not wrong. Like any good movie director, James Webb knows how to make his stars look great on camera, and he does it with his signature visual brand: extra diffraction spikes.

Check this out to see what we’re talking about side by side comparison of iconic images Pillars of CreationOne taken by Webb, the other by the Hubble Space Telescope (which is still going strong, Meanwhile).

In the Webb image, each star is adorned with eight spikes surrounding its center; six are large and two are barely visible. Meanwhile, Hubble only shows four. So what’s the problem?

Go back

These diffraction spikes do not represent what the stars actually look like, but are a visual artifact caused by the internal structure of the telescopes.

Diffraction is a term that describes what happens when light waves pass the edge of an object, causing it to bend. In reflecting telescopes such as Webb and Hubble, where a secondary mirror is suspended in front of the primary mirror – as seen this handy NASA infographic – you tend to get most of it.

Some diffraction is caused by light reflected from the main mirror, which at Webb consists of more than a dozen segments. But its most noticeable effects occur when it hits the secondary, which is held in place by several supports.

When the light is refracted by the buttresses again, some of the waves will overlap in certain areas, either being canceled out or increasing in brightness. Spikes are an example of the latter, and their pattern depends on both the shape of the primary mirror and the arrangement of the struts.

Eight of Hands

Now let’s get to why there are eight spikes specifically. James Webb’s secondary mirror has three struts that produce six smaller spikes.

By design, four of these overlap the six much larger spikes produced by the main mirror’s hexagonal pattern. This leaves only two of the secondary spikes visible; we can actually see eight of them in total.

You tend to see these diffraction spikes only in very bright stars. The light of larger objects that are also bright (such as a bright nebula) is not intense enough to create this effect.

Although they look great, diffraction spikes are not very desirable because they can obscure other objects. For now, scientists will have to live with this. But future telescopes, as planned, Giant Magellanic Telescope In Chile, it cannot have spikes at all due to its advanced configuration that will ensure that no light is blocked by the support poles.

More about space telescopes: James Webb Spotted the First Alien in “Steam World”