JWST Shoots SMACS and gets Smacked!

I’m sure you have at least heard about the James Webb Space Telescope’s (JWST) incredible initial images.

At first, I was a little underwhelmed. The images just didn’t move me the way Hubble’s Ultra Deep Field did. Then I found out JWST’s image of SMACS 0723 only took 12.5 hours total. Hubble’s Ultra-Deep Field image took 277.8 hours, scheduled over several months. Due to Hubble’s close orbit of Earth, it was limited by Earth getting in the way and other issues, forcing multiple imaging sessions. JWST is a million miles from Earth, so it doesn’t have these limitations.

This is not a put down of Hubble. At just under 100”, Hubble is less than half the size of JWST’s 256-inch mirror array. And the other advantage JWST has is its design as an infrared telescope. Hubble just cannot compete with JWST at infrared wavelengths.

The first JWST deep field image I saw was of SMACS 0723, a massive galaxy cluster in the southern sky constellation Volans, the flying fish. This is the 12.5-hour exposure that shows a similar (but different) sight as Hubble’s Ultra Deep Field. It’s full of galaxies, from an area of sky equivalent to a grain of sand held at arm’s length. Because it was taken with NIRC and MIRC (near infrared and mid-infrared cameras), many galaxies unseen by Hubble are on display. And as I mentioned, SMACS 0723 is a massive galaxy cluster so the other intriguing thing about this image is how distorted many galaxies appear. It’s an example of gravitational lensing. Strong gravitational fields can re-direct photons from their path, causing interesting effects like in the JWST image. A strong gravitational field’s effects include magnifying the view of objects directly behind them, like a magnifying glass. That helps astronomers see galaxies even farther away.

While gravitational lensing isn’t something new, JWST’s sensitive eye gives astronomers a more detailed look at what’s going on. Maybe JWST will help astronomers map unseen dark matter.

With a mirror more that twice the size of Hubble, JWST will also have better resolution, meaning the ability to see details that would be blurry in Hubble images. But don’t worry, Hubble still has plenty of research power within its wheelhouse.

Then it happened.

JWST got smacked. In late May, one of JWST’s hexagonal mirror sections was hit by a micrometeoroid, one larger than engineers had expected. The damage is done but science goes on. The mirror section was adjusted and the effect on image data collection appears minimal. Micrometeoroids are a hazard of doing stuff in space and are considered when designing and planning a mission. This was called an exception, but engineers are revisiting the subject, to hopefully minimize exposure of JWST’s mirror array.

What’s in the Sky?

It’s still a pre-dawn riser festival in the sky. Venus, Mars, Jupiter, and Saturn are stretched out from east to southwest. Put the coffee on and enjoy.