Thread by @Kevin_Hainline

On Tuesday morning, NASA will release the first full color images from JWST. It's making me very emotional, tbh. Below are the targets of these images, shown from the ground, or from Hubble, or in an artist's rendition. Let's talk about these targets a little bit in advance!

The first target is the Carina Nebula, an incredible assemblage of gas and young stars 8,500 light years away. This is a site of active star formation, and includes Eta Carinae, one of the most massive stars we know of in our galaxy, 100 - 150 times more massive than the Sun.

We currently don't know where JWST was pointing within the nebula. Hubble looked at an area near the center they called the Mystic Mountains in the optical (left) and in the infrared (right). I show the infrared because that's more in line with what JWST will be seeing.

Infrared light can be used to see through the dust to the huge numbers of young stars throughout the nebula. However, longer-wavelength JWST MIRI images could be used to actually look at particular properties of the dust. There's a lot to be learned!

(and hey, dust can be pretty opinionated, too. Here's another possible target, a "Bok globule" of dense dust also in the Carina Nebula.)

The next confirmed target is the Southern Ring Nebula, 2000 light-years distant and shown in the Hubble image below. What you're seeing is the very late state of a sun-like star after it has died, leaving a white dwarf star near the center (though *not* the obvious bright one).

The big envelope of gas is the outer layers of the star that have puffed off of the naked core, the white dwarf, a star made of almost pure carbon the size of the Earth. We call these objects "planetary nebulae."

JWST will see this object in the infrared, so it will look somewhat different. Here's an infrared image of *another* planetary nebula, the Helix nebula, showing complex and delicate layers of dust surrounding the white dwarf.

Next, moving a little farther afield, we have Stephan's Quintet, a group of five very interesting galaxies. Four of the galaxies are doing a delicate merging dance, while the fifth, the blue one in the top left corner, is much closer to Earth and is just a chance superposition.

JWST's infrared images will probably look quite different from that Hubble image. Here's an image that combines multiple visible and infrared images of Stephan's quintet, and pay attention to how the galaxies look. You're seeing through dust to populations of older stars.

So when you're looking at the images on Tuesday, don't just look to see better resolution, or more detail, look to see how having an eye into the universe in the near- and mid-infrared enables us to see *different aspects* of these complex astronomical objects.

Next we have the target that was the most shocking to me (and many other extragalactic astronomers), which is the deep field SMACS 0723. This is a field of many thousands of galaxies that was part of a survey called RELICS that looked for gravitationally-lensed galaxies.

Notice in the image how many galaxies look like weird stringy arcs. These are very distant galaxies where the light they give off has been magnified and stretched by the gravity of the giant hazy galaxy in the middle of the image.

So these lensing galaxies can allow us to see *VERY* distant objects, which is why they were targeted with RELICS. I expect the JWST image will have tons and tons of very pretty galaxies, more even than the Hubble image above. I wonder how far away they'll be!

And finally, the last target is an extrasolar planet, but here they're highlighting the fact that JWST can be used to understand the properties of objects as a function of wavelength. Here, they're releasing a spectrum of WASP 96-b, presumably of it's atmosphere.

Research lead by Nikolay Nikolov showed that this Saturn- to Jupiter-sized planet had an atmosphere that was seemingly free of clouds, so it's a perfect target to see if there are more complicated elements in its atmosphere.

Here, McGruder et al. confirmed the clear atmosphere for this planet, and showed a spectrum of its atmosphere out to 1.8 microns. JWST has the ability to go out much farther than this with its spectrograph, to understand the complicated chemistry of this planet's atmosphere.

The take-home message is that you should be excited for Tuesday. This week is the culmination of years and years of effort by thousands of people. I can't wait to see these images and all of the science that JWST will do over the coming decades.

Astronomy is literally on the precipice of a major change. I am so excited about the answers we are about to get to major scientific questions. But I'm even more excited about the new questions that we're going to ask because of these data.