JWST Revisited the EXTREME Deep Field. What It Saw Was AMAZING! (MIDIS Deep Field)

This brand new image took JWST nearly a hundred hours to observe. It shows one of the most iconic patches of space in history, the Hubble Ultra Deep Field region. This is the longest observation of a single patch of space that JWST has done so far, and it has revealed so many galaxies that we have never seen before. When Hubble originally imaged this same field, the world was shocked at how much light and how many objects it could see. And to be honest, this new one makes Hubble's look emptier than ever before. In this video, we'll take a deep look at the new image, explore the differences between the JWST and Hubble versions of the image, and even see what's changed since the last time JWST pointed in this direction. JWST has used two of its instruments to revisit one of Hubble's most iconic images, using almost a hundred hours worth of data obtained by continually staring at the same patch of space. This patch covers the majority of a Hubble image called the Extreme Deep Field, or XDF, which itself is within the famous Hubble Ultra Deep Field. Honestly, Hubble's released a whole bunch of different deep fields, and it can be kind of hard to keep track of which one's which. The Ultra Deep Field used 11.3 days worth of data to create, and was released in 2004, while the Extreme Deep Field focused on more or less the same patch of space, but combined even more data, spanning 10 years of Hubble observations, and this was released in 2012. JWST has now revisited the XDF, giving us an incredible comparison between the capabilities of the two telescopes. Both of them see so many objects, mostly galaxies, that I think it's natural to think of this as an enormous patch of space. In reality though, it looks like that because these telescopes take very zoomed in, detailed images, but the XDF covers a patch of sky much, much smaller than the diameter of the full moon. That's why it is so shocking that we see so many galaxies in here. It looks like it's a completely dark patch of space from Earth, but the reality is that it's full of bright, shining galaxies. There are two main differences between the original 2012 Hubble image and the brand new JWST one that we've just got to see. The first is how many more objects we can see. As we swap back and forth between the two images, pick any dark patch in the Hubble image. Chances are, there or very nearby, a galaxy will pop out of the darkness as we go to the JWST image. Hubble saw almost 10,000 objects in its XDF, and JWST sees many, many more, revealing at least two and a half thousand new objects. The other difference is in the brightness of the objects, even the ones that are in both of the images. This is to do with how much light each telescope collects, and that is determined by the size of their primary mirrors. Hubble's is a very respectable 2.4 meters in diameter, but JWST's is an enormous 6.5 meters. So JWST's is about two and a half times larger in diameter, but for light collecting, it's actually the area that's the important number, and JWST's 25 square meter area is about six times larger than Hubble's 4.5 square meter area. So JWST is collecting about six times more light than Hubble at all times. This means that faint objects look a lot brighter a lot quicker when we're using Webb. Every object in both images is brighter and more detailed in the new image, and even the background looks a little less pitch black. It's amazing to see each object in the Hubble image light up even more. More details emerge from the darkness, and galaxies look bigger than ever in the new Webb image. This brightness is really shown by how many objects gain diffraction spikes in the JWST picture. These appear only around the brightest objects in telescope images, and here they're around a whole host of the bigger and brighter galaxies when Webb imaged them. These are just caused by the shape of the telescope mirrors and the struts that hold up secondary mirrors in the telescopes, giving different numbers of spikes in the images of different telescopes. JWST typically gives six large spikes and two smaller spikes, while Hubble usually just gives four spikes of equal size. I say usually because here there are actually one or two bright stars that have eight spikes. This tells us something about how the data was collected over those 10 years that was collected together for this image. The telescope itself must have been rolled into slightly different orientations to take some of the different exposures at different times. This means that when all of that data was stacked together, we end up getting two lots of the four diffraction spikes in the final image here, giving these stars with eight spikes, which we don't normally see in Hubble pictures. The field shown in the new JWST image is now known as the MIRI Deep Imaging Survey region, or the MIDIS region, or MIDIS region? I'm not sure, I've never said that out loud. It's effectively the same as the extreme deep field from Hubble, but just a tiny bit smaller. It's named for MIRI, the mid-infrared instrument on JWST, which was used to observe the fields with the three shortest wavelengths of mid-infrared light that MIRI can detect, and it did that for nearly 100 hours in total. This includes Webb's longest observation in one wavelength so far, making this one of the deepest views of the universe ever obtained. This MIRI data was then combined with near-infrared data from NIRCAM, the near-infrared camera, that was obtained at the same time to give us a new image that allows us to explore how galaxies formed and evolved over billions of years. We're looking back in time in all of these pictures. Among the thousands of sources of light here, there are hundreds of extremely red galaxies, some of which are likely to be massive, dust-obscured systems, or even some evolved galaxies, with mature stars that formed early in the universe's history. Thanks to Webb's pretty incredible resolution, even at mid-infrared wavelengths, researchers can resolve structures in many of these galaxies and study how their light is distributed across those galaxies, teaching us about their growth and evolution through time. The fact that this image is made with infrared light lets us also touch on two important things here. The first is that the colours in the Webb image are not exactly real. We can't see infrared light with our own eyes, so there's no way to show this as a true colour image that we can actually see. Instead, the infrared wavelengths of light are mapped to visible colours, so that we can see them. Here, the colours have been chosen to be as real as possible, for example mapping the longest wavelengths to oranges and reds, but also chosen to highlight some important details of the image too. The reddest galaxies tend to be the oldest and most distant, and they often feature a lot of star formation, active galactic nuclei, and high concentrations of dust. Other galaxies, such as the green galaxies, are also very distant with a very high redshift, while the whiter and bluer galaxies tend to be younger and closer to us. The other interesting feature that results from the wavelengths being used here is the resolution of the image. It might be kind of surprising that the resolution of the JWST image isn't much better, if any better, than Hubble's image. That's because image resolution depends on mainly two things for telescopes. The size of the mirror is the first, so the bigger the mirror, the better the resolution, giving JWST a clear advantage here. However, the other thing is the wavelength of light you're observing. Hubble's image is a visible light image, and visible light is shorter wavelength than infrared light. The thing is, the longer the wavelength, the worse the resolution you get is naturally. So in this area, JWST is at a disadvantage. When these two things are combined, the images actually tend to come out at about the same resolution, although JWST does still show off brighter objects with more details visible, thanks to that huge light collecting area. Be sure to take a closer look at all of these images yourself if you fancy it. There are so many cool looking galaxies to find, and let me know if you spot something that's particularly interesting or surprising looking down in the comments. YouTube is now really pushing likes and comments on video, so leaving anything below is super helpful to me. You can tell me about your favorite thing in the image, ask any questions you still have, tell me whether you're excited to revisit the deep fields, or just that you heard that I adopted a cat recently and you'd like to see him. All comments help out just the same, so thanks in advance if you leave one for me. Until next time, stay safe team. I'll see you soon. Bye!