 Gravitational lensing of objects on or near critical-costed curves can actually identify individual stars in a lensed galaxy. This is referred to as micro-lensing. To illustrate this ability, we'll cover two examples, Icarus and Arendelle. Here's Max J1149, a foreground galaxy cluster 5 billion light-years away. We used this lens when we covered the Rivstal, supernova. Here we lensed the single star nicknamed Icarus in a galaxy 9 billion light-years away. In 2018, this star was astride a critical curve. It was magnified around 2,000 times its actual size. At that time, it was the furthest individual star ever seen. The colors of the light coming from this object showed that it was a blue super-giant star. This type of star is much larger, more massive, hotter, and possibly hundreds of thousands of times intrinsically brighter than our sun. By 2022, the star had moved off the critical curve and is no longer visible. Here we have a massive galaxy cluster. It has been studied for over five years since Hubble first captured the image in 2016. The galaxy was 4.5 billion light-years away from us when the light we see started its journey. The light traveled 5.6 billion light-years to get here, and it's currently 7 billion light-years away. In this cluster, Hubble discovered a gravitationally lensed galaxy nicknamed the Sunrise Arc. Its redshift is 6.2, with an angular size on the sky exceeding 15 arc seconds. At that distance, this makes it 410,000 light-years long. The galaxy was only 3.9 billion light-years away from the Milky Way when the light we see started its journey. The light traveled 12.9 billion light-years to get here, and it is currently 28 billion light-years away, receding faster than the speed of light and beyond the visible horizon. No light leaving that galaxy now will ever reach the Milky Way. In this galaxy, Hubble discovered a single star. The star, LSZ-6, is nicknamed Arundel. The light we see from this star began its journey 900 million years into the universe's expansion. This makes it the oldest most distant individual star ever seen. In addition, it is at least 50 times the mass of our sun, and hundreds of thousands of times brighter. This makes it one of the most massive stars known. Stars that massive only last for a few million years, so Arundel is long gone, having spewed the heavier elements it created into ZD-1 to become part of the next generation stars. On July 30, 2022, a few months after Hubble's discovery, a team of astronomers called Cosmic Spring worked with Webb to train its near-infrared imaging camera on the sunrise arc for over four hours as part of a survey of the galaxy cluster. It also managed to capture the red dot corresponding to Arundel. Webb's analysis of the image has already confirmed that this is indeed a single star system and not a group of several stars. The red dots on either side of Arundel are a single mirrored star cluster. Here's a higher resolution image of the area around Arundel produced by the James Webb team. Objects close to a critical curve get mirrored into multiple images, like these two images of a star cluster inside the sunrise arc galaxy. The critical curve responsible for this will pass through the midpoint of the two images. An object found at this midpoint, like Arundel, would be so close to the critical curve that its multiple images cannot be resolved. It will appear as a single object. Four different models were used to locate the lensing critical curves. Here's one of them. The others are quite different, but they all pass through Arundel. The magnification drops off rapidly as the distance from the line increases. Arundel's distance from the line is within 0.1 arc seconds. That's a very small angle, but at these distances, it represents 2,730 light-years. This distance, along with its shape, puts its magnification between 1 and 40,000, with 9,000 being the most likely. With this, and the size of the image, we get a source object that has a radius less than 617 billion kilometers. That's 393 billion miles. This is a hundred times smaller than known small star clusters, leading to the conclusion that it is a single gigantic star, or binary star system. Now that we can examine stars this far away with gravitational lensing in the James Webb Space Telescope, I'm hoping that we will even get to the point where light fluctuations from a star like Arundel will someday tell us something about the earliest planets.