The April of 1990 marked the date when NASA launched the Hubble Telescope into space. This was a truly momentous occasion for many reasons, one of which being it was the first optical telescope to be used in space. We no longer had to deal with pesky things to get in the way of observing objects, such as the weather, light pollution, and the atmosphere itself diffracting light. To showcase how powerful the telescope (and by extension, the advantages of having a telescope in space) was, NASA pointed it towards a generally dark region of sky, within the constellation Fornax. From, it was pointed at the same region over 800 times, over a period of time between September 24, 2003, to January 16, 2004, with an equivalent exposure time of over 11 days. The resulting images, compiled over the many observations, was this:
A whole array of galaxies, from a region of sky only about 11.5 square arcminutes (Hyperphysics), which is about 1/10 the diameter of the Full Moon, as viewed from Earth. To give a comparison, it would be like trying to look through an 8-foot straw (NASA)! In this tiny, dark region of sky (less than one in ten millionth the size of the total sky), scientists were able to estimate that were about 10,000 galaxies in total. These galaxies ranged in size, shape, and age, some being only a few hundred million years older than the Big Bang. They were partially able to do this by observing the red shift of certain galaxies. We know that the universe is expanding around us, and that the rate of expansion increases the further away an object is from us. Due to the universe expanding like this, light on its way to Earth gets its wavelength contracted, or "redshifted," due to the Doppler Effect. Depending on how much redshifted an object is, we can calculate how fast it is moving away from us, and thus its distance from us. This means that the redder galaxies are more ancient, and the more red they are, the closer they are in age to the big bang. Many galaxies are so red in fact, that they are actually infrared. This means that the image above is actually not accurate to the color. The redder galaxies are actually galaxies emitting infrared light, and the more green/blue galaxies are galaxies in the visible spectrum. In a sense, this means that not only is this image a snapshot of galaxies near and far, but also a glimpse back in time.
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| Hubble Ultra Deep Field (Credit: ESA, S. Beckwith (STScI) and the HUDF Team) |
These older galaxies are also evidence of a younger, more chaotic universe. Many of the older galaxies look more reminiscent of large bright blobs than the familiar galaxies we know of now. Scientists are using these to see what the earliest galaxies and star formations may be like, which can give a better glimpse into the early universe. Speaking of early glimpses, astronomers have been taking more precise images. They have also been observing more regions in ultraviolet light, which are mainly produced in younger, hotter stars. Another such image that was taken was the eXtreme Deep Field (XDF). The XDF was taken in the center of the original location the Ultra Deep Field, with much more detail. With it, we got an even deeper look into the universe, and found 5,500 galaxies within a much smaller region.
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| eXtreme Deep Field (Credit: NASA; ESA; G. Illingworth, D. Magee, and P. Oesch, University of California, Santa Cruz; R. Bouwens, Leiden University; and the HUDF09 Team) |
I think the most interesting thing about these images is just how a discovery like this was under our nose (or above it). It's hard to encapsulate the size of the galaxy that we live in, let alone the fact that it's one of possibly billions. To me, this image alone really showcases how huge and ancient our universe truly is, and just how small we are in comparison. Although the previous statement may sound existential, it is also just a great image to look at, and makes for a wicked poster.
References:
https://esahubble.org/news/heic0406/
http://hyperphysics.phy-astr.gsu.edu/hbase/Astro/deepfield.html#c1
https://www.nasa.gov/mission_pages/hubble/science/xdf.html
https://www.nasa.gov/mission_pages/hubble/story/index.html
https://svs.gsfc.nasa.gov/30946
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