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Kaushiki Mittal, Astronomy and Space Science
Have you ever wondered how the cold, dark void of space is transformed into stunning images that leave us in awe? By combining science, imagination, and technology, the Hubble Telescope does more than just observe the universe- it shows its beauty. How exactly does this happen? Let’s find out!
Seeing the Universe in shades of Gray
Human eyes only see a small fraction of the electromagnetic spectrum that slots between infrared light and ultraviolet light, from about 380 to 700 nanometers. So, most raw images produced by Hubble look black and white to us. Unlike your camera or smartphone, the Hubble sees everything in monochrome, i.e, black and white. It has the ability to capture light beyond the range of the visible spectrum using specialized filters. Each monochrome layer reveals specific features, such as the temperature, structure, and composition of stars and galaxies. These images serve as the raw data for Hubble’s colourful creations.
Colouring Beyond Vision
The journey from grayscale to vibrant color involves both wide-band and narrow-band imaging techniques. Wide-band imaging captures a broad range of wavelengths, revealing large-scale structures of celestial objects, such as galaxies and nebulae. Narrow-band imaging, on the other hand, isolates specific wavelengths associated with elements like hydrogen, oxygen, or sulfur. These techniques allow scientists to study the physical and chemical processes at work in these cosmic phenomena.
Colourizing of Hubble’s images involves assigning visible colours to represent various wavelengths of light. For example, ultraviolet light, which is invisible to the naked eye, might be represented as blue, while infrared light might be shown as red. This colorization process isn't arbitrary; it serves scientific and artistic purposes.
For example, the iconic Pillars of Creation image captured within the Eagle Nebula, reveals clouds of gas and dust in vivid detail, helping researchers study star formation while captivating the public. The artistic choices, guided by scientific data, make Hubble's images resonate emotionally, turning scientific data into universal art.
Images are also processed to remove imperfections and effects that don't come from the objects being observed by Hubble. These undesired features could be the result of aging sensors causing "dead pixels" in images or the dynamic environment of space. For instance, Hubble images can be streaked by lines of bright light caused by passing asteroids, satellites or even flashing cosmic rays. The Hubble team often removes such distractions before releasing an image to the public.
How has this helped us?
Hubble's ability to study such stretched light from early stars has allowed scientists to better constrain the age of the universe, to around 13.8 billion years. The capability to see early galaxies and stars has also massively increased our understanding of how the universe has evolved since its early epochs.The earliest and most distant object Hubble has been able to image thus far is the highly redshifted galaxy GN-z11, which is located about 13.4 billion light-years away.
Drawbacks
The processing of Hubble images is an intricate and time-consuming procedure. Even simple Hubble photos can take days to process, while large complex mosaics of multiple images can take months, NASA says. However, In every image, there’s a story waiting to be discovered, which makes the wait worth it!
Reference List:
Author. (2020, July 2). From research data to a piece of art: this is how the colourful Hubble images are made. Wonderdome: Planetarium Shows for Schools. https://wonderdome.co.uk/hubble-colour-images-processing/#:~:text=Astronomers%20usually%20use%20three%20filters,by%20stacking%20together%20individual%20exposures.
How are Webb’s Full-Color images made? (n.d.). Webb. https://webbtelescope.org/contents/articles/how-are-webbs-full-color-images-made
Lowndes, C. (2019, August 2). How scientists colorize photos of space. Vox. https://www.vox.com/2019/8/1/20750228/scientists-colorize-photos-space-hubble-telescope
Lea, R. (2023, April 10). How are Hubble Space Telescope images made? Space.com. https://www.space.com/how-hubble-space-telescope-images-are-made
How Hubble Images Are Made, NASA's Goddard Space Flight Center, https://www.youtube.com/watch?v=QGf0yzdM5OA
Hubble Space Telescope Observatory : Instruments, NASA. Accessed 03/24/23 from https://www.nasa.gov/content/goddard/hubble-space-telescope-science-instruments
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