00:00As a cosmic photographer, NASA's Hubble Space Telescope has taken over a million snapshots
00:06documenting the universe.
00:08These images illustrate, explain, and inspire us with their grandeur, but may not match
00:14what we'd see with our own eyes.
00:16That's because Hubble sees light beyond our sensitivity.
00:21Our eyes only sense a small fraction of the universe's light.
00:26This tiny band of wavelengths, called the visible spectrum, holds every color in the rainbow.
00:32Light outside that span, with longer or shorter wavelengths, is invisible to our eyes.
00:38But those invisible wavelengths can tell us so much more about the universe.
00:43Hubble houses six scientific instruments that observe at different wavelengths.
00:47Together, they expand our vision into infrared and ultraviolet light.
00:52That doesn't mean Hubble can show us never-before-seen colors.
00:56In fact, the telescope can only see the universe in shades of gray.
01:02Seeing in black and white allows Hubble to detect subtle differences in the light's intensity.
01:07If one wavelength is brighter than another, that tells us something about the science of
01:11that object.
01:13But because color helps humans interpret what we see, NASA specialists work to process and
01:19colorize publicly available Hubble data into more accessible images.
01:24When Hubble snaps a photo, it puts a filter in front of its detector, allowing specific wavelengths
01:29to pass through.
01:31Broadband filters let in a wide range of light.
01:34Narrowband filters are more selective, isolating light from individual elements like hydrogen, oxygen,
01:41and sulfur.
01:43Hubble observes the same object multiple times using different filters.
01:47Image processors then assign those images a color based on their filtered wavelength.
01:52The longest wavelength becomes red, medium becomes green, and the shortest blue, corresponding
01:58to the light sensors in our eyes.
02:00Combining them gives us a color image, showcasing characteristics we can't make out in black
02:05and white.
02:08Adding color reveals the underlying science in every image.
02:12It's like translating words into another language, making sure no information is lost.
02:19Some words have an exact counterpart.
02:21The meaning remains the same when you swap them.
02:24Hubble's true color photos are like that.
02:26They are a direct translation, using broad filters in wavelengths we can see.
02:32Other words can't be translated directly.
02:35When we use narrowband filters or peer outside the visible spectrum, it's like translating
02:40words with no one-word replacement.
02:43Easily done, but requires more work.
02:47Narrowband images highlight the concentration of important elements.
02:52Infrared images are like heat maps, helping us spot newborn stars in dark, dusty clouds,
02:58and peer further back in time and space.
03:01In Ultraviolet, we uncover active aurorae on Jupiter, and learn how young, massive stars
03:07develop.
03:09Image processors also clean up artifacts, signatures in an image that aren't produced by the observed
03:15target.
03:16As sensors age, some pixels become imperfect, returning too much electrical charge or not
03:22enough.
03:24Artifacts can leave behind odd shapes, or return images without any true black.
03:30These effects can be calibrated and removed.
03:34Other artifacts come from the dynamic environment of space.
03:38Even the best photographers get photobombed.
03:40In Hubble's case, the culprits are asteroids, spacecraft or debris trails, and high-energy particles
03:47called cosmic rays.
03:49By combining and aligning multiple observations, image processors can identify them and piece
03:55together an artifact-free image.
03:58Without processing, many Hubble images would be divided down the middle.
04:03This line, called a chip gap, is the tiny space between some camera sensors.
04:08Hubble moves slightly with each observation, allowing image processors to fill the gap and
04:13replace faulty pixels.
04:15This process is called dithering.
04:18And because there's no natural up or down in space, processors decide how to rotate and
04:24frame the image.
04:27It's a time-consuming procedure.
04:29Simple images take about a week, while large mosaics stitched together from many observations
04:35can take a month to process.
04:40Hubble images may not be what we'd see first-hand.
04:43Instead, they are tools for understanding science at a glance, shedding light on otherwise invisible
04:49views of our universe.
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