00:00 As a cosmic photographer, NASA's Hubble Space Telescope has taken over a million snapshots
00:05 documenting the universe.
00:08 These images illustrate, explain, and inspire us with their grandeur, but may not match
00:14 what we'd see with our own eyes.
00:16 That's because Hubble sees light beyond our sensitivity.
00:21 Our eyes only sense a small fraction of the universe's light.
00:26 This tiny band of wavelengths, called the visible spectrum, holds every color in the
00:30 rainbow.
00:31 Light outside that span, with longer or shorter wavelengths, is invisible to our eyes.
00:37 But those invisible wavelengths can tell us so much more about the universe.
00:43 Hubble houses six scientific instruments that observe at different wavelengths.
00:47 Together, they expand our vision into infrared and ultraviolet light.
00:52 That doesn't mean Hubble can show us never-before-seen colors.
00:56 In fact, the telescope can only see the universe in shades of gray.
01:02 Seeing in black and white allows Hubble to detect subtle differences in the light's
01:06 intensity.
01:07 If one wavelength is brighter than another, that tells us something about the science
01:11 of that object.
01:13 But because color helps humans interpret what we see, NASA specialists work to process and
01:19 colorize publicly available Hubble data into more accessible images.
01:24 When Hubble snaps a photo, it puts a filter in front of its detector, allowing specific
01:29 wavelengths to pass through.
01:31 Broadband filters let in a wide range of light.
01:34 Narrowband filters are more selective, isolating light from individual elements like hydrogen,
01:40 oxygen and sulfur.
01:42 Hubble observes the same object multiple times, using different filters.
01:47 Image processors then assign those images a color based on their filtered wavelength.
01:52 The longest wavelength becomes red, medium becomes green, and the shortest blue, corresponding
01:57 to the light sensors in our eyes.
02:00 Combining them gives us a color image, showcasing characteristics we can't make out in black
02:05 and white.
02:08 Adding color reveals the underlying science in every image.
02:11 It's like translating words into another language, making sure no information is lost.
02:18 Some words have an exact counterpart.
02:21 The meaning remains the same when you swap them.
02:23 Hubble's true color photos are like that.
02:26 They are a direct translation, using broad filters in wavelengths we can see.
02:32 Other words can't be translated directly.
02:35 When we use narrowband filters or peer outside the visible spectrum, it's like translating
02:40 words with no one word replacement.
02:43 Easily done, but requires more work.
02:47 Narrowband images highlight the concentration of important elements.
02:51 Infrared images are like heat maps, helping us spot newborn stars in dark, dusty clouds,
02:58 and peer further back in time and space.
03:01 In ultraviolet, we uncover active aurorae on Jupiter, and learn how young, massive stars
03:07 develop.
03:09 Image processors also clean up artifacts, signatures in an image that aren't produced
03:14 by the observed target.
03:16 As sensors age, some pixels become imperfect, returning too much electrical charge or not
03:22 enough.
03:24 Artifacts can leave behind odd shapes, or return images without any true black.
03:29 These effects can be calibrated and removed.
03:34 Other artifacts come from the dynamic environment of space.
03:38 Even the best photographers get photobombed.
03:40 In Hubble's case, the culprits are asteroids, spacecraft or debris trails, and high-energy
03:46 particles called cosmic rays.
03:49 By combining and aligning multiple observations, image processors can identify them and piece
03:55 together an artifact-free image.
03:58 Without processing, many Hubble images would be divided down the middle.
04:03 This line, called a chip gap, is the tiny space between some camera sensors.
04:08 Hubble moves slightly with each observation, allowing image processors to fill the gap
04:13 and replace faulty pixels.
04:15 This process is called dithering.
04:18 And because there's no natural up or down in space, processors decide how to rotate
04:24 and frame the image.
04:27 It's a time-consuming procedure.
04:29 Hubble images take about a week, while large mosaics stitched together from many observations
04:35 can take a month to process.
04:39 Hubble images may not be what we'd see firsthand.
04:43 Instead, they are tools for understanding science at a glance, shedding light on otherwise
04:48 invisible views of our universe.
04:51 [Hubble]
04:53 (upbeat music)
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