00:00 As a cosmic photographer, NASA's Hubble Space Telescope has taken over a million snapshots documenting the universe.
00:08 These images illustrate, explain, and inspire us with their grandeur, but may not match what we'd see with our own eyes.
00:17 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 rainbow.
00:32 Light outside that span, with longer or shorter wavelengths, is invisible to our eyes.
00:38 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.
01:01 Seeing in black and white allows Hubble to detect subtle differences in the light's intensity.
01:07 If one wavelength is brighter than another, that tells us something about the science of that object.
01:13 But because color helps humans interpret what we see,
01:17 NASA specialists work to process and 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 wavelengths to pass through.
01:31 Broadband filters let in a wide range of light.
01:35 Narrowband filters are more selective, isolating light from individual elements like hydrogen, oxygen, and sulfur.
01:43 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 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 and white.
02:07 Adding color reveals the underlying science in every image.
02:12 It's like translating words into another language, making sure no information is lost.
02:18 Some words have an exact counterpart. The meaning remains the same when you swap them.
02:24 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 words with no one-word replacement.
02:43 Easily done, but requires more work.
02:47 Narrowband images highlight the concentration of important elements.
02:52 Infrared images are like heat maps, helping us spot newborn stars in dark, dusty clouds, and peer further back in time and space.
03:02 Using ultraviolet, we uncover active aurorae on Jupiter, and learn how young, massive stars develop.
03:10 Image processors also clean up artifacts, signatures in an image that aren't produced by the observed target.
03:17 As sensors age, some pixels become imperfect, returning too much electrical charge or not enough.
03:24 Artifacts can leave behind odd shapes, or return images without any true black.
03:30 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.
03:41 In Hubble's case, the culprits are asteroids, spacecraft or debris trails, and high-energy particles called cosmic rays.
03:49 By combining and aligning multiple observations, image processors can identify them and piece 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 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 and frame the image.
04:27 It's a time-consuming procedure.
04:29 Simple images take about a week, while large mosaics stitched together from many observations 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 invisible views of our universe.
04:52 (upbeat music)
04:54 (upbeat music)
