Are the Colours in Space Really Like That?
You probably have seen pictures like this before.
Pillars of Creation, by James Webb Space Telescope
"A bit much, broski" |
Glowing blue clouds surrounding fiery, dusty orange pillars; faint pink and green nebulae; and thousands and thousands of stars.
But if you had a bazillion dollars and went on a spaceship to see these amazing things in person, do you think they would look like that? Afraid to say you would probably be disappointed! "Mrs J, you mean that the dudes at Nasa are lying to us? We fell for a giant lie? IS THE MOON LANDING EVEN REAL???" |
Breathe, child! The issue is not the pictures being fake or true; of course they are true. But they are different than what we would see. Just like we don't see the same as cats or dogs, we also don't see the same as a telescope.
Light comes in many different wavelengths. There are radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma rays. Your eyes detect only a very small section of this enormous electromagnetic spectrum: visible light.
Even within visible light, our eyes have limitations. Faint objects are especially difficult for us to see in colour because the light-sensitive cells that work best in darkness do not give us much colour information.
But a telescope does not have that problem! Its detectors can collect light for a long time, measure extremely faint signals, and in some cases detect wavelengths that human beings cannot see at all.
This means a space telescope is not simply a giant eyeball like ours, but like a scientific light detector.
Light comes in many different wavelengths. There are radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma rays. Your eyes detect only a very small section of this enormous electromagnetic spectrum: visible light.
Even within visible light, our eyes have limitations. Faint objects are especially difficult for us to see in colour because the light-sensitive cells that work best in darkness do not give us much colour information.
But a telescope does not have that problem! Its detectors can collect light for a long time, measure extremely faint signals, and in some cases detect wavelengths that human beings cannot see at all.
This means a space telescope is not simply a giant eyeball like ours, but like a scientific light detector.
BUT THE COLOURSssss
Hate to burst your bubble, but many of the most famous space images do not arrive from the telescope as beautiful colour photographs.
“Most of the cameras that we have on our spacecraft and space telescopes don't take color pictures,” said Heidi Hammel, vice president for science at the Association of Universities for Research in Astronomy, and vice president of The Planetary Society’s board of directors. “They take black and white pictures that are tuned to specific wavelengths of light.”
Tuning space cameras to specific wavelengths of light helps scientists answer important questions about the objects they study, such as what minerals are on the surface of an asteroid, or what elements are in a nebula. Because each space mission has its own unique science questions to answer, different spacecraft are equipped with cameras tuned to different wavelengths.
Those separate images can then be combined into a multicolour image. NASA describes both Hubble and Webb images this way: individual exposures are recorded through different filters and later assigned colours to create a composite.
Think of it as taking several transparent scientific maps and stacking them on top of one another, each map with different information; one with elements found in a cloud, one with heat, one with a specific element, and so on.
The assigned colour helps us tell those maps apart.
“Most of the cameras that we have on our spacecraft and space telescopes don't take color pictures,” said Heidi Hammel, vice president for science at the Association of Universities for Research in Astronomy, and vice president of The Planetary Society’s board of directors. “They take black and white pictures that are tuned to specific wavelengths of light.”
Tuning space cameras to specific wavelengths of light helps scientists answer important questions about the objects they study, such as what minerals are on the surface of an asteroid, or what elements are in a nebula. Because each space mission has its own unique science questions to answer, different spacecraft are equipped with cameras tuned to different wavelengths.
Those separate images can then be combined into a multicolour image. NASA describes both Hubble and Webb images this way: individual exposures are recorded through different filters and later assigned colours to create a composite.
Think of it as taking several transparent scientific maps and stacking them on top of one another, each map with different information; one with elements found in a cloud, one with heat, one with a specific element, and so on.
The assigned colour helps us tell those maps apart.
IT'S ALL A LIIIIIE
Now wait a minute. Not everything we see is the outcome of a scientific decision! If you search for real images of planets, or "visible light" images, then you will see many amazing images that you would probably see if you went off on your spaceship!
The images taken by the Hubble telescope, for instance, despite arriving in black and white, were taken with visible light BUT in post production, colours are assigned by wavelength, and so shorter wavelengths of light are assigned blue while longer are assigned red, for instance. This is exactly how our eye sees colours. Scientists use what is known about colours to assign the most appropriate colour based on visual effect. This is why the Hubble telescope is my favourite!
The images taken by the Hubble telescope, for instance, despite arriving in black and white, were taken with visible light BUT in post production, colours are assigned by wavelength, and so shorter wavelengths of light are assigned blue while longer are assigned red, for instance. This is exactly how our eye sees colours. Scientists use what is known about colours to assign the most appropriate colour based on visual effect. This is why the Hubble telescope is my favourite!
Hubble on the left, Webb on the right
You can see more details on the right, but all the orange and blue are not really there.
Hubble on left, Webb on right
A visible light photograph is trying to reproduce what a human observer might see, but a scientific astronomical image may be trying to answer a completely different question:
Where is the hydrogen?
Where is the hottest gas?
What lies behind this dust cloud?
Which stars are forming?
What wavelengths are coming from this galaxy?
What can this telescope detect that humans cannot?
Colour helps turn those answers into something we can see.
So maybe the best question is not "is this really what space is like?", but instead, "What does this image tell us about space?"
Where is the hydrogen?
Where is the hottest gas?
What lies behind this dust cloud?
Which stars are forming?
What wavelengths are coming from this galaxy?
What can this telescope detect that humans cannot?
Colour helps turn those answers into something we can see.
So maybe the best question is not "is this really what space is like?", but instead, "What does this image tell us about space?"
