The world's most expensive telescope - James Webb Space Telescope (JWST) finally sent back its first photo. To be precise, the JWST team released the first five sets of space pictures. The details of the pictures are clear and extremely shocking. People are impressed. No wonder some people say: This 10 billion is well spent!
Part of the Carina Nebula captured by the Webb Telescope
Is our universe really so beautiful? The answer will disappoint you: Space is not as colorful as you think, The nebulae in the Milky Way are not so luxurious and beautiful. In fact, they look very dim. , if it were not for the astronomical (art) experts who have worked hard to retouch the pictures. , I am afraid that most people will not be interested in it.
You understand correctly, these beautiful pictures are produced using computers to attract your attention.
Actually, the above picture looks like this after being synthesized:
What the Carina Nebula looks like before coloring
Yes, it is a black and white picture, including the earliest Webb test picture released by NASA, the red of the starry sky It was also added using a computer to indicate that this was a photo taken by an infrared telescope .
What is infrared ? Is infrared red? No, it is light invisible to our naked eyes. Human eyes are sensitive to light with wavelengths in the range of approximately 380 to 750 nanometers. The electromagnetic waves in this frequency band are called "visible light", and those with longer wavelengths than this range are called For infrared rays. All objects with temperature can emit infrared light, but it can only be detected with instruments.
The range of visible light for the human eye is very limited
During the COVID-19 epidemic, infrared thermometers can be seen everywhere in public places, which use the difference in infrared wavelengths emitted by hot objects to measure temperature.
Infrared light emitted by objects of different temperatures
The Webb telescope is a huge infrared instrument. It measures the temperature of various celestial bodies and gases in the universe. To be more precise, scientists use it to receive infrared emissions from all objects in space. The wavelength of electromagnetic waves. The image sensor on the Webb telescope can image infrared light with a wavelength of 600 to 28,500 nanometers, and 625 to 750 nanometers is what we see as red. Therefore, it is not "random" for the NASA team to turn Webb's test pictures into red.
Three space telescopes receive different spectrums of light
However, scientists spend huge sums of money to build telescopes and send them to the sky, not to see the scenery, but to use them to explore the secrets of the universe: How was the universe formed? Is " big bang " true? How will stars and galaxies evolve? What elements are there? Where is oxygen , water and life? ...All these questions can be answered in the spectrum.
Various planets in the universe will emit light, and nebulae and interstellar materials will absorb light. Since different atoms and molecules have different emission and absorption spectral lines, we can use these spectral lines to determine what is happening in distant space. Something.
The space telescope explores the composition of matter through spectrum
Previously, the United States has launched the Hubble Space Telescope and Spitzer Space Telescope . Hubble covers the frequency band from ultraviolet to part of the near-infrared. Spitzer is a medium The far-infrared telescope and Webb fill the gap between Hubble and Spitzer in the infrared region. Some friends say that Webber is the "successor" of Hubble. In fact, this is a misunderstanding.
Infrared rays can penetrate black plastic bags
Because the wavelength is longer, infrared rays can pass through dense interstellar molecular clouds and dust, so Webber can see stars that are invisible to Hubble Telescope and when photographing the more distant universe , Weber's image is clearer.
The Webb telescope takes infrared images, and the data sent from its image sensor has no "color" visible to the human eye.Light starts from distant celestial bodies and travels hundreds of millions of kilometers to reach the Webb Telescope, where it undergoes complex transmission, passes through filters and shutters, and finally forms an image on the sensor.
There is a complex filtering system in the Webb telescope
Similar to the Hubble telescope, there is also a set of filters in the Webb telescope. Each filter only allows light of a specified wavelength to pass through, and photons of other wavelengths all are intercepted, so that only the information of photons of this specified wavelength will be displayed on the sensor.
Webber collected the spectra of different stars in the center of the Milky Way
In this way, when the space telescope "stares" at a planet in the universe, what it gets is not a color image of the planet, but a strip of "0" and " 1" spectral line data, these data reveal the secrets of planet composition, which is what scientists are most interested in.
Scientists are more interested in spectra
Now let us return to the original question, how did Weber's color photos come from?
Take the Southern Ring Nebula (NGC 3132) as an example. The Webb Telescope's Near Infrared Camera (NIRCam) imaged it using filters F090W, F187N, F212N, F356W, F405N, and F470N respectively. These images respectively include the interior of the nebula. Different spectral information, but all we can see are black and white pictures.
After receiving this set of photos, NASA technicians colored them respectively. F470N and F405N were colored red, F356W yellow, F212N green, F187N cyan, and F090W blue. Then these colored pictures are superimposed to form a gorgeous nebula picture:
"pseudo-color" image synthesis of the Southern Ring Nebula
Please note: The Webb Telescope's NIRCam is a near-infrared camera. Other colors cannot be represented, so the Southern Ring Nebula you see is actually "fake" by coloring several black and white pictures. This is not its original color. Or you could say it's pseudo-color after "overclocking" it.
Near-infrared and mid-infrared pseudo-color images of the Southern Ring Nebula
Similar to the Southern Ring Nebula, the first batch of photos released by the Webb team do not have much scientific value in terms of color alone, and astronomers are more interested in black and white. But colorful pictures are beautiful and spectacular, which can arouse public interest and inspire everyone's enthusiasm for exploring the universe. This is considered to have achieved the goal.
#Webb Telescope# #Webb Telescope’s first batch of full-color images of the universe#
