Never before has science been able to boast of such colorful images of astronomical objects. We are fascinated by the spectacular beauty of galaxies and nebulae in Hubble's photographs. We are amazed at the images of the incredible planets discovered by Kepler. If ever our descendants manage to get close to these amazing objects, will they see with their own eyes what we see in NASA photographs?
I see - I do not see
A couple of decades have passed, and our perception of space has changed dramatically. And not least (if not primarily) thanks to the Hubble Telescope. It is with his “eyes” that we have been observing the Universe in recent years. The space in the pictures taken by the telescope looks really amazing. But do the objects depicted in the pictures really look like this? Everyone knows that NASA is good friends with Photoshop. And other space agencies do the same. Is it possible to do without image processing? And is it worth it?
Unlike Galileo Galilei and other astronomers, including modern ones, but examining celestial bodies with their own eyes through optical telescopes, modern astronomy practices a different approach. Stars, galaxies, nebulae are sources of radiation of a wide spectrum. From gamma rays to radio waves. Light is visible radiation perceived by the human eye, just a small area on the scale of electromagnetic waves. Therefore, there are many telescopes in orbit. Each of them receives information about the object in its spectrum of electromagnetic waves. And the Hubble itself is capable of registering radiation not only in the visible, but also in the ultraviolet and infrared ranges invisible to human eyes.
The data obtained from different telescopes make it possible to better understand what constitutes an astronomical object. Take, for example, the Crab Nebula, located in the constellation Taurus, which is almost 6,500 light-years distant from us. Below is how it looks using data from different telescopes. Perhaps there are representatives of intelligent life in other worlds. And it may very well be that the eyes of aliens are arranged differently than that of humans. For them, the visible range of electromagnetic radiation may be another part of the electromagnetic spectrum. It is known that many species of animals can see radiation that is inaccessible to the human eye. Bees, for example, see light in the ultraviolet range. Perhaps, for aliens, the usual view of the Crab Nebula will not be the extreme right in the top row, as for us, but for example the second from the left.
Different photographic illustrations can also be made based on the data from one telescope. The Pillars of Creation is perhaps one of the most famous photographs of the Hubble. They are remnants of the central part of the Eagle gas and dust nebula in the constellation Serpent and are approximately 7,000 light-years distant from us.
Considering the “Pillars of Creation”, it is important not to forget that now this part of the cosmos has already changed. Some scientists are convinced that the "Pillars" collapsed 6,000 years ago. The information about how this happened will be brought to us by the light only after 1000 years.
We do not see most of the waves coming from the stars. But the truth is, NASA illustrators often translate data that is invisible to us into visible. This is how the head of the imaging group of the Space Telescope Institute (STScI), Zolt Levey, says: “The telescope can register some of the light that we show in the photographs, but we cannot see it. Why not translate it into a photograph that we can see? " Thus, part of what we see in NASA photographic illustrations is obtained from the registration of infrared and ultraviolet radiation. Yes, on the one hand, if we were next to the objects depicted in the pictures, we would see a different picture with our own eyes. But, on the other hand, the use of an invisible spectrum in images allows us to get the most accurate representation of them. In this case, the shape of the objects does not change.
Space imagery is an effective means of popularizing the work of scientists, but space observatories are not launched outside the planet for spectacular photographs. Their goal is to obtain information about the physical parameters of astronomical objects.
NASA and Photoshop
Hubble's cameras do not take color pictures, like cameras and telephones we are used to, but black and white. And, as already mentioned, they register not only the visible spectrum, but also the one that is inaccessible to our eye - infrared and ultraviolet radiation. To make a black and white image in color, filters are applied. Thus, several images are obtained in different colors. Putting them together, and get those mesmerizing images that NASA accompanies press releases.
NASA astronomer and Adobe Photoshop specialist Robert Hurt is processing Hubble images. Hurt compares his work to what the designers of glossy magazines do. Photo editing is done solely for aesthetic reasons, and also in order not to accidentally mislead the viewer. Original images need editing. The artifacts created by the telescope cameras may outwardly resemble real space objects. All of this is removed from the final image. “We don’t want people to think that there’s something weird flying there that’s not really there,” says Robert Hurt. If you've heard talk that NASA erases UFO images from its images, then they appeared for this very reason.
With planets near distant worlds, everything is much more complicated. With rare exceptions, we are not yet able to see them through any telescope. Such an exception, for example, is the exoplanet 2M1207 b, orbiting the brown dwarf 2M1207 in the constellation Centaurus. It is located at a distance of about 170 sv. years from us. But the image taken with an optical telescope gives us little information about the planet.
But, as a rule, the discovery of exoplanets by ground-based telescopes is a rarity. The main hunter for exoplanets is the Kepler orbiting telescope. Its wavelength range is 430–890 nm. That is, it captures almost the entire visible spectrum and part of the infrared radiation. But "Kepler" is not able to see the planets near the stars. They are too small and far from us. He does not even "try" to consider the planets, he has a different way of working.
To locate the planet, astronomers record the fluctuations in brightness and trajectory of the stars. If there is a periodic drop in the brightness of a star, then there is a high probability that there is a planet. Orbiting around its star, it periodically passes between the star and us, covering part of the disk of its star. This resembles the transit of Mercury and Venus along the disk of the Sun. We only observe them in other stellar systems. The planet simply "takes" part of the light flux coming from the star. This method is called the "transit method". Another method allows you to detect a star by registering a change in its position. The star and its planet revolve around a common center of mass, which means that the exoplanet is swinging its star. In relation to us, such a star is moving away, then approaching the Earth. Measurement of the Doppler shift of the star's spectrum helps to detect such fluctuations. Whatever these values are, they are recorded with sufficient accuracy by modern instruments. Scientists become aware of the size and density of the planet, the period of revolution around its star and how far it is from it. Sometimes in exoplanetary systems located close to us, scientists manage to determine the color of the planet's surface. Thus, observing the star's light reflected from the surface of the planet HD 189733b, astronomers have determined its true color - in this case, an intense blue. This data is then passed on to the artists, who come up with the remaining details themselves.
If the planet is in the habitable zone, then vegetation is possible on it. And the color of the vegetation cover of an exoplanet does not have to be the same as on Earth - green. Kepler-186 is a red dwarf in the constellation Cygnus at a distance of 492 sv. years from our planet - emits light mainly in the red range. According to scientists, vegetation on a planet orbiting a star will most likely have one of the shades of orange. True, the artists still settled on the copper shade of its surface, since they did not dare to illustrate such a bold assumption.
NASA artists are guided by their imaginations and scientific data to describe a possible distant world as accurately as possible. But sometimes they neglect realism for the sake of entertainment. If in the illustration you see a brightly lit surface of a planet, and its star is at the same time behind the planet, this is a reason to think. Where does the light come from? In reality, a space traveler would see illuminated only a narrow sickle at the edge of the planet's disk. As, for example, we from the Earth see the narrow crescent of the young Moon after the new moon.