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Visual Extraterritorial Astronomy: Ultraviolet (UV)

Earth’s atmosphere is not permeable to photons with certain energies. Ultraviolet, which has energy between 1015 and 3×1016 Hz and wavelength between 10 nm and 300 nm, is also one of them. Molecules in our atmosphere, the main one of which is ozone, do not allow purple to pass through the atmosphere. Of course, this does not mean that all morose waves are blocked. For this reason, especially on summer days, staying under sunlight for a long time will mean being exposed to quite a lot of purple. But the amount of morose that passes is quite small compared to what comes into the atmosphere. So in order to make astronomical observations in purple, we have to go out of the atmosphere, into space.

Ultraviolet (UV) study areas


Only less than 8% of the radiation from the sun is in the 150-400 nanometer range. At wavelengths less than 300 nanometers, the sun’s radiation is only 1% of its total radiation.

At wavelengths greater than 200 nanometers in the Ultraviolet range, photospheric continuity rides on the main absorption lines. The Balmer (365 nm) and Lyman (91.2 nm) series of hydrogen contribute to continuous absorption.

Most ultraviolet observations of the sun begin in the chromosphere layer, where the temperature rises, most ultraviolet radiation from the sun comes from this layer. On the other hand, observation of phaculae, bright structures associated with sunspots, is made in the near Purple. However, observations of spurts (prominence), bright structures that can be observed to reach the corona, especially during a solar eclipse, are also made in morose areas.

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We know that morose is a wavelength range located in a relatively high energy region. Since each body emits a black body radiation due to its temperature, we expect areas with an excess temperature to glow in the purple. Since the temperature in the corona, the outermost layer of the sun, reaches 106 Kelvin degrees, observation of this region can also be made in the morose and X-ray region.

At the same time, The Shape of the corona is highly dependent on the cycle of activity in the Sun. In its maximum period, the corona appears to be a more symmetrical structure around the solar disk, while in its minimum period it is more spread over the equatorial plane of the Sun.

When talking about energetic events, it is not possible to skip the flares that occur on the Sun. These flashes can emit energy at the level of 1027 to 1032 erg per second. Flashes observed at almost all wavelengths are also studied in the purple region, usually in the range of 1-103 nm.

Solar System

Ultraviolet, due to its high energy, is very prone to interaction with matter. Entering the atmosphere of a planet, ultraviolet can basically go through the following stages:
Aerosols in the environment (dust, etc. scattering of photons by ) ,
Absorption of light in Ultraviolet in the atmosphere,
Gas in the atmosphere is emulated and followed by fluorescence and release process,
Photoionization and photointegration processes that cause chemical reactions.

The morose beam coming out of the sun is highly effective on planets and their moons. If the ultraviolet-exposed planet does not have an atmosphere, the ultraviolet can access the surface directly without interacting with the atmosphere. In this way, a number of chemical reactions can be triggered on the surface of the planet directly exposed to purple, as well as cause erosion (on Mercury and the Moon). If the planet has an atmosphere, ultraviolet will interact with this place first. Here, it can also initiate processes that cause molecules to disperse and form.

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The answer to the question of why there is no water in Venus ‘ atmosphere can be explained by the morose radiation that Venus is exposed to. If H2O was present in Venus ‘ atmosphere, ultraviolet could decompose it into H2 and O2. H2 could not hold onto Venus ‘ atmosphere and escape, while O2 would remain. In this case, Venus ‘ atmosphere would contain only O2 instead of water. This condition is called the runaway greenhouse effect.1,9

At the same time, ultraviolet can divide H2O into H and Oh. In addition, CO (carbon monoxide) can also be divided into carbon and oxygen. So with the simplest approach, ultraviolet has quite a significant effect on molecules. In addition, during the maximum time in The Sun, Venus ‘ ionosphere increases its height, and the electron temperature almost doubles.


Morose photons from The Sun have enough energy to affect the middle and upper layers of Earth’s atmosphere. Ionospheric electron density changes, especially during the activity of the sun, are observed in the EUV (extreme ultraviolet) wavelength range.

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The most important effect of purple on the Earth’s atmosphere is the formation process of ozone. Morose rays interacting with O2 can separate the oxygen atoms that make up this molecule from each other. It also combines an oxygen molecule (O2) with an oxygen atom (O), causing the formation of ozone (O3). During this reaction, other molecules that act as catalysts also enter, but they exit unchanged. So the amount of ozone in the Earth’s atmosphere is linked to the amount of morose radiation coming directly from the Sun.


Most of Mars ‘ atmosphere is made up of CO2 (carbon dioxide). Although Mars has a thin layer of atmosphere, the high levels of carbon dioxide present in its atmosphere significantly prevent ultraviolet radiation from reaching the surface (especially ultraviolet with a wavelength of less than 200 nanometers). Morose radiation, which interacts with CO2 in the atmosphere, also causes atmospheric glare (airglow). Based on the observation of this flare, calculations can be made about the amount of escape of the hydrogen that causes it.


Because Mercury is close to the Sun, It is very affected by the Sun. Studies suggest that strong solar winds and EUV radiation caused by the young Sun (0.5 – 1 billion years) swept the early atmosphere of Mercury (Ribas et al. 2004). That’s why Mercury has a rather unstable, thin atmosphere. The pressure that solar winds exert on Mercury is 7 times greater than it applies to Earth.

Gas Giants

We know that planets that are gas giants are quite large compared to rock structures. In addition, it also shows quite interesting color distributions, especially Jupiter. Most of its atmosphere consists of hydrogen and helium, but it also contains methane, ammonia, H2S and water. Jupiter is a very cold planet because it is far from the sun, because it is exposed to very little solar radiation. For this reason, we expect only volatile molecules to be found in the upper layers of the atmosphere and interact with the incoming purple radiation. Jupiter, which already receives little radiation due to its distance from the sun, is still very affected by low-emission morale.

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The presence of color bands seen on Jupiter and similar giant gas planets can be explained by the interaction of molecules located in different layers of the atmosphere with ultraviolet radiation. For example, when purple Rays separate the H2S molecule, S8 is formed by the reaction that follows, and this molecule is yellow. Similarly, ammonium Polysulfate (NH4)xsy is orange and hydrogen Polysulfate HxSy is brown.1,10

Comets and meteorites

Comets are sometimes quite close to the sun, sometimes quite far, especially because of their very flattened orbits. As they approach the sun, it is clear that they will be highly affected by radiation from the Sun. When water molecules are exposed to this morose radiation from The Sun, they can decompose into oxygen, hydrogen and hydroxyl (OH). Hydroxyl is one of the most commonly found components, especially in Comet comas.1,11

As we mentioned earlier on rocky planets, morose radiation can affect the surface of comets. At this point, rather than issues such as erosion, it is quite important what kind of chemical reactions will occur. Especially under certain conditions, it is possible to form amino acids from complex molecules that form the basis of life.1,12

Hot and massive stars

The dynamics in star formations and the various physical feature distributions of stars also cause different kinds of events to occur. One of them is Be Stars. Be stars are stars with an effective temperature of 10,000 K to 30,000 k, with a fairly high rotation speed of 200 kilometers per second, ranging from radiation classes III to V. Violent stars show winds and experience significant mass loss. For this reason, there is a disk of gas that surrounds the star.

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As we know, these stars, which are quite hot for a star, will make high-energy radiation much more than The Sun. Especially since there is also a gas disc surrounding it, we expect this high-energy radiation to affect the disc. Indeed, this is the case, and be stars ionize the interstellar medium around them by the purple radiation they release. These effects can reach up to several hundred parsecs. This is why be stars play a very important role in heating the gas in the arms of galaxies.

Mass loss with stellar winds is quite significant. Large-mass stars can lose almost half of their mass in this way. So it is clear that they will have a very important role in galaxy evolution.

White Dwarfs

White dwarfs are stellar residues consisting of a hot core that stars with Sun-like mass leave behind after passing a planetary nebula, releasing their outer layers into space at the end of their lives. White dwarfs continue to cool during their lifetime, showing no development. Because these structures are quite hot, studying them in purple gives us important information.

Thanks to purple research conducted on white dwarfs, the presence of heavy elements has been observed in hydrogen-rich stars with a temperature of 40,000-50,000 K. In addition, we know that many star systems exist in dual systems. If the mass of one of these components is different, the component with excess mass evolves first and may come to the white dwarf stage. Again, thanks to morose observations, observations of double systems suspected to have a white dwarf component were made.

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In addition, the resulting EUV flux can be expressed as a strong function of effective temperature (Teff) and surface gravity (logg). In this way, the flux observed in the EUV region will give significant information about these parameters. Measurement of gravity on the surface is very important, since determining the radius if its mass is known means determining the mass in appreciation of knowing the radius.


Supernova are violent explosions that large-mass stars undergo late in their lifetimes. Since all elements that develop from hydrogen as a result of nuclear reactions occurring in the star are spread to the Galaxy environment by this explosion, they are responsible for the metallic richness of the interstellar medium.

Type Ia supernova have been characterized by a lack of hydrogen in their spectra. They occur as a result of the transfer of matter to the white dwarf by the gathering disk formed around a white dwarf component. Type Ia supernova are very important in terms of cosmology. Because they have a specific glow profile. If you know that a celestial body will show the same radiation anywhere in the universe, you can find its distance from the decrease in radiation that you measure. In this way, Type Ia supernova are used as standard candles in cosmology. Because they are very bright, they can also be seen from far away.

An important case with Type Ia supernova is that their morose Spectra drop rapidly with frequency. For this reason, it is very difficult to observe a type Ia supernova at short wavelengths (<250 nm).

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Type II supernova, on the other hand, occur at the end of the lifetimes of stars with a mass greater than 8 solar masses. Unlike Type Ia supernova, they show hydrogen lines in their spectra. At the same time, the eruption, which interacts with the Environmental material formed before the supernova, creates strong keel lines. For example, N V at 124 nanometers and C IV at 155 nanometers. At the same time, type II supernova overlap with prominent hydrogen lines and broad P-Cygni lines, with strong continuity.

Interstellar medium (ISM)

Observations of the interstellar environment are very important. At the beginning of everything, because it refers to the distribution of gas and dust within the galaxy, the evolution of the Galaxy carries quite important information about the lives of stars. Large amounts of H2 molecules have been discovered thanks to morose observations of interstellar matter. Heavy element abundances were found to be less than thought. The missing elements, on the other hand, are trapped by interstellar dust particles. At the same time, the abundance of deuterium, which plays a key role in research on nuclear processes, was determined. This is thought to be deuterium left over from the Big Bang.

Ultraviolet (UV) satellites

In the 1960s and early 1980s, sound rockets were carried out with high-altitude balloons and manned space missions such as Apollo and Skylab. Following these, Copernicus (OAO-3) was launched in 1972 and IUE (International Ultraviolet Explorer) in 1978.1,2,3 with ASTRO projects, important work has begun in the ultraviolet field.1,4

Orbiting Astronomical Observatory (OAO): thanks to four satellites launched by NASA between 1966 and 1972, the first high-quality ultraviolet (UV) observations were obtained. The last of these was OAO-3 (Copernicus), which among others was the longest running and the most successful data provider. Copernicus carried a ultraviolet telescope and an X-ray detector (detector) and operated from 1972-1981. It detected the presence of H2 and CO molecules in the interstellar medium. He also discovered the O VI distributions, which indicate the distribution of hot gas in space.1,3

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International Ultraviolet Explorer (iue): worked in 1978-1996, during which time it presented high-resolution (0.01 nm) and low-resolution (0.6-0.7 nm) spectrophotometry (spectral photometry) data between 115-320 nanometers. It obtained morose Spectra (spectra) of 104,000 Galactic and extragalactic objects.1,2

Extreme Ultraviolet Explorer (EUVE): operating from 1992-2001, EUVE operated in the range of 7-76 nanometers. He worked on mapping the entire sky using his imaging and spectroscopic devices. Warm white dwarfs, coronal stars and interstellar medium were also areas of study.1,7

Far Ultraviolet Spectroscopic Explorer (FUSE): operating from 1999-2007, this satellite achieved a high-resolution ultraviolet spectrum of 3000 objects in the remote ultraviolet (90.5-119.5 nm). It showed that less deuterium was burned in stars, consistent with models of the evolution of galaxies, just as interstellar matter obtained important information about the chemical components of Galactic and extragalactic objects.1,5

Galaxy Evolution Explorer (GALEX): running from 2003-2012, GALEX mapped the entire space. It had two broad bands centered at wavelengths of 135 and 283 nanometers. He gave important information on the evolution of galaxies.1,6

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Hubble Space Telescope (HST): Hubble, which started working in 1990, offered us great visuals, as well as being able to work at a wavelength of 120-400 nanometers and near infrared. With the ability to take high resolution photographs (0.05 arc seconds), Hubble provided important insights into the structures of quasars and the interstellar medium in particular.1,8


1. Intеrnatiоnal Ultraviоlеt Explоrеr (IUE),
2. Orbiting Astrоnоmical Obsеrvatоry (OAO),
3. ASTRO Prоjеcts,
4. Far Ultraviоlеt Spеctrоscоpic Explоrеr (FUSE),
5. Galaxy Evlоtuiоn Explоrеr (GALEX),
6. Extrеmе Ultraviоlеt Explоrеr (EUVE),
7. Hubblе Spacе Tеlеscоpе (HST),
8. Runaway Grееnhоusе Effеct,
9. Harоld A. Papazian, Thе Cоlоrs оf Jupitеr,
10. V. A. Krasnоpоlsky еt al., Watеr vapоr and hydrоxyl distributiоns in thе innеr cоma оf cоmеt P/Hallеy mеasurеd by Vеga 2 thrее-channеl spеctrоmеtеr TKS,
11. Max P. Bеrnstеin еt al., Racеmic aminо acids frоm thе ultraviоlеt phоtоlysis оf intеrstеllar icе analоguеs,

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