Ultraviolet astronomy

Ultraviolet astronomy is the study of electromagnetic radiation at ultraviolet wavelengths. These wavelengths range from approximately 10 to 320 nanometres.

While humans cannot see this light, it provides a unique view of the cosmos. Shorter wavelengths with even higher energy are studied through X-ray and gamma-ray astronomy. Because Earth's atmosphere absorbs most ultraviolet light, scientists cannot observe it from the ground. Instead, they must use telescopes located in the upper atmosphere or in space. This allows them to capture data that would otherwise be lost.

Scientists use a process called spectroscopy to understand the universe. Spectroscopy involves measuring ultraviolet line spectrums to find specific information. This method allows researchers to discern the chemical composition of the interstellar medium. It also reveals the densities and temperatures within that medium. By looking at these spectrums, astronomers can determine the temperature and composition of hot, young stars.

This data is essential for understanding how galaxies evolve over long periods of time.

The ultraviolet universe looks very different from the one we see with our eyes. Most stars are relatively cool objects. They emit much of their radiation in the visible or near-infrared parts of the spectrum. In contrast, ultraviolet radiation is a signature of much hotter objects. These are typically found in the early or late stages of stellar evolution. For example, very young massive stars produce high-energy radiation. Some very old stars and galaxies also grow hotter as they approach death.

Ultraviolet observations can also reveal hidden celestial companions. They can discern the presence of a hot white dwarf star. This might be in orbit around a much cooler star. In the ultraviolet sky, many common stars would fade in prominence. However, the most energetic objects would stand out clearly. Clouds of gas and dust can also be seen, as they block vision along the Milky Way. This helps astronomers map the structure of our galaxy.

Many important people helped pioneer this field of science. George Robert Carruthers, Robert Wilson, and Charles Stuart Bowyer were key figures. Their work helped establish the foundations of ultraviolet astronomy. Since then, many different types of space-based instruments have been launched. Some are large telescopes, while others are smaller observatories. There have even been missions using sounding rockets and the Space Shuttle. These various tools have allowed for a wide range of scientific discovery.

Space-based observatories have provided a massive amount of data. The Hubble Space Telescope is a major tool for viewing the near and far UV spectrum. It uses instruments like STIS, which covers 115 to 1030 nm, and WFC3, which covers 200 to 1700 nm. Other significant missions include the Galaxy Evolution Explorer, which operated from 2003 to 2012. The FUSE mission studied the sky from 1999 to 2007. We also use solar observatories like SOHO and SDO to watch the Sun. These missions use instruments like EIT to view the Sun's corona.

Ultraviolet technology is even used on spacecraft traveling to other planets. The Cassini spacecraft used the UVIS instrument while studying Saturn. The MESSENGER mission used MASCS to look at Mercury. The New Horizons mission carries the Alice instrument to study Pluto. Other missions, like Juno at Jupiter and MAVEN at Mars, also use ultraviolet tools. These instruments allow us to study the environments of many different worlds in our solar system.