Earth’s atmosphere absorbs most wavelengths of light – including ultraviolet light – which is why telescopes must be positioned above its atmosphere to capture it. In space, ultraviolet light is most often emitted by the energetic processes of young stars. Currently, only Hubble’s instruments are capable of making these observations.

Hubble’s scientific programs are continuously refined and its instruments receive regular software updates, both of which make groundbreaking science possible. Hubble has already begun using even more advanced ultraviolet light observing modes to gather images and spectra more quickly from transient events with the goal of determining the character of objects’ fast-fading light.

The NASA Hubble Space Telescope is a project of international cooperation between NASA and ESA. AURA’s Space Telescope Science Institute in Baltimore, Maryland, conducts Hubble science operations.

If you’ve ever pointed a blacklight – which is an ultraviolet lightbulb – at a blacklight poster, you’ve watched its inks fluoresce. The inks on the poster react to ultraviolet light by emitting visible light our eyes can see. A similar effect occurs with certain minerals, which fluoresce in vivid colors after being hit by the Sun.

Imaging and spectroscopy go hand in hand – scientists require data from both to more fully understand the targets they are studying.

Hubble has also captured ultraviolet radiation and violent stellar winds emitted by newly formed high-mass stars, which blew out an enormous cavity in the gas and dust enveloping star cluster NGC 3603. Star clusters like this one provide important clues to understanding the origin of massive star formation in the early universe.

Hubble’s Wide Field Camera 3 (WFC3), which delivers some of the observatory’s spectacular images, directs light to its ultraviolet-visible light channel, which breaks down the light with filters into specific colors that are present. Once these data are sent to Earth, science visuals developers assign primary colors and reconstruct the data into a picture our eyes can clearly identify. Astronomers and citizen scientists who use specialized imaging processing software can also manipulate the raw data, assigning their own colors to elements to further study an object’s composition.

By making ultraviolet light observations, Hubble has revealed some of the most energetic processes on planets, young stars and star-forming galaxies. For example, far-ultraviolet observations of Jupiter revealed unexpectedly active auroras on its poles that are hundreds of times more active than auroras on Earth. These data points have helped us learn that the auroras are caused by the Sun’s solar storms as well as particles thrown into space by its moon Io, which is known for its numerous and large volcanos.

Ultraviolet light, which has short, high energy wavelengths, lies just outside the range of visible light our eyes can detect. However, even though human eyes can’t detect ultraviolet light, we can see its effects. For example, despite the Earth’s atmosphere filtering out much of the Sun’s ultraviolet light, we may experience that light as a sunburn on our skin.

COS and STIS break the light from a single object into its component colors the way a prism splits white light into a rainbow, recording what’s known as a spectrum. Researchers analyze these data to discover properties of the material interacting with the ultraviolet light.

Ultraviolet light also helps researchers trace the vibrant glow of young, blue star clusters in galaxies like Centaurus A. Its warped shape is evidence of a past collision and merger with another galaxy, and the resulting shockwaves caused hydrogen gas clouds to compress, triggering new star formation.

The observatory also has two instruments that produce ultraviolet spectra – one of Hubble’s most unique capabilities since these instruments will not be complemented or surpassed by any mission in the near future. The Cosmic Origins Spectrograph (COS) breaks ultraviolet light into components that can be studied in detail as a one-dimensional spectrum to learn about a celestial object’s temperature, chemical composition, density, and motion. The Space Telescope Imaging Spectrograph (STIS) can provide additional data about extended objects, like galaxies, as a two-dimensional spectrum.

By sampling star formation in a range of galaxies, Hubble regularly provides additional, detailed information about young, massive stars and star clusters, and how their environment affects their development. In 2017, Hubble joined other NASA missions in observing gravitational waves from two colliding neutron stars. In the future, the observatory will also be able to observe this type of event in ultraviolet light.

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Telescopes above the Earth’s atmosphere with specially designed instruments, like those on the Hubble Space Telescope, are capable of gathering ultraviolet light directly. These ultraviolet observations allow us to analyze auroras on other planets, like Jupiter, learn more about Saturn’s gaseous makeup, capture fast-moving material from tightly orbiting massive stars, and identify areas of new star formation in nearby galaxies.