Dust drifting in the space between stars blocks part of the light that reaches Earth, making stars appear fainter than they really are, according to a report published by 비건뉴스 on November 7, 2026. Astronomers call this dimming interstellar extinction. The same dust also changes the color of starlight, a separate effect known as interstellar reddening.
The report draws on educational material from the European Space Agency (ESA) to explain how the two phenomena differ. Extinction refers to a loss of brightness, while reddening refers to a shift in color.
Why it matters
The effects are not only a matter of appearance. Because dust alters both the brightness and the color of stars as seen from Earth, astronomers must account for it when working out a star's properties and its distance. ESA's CESAR educational material, cited in the report, notes that failing to correct for interstellar dust can lead observers to conclude that a star is cooler or farther away than it actually is.
ESA's documentation for the Gaia Data Release 3 makes a similar point, stating that an observed spectrum can be dimmed and reddened depending on how much dust lies along the line of sight.
Why blue light suffers more than red
The report explains that dust does not treat all wavelengths of light the same way. Shorter wavelengths, such as blue light, are absorbed and scattered more heavily than longer red wavelengths. As a result, a star viewed through dust appears redder than it would without the dust in the way.
This color shift is what astronomers call interstellar reddening, and the report stresses that it should not be confused with extinction, which describes the drop in brightness. ESA's teaching resources on the interstellar medium describe the two effects separately for the same reason, presenting one as a reduction in brightness and the other as a change in color.
Infrared views pierce the dust
The report also notes that infrared observations offer a way to study stars hidden behind dust clouds. In an example from ESA's Euclid mission, stars that appeared dark in visible light showed up more clearly in near-infrared images taken through a dust cloud.
Near-infrared light is not entirely immune to dust, according to the report, but it passes through dust more readily than visible light does. That makes infrared imaging a useful tool for observing regions where visible-light views are obscured.
The report, published by 비건뉴스, is an explanatory piece on how cosmic dust shapes what telescopes record. What to watch: how upcoming survey data, including releases from missions such as Gaia and Euclid, are used to correct for dust and refine measurements of stellar brightness, color and distance.
