Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2020 December 27
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Cosmic Latte: The Average Colour of the Universe
Colour Credit: Karl Glazebrook & Ivan Baldry (JHU)

Explanation: What colour is the universe? More precisely, if the entire sky were smeared out, what colour would the final mix be? This whimsical question came up when trying to determine what stars are commonplace in nearby galaxies. The answer, depicted above, is a conditionally perceived shade of beige. In computer parlance: #FFF8E7. To determine this, astronomers computationally averaged the light emitted by one of the larger samples of galaxies analyzed: the 200,000 galaxies of the 2dF survey. The resulting cosmic spectrum has some emission in all parts of the electromagnetic spectrum, but a single perceived composite colour. This colour has become much less blue over the past 10 billion years, indicating that redder stars are becoming more prevalent. In a contest to better name the colour, notable entries included skyvory, univeige, and the winner: cosmic latte.

Gallery: Notable images of the Great Conjunction submitted to APOD
Tomorrow's picture: eagle space

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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
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