Hubble images taken 25 years apart show major changes in the iconic Crab Nebula — Space Photo of the Week

The Hubble Space Telescope’s remarkable lifespan has given astronomers the opportunity to observe not only how distant celestial objects look up close, but also how they change over time.

This week, NASA announced a surprising example. A comparison of two Hubble images from 1999/2000 and 2024 shows how the Crab Nebula, the remains of an exploded star, has expanded and evolved over a quarter-century of Hubble images.

Few objects in the night sky are as iconic as the Crab Nebula, the cosmic cloud that connects ancient astronomy with modern space telescopes. In 1054, a supernova in the constellation Taurus lit up the daytime sky for several weeks. This event was recorded by early astronomers in Japan, China, and the Middle East. Although this “guest star” eventually disappeared from view, it remains one of the best-documented cosmic explosions in human history.

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Centuries later, in the mid-18th century, the Crab Nebula was discovered in the constellation Taurus. Astronomers, including Edwin Hubble in the 1950s, associated the Crab Nebula with the 1054 supernova. The decisive trigger was the discovery of a pulsar (a rapidly rotating neutron star, a typical remnant of a supernova explosion) at the center of the Crab Nebula.

This pulsar has been busy expanding the nebula in the 25 years since it was first imaged by the Hubble Space Telescope. The latest observations of the Crab Nebula, published earlier this year in The Astrophysical Journal, allow astronomers to measure the outward movement of the nebula’s intricate filaments.

The difference between the two images may seem small, but the filament is expanding at about 3.4 million miles (5.5 million km/h). This expansion is not caused by a shock wave from the initial explosion, as in many supernova remnants, but by a pulsar whose powerful magnetic field pushes charged particles outward. This energy source drives the expansion of the nebula and illuminates its glowing filaments.

The image, powered by Hubble’s High-Resolution Wide-Field Camera 3 (installed by astronauts in 2009), allows scientists to see 3D structure and detail, with blue regions showing the hottest and least dense gas, and yellow and red tones indicating energetic sulfur and oxygen. (Photos from 1999/2000 have also been reprocessed to match Wide Field Camera 3 resolution.)

“We tend to think of the sky as fixed and unchanging,” Johns Hopkins University astronomer William Blair, who led the observations, said in a NASA statement. “However, the longer lifespan of the Hubble Space Telescope has revealed that even objects like the Crab Nebula continue to expand and move from the explosion about 1,000 years ago.”

Hubble is not the only telescope to successfully photograph this spectacular supernova remnant. In 2023, the James Webb Space Telescope also captured incredibly detailed shots of the Crab Nebula, which later helped scientists map the cosmic dust inside its expanding shell, NASA said.