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Longer sentences, more descriptive words (about B1)

Longer sentences, more descriptive words (about B1)

Hubble Uncovers Ancient Galaxy Collision

An illustration of two galaxies in the midst of a collision against a dark, star-filled background. The collision takes up the middle third of the illustration. On the right, a larger galaxy is viewed at an angle from 11 o’clock to 4 o’clock, with a white-yellow core surrounded by mottled brown dust lanes and faint bluish spiral arms. To the left, a smaller, bright blue-white galaxy is stretched into a curved, hook-like shape as gravity distorts it. A broad, glowing bridge of pale blue gas and stars extends off the galaxy at the left, while wispy streams extend above and below the larger galaxy at the right. The words “Artist’s Concept” appear in the lower left corner.
An illustration of two galaxies in the midst of a collision against a dark, star-filled background. The collision takes up the middle third of the illustration. On the right, a larger galaxy is viewed at an angle from 11 o’clock to 4 o’clock, with a white-yellow core surrounded by mottled brown dust lanes and faint bluish spiral arms. To the left, a smaller, bright blue-white galaxy is stretched into a curved, hook-like shape as gravity distorts it. A broad, glowing bridge of pale blue gas and stars extends off the galaxy at the left, while wispy streams extend above and below the larger galaxy at the right. The words “Artist’s Concept” appear in the lower left corner.

The Milky Way reached its current size over time by absorbing smaller neighbor galaxies. New data from NASA's Hubble Space Telescope confirms that a dwarf system merged into our developing galaxy during its initial formation phase. This discovery pushes the known timeline of galactic collisions back by an additional 1.8 billion years.

Today, our galaxy is a massive spiral with hundreds of billions of stars. Its growth comes from internal star creation and external galaxy collisions. Around 10 billion years ago, the Milky Way integrated a system called Gaia-Sausage-Enceladus. Astronomers suspected an even older collision occurred before that event.

To prove this early collision, researchers analyzed a globular cluster named NGC 6388. Hubble observations showed that stars in NGC 6388 contain low amounts of heavy elements. This chemical signature confirms that the cluster originated outside our galaxy and joined it 11.8 billion years ago.

Why do you think scientists spend so much time studying events that happened billions of years ago?

Adapted from NASA Universe.

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