Topic: Space

A team of students from the University of Chicago discovered an extremely old star drifting into our galaxy. The star is almost pure hydrogen and helium, making it one of the oldest stars ever seen.

A group of undergraduate students at the University of Chicago has made a groundbreaking discovery using data from the Sloan Digital Sky Survey (SDSS). They found one of the oldest known stars in the universe that did not originate in our galaxy. Instead, it formed in a nearby companion galaxy and later moved into the Milky Way.

The star was identified as SDSSJ0715-7334, and it is extremely pure, consisting almost entirely of hydrogen and helium. This chemical makeup indicates it formed very early in cosmic history, making it one of the oldest stars ever observed.

The students worked directly with SDSS data to find this unusual candidate. They examined thousands of stars from the latest survey results, searching for stars that stood out. From this effort, they selected 77 stars for closer study during a planned observing trip.

The team traveled to Carnegie Science's Las Campanas Observatory in Chile and used the Magellan Inamori Kyocera Echelle (MIKE) instrument on the Magellan telescopes. Their first observing session took place on March 21st, 2025. The second star they examined that night quickly stood out.

The star has just 0.005 percent of the metals found in the Sun, making it the most metal-poor star ever observed, more than twice as metal-poor as the previous record holder. Low metallicity is a key indicator of age. Elements heavier than hydrogen and helium are created in supernova explosions.

To better understand the star's history, the team combined their observations with data from the European Space Agency's Gaia mission. This allowed them to calculate both its distance and its motion through the Milky Way.

Why It Matters

This discovery helps us learn more about the early universe and how stars form and evolve over time. It also shows that big data projects like SDSS can be used by students to make important discoveries.

Key Facts

• A team of undergraduate students from the University of Chicago discovered an extremely old star drifting into our galaxy.
• The star is almost pure hydrogen and helium, making it one of the oldest stars ever seen.
• It formed in a nearby companion galaxy and later moved into the Milky Way.
• The star has just 0.005 percent of the metals found in the Sun, making it the most metal-poor star ever observed.
• Low metallicity is a key indicator of age.

Key Terms

Metallicity

A measure of how much of elements heavier than hydrogen and helium a star contains.

Implications

This discovery helps us learn more about the early universe and how stars form and evolve over time. It also shows that big data projects like SDSS can be used by students to make important discoveries.