Astronomers discovered a star that was likely formed in the same celestial nursery as our Sun. The new sibling is only the second to be identified.

Key takeaways

  • Astronomers discovered a star, HD186302, that likely formed in the same stellar nursery as our Sun, making it the Sun’s second known sibling.
  • The Sun and its sibling stars were born in a large cluster, but the Milky Way’s tidal forces scattered them across the galaxy over billions of years.
  • HD186302 is a main sequence star about 184 light-years away, with similar age, chemical makeup, and carbon isotope ratios to our Sun, making it almost a solar twin.
  • The discovery raises the possibility that HD186302 could have habitable planets, potentially even life, influenced by material spread from Earth during the late heavy bombardment period.
  • Scientists plan to use advanced spectrographs to search for planets around HD186302, which could provide insights into the types of planets formed in the Sun’s original stellar nursery.
A composite image of the Sun taken by ASA’s Solar Dynamics Observatory (SDO). NASA/SDO

Didn’t we all had the “Parent Trap” scenario, in which we discovered a long-lost sibling who was separated at birth? For most of us, that fantasy was only a movie storyline, but it has now become a reality for the Sun.

An multinational team of astronomers made a unique discovery: a star that was most likely born in the same celestial nursery as our Sun. After evaluating the properties of hundreds of stars in the Milky Way, the researchers are convinced that they have discovered not just a solar sister, but probably a solar twin.

The near-identical star, named HD186302, is just the second of the Sun’s close cousins to be identified. The discovery might help researchers better comprehend the circumstances in which the Sun and its siblings developed, as well as potentially unearth habitable planets in the twin’s orbit.

A Turbulent Past

The Sun today exists in relative isolation, yet billions of years ago it was part of a youthful, busy neighborhood. Like all stars, it was born in a large stellar nursery among thousands of others. However, the Milky Way’s tidal forces tore apart the nursery, scattering the stars throughout the galaxy. Finding stars has been difficult since they frequently wander far from their birthplaces.

However, experts from the AMBRE project are working hard to discover the Sun’s old family. AMBRE, a partnership between ESO and the Observatoire de la Cote d’Azur, employs an array of spectrographs and data from ESA’s GAIA mission to determine the ages, chemical abundances, and movements of stars in the Milky Way. Researchers at Portugal’s Instituto de Astrofísica e Ciências do Espaço (AI) used a large dataset to study 17,000 stars.

Mirror Image

After looking through the cosmic records, the researchers discovered a star that has a striking likeness to the Sun. HD186302 is a main sequence star located about 184 light-years from Earth. The star has a similar age, metallicity, chemical abundances, and even carbon isotope ratios to the Sun. In other words, it’s nearly identical to the Sun. With these unmistakable similarities, it is just one of two stellar siblings ever recognized, trailing only HD 162826, which was discovered in 2014.

Astronomers might use these commonalities to establish the sort of environment in which the siblings developed, therefore painting a picture of their now-defunct stellar nursery and the other family members who were born there. The discovery also leads researchers to wonder if, like the Sun, HD186302 could house life and habitable planets.

“Some theoretical calculations indicate that there is a non-zero chance that life spread from Earth to other planets or exoplanetary systems during the late heavy bombardment. If we are lucky, and our sibling candidate has a planet, and the planet is rocky, in the habitable zone, and finally if this planet was ‘contaminated’ by life seeds from Earth, then we have what one could dream of – an Earth 2.0, orbiting a Sun 2.0,” said lead researcher Vardan Adibekyan, whose discovery of HD186302 was published in the journal Astronomy & Astrophysics, in a news release.

In a follow-up study, the team intends to search for planets around the star using ESO’s ESPRESSO and HARPS spectrographs. If discovered, researchers might compare planets produced around our Sun to those formed around one of its siblings, revealing the sorts of planets that our old star cluster may have left behind.

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