Newspaper article The Christian Science Monitor

Planets Found at Dawn of Universe, but Their Existence Is a Mystery

Newspaper article The Christian Science Monitor

Planets Found at Dawn of Universe, but Their Existence Is a Mystery

Article excerpt

Scientists have found two planets orbiting a star that formed only a billion years after the big bang. But the universe had few planet-making elements then, so how did the planets form?

Two planets from a period near the dawn of the cosmos are hinting that there may be more than one way to sow the seeds of planet formation.

A team of astronomers reports it has found two planets orbiting a star some 376 light-years from Earth in the constellation Cetus. The team estimates that the star is 12.8 billion years old, indicating that the star and its planets formed only a billion years after the universe itself emerged in what astrophysicists have dubbed the big bang.

By contrast, the solar system humans inhabit formed about 4.6 billion years ago.

The results, set for publication in an upcoming issue of the monthly journal Astronomy and Astrophysics, represent what the study's lead scientist, Johny Setiawan, dubs "an archaeological find in our own backyard."

Indeed, the discovery is "remarkable since the planetary system most likely belongs to the first generation of planetary systems in the Milky Way," the team writes.

The star, HIP 11952, has 83 percent of the sun's mass and 1.6 times the sun's radius. It appears to be on the doorstep of its death throes as a red giant, when its core's supply of hydrogen fuel hits "empty." The core collapses, heats, and provides the energy for hydrogen remaining in the star's outer shell to begin fusing into helium. The star brightens, and its atmosphere heats and expands far beyond its current reach.

Orbiting in the path of that expansion are two planets: one with 2.9 times Jupiter's mass orbiting HIP 11952 once every 290 days; the other with 78 percent of Jupiter's mass orbiting the star once every 6.95 days.

Therein lies an intrigue: How did such planets form?

For years, astronomers have held that the stars most likely to host planets are, like the sun, enriched with elements heavier than the hydrogen they burn for fuel - elements such as carbon, nitrogen, oxygen, calcium, and silicon, for example. These are the raw materials for rocky cores around which planets form. …

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