First Stars in the Universe


The birth of the first generation of stars

Shortly after the cosmological recombination epoch when hydrogen atoms were formed and the cosmic background photons were last-scattered off electrons, most of the photons shifted to infrared, and then the universe would have appeared completely dark to human eyes. It took about a few hundred million years until the first stars were born, which illuminated the universe once again and terminated the Dark Ages. The first stars are thought to be the first sources of light, and also the first sources of heavy elements that enable the formation of ordinary stellar populations, planets, and ultimately, the emergence of life. We use supercomputer simulations to reveal how the first star are born. Our simulations are started from realistic initial conditions that are predicted by the popular inflationary theory. The figure shows the distribution of gas in our simulation. It has a side length of a hundred thousand light-years. There are many small nots at the intersections of the filamentary struture, where the first star nurseries are found.



The first light

The first stars light up the dark universe. According to our computere simulations, after their birth, the first stars grow quickly to become as heavy as ten to hundred times that of the sun. Their growth is "self-regulated" by their own intense radiation.
Picuture made by Takashi Hosokawa


A very massive star is also very hot, with its surface temperature exceeding 100000 degrees. It emits an enormous amount of ultra-violet photons, which heats up the surrounding gas. The figure shows the time sequence of this process.



First supernova explosion

Massive stars end their lives by triggering violent explosion - supernovae. When a star explodes, heavy elements synthesized in the star through its lifetime are dispersed into the surrounding inter-stellar medium. The next generation of stars are born from the interstellar gas enriched with heavy elements in this way. The figure shows how explosion of a massive first star disperse heavy elements indicated in red. The blastwave propage at a speed of 100-1000 km/sec.



Further info:


A review article in Nature
Another review article in ARAA

Science article in 2008
Science article in 2011
NASA press release
CBS news
New York Times
Wall Street Journal
National Geographic



Written by Naoki Yoshida