快猫短视频

MYSTERIOUS bursts of X-rays from the heavens might be the death cries of the
first stars to light the Universe. Astronomers in Italy suggest that X-rays
occasionally spotted by satellites might come from explosions of monster stars
that roamed space before galaxies formed.

These 鈥淴-ray transients鈥� are similar to gamma-ray bursts鈥攕hort flashes
of gamma rays thought to come from very massive stars as they explode and
collapse into black holes at the end of their lives. But the X-ray versions last
from 10 seconds to a few minutes鈥攍onger than gamma-ray bursts鈥攁nd
the radiation has a longer wavelength.

Now Raffaella Schneider and her colleagues at the Arcetri Observatory in
Florence suggest the X-ray transients might come from explosions of the very
first stars to populate the Universe. These were probably enormous stars several
hundred times the mass of the Sun
(快猫短视频, 9 September 2000, p 25).
Some would have exploded and collapsed to form black holes when the
Universe was only 100 million years old, so for us to see the explosions today,
their light would have to travel the cosmos for around 14 billion years before
reaching Earth.

This huge distance might have made gamma-ray bursts from these stars look
like fast X-ray transients, Schneider concludes in a report submitted to
Monthly Notices of the Royal Astronomical Society. The Universe has
expanded enormously in the time the light took to travel to Earth. This would
stretch the light to longer wavelengths and also make the explosions appear to
last longer, an effect called time dilation.

If Schneider鈥檚 hunch is correct, these flashes could reveal when the first
ever stars lived and died. 鈥淚t would be a great breakthrough in our
understanding of how the Universe turned from darkness into light,鈥� she says.