meteorites are sometimes found specks of star dust, which is older than the Solar system. However, the new discovery has broken all records of age. It can provide invaluable information about the distant past of our region of the Galaxy.
the Discovery is described in a scientific paper published in the journal PNAS.
As you know, the Solar system was formed from clouds of gas and dust. About 4.6 billion years ago in the bowels of new-born star has started the fusion reaction. This figure is often called the age of the Sun, although the formation of the luminaries, of course, started earlier.
Approximately in every twentieth fell to the Ground meteorite find Presolana grain. It’s specks of star dust, formed even before the birth of the Sun. They have been preserved since that time unchanged, and therefore carry invaluable information about the composition of matter from which the Solar system formed.
the Authors of the new study studied Presolana grain silicon carbide (SiC) from the meteorite that fell in 1969 in Australia. For this fragment of the celestial stone literally rubbed to powder, and then dissolved in acid. Presolar grains with their microscopic size and chemical stability it does not hurt.
“It’s like burning the haystack to find the needle” – compares Philip hake (Philipp Heck) from the University of Chicago, first author of the study.
as a result, In the hands of scientists was 40 grains. Needed to determine their age.
Experts relied on the contents in the samples of neon-21, which is formed under the influence of cosmic rays. At how much stuff has accumulated this isotope, you can determine how long it is bombarded by cosmic rays. So the water level in the bucket to learn how long it stands in the rain, explains hake.
it Turned out that the studied Presolana grains are very different in age. The youngest of them is older than the Sun by 3.9 1.6 million years and the oldest at unbelievable 3 2 billion (!) years. (Here the age of our stardrive is assumed to equal 4.6 billion years). The authors, at least 8% of the samples over lights in a billion years or more.
“It is the oldest solid matter ever found, and it tells us about how our galaxy formed stars. This is one of the most exciting research I ever worked on,” says heck.
Micrograph prosolennogo grain size of about eight micrometers.Illustration Janaina N. Ávila.
About 60% of the studied grains older than the Sun less than 300 million years. Scientists believe that this is a relatively new substance was formed in the stars that erupted seven billion years ago. For a few hundred million years before the birth of the Sun they just entered the period of old age and considerably cooled the atmosphere began to form dust.
“we Have more young beans than we expected, says heck. – Our hypothesis is that most of these grains, whose age ranges from 4.9 to 4.6 billion years, formed at a time of increased star formation. Before the birth of the Solar system there was a time when it was formed more stars than usual.”
This will be another argument in the debate about how varied the intensity of star birth in the milky Way.
“Some people think that the rate of star formation in the Galaxy is constant, he said. But thanks to these grains, we now have direct evidence of the period of enhanced star formation in our galaxy seven billion years ago, obtained with samples from meteorites. This is one of the key findings of our research”.
the Samples were presented to the experts one more surprise. Comparing the contents of the isotopes of neon and helium, the researchers found an unexpected fact. At least 12 of the studied grains were originally part of the larger clumps of interstellar dust. These bodies were approximately 30 times larger than withAmy grains and could be covered with water ice and organics.
By the way, earlier “News.Science” (nauka.vesti.ru) wrote about Presolana grain, reveal important secrets of the flashes of new stars. We talked about the oldest minerals in the Solar system.