On Feb. 8, 1969, a blazing meteor streaked across the sky. The fireball came crashing down in Mexico and the event was captured by the eyes of awe-stricken spectators. Fragments of this Allende meteorite were quickly recovered. Included in these fragments where one of the largest carbonaceous chondrites ever found; carbonaceous is classification and chondrite is a non-metallic meteorite that hasn’t suffered any damage and still resembles its parent body.
Recently, research has been conducted on the Allende meteorite by a team of scientist; Gregory Brennecka, Lars Borg and Meenakshi Wadhwa. Their findings have unlocked key information about the early stages of the formation of the Solar System.
The Solar System formed from the matter left behind from a star that went supernova, the death phase of a star in which it explodes it’s enriched guts. The elements left behind form a nebula, a cloud of gas, dust and particles that eventually coalesce and begin the formation of our Solar System some 4.6 billion years ago. However, many questions remained about the galactic environment where the Solar System was born.
Some of the oldest elements from the early formation of our Solar System are found in meteorites. By studying these meteorites, scientists can look at what materials were present when the Solar System formed.
Studying the Allende meteorite has led the team of researchers to believe that sometime during the early formation of our Solar System, new material was injected from a nearby supernova.
“We present isotopic evidence that supports the injection of supernova material into the early Solar System within a small window of time around the formation of the first solids in the proto-planetary disk.” writes Brennecka and his colleagues in a research article submitted to Proceedings of the National Academy of Sciences of the United States of America.
The Solar System is composed of materials that are the result of a nucleosynthetic event occurring during the early formation. This material contains elements heavier than iron which are only formed in supernovae through a nucleosynthesis process called r-process; r-process happens in high neutron densities found in certain types of supernova.
“The isotopic differences between the first solids and subsequently formed matter in the Solar System require the existence of multiple sources of the r-process nucleosynthesis.”
Brennecka and his team studied calcium-aluminum-enriched-inclusions in the Allende meteorite which result from r-process anomalies; these CAIs where the first solids to form inside the cooling nebula. The concentration of the CAIs found in the Allende meteorite are different from the material that make up most of the meteorites and Earth.
This data shows direct evidence of r-process and the research also reveals the timing, extent of mixing, and a source of supernova material being injected into the Solar System.
The researchers assert, “A scenario of late supernova injection into the proto-planetary disk is consistent with the formation of our Solar System in an active star-forming region of the galaxy.”
CAI inclusions are formed in the inner regions of the early Solar System near a young Sun in a time frame as short as 20,000-50,000 thousand years. These CAI inclusions mixed with other material to be preserved in the form meteors. However, for the CAI inclusions found in the Allende meteorite to be preserved, a time frame is placed on the introduction of supernova material.
“The addition of . . . supernova material must have occurred no earlier than 100,000 y[ears] before CAI formation and before the condensation of the. . . bulk of primitive chondritic meteorites that represent the average Solar System composition.”
Further studies may help researchers understand the CAI inclusions found in other samples and what roles other supernovae may have played in the early formation of the Solar System; possibly unlocking secrets to the development of galaxies.
“Radionuclides in the early Solar System can be used to understand the balance between the creation of such nuclides in stars and their decay in the interstellar medium. . . [This] greatly influences our understanding of the dynamic evolution of the galaxy and the nucleosynthetic history of matter.”
Gregory A. Brenneckaa, Lars E. Borga and Meenakshi Wadhwab published their research through the Proceedings of the National Academy of Sciences of the United States of America
For further reading, the published research article can be found at www.pnas.org/content/early/2013/10/02/1307759110