TPO22 The Allende Meteorite - 英檢

請各位大神解惑一下
TPO22 The Allende Meteorite這篇的第二段

When broken open, Allende stones are revealed to contain an assortment of
small,distinctive objects,spherical or irregular in shape and embedded in a
dark gray matrix(binding material), which were once constituents of the solar
nebula-the interstellar cloud of gas and dust out of which our solar system
was formed.

請問最後的out of which our solar system was formed要怎麼解釋?
which指的是甚麼東西?

謝謝~

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