A collection of gas, dust and stars
galaxy
dark nebula
planetary nebula
emission nebula

We sometimes use the word "nebula" to refer to galaxies, various types of star clusters and various kinds of interstellar dust/gas clouds. ... Dark nebulae are also often seen in conjunction with reflection and emission nebulae. A typical ... Planetary nebulae are shells of gas thrown out by some stars near the end of their lives.

Explanation:

when a reversible reaction is occurring in both directions at the same rate; the products and reactants do not change in concentration. a chemical reaction where the compound is broken into its constituent parts.

explanation:

mark brainliest and have a great day!

the truman doctrine was an american foreign policy whose stated purpose was to counter soviet geopolitical expansion during the cold war. it was announced to congress by president harry s. truman on march 12, 1947, and further developed on july 12, 1948, when he pledged to contain threats to greece and turkey.