Astronomy, in general, is the study of celestial bodies, and the universe as a whole, excluding the earth. It includes the study of stars, planets, galaxies and other objects that are beyond the atmosphere of earth. The Bible does reference several objects, such as planets and constellations, found in what we today call space.
For example, the most studied star in astronomy, the sun, is directly mentioned at least 160 times in the KJV translation, with the moon referred to 51 times. During Biblical times, the only planets viewable from the earth were Mercury, Venus, Mars, Jupiter and Saturn. Some of these can be found in Scripture, not by the names we call them today, but through the false gods associated with them.
Astronomy tells us that next to the sun and moon, the planet Venus is the brightest object we can see in the night sky. Its ability to reflect light is due to its close proximity to the sun and the highly reflective clouds of sulfuric acid that shroud it. Many times it can easily be seen just before sunrise, hence its reference as the "morning star." It can even be viewed during the day, lending to it also being called the "day star."
There are allusions in Scripture to Christ being the morning star. Since Venus was the brightest of all the points of light in the sky the analogy would be that Christ would be the brightest (or have the preeminence) over the other heavenly bodies, which are the stars that correspond to angels (2Peter 1:19, Revelation 2:26, 28, 22:16).
According to a 1913 Catholic Encyclopedia article on Astronomy, the planet Saturn is directly referenced in the book of Amos. The Encyclopedia states, "Saturn is no less certainly represented by the star Kaiwan (called "Chiun" in the KJV translation), adored by the reprobate Israelites in the desert (Amos 5:26)." In Stephen's discourse just before his martyrdom, he mentions God's condemnation of ancient Israel's idolatrous worship of "your god Remphan" (Acts 7:43). Remphan was the Egyptian name for Saturn (JFB commentary on Amos 5:26).
According to the JFB, Isaiah 65:11 alludes to Jupiter and Venus when it refers to "fortune" (Hebrew Gad, the Babylonian god linked to Jupiter) and "fate" (Hebrew Meni, linked with Venus). Holy writ also contains several references to constellations or groupings of stars. The book of Job mentions astronomy related phenomena more than any other book. Constellations such as the Bear (Arcturus), Orion, and Pleiades are written about in Job 9:8 - 9, 38:31 - 33 and also Amos 5:8.
How many stars does astronomy tell us exist? Do they truly number like grains of sand? The number of stars in the visible universe (not the entire universe) is currently estimated to be between 10 to the 22nd power (10 sextillion) to 10 to the 24th power (1 septillion).
How incredibly VAST is the universe? What astronomy calls the "observable universe" are those galaxies and other celestial objects whose light (and other signals) has had time since the Big Bang to reach the earth. This means it is estimated that we on earth can "observe" objects 46 to 47 BILLION light years away in any direction. The entire universe itself, however, is much bigger! In fact, because of expansion, with some distant regions speeding away from us FASTER than light, there are vast parts of God's creation that will never be "observable" from earth!
Alan Guth, creator of the theory of cosmic inflation, has approximated the total size of all that was created in the Big Bang. He calculates that it is 300 sextillion, or 3 followed by 23 zeros, times LARGER than the observable universe! God, through astronomy in the Bible, has left mankind with no excuse regarding his awesome power. The heavens are a constant testament that He exists.