Why did God create the other planets(Mars, Mercury, etc.)? Also, if stars
are meant to give us “light” what about other stellar phenomena such as
nebulae and black holes?

In the final analysis I cannot speak for God about why he did what he did.
However there seems to be a perfectly natural explanation for why God
created the planets, stars, galaxies, quasars, black holes and so forth.

A careful study of nature reveals that God has set up the universe in such
a way that the physical universe follows certain invariant laws. These
would include the laws of motion of objects (discovered by Newton), the
laws of conservation of mass and energy (discovered by Einstein), and the
laws of thermodynamics. There is a movement amongst physicists to explain
the laws of nature on the premise that the size of the gravity constant,
the electrical force, nuclear force and so forth were specifically
designed to allow for complex life forms such as humans to exist. These
universal constants have values which are amazingly fine-tuned to the
perfect value to allow life to exist. For more on this, I suggest you go
to the article section in the web site, click on “God” and look at some of
the articles under the heading “Articles on Design.”

Based on this information, I conclude that when God created the universe,
he created it with a sufficient amount and variety of the elements to
cause the inevitable formation of galaxies and stars. As stars form out of
swirling and spinning interstellar media, they inevitably produce planets.
Very recent evidence has shown conclusively that the existence of planets
on stars in not unique to our sun at all, but is rather the norm.
Therefore, when God created the universe, he created the conditions which
ultimately produced Mercury, Venus, Earth, Mars, Jupiter and so forth. In
fact, it has been shown by good evidence that the large planets such as
Jupiter and Saturn provide gravitational protection for the smaller and
more vulnerable inner planets against impacts of large objects such as
asteroids. If it were not for Jupiter and Saturn, there probably would be
no advanced life forms on the earth, at least according to scientific
discovery. You also ask about black holes. According to the laws of
physics, the existence of black holes are an inevitable consequence of the
formation of certain types of very massive stars. It is now believed that
the formation of galaxies depends on the presence of super massive black
holes at the center of these swirling galaxies. If it were not for black
holes, concentrations of stars with heavier elements (necessary to form
life) would not have been created. God did a great job when he created the
laws of nature. Good job God.

John Oakes, PhD