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The outer gas giant planets — Uranus and Neptune in particular — appear distinctly bluish in color. What causes this blue appearance?

Cosmologists have estimated the age of the universe using multiple independent methods. What is the currently accepted age of the universe?

Hydrogen and helium are the most abundant elements in the universe, but heavier elements also exist. Where were elements heavier than hydrogen and helium created?

Some properties of a star change depending on the observer’s distance, while others remain constant. Which property of a star would remain unchanged if observed from twice the current distance?

Looking up at the night sky with the naked eye, some stars appear much brighter than others. Which of the following stars has the greatest apparent brightness as seen from Earth?

Elliptical galaxies are classified on a scale from E0 to E7 based on their apparent shape. Which class appears most spherical?

Scientific notation is used to express very large and very small numbers. Which of the following correctly expresses ‘thirty-two hundred thousand meters’ in scientific notation?

The diagram below shows electrons transitioning between energy levels in an atom, each absorbing a photon. Which transition absorbs the photon with the least energy?

How do astronomers know that hydrogen gas is present in Emission nebulae?

A star with a right ascension of 13 hours is crossing the meridian (transiting) at noon today. At what time will a star with a right ascension of 7 hours transit the meridian?