Astronomy: The Science of Observation

• Astronomy: The study of the sky, the science behind celestial phenomena and cosmic objects, and the exploration of the origins of the universe you inhabit.

• Professional astronomers

  • They carry out their astronomical work by using telescopes to observe the stars' visible light or by listening for radio waves that travel to the stars.

  • They research the Sun, the solar system, the Milky Way, and the cosmos beyond.

• Asterism

  • Star pattern that’s not identical to one of the 88 recognized constellations.

  • It might only contain stars from one constellation, or it might contain stars from several different constellations.

• Amateur astronomers

  • When observing the sky with their naked eyes, binoculars, and telescopes, they typically know the constellations and use them as compass points.

  • They crisscross the Earth to take pictures of the shadows cast by asteroids passing in front of bright stars, track the brightness of variable stars, find asteroids, comets, and exploding stars.

  • They even contribute to professional research projects using their smartphones and home computers.

The Language of Light

• Light provides us with knowledge about the stars, nebulae, and star clusters in our galaxy as well as the planets, moons, and comets in our solar system.

• Some basics of recognizing and describing what you see in the sky are:

  • Star and planet distinction.

  • Identifying constellations, individual stars, and other sky objects by name.

  • Observing brightness (given as magnitudes).

  • Understanding the concept of a light-year.

  • Charting sky position.

• Planet: It comes from the ancient Greek word planetes, meaning “wanderer.”

• Ancient astronomers divided the sky into imaginary figures:

  • Ursa Major, the Great Bear;

  • Cygnus, the Swan;

  • Andromeda, the Chained Lady; and

  • Perseus, the Hero.

• Today, astronomers have divided the sky into 88 constellations, which contain all the stars you can see.

• International Astronomical Union: It governs science and establishes constellation boundaries so that astronomers can agree on which stars belong to which constellation.

• Hydra: The largest constellation; the Water Snake.

• Crux: The smallest constellation; the Cross.

• Individual stars in a constellation often have no relationship to one another other than their proximity in the sky as seen from Earth.

• Serpens: The Serpent; is broken down into two sections. These sections are located on either side of Ophiuchus, the Serpent Bearer.

  • Serpens Caput, the Serpent’s Head.

  • Serpens Cauda, the Serpent’s Tail.

• Generally speaking, either by ancient Greek astronomers or by astronomers of later civilizations, the brighter stars in a constellation were given a Greek letter.

  • The brightest star in each constellation was designated as alpha, the first letter of the Greek alphabet. Beta, the second Greek letter, was the next brightest star, and so on until omega, the last letter of the 24-character Greek alphabet.

• Magnitude: It is a measure of a star’s brightness.

• Light Years: The distances to the stars and other objects beyond the planets of our solar system.

• RA: The position of a star measured in the east–west direction in the sky.

• Dec: The position of the star measured in the north–south direction on the sky.

• North Celestial Pole (NCP): The place to which the axis of Earth points in the north direction.

• South Celestial Pole (SCP): The place to which the axis of Earth points in the south direction.

• The imaginary lines of equal RA run through the NCP and SCP as semi circles centered on the center of Earth.

Newton’s Concept of Gravity

• Why Earth orbits the Moon, the Moon orbits the Sun, the Sun orbits the Milky Way's center, and why numerous other objects orbit various other objects in space.

• Why a planet or star is spherical.

• Why might gas and dust in space collide together to form new stars?

Einstein's Theory of Gravity

• Why do stars visible near the Sun during a total eclipse appear slightly out of place?

• Why are there black holes?

• Why is gravitational lensing discovered when we observe deep space?

• Why does Earth drag warped space and time around with it as it rotates, an effect that scientists have confirmed using satellites orbiting Earth.

• How two black holes colliding causes gravitational waves that cause disturbances billions of light-years away.