What Are Quasars?

• Quasars (short for quasi-stellar objects) are extremely bright and distant objects in the Universe.

• They look like stars in telescopes but are actually the active centers of very young galaxies.

• A quasar is powered by a supermassive black hole at the center of a galaxy.

• As matter falls into the black hole, it gets heated up and releases huge amounts of energy, especially in radio, visible, and X-ray wavelengths.

• Quasars are among the most luminous and energetic objects in the Universe.

• They are so far away that their light has taken billions of years to reach us — we see them as they were in the early Universe.

• Quasars provide strong evidence for the expansion of the Universe and help us study its early stages.

Summary Points:

• Very distant and bright

• Powered by supermassive black holes

• Look like stars but are not

• Found in early galaxies

• Key evidence for the Big Bang and cosmic evolution

What is Galaxy Starlight?

• “Galaxy starlight” means the light coming from the stars in a galaxy.

• A galaxy is a huge collection of billions of stars, gas, and dust, all held together by gravity.

• The combined light from all the stars in that galaxy is what we call galaxy starlight.

• This light travels through space and can be observed from Earth using telescopes.

• Astronomers analyze the spectrum of this starlight to:

  • Determine the elements present in the stars.

  • Measure the redshift, which tells us how fast the galaxy is moving away.

  • Estimate the galaxy’s distance and age.