Home >> Science & Nature >> Astronomy

How to Identify the Bodies in Space That Emit Light

Every object that has a temperature above absolute zero emits electromagnetic radiation, or light. In space, countless celestial objects emit light ranging from low-energy radio waves to high-energy gamma waves. Visible light is the part of the electromagnetic spectrum, between these extremes, to which the human eye is sensitive. The sun, like every star, emits light in the characteristic pattern of its spectral class. Celestial objects, such as galaxies, star clusters and nebulae, are located at vast distances from Earth, and most are too dim to be seen by the unaided eye.

Things You'll Need

Binoculars or telescope
Monthly star chart or sky map

Instructions

Planet Saturn
- 1
  
  The closeup view of Saturn is different than the view from Earth.
  
  Find the curved line on your star chart labeled "ecliptic," or "zodiac," the apparent path that the planets take across the sky. When Saturn is above your horizon at night, it will appear as a bright yellow star somewhere on the ecliptic. The elevation of the ecliptic above the horizon changes with the seasons, so use the bright stars and recognizable star patterns on your star chart as guides to its position on the sky.
- 2
  Train your binoculars on Saturn. Note that at low magnification the planet has an oval appearance. The rings can be seen separated from the planet at a magnification of 25 times or greater.
- 3
  Study the region of space near the planet. With patience and good viewing conditions, you may be able to discern one or more of Saturn's moons, which appear as delicate pinpoints of light.
Emission Nebula M42 in Orion
- 4
  Find the constellation Orion the Hunter using your star chart. Orion is a prominent winter constellation that looks like a large rectangle, pinched near the center by a line of three stars (Orion's belt), with four bright stars marking the corners.
- 5
  Train your binoculars at the center of the rectangle. Note another line of three stars extending to the south (Orion's sword), at right angles to the belt, and the hazy patch of light surrounding the middle star. M42 is a vast, star-forming region, located about 1,500 light years from Earth. This famous nebula is composed of gas and dust lit by intense radiation from newborn stars contained within it.
- 6
  Note the bright glow at the heart of the nebula. This glow comes mainly from a group of four, young, super-hot stars, known as the trapezium.
Spiral Galaxy M31 in Andromeda
- 7
  Locate the constellation Cassiopeia in the fall or winter sky using your star chart. Cassiopeia is near the north celestial pole and has an unmistakable "W" shape with five bright stars marking the outline.
- 8
  Identify the two westernmost stars of the "W." Extend the line formed by these stars a distance of five lengths toward the southeast.
- 9
  Scan the sky at this position with your binoculars, using a circular scan pattern, until you see a dim patch of white light. M31 is a large spiral galaxy, similar to the Milky Way, located about two-million light years from Earth.

Astronomy