The objects you can see in the sky with your naked eye are mostly stars and sometimes planets, but with binoculars or a telescope, many other types of objects become visible. That being said, if you just have a small, basic telescope, don’t expect to see a lot of spectacular detail and colors—most of the published photographs of beautiful, multicolored deep-sky objects were taken with the Hubble Space Telescope or by professional observatories.
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Stars are large balls of burning gases, like our Sun, for example. They can have different colors depending on their temperature (hotter stars are whitish-blue, cooler stars are red, and intermediate stars can be orange or yellow).
- What you need to see them: The brightest stars can be seen with the naked eye even in urban areas.
- Examples to look for: If you look carefully, you can see the color variations between different stars. For example, Betelgeuse (the left shoulder of Orion) looks orange-red, whereas Rigel (the left foot of Orion) is much hotter and looks blue.
Double stars are pairs of stars that appear to be very close together. Sometimes this is an illusion, and one star is actually hundreds of light-years behind the other. Other times they are binary stars that orbit around each other.
- What you need to see them: Some double stars can be distinguished with the naked eye, but most look like a single star until you use binoculars or a telescope.
- Examples to look for: The middle star of the Big Dipper’s handle is actually a double star: Mizar and Alcor can be distinguished without a telescope on a very clear night. With a small telescope, you’ll see that Rigel in Orion is also a double star.
Open clusters are loose aggregations of stars that look like several individual stars in close proximity.
- What you need to see them: You don’t need any tools to see many open clusters, but you can see more of their stars with binoculars.
- Examples to look for: The Pleiades (the Seven Sisters), shown above, are an open cluster with at least six stars visible to the naked eye.
Globular clusters are aggregations of hundreds of thousands of stars so tightly concentrated that they look like a continuous patch of light.
- What you need to see them: You’ll need binoculars or a small telescope to get a good look.
- Examples to look for: M13, in the constellation Hercules, is the best-known globular cluster.
Planetary nebulae are glowing regions of gas that have been ejected from a dying star. They look like faint, irregularly shaped, fuzzy smudges, some of which are ring-shaped.
- What you need to see them: You’ll need a small telescope to view most nebulae. The bigger the telescope, the more detail you’ll be able to see.
- Examples to look for: The Ring Nebula in the constellation Lyra is probably the best known planetary nebula. You can spot it most easily in the summer.
Diffuse nebulae are large regions of gas where new stars are in the process of forming. Like planetary nebulae, they look like fuzzy splotches.
- What you need to see them: Use a small telescope.
- Examples to look for: The Orion Nebula in Orion’s belt is easy to spot.
A galaxy is a system of billions of stars spinning around a glactic center (where there is often a black hole). Through a small telescope, most galaxies look like fuzzy circles or ovals (or fuzzy lines if seen edge-on), but some have visible spirals.
- What you need to see them: A small handful of galaxies can be seen with the naked eye and binoculars, but to see their structure you’ll need a telescope—the bigger, the better.
- Examples to look for: On a clear, moonless night, the Andromeda Galaxy (also called M31) can be seen with the naked eye. With a telescope, you’ll get an edge-on view of this spiral galaxy.
The Milky Way
The Milky Way is our own spiral galaxy—we are located in a spiral arm about two-thirds of the way out from the galactic center. The plane of the galaxy’s disk looks like a bright band across the sky, stretching from horizon to horizon. This part of the Milky Way looks brightest because it’s where most of the galaxy’s stars are located.
- What you need to see it: On a clear night away from light pollution, the Milky Way is easily visible to the naked eye.
- Examples to look for: The bright band of the Milky Way passes through the constellations Cassiopeia and Crux (the Southern Cross), and is brightest in the direction of Sagittarius (toward the galactic center).