Caldwell 20

C20's shape resembles the North American continent, giving it the nickname of the North America Nebula.

Distance

1,800 light-years

Apparent Magnitude

5.0

constellation

Cygnus

object type

Emission Nebula

Caldwell 20
While the spiral feature in the upper portion of this Hubble image may resemble the arm of a galaxy or the heart of a cosmic storm, it is actually a small portion of Caldwell 20 (NGC 7000), or the North America Nebula.
NASA, ESA, and K. Stapelfeldt (Jet Propulsion Laboratory); Processing: Gladys Kober (NASA/Catholic University of America)

Discovered by William Herschel in 1786 and nicknamed the North America Nebula because its shape resembles the continent, C20 is located roughly 1,800 light-years from Earth and occupies a space in the constellation Cygnus that appears more than three times larger than the full moon. However, despite an apparent magnitude of 5, the nebula does not appear very bright against the starry Milky Way. Binoculars or a small telescope will reveal it as a subtle brightening against its galactic backdrop. Observers can best view C20 in September.

Caldwell 20 - inset 1
The Digitized Sky Survey (DSS) ground-based image of Caldwell 20 (NGC 7000) in the upper right captures a wide view of the nebula, illustrating why the object is known as the North America Nebula. The white outline shows the location of Hubble’s observation taken with its Wide Field and Planetary Camera 2 (WFPC2), which captures a small region of the nebula located roughly where northeastern Texas might be.
Ground-based image: Digitized Sky Survey; Hubble image: NASA, ESA, and K. Stapelfeldt (Jet Propulsion Laboratory); Processing: Gladys Kober (NASA/Catholic University of America)

Caldwell 20 is a stunning example of an emission nebula. The clouds of gas that make up the nebula are being ionized by a nearby star, causing the gas to glow as it emits energy. Colors emitted by emission nebulae depend on the chemical composition of the region. The reddish color that is characteristic of hydrogen and dominates C20 can be picked up by sensitive cameras.

This image of Caldwell 20, taken with Hubble’s Wide Field and Planetary Camera 2, is a part of a survey of T Tauri stars in nearby star-forming regions. T Tauri stars are young stars that vary in brightness over time. One reason this kind of star is important to astronomers is because a large portion of T Tauri stars have been found to host circumstellar disks. These disks of gas and dust may one day become fully fledged solar systems.

Star chart for Caldwell 20
This star chart for Caldwell 20 represents the view from mid-northern latitudes for the given month and time.
Image courtesy of Stellarium
Line drawings of constellations pinpoint the location of Caldwell 20.
This star chart for Caldwell 20 represents the view from mid-southern latitudes for the given month and time.
Image courtesy of Stellarium

Glossary

Apparent Magnitude - The brightness of an astronomical object as seen from Earth, influenced by the object's distance from Earth, its absolute magnitude, and even gas and dust that lie between the object and Earth.

Emission Nebula - A cloud of ionized gas that emits energy at wavelengths across the electromagnetic spectrum, causing it to glow with vibrant colors.

Nebula - An interstellar cloud of dust and gas; either a location where new stars are being forged or a cloud of material ejected into space by a dying star.

T Tauri Star - A young star that has not yet reached temperatures high enough to ignite nuclear fusion, and exhibits variations in its brightness.

Explore Hubble's Caldwell Catalog

The following pages contain some of Hubble’s best images of Caldwell objects.

Stars with four diffraction spikes dot the scene against a black backdrop.

Caldwell 1

Also known as NGC 188, this group of stars formed from a large cloud of gas making the stars roughly…

Red cloud of dust with a bright white star in the center of it. Lots of reddish and orangish stars in the background.

Caldwell 2

This shell of gas is expanding outward, away from the dying star within.

Large grouping of bright white, blue and red stars. Lightly colored blue dust surrounds the stars.

Caldwell 3

This barred spiral galaxy was first spotted by British astronomer William Herschel in April 1793 in the constellation Draco.