Caldwell 40

Hubble’s Wide Field Camera 3 helped astronomers better understand the cores of galaxies like Caldwell 40.

Distance

70 million light-years

Apparent Magnitude

10.6

constellation

Leo

object type

Spiral Galaxy

Caldwell 40
This structure is a densely packed region of stars that encompasses the heart of a spiral galaxy. Most galactic bulges host supermassive black holes. The visible, ultraviolet, and infrared observations used to create this image of Caldwell 40 were made using Hubble’s Wide Field Camera 3.
NASA, ESA, and P. Erwin (Max Planck Institute for Extraterrestrial Physics); Processing: Gladys Kober (NASA/Catholic University of America)

Galaxies consist of a number of different structures, and the particulars of these structures drive the evolution of a given galaxy. One such structure in spiral galaxies like Caldwell 40 (or NGC 3626) is the galactic bulge. This structure is a densely packed region of stars that encompasses the heart of a spiral galaxy. Most galactic bulges host supermassive black holes, with the masses of the black hole and the bulge typically linked (bigger bulges harbor more monstrous black holes).

The two main types of galactic bulges are “classic bulges,” which develop after a merger with another galaxy, and “pseudobulges,” which form out of material from the galaxy’s own outer region. Recent studies suggest that “composite bulges,” which are formed by a combination of these two processes, might be common. The visible, ultraviolet, and infrared observations used to create this image of Caldwell 40 were made using Hubble’s Wide Field Camera 3 to help astronomers better understand the prevalence of “composite bulges” in the universe.

Caldwell 40 was discovered by astronomer William Herschel in 1784. It is located 70 million light-years from Earth in the constellation Leo and has an apparent magnitude of 10.6. The best time of year to observe Caldwell 40 is during the Northern Hemisphere’s spring and the Southern Hemisphere’s autumn. It can be spotted using a small telescope, but the galaxy is one of the smallest Caldwell objects in the sky, so a larger telescope is best for observing the dim and compact galaxy.

Caldwell 40
This view of Caldwell 40 is a single image captured by Hubble’s Wide Field Camera 3 through one infrared filter (rather than a composite from multiple images and filters, as the above image is). It offers a wider field of view than does the image above.
NASA, ESA, and P. Erwin (Max Planck Institute for Extraterrestrial Physics); Processing: Gladys Kober (NASA/Catholic University of America)
Caldwell 40 (NGC 3626)
A ground-based image of Caldwell 40 (NGC 3626) from the Digitized Sky Survey (DSS) appears in the upper left. A yellow rectangle in that image shows the area imaged by Hubble’s Wide Field Camera 3 (WFC3) in infrared (IR) light on the right. A blue rectangle in the WFC3 IR image shows the field covered by the WFC3 image in the lower left, which combines observations taken in ultraviolet, visible, and infrared light.
Ground-based image: Digitized Sky Survey (DSS); Hubble images: NASA, ESA, and P. Erwin (Max Planck Institute for Extraterrestrial Physics); Processing: Gladys Kober (NASA/Catholic University of America)
Star chart for Caldwell 40
This star chart for Caldwell 40 represents the view from mid-northern latitudes for the given month and time.
Image courtesy of Stellarium
A finder chart for C40 for mid-southern latitudes, in the constellation Leo at 10:00 p.m. in April.
This star chart for Caldwell 40 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.

Galactic Bulge - A dense collection of stars at the center of a spiral galaxy, possibly hosting a supermassive black hole.

Spiral Galaxy - A galaxy characterized by its spiral structure, with star-filled arms that extend out from the center of the galaxy and host regions of star formation.

Supermassive Black Hole - A black hole millions or billions of times more massive than the Sun, typically residing at the center of a large galaxy.

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.

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