Brown Dwarfs
Overview
In astronomy, there are dwarf stars, dwarf novae, and even dwarf galaxies. Substellar objects, like brown dwarfs, cover objects too small the be stars and too large to be planets. Planets are believed to range up to 13 Jupiter masses, while brown dwarfs range from there up to about 80 Jupiter masses, where there is enough mass to stimulate fusion.
Discovery
While brown dwarfs had been theorized starting in the 1960s, it took roughly thirty years to get conclusive observation of one. These dim objects emit most of their light in the infrared, and so infrared detectors were needed to see them. With the advent of 2MASS in 1997, the floodgates opened and many such objects were catalogued. Today, we know of thousands of such objects.
The objects in this catalog use telescopes like Pan-STARRS, 2MASS, WISE, and Gaia.
Classification
In the transition from star to brown dwarf, we have the M stars—the coolest stars. Some astronomers consider the less massive of these to be brown dwarfs, or red dwarfs. These are the M type dwarfs. Cooler objects are given the spectral class L. L type objects have distinct absorption bands in their spectra. Defined by their spectra in this way, the L-type objects can include very low mass stars as well as brown dwarfs. T type objects are dimmer and more magenta colored and exhibit different spectral features. Established in 2009, the coolest known objects were called Y type objects. These are around 500 Kelvin
Representing Brown Dwarfs
Note
None of these objects are visible to the eye, so we represent these objects conceptually with oversized points, tinted according to their type: L dwarfs, T dwarfs, and Y dwarfs. Their brightness (size) is grossly exaggerated so we can examine them.
We represent these data by oversized points colored according to their spectral type. These objects are incredibly faint, so we need to exaggerate their size in order to see them. We color them according to spectral type:
L type: orange-red
T type: red-magenta
Y type: violet
Brown dwarfs as seen from the night sky looking toward the constellation Orion. None of these objects are visible with the eye. There is a variety of colors corresponding to each object’s spectral type: red-orange for L type, red-magenta for T type, and violet for Y type.
Brown dwarfs in the nighttime sky. Here, we’re looking toward the constellations Scorpius and Sagittarius. The size of the brown dwarf point in the sky is a function of how distant the object is to you—the larger the point, the closer it is.
Distribution in the Solar Neighborhood
Because brown dwarfs are extremely dim objects, we cannot detect these objects to great distances. In many ways, it is still a research frontier where new objects are being discovered and new telescopes tailored to detect these objects are coming online.
Because these objects are difficult to detect, we only see them very close to the sun.
Brown dwarfs, in red, distributed around the Sun. The green object is a 160-light-year diameter sphere centered on the Sun. The brown dwarfs are not distributed evenly around the Sun, rather, they are easier to observe off the plane of the Milky Way, so we see more of them above and below the plane of the Galaxy.
Profiles
Dossier
Census: |
2,203 brown dwarfs |
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Asset File: |
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OpenSpace Version: |
1 |
Reference: |
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Prepared by: |
Brian Abbott, Zack Reeves, Jackie Faherty (AMNH) |
Source Version: |
7.05 |
License: |