The density of stars from Gaia's Early Data Release 3
Data from more than 1.8 billion stars has been used to create this map of the entire sky. It shows the total density of stars observed by ESA's Gaia satellite and released as part of Gaia's Early Data Release 3 (Gaia EDR3).
Brighter regions indicate denser concentrations of stars, while darker regions correspond to patches of the sky where fewer stars are observed. In contrast to the brightness map in colour which is enhanced by the brightest and most massive stars, this view shows the distribution of all stars, including faint and distant ones.
The bright horizontal structure that dominates the image is the plane of the galaxy. It is a flattened disc that hosts most of our galaxy's stars. The bulge in the centre of the image is surrounding the centre of the galaxy.
The faint, elongated feature just visible below the Galactic centre and pointing in the downwards direction is the Sagittarius dwarf galaxy. This is a small satellite of the Milky Way that is leaving a stream of stars behind as an effect of our galaxy's gravitational pull. This faint feature is only visible in this view, and not in the all-sky map based on the luminosity of stars, which is dominated by brighter sources.
Darker regions across the Galactic plane correspond to foreground clouds of interstellar gas and dust, which absorb the light of more distant stars. Many of these clouds conceal stellar nurseries where new generations of stars are currently being born.
Dotted across the image are also many globular and open clusters, as well as entire galaxies beyond our own. The two bright objects in the lower right of the image are the Large and Small Magellanic Clouds, two dwarf galaxies orbiting the Milky Way. Other nearby galaxies are also visible, most notably the Milky Way's largest galactic neighbour the Andromeda galaxy (also known as M31), seen in the lower left of the image along with its satellite, the Triangulum galaxy (M33).
A number of artefacts are also visible on the image. These take the form of curved features. These features are not of astronomical origin but rather reflect Gaia's scanning procedure. They are much less pronounced than they were in previous data releases, and will fade even more as more data are gathered.
Gaia EDR3 was made public on 3 December 2020 and includes the position and brightness of more than 1.8 billion stars, the parallax and proper motion of almost 1.5 billion stars, and the colour of more than 1.5 billion stars. It also includes more than 1.6 million extragalactic sources.
A complementary image showing Gaia's map of the colour of the stars is available here.
Gaia's density of stars map is also available in equirectangular projection (suitable for full-dome presentations) here.
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