Preparing AstroBrain

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Sharpless 4

Set a site to see tonight's sky

When Sharpless 4 is up, how long it stays usable and when it is in season all depend on where you observe from. Set your site and this page adds tonight's answer and its year.

Set it on Tonight

The science

What you are looking at

In one sentence

Interstellar hydrogen ionised by the ultraviolet light of hot, young stars embedded in it.

Class explainer for H II region (SIMBAD classification).

The facts

Sharpless 4 is an emission nebula in Scorpius. SIMBAD gives its distance as 14.3 kpc — ≈ 46,600 ly, measured by its motion through the Galaxy from 1 measurement. The light reaching us from it now left it about 46,600 years ago, when early Homo sapiens lived through the ice ages. SIMBAD measures it at 3.3′ × 3.3′ on the sky — 11% of the full Moon's width. At that distance, that angle means it is roughly 45 light-years across. Framing uses its catalogue size instead: 5.0′.

Sources: AstroBrain catalogue; Sharpless S. 1959, ApJS 4, 257, via CDS/VizieR VII/20; CDS/SIMBAD astronomical database, Strasbourg (SIMBAD record SH 2-4 · distance from 2006ApJ...653.1226Q). Contains information from SIMBAD, which is made available here under the Open Database License (ODbL). Download the SIMBAD-derived data.

For scale

Angular size, as it would sit on your sky.

45 ly

across — 10× the distance from the Sun to its nearest neighbour star (4.37 ly).

The same patch of sky in visible light

Sky image
Observatory photos and open-licence sky surveys.
Credits on each image.

Neighbours in the sky

Sky maths: apparent positions with refraction, one-minute steps; usable = full astronomical dark, at least 30° up and clear of your skyline. Survey images: CDS, Strasbourg (DSS2 and other surveys). Science: SIMBAD. The hours, heights and Moon on this page use no weather forecast; the rank is this target’s place in the Targets list, whose score also counts the cloud forecast when there is one.

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