S Normae Cluster (NGC 6087)

An open cluster in Norma, about 3,100 light-years away, named for the variable star S Normae among its stars. From Guyana it climbs only 25° above the southern horizon.

Open cluster in Norma. Magnitude 5.4.

Can you see it from Guyana?

From Georgetown (6.8° N) it climbs to 25° above the southern horizon at its highest; from Lethem (3.4° N), to 29° above the southern horizon. It is highest at midnight on the night of 25 May, in the middle of its season. The page works out tonight's rise, highest point and set for both towns in Guyana time (UTC-4), and where the Moon is.

What you'll see

• Your eyes: Visible to the eye only from a dark site, as a hazy knot of stars; lost in city skies. It lies 11.6° north of Atria.
• 10x50 binoculars: Resolves into dozens of stars.
• A small telescope (80 to 100 mm): A loose group of bright stars at low power, S Normae among them.
• A camera: Tiny on camera: it needs 2,000 mm or more of focal length on a tracking mount.

How big, how bright, how far

• Size on the sky: 10.2′, 33% of the Moon's width (the Moon is about 31′ wide).
• Brightness: magnitude 5.4. Fainter than Georgetown's faintest stars (4.3) but brighter than Lethem's (6.0).
• Distance: 3,060 light-years. The light reaching your eye left it about 3,060 years ago.
• True size: 9.1 light-years across its catalogued outline; light crosses it in 9.1 years.

Apparent size from OpenNGC (Mattia Verga), CC-BY-SA-4.0.

What it is made of

Type

Open cluster

Mass

About 1,100 times the Sun's mass, in its stars

Age

About 91 million years (range 56 million years to 150 million years)

What is in it, not measured:

• Stars born together: from one cloud of gas, at one time

How we know: Distance from Gaia parallaxes of its stars: Hunt & Reffert 2024, A&A 686, A42 (Gaia DR3 cluster catalogue, VizieR J/A+A/686/A42), retrieved 2026-10-21: NGC 6087 938 pc; statistical 3,056-3,064 ly (16th-84th percentile); Gaia DR3 parallax zero-point systematics (about 0.02 mas) add about 2%. True size: the apparent size times the distance (apparent size: OpenNGC (Mattia Verga, CC BY-SA 4.0), commit 4e2398a2). Mass: Hunt & Reffert 2024, A&A 686, A42 (Gaia DR3 cluster catalogue, VizieR J/A+A/686/A42), retrieved 2026-10-21, NGC 6087: total 1,100 ± 78 Suns.

More deep-sky objects: NGC 6025 (Open Cluster) · NGC 6397 (Globular Cluster) · NGC 6231 (Northern Jewel Box) · NGC 6124 (Open Cluster) · NGC 6388 (Globular Cluster) · NGC 6281 (Open Cluster)

What's in the sky tonight · Sun/Moon Times & Dark Window

Tools · Learn