Small Magellanic Cloud

At a glance

Key points

• About 204,000 light-years away
• Linked to the LMC by a bridge of gas
• Visible without a telescope from the south

Torn by tides

Interaction with the LMC has drawn out a bridge of gas and stars between the two Clouds and stretched the SMC deep along our line of sight.

Where the distance ladder began

In 1912 Henrietta Swan Leavitt at Harvard College Observatory published the periods of 25 Cepheid variable stars in the SMC. Because they all lie at about the same distance, she could see that the brighter ones pulse more slowly. Once calibrated, that period–luminosity relation let astronomers measure the distances to other galaxies, and it still anchors the distance ladder used to measure how fast the universe is expanding.

Long-lived planet-forming discs

The young cluster NGC 346 has only about a tenth of the Sun's share of elements heavier than helium, close to conditions in the early universe. Models predicted that discs around young stars there should disperse within 2 to 3 million years. In December 2024 Webb spectra confirmed earlier Hubble hints that stars 20 to 30 million years old still have discs and are still feeding from them, which suggests planets in the young universe had longer to form than expected.

One galaxy or two?

Because we see the SMC end-on, its true shape is hard to read. A 2024 study of its gas and young stars argued that it may be two star-forming systems with different chemistry, overlapping on the sky but about 16,000 light-years apart along our line of sight. A 2025 Gaia study of about 7,000 massive stars found no sign of rotation, with stars on opposite sides moving toward and away from the LMC: a hint that the larger Cloud is pulling it apart. Both results are new and debated, and either would change estimates of the SMC's mass.

Observing it

The SMC is an easy naked-eye patch from dark southern skies, smaller and fainter than the LMC, in the constellation Tucana. Beside it on the sky sits 47 Tucanae, one of the brightest globular clusters, which belongs to the Milky Way and is far closer. The SMC is highest in the evening from about October to December and never rises north of about 17°N.

Missions

1. 1990–

   Hubble Space Telescope

   NASA / ESAActive

   Ultraviolet to near-infrared imaging from low Earth orbit.

   Mission page (opens in a new tab)

2. 2013–2025

   Gaia

   ESACompleted

   Mapped about two billion stars; Data Release 4 is scheduled for 2 Dec 2026.

   Mission page (opens in a new tab)

Related entries

• Large Magellanic CloudThe Milky Way's biggest satellite
• The Milky WayOur barred spiral home galaxy

Sources

1. Murray et al. 2024, ApJ 962:120, the SMC as two superimposed systems (arXiv) (opens in a new tab)
2. Nagoya University (11 Apr 2025): the SMC may be being torn apart (opens in a new tab)
3. Graczyk et al. 2020, ApJ 904:13 (arXiv) (opens in a new tab)
4. SIMBAD (CDS): Small Magellanic Cloud (opens in a new tab)
5. ESA: ESA/Webb weic2430: planet-forming discs in NGC 346 (opens in a new tab)
6. Leavitt & Pickering 1912, Harvard College Observatory Circular 173 (ADS) (opens in a new tab)

Last reviewed 10 Oct 2026 against these sources. Built from public NASA, ESA and JPL data; not affiliated with or endorsed by any agency.