# IC 1101 confirmed as largest known galaxy

> Live situation record from CLSTR: https://clstr.news/situations/ic-1101-confirmed-as-largest-galaxy
> Updated: 2026-08-24T11:00:00.000Z. Sources: 6. Developments: 3.

Astronomers led by Carlos Marrero-de-la-Rosa of the Instituto de Astrofísica de Canarias have confirmed IC 1101 as the largest known galaxy. Using ultra-deep imaging from the 2.5-meter Isaac Newton Telescope at the Roque de los Muchachos Observatory, the team mapped the galaxy’s outermost light to establish a diameter of approximately 520 kiloparsecs (about 1.7 million light-years).

To achieve this measurement, researchers had to meticulously model and subtract light interference from the atmosphere, the telescope, and more than 250 foreground stars. This process allowed them to identify the main stellar area extending roughly 260 kiloparsecs from the center. The resulting diameter is approximately 17 to 20 times wider than the Milky Way’s stellar disk; if placed in our local neighborhood, IC 1101 would nearly span the distance between the Milky Way and the Andromeda galaxy.

Located at the center of the Abell 2029 galaxy cluster, IC 1101 has a stellar mass of about 3.4 trillion solar masses. The study noted faint asymmetric structures beyond the main edge, indicating the galaxy is still growing through the ongoing accretion of smaller galaxies. Additionally, the galaxy’s core hosts an ultra-massive black hole estimated to be several hundred billion solar masses, making it one of the largest known black holes.

## Timeline

### 2026-08-24: IC 1101 identified as the largest known galaxy with 1.7 million light-year diameter

Astronomers using the Isaac Newton Telescope have confirmed IC 1101 as the largest known galaxy, with a diameter of 1.7 million light-years, significantly exceeding the size of the Milky Way.

2 sources. https://clstr.news/cluster/ic-1101-identified-as-the-largest-known-galaxy-with-17-million-light-year-diameter

### 2026-08-06: IC 1101 confirmed as the largest known galaxy

Astronomers led by Carlos Marrero‑de la Rosa measured IC 1101’s diameter at 520 kpc (≈1.7 million ly), confirming it as the largest known galaxy, centered in the Abell 2029 supercluster and hosting an ultra‑mas

2 sources. https://clstr.news/cluster/ic-1101-confirmed-as-the-largest-known-galaxy

### 2026-07-31: IC 1101 Confirmed as Largest Known Galaxy at 1.7 Million Light‑Years Across

Astronomers using the Isaac Newton Telescope measured IC 1101’s diameter at about 1.7 million light‑years, confirming it as the Universe’s largest known galaxy.

2 sources. https://clstr.news/cluster/ic-1101-confirmed-as-largest-known-galaxy-at-17-million-lightyears-across

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Cite as: IC 1101 confirmed as largest known galaxy. CLSTR, https://clstr.news/situations/ic-1101-confirmed-as-largest-galaxy