NGC 4559
Intermediate spiral galaxy in Coma Berenices with a luminous blue variable.
NGC 4559, also cataloged as Caldwell 36, is an intermediate spiral galaxy found in the constellation Coma Berenices. It features a faint inner ring structure. Its motion relative to the cosmic microwave background suggests a Hubble distance of about 16.17 megaparsecs, but 26 measurements not based on redshift place it much closer, at roughly 7.53 megaparsecs. German-British astronomer William Herschel discovered it on April 11, 1785. The galaxy belongs to the Coma I Group.
One supernova, SN 1941A, has been observed in NGC 4559. It was a Type II-L event with a magnitude of 13.2, discovered by Rebecca Jones on February 24, 1941. Later checks of earlier photographs showed it had been visible since February 5, 1941.
The galaxy also hosts a luminous blue variable known as AT2016blu (also called PSNJ12355230+2755559 or NGC4559OT). The Lick Observatory Supernova Search found it on January 11, 2012. This star has produced repeated supernova-like outbursts: first when discovered, and again in 2014, 2016, 2017, 2018, 2019, 2020, 2021, 2022, 2024, 2025, and 2026.
Quick Facts
- Epoch
- J2000
- Ra
- 12 · 35 · 57.6285
- Dec
- +27 · 57 · 35.851
- Dist Ly
- 7.530 ± 0.483 Mpcned
- Z
- 0.002715 · 0.000002ned
- H Radial V
- 814 ± 1 km/s
- Appmag V
- 10.4
- Constellation Name
- Coma Berenices
Facts from the source article.
Lore & Background
NGC 4559 was discovered by German-British astronomer William Herschel on 11 April 1785. Its distance is uncertain: the velocity with respect to the cosmic microwave background gives a Hubble distance of 16.17 ± 1.17 Mpc, while 26 non-redshift measurements yield a much closer distance of 7.530 ± 0.483 Mpc. The galaxy belongs to the Coma I Group. One supernova has been recorded in NGC 4559: SN 1941A, a Type II-L event of magnitude 13.2, discovered by Rebecca Jones on 24 February 1941; subsequent examination of earlier photographs showed it had been visible since 5 February 1941. The galaxy also hosts the luminous blue variable AT2016blu (also known as PSNJ12355230+2755559 or NGC4559OT), discovered by the Lick Observatory Supernova Search on 11 January 2012. This object experiences repeated supernova-like outbursts, first when discovered, and then again in 2014, 2016, 2017, 2018, 2019, 2020, 2021, 2022, 2024, 2025, and 2026.
Reader's Guide
NGC 4559 is significant as a member of the Coma I Group, providing a nearby laboratory for studying intermediate spiral galaxies with weak inner ring structures. Its distance discrepancy—between the Hubble flow value and closer non-redshift measurements—highlights ongoing challenges in extragalactic distance determination. The galaxy's supernova SN 1941A, discovered by Rebecca Jones, is a historical Type II-L event that was later found to have been active weeks before its official detection. More notably, the luminous blue variable AT2016blu has drawn attention for its repeated, nearly annual supernova-like outbursts spanning over a decade, making it a rare and well-monitored example of such stellar instability. This recurring behavior offers astronomers a unique opportunity to study the evolution of massive stars in real time. The galaxy's legacy lies in its combination of classic spiral structure, a historical supernova, and a persistently erupting variable star that continues to be observed.
Did You Know?
- NGC 4559 was discovered by William Herschel on 11 April 1785.
- The galaxy hosts the luminous blue variable AT2016blu, which has outbursts recorded in 2012, 2014, 2016, 2017, 2018, 2019, 2020, 2021, 2022, 2024, 2025, and 2026.
- SN 1941A, a Type II-L supernova in NGC 4559, was discovered by Rebecca Jones on 24 February 1941 and was later found to have been visible since 5 February 1941.
- NGC 4559 is a member of the Coma I Group.
More in Galaxy Clusters and Groups, Part 4 1-24
Spotted an error? Know more?
Reader corrections go straight into our review queue. Suggest an edit · How this site is sourced