The James Webb Space Telescope (JWST) has recently provided us with a breathtaking view of the spiral galaxy NGC 1559. This new image, captured by the telescope’s infrared vision, reveals the galaxy’s inner structure and offers valuable scientific insights into the birth, life, and death of stars.
NGC 1559, located in the southern hemisphere constellation of Reticulum, stands out among the galaxies observed by the PHANGS project due to its isolated position. Unlike other galaxies, NGC 1559 does not have any close galactic neighbors. This uniqueness makes it an ideal subject for studying the interplay between stars and the gas and dust clouds within a galaxy.
The JWST’s Near-Infrared Camera (NIRCam) and Mid-Infrared Instrument (MIRI) played crucial roles in capturing this stunning image. NIRCam filtered starlight through the dust, allowing us to see the glow of ionized hydrogen gas in star-forming regions. On the other hand, MIRI directly observed the dust, revealing intricate clouds of tiny particulate matter that trace out NGC 1559’s spiral structure.
But this image is not just a feast for the eyes; it also holds significant scientific value. The PHANGS project aims to understand the processes of star formation, evolution, and their impact on a galaxy’s overall structure. By mapping galaxies across the electromagnetic spectrum using various observatories, including the JWST, Hubble Space Telescope, ALMA, VLA, MeerKAT, and NOEMA, astronomers hope to gain a comprehensive understanding of these cosmic phenomena.
NGC 1559 has also played a crucial role in measuring the expansion rate of the universe. Over the past 40 years, four supernovas have been discovered within this galaxy. The first three were found by Australian amateur astronomer Robert Evans before automated telescopic surveys became prevalent. The fourth supernova, SN 2009ib, was discovered by CHASE, the Chilean Automatic Supernova Search. These supernovas, particularly SN 2005df and SN 2009ib, allowed astronomers to calculate the distance to NGC 1559 and its position on the cosmic distance ladder.
SN 2009ib, a Type-II-P supernova, provided valuable data for calculating the galaxy’s distance. Its light curve, which measures the brightness of the supernova over time, remained flat for 130 days after reaching peak brightness. This plateau is caused by ionized hydrogen gas in the supernova’s debris, allowing astronomers to measure the distance to NGC 1559 accurately.
SN 2005df, a Type 1a supernova, is considered a “standard candle” due to its standardizable brightness. By comparing its brightness to its true luminosity, astronomers can determine its distance from Earth. Together with other standard candles like Cepheid and Mira-type variable stars, SN 2005df helped confirm the distance to NGC 1559.
These distance measurements were crucial for calibrating the brightnesses of Type 1a supernovas in galaxies farther away. By comparing these calibrated distances to redshift data, astronomers calculated the Hubble constant, a measure of the universe’s expansion rate. However, these measurements have added to the cosmological paradox known as “Hubble tension.” The expansion rate calculated using Type 1a supernovas differs from measurements based on the cosmic microwave background, leaving scientists puzzled as to why they don’t align.
NGC 1559 also holds another intriguing feature. In 2023, Taiwanese astronomers discovered eight ultra-luminous X-ray sources (ULXs) within the galaxy using NASA’s Chandra X-ray Observatory. ULXs emit extremely high-energy X-rays that cannot be explained by known stellar processes. These sources are believed to involve compact objects like neutron stars and black holes. Among the eight ULXs, one named X-24 stands out due to its periodic X-ray emission, indicating the presence of a compact binary system with a stellar-mass black hole.
NGC 1559, with its captivating beauty and scientific significance, continues to captivate astronomers. Despite its isolated location, this spiral galaxy provides valuable insights into the mysteries of the universe, from star formation to the expansion rate of our cosmos. As we delve deeper into NGC 1559’s secrets, we come closer to unraveling the enigmatic nature of galaxies and their place in the vast expanse of space.
