The James Webb Space Telescope’s infrared view has transformed our view of a large barred spiral galaxy, revealing its skeleton of dust illuminated by the glow of young stars.
Visible-light images of NGC 1559, such as those taken by the Hubble Space Telescope, show a glowing vortex of light with bright, young star clusters spread across spiral arms with orbits of black dust.
The JWST has now seen beyond the glare and its infrared vision reveals the bowels of the Milky Way. The JWST’s Near-Infrared Camera (NIRCam) sees starlight filtered through the obscuring dust, as well as the glow of ionized hydrogen gas in star-forming regions. Meanwhile, the space telescope’s Mid-Infrared Instrument (MIRI) was able to directly observe the dust and pick up clouds of small particles produced by previous generations of dust. stars and drawing the spiral structure of NGC 1559.
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The JWST’s new image of NGC 1559 is not only exquisite in its beauty. It is also scientifically valuable, produced as part of the PHANGS (Physics at High Angular Resolution in Near GalaxieS) project to better understand how stars are born, how they live and how they die in various galaxies in the universe. PHANGS also wants to know more about the interactions between these stars and the gas and dust clouds found in a galaxy, and how these together influence the overall, large-scale structure of a galaxy. The project, led by an international team of astronomers, will map these galaxies across the entire electromagnetic spectrum, using not only the JWST but also a wealth of other powerful observatories. The list includes the Hubble Space Telescopethe Atacama large millimeter/submillimeter array (ALMA) and the Atacama Compact Array (ACA) in Chile, the Very large series (VLA) of radio telescopes in the United States, the MoreKAT radio telescope in South Africa and the Northern extended millimeter array (NOEMA) in France.
However, NGC 1559 stands out among the galaxies observed by PHANGS because it is located on a lonely patch of ground. room. It has no close galactic neighbors and is located in the southern hemisphere constellation Reticulum. NGC 1559 also hosts four supernovas discovered in the last forty years. The first three – SN 1984J, SN 1986L and SN 2005df – were all discovered by Australian amateur astronomer Robert Evans. That was back when amateur supernova patrols found the bulk of exploding stars, before professional automated telescopic surveys came online. An example of this is the fourth supernova observed in NGC 1559, SN 2009ib, which was discovered by CHASE, the Chilean Automatic Supernova Search of the Cerro Tololo Inter-American Observatory.
The last two supernovae – SN 2005df and SN 2009ib – are particularly important because they allowed astronomers to calculate the distance to NGC 1559 and thus the galaxy’s place on the cosmic distance ladder. This could help calculate the expansion rate of the universe.
SN 2009ib is what is known as a Type-II-P supernova. It represents the cataclysmic explosion of a massive star, but its light curve – how the supernova’s brightness changed time – remained flat or flat for 130 days after peak brightness was reached. The plateau is caused by the hydrogen gas in the supernova debris turning opaque as it is ionized by the supernova’s shock wave. Special features of these plateau supernovae make it possible to measure the distance of each supernova (and therefore of galaxies) to us. In 2009, astronomers led by Katalin Takáts of the Universidad Andrés Bello in Chile used SN 2009ib to calculate the distance to NGC 1559, yielding an answer of 19.8 mega.parsecor 64.57 million light years.
Meanwhile, SN 2005df is a type 1a supernova, which causes the destruction of a white dwarf. Type 1a supernovae have a standardizable brightness. The further away they are, the weaker they seem, but if we know what they are true, they can be standardized Brightness that is, we can calculate exactly how far along they have to be to look as weak as they do. Therefore, they can be used to determine cosmic distances. For this reason they are also considered ‘standard candles’. In 2019, astronomers led by Caroline Huang and Adam Riess of Johns Hopkins University used SN 2005df, in combination with two other types of standard candles, Cepheid and Mira variable stars, to confirm the distance to NGC 1559. a response of 19.8 megaparsecs, which is in excellent agreement with the previous measurement of SN 2009ib.
Partly based on this distance measurement, Huang and Riess’ team were able to calibrate the brightness of Type 1a supernovae in more distant galaxies to more accurately measure their distances. They then compared these distances with their own distances redshift to calculate the Hubble constanta benchmark for the the expansion of the universe73.3 kilometers per second per megaparsec.
This calculation is interesting; it has added more fuel to the cosmological paradox known as ‘Hubble tension“in which measurements of the expansion rate using Type 1a supernovae give a different answer to measurements of the expansion rate based on the study of the cosmic microwave backgroundwhich instead gives a Hubble constant of 67.8 kilometers per second per megaparsec.
It remains a mystery why these measurements are different when they should actually be the same.
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NGC 1559 has another striking feature. In 2023, Taiwanese astronomers used data from NASA‘S Chandra X-ray Observatory to find eight ultra-luminous X-ray sources (ULXs) in NGC 1559. ULXs are mysterious objects that release floods of extremely high-energy X-rays in greater quantities than can be explained by known processes in stars. It is suspected that these phenomena involve compact objects such as neutron stars And black holes.
One of the eight ULXs in NGC 1559 stood out above the others. The X-rays, referred to as X-24, vary with a periodicity of 7,500 seconds (two hours and five minutes). This periodicity is suspected to be related to the orbital period of an object, probably a star, moving around a stellar-mass black hole with a gravitational force strong enough to tear and eat material from the orbiting object. If so, this would be the first compact binary ULX to be discovered.
For a loosely wound but beautiful spiral galaxy located in the middle of nowhere with few other galaxies nearby, NGC 1559 manages to occupy an important place for astronomers in the study of stars, galaxies, and the universe as a whole.