In the immense canvas of the cosmos, every point of light, every distant galaxy, contains fundamental clues to understand the laws that govern our universe. Recently, the Space Telescope NASA/ESA Hubble once again caught the attention of the scientific world with the image of a weakly-barred spiral galaxy, Mrk 1337, located about 120 million light years from Earth, in the constellation of the Virgin. This observation, apparently a routine snapshot of deep space, is actually a crucial step in one of the greatest puzzles of modern cosmology: accurate determination of the rate of expansion of the universe. The Wide Field Room 3 hubble, with its ability to capture images in a wide range of wavelengths – from ultraviolet to visible and infrared – has produced an image rich in details that, although fascinating in itself, serves a much deeper scientific purpose. Mrk 1337, with its spiral arms radiating from a central bar of gases and stars, is a structure not rare in the universe; our Milky Way itself is a bare spiral galaxy. However, its position and its characteristics make it a “standard candle” or an ideal reference point to calibrate cosmic distances. These observations are part of a scientific campaign aimed at improving our understanding of how quickly the universe is expanding, a research field that has earned the Nobel Prize for Physics in 2011 to Adam Riess, along with Saul Perlmutter and Brian Schmidt, for their discovery of the accelerated expansion of the Universe. This article aims to deepen not only the importance of Mrk 1337, but to explore the wider context of this research: the history of the Hubble Telescope, the nature of spiral galaxies, the surprising discovery of dark energy and the sophisticated methods that allow us to measure the infinite, and then look at the future frontiers of astrophysics that promise to reveal further mysteries of the cosmos.
The Unparalleled Eye of Hubble: A Window on Cosmic Expansion
The Hubble Space Telescope is undoubtedly one of the greatest triumphs of 20th century engineering and science. Launched in the Earth’s orbit in 1990, jointly by NASA and ESA, Hubble revolutionized astronomy, offering an unprecedented vision of the universe, free from distortions caused by the Earth’s atmosphere. His ability to operate in the electromagnetic spectrum, from the near ultraviolet to the near infrared, passing through the visible, allowed him to capture images with a clarity and detail impossible to obtain with the terrestrial telescopes of the time. Before Hubble, the measurement of the expansion rate of the universe was afflicted by significant uncertainties, with estimates that varied considerably. It was thanks to Hubble's observations variables Cepheids – stars whose intrinsic luminosity pulsates at regular intervals, providing “standard candles” to measure cosmic distances – that astronomers managed to calibrate the scale of distances with a much greater precision. This allowed to refine the Hubble Coast, the value that describes the speed with which the universe is expanding. The history of Hubble was not exempt from challenges; a defect in the main mirror was corrected with a historic service mission in 1993, transforming the telescope from a disappointment to a scientific icon. Since then, Hubble has produced a constant flow of discoveries, from the confirmation of the existence of supermassive black holes in the center of galaxies, to the identification of galaxies in the primordial universe, to the provision of crucial data for the study of the study of the dark matter and dark energy. The observations of Mrk 1337, like those of countless other galaxies, are a perfect example of Hubble’s ongoing mission: not only admiring cosmic beauty, but collecting vital data to answer fundamental questions about the origin, evolution and destiny of the universe. Each pixel, each captured wavelength, contributes to an overall model, allowing us to reconstruct the story of the universe piece after piece. Hubble's legacy has been and continues to be immense, not only for its direct discoveries, but also for paving the way for future generations of spatial observers, such as the James Webb Space Telescope, which is now carrying out this research with even greater capacity.
The Mystery of the Galaxies in Spirale and Cosmic Dance
Galaxies are the structural foundations of the universe, gigantic islands of stars, gases, dusts and dark matter held together by gravity. Among the various galactic morphology, the spiral galaxies are among the most fascinating and recognizable, characterized by their distinctive arms wrapped around a central core. Mrk 1337 is an example of a spiral galaxy “lowly barted”, a subclass where spiral arms do not emerge directly from the center, but from a linear structure of stars and gases that crosses the galactic nucleus, known as “barra”. It is estimated that about half of all spiral galaxies, including our Via Lattea, they own a bar. These bars are not only aesthetic elements; they play a crucial role in the dynamics and evolution of galaxies. It is believed that the bars act as gravitational “channels”, channeling gas and dust from the external disk to the galactic center, thus feeding the stellar formation in the nucleus and, potentially, the activity of the supermassive black hole inside it. Studying galaxies like Mrk 1337 allows us to better understand these processes of mass transfer and energy, and how they affect the stellar birth rate and the growth of central black holes over billion years. The spiral arms themselves are regions of higher density, where the gas is compressed, triggering the formation of new bright stars, visible as the bluish areas in Hubble images. The reddish areas, on the other hand, indicate the presence of gas heated by young stars. The distribution of these regions, observed through different wavelengths, provides astronomers with a detailed map of galactic activity. Understanding the structure and dynamics of bare spiral galaxies is fundamental not only for galactic morphology, but also to calibrate cosmic distances. For example, the brightness of some stars or phenomena within Mrk 1337 could be used as a reference for distance measurements, provided that the galactic context is fully understood. The complexity of these structures and their ubiquity in the universe demonstrate how much still there is to be learned about the formation and evolution of galaxies, and how every new image of a single cosmic object, like Mrk 1337, can offer valuable insights for the overall picture of cosmology.
Accelerated Expansion of the Universe: From Big Bang to Dark Energy
The discovery that the universe is expanding was one of the deepest revelations of modern science. It was the astronomer Edwin, in the 1920s, to provide the first convincing observative evidence that galaxies are moving away from ours, and that they are farther away, the faster they turn away – a principle known as the Hubble Law. This discovery confirmed the theories previously proposed by Georges Lemaître and laid the foundations for the Big Bang model. For decades, it has been believed that the expansion of the universe should slow down due to the gravitational force of all the matter contained within it. The surprise arrived at the end of the 1990s, when two independent astrophysicist teams, led respectively by Adam Riess, Saul Perlmutter and Brian Schmidt, using the observations of type Ia supernova – stellar explosions whose intrinsic luminosity is remarkably uniform, making them excellent “standard candles” to measure extremely large distances – they discovered that the expansion of the universe was not slowing down, but, on the contrary, was accelerating. This discovery was so unexpected and revolutionary that its authors were awarded the Nobel Prize for Physics in 2011. The implication of a rapidly expanding universe was the postulation of the existence of an unknown form of energy, renamed dark energy. Dark energy is an enigmatic concept, not directly detectable, but whose presence is influenced by its gravitational effects on a cosmic scale. It is believed to be about 68% of the total energy density of the universe, acting as a kind of negative pressure that pushes space to expand faster and faster. Together with dark matter (about 27% of the universe), which interacts only gravitationally and does not emit or absorb light, ordinary matter (barionic) is only about 5% of what exists. This “coordination model” or model Lambda- CDM (where Lambda stands for the cosmological constant associated with dark energy and CDM for Cold Dark Matter, cold dark matter) is currently the most accepted picture to describe the composition and evolution of the universe. Research on the rate of expansion, such as the one involving Mrk 1337 and other galaxies, is essential to refine our understanding of dark energy. Determining its nature – if it is a cosmological constant, as Einstein predicted, or if its density varies over time – is one of the greatest challenges of contemporary cosmology, with deep implications on the ultimate destiny of our universe: if it will continue to expand indefinitely, finally tearing all structures (Big Rip), or if dark energy will weaken, allowing gravity to take over.
La Scala delle Distanze Cosmiche: Measuring Infinity
To understand the expansion of the universe and the nature of dark energy, it is essential to measure cosmic distances with extreme precision. But how do you calculate the distance of a distant galaxy millions or billions of light years? Astronomers rely on a “scale of cosmic distances”, a series of interconnected methods that allow to determine ever greater distances. The first step of this scale is the parallax stellar, a geometric method that exploits the apparent shift of a star in the background when the Earth orbits around the Sun. Although effective for relatively close stars (up to a few thousand light years with modern satellites like Gaia), it is not enough for galaxies. For greater distances, astronomers rely on “standard candles”, celestial objects with an intrinsic luminosity known. The variables Cepheids are the next, and crucial, step of the scale. These stars pulsate with a period directly related to their intrinsic luminosity: the longer they are bright, the longer their pulsation period. Measuring the period of a Cepheid in a distant galaxy, and comparing its apparent luminosity to the intrinsic one, you can calculate the distance of the galaxy. It was Edwin Hubble who first used the Cepheids to prove that the “coil nebulae” were actually external galaxies at the Milky Way. The Hubble observations of galaxies such as Mrk 1337 are often aimed at identifying and studying the Cepheids within them, providing basic data to calibrate the distances for steps farther than the scale. For greater distances, up to the margins of the observable universe, the use of type Ia supernova. These stellar explosions occur when a white dwarf in a binary system increases enough matter to exceed the limit of Chandrasekhar and collapse, triggering a thermonuclear reaction. Since the process that generates it is relatively uniform, the Ia type supernovae have an almost constant intrinsic brightness, making it exceptional “standard candles” for billion-year-old distances of light. The discoveries of Riess, Perlmutter and Schmidt on accelerated expansion were based on the observation of these supernovae. Despite success, the calibration of the distance scale is not exempt from challenges. There is a persistent “Hubble extension”, a discrepancy between the value of the Hubble Coast derived from the measurements of the cosmic microwave fund (CMB), which represents the primordial universe, and that obtained from the direct measurements of standard candles in the local universe. This voltage, if confirmed, may indicate the need for a new physics beyond the Lambda-CDM model, perhaps by changing the nature of dark energy or dark matter, or even gravity itself. The continuous research, powered by telescopes such as Hubble and its successors, is focused on solving these discrepancies, thus offering a more complete understanding of the universe.
Beyond Hubble: New Frontiers and the Future of Astrophysics
The era of space astronomy inaugurated by Hubble is far from being completed. Indeed, we are witnessing the dawn of a new generation of observers who promise to push even further beyond the boundaries of our knowledge. The James Webb Space Telescope (JWST), the spiritual successor of Hubble, works mainly in infrared, a crucial wavelength to study the first galaxies of the universe, stellar and planetary formation, and even the atmospheres of exoplanets. His superior abilities are already revealing a much richer and more complex primordial universe than he thought, offering new perspectives on galactic evolution and the formation of the first cosmic structures. In parallel, missions like Euclid eSA, recently launched, and the future Roman Space Telescope of NASA, they are specifically designed to study dark energy and dark matter on cosmic scales. Euclid will create a 3D map of the universe by observing billions of galaxies up to 10 billion light years away, providing unprecedented data on the distribution of dark matter and the evolution of galaxies, all to better understand the acceleration of cosmic expansion. The Roman Space Telescope, with its wide field of view, will be able to capture large slices of sky, allowing to identify a huge number of Ia type supernovae and to study the effect of gravitational lensing on a large scale, both key tools to probe the nature of dark energy. But the astrophysics of the future will not be limited to visible and infrared light. The era ofmulti-message astronomy has already begun, integrating observations from different “windows” on the cosmos. The detectors of gravitational waves like LIGO and Virgo, and the future LISA space observatory, will open a completely new perspective on the universe, allowing us to study fusions of black holes and neutron stars, and even to probe the universe in its most primordial phases, before it was transparent enough to emit light. The observations of the microwave cosmic background (CMB) they will continue to be fundamental, providing a photograph of the universe when it was only 380.000 years old and allowing us to measure cosmological parameters with incredible precision. Coordination between these different techniques and tools is the key to addressing the current challenges of cosmology, such as the Hubble Extension. Every new mission, every new observation, adds a piece to the gigantic puzzle of the universe, bringing us closer and closer to understanding not only as it is done, but also because it is so, and what will be its ultimate destiny. The journey of cosmic discovery is an endless epic, a testimony of the insatiable curiosity of humanity and its incessant search for knowledge in the immensity of space and time.
