This Summer, both seasoned astronomers and enthusiastic stargazers worldwide will direct their gaze towards a particular petite constellation nestled within the expanse of the night sky. However, it's not the familiar sight of Corona Borealis, the "Northern Crown," with its constellation of seven stars that commands attention. Instead, it's a seemingly inconspicuous void within this constellation that has ignited widespread intrigue. Here, an imminent nova event, projected to blaze with such luminosity that it will be discernible to the naked eye from Earth, awaits its moment to unfold.
"In the realm of celestial occurrences, this singular event promises to cultivate a legion of fresh stargazers, granting young enthusiasts a chance to behold a cosmic spectacle firsthand, craft their own inquiries, and compile individualized observations," declared Dr. Rebekah Hounsell, an assistant research scientist with expertise in nova phenomena at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "It stands as a beacon of inspiration for the scientists of tomorrow."
T Coronae Borealis, affectionately named the "Blaze Star" and scientifically recognized as "T CrB," resides within the Northern Crown constellation approximately 3,000 light-years distant from Earth.
This binary system consists of a white dwarf, a compact remnant of a deceased star roughly the size of our planet but with a mass akin to the sun, and an aging red giant gradually losing its hydrogen to the insatiable gravitational forces exerted by its voracious companion.
Hydrogen siphoned from the red giant accumulates on the surface of the white dwarf, leading to a gradual escalation of pressure and temperature.
Eventually, this buildup culminates in a thermonuclear explosion of significant magnitude, effectively dispersing the accreted material. In the case of T CrB, this phenomenon seems to repeat at intervals averaging around every 80 years.
Hounsell clarified the distinction between a nova and a supernova, emphasizing that while supernovae mark the cataclysmic demise of certain stars, novae entail a different phenomenon. In a nova event, the dwarf star endures, expelling the accumulated material into space in a dazzling burst. This cycle often recurs over extended periods, potentially persisting for tens or even hundreds of thousands of years.
"Although there are a few recurrent novae with exceptionally short cycles, witnessing repeated outbursts within a human lifetime is uncommon, particularly one occurring relatively close to our own system," remarked Hounsell. "Having this front-row seat to such an event is incredibly thrilling."
Locating T Coronae Borealis
Locating T Coronae Borealis (T CrB) for potential observation requires a journey through both historical records and contemporary astronomical insights. The first documented sighting of the T CrB nova dates back over 800 years to autumn 1217 when Burchard, the abbot of Ursberg, Germany, described his observation of "a faint star that for a time shone with great light."
The most recent sighting from Earth occurred in 1946. Notably, recent observations suggest behavior akin to that leading up to the 1946 eruption. If this trend persists, some researchers speculate that the nova event might unfold by September 2024.
For those eager to witness this celestial spectacle, locating the Northern Crown, nestled west of the Hercules constellation, is essential. This horseshoe-shaped array of stars can be discerned on clear nights by identifying two of the brightest stars in the Northern Hemisphere—Arcturus and Vega—and tracing a direct line between them. This trajectory will guide skywatchers to Hercules and ultimately to the Corona Borealis.
The anticipated outburst will be fleeting. Once it commences, visibility to the naked eye will extend for slightly less than a week. Nonetheless, Hounsell expresses confidence that this event will be a remarkable sight to behold.
An Integrated Scientific Strategy
Dr. Elizabeth Hays, chief of the Astroparticle Physics Laboratory at NASA Goddard, echoed this sentiment. She emphasized the excitement generated by amateur stargazers as they gear up to witness the event. Their fervor for exploring the depths of space has fostered a longstanding and fruitful collaboration with NASA.
"Citizen scientists and space enthusiasts are constantly on the lookout for prominent, luminous signals indicating nova events and other cosmic phenomena," Hays remarked. "Through social media platforms and email networks, they swiftly disseminate alerts, raising awareness. We rely on this global community engagement once more as we anticipate the spectacle of T CrB."
Hays serves as the project scientist for NASA's Fermi Gamma-ray Space Telescope, a pivotal role she has held since 2008. Fermi, operating from low Earth orbit, has been diligently conducting gamma-ray observations for over a decade. When the nova eruption of T CrB is detected, Fermi stands ready to capture crucial data alongside other esteemed space-based missions.
These include NASA's James Webb Space Telescope, Neil Gehrels Swift Observatory, IXPE (Imaging X-ray Polarimetry Explorer), NuSTAR (Nuclear Spectroscopic Telescope Array), NICER (Neutron star Interior Composition Explorer), and the European Space Agency's INTEGRAL (Extreme Universe Surveyor). Together, these missions form a formidable array of observational tools poised to unravel the mysteries of cosmic phenomena.
Several ground-based radio telescopes and optical imagers, such as the National Radio Astronomy Observatory's Very Large Array in New Mexico, will join the endeavor. Together, these instruments will collaborate to capture data spanning the entire electromagnetic spectrum, from visible light to non-visible wavelengths.
"We'll meticulously observe the nova event from its zenith to its gradual fade, tracking the visible energy emitted during the outburst," explained Hounsell. "Yet, acquiring data during the initial stages leading up to the eruption is equally imperative. Therefore, the contributions from dedicated citizen scientists currently monitoring the nova's activity will significantly enhance our research outcomes."
For astrophysics researchers, this presents a unique chance to illuminate the intricacies of recurrent stellar explosions like the forthcoming nova event.
"Usually, nova occurrences are distant and faint, making it challenging to pinpoint the focal points of erupting energy," explained Hays. "However, this event will occur in close proximity, attracting considerable attention from observers scrutinizing multiple wavelengths. We anticipate that this collective effort will furnish invaluable data, paving the way to unravel the underlying structure and intricate processes at play. We're eager to piece together the complete narrative of this phenomenon."
Among those observers, many will be relatively new to the field. For instance, gamma-ray imagers weren't available during T CrB's last eruption in 1946. Additionally, the polarization capability of IXPE, a tool in X-ray astronomy that discerns the alignment of electromagnetic waves, is a recent addition. By merging their datasets, researchers aim to gain unprecedented insights into the life cycles of binary systems and the potent stellar processes that drive them, even in their declining phases.
Is there a possibility that September might pass without the anticipated nova outburst from T CrB? Experts concur that there are no certainties, but optimism persists.
"Recurrent novae are enigmatic and capricious," noted Dr. Koji Mukai, a fellow astrophysics researcher at NASA Goddard. "Just when you believe they adhere to a discernible pattern, they surprise you. Conversely, when you anticipate a departure from the norm, they may adhere steadfastly to it. We shall observe T CrB's behavior with keen interest.
