Title: Astronomers Predict the Sun’s Final Act: Transforming Into a Planetary Nebula
Subtitle: Humanity limited to 1 billion years on Earth due to rising brightness of the Sun
Date: November 25, 2022
Scientists have made significant strides in predicting the future of our Sun. These predictions include the circumstances leading up to its demise, the estimated timeline, and what it will ultimately transform into. Notably, humans won’t be present to witness the Sun’s final act.
Previous assumptions suggested that the Sun would evolve into a planetary nebula, a luminous bubble comprised of gas and cosmic dust. However, recent evidence hinted that the Sun’s mass wasn’t sufficient for this transformation. In 2018, an international team of astronomers conducted a groundbreaking study and confirmed that a planetary nebula remains the most likely outcome for our Sun’s afterlife.
With an approximate age of 4.6 billion years, the Sun is expected to reach the end of its life in roughly another 10 billion years based on observations of other stars. However, there are significant events that will transpire before its final curtain call. In approximately 5 billion years, the Sun is projected to expand into a red giant, with its core shrinking while simultaneously engulfing our planet and much of the solar system.
The increasingly brighter future of the Sun poses a greater threat to life on Earth. Over the next billion years, the Sun’s brightness will gradually intensify by 10 percent per billion years. Although this may seem inconsequential, it will ultimately exterminate life on Earth. Rising temperatures will cause the oceans to evaporate, rendering the surface uninhabitable.
The most challenging aspect to predict accurately is the post-red giant stage of the Sun. Past studies indicated that for a bright planetary nebula to form, the initial star would need to be up to twice as massive as the Sun. However, advanced computer modeling used in the 2018 study determined that the Sun, like 90 percent of other stars, is expected to contract from a red giant to become a white dwarf, ultimately transforming into a planetary nebula.
Astrophysicist Albert Zijlstra from the University of Manchester, a co-author of the research paper, explained that when a star dies, it releases its envelope, a mass of gas and dust, into space. This shedding of the envelope reveals the star’s core, which, depleted of fuel, eventually dies. The expelled envelope creates a luminous glow, showcasing the planetary nebula for around 10,000 years before it dissipates. These nebulae, some brighter than the stars they originated from, often appear millions of light-years away.
The team’s data models have provided valuable insights into the life cycles of various stars, aiding in accurately determining the brightness of associated planetary nebulae based on star masses. Planetary nebulae are commonly found throughout the observable universe, with popular examples including the Helix Nebula, the Cat’s Eye Nebula, the Ring Nebula, and the Bubble Nebula.
Although the focus is on the Sun’s fate, astronomers have also discovered another significant relationship. Observing the brightest planetary nebulae across other galaxies consistently revealed a similar level of brightness, enabling astronomers to calculate their distance. While this discovery aligns with the data, it contradicts existing models, posing a longstanding challenge for scientists.
The team’s models have successfully reconciled this discrepancy by determining that the Sun represents the lower limit of mass required for a star to produce a visible nebula. Stars with a mass less than 1.1 times that of the Sun won’t generate a visible nebula, while stars up to three times more massive than the Sun will produce brighter nebulae. The predicted brightness closely matches observations for the remaining stars within that range.
“This is a significant result,” said Albert Zijlstra. “We not only have a way to measure the presence of stars billions of years old in distant galaxies – a range that is remarkably challenging to measure – but we have also discovered what the Sun will eventually become!”
The findings from this study were published in Nature Astronomy, contributing to humanity’s understanding of the Sun’s future and its role in the broader universe.
(Note: This article is an updated version of a previously published article in May 2018)