Does Earth have a chance? It remains a topic of debate whether our planet will survive the end of the sun or be consumed by it. The discovery of an Earth-like exoplanet orbiting a white dwarf provides some hope. This planet has survived the expansion of its sun-like star into a red giant, despite orbiting at a distance similar to that of Earth from the sun. This suggests that Earth might also endure this phase, according to astronomers.
As our sun approaches its end of life cycle, it will expand and become a red giant. In approximately six to seven billion years, this solar red giant will swallow Mercury and Venus and reach Earth’s orbit. But what will happen to Earth? It is evident that our planet will eventually turn into a dead, waterless desert world. Can it at least avoid being devoured?
The expanding sun is damaging the inner planets – will this fate also threaten Earth? © Fsgregs /CC-by-sa 3.0
The answer to this question is controversial. On one hand, the sun will expand to reach Earth’s orbit. On the other hand, its increased stellar wind pushes the planets further outwards – including Earth’s orbit. If this outward shift happens faster than the sun’s growth, Earth could survive the red giant phase. However, astronomers have previously discovered only a few extrasolar gas giants orbiting white dwarfs that have survived the red giant phase of their stars, but no Earth-like planets.
Rocky planet around a burnt-out stellar remnant
That has now changed: Astronomers led by Keming Zhang from the University of California, San Diego, have discovered an Earth-like exoplanet resembling a future version of our own planet. Located about 4,000 light-years away, the planet orbits the burnt-out remnant of a sun-like star that had one to two solar masses. This star has passed its red giant phase, shed its outer layers, and is now only about 0.5 solar masses heavier than a white dwarf.
The system was discovered in July 2020 when it transited in front of a background star. This allowed astronomers to observe the star and its planets, estimating their mass through gravitational lensing. Due to initial observations being imprecise, Zhang and his team re-examined the system, named KMT-2020-BLG-0414, in 2023 using the high-resolution optics of the ten-meter Keck-II telescope in Hawaii.
Exoplanet has an orbit similar to Earth…
The follow-up observations revealed that the exoplanet, designated KB200414Lb, is approximately 20 percent larger than Earth and has a mass of about 1.9 Earth masses, making it akin to a slightly larger sibling of our planet. However, the orbit of this exoplanet is even more intriguing: it currently orbits the white dwarf at a distance of about 2.3 astronomical units, as determined by Zhang and his team. In terms of our solar system, this would place the planet at the location of the asteroid belt between Mars and Jupiter.
Before the star burned out, exoplanet KB200414Lb likely had an orbit very similar to that of Earth. “Considering the orbit expansion during the final stages of the central star, this Earth-like planet may have originally orbited at about one astronomical unit,” the astronomers report. In other words, this planet orbited its star at the same distance that Earth orbits the sun.
…and survived the end of its sun
The exoplanet thus presents a potential future scenario for Earth, raising hopes for its survival. The planet KB200414Lb and its star demonstrate that Earth can successfully navigate the challenge posed by an expanding sun and the outward shift of its orbit. In about eight billion years, our planet could still exist and have survived the sun’s red giant phase.
“Whether life on Earth can survive this phase remains uncertain. However, the key takeaway is that Earth does not necessarily need to be swallowed by the sun when it becomes a red giant,” explains co-author Jessica Lu from the University of California, Berkeley. “KB200414Lb has also survived the red giant phase of its star.” (Nature Astronomy, 2024; doi: 10.1038/s41550-024-02375-9)
Source: University of California Berkeley
September 27, 2024 – Nadja Podbregar
Does Earth Have a Chance? The Survival of Our Planet as the Sun Evolves
As humanity grapples with the long-term future of Earth, one key question looms: will our planet survive the end of the sun? Recent discoveries suggest a glimmer of hope. Astronomers report the existence of an Earth-like exoplanet orbiting a white dwarf, which has successfully endured the expansion of its parent star into a red giant.
The Lifecycle of Our Sun
In approximately six to seven billion years, our sun will enter its red giant phase, expanding significantly and likely swallowing Mercury and Venus, before possibly reaching Earth’s orbit. But what about Earth itself? With predictions indicating our planet could become a barren, waterless desert, the question remains: Can Earth avoid being engulfed?
The Expanding Sun: Threat or Opportunity?
The solar expansion poses a dual threat. As the sun grows, its increased stellar wind may push the Earth’s orbit outward. If this outward movement occurs faster than the sun’s expansion, there’s a possibility that Earth could survive this red giant phase. To date, astronomers have primarily identified gaseous exoplanets that managed to survive this phase around white dwarfs, but the search for rocky, Earth-like planets has been challenging.
Discovery of a Survivor: KB200414Lb
A significant breakthrough came thanks to the work of astronomers led by Keming Zhang at the University of California, San Diego. This team discovered an Earth-like exoplanet approximately 4,000 light-years away, orbiting a white dwarf that was once a sun-like star. Shrunken to a fraction of its former size, this star has shed its outer layers and stabilized into a white dwarf.
Scientific Discovery Process
Identified in July 2020, the exoplanet’s existence became evident when it transitively moved in front of a background star, allowing researchers to observe and analyze it through gravitational lensing effects. Further high-resolution observations were conducted in 2023 using the advanced capabilities of the ten-meter Keck-II telescope in Hawaii, confirming the planetary characteristics.
Characteristics of KB200414Lb
The discoveries surrounding the exoplanet, designated KB200414Lb, reveal some intriguing features:
- **Size:** About 20% larger than Earth.
- **Mass:** Approximately 1.9 times that of Earth.
- **Orbit:** Currently situated at about 2.3 astronomical units from its white dwarf, analogous to the distance from Mars to Jupiter.
- **Potential Original Orbit:** Suggests it may have orbited its parent star at roughly 1 astronomical unit, akin to Earth’s current orbit around the sun.
Lessons from KB200414Lb: Hope for Earth
The survival of KB200414Lb provides valuable insight into Earth’s potential future. This exoplanet has demonstrated that in the cosmic race between a star’s expansion and a planet’s shifting orbit, survival is indeed possible. This leads astronomers to ponder a hopeful scenario in roughly eight billion years where Earth may exist beyond the sun’s red giant phase.
Potential for Life on Earth
While the prospect of Earth surviving the red giant phase is tantalizing, the question of whether life could persist remains complex. As co-author Jessica Lu articulated, “Whether life on Earth can survive this phase is quite questionable. However, it is crucial that Earth doesn’t necessarily need to be swallowed by the sun.”
Comparative Analysis: Survival Factors
| Factor | KB200414Lb | Earth |
|---|---|---|
| Current Orbit (AU) | 2.3 | 1 |
| Size Ratio | 20% larger | Baseline |
| Mass (Earth Masses) | 1.9 | 1 |
| Future Orbit Potential | Expanded around 1 AU | Possible |
| Life Viability | Unknown | Questionable |
The Implications of These Discoveries
This research opens the door to new inquiries about planetary survival in our universe. The resilience showcased by KB200414Lb suggests that Earth might also have the capacity to endure cosmic changes over astronomical timescales.
Looking Towards the Future
As we study these distant planets and their interactions with their stars, our understanding of environmental conditions necessary for habitability grows more profound. The ongoing investigations into the life cycle of stars and the fate of planets will guide humanity’s long-term planning for Earth.
Final Thoughts
While the fate of Earth as our sun approaches the end of its life may seem dire, the discoveries of exoplanets like KB200414Lb provide hope and cautionary tales about planetary resilience. As we expand our cosmic knowledge, we can better comprehend the universe’s dynamics and Earth’s place within it.
