New research using the ALMA telescope reveals that frequent and extremely intense bursts of radiation from Proxima Centauri could destroy the atmospheres of nearby planets and make them uninhabitable.
Using the ALMA radio observatory, astronomers have discovered that Proxima Centauri – the closest star to the Sun – frequently emits high-energy bursts at millimeter wavelengths. These bursts can significantly alter, and possibly completely erode, the atmospheres of nearby planets in its habitable zone.
Proxima Centauri is just over four light-years away and is the closest star to our solar system. It is a particularly active red dwarf. While its outbursts have long been observed in visible light, new research using the Atacama Large Millimeter/submillimeter Array (ALMA) has found that the star is also intensely active in the radio and millimeter wavelengths. These observations provide new insight into the particle nature of the outbursts and raise important questions about their possible impact on the suitability of life on nearby planets.
Extremely active star
Proxima Centauri is known to host at least one Earth-like planet, located in the system's habitable zone. Similar to solar flares from our Sun, Proxima's flares emit energy across the electromagnetic spectrum, releasing bursts of high-energy particles called Stellar Energetic Particles.
The intensity and frequency of the eruptions could pose a serious threat to nearby planets. If the eruptions are strong enough, they could erode the atmosphere and damage vital components such as the ozone layer and water – potentially rendering these planets uninhabitable.
Investigating outbreaks using ALMA
A team of astronomers led by Kiana Burton of the University of Colorado and Professor Meredith McGregor of Johns Hopkins University used archival data and new observations from the ALMA telescope to study the Proxima Centauri outbursts in the millimeter wave range.
Proxima Centauri has a different structure than the Sun – it is smaller and has a much stronger magnetic field, and its internal structure is likely fully convective (meaning plasma currents heat and mix the entire thing), unlike the Sun, which has convective and non-convective regions.
Proxima's magnetic fields become strained and distorted – until they break, creating bursts of energy.
Prof. McGregor summarized the central question of the study:
"Our sun doesn't strip Earth of its atmosphere, but it creates spectacular flares. We have a strong magnetic field and a dense atmosphere. But on Proxima, the outbursts are much stronger – and there are rocky planets in its habitable zone. What does this radiation do to their atmospheres? Are they chemically altered? Or does the atmosphere simply disappear?"
Unprecedented research into multiple wavelengths
This is the first study to incorporate observations at millimeter wavelengths for a deeper understanding of the physics of the eruptions.
The researchers used 50 hours of observations with the ALMA telescope, which included the full 12-meter array and the compact Atacama array (7 meters). The result: 463 energy bursts were detected, at levels between 102410^{24} and 102710^{27} arg.
The bursts themselves were short, lasting between 3 and 16 seconds. “When we look at the bursts with ALMA, we pick up the electromagnetic radiation – that is, the light at different wavelengths,” says McGregor. “But using radio waves, we can also understand the properties of the particles that are released and measure their energy.”
To do this, the researchers mapped the frequency distribution of the bursts—that is, how many bursts occur at different energy levels. Usually, the curve follows a power law: smaller bursts are more common, and larger ones are less common. But Proxima Centauri has so many bursts that the researchers were able to measure all ranges—and even characterize an asymmetry between the burst phase and the decay phase of the burst.
Observations in the radio and millimeter range make it possible to determine precise limits on the energy intensities of the bursts and the accompanying particles.
McGregor emphasizes: "The bursts at millimeter waves are much more frequent – it's a different power law than what we see in the optical domain. If we only look at visible light – we'll miss critical information. ALMA is the only millimeter-wavelength interferometer sensitive enough for these measurements."
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So wait, is there life in another world?
Proxima is the secondary sun in a system that has 3 suns, of which Alpha Centauri is the primary sun.
The system is named after Alpha Centauri, not Proxima.
In the first line, "Astronomers have discovered that Proxima Centauri – the closest planet to the Sun" – please delete the word "proxima" because Proxima Centauri is a star.