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Hubble Telescope Observes Evaporating Planet Exhibiting Hiccup-Like Behavior During Orbits

In the depths of space, Hubble Telescope observes evaporating planet exhibiting hiccup-like behavior during orbits. This cosmic spectacle is marked by an intriguing twist - with each passing orbit, the planet undergoes unforeseen changes, keeping astronomers on their toes.

Landon Morton
Jul 31, 20233217 Shares86958 Views
In the depths of space, Hubble Telescope observes evaporating planet exhibiting hiccup-like behavior during orbits. This cosmic spectacle is marked by an intriguing twist - with each passing orbit, the planet undergoes unforeseen changes, keeping astronomers on their toes.
Drawn perilously close to its parent star, the planet endures an unyielding torrent of energy, which relentlessly evaporates its once abundant hydrogen atmosphere, causing it to dissipate into space. However, the enigma deepens when, during one orbit meticulously observed through the lens of the Hubble Space Telescope, the planet appears strangely immune to atmospheric loss. Yet, perplexingly, a year and a half later, another Hubble observation reveals evident signs of its atmosphere vanishing into the void.

Probing Extreme Planetary Conditions

Astronomers were taken aback by the astonishing fluctuations observed between orbits of a young planet twirling around a fiery red dwarf star. Keighley Rockcliffe of Dartmouth College in Hanover, New Hampshire, expressed her bewilderment, stating that such extreme variability in atmospheric escape had never been witnessed before. The planet's behavior defied expectations, swinging from complete undetectability of atmospheric loss during one observation with the Hubble Space Telescope to unmistakable signs of evaporation a mere year and a half later.
Adding to the mystery, Rockcliffe noted that when the atmospheric escape was detectable, the planet's atmosphere seemed to puff out in front of it, akin to a headlight on a swiftly moving train. This peculiar phenomenon became a stress-test for planetary evolution models and physics, offering a unique opportunity to explore the intricate interplay between the youthful star AU Microscopii (AU Mic) and its planetary companion.
AU Mic, situated 32 light-years away from Earth, is home to one of the youngest planetary systems ever documented, with the star's age being less than 100 million years (a tiny fraction of our Sun's 4.6 billion-year lifespan). The innermost planet, AU Mic b, orbits the star every 8.46 days, maintaining a proximity of only 6 million miles (approximately one-tenth the distance between Mercury and our Sun). This bloated, gaseous world is about four times larger than Earth in diameter, making it a fascinating subject of study for astronomers seeking to unlock the secrets of planetary formation and evolution.

AU Mic B - Discovery And Characteristics

AU Mic b was found using NASA's Spitzer and TESS (Transiting Exoplanet Survey Satellite) space telescopes back in 2020. The discovery utilized the transit method, where telescopes detect a slight decrease in the star's brightness when the planet passes in front of it.
Red dwarfs, such as AU Microscopii, are the most abundant type of stars in our Milky Way galaxy. As a result, they are expected to host a large number of planets. However, the question remains whether planets orbiting red dwarf stars like AU Mic b can be suitable for supporting life.
One significant challenge is that young red dwarfs are known for their intense stellar flares that release powerful radiation. These periods of heightened activity last considerably longer than those observed in stars like our Sun.

Challenging Living Conditions On Red Dwarf Planets

The flares are driven by incredibly strong magnetic fields that become entangled due to the turbulent movements within the stellar atmosphere. When this tangling reaches a critical point, the magnetic fields break and reconnect, releasing an immense amount of energy that surpasses the energy released by our Sun during its outbursts by 100 to 1,000 times.
The result is a spectacular display of fierce winds, intense flares, and X-rays that pose a significant threat to any planets situated in close proximity to the star. "This creates a really unconstrained and frankly, scary, stellar wind environment that’s impacting the planet’s atmosphere," said Rockcliffe.
An illustration of a red dwarf planet's atmosphere being stripped away by a bigger star
An illustration of a red dwarf planet's atmosphere being stripped away by a bigger star

Questions On Planetary Survival And Habitability

In such extreme conditions, planets that form within the initial 100 million years of the star's birth would undergo significant atmospheric escape. The intense stellar activity during this early period can lead to a complete stripping of a planet's atmosphere.
"We want to find out what kinds of planets can survive these environments. What will they finally look like when the star settles down? And would there be any chance of habitability eventually, or will they wind up just being scorched planets?" said Rockcliffe. "Do they eventually lose most of their atmospheres and their surviving cores become super-Earths? We don’t really know what those final compositions look like because we don’t have anything like that in our solar system."
Due to the star's intense brightness, Hubble cannot directly observe the planet. However, the telescope can still detect variations in the star's apparent brightness caused by hydrogen escaping from the planet and partially blocking the starlight during the planet's transit. The atmospheric hydrogen has been heated to such high temperatures that it surpasses the planet's gravitational pull, allowing it to escape into space.

Unprecedented Variability In Atmospheric Outflow

The unprecedented fluctuations in atmospheric outflow from AU Mic b suggest rapid and intense variability in the host red dwarf's outbursts. This variability arises due to the presence of numerous turbulent magnetic field lines on the star's surface. One potential explanation for the absence of hydrogen during a particular planet transit is the occurrence of a powerful stellar flare, observed seven hours before, which might have photoionized the escaping hydrogen, rendering it transparent to light and undetectable.
Alternatively, the shape of the stellar wind itself could be influencing the planetary outflow, causing it to be observable during certain periods and not during others, and even leading to some outflow occurring ahead of the planet itself. This phenomenon is consistent with certain scientific models proposed by researchers such as John McCann and Ruth Murray-Clay from the University of California at Santa Cruz. However, this is the first observational evidence of such extreme occurrences.
Further Hubble observations of additional AU Mic b transits are expected to provide more insights into the unusual variability of both the star and the planet, offering valuable opportunities to test and refine scientific models concerning exoplanetary atmospheric escape and evolution.
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