What that signifies for the hunt for existence is as follows.
Even though the planet in question is not, in and of itself, livable, a
recent finding on a rocky little world [this far] away may give some promise
in the hunt for viable exoplanets.
A team of scientists headed by Pineda and Vassar College astronomer Jackie
Villadsen hypothesize that YZ Ceti b may have a magnetic field that
interacts with its star and causes the system to emit radio waves despite
orbiting its star at a distance that makes it impossible for it to support
liquid water on its surface. The existence of a rocky exoplanet with a
magnetic field may also hint at a tiny part of the solution to an urgent
habitability conundrum.
A NEARBY STAR'S RADIO SIGNALS
Three and possibly a fourth rocky exoplanets, all of which circle their
stars too closely to be livable, are illuminated by the faint reddish light
of the small star YZ Ceti. The nearest member of the group, YZ Ceti b,
travels around the star in just over two days and has surface temperatures
that vary from just below the boiling point of water to more than 400
degrees Fahrenheit. It's not the kind of location where you'd typically
search for information about life or inhabited worlds.
However, when Pineda and Villadsen used the Karl G. Jansky Very Large Array
radio telescope in New Mexico to study the neighborhood star, they
discovered recurring radio wave flashes emanating from the system. No, it
isn't extraterrestrial life; however, it might be proof that YZ Ceti b has a
magnetic field. If Pineda and Villadsen are right—and they say they need
more information before they are sure—then at specific places in the
planet's trajectory, the magnetic field of the planet reacts with the
magnetic field of the star to generate radio waves.
Their results were reported in the journal
Nature Astronomy by Pineda and Villadsen.
Despite YZ Ceti b's hot surface, finding a solid, Earth-like world with a
powerful magnetic field of one's own would be very exciting for habitability
in general. Other stony exoplanets may have magnetic fields if YZ Ceti b
does. And if that's the case, then the likelihood of discovering a solid
planet with an atmosphere in a red dwarf's habitable zone just rose (even
though we don't yet know enough to estimate by how much).
A DANGER ZONE OR A HABITABLE ZONE?
It's most likely going to be somewhere like TRAPPIST-1 or LP-890-9, also
known as SPECULOOS-2: rocky, Earth-sized planets circling cool stars
referred to as red dwarfs. If we're going to discover life, or even a
habitable world, orbiting another star, it's probably going to be
there.
One of the main hotspots in the hunt for habitable worlds is TRAPPIST-1.
Three rocky exoplanets, out of a total of seven, are present in the region
of livable space surrounding the red dwarf star. There is a downside to the
star system, however. Some research hypothesized that the red dwarf star may
have drained these planets of their atmospheres, leaving them without oxygen
and most likely uninhabitable. The habitable zones of red dwarfs are located
near by and are known to produce powerful star outbursts.
If so, that wouldn't be good for our odds of discovering extraterrestrial
species or even a world that is obviously habitable.
The innermost planet of the TRAPPIST-1 system, TRAPPIST-1 b, was revealed
to have no atmosphere, or only a very weak wisp of one, last week, according
to a team of scientists. Given how near TRAPPIST-1b is to its star (it is
essentially the TRAPPIST-1 version of Mercury, so it gets bombarded with
more radiation and stellar wind than its planetary siblings), this shouldn't
come as a total surprise, but it's still depressing.
According to NASA scientist
Taylor Bell, a
co-author of the TRAPPIST-1b study, "I would have been more optimistic for
the cooler planets if TRAPPIST-1b had shown clear signs of an atmosphere in
our observations."
This summer, JWST scientist
Nikole Lewis
of Cornell University and her group will direct its potent sensors at
TRAPPIST-1e, one of the system's three habitable zone planets.
WORLD OF PLANETARY FORCES
However, a magnetic field can act as a barrier to prevent charged ions from
stealing a planet's atmosphere.
According to NASA astrophysicist
Thomas Greene, who wasn't engaged in the YZ Ceti research, "having an organized magnetic
field (like Earth's) could make it more likely that a planet could retain
its atmosphere." "A field like that could slow or stop charged particles
from the star (analogs to our own solar storms)."
Our world is able to support life thanks in large part to the Earth's
magnetic field, even at our comparatively close proximity to the Sun.
Because of the molten metal in our rotating center, which makes the globe
essentially into a gigantic electromagnet, Earth has a pretty powerful
magnetic field. Surprisingly, Mercury also has a magnetic field and a liquid
center. Venus, on the other hand, lacks magnetic fields as a result of their
innards having hardened and cooled over a very long time.
As a result, scientists are unsure of how frequently stony planets can
sustain magnetic fields for any length of time, much less long enough to
support life. Simply put, we lack sufficient instances.
And that's why YZ Ceti b is so significant. In addition to serving as yet
another illustration, it also demonstrates to scientists what to search for
in order to discover other rocky planets that might have magnetic fields:
radio bursts.
If we can confirm YZ Ceti b's magnetic field and start learning from
thousands of exoplanets instead of being limited to a handful of Solar
System objects, it would be a big step forward for our understanding of how
frequently planets can power and sustain, for billions of years, a strong
magnetic field, says
Remo Burn
of the Max Planck Institute for Astronomy, who was not involved in the YZ
Ceti study.
YZ Ceti b produces radio waves when its magnetic field interacts with that
of its star, but that interaction is only made feasible by the planet's
daringly near orbit. The habitable zones of red dwarf stars like TRAPPIST-1,
SPECULOOS-2, and others contain planets that are too far from their stars to
produce radio bursts like the ones Pineda and Villadsen observed from YZ
Ceti. Planets in these zones include TRAPPIST-1, SPECULOOS-2, and others. In
other words, scientists won't be able to use radio bursts to detect worlds
with magnetic fields that may be livable. Still, it's beneficial:
We could determine the strength of the magnetic fields on more temperate
planets by learning how prevalent magnetic fields are, according to
Burn.
Pineda and Villadsen intend to continue watching YZ Ceti in the interim.
The possibility that the radio blasts observed with the Very Large Array
were not totally powered by the star itself, without assistance from a
planet's internal electromagnet, cannot yet be ruled out.
Furthermore, just because a planet, such as YZ Ceti b, has a magnetic field
does not mean that it will also have an atmosphere. That relies on the mass
of the planet, the density of its atmosphere, the strength of its magnetic
field, as well as how frequently and intensely the star flashes.
It's even conceivable that a star like TRAPPIST-1's strong outbursts could
heat a planet's core sufficiently to keep it geologically active and
generate a shielding magnetic field. Just yet, we don't know. Time and
additional evidence will reveal, as always. However, even though it isn't a
certainty, it is probable that any habitable planets we discover will have a
powerful magnetic field protecting their atmosphere.
"We believe that a balanced environment, neither too heavy nor too light,
is essential for existence. But without the safety of a magnetic field,
precisely those atmospheres would be lost most effectively," claims Burn.
Because of this, it becomes a vital component of existence as we know
it.
