- 4545 - LIFE ON EXOPLANETS? - We have gained so much powerful knowledge in the past few hundred years. But there’s still so much that we don’t know. There are limits to our current knowledge of the universe. In astronomy, we have recently discovered that 95% of the matter and energy contents of the universe, dubbed dark matter and dark energy, are of a form completely unknown to modern science.
------------------------------------------ 4545
- LIFE ON
EXOPLANETS?
-
- Everything we have ever studied and learned
in our exploration of atoms, chemicals, and forces, every star we see in the
night sky and every galaxy we observe in the distant cosmos, makes up less than
5% of the entire universe.
-
- We have pushed our understanding of the
history of the universe into the earliest moments of the big bang, with a firm
grasp of the physics underlaying the first few minutes of the existence of the
cosmos. But beyond that is murky haze, a tangled mess of unsolved mathematics
and over-complicated physics. We do not understand the origins of our universe,
or even if that question makes sense, if our knowledge of time and space even
apply at such extreme scales.
-
- We do not know how to merge our knowledge of
gravity, as expressed through general relativity, with our understanding of
quantum physics, which governs the other forces of nature. We do not know how
gravity operates at extremely small scales, preventing us from understanding
the big bang itself and the true nature of black holes.
-
- Despite cracking the code of DNA and the role
that genetics plays in the evolutionary process, we do not understand how life
first arose on the Earth, and whether we are truly alone in the cosmos. We do
not know how sexual reproduction arose, or where viruses originated from, or
the full extent of life on Earth. We do not understand the full variety of
molecular interactions that power our own biochemistry, or how the components
of our cells came to find themselves working together.
-
- We do not know if superconductors, which
allow for the transmission of electricity with no resistance, is possible at
room temperature. We do not know the full tectonic history of the Earth, or
even if duplicates of the Earth’s climate system exist on other worlds orbiting
alien stars.
-
- We do not even understand the origins, or
even nature, of our own conscious thoughts, the source of our thirst for
knowledge and our capacity to access it.
We do not even know how we are able to ask these questions.
-
- However we have learned the existence of
extrasolar plane. The census recently
passed a major milestone, with 5500 confirmed candidates in 4,243 solar systems
astronomers have learned a great deal about the types of planets that exist in
our galaxy and have been rethinking several preconceived notions. These include
the notion of “habitability” and whether Earth is the standard by which this
should be measured.
-
- Traditionally, astronomers have defined
habitable zones based on the type of star and the orbital distance where a
planet would be warm enough to maintain liquid water on its surface. But in
recent years, other factors have been considered, including the presence of
planetary magnetic fields and whether they get enough ultraviolet light.
-
- On Earth, the presence of an intrinsic
magnetic field has been vital to the emergence and evolution of life as we know
it. Without it, our atmosphere would have been stripped away long ago by
energetic particles emanating from the Sun, which was the case with Mars. In
addition to Earth’s atmosphere, our planet’s magnetic field ensures that a
limited amount of solar radiation and cosmic rays reach the surface. For this
reason, astrobiologists consider a planetary magnetic field essential for
determining whether or not an exoplanet is habitable.
-
- Another factor is how the strength of a
planet’s magnetic field and its interaction with its parent star’s magnetic
field affect habitability. Not only does an exoplanet require a strong field to
shield it against stellar activity (solar flares, etc.), but it must also orbit
far enough to avoid a direct magnetic connection with its star.
-
- The magnetic interactions between planets
and their parent stars are known as “space weather”. The team examined 1,546 exoplanets to
determine if they orbited inside or outside their host star’s Alfvén radius,
the distance where stellar wind decouples from the star. This consisted of
characterizing the stars’ activity known using their Rossby number (Ro), the
ratio between a star’s rotational period to their convective turnover time.
-
- Planets orbiting within this radius would
directly interact magnetically with the star’s corona, leading to significant
atmospheric stripping, ruling them out as viable candidates for habitability.
This phenomenon has been observed with TRAPPIST-1 and its system of seven
exoplanets. After examining the exoplanets in their study, they found that only
two planets met all the conditions for potential habitability. These were K2-3
d and Kepler-186 f, two Earth-sized exoplanets 144 and 579 light-years from Earth.
-
- These planets have strong enough magnetic
fields to protect them from stellar activity.
These findings are also indicative of current efforts among astronomers
and astrobiologists to refine the definition of “Habitable Zone” and create a
more nuanced understanding.
-
August 30, 2024 4500
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--------------------- --- Friday, August 30, 2024
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