- 4291 - NEW ROCKY PLANETS - Observations of faraway rocky planets that might have their own magnetic fields like Earth could help astronomers understand the seemingly haphazard magnetic fields swaddling our solar system’s planets.
------------------------- 4291 - NEW ROCKY PLANETS
- Astronomers call
Earth a rocky planet. Mercury,Venus and
Mars also fit that description. But,
Jupiter, Saturn, Uranus and Neptune are called gaseous planets.
-
- The Milky Way is
full of alien worlds that might make their own magnetic fields. For decades,
astronomers have been perplexed by planetary magnetic fields. In our own solar
system, there is no rule that explains which worlds generate these magnetic
sheaths. Earth has one, but its sister world, Venus does not.
-
- Astronomers
suspect that one of the best ways to understand the mysteries of magnetism
might be to study worlds orbiting other suns. By collecting a census of
exoplanet magnetic fields, researchers could determine whether they are common
features of other worlds. Doing so would help put our solar system in context
and resolve some curiosities.
-
- Earth versus Venus
is a good example, two planets that are similar in size, fairly similar in
composition, but wildly different in terms of magnetic fields. Earth has a magnetic field, but Venus,
Earth’s sister planet, doesn’t. Why does one rocky planet have a magnetic field
while the other does not?
-
- Exoplanet magnetic
fields are faint and hard to detect. But in April, 2023, two independent teams
found what appears to be the signature of a magnetic field produced by a rocky
planet orbiting a small, dim red dwarf star about 12 light-years away.
-
- The planet, “YZ
Ceti b”, is slightly smaller than Earth and likely too hot for life as we know
it. Yet finding a magnetic field on a rocky world could tell us more about how
magnetic fields form and how they impact a planet’s evolution and even its
suitability for life.
-
- We know from our
solar system that magnetic fields play an important role in affecting how a
planet loses or retains its atmosphere over time. We’re trying to answer the question: How
common are strong global magnetic fields on Earth-like planets?
-
- In our solar
system, Earth and the four giant planets, Jupiter, Saturn, Uranus and Neptune,
have significant magnetic fields. Mercury has only a faint field, and Mars very
likely had a more robust field in the past, which it lost for reasons that
aren’t completely understood.
-
- Planetary magnetic
fields are generated by an engine called a “dynamo”, which is built from molten
metal churning in a planet’s core. That churning produces electrical currents
that drive a magnetic field. On Earth and the four gas giants, this process is
strong enough to form a protective cocoon around the planet, deflecting charged
particles that would otherwise blow away the planets’ atmospheres.
-
- Magnetic fields
act like a shield from radiation. They
are very important for life.
Scientists suspect that many of the 5,000 known exoplanets
have magnetic fields, but detecting them is a different matter.
-
- In the 1970s,
astronomers surmised that when a planetary magnetic field interacts with the
planet’s host star, it might produce an observable spike in low-frequency radio
waves emitted by the star, known as auroral emissions. The timing of those
spikes, as seen from Earth, would depend on a planet’s location in its orbital
trek they’re like a periodic fingerprint that indirectly reveals the planet’s
presence.
-
- Even before the
first exoplanet discovery in 1992, people thought this would be a really good
way to look for exoplanets. The
technique proved difficult; no ironclad detections of exoplanetary magnetic
fields have been made before now, but there have been promising candidates.
-
- Atmospheric data
from four hot Jupiters, giant planets orbiting close to their stars, to get a
hint of magnetic fields in 2019. In 2021, a team used the Low Frequency Array
(LOFAR) telescope in the Netherlands to detect a radio signal linked to a
planetary magnetic field in the Tau Boötes system, 51 light-years from Earth.
-
- And later in 2021
astronomers detected ultraviolet emissions from a Neptune-like planet called
“HAT-P-11 b”, 123 light-years from Earth, that were suggestive of the planet’s
magnetosphere.
-
- In 2017,
astronomers found exactly the system they needed for the type of indirect
observation they’d hypothesized about for nearly 50 years. Three rocky planets
orbited the red dwarf “YZ Ceti”, a
cosmic stone’s throw away. The system’s proximity to our own makes its planets
convenient targets, especially YZ Ceti b, the innermost planet.
-
- Red dwarfs
typically have stronger magnetic fields than stars like our sun, which makes it
easier to identify the fingerprint of an orbiting planet’s magnetic field. Finding exoplanetary magnetic fields is
crucial for understanding how prevalent they are and how planets make
magnetism.
-
- In our solar
system, a dynamo seems to be key. But a dynamo might not be the only way to
generate a planetary magnetic field, especially in “super-Earths”, worlds that
are between Earth and Neptune in mass, which are among the most common type of
exoplanet spotted so far.
-
- Planetary
scientists are investigating whether heat fluctuations within a planet could do
the job inside worlds that have molten interiors but lack a solid core. Whether a magma ocean can produce a magnetic
field, noting that magma oceans should be pretty common in super-Earths.
-
- “GO-LoW” is an
idea that uses a fleet of thousands of small spacecraft to study radio waves
from exoplanets. Another idea is '”FARSIDE”, a proposed radio array from NASA
that would be placed on the far side of the moon, free of radio interference
from Earth.
-
- Will we find
Earths with Jupiter-sized fields, or Jupiters with Earth-sized fields?
-
- December 29,
2023 NEW
ROCKY PLANETS 4291
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