- 4547 - ROGUE PLANETS - roaming free of a star's gravity? - JamesWebb telescope discovers six new 'rogue worlds' that provide clues to star formation. Rogue planets, or free-floating planetary-mass objects , are planet-sized objects that either formed in interstellar space or were part of a planetary system before gravitational perturbations kicked them out.
--------------------------- 4547 - ROGUE PLANETS - roaming free of a star's gravity?
- Since these rogue planets were first
observed in 2000, astronomers have detected hundreds of candidates that are
untethered to any particular star and float through the interstellar medium
(ISM) of our galaxy. In fact, some scientists estimate that there could be as
many as 2 trillion rogue planets (or more) wandering through the Milky Way
alone.
-
- Astronomers discovered six rogue planet
candidates in an unlikely spot. The planets, which include the lightest rogue
planet ever identified (with a debris disk around it), were spotted during
Webb's deepest survey of the young nebula NGC 1333, a star-forming cluster
about a thousand light-years away in the Perseus constellation. These planets
could teach astronomers a great deal about the formation process of stars and
planets.
-
- Most of the rogue planets detected to date
were discovered using “gravitational microlensing”, while others were detected
via “Direct Imaging”. The former method relies on "lensing events,"
where the gravitational force of massive objects alters the curvature of
spacetime around them and amplifies light from more distant objects. The latter
consists of spotting brown dwarfs (objects that straddle the line between
planets and stars) and massive planets directly by detecting the infrared
radiation produced within their atmospheres.
-
- Using data from Webb's Near-Infrared Imager
and Slitless Spectrograph (NIRISS), astronomers
measured the spectrum of every object in the observed portion of the
star cluster. This allowed them to reanalyze spectra from 19 previously
observed brown dwarfs and led to the discovery of a new brown dwarf with a
planetary-mass companion.
-
- This latter observation was a rare find that
already challenges theories of how binary systems form. But the real kicker was
the detection of six planets with five to 10 times the mass of Jupiter. This means these six candidates are among the
lowest-mass rogue planets ever found that formed through the same process as
brown dwarfs and stars.
-
- The fact that Webb's observations revealed
no objects lower than five Jupiter masses (which it is sensitive enough to
detect) is a strong indication that stellar objects lighter than are more
likely to form the way planets do.
-
- The most intriguing of the rogue planets
was also the lightest: an estimated five Jupiter masses (about 1,600 Earths).
Since dust and gas generally fall into a disk during the early stages of star
formation, the presence of this debris ring around the one planet strongly
suggests that it formed in the same way stars do.
-
- However, planetary systems also form from
debris disks (circumsolar disks), which suggests that these objects may be able
to form their own satellites. This suggests that these massive planets could be
a nursery for a miniature planet system like our solar system, but on a much
smaller scale.
-
- These observations confirm that nature
produces planetary mass objects in at least two different ways, from the
contraction of a cloud of gas and dust, the way stars form, and in disks of gas
and dust around young stars, as Jupiter in our own solar system did.
-
- The new Webb observations indicate that
such bodies account for about 10% of celestial bodies in the targeted
cluster. Current estimates place the
number of stars in our galaxy between 100 and 400 billion stars and the number
of planets between 800 billion and 3.2 trillion. At 10%, that would suggest
that there are anywhere from 90 to 360 billion rogue worlds floating out there.
-
September 2, 2024 ROGUE
PLANETS - roaming free of a star's gravity? 4547
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--------------------- --- Tuesday, September 3,
2024
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