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ARIUSCAPRICORNUS2.0%
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ORIONSaturnplanets or, according to the new study’s
researchers, primordial black holes.
“Capture of a free-f loating planet is
a leading explanation for the origin of
Planet Nine,” wrote the authors in the
study, “and we show that the probability
of capturing a primordial black hole
instead is comparable.”
According to Konstantin Batygin of
Caltech, who has been a primary pro-
ponent of the Planet Nine hypothesis
but was not involved in the new study,
it’s definitely possible that a primordial
black hole could replace Planet Nine
in their model. But that doesn’t meanit should. “The important thing to
understand here is that all that the cal-
culations can tell is the mass of Planet
Nine, not its composition,” Batygin tells
Astronomy. “So, in principle, Planet
Nine can be a planet, a potato, a black
hole, a hamburger, et cetera, as long as
its orbital parameters are right.”
Though Batygin isn’t convinced a
primordial black hole roaming the
outer solar system would be a more
natural fit than Planet Nine, he admits
he’s hesitant to write off the new idea
completely. Or, as he put it: “I always
like to keep an open mind.” — JAKE PARKSNESTED BLACK HOLES
New research suggests the disks
of supermassive black holes could
have smaller black holes merging
within them. If true, this could help
explain the formation of the
roughly 50-solar-mass black holes
found by the Laser Interferometer
Gravitational-wave Observatory.BON VOYAGE
Voyager 2 passed into interstellar
space in November 2018.
Scientists have described the
milestone in five recent papers,
including one that found
surprising signs of charged
particles “leaking” from the
heliosphere, the bubble of space
carved out by the Sun’s influence.CASE-ING PLANETS
The European Space Agency’s
ARIEL mission, planned for launch
in 2028, will closely study the
atmospheres of about 1,
exoplanets. Aboard the spacecraft,
NASA’s CASE instrument will help
determine whether these alien
skies are cloudy, hazy, or clear.STARLINK GROWS
On November 11, SpaceX launched
its second batch of 60 Starlink
satellites into orbit; they are
intended to further the company’s
goal of providing global internet
coverage through a combined
fleet of about 12,000 total satellites
by the mid-2020s.SMALLEST DWARF
New observations show asteroid
Hygiea, the fourth-largest object
in the main belt, is spherical. This
could make it the solar system’s
smallest known dwarf planet.NOT SO GOLDILOCKS
Rice University scientists modeled
how stars’ extended magnetic
fields impact the habitability of
close-in “Goldilocks” exoplanets,
finding the fields could strip
a planet’s life-protecting
atmosphere away in as little
as 100 million years. — J.P.QUICK
TAKE S
WWW.ASTRONOMY.COM 9
A ZODIACAL JOURNEY. Saturn takes
29.5 years to circle the Sun, so it
typically spends a lot of time in
each constellation it traverses.
It crosses from Sagittarius to
Capricornus in March 2020,
ending a 28-month foray
through the Archer’s stars. But
its longest stretch comes within
the confines of Virgo the Maiden.
The chart shows the percentage of
time the ringed planet will reside
in each constellation from March
2020 until it returns to the same
position three orbits from now, in
July 2108. — RICHARD TALCOTTFAST FACT
Saturn’s orbit tilts 2.5° to the ecliptic,
enough that it slices through two
non-zodiacal constellations: Cetus and Orion.THE RINGED
WORLD WANDERS
The speed, in mph (6 million km/h), at which
astronomers recently clocked a star fleeing
our galaxy. Researchers believe the star’s
speed results from a close encounter with the
Milky Way’s supermassive black hole.
million
LEARN MORE ABOUT THESE STORIES AT
http://www.astronomy.com/newsASTRONOMY:^RICK^ JOHNSON