YSM Issue 95.2

use the transit method, a detection technique
where astronomers measure how much light a
planet blocks as it passes or transits its host star.
“You get the size of the planet by looking at how
much of the starlight has been blocked, you get
the period by seeing how often it happens, and
you get information about the orbit from the
duration of the transit,” said Greg Laughlin,
Yale professor of astronomy.
Over the past decade, a lot of effort has gone
into measuring the angles between planetary
orbits and the stars’ equators. Enough of these
measurements have been collected such that
patterns are now starting to emerge. One
of the most interesting patterns is that stars
that are more massive than the Sun by about
twenty or thirty percent tend to show planets
that are badly misaligned, whereas the stars
that are less massive than the Sun tend to
show better alignment.
Extrapolate Your Jupiter’s Evolutionary
History
Researchers Malena Rice and Greg Laughlin
found that when the planet’s orbit had a higher
eccentricity, there was more misalignment.
This finding aligns with the idea that the planets
get to their current locations through scattering
rather than steady, slow disk migration. “That
doesn’t mean that high-eccentricity migration
is the only process that could take place, but is
probably dominant—if you assume that it’s the
only mechanism at play, it is consistent with all
of our observations,” Rice said.
For now, they need more data, but what
they’ve collected so far is promising, confirming
that disks should be aligned with their hosts. If
wide-orbiting warm Jupiter planets had started
in misaligned orbits, they would continue to
have those peculiar orbits since they orbit too
far from their host star to be realigned over
time. So, the fact that we mostly see aligned
systems, particularly on wider orbits, further
indicates that something drastic happened to
the closer-orbiting hot Jupiters after they had
all formed to become misaligned.
This result isn’t what would be expected, as it
implies that these hot Jupiters rely on random
events rather than a systematic process. “I had
assumed either that the planets are forming in
situ or that they're migrating, and I hadn't really
appreciated the fact that we can explain the
distribution simply through chaotic scattering
and planet-planet interactions, kinds of oneoff
events,” Laughlin said.
But what advantages does characterizing
these planetary systems bring? Having
two well-studied types of planetary systems
is much better than just one, especially when
those two systems are fringe-type oddballs on
each end of the spectrum. From these systems,
one can interpolate between the two extremes
and extrapolate the evolutionary histories of
more average systems. “What’s really exciting
about this paper is that it gives us really good
reason to believe that this very dramatic set of
events, which are
unlike anything
that happened
in the solar
system, is actually
happening on a
regular basis,” Rice
said. “It’s providing
a completely new
perspective on
the different ways
that planetary
systems form;
we are starting to
piece together the
possibilities and
move away from
being biased by
our one exquisitely
detailed data
point.” ■
A R T B Y U R I E L T E A G U E
ABOUT THE AUTHOR
BRIANNA FERNANDEZ
BRIANNA FERNANDEZ is a junior in Pierson College studying astronomy and earth and planetary
sciences. In addition to writing for YSM, she is one of the magazine’s layout editors. Outside of YSM,
she researches exoplanets with Professor Debra Fischer and advocates for incarceration-impacted
individuals with the Yale Undergraduate Prison Project.
THE AUTHOR WOULD LIKE TO THANK Malena Rice and Greg Laughlin for their time and enthusiasm
in sharing their research.
FURTHER READING
Rice, Malena, et al. “Origins of Hot Jupiters from the Stellar Obliquity Distribution.” The Astrophysical
Journal Letters, 926(2), 2022, https://doi.org/10.3847/2041-8213/ac502d.
Astronomy
FOCUS
www.yalescientific.org
May 2022 Yale Scientific Magazine 15