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Sally Dodson-Robinson, associate professor of physics and
astronomy, is leading UD’s role in an international space mission called
“Twinkle” that aims to answer some of humanity’s greatest questions,
including the age-old “Is anyone else out there?”
Photos taken by
NASA’s Voyager 2 spacecraft mesmerized Sally Dodson-Robinson as a child —
from the striking closeups of Saturn’s colorful rings to icy-blue
Neptune with the dark spot where a storm the size of Earth was swirling
“I would look at them and imagine going there and visiting and
thinking how amazing that would be,” said Dodson-Robinson, associate
professor of physics and astronomy at the University of Delaware.
When those photos were taken more than 30 years ago, the only
planetary system we really had in mind was Earth and its neighbors.
“But astronomers were asking, ‘Why should we be special?’ and their
predictions were completely right,” Dodson-Robinson said. “The first
exoplanet was discovered when I was in high school, and in grad school, I
got to see this revolution, from 30 planets found, to thousands that
people now know about today. It’s been exciting to watch this revolution
in astronomy and to be a part of it.”
Dodson-Robinson is now leading UD’s participation in an international
space mission called “Twinkle” that aims to answer some of humanity’s
greatest questions, including the age-old “Is anyone else out there?” It
is the first space science mission of Blue Skies Space Ltd., which was
co-founded by researchers at University College London in the United
Kingdom to deliver independent satellites providing high-quality data to
the global scientific community. The Twinkle mission involves
scientists from 15 universities and counting, in North America, Europe
and the Asia-Pacific region. This video of the Twinkle mission provides
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Dodson-Robinson’s involvement in Twinkle is being supported by UD’s Department of Physics and Astronomy and by a generous donation from the Miles Family Endowment.
Once launched into low-Earth orbit in 2024, the Twinkle satellite
will capture new data on thousands of celestial targets, including
exoplanets — the planets beyond our solar system orbiting distant
sun-like stars. The satellite will carry a spectrometer that measures
and records the light emitted, absorbed and reflected by objects in
space, from stars and planets and moons, to comets and asteroids. This
includes light we can see, and light of slightly longer wavelength in
the infrared spectrum, which is invisible to us.
Scientists can detect exoplanets trillions of miles beyond our solar
system by analyzing the light signatures of stars. Telescopes in space,
such as NASA’s Transiting Exoplanet Survey Satellite (TESS), look for
changes in the light emitted by a star. As exoplanets move along their
orbit, they will block some of the light from their host star when they
pass in front of the telescope’s line of sight, and the telescope will
record that dip in brightness.
Dodson-Robinson wants to use Twinkle’s light-spectrum data to develop
a complementary way to search for Earth-like exoplanets and involve UD
students in the process. (Besides her complex research, Dodson-Robinson
teaches a course called “Introduction to Astronomy.”)
Her focus is on a star’s radial velocity — the ever-so slight
elliptical movements of a star in response to a planet’s gravitational
tug. This wobbling, as if the star is using a hula hoop, affects the
star’s light signature. A star moving toward us during that wobble has
light of slightly shorter wavelength, which reads bluer in color, versus
a star moving slightly away from us, which will have a longer
wavelength and thus be redder.
“The surface of a star is a very active place – bubbles arise from
convection, there are flares, areas of strong magnetic fields, the
stalling of gases. If we’re looking at motion,” Dodson-Robinson said,
“how do you separate out this ‘noise’ versus the gravitational pull of a
planet? That’s a big challenge because the wobbling of stars caused by
the tugs from small, Earth-like exoplanets are minuscule and can easily
be masked by this noise.”
Twinkle’s mission is explained in this video provided by Blue Skies Space Ltd.
The hypothesis she’s working on is that at some wavelengths, or
colors of light, you will get more “noise,” or up-and-down motions,
reflecting natural activity on a star’s surface rather than an
“My hope is that, using Twinkle’s data, we can monitor specific
colors and by removing the noise, we can develop models of this stellar
variability and find Earth 2.0 right here from the ground,”
Dodson-Robinson said. “Many exoplanets have been found from the ground,
but not Earth-like ones orbiting sun-like stars.”
Twinkle is expected to provide more than 70,000 hours — nearly eight
years — of observational data once it launches in 2024. Robinson’s work
will complement other Twinkle research on the atmospheres of exoplanets
to determine their habitability.
Finding another Earth out there will take extensive searching and
validation. How close is a prospective candidate to its sun-like star?
Does it have an atmosphere rich in oxygen, an ozone layer for protection
against ultraviolet radiation, liquid water on the surface, and so on?
Such “checklists” for livability are very involved, Dodson-Robinson
said, driving intense climate modeling efforts in the search for other
planets that can sustain life.
But planets have always enthralled Dodson-Robinson. Recently, the
American Astronomical Society invited her to write about her specialty —
giant planets — for their monograph series. The Origins of Giant Planets,
the first volume published in December 2021, serves as both an
introduction for astronomy students and postdoctoral researchers, as
well as a useful reference for senior professionals in the field. The
society highlights the book in an interview now available on YouTube.
What is a giant planet? In our solar system, they include Jupiter,
Saturn, Uranus and Neptune. Rather than having a large, rock body like
Earth, these planets are huge balls of gas surrounding small, dense
cores. You couldn’t really stand on them because their surfaces are not
solid. Yet they have had an outsized role in controlling the growth,
composition and orbits of their smaller, potentially habitable
Research has suggested that as Neptune grew, it may have starved the
solar system of a supply of solids that could have formed a super-Earth,
and as Jupiter grew, it directed asteroids into the inner solar system,
providing a water source for early Earth — and those are just a few
examples, Dodson-Robinson said.
“It will be impossible to unravel the formation of any habitable
world without characterizing its giant-planet neighbors,” she said.
“While they may be gas balls, there are good reasons to include giant
planets in the search for extraterrestrial life.”
Sarah (Sally) Dodson-Robinson received her doctorate in astronomy and
astrophysics from the University of California at Santa Cruz in 2008 and
afterward took a Spitzer Postdoctoral Fellowship at the NASA Exoplanet
Science Institute. An associate professor of physics and astronomy at
UD, Dodson-Robinson won the American Astronomical Society’s Annie Jump
Cannon Award for her contributions to the study of planet formation. She
conducts numerical simulations of the chemical and dynamical evolution
of planet-forming disks and participates in observational studies of
debris disks. She also develops and tests methods for distinguishing
exoplanet discoveries from stellar noise.
Article by Tracey Bryant; Photos by Kathy F. AtkinsonPublished May 24, 2022