Using data from NASA’s Stratospheric Observatory for Infrared
Astronomy (SOFIA), astronomers confirm that the nearby Epsilon Eridani
system has an architecture remarkably similar to that of our solar
system.
The star Epsilon Eridani, eps Eri for short, is located 10.5
light-years away in the southern hemisphere of the constellation
Eridanus. It is the closest planetary system around a star similar to
the early sun. It is a prime location to research how planets form
around stars like our sun, and is also the storied location of the
Babylon 5 space station in the science fictional television series of
the same name.
Previous studies indicate that eps Eri has a debris disk, which is
the name astronomers give to leftover material still orbiting a star
after planetary construction has completed. The debris can take the form
of gas and dust, as well as small rocky and icy bodies. Debris disks
can be broad, continuous disks or concentrated into belts of debris,
similar to our solar system’s asteroid belt and the Kuiper Belt – the
region beyond Neptune where hundreds of thousands of icy-rocky objects
reside. Furthermore, careful measurements of the motion of eps Eri
indicates that a planet with nearly the same mass as Jupiter circles the
star at a distance comparable to Jupiter’s distance from the Sun.
Using new SOFIA images, Kate Su of the University of Arizona and her
research team were able to distinguish between two theoretical models of
the location of warm debris, such as dust and gas, in the eps Eri
system. These models were based on prior data obtained with NASA’s
Spitzer space telescope.
One model indicates that warm material is in two narrow rings of
debris, which would correspond respectively to the positions of the
asteroid belt and the orbit of Uranus in our solar system. Using this
model, theorists indicate that the largest planet in a planetary system
might normally be associated with an adjacent debris belt.
The other model attributes the warm material to dust originating in
the outer Kuiper-Belt-like zone and filling in a disk of debris toward
the central star. In this model, the warm material is in a broad disk,
and is not concentrated into asteroid belt-like rings nor is it
associated with any planets in the inner region.
Using SOFIA, Su and her team ascertained that the warm material
around eps Eri is in fact arranged like the first model suggests; it is
in at least one narrow belt rather than in a broad continuous disk.
These observations were possible because SOFIA has a larger telescope
diameter than Spitzer, 100 inches (2.5 meters) in diameter compared to
Spitzer’s 33.5 inches (0.85 meters), which allowed the team onboard
SOFIA to discern details that are three times smaller than what could be
seen with Spitzer. Additionally, SOFIA’s powerful mid-infrared camera
called FORCAST, the Faint Object infraRed CAmera for the SOFIA
Telescope, allowed the team to study the strongest infrared emission
from the warm material around eps Eri, at wavelengths between 25-40
microns, which are undetectable by ground-based observatories.
“The high spatial resolution of SOFIA combined with the unique
wavelength coverage and impressive dynamic range of the FORCAST camera
allowed us to resolve the warm emission around eps Eri, confirming the
model that located the warm material near the Jovian planet’s orbit,”
said Su. “Furthermore, a planetary mass object is needed to stop the
sheet of dust from the outer zone, similar to Neptune’s role in our
solar system. It really is impressive how eps Eri, a much younger
version of our solar system, is put together like ours.”
Wednesday, May 3, 2017
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