New observations from the joint German-U.S. Stratospheric Observatory for Infrared Astronomy (SOFIA), the largest airborne observatory in the world, indicate that the nearby planetary system Epsilon Eridani has an architecture very similar to that of the Solar System.
Artist’s illustration of the Epsilon Eridani system. In the right foreground, the Jupiter-mass planet Epsilon Eridani b is shown orbiting its star at the outside edge of an asteroid belt. In the background can be seen another narrow asteroid or comet belt plus an outermost belt similar in size to our Solar System’s Kuiper Belt. The similarity of the structure of the Epsilon Eridani system to our Solar System is remarkable, although Epsilon Eridani is much younger than our Sun. Image credit: NASA / SOFIA / Lynette Cook.
The star Epsilon Eridani, also known as eps Eri, 18 Eri and HD 22049, is located 10.5 light-years away in the constellation Eridanus and is visible in the night skies with the naked eye.
The star’s temperature of 5,116 degrees Kelvin (almost 700 Kelvin cooler than the Sun) and low luminosity (34% solar) tell of a lower mass, approximately 83% that of the Sun.
Though its rotation speed appears similar to that of the Sun, the star is much younger, some 800 million years old, or one-fifth the age of the Sun.
The Epsilon Eridani system is the closest planetary system around a star similar to the young Sun and is a prime location to research how planets form around Sun-like stars.
It is also a popular locale in science fiction. It has been featured in novels by Isaac Asimov and Frank Herbert, among others. In the popular TV series Babylon 5 it is the location of the featured space station.
Illustration based on Spitzer observations of the inner and outer parts of the Epsilon Eridani system compared with the corresponding components of our Solar System. Image credit: NASA / JPL / Caltech / R. Hurt, SSC.
Previous studies indicate that Epsilon Eridani hosts a disk of planetary debris (can take the form of gas and dust as well as small rocky and icy bodies) and two planets, the Jupiter-mass planet Epsilon Eridani b (AEgir) and a low-mass planet candidate called Epsilon Eridani c.
Debris disks can be broad, continuous disks or concentrated into belts of debris, similar to our Solar System’s main asteroid belt and the Kuiper Belt.
With the new SOFIA images, a team of scientists led by Dr. Kate Su of the University of Arizona was able to distinguish between two theoretical models of the location of warm debris, such as dust and gas, in the Epsilon Eridani 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 the Solar System.
Using this model, the researchers 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, the authors ascertained that the warm material around Epsilon Eridani is in fact arranged like the first model suggests; it is in at least one narrow belt rather than in a broad continuous disk.
“The high spatial resolution of SOFIA combined with the unique wavelength coverage and impressive dynamic range of SOFIA’s FORCAST camera allowed us to resolve the warm emission around Epsilon Eridani, confirming the model that located the warm material near the Jovian planet’s orbit,” Dr. Su said.
“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 Epsilon Eridani, a much younger version of the Solar System, is put together like ours,” she said.
Details of the research were recently published in the Astronomical Journal. The article is also publicly available at arXiv.org.
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Kate Y. L. Su et al. 2017. The Inner 25 AU Debris Distribution in the epsilon Eri System. AJ 153, 226; doi: 10.3847/1538-3881/aa696b
