The so-called extreme trans-Neptunian objects (ETNOs) are orbiting the Sun at heliocentric distances larger than 150 AUs, and their discovery a decade ago was soon recognized as a turning point in our knowledge of the outer Solar System. The currently tally stands at 21 ETNOs, and only one, Sedna, has been spectroscopically observed. In the last years several studies have suggested that the dynamical properties of the ETNOs could be better explained if one or several planets of several Earth masses are orbiting the Sun at hundreds of AUs. In 2016, Brown and Batygin used the orbits of seven ETNOs to predict the existence of a super-Earth in the sub-Neptunian mass range orbiting the Sun at 700 AUs: this is known as the “Planet Nine” hypothesis. Among these seven ETNOs, the pair 2004 VN112 – 2013 RF98 clearly stands out, the two objects having almost identical orbits with an angular separation between their directions of perihelia and orbital poles extremely small. This suggests a common dynamical origin: in September 2016 we used the OSIRIS camera-spectrograph at the 10.4m GTC telescope to obtain visible spectra of this pair of ETNOs to unravel their physical nature. The obtained spectral slopes for the two objects were almost identical, 12 ± 2 %/1000Å and 15 ± 2 %/1000Å for 2004 VN112 and 2013 RF98, respectively, and consistent with those obtained by other authors for 2000 CR105 (14%) and 2012 VN113 (13%) using photometric data. These values indicate the possible presence of amorphous silicates in the surface of these objects, as is the case of Trojans or Centaurs, but never dominated by complex organics. In contrast, Sedna presents a value of 42%, having a ultra-red surface material, typically organics, very different from the rest of ETNOs. These five objects belong to the group of seven used to present the Planet Nine hypothesis, suggesting that they all may share a common region of origin, with the exception of Sedna, which is thought to come from the inner Oort Cloud. Therefore, the very similar spectral slopes for the pair 2004 VN112 – 2013 RF98 indicated a common physical origin, suggesting the possibility that this pair could have been a binary asteroid that was perturbed in the past after an encounter with a more massive object. To test the viability of this hypothesis we performed thousands of numerical experiments, analyzing the evolution with time of the angular separation between the orbital poles of the two objects. Our results favors a scenario in which 2004 VN112 – 2013 RF98 were once a binary asteroid that became unbound after a relatively recent gravitational encounter (5 – 10 Myr) with a planet with mass in the range 10-20 Earth masses, moving in an eccentric (0.1-0.4) and inclined (20-50 degrees) orbit, with semi-major axis of 300-600 AU.
Advertised on
References
It may interest you
-
The cosmic evolution of the barred galaxy population provides key information about the secular evolution of galaxies and the settling of rotationally dominated discs. We study the bar fraction in the SMACSJ0723.37323 (SMACS0723) cluster of galaxies at z = 0.39 using the Early Release Observations obtained with the NIRCam instrument mounted on the JWST telescope. We visually inspected all cluster member galaxies using the images from the NIRCam F200W filter. We classified the galaxies into ellipticals and discs and determine the presence of a bar. The cluster member selection was based on aAdvertised on
-
The transient Swift J1727.8-162 is the latest member of the X-ray binary black hole family to be discovered. They are formed by a black hole and a low-mass star whose gas is stripped off and accreted to the black hole via an accretion disc. The high temperature of the accretion disc makes it shine in all energy bands up to X-rays, and is particularly bright during epochs known as outbursts. In this novel study, published just a few months after the discovery of the system, we present 20 epochs of optical spectroscopy obtained with the GTC-10.4m telescope. The spectra cover the main accretionAdvertised on
-
Stellar ages are key to several fields of astrophysics such as exoplanet research, galactic-archeology, and of course stellar physics. Obtaining the ages of stars is however not straightforward and requires stellar modeling. The most widely used technique only requires stellar colors or temperature and surface gravity, but the uncertainties are quite large. This technique is most efficient for stars belonging to clusters, as they were born from the same molecular cloud and share the same ages. In the last decades, based on the study of stellar acoustic waves, asteroseismology became the mostAdvertised on