* Astronomy

Members Login

Post Info

TOPIC: WISE J072003.20-084651.2

Blobrana

L

Posts: 131433

Date: Feb 18 14:32 2015

RE: WISE J072003.20-084651.2	Permalink

Alien star system buzzed the Sun An alien star passed through our Solar System just 70,000 years ago, astronomers have announced. No other star is known to have approached this close to us. Read more __________________

Blobrana

L

Posts: 131433

Date: Feb 17 05:25 2015

Scholz's star	Permalink

Title: The Closest Known Flyby of a Star to the Solar System Author: Eric E. Mamajek, Scott A. Barenfeld, Valentin D. Ivanov, Alexei Y. Kniazev, Petri Vaisanen, Yuri Beletsky, Henri M. J. Boffin Passing stars can perturb the Oort Cloud, triggering comet showers and potentially extinction events on Earth. We combine velocity measurements for the recently discovered, nearby, low-mass binary system WISE J072003.20-084651.2 ("Scholz's star") to calculate its past trajectory. Integrating the Galactic orbits of this ~0.15 solar mass binary system and the Sun, we find that the binary passed within only 52+23-14 kAU (0.25+0.11-0.07 parsec) of the Sun 70+15-10 kya (1sgma uncertainties), i.e. within the outer Oort Cloud. This is the closest known encounter of a star to our solar system with a well-constrained distance and velocity. Previous work suggests that flybys within 0.25 pc occur infrequently (~0.1 Myr-1). We show that given the low mass and high velocity of the binary system, the encounter was dynamically weak. Using the best available astrometry, our simulations suggest that the probability that the star penetrated the outer Oort Cloud is ~98%, but the probability of penetrating the dynamically active inner Oort Cloud (<20 kAU) is ~10-4 . While the flyby of this system likely caused negligible impact on the flux of long-period comets, the recent discovery of this binary highlights that dynamically important Oort Cloud perturbers may be lurking among nearby stars. Read more (39kb, PDF) __________________

Blobrana

L

Posts: 131433

Date: Oct 17 05:41 2014

WISE J072003.20-084651.2	Permalink

Title: WISE J072003.20-084651.2: An Old and Active M9.5 + T5 Spectral Binary 6 pc from the Sun Author: Adam J. Burgasser (UCSD), Michael Gillon (U. Liege), Carl Melis (UCSD), Brendan P. Bowler (Caltech), Eric L. Michelsen (UCSD), Daniella Bardalez Gagliuffi (UCSD), Christopher R. Gelino (Caltech/NASA ExoSCI), E. Jehin (U. Liege), L. Delrez (U. Liege), J. Manfroid (U. Liege), Cullen H. Blake (U. Pennsylvania) We report observations of the recently discovered, nearby late-M dwarf WISE J072003.20-084651.2. Astrometric measurements obtained with TRAPPIST improve the distance measurement to 6.0±1.0 pc and confirm the low tangential velocity (3.5±0.6 km/s) reported by Scholz. Low-resolution optical spectroscopy indicates a spectral type of M9.5 and prominent H-alpha emission (<LH-alpha/Lbol> = -4.68±0.06), but no evidence of subsolar metallicity or Li I absorption. Near-infrared spectroscopy reveals subtle peculiarities indicating the presence of a T5 binary companion, and high-resolution laser guide star adaptive optics imaging reveals a faint (DeltaH = 4.1) candidate source 0"14 (0.8 AU) from the primary. We measure a stable radial velocity of +83.8±0.3 km/s, indicative of old disk kinematics and consistent with the angular separation of the possible companion. We measure a projected rotational velocity of v sin i = 8.0±0.5 km/s, and find evidence of low-level variability (~1.5%) in a 13-day TRAPPIST lightcurve, but cannot robustly constrain the rotational period. We also observe episodic changes in brightness (1-2%) and occasional flare bursts (4-8%) with a 0.8% duty cycle, and order-of-magnitude variations in H-alpha line strength. Combined, these observations reveal WISE J0720-0846 to be an old, very low-mass binary whose components straddle the hydrogen burning minimum mass, and whose primary is a relatively rapid rotator and magnetically active. It is one of only two known binaries among late M dwarfs within 10 pc of the Sun, both harbouring a mid T-type brown dwarf companion. While this specific configuration is rare (1.4% probability), roughly 25% of binary companions to late-type M dwarfs in the local population are likely low-temperature T or Y brown dwarfs. Read more (1036kb, PDF) __________________

Page 1 of 1 sorted by

Create your own FREE Forum
Report Abuse