Volume 2 Issue 9, September 2018

The National Astronomical Observatory of Japan has been working to increase public familiarity with astronomy. Here we introduce our outreach activities, including the development of interactive tools that make NAOJ data visible to the public.

Understanding how and why star formation turns off in massive galaxies is a major challenge for studies of galaxy evolution. Many theoretical explanations have been proposed, but a definitive consensus is yet to be reached.

An exoplanet as hot as a star challenges our understanding of how planets evolve under extreme conditions. Observations with the CARMENES spectrograph provide clues about the atmospheric properties of this outstanding planet.

The Andromeda galaxy’s stellar halo and disk show signs of an active recent merger history. Recent work suggests that most of the disturbances in Andromeda’s disk and the inner halo may be due to a single merger event.

Noble gas abundances measured in the oldest calcium–aluminium-rich inclusions (CAIs) reveal a burst of intense solar irradiation early in the Solar System’s history, not recorded by CAIs that formed later. This result is consistent with a T Tauri phase for the Sun.

Using high-resolution spectra, the CARMENES survey detects a hydrogen atmosphere around KELT-9b, the hottest exoplanet ever discovered. This hydrogen envelope almost entirely fills the Roche lobe, indicating intense atmospheric loss.

A method of atmospheric retrieval for exoplanets that uses supervised ‘random forest’ machine learning, less time-consuming than standard techniques, is presented. Tests on Hubble spectra of WASP-12b give results consistent with standard atmospheric retrievals.

In simulations, young massive star clusters in the present-day Universe form naturally in giant molecular clouds, despite the influence of radiative feedback. The same process occurred in earlier epochs, for instance, when globular clusters were born.

Massive binary star Eta Carinae drives the strongest colliding wind shock in the solar neighbourhood. Using NuSTAR and XMM-Newton data, Eta Car has now been convincingly shown to accelerate non-thermal particles, contributing to the Galactic cosmic ray flux.

M31’s massive and metal-rich stellar halo appears to indicate that a single dominant merger with a large galaxy took place about 2 Gyr ago, co-temporal with M31’s global burst of star formation. M32 is likely to be the stripped core of the disrupted galaxy.

The strong gravitational lensing signal around the massive cluster PSZ2 G099.86+58.45 indicates environment matter density in notable excess of the cosmological mean and implies that enhancing mechanisms around high-mass halos can be very effective.

Late-time optical and near-infrared observations of the binary neutron star merger GW170817 are at odds with kilonova models but match a Gaussian-structured relativistic jet, which would have launched a high-luminosity short gamma-ray burst to an aligned observer.

HaloSat, NASA’s first astrophysics-focused CubeSat mission — the size of a small briefcase — will survey the Milky Way’s halo in order to assess its complement of hot baryons, explains Principal Investigator Philip Kaaret.