We have searched three hot molecular cores for submillimetre emission from the nucleic acid building block pyrimidine. We obtain upper limits to the total pyrimidine (beam‐averaged) column densities towards Sgr B2(N), Orion KL and W51 e1/e2 of 1.7 × 1014, 2.4 × 1014 and 3.4 × 1014 cm−2, respectively. The associated upper limits to the pyrimidine fractional abundances lie in the range (0.3−3) × 10−10. Implications of this result for interstellar organic chemistry, and for the prospects of detecting nitrogen heterocycles in general, are discussed briefly.

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Current Earth-like numerical dynamo simulations are able to reproduce many characteristics of the observed geomagnetic field. One notable exception is the geomagnetic octupolar component. Here we investigate whether a stably stratified layer at the top of the core, a missing ingredient in standard dynamo simulations, can explain the observed geomagnetic octupole. Through numerical simulations, we find that the existence of a stable layer has significant influence on the octupolar-to-dipolar ratio of the magnetic field. Particularly, we find that a 60-km stable layer with relatively strong stability or a 130-km layer with relatively weak stability are compatible with the observations, but a 350-km stable layer, as suggested by recent seismological evidence, is not compatible with Earth's octupole field over the past 10,000 years.Plain Language Summary Current computer models of Earth's magnetic field generation do a good job of reproducing the observed features of the field except for one large-scale component of the field: the octupole. In this paper we investigate whether including a layer at the top of the core that is stable to convection could help explain the observed octupole component of the field. We add such a layer to computer models of the geodynamo and find that it has significant influence on the octupolar component of the magnetic field. Particularly, we find that a 60-km thick stable layer that is relatively strongly stratified or a 130-km thick layer with relatively weak stratification are compatible with the observations, but a 350-km stable layer, as suggested by recent seismic evidence, is not compatible with Earth's octupole field over the past 10,000 years.

The Cassini Grand Finale orbits provided detailed observations of Saturn’s internal magnetic field. Unique characteristics of the observed field, such as its axisymmetry and power spectrum, provide constraints on dynamo processes deep in Saturn’s interior. Here, we use numerical dynamo simulations to explore what ingredients are necessary in a dynamo in order to produce the unique “Saturn‐like” surface magnetic field. We find that characteristics of Saturn’s magnetic field can be sensitive to properties of a stably stratified helium rain‐out layer and thermal perturbations at the top of the layer. Our best models suggest that a relatively thick stably stratified helium rain‐out layer may extend out to 70% of Saturn’s radius, likely imprinted with weak heat flux out of the equatorial region and strong heat flux out of high latitudes. These results may provide new constraints on stable stratification inside Saturn and its thermal evolution.

The latest generation of Galactic-plane surveys is enhancing our ability to study the effects of galactic environment upon the process of star formation. We present the first data from CO Heterodyne Inner Milky Way Plane Survey 2 (CHIMPS2). CHIMPS2 is a survey that will observe the Inner Galaxy, the Central Molecular Zone (CMZ), and a section of the Outer Galaxy in 12CO, 13CO, and C18O (J = 3 → 2) emission with the Heterodyne Array Receiver Program on the James Clerk Maxwell Telescope (JCMT). The first CHIMPS2 data presented here are a first look towards the CMZ in 12CO J = 3→2 and cover −3○ ≤ ℓ ≤ 5○ and ∣${b}$∣ ≤ 0${_{.}^{\circ}}$5 with angular resolution of 15 arcsec, velocity resolution of 1 km s−1, and rms $\Delta \, T_A ^\ast =$ 0.58 K at these resolutions. Such high-resolution observations of the CMZ will be a valuable data set for future studies, whilst complementing the existing Galactic Plane surveys, such as SEDIGISM, the ${Herschel}$ infrared Galactic Plane Survey, and ATLASGAL. In this paper, we discuss the survey plan, the current observations and data, as well as presenting position-position maps of the region. The position-velocity maps detect foreground spiral arms in both absorption and emission.