Gaia: science essays

148. Non-radial pulsators

I have discussed Gaia variables in several essays, focusing on Cepheids (43), on RR~Lyrae (45), their detection and classification (61), their distribution across the Hertzsprung--Russell diagram (62), and in the context of citizen science (132). Here I look at some new insights into the non-radial g-mode pulsators in the SPB and Gamma Dor class.

30 October 2023

147. Videos and visualisations: part 2

In essay 54, in January 2022, I gave links to some of the videos, animations, visualisations, and `fly-throughs' made to illustrate the science that Gaia is addressing. DR3 was released in June 2022, and many new explanatory videos have been made since. This is an introduction to some of the many video animations and illustrations that now exist.

23 October 2023

146. Benford's law - and astrometry

A curious property of many collections of numbers, including naturally occurring data, is that the leading digits are not uniformly distributed, but are skewed toward smaller values. As Benford's law, it has been considered in many contexts, including identifying suspicious accounting. I consider it here in the context of the Gaia DR2 parallaxes.

16 October 2023

145. Spectroscopic binaries

Included in the DR3 data release are some 180,000 single-lined spectroscopic binaries, a colossal increase in numbers enabling the study of many aspects of short-period binaries. I look here at some new insights into orbit circularisation, where the Gaia data point to the process operating most efficiently in the pre-main sequence evolutionary phase.

9 October 2023

144. How many open clusters?

Gaia is transforming the study of open clusters. Pre-2016, some 3000 clusters had been identified. But Gaia has shown that more than half of these are unreal, being simply asterisms. In their place, from nearly 25,000 new discoveries reported with Gaia (some duplicated), there are today nearly 14,000 unique clusters known in our Galaxy.

2 October 2023

143. Gaia's maps of the Milky Way

The ESA-Gaia `Image of the Week', on the first anniversary of the 34-month Data Release~3 (DR3), 13 June 2023, was a remarkable multi-dimensional map of the Milky Way, produced by the many members of the Data Processing and Analysis Consortium (DPAC). I'm showing these 10 splendid sky plots again here.

25 September 2023

142. Gaia and the search for axions

Gaia's contribution to understanding the distribution of dark matter follows from studies of the stellar halo population, Galactic kinematics, and stellar streams. Studies have also begun to place specific constraints on the properties of dark matter, for example if it is comprised of axions. I provide an overview of the various approaches.

18 September 2023

141. White dwarf pulsars

White dwarfs have featured in a number of my previous essays. Gaia is providing well-defined samples in the solar neighbourhood, with more than 260,000 from Gaia DR2. I look here at the recent discovery of the new type of `white dwarf pulsars'. With just two members of this exclusive class, Gaia is contributing to their understanding,

11 September 2023

140. Cataclysmic variables

Cataclysmic variables are interacting binaries containing a white dwarf accreting from a donor star. Their space density places strong constraints on models of their formation and evolution, and has revealed major discrepancies between observations and theory. New and improved space densities are becoming available with Gaia.

4 September 2023

139. Quadruple star systems

How common are quadruple star systems? How is Gaia discovering and characterising new systems, and what do they tell us about the star-formation process? One specific quadruple system is providing insights into the cooling and crystallisation of white dwarf interiors, and another is providing hints about the origin of type Ia supernovae.

28 August 2023