Gaia: science essays

108. White dwarf physics

Continuing on the subject of white dwarfs, I look at two other aspects that Gaia is helping to characterise. The white dwarf sequence in the colour-magnitude diagram reveals new insights into their composition and mass, and also into the physical processes accompanying their cooling over cosmological time scales.

23 January 2023

107. The white dwarf mass-radius relation

Theories of white dwarf interiors predict a relation between mass and radius that depends on their core composition and temperature. But accurate empirical confirmation is challenging. Results from Gaia DR2 show good agreement with predictions, confirming stellar degeneracy, while raising new questions.

16 January 2023

106. The remarkable cluster Westerlund 1

At a distance of about 4 kpc, the young compact star cluster Westerlund 1 contains many rare, evolved, high-mass stars, including red supergiants, yellow hypergiants, one of the largest known stars, and 24 Wolf-Rayet stars. Gaia is pinpointing its distance and its members, and resolving the puzzling question of its age.

9 January 2023

105. Wolf–Rayet stars

Wolf-Rayet stars are the final He-burning phase in the evolution of massive O stars, the last observable stage before core collapse. They are rare, but have an enormous influence on their environment. Distances were only poorly constrained before Gaia, which is now having a significant impact on their detailed understanding.

2 January 2023

104. Light deflection... by Jupiter

Gravitational light-bending by the Sun during the solar eclipse of 1919, around 1.7 arcsec at the solar limb, was the first observational confirmation of general relativity. Hipparcos measured light bending over the entire celestial sphere. Gaia has now measured light bending due to Jupiter, at around 10 milli-arcsec.

26 December 2022

103. Stellar rotation... for 3 million stars

The study of stellar rotation has been transformed within the past decade. Twenty years ago, the number of stars with measured rotation periods stood at 11,000. Kepler made a major advance by characterising photometric modulation for some 60,000. With Gaia DR3, more than three million are now known.

19 December 2022

102. The heart of the Milky Way

Compared to recent advances in understanding the details of our Milky Way's halo, the inner Galaxy has proven more elusive, complicated by the large distances involved. Amongst several advances being made with the Gaia data is the identification of the most ancient `proto-Galactic' component of our Galaxy.

12 December 2022

101. The nearest black hole

Gaia is enabling the discovery of two important classes of stellar-mass black holes in our Galaxy: isolated black holes, and those in binary systems which lack significant mass transfer. Amongst the latter, recently reported, is the nearest known black hole, at a distance of just 480 pc.

5 December 2022

100. The Fermi paradox

Following my last three essays, which looked at the historical debate about the existence of life on other worlds, and the search for anomalous stars which may be the first steps along the path for discovering alien civilisations, I look in more details at the Fermi paradox: if such civilisations exist, where are they?

28 November 2022

99. Searching for Dyson spheres

I look at one specific search for alien civilisations which is being assisted by Gaia: the search for so-called Dyson spheres. These are hypothetical megastructures that might encompass a star, capturing a significant fraction of its emitted energy, and satisfying that civilisation's continuously growing energy needs.

21 November 2022