Gaia: science essays

54. Animations, stereos and fly-throughs

It is a challenge to explain the scientific importance of astrometry to a wider public. But the measurement of stellar distances and space motions in the vast quantities and accuracies provided by Gaia, is yielding compelling animations, stereo images, and fly-throughs of our Galaxy. I provide some examples.

10 January 2022

53. The scientific case for Gaia in 2000

With the steady flow of scientific results now coming from the Gaia satellite, I look back at the mission's scientific case, prepared during the period 1997–2000. This formed part of the Concept & Technology Study Report, which was used as the basis for ESA's advisory structure's selection of the mission in 2000.

3 January 2022

52. Interplanetary navigation

Spacecraft sent out to orbit, land on, or simply fly past the planets and other bodies of our solar system rely on interplanetary navigation. At the basis of knowing both the target object's orbit, and the rendezvous vehicle's orbit, are accurate star positions. The recent spectacular fly-by of Ultima Thule used the latest Gaia results.

27 December 2021

51. Asteroseismology - and star distances

Given that stars are usually seen as point sources, it is perhaps surprising that we can say anything at all about their internal structure and physical processes. The observational effects of shock waves propagating through them provides an important tool for probing their interiors. And distances provide an important constraint.

20 December 2021

50. The DIVA project

As the Hipparcos project neared its completion in the mid-1990s, several groups around the world started to discuss possible follow-on missions. DIVA was an initiative led by German scientists, intended as a fast and cheap mission, exploiting advancing technology, and providing a bridge to the results expected from Gaia.

13 December 2021

49. Galactic rotation

Stars in the disk of our Galaxy rotate around its centre. Our Sun participates in this general motion, orbiting the Galaxy in about 250 million years. Much about our Galaxy's origin and dynamics relies on an understanding of the detailed form of its rotation. Many issues complicate its determination, which Gaia is advancing.

6 December 2021

48. The risk of asteroid impacts

From time to time, the topic of near-Earth asteroids, and their potential for impact hazards to our planet, hits the scientific and popular headlines. Although still unprecedented, Gaia's original target accuracies could have predicted likely impactors 100 years hence, contributing even more to impact assessment and mitigation.

29 November 2021

47. The iterative solution: implementation

Formulating the mathematical description of the astrometric solution was one part of the challenge for the Gaia data processing. But its actual computer implementation was quite another. The solution adopted is to execute four distinct data 'blocks', which are optimised in memory and evaluated in a cyclic sequence until convergence.

22 November 2021

46. The iterative solution: formulation

Gaia gathers an enormous quantity of observations of a vast numbers of stars over several years. The goal of the data analysis on the ground is straightforward in principle: like solving a giant celestial jigsaw, the task is to find the astrometric parameters of each star best matching this gargantuan global set of observations.

15 November 2021

45. RR Lyrae variables

Like the Cepheid variables, although less luminous, the distinctive light curves of RR Lyrae stars allows their detection to large distances. Nearly 200 were included in the Hipparcos catalogue, although only one provided a meaningful distance. Gaia DR2 provides results for 140,784 RR Lyrae stars as faint as 20.7 mag.

8 November 2021