Image of the Week

 

Gaia's contribution to discovering distant worlds

Figure 1. Graphical representation of the mass (Jupiter Masses) versus orbital period (days) distribution of the population of known extrasolar planets (status 10 January 2024). The different colours and shapes with which the planets are identified indicate the different methods by which they have been detected. The light blue rectangle indicates Gaia's containment area, the purple one that of Cheops, the orange one that of PLATO and the dark blue one that of Ariel. Credits: Adapted from NASA Exoplanet Archive Caltech by Mariasole Agazzi for the Gaia mission. GIF by Tineke Roegiers.

 

The European Gaia space mission is primarily designed to map with extreme precision the positions, parallaxes, and proper motions of over a billion stars in the Milky Way and beyond, creating an exceptionally detailed three-dimensional stellar catalogue. Its characteristics have also proven optimal for contributing to one of the most promising fields of astrophysics in the last twenty years: the study and characterisation of extrasolar planets. Indeed, a wide range of applications exist for which Gaia data will be key for the ongoing exoplanetary ESA missions, Cheops, Plato and Ariel, as well as missions in collaboration, such as the James Webb Space Telescope. This story provides an overview of the contribution of Gaia to this research area and positions the mission in the landscape set by ESA's exoplanet missions, Cheops, PLATO, and Ariel, showing its synergies and complementarities.

 

The search for extrasolar planets

The field of exoplanets represents one of the most fascinating and dynamic areas of contemporary astronomy. With the growing interest in understanding the universe and its planetary diversity, the search for and study of planets outside our solar system has become crucial. Exoplanets offer an unprecedented opportunity to understand the formation and evolution of stellar and planetary systems, as well as to explore the conditions for the emergence and sustainability of life in the universe. The first discovery of an exoplanet in 1992 has indeed revolutionized our view of the universe, giving rise to many fundamental questions about the origin of life and its possible presence outside our solar system. In the last twenty years, we have witnessed an almost exponential increase in the number of detected planets: as of today (March 2024), over five thousand have been found.

 

Figure 2. Graphical representation of the number of confirmed extrasolar planets (y-axis) detected per year (x-axis) by type of detection. The different colours correspond to the different detection techniques used. The two predominant colours are green, which corresponds to the transit method, and red, which corresponds to the radial velocity method. Source: NASA Exoplanet Archive Caltech.

 

To detect these distant worlds, astronomers employ various methods. Among the main ones is the transit method, which detects the periodic decrease in the apparent brightness of a star when a planet passes in front of it. Another method is the radial velocity method (Doppler technique), which exploits small variations in the radial velocity of a star caused by the presence of a planet orbiting it. Others include gravitational microlensing, direct imaging, and astrometry. One of the most promising methods and newest kid on the block is astrometry. This technique uses the precise measurement of the positions of stars in the sky to detect the minute oscillatory movement caused by planets orbiting them. It is a method particularly suitable for detecting massive planets in orbits distant from their parent star.

Despite the potential of this technique, as we can see from the image above, only a few planets have been detected astrometrically so far. The reasons can be attributed to technical challenges, instrument limitations, and required resources. To utilize astrometry, extremely sensitive and precise instruments are necessary. Moreover, since deviations in stellar positions can be very subtle, repeated and prolonged observations are required. In this context, Gaia comes to the rescue, playing a significant role. In fact, the mission offers an unprecedented opportunity to expand the exoplanet knowledge through astrometry, providing extremely precise astrometric data on a vast number of stars in our galaxy.

 

"In terms of their geometric alignment, the planets discovered with Gaia will be orthogonal to those normally detected and characterised with the transit method by CHEOPS, PLATO, and ARIEL. This will open a completely new discovery space that we have not really been able to explore until now. It will be interesting to see whether the assumption holds true that most planetary systems lie on the same orbital plane just like in our Solar System. Maybe some exoplanet systems have been so perturbed that Gaia could find huge outer planets that are not in the same plane as their inner, transiting siblings. We can cross-match whether known transiting exoplanets have Gaia signals, or vice versa, follow the exoplanets detected by Gaia to detect if there are also transit signals. Such results could lead us to reassess our idea of planetary systems’ formation and evolution. In any case, we will open a new exploration sandbox."

Maximilian Günther, ESA Cheops Mission Project Scientist

 

The Gaia DR3 data release, for the first time, included astrometric orbital solutions for companions around stars with sensitivities extending into the planetary-mass regime. Through sophisticated methods like Markov chain Monte Carlo and genetic algorithms, it was possible to fit the orbits of 1162 sources, validating 198 of these, across the planetary, brown dwarf, and low-mass stellar companion regimes (Holl et. all 2023). Thanks to this technique Gaia DR3 showed the companion of HD114762 (Latham et al. 1989) which in hindsight could have been the very first super-Jupiter exoplanet, was a clear binary star. This achievement highlighted Gaia's capability to refine known orbital companions and discover new ones, promising significant advancements in our understanding of exoplanets and sub-stellar companions with future data releases.

But that’s not all, Gaia makes for an essential tool in the research and understanding of planetary systems with its detailed catalogue of host stars. Gaia stellar data are widely used by current exoplanetary missions, significantly contributing to our understanding of the universe.

 

"Knowing the characteristics of exoplanet host stars is fundamental. In fact, stars and planets interact directly with each other. The star plays a fundamental role in the evolution of the planet: the same planet around a different star would have developed in a completely different way. For this reason, it is important to know the characteristics of the star, and this knowledge provided by Gaia is increasingly recognised within the exoplanet community."

Theresa Lüftinger, ESA Ariel Mission Project Scientist

 

 

Gaia's role in exoplanet detection

 

Despite the field of extrasolar planets developing concurrently with the Gaia mission’s inception, the initial documents outlining Gaia's objectives already hinted at a significant contribution to this emerging research area. Over time, this possibility became a certainty: to date, Gaia significantly contributes to the science of extrasolar planets through various means.

 

"Exoplanet science wouldn’t be the same without Gaia."

Maximilian Günther, ESA CHEOPS Mission Project Scientist

 

 

Characterisation of host stars

 

By creating an exceptionally detailed multi-dimensional stellar catalogue, Gaia provides information about host stars around which extrasolar planets orbit. The data obtained with the space telescope are employed to derive stellar masses, stellar radius, temperatures, luminosity, and other characteristics crucial to understanding the environment in which planets orbit. A comprehensive characterisation of the fundamental properties of host stars is essential, as the formation and evolution of exoplanets are directly influenced by host stars at various points in time. Stellar information also allows to determine characteristics of the planet itself. Accurate stellar data are essential for deriving the planet's radius, mass, and age, but additional information may be required to fully determine these parameters. This is particularly intriguing because some theoretical models, using knowledge of radius and mass to derive density, allow us to make certain assumptions about the planet's composition and structure.

Starting with the Data Release 2 in 2018, Gaia data have allowed to re-derive very accurate and precise stellar radii that in turn made for a critical re-assessment of the bimodality of the distribution of the radii of thousands of small planets uncovered by the Kepler mission: Gaia's first key contribution to the exoplanet field.

Gaia’s star catalogue constitutes a fundamental reference for other missions, which use it both initially to select the targets to observe and, subsequently, to deduce planet information from their host stars. Also the catalogue of future missions currently being developed, such as HPIC: The Habitable Worlds Observatory Preliminary Input Catalog, is based on the use of Gaia data.

 

"If we desire to know and characterise the planet, we must know the star. For PLATO, our input catalogue has been fundamentally based on the Gaia catalogue, which was then complemented with additional information."

Ana Heras, ESA Plato Mission Project Scientist

 

Release of an unbiased planets catalogue

 

Although Gaia's primary goal isn't the detection of exoplanets, its ability to monitor variations in stellar positions reveals the presence of planets orbiting around them. The mission surveys a vast number of stars, all-sky, covering a time baseline of around 10 years, measuring their positions, radial velocities, and other features with high precision. This data can be used to detect the gravitational influence of exoplanets on the position of their host stars, enabling planet detection.

Gaia is primarily dedicated to high-precision astrometry but also provides spectroscopy and photometry, allowing to study various types of photometric variability, including exoplanetary transits. So far, transit photometry has been the most effective method for detecting exoplanets with over 3000 of the over 5000 exoplanets discovered to date, in majority thanks to the Kepler mission.

Gaia’s photometry has some limitations though, making it less optimal for transit planet detection: it is sparse and irregularly sampled, requiring a longer observation span to distinguish the signals by extrasolar planets. Nonetheless, it has already been possible to confirm the detection of two previously discovered exoplanets: WASP-19b (Hebb et al. 2009) and WASP-98b (Hellier et al. 2014). Furthermore, in 2022, Gaia found its first extrasolar planets with the transit method (Panahi et al. 2022) which were never detected before and published 214 of such candidates for follow-up. With the upcoming fourth data release, we can anticipate the discovery of hundreds of new planets by Gaia using the transit method.

However, Gaia's true paradigm shift lies in the astrometric method, which has so far allowed the discovery of only a limited number of extrasolar planets. The Gaia mission is set to become a game-changer in this context, unleashing the power of micro-arcsecond astrometry.

Like the spectroscopic technique, astrometric measurements can reveal periodic changes of the star’s position around the system's barycenter due to the gravitational attraction of orbiting planets. With the two major data releases still come, Gaia DR4 (expected no sooner than the end of 2025) and Gaia DR5, Gaia will produce all-sky exoplanet catalogues containing thousands of new exoplanets candidates. In addition, the complete pool of collected data will be made available, which can be analysed by the researchers to detect further candidate exoplanets. This might double the number of extrasolar planets discovered to date, which currently stands at over five thousand: a real revolution.

 

"With the two upcoming data releases, DR4 and DR5, Gaia's full astrometric planet finding capabilities will be unveiled. Leveraging the 10-yr extended mission, thousands of giant planets beyond the snowline will be detected, including true Jovian analogues (same mass and period of Jupiter). Gaia is particularly 'democratic', as it will provide a census of cold gas giants that will be unbiased across mass, chemical composition, and age of the host stars. Gaia's crucial contributions to many aspects of the formation, physical and dynamical evolution of planetary systems will be fully realized exploiting its huge synergy potential with ongoing and planned exoplanet detection and (atmospheric) characterization programs, such as those that are being and will be carried out by Cheops, PLATO and Ariel."

Alessandro Sozzetti, Gaia Data Processing and Analysis Consortium

 

A crucial characteristic is that Gaia is impartial in its examination of the entire sky, monitoring stellar and sub-stellar objects without discrimination based on spectral type, age, evolutionary status, stellar environment, or multiplicity status. We can therefore expect Gaia not only to monitor millions of main-sequence stars with sufficient sensitivity to detect brown dwarf and/or exoplanet companions within a few astronomical units of their host stars but also to provide accurate astrometric time series for thousands of very low-mass stars in the solar neighborhood (Sozzetti et al. 2014). For these targets, the mission's astrometry could be sufficiently precise to reveal any orbiting companion with masses even below one Jupiter mass in addition to planets belonging to binary systems. Obtaining an impartial catalogue is a crucial result as it will allow us to better understand the distribution of different types of planets across the Milky Way and to study the impact of stellar environment.

 

"For those working in this field, an important goal is to understand the demography and diversity of the systems out there - what can exist? Sub-Neptune-type planets, for example, are one of Cheops' main targets. Although they do not exist in our solar system, we know that they are the most common planet type in our galaxy. This poses a new puzzle to solve: why do we find ourselves in a system with life without this kind of planet? Could we have life with this kind of planet? With Gaia exploring a completely new parameter space, a range we have never had the opportunity to look at before, similarly new insights could be discovered, giving us more clues about the formation and evolution of extrasolar planets. Such pieces of the puzzle from different angles are truly fundamental for completing the picture."

Maximilian Günther, ESA Cheops Mission Project Scientist

 

Figure 3. Graphical representation of the mass (Jupiter Masses) versus orbital period (days) distribution of the population of known extrasolar planets (status 10 January 2024). The different colours and shapes with which the planets are identified indicate the different methods by which they have been detected. The light blue rectangle indicates Gaia's containment area, the purple one that of Cheops, the orange one that of PLATO and the dark blue one that of Ariel. Credits: Adapted from NASA Exoplanet Archive Caltech by Mariasole Agazzi for the Gaia mission.

 

Gaia will not be able though to detect planets with an Earth-like mass unless the object is extremely close to the Sun, which is unlikely. In an era where exoplanetary research is focused on the search for Earth-like planets, we may therefore ask: does it really make sense to try to detect a sample of planets that deviate so much from the target of greatest interest? Yes, absolutely! In fact, it is essential to understand the variety of the extrasolar planet zoo, to possess a large sample of planets with different characteristics. For instance, the presence of Jupiter in the solar system, acting as cometary vacuum cleaner preventing Earth from being heavily bombarded, may well have been instrumental for the development of life on Earth.

 

"If we want to understand Earth-like planets, how they form, how they evolve, what their atmospheres are composed of, we absolutely also need to understand the formation and evolution of the largest planets. Even if we look for habitability in other systems, it is necessary to understand the whole system and its chemistry and dynamics, including the gas giant planets. Take our own solar system as an example: Jupiter and Saturn are important for the orbit of the Earth, and thus for the development of life. If only Saturn had been on a more elliptical orbit or closer to the Sun, Earth's climate would have developed in a very different way - and this is just one example. The large planets therefore also play a crucial role in the evolution and the habitability of the smaller ones."

Theresa Lüftinger, ESA Ariel Mission Project Scientist

 

Finally, Gaia contributes to validating extrasolar planetary candidates discovered by other missions such as Kepler, TESS, and ground-based telescopes. Gaia's precise measurements of stellar positions can confirm the existence and characteristics of suspected exoplanets and reveal the structure and dynamics of extrasolar planetary systems.

 

What can we expect for the future?

 

In conclusion, Gaia emerges as a crucial catalyst for the study of extrasolar planets. With its ability to perform extremely precise astrometric measurements, the mission will soon bring about a paradigm shift in this field of research. With the upcoming fourth data release, Gaia is expected to unveil thousands of new planets. Its non-discriminatory astrometry against spectral type, age, or multiplicity of the host stars offers the opportunity to detect planets even in binary systems and will provide a comprehensive view of the exoplanet zoo. Moreover, Gaia will continue to contribute to the fundamental characterisation of host stars of exoplanets, adding to the understanding of the formation and evolution of planetary systems. In summary, Gaia opens new avenues in the search for and study of exoplanets, enriching our understanding of the universe and its diverse planetary facets.

 

Figure 4. Gaia discovery space. Shown here are the planetary mass of exoplanets versus the semi-major axis of the orbits of exoplanets about their host star. The upper purple curves indicate the sensitivity of Gaia with respect to objects out to a distance of about 150 parsecs (so out to various star formation regions), as compared to the lower purple curves which indicate the sensitivity of Gaia to detect extrasolar planets out to a distance of about 20 parsecs. While the dotted purple curves correspond to the nominal Gaia mission lifetime of 5 years, the full purple curves correspond to an extended mission for a total of 10 years. Credits: Sozzetti and de Bruijne 2018.

 

Further reading

 

Stories:

 

Gaia data set

 

Videos and explainers:

Published papers:

 

Story written by Mariasole Agazzi, Tineke Roegiers, Jos de Bruijne

 

Credits: ESA/Gaia/DPAC, Mariasole Agazzi, Alessandro Sozetti, Johannes Sahlmann, Maximilian Günther, Theresa Lüftinger, Ana Hera, Tineke Roegiers, Jos de Bruijne.

[Published: 22/04/2024]

 

Image of the Week Archive

2024

28/05: Did Gaia find its first neutron star?

26/04: A textbook solar eruption

22/04: Gaia's contribution to discovering distant worlds

16/04: Gaia spots Milky Way's most massive black hole of stellar origin

02/04: The Gaia Cataclysmic Variable hook

2023

19/12: 10 Science topics to celebrate Gaia's 10 years in space

31/10: Gaia observes cosmic clock inside a heavenly jewel

10/10: Gaia Focused Product Release stories

27/09: Does the Milky Way contain less dark matter than previously thought?

22/09: Mass-luminosity relation from Gaia's binary stars

13/09: Gaia DPAC CU8 seminars

13/06: Gaia's multi-dimensional Milky Way

18/05: Mapping the Milky Way

15/05: Goonhilly station steps in to save Gaia science data

25/04: The Gaia ESA Archive

05/04: Dual quasar found to be hosted by an ongoing galaxy merger at redshift 2.17

21/03: GaiaVari: a citizen science project to help Gaia variability classificaton

09/02: Missing mass in Albireo Ac: massive star or black hole?

31/01: Gaia reaches to the clouds – 3D kinematics of the LMC

25/01: Meet your neighbours: CNS5 - the fifth catalogue of nearby stars

18/01: A single-object visualisation tool for Gaia objects

2022

25/11: 100 months of Gaia data

23/11: The astonishment

09/11: Gamma-Ray Burst detection from Lagrange 2 point by Gaia

04/11: Gaia's first black hole discovery: Gaia BH1

26/10: Are Newton and Einstein in error after all?

21/10: Gaia ESA Archive goes live with third data release

06/10: Mapping the interstellar medium using the Gaia RVS spectra

26/09: Gaia on the hunt for dual quasars and gravitational lenses

23/09: Gaia's observation of relativistic deflection of light close to Jupiter

13/06: Gaia Data Release 3

10/06: MK classification of stars from BP/RP spectrophotometry across the Hertzsprung-Russell diagram

09/06: BP/RP low-resolution spectroscopy across the Hertzsprung-Russell diagram

27/05: Cepheids and their radial velocity curves

23/05: The Galaxy in your preferred colours

19/05: GaiaXPy 1.0.0 released, a tool for Gaia's BP/RP spectra users

11/05: Systemic proper motions of 73 galaxies in the Local group

28/03: Gaia query statistics

16/03: Gaia's first photo shooting of the James Webb Space Telescope

08/03: Gaia's women in science - coordination unit 8

25/02: Not only distances: what Gaia DR3 RR Lyrae stars will tell us about our Galaxy and beyond

11/02: Gaia's women in science

31/01: Astrometric orbit of the exoplanet-host star HD81040

12/01: The Local Bubble - source of our nearby stars

05/01: A Milky-Way relic of the formation of the Universe

2021

23/12: Signal-to-Noise ratio for Gaia DR3 BP/RP mean spectra

22/12: The 7 October 2021 stellar occultation by the Neptunian system

01/12: Observation of a long-predicted new type of binary star

24/09: Astrometric microlensing effect in the Gaia16aye event

22/09: the power of the third dimension - the discovery of a gigantic cavity in space

16/09: An alternative Gaia sky chart

25/08: Gaia Photometric Science Alerts and Gravitational Wave Triggers

09/07: How Gaia unveils what stars are made of

23/06: Interviews with CU3

27/04: HIP 70674 Orbital solution resulting from Gaia DR3 processing

30/03: First transiting exoplanet by Gaia

26/03: Apophis' Yarkovsky acceleration improved through stellar occultation

26/02: Matching observations to sources for Gaia DR4

2020

22/12: QSO emission lines in low-resolution BP/RP spectra

03/12: Gaia Early Data Release 3

29/10: Gaia EDR3 passbands

15/10: Star clusters are only the tip of the iceberg

04/09: Discovery of a year long superoutburst in a white dwarf binary

12/08: First calibrated XP spectra

22/07: Gaia and the size of the Solar System

16/07: Testing CDM and geometry-driven Milky Way rotation Curve Models

30/06: Gaia's impact on Solar system science

14/05: Machine-learning techniques reveal hundreds of open clusters in Gaia data

20/03: The chemical trace of Galactic stellar populations as seen by Gaia

09/01: Discovery of a new star cluster: Price-Whelan1

08/01: Largest ever seen gaseous structure in our Galaxy

2019

20/12: The lost stars of the Hyades

06/12: Do we see a dark-matter like effect in globular clusters?

12/11: Hypervelocity star ejected from a supermassive black hole

17/09: Instrument Development Award

08/08: 30th anniversary of Hipparcos

17/07: Whitehead Eclipse Avoidance Manoeuvre

28/06: Following up on Gaia Solar System Objects

19/06: News from the Gaia Archive

29/05: Spectroscopic variability of emission lines stars with Gaia

24/05: Evidence of new magnetic transitions in late-type stars

03/05: Atmospheric dynamics of AGB stars revealed by Gaia

25/04: Geographic contributions to DPAC

22/04: omega Centauri's lost stars

18/04: 53rd ESLAB symposium "the Gaia universe"

18/02: A river of stars

2018
21/12: Sonification of Gaia data
18/12: Gaia captures a rare FU Ori outburst
12/12: Changes in the DPAC Executive
26/11:New Very Low Mass dwarfs in Gaia data
19/11: Hypervelocity White Dwarfs in Gaia data
15/11: Hunting evolved carbon stars with Gaia RP spectra
13/11: Gaia catches the movement of the tiny galaxies surrounding the Milky Way
06/11: Secrets of the "wild duck" cluster revealed
12/10: 25 years since the initial GAIA proposal
09/10: 3rd Gaia DPAC Consortium Meeting
30/09: A new panoramic sky map of the Milky Way's Stellar Streams
25/09: Plausible home stars for interstellar object 'Oumuamua
11/09: Impressions from the IAU General Assembly
30/06: Asteroids in Gaia Data
14/06: Mapping and visualising Gaia DR2

25/04: In-depth stories on Gaia DR2

14/04: Gaia tops one trillion observations
16/03: Gaia DR2 Passbands
27/02: Triton observation campaign
11/02: Gaia Women In Science
29/01: Following-up on Gaia
2017
19/12: 4th launch anniversary
24/11: Gaia-GOSA service
27/10: German Gaia stamp in the making
19/10: Hertzsprung-russell diagram using Gaia DR1
05/10: Updated prediction to the Triton occultation campaign
04/10: 1:1 Gaia model arrives at ESAC
31/08: Close stellar encounters from the first Gaia data release
16/08: Preliminary view of the Gaia sky in colour
07/07: Chariklo stellar occultation follow-up
24/04: Gaia reveals the composition of asteroids
20/04: Extra-galactic observations with Gaia
10/04: How faint are the faintest Gaia stars?
24/03: Pulsating stars to study Galactic structures
09/02: Known exoplanetary transits in Gaia data
31/01: Successful second DPAC Consortium Meeting
2016
23/12: Interactive and statistical visualisation of Gaia DR1 with vaex
16/12: Standard uncertainties for the photometric data (in GDR1)
25/11: Signature of the rotation of the galactic bar uncovered
15/11: Successful first DR1 Workshop
27/10: Microlensing Follow-Up
21/10: Asteroid Occultation
16/09: First DR1 results
14/09: Pluto Stellar Occultation
15/06: Happy Birthday, DPAC!
10/06: 1000th run of the Initial Data Treatment system
04/05: Complementing Gaia observations of the densest sky regions
22/04: A window to Gaia - the focal plane
05/04: Hipparcos interactive data access tool
24/03: Gaia spots a sunspot
29/02: Gaia sees exploding stars next door
11/02: A new heart for the Gaia Object Generator
04/02: Searching for solar siblings with Gaia
28/01: Globular cluster colour-magnitude diagrams
21/01: Gaia resolving power estimated with Pluto and Charon
12/01: 100th First-Look Weekly Report
06/01: Gaia intersects a Perseid meteoroid
2015
18/12: Tales of two clusters retold by Gaia
11/11: Lunar transit temperature plots
06/11: Gaia's sensors scan a lunar transit
03/11: Celebrity comet spotted among Gaia's stars
09/10: The SB2 stars as seen by Gaia's RVS
02/10: The colour of Gaia's eyes
24/09: Estimating distances from parallaxes
18/09: Gaia orbit reconstruction
31/07: Asteroids all around
17/07: Gaia satellite and amateur astronomers spot one in a billion star
03/07: Counting stars with Gaia
01/07: Avionics Model test bench arrives at ESOC
28/05: Short period/faint magnitude Cepheids in the Large Magellanic Cloud
19/05: Visualising Gaia Photometric Science Alerts
09/04: Gaia honours Einstein by observing his cross
02/04: 1 April - First Look Scientists play practical joke
05/03: RR Lyrae stars in the Large Magellanic Cloud as seen by Gaia
26/02: First Gaia BP/RP deblended spectra
19/02: 13 months of GBOT Gaia observations
12/02: Added Value Interface Portal for Gaia
04/02: Gaia's potential for the discovery of circumbinary planets
26/01: DIBs in three hot stars as seen by Gaia's RVS
15/01: The Tycho-Gaia Astrometric Solution
06/01: Close encounters of the stellar kind
2014
12/12: Gaia detects microlensing event
05/12: Cat's Eye Nebula as seen by Gaia
01/12: BFOSC observation of Gaia at L2
24/11: Gaia spectra of six stars
13/11: Omega Centauri as seen by Gaia
02/10: RVS Data Processing
12/09: Gaia discovers first supernova
04/08: Gaia flag arrives at ESAC
29/07: Gaia handover
15/07: Eclipsing binaries
03/07: Asteroids at the "photo finish"
19/06: Calibration image III - Messier 51
05/06: First Gaia BP/RP and RVS spectra
02/06: Sky coverage of Gaia during commissioning
03/04: Gaia source detection
21/02: Sky-background false detections in the sky mapper
14/02: Gaia calibration images II
06/02: Gaia calibration image I
28/01: Gaia telescope light path
17/01: First star shines for Gaia
14/01: Radiation Campaign #4
06/01: Asteroid detection by Gaia
2013
17/12: Gaia in the gantry
12/12: The sky in G magnitude
05/12: Pre-launch release of spectrophotometric standard stars
28/11: From one to one billion pixels
21/11: The Hipparcos all-sky map
15/10: Gaia Sunshield Deployment Test
08/10: Initial Gaia Source List
17/09: CU1 Operations Workshop
11/09: Apsis
26/08: Gaia arrival in French Guiana
20/08: Gaia cartoons
11/07: Model Soyuz Fregat video
01/07: Acoustic Testing
21/06: SOVT
03/06: CU4 meeting #15
04/04: DPCC (CNES) 
26/03: Gaia artist impression 
11/02: Gaia payload testing  
04/01: Space flyby with Gaia-like data
2012
10/12: DPAC OR#2. Testing with Planck
05/11: Galaxy detection with Gaia
09/10: Plot of part of the GUMS-10 catalogue
23/07: "Gaia" meets at Gaia
29/06: The Sky as seen by Gaia
31/05: Panorama of BAM clean room
29/03: GREAT school results
12/03: Scanning-law movie
21/02: Astrometric microlensing and Gaia
03/02: BAM with PMTS
12/01: FPA with all the CCDs and WFSs
2011
14/12: Deployable sunshield
10/11: Earth Trojan search
21/10: First Soyuz liftoff from the French Guiana
20/09: Fast 2D image reconstruction algorithm
05/09: RVS OMA
10/08: 3D distribution of the Gaia catalogue
13/07: Dynamical Attitude Model
22/06: Gaia's view of open clusters
27/05: Accuracy of the stellar transverse velocity
13/05: Vibration test of BAM mirrors
18/04: L. Lindegren, Dr. Honoris Causa of the Observatory of Paris
19/01: Detectability of stars close to Jupiter
05/01: Delivery of the WFS flight models
2010
21/12: The 100th member of CU3
17/11: Nano-JASMINE and AGIS
27/10: Eclipsing binary light curves fitted with DPAC code
13/10: Gaia broad band photometry
28/09: Measuring stellar parameters and interstellar extinction
14/09: M1 mirror
27/08: Quest for the Sun's siblings
 
Please note: Entries from the period 2003-2010 are available in this PDF document.