Image of the Week

Gaia's impact on Solar system science

 

Figure 1: The 14,099 asteroids in Gaia Data Release 2 (indicated with green orbits) along with four newly discovered asteroids by Gaia (indicated with the pink orbits). Credits: ESA/Gaia/DPAC. Acknowledgements: Created with Gaia Sky by S. Jordan and T. Sagrista using info from Gaia DPAC CU4 / F. Spoto.

Gaia's impact on Solar System science follows not only from its observations of Solar System objects themselves, but also from the improved knowledge of the position and motion of stars. Asteroids are observed against a background of stars. These stars will thus appear in the images taken of asteroids, and are used as reference points to determine where asteroids are in space. The knowledge of where a background star is at the respective moment in time is therefore essential.

With the advent of the accurate positions and proper motions of stars in the Gaia data releases, astronomers have started to recompute the asteroid's positions based on old asteroid observations. These more precise asteroid positions have in turn lead to the computation of more precise orbits. Going back in time, one can see if there are older observations that match with a given asteroid or, when going forward in time, predict where asteroids will be in the future. Having a better knowledge of where an asteroid will be, improves the chance of observing it again. Not only directly, by taking an image of an asteroid, but also indirectly, for example through stellar occultation studies. When applied to near-earth asteroids, the improved orbits can reveal how closely the asteroid will approach Earth.

Stellar occultation studies rely on both the knowledge of the asteroid's orbit and the knowledge of the star's position at a given moment in time. A prediction is then made for certain asteroids occulting sufficiently bright stars, allowing to observe the occultation from the ground if one is lucky enough to be positioned on the shadow track on the surface of the Earth. Before Gaia data releases, these shadow tracks were computed with large uncertainties. Given the precision of the asteroid orbit could have been improved as well as the fact that star's positions surely did improve with the Gaia data releases, it is not a surprise that the uncertainties on the computations of the shadow tracks decreased a lot. This effect is clearly visible in Figure 2, where the succesful observations of occultations are given with time. There is a clear jump when Gaia Data Release 1 came out in September 2016, and an even bigger jump when Gaia Data Release 2 was being used. So since Gaia data releases, astronomers are better positioned on the ground improving their chances to observe stellar occultations.

Figure 2: Immediate impact of Gaia Data Release 2 on the amount of stellar occultation events successfully observed (counting at least one successful observation). One can see the jump in 2016 when Gaia Data Release 1 (Gaia DR1) became available in September 2016. Then another increase is visible in 2018, when Gaia's second data release (Gaia DR2) came out in April 2018. The 2019 numbers in the figure are incomplete and only take into account the first few months of 2019. When looking at the website Euraster, and counting the stellar occultation events in 2019 with at least one successful observation, a total of 180 succesful events are obtained for the full 2019. The graphic in the figure was produced by João Ferreira using data from Euraster, a website for asteroidal occultation observers in Europe, managed by Eric Frappa. ​​​​​​​

 

Through stellar occultations, and by observing the star right before, during, and after its occultation by the Solar System object, one can measure important parameters, e.g., its shape and size, for that Solar System object. While observing the star being occulted, one knows exactly the location of the Solar system object in space responsible for this occultation. This helps to confirm and further improve the orbit of this very object itself. The measurements taken during the occultation can provide more information on possible rings around an asteroid, the shape of the object, and much more.

Precise star data also allows to navigate in deep space with more confidence. With the use of Gaia DR2 and Hubble star fields, the space probe New Horizons computed a more precise trajectory to visit the Kuiper Belt Object Arrokoth (also referred to as Ultima Thule or 2014 MU69), while obtaining information on the shape and other peculiarities through stellar occultations. Gaia data thus contains Solar System objects but also improves the chances to observe these objects from Earth, and even helps with observations performed in space.

Apart from the use of star data for Solar System science, Gaia Data Release 2 contains 14,099 asteroids with epoch astrometry and photometry based on more than 1.5 million CCD observations. Typically, residuals for Gaia DR2 asteroids are in the range -5 to 5 milli-arcsecond with a substantial part (52% of the along-scan residuals) in the range of -1 to 1 milli-arcsecond. The data published can already be used to derive more parameters for these asteroids, such as rotation periods.

Expected near the end of 2020 is Gaia's Early Data Release 3 (Gaia EDR3), which will bring improved astrometry (better positions and proper motions) for stars thus further improving the stellar occultation predictions, deep space navigation, and asteroid orbit computations. Beyond Gaia EDR3, Gaia's third Data Release (Gaia DR3) is expected to contain information on about 100,000 asteroids. While Gaia DR2 contains known asteroids only, Gaia DR3 is expected to also include newly discovered asteroids. First discoveries by Gaia are coming out these days with the help of observatories following up on the alerts sent out to the Gaia Follow-Up Network.

Further reading on stellar occultation studies using Gaia data, asteroid discoveries by Gaia, or Solar System science with Gaia can be found here:

Many enthusiastic amateur astronomers help out making stellar occultation observations. Are you interested as well? Check out the following websites on stellar occultation:

Credits: ESA/Gaia/DPAC

[Published: 30/06/2020]

 

Image of the Week Archive

2020
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.