Image of the Week

Searching for solar siblings with Gaia

   
  Figure 1: The red circles denote the possible present-day distributions of solar siblings in the disk of the Milky Way. Each panel corresponds to a specific set of Milky Way model parameters. The dashed black lines represent the shape of the Galactic spirals arms in each case. The solid lines in the bottom left panel represent the spiral arms of the Galaxy in a composite model in which two arms have different pattern speed and amplitude compared to the other two arms. The black crosses in the panels mark the location of the Sun's birth cluster 4600 million years ago.  In the simulations, this position is assumed to be at 9 kpc from the Galactic centre. Here, the Sun's birth cluster has an initial mass of 1023 solar masses and a radius of 2 parsec.  
 

Some 4600 million years ago, the Sun was born in a cluster, i.e., in a clump of stars that interact gravitationally and share the same age, metallicity and chemical composition. Evidence for this birth environment can be observed in the Solar System. For instance, the decay products of radioactive elements found in the meteorite fossil record suggest that a supernova explosion occurred near the Sun, during or shortly after the formation of the Solar System. Additionally, the large eccentricities of the orbits of objects located in the Edgeworth-Kuiper belt are thought to be a consequence of close encounters experienced by the Sun and other stars that once belonged to the birth cluster.

The intense gravitational tidal field of the Galaxy dispersed the Sun's birth cluster 2400 million years ago. As a consequence, the stars that were born together with the Sun, the so-called solar siblings, might be currently dispersed all over the Galactic disk. The present-day distribution of solar siblings can be predicted by performing numerical simulations of the evolution of the Sun's birth cluster in a realistic model of the Galaxy. However, such a distribution will not be unique, given the uncertainties in the Galaxy model and its parameters. Martínez-Barbosa et al. (2016) carried out N-body simulations of the Sun's birth cluster to predict the current location of the solar siblings in the Milky Way. These simulations include the gravitational forces within the cluster, the effects of stellar evolution on the cluster population and the gravitational force due to the Galaxy.

Figure 1 shows the possible spatial distributions the solar siblings might have right now, according to the numerical simulations performed by Martínez-Barbosa et al. (2016). In a Galaxy model containing two spiral arms (top panel), the solar siblings can be very close to each other in radius and azimuth, meaning that they have a similar motion around the Galaxy. In less optimistic cases, the solar siblings might be rather dispersed in the Galactic disk (bottom panel). This occurs at considering four spiral arms (bottom right panel) or at considering a Galaxy model with a composition of spiral arms with different amplitudes and angular velocities (bottom left panel).     

If field disk stars were overlaid on each panel of Figure 1, it would not be possible to distinguish between solar siblings and other disk stars. Hence, it is necessary to develop specific techniques to search for solar siblings in the future. One of these techniques, which was introduced by Brown et al. (2010) and later revised by Martínez-Barbosa et al. (2016), consists of searching for solar siblings in the space of astrometric observables (parallaxes, proper motions and radial velocities). The procedure is illustrated in Figure 2. First, every predicted distribution of solar siblings is compared to the distribution of disk stars, as Gaia will see them. This comparison is made in order to find regions in the space of astrometric observables where the contrast between the solar siblings and disk stars is high. By making statistics over a broad range of possible Galactic parameters and initial conditions of the Sun's birth cluster, Martínez-Barbosa et al. (2016) found that the region where solar siblings are most reliably detected - and discriminated from disk stars through their kinematics - is at parallaxes larger than 5 mas, proper motions between 4 and 6 mas yr-1 and radial velocities between -2 and 0 km s-1. Selecting stars from this region will increase the probability of identifying solar sibling candidates. In this respect, the upcoming data from Gaia and other observational campaigns will be essential. However, it is also necessary to determine precisely the age, metallicity and chemical composition of these stars in order to find the solar family. The identification of solar siblings will provide information on the environment where the Solar System was formed and on the place in the Galaxy where the Sun was born.

   
  Figure 2: Distribution of solar siblings (red contours) and simulated Gaia data for disk stars (black contours) in the proper motion vs. parallax plane. Each panel corresponds to the distributions shown in Figure 1. The disk stars were simulated using the Gaia Universe Model Snapshot.  
 

Credits: Carmen Adriana Martínez Barbosa (Leiden Observatory, Leiden University)

[Published: 04/02/2016]

 

Image of the Week Archive

2017
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
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
 
Please note: Entries from the period 2003-2010 are available in this PDF document.