Image of the Week

The lost stars of the Hyades

 

 

The Hyades and its tidal tails. The dots represent those stars from Gaia DR2 that are in dense regions (at least 2.5 x 10-3 stars per cubic parsec). In red is plotted the Hyades cluster proper. The green dots represent the leading tail while the blue dots represent the trailing tail. All other stars in the dense regions are plotted with pink dots. Indicated with yellow in the background is the location of the predicted Hyades tidal tails from the model by Kharchenko et al. (2009). Image credit: Siegfried Röser et al (2019).

 

The Hyades are the closest star cluster to Earth, being a mere 150 light years away, and can be easily spotted from Earth with the naked eye given some of its stars are so bright. Being so close to Earth makes the Hyades a perfect cluster to study in more detail. With the help of Gaia and its high-precision measurements of the positions, movements, and parallaxes (leading to derived distances), the three-dimensional structure of the cluster can be studied in great detail.

Stars in an open cluster are known to move together in space. While position and distance help to identify which stars are close to one another, the knowledge of the velocities of stars is essential to identify the ones that move along together. If nearby stars are moving in opposite directions, they most probably do not belong together. If nearby stars are moving in the same direction though, this is a good indicator of a genetic link.

A star cluster does not live forever. While star clusters can contain hundreds to thousands of stars, they continuously lose stars due to the gravitational pull of the Milky Way. This effect is felt most strongly by the star cluster members with the lowest masses and a slightly higher orbital velocity about the cluster centre. However, even stars which were lost from the cluster approximately still share the same velocity. If one therefore extends the search radius and traces back stars to their original place in space, former members of a cluster can be found.

Two independent research teams (from Heidelberg in Germany and from Vienna in Austria) searched through the Gaia DR2 data near the Hyades cluster, tracing back stars within a certain distance from the Hyades cluster with the help of their proper motions and radial velocities, and found traces of former members that the Hyades cluster has lost in the course of several hundred million years.

Based on the three-dimensional velocity data, evidence was found for the existence of extended tidal tails associated with the Hyades cluster. A leading tail extending up to 170 parsec from the centre of the Hyades and a trailing tail up to 70 parsec. More information can be found in the papers describing the results as referenced below. A video showing the cluster and its tidal tails can be found below.

 

 

The video first shows the direction to the constellation Taurus with the Hyades star cluster. The cluster is close on the sky to the bright star Aldebaran, marked in red. This star, however, is not a member of the Hyades, being located much closer to the Earth (at 66 light years from Earth). The directions of movements are then shown for many stars based on velocities measured by Gaia. The members and lost stars of the Hyades are flying in the same direction (both groups are marked in yellow). The video then shows the exaggerated movements of the Hyades (one trillion or 1012 times faster than reality). The covered time interval amounts to 320,000 years. The time propagation is then reset to present time again and the camera moves backwards at superluminal velocity allowing to see the Hyades and their tidal tails. By orbiting around the star cluster, one gets an impression of its three-dimensional structure. The tidal arms are oriented parallel to the plane of the Milky Way and can be easily recognised.

This video was produced for ESA/Gaia/DPAC by Stefan Jordan and Toni Sagrista with Gaia Sky, a visualisation software developed at the university of Heidelberg.

 

References:

 

Credits: S. Jordan and T. Sagrista for the video; story based upon the work by S. Meingast and J. Alves and upon the work by S. Röser, E. Schilbach and B. Goldman.

[Published: 20/12/2019]

 

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.