Image of the Week

 

The 7 October 2021 stellar occultation by the Neptunian system

(the first large scale study since Voyager 2)

 

 

Figure 1: Left: Geometry of the Neptune occultation of 7 October 2021, shown at the geocentric closest approach at 06:53:08.9 UT. Dark and light grey areas are in the night and twilight, respectively. The dots along the thick central blue line show the motion of Neptune’s shadow centre every minute, whereas the other two thinner blue lines show the N and S shadow limits. Observations were organised from Hawaii, North, Central, and South Americas, using large and medium-sized telescopes. Right: Neptune Viewer (FoV 10”×10”) at the time of occultation over which the Earth’s motion projected onto Neptune is plotted. The blue arrow indicates the direction of motion. The occultation concerns the Adams (outermost) and Le Verrier rings as well as Neptune’s southern hemisphere (probing its atmosphere).  Three time stamps for the event (6:00, 7:00, and 8:00 UT from right to left) are indicated on the plot as reference. This figure also shows that the occultation by the arcs (represented in thicker black lines along the outermost Adams ring) is not observable from Earth. Image credit: Lucky Star Project

 

On October 7, 2021, The Lucky Star team at Observatoire de Paris (France) led and organised the largest occultation and imaging campaign by the Neptunian system ever undertaken since the Voyager flyby in 1989. This occultation event was observable across the Americas (North, Central, and South) as well as in Hawaii, and the campaign involved all large telescopes in the region that were equipped with fast cameras either in the infra-red K band (2.2 μm) or in the visible using a CH4 filter at 890 nm.

Several historical occultations by Neptune have been observed throughout the 1980s up to 1990. However, as Neptune has since been receding from the Galactic plane, predicting such events became difficult. An occultation with only one station was, however, observed in 2008.

The prediction of the October 2021 event was made possible thanks to the Gaia EDR3 catalogue. The occulted star is Gaia EDR3 2633285513360476416, for which the highly accurate Gaia position and proper motion contributed to the prediction.

This work was led by the Lucky Star team: Damya Souami and Bruno Sicardy (LESIA/ Observatoire de Paris), Josselin Desmars (IPSA/IMCCE/ Observatoire de Paris), and Jean Lecacheux (Observatoire de Paris). A total of 15 large and medium-size telescopes were mobilised for the event: the largest telescopes in Hawaii (CFHT, IRTF, Keck, Gemini North), Arizona (Large Binocular Telescope - LBT, Vatican Advanced Technology Telescope - VATT), Las Cumbres Observatory - LCO (LCO McDonald in Texas and LCO at Cerro Tololo Observatory in Chile), Mexico (San Pedro Martir), Peru (Observatorio Astronómico de Moquegua), in Chili: Gemini South, VLT/UT3 & UT4 at ESO, NTT/ESO, and MPG 2.2m telescope. The work was conducted with 45 collaborators across Europe (France, Germany, Italy, and Spain), South Africa, Canada (Université de Montréal), USA (UC Berkeley, LBT, VATT), Peru, Mexico, Brazil, and ESO (Paranal and La Silla).

This October 2021 occultation campaign, coming more than thirty years after Voyager, allows to search for any variation in the distribution of the rings (e.g., searching for clumps, small co-orbital satellites, and confined material) and to probe the upper atmosphere of Neptune.

Figures 1 and 2 allow to grasp the spatial dimensions of the problem. While Earth’s diameter is ~12,100 km, Neptune’s diameter is over 4 times that value, namely ~49,500 km. The occultation event was observable across the Americas and from Hawaii. Given the aforementioned dimensions, this means that a global telescope coverage from North to South would only allow to probe about half of Neptune’s southern hemisphere.

Nine telescopes (in the northern and southern hemispheres) have already confirmed that high-quality data were successfully obtained. The data analysis has begun and looks very promising so far.

 

References and further reading:

  • Hubbard, W. B., et al. 1986. "Occultation detection of a neptunian ring-like arc" Nature 319, 636 – 640
  • Sicardy, B., et al. 1991. "Neptune's rings, 1983-1989: Ground-based stellar occultation observations I. Ring-like arc detections" Icarus 89, 220 – 243
  • Smith, B. A. et al., 1989. "Voyager 2 at Neptune: Imaging Science Results" Science 246, 1422 – 1449
  • Hubbard, W. B., et al. 1987. "Oblateness, radius, and mean stratospheric temperature of Neptune from the 1985 August 20 occultation" Icarus 72, 635 – 646
  • Lellouch, E., et al. 1986. "Occultation determination of Neptune's oblateness and stratospheric methane mixing ratio" Nature 324, 227 – 231
  • French, R. G., et al. 1998. "Neptune's Stratospheric Winds from Three Central Flash Occultations" Icarus 136, 27 – 49
  • Roques, F., et al, 1994. "Neptune's upper stratosphere, 1983-1990: ground-based stellar occultation observations III. Temperature profiles" A&A 288, 985 – 1011
  • Uckert K., et al., 2014. "An investigation of the température variations in Neptune's upper stratosphere including a July 2008 stellar occultation event" Icarus 232, 22
  • de Pater, I. et al., 2005. "The dynamic neptunian ring arcs: evidence for a gradual disappearance of Libert_e and resonant jump of courage" Icarus 174, 263 – 272
  • Renner, S., et al., 2014. "Neptune's ring arcs: VLT/NACO near-infrared observations and a model to explain their stability" A&A 563, 18
  • de Pater, I., et al., 2018. "The Rings of Neptune" Planetary Ring Systems. Properties, Structure, and Evolution, 112 – 124

 

 

Credits: ESA/Gaia/DPAC; D. Souami, B.Sicardy, J. Desmars and J. Lecacheux from the Lucky Star Project (Observatoire de Paris, France), I. De Pater from UC Berkley California, USA; M. Langlois from Université de Lyon, France; S. Renner from IMCCE, Université de Lille, France; E. Lellouch from Observatoire de Paris; L. Albert from Université de Montréal, Canada; A. Sickafoose from the Planetary Science Institute (PSI) & Massachusetts Institute of Technology (MIT); R.A. Leiva Espinoza from U. de Chile; V. Ivanov from ESO München, Germany, A. Conrad and C. Veillet from Large Binocular Telescope Observatory, AZ, USA; R. Sfair from São Paulo State University, Brazil; from the Lucky Star Project  in Brazil: G. Benedetti-Rossi (São Paulo State University, Brazil) and F. Braga-Ribas (Federal University of Technologym Curitiba, Brazil);  L. Rousseau-Nepton, M. Baril, T. Vermeulen, N. Mansat, D. Devost, from the Canada France Hawaii Telescope, CFHT, Hawaii; J-B. Kikwaya Eluo, P. Garbor, R. P. Boyle, C. Hergenrother from the Vatican Advanced Technology Telescope, AZ, USA; T. Lister from Las Cumbres Observatory;  A.W. Stephens, T.~Seccull, R. Salinas, Z. Hartman from the Gemini Observatory;  J. Marques-Oliveira, T. Santana from the Lucky Star Project (Observatoire de Paris, France);  J-L. Ortiz, R. Duffard, M. Kretlow, P. Santos-Sanz Santana from the Lucky Star Project (Instituto Astrofísica Andalucía, Granada, Spain); L. Mancini and R. Gredel from the Max Planck Institute for Astronomy, Heidelberg;  A. Hempel Universidad Andrés Bello, Chile.

 

Published: 22/12/2021

 

Image of the Week Archive

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.