Searching Asteroids via TiDO

A contributed talk for Workshop: From KBO to JFC: Small Icy Bodies in the Solar System on May 24, 2019

Transcript

1. Wang Mutian, the school of Astronomy and Space Science, Nanjing University Searching Asteroids via TiDO
2. 1 Introduction to TiDO 2 Methods to seek asteroids 3 Prospect
3. Site Location Ali, Xizang Province （80°E，32.3°N） Altitude: 5050m Time Domain Telescope （TiDO） Construction Timeline 2017.12 - out of factory 2019.12 – finished installation and start to function
4. Equipment Composition Telescope Aperture Field of View Pixel Scale Limited Magnitude 30 cm x 3 64 7” 16 @ 10s 18 cm 144 10.5” 15 @ 10s 100 cm 9 1.75” 19 @ 30s 30 cm 0.1 1.2” 16 @ 10s
5. Scientific Targets & Performance Performance • TiDO has better precision for 10-20 d period exoplanets. • For 18cm, 10s exposure guarantee 1% photometric precision Scientific Targets • Exoplanets • Binaries and Variables • Asteroids in solar system • Microlensing events • SN, GRB…
6. Peripheral Support Automated Observation • Observation conditions monitoring • Diary record and warning • Client app control • Data cloud storage Now in a fine weather condition, a night’s observation can produce 60GB data.
7. Searching Asteroids via TiDO Occultation Long distance objects e.g. KBOs Direct Imaging Short distance objects e.g. main belt asteroids NEO
8. My Undergraduate Research Seek Asteroids in the Solar System using data retrieved from TiDO Advisor: Prof. Liu Huigen Data Conditions • Observations lasted from 5th to 21st, May 2018 • 18cm Telescope, each exposure time 10s, nearly 150000+ stars • Field of View: 12 deg^2 • Field Center: Ra , Dec (around the ecliptic) 2018 May, 5th – 2018 May, 21st
9. My Undergraduate Research Seek Asteroids in the Solar System using data retrieved from TiDO Advisor: Prof. Liu Huigen Basic Procedure Use Astrometry and SExtractor to extract sources with coordinates information. Identify moving objects. Compare the results with MPC database.
10. My Undergraduate Research • Star lists Information Combination • Hough Transform Ø Detect line segments (Comets, trajectories of asteroids). Ø Divide the image by parts to employ the transform. List1 List2 … List1384 List1385 Combine ONE Simplified FITs (no PSF, no background only the coordinates and flux information) FITS1 FITS2 … FITS1384 FITS1385 Extract Advantage: 1, easy to remove bright stars. 2, the trajectories are evident
11. My Undergraduate Research • Hough Transformation
12. Hough Transformation Example 21P/Giacobini-Zinner Peak
13. Problems & Improvements • Some stars may naturally align, mistake as asteroids tracks. • Track points may scatter along the track lines, Hough Transformation is thus considered inefficient. • Attach the time sequence info, compare the correlation between positon deviations and elapsed time. • Examine the dispersion of the stars to make calibrations Problems Improvements Aligned stars Moving object’s trajectory Star dispersion
14. Features of Occultation 𝑡!""#$%&%'!( = max(𝐷)%&* , 𝐷&)%+*!', ) 𝑣 typical value is 10~100ms ⃗ 𝑣&)% ⃗ 𝑣+&* 𝑛+) ⃗ 𝑣&)%
15. Features of Occultation 𝑡!""#$%&%'!( = max(𝐷)%&* , 𝐷&)%+*!', ) 𝑣 typical value is 10~100ms ⃗ 𝑣 = In Kepler’s law, 𝜔+&*%- 𝜔&)% ~ 𝑅&)% 𝑅+&*%- ..0 ~300 Two modes of observation 𝑛+) ⃗ 𝑣&)% ⃗ 𝑣+&* 𝑛+) ⃗ 𝑣&)% 1、 ⃗ 𝑣!"# dominated 2、 ⃗ 𝑣"$% dominated ⃗ 𝑣+&*
16. Geometry of the Occultation Events …… …… 30AU~50AU KBOs Some stars will be blocked by the trajectories of the KBOs
17. Estimates of the Occultation Events • Extend the applicable range of R down to 1km. • KBOs uniformly distribute at the distance of 30AU and 50AU. • Every round of observation lasts for 3 months, only surveys the ecliptic plane. 1 𝐹𝑜𝑉 6 𝑅&)% 𝑑 · 𝑉1 · 𝑇 𝑑 · 𝑑𝑁 𝑅 = 0.24 N( > R ) ∝ 𝑅!" R>30km, Schlichting et al (2013)
18. Occultation Differences between asteroids occultation and exoplanets transits Asteroids Occultation Exoplanets Transits • Timescale: ~1ms • Light curve drop: ~100% • Maybe accompanied with a 2nd occultation, caused by its company • Rarer than the exoplanets transit • Timescale: ~10m to 1hr • Light curve drop: ~0.1~1%
19. Exposure Time v.s. Time Resolution Flux 1.0 0.5 0.1 Time x x x x x x x x x x x x x x x x x x x Flux 1.0 0.5 0.1 x x x x x x Time Shorter Exposure Longer Exposure • The more stars can be detected • The lower the time resolution will be • The fewer stars can be detected • The higher the time resolution will be
20. Issues in Solar System Ø Monitoring and early warning of PHO ( >140 m NEO, LSST: >90%) Ø Components and chronology of MBA Ø Water/Organic matters on Main Belt Comets？ Ø Different D/H ratio at different locations. ... In cold ( ≤ 30 K) gas, deuterium fractionation occurs (Cecilia Ceccarelli et al. 2014) Scientific Issues • Formation of Asteroids • Origins of Water on Earth • Chemical Evolution
21. Issues in Outer Kuiper Belts Ø How many objects outside KB? Ø What's the mass beyond KB? Ø Where is the Planet Nine? Ø What is the Oort Cloud’s structure? Scientific Issues • Condensation of Dusts • the Growth of Planetesimals • Formation of Embryos, Proto-planet • the Dynamical Evolution History Caltech / Robert Hurt
22. Summary • Nanjing University’s Time Domain Observatory aims at many targets, such as exoplanets and asteroids detection. • I developed a detection algorithms of moving objects for TiDO (and still working on it), including identification part and possible optimizing • TiDO will also detect occultation events in the future. Estimate of such events is . • The design of observation mode for occultation is under way. • Many issues related to asteroids in Solar Systems and outer Kuiper Belts need to be addressed, missions are expected.
23. 南京大学普通本科招生办公室 谢谢聆听 Thank You