Updated RECON coverage for our next official campaign: 2018 July 8 UT – Quaoar.
Over the course of four nights in April and May, the RECON team was able to use Apache Point Observatory’s Astrophysical Research Consortium Telescope Imaging Camera (ARCTIC) on the 3.5-meter ARC telescope to more accurately determine the positions of 31 trans-Neptunian Objects (TNOs). The objects that were observed had high uncertainties in their known orbits that limited our ability to predict occultations. By taking three separate exposures spread out over multiple hours, each object can be seen moving across the sky relative to the stars. By then measuring the object’s position as it moves through the night, a more accurate orbit for the object can be defined, resulting in more accurate occultation predictions. This is an important step in the occultation prediction process. The goal of these measurements is to identify the occultation events with a nominal 30% probability of success.
Drs. Rodrigo Leiva (RECON Postdoctoral Researcher) and John Keller (RECON Co-PI) observed at Apache Point Observatory on April 16-18, 2018. During the first night, they were trained on the APO 3.5-meter telescope by New Mexico State University astronomer Dr. Candace Gray. They then collected astrometry data for 14 out of 21 during the morning hours of the subsequent two nights.
For May 18th and 19th, Rodrigo remotely observed from Boulder with help from new RECON student research assistants Sean Haley, Lizzie Wilde, and Ryder Strauss while John was in Washington DC remotely controlling the telescope. After taking flats, darks, and bias frames, science images started to roll in. The objects observed were between magnitude 20-23 and were observed 3 times over the course of both nights. Each exposure of the same object was taken long enough apart so that the object had moved at least three arcseconds across the sky from the previous exposure. Sean, Lizzie, and Ryder looked through all the science images as they came in to make sure they were good to use (no weird light artifacts) and to confirm that the object was in the frame. Each object was found by assigning a pixel color (red, green, and blue) to the three images taken of each object and combined to make a color image that is useful to find moving targets – can you guess why? An example of what is seen with this method is shown below. 17 out of 18 objects were successfully recovered and put into the RECON occultation prediction system.
The occultation prediction system has also now been updated with the new, much more accurate, Gaia DR2 (Data Release 2) data, shown here. With an incredible increase in positional accuracy (three orders of magnitude more accurate than previously measured!) provided by Gaia, the uncertainty of star locations is no longer a significant factor in our occultation predictions. This means there are more accurate occultation predictions than ever before, which is great news for the future of RECON! Overall, 31 TNO positions were improved to bring the uncertainty in their orbits down to ~0.1 arcseconds. All of these objects are now updated in the system with the new more accurate orbit information gained in these observing runs. They are now accurate enough to potentially provide us with some great occultation opportunities in the future.
The 2017-18 academic year started off strong with our Annual RECON Team Meeting in Sunriver Oregon in late October and an occultation event in November involving Centaur 01SQ73. However, since then we have not had any high probability TNO occultation events to pursue as a network. We wanted to briefly explain why and share what we have been working on to address this.
Up through January 2016, RECON Principal Investigator Marc Buie had successfully competed for routine use of the Mayall 4-meter Telescope at Kitt Peak National Observatory to monitor the positions and orbits for TNOs that feed into our RECON occultation prediction system. However, the Mayall Telescope has been undergoing a significant mission reconfiguration over the past two years to focus on the 3-D structure of the universe to investigate dark energy.
While this involves cool science, the downside has been that the facility is no longer available to RECON and other projects previously using the telescope facility. With the resulting loss of telescope time for monitoring TNO positions, we have seen a significant drop in our ability to predict high-probability TNO occultation opportunities this year. Hence, no official, full-network RECON campaigns since November.
To address this, Marc Buie and Rodrigo Leiva at SWRI and John Keller (now at Fiske Planetarium at the University of Colorado Boulder) have been working over the past several months to obtain observing time on other telescopes to collect more positional data for our TNO prediction system. Toward that end, RECON was recently awarded 4 half-nights with the 3.5-meter telescope at Apache Point Observatory in New Mexico. Weather permitting, we hope to measure as many as 70 TNOs in April and May with this facility.
We have also obtained 4 hours for a pilot program with the Gemini North 8-m Telescope located in Hawaii. With this telescope, we expect to observe 5-6 TNOs, focusing on much fainter objects.
During the middle of March, we observed the first three objects of this Gemini study and analyses are on the way. Shown below is a stacked image of one of these objects taken at three different times during the night. The white objects are stars, while the red, green, and blue dots are the the same object changing positions with each exposure, a TNO moving relative to the background stars!
We also have monthly time allocated on the 4.3-meter Discovery Channel Telescope (DCT) at Lowell Observatory in Flagstaff, Arizona, and another proposal was recently submitted to observe more than a 100 TNOs with our Canadian colleagues at the 3.6-m Canada France Hawaii Telescope (CFHT) telescope.
Another important development coming up in less than a month is the second data release of the Gaia mission headed by the European Space Agency on April 25. This catalogue will provide ultra-high precision position and proper motion information for over 1.3 billion stars.
Because occultation predictions depend on known positions of both the target star and occulting object, both the Gaia dataset and our TNO monitoring efforts described above should get us back on track to our proposed cadence of 6-8 occultation campaigns per year by the start of the next school year.
So what should RECON teams expect before the start of summer? There are currently five potential TNO campaigns in our prediction system on the following four dates before the end of the school year (5/10, 5/24, 5/25, 6/8, all UT dates). Clear skies permitting, we plan to measure the positions of all five of these objects on April 16-17 from Apache Point Observatory (along with an additional 60ish objects). We will use this data and the Gaia dataset to update our prediction system by the end of April, and we will let our RECON teams know by early May if any of these five become high probability events that we would like to pursue. This is a classic example of how additional and higher quality data can used to obtain better predictions to drive further science.
Finally, looking ahead to the summer, it is also very likely that RECON will participate in an important occultation opportunity involving Pluto. This event will occur on August 15 around 05:32 UT, and RECON is very well positioned to provide valuable data during this event. Additional information on this and other TNO and Centaur predictions is available on the ERC Lucky Star Project prediction page.
Rodrigo and John are planning to blog from the Apache Point Observatory the nights of April 17 and April 18. We will keep you posted on how this observing run goes and the resulting impact on future TNO predictions. Stay tuned!!
On February 3rd the RECON projects leads announced an optional observing event for asteroid (191) Kolga for the evening of Feb. 9th. The specifics of this event was also noted on Occult Watcher (OW) which provided many of the event details, like potential observing station information, path maps, data on the occulting asteroid and target star, etc. What many may not know, is that on the evening of Feb 9th, another event involving asteroid (154) Bertha was also predicted to occur approx. 17 minutes later then Kolga, over much of northern California and northern Nevada. The prediction paths for these two events crossed some 40-50 km northeast of Reno, Nevada. For my typical observing station in Gardnerville Nevada, I was NOT in the predicted path of either of these events, (although inside 1 sigma for the Bertha event). After some evaluation of the events and the possibility of observing positives for both, I decided to “go mobile” with an 8” SCT and attempt observing both events from a location near Lahonton State Recreation Area, which is northeast of Carson City (approx. 56 km). For this location OW predicted that I had a 78% positive observing probability for Kolga and a 98% probability for Bertha. The LiMovie generated light curves for these observations are below.
As can be seen, I was fortunate enough to record occultation events for both Kolga and Bertha. For Kolga the duration was 5.74 seconds and for Bertha 5.34 seconds. It is a rare opportunity that two events are predicted for the same evening so close in time and so close together, location wise. For me, it was even more surprising that, none of other potential obstacles to making these observations (travel, weather, setup, etc.), got in the way of a successful evening.
For those of you that weren’t able to view the early morning event, forgot about it, or maybe just didn’t care, I offer the attached composite image as seen from Gardnerville, Nevada. The lunar eclipse started around 11:48 UTC (03:48 PST) and the moon was completely within the earth’s shadow about an hour later. We had partly cloudy skies with varying levels of cirrus over the Carson Valley. The moon was approximately 36 degree above the western horizon at the start and set before coming completely out of the earth’s shadow. For those interested in the specifics of the captured images; each of the three images in the composite were taken with a Canon EOS 80D with a Tamron 150-600 mm G2 zoom at 600mm (APS-C sensor – 1.6 crop factor – 960mm equivalent focal length). Exposures for each of the images are: 1/500 sec. (left image), 1.6 sec. (middle image) and 4 sec. (right image) at f/6.3. The camera and lens system were mounted on an EQ mount for the last images due to the necessary length of exposure.
This evening, Friday December 8, RECON is holding an optional campaign to record TNO 07TH422 starting around 5:10UT (9:10PM Pacific / 10:10PM Mountain).
Apart from a system up in Washington, sky conditions are looking excellent for all sites south of the Dalles!
Team members can check out local sky predictions on our Sky Conditions Page.
Good luck tonight!!!