163693 Atira

As mentioned in a recent post on observing Atira-class minor planets, I had tried to observe Atira herself last fall but was not able to pick it up. So I was interested to spot it on the MPC Bright Recovery List a few weeks ago, where it looked like it would be observable from the Slooh Canary Island Observatory.

I scheduled a couple of sessions before dawn on the night of 7 Feb and was glad to see nice images come back. But they were quite crowded with stars! Turns out the object was near the edge of the Milky Way between Cygnus and Lyra. Still, the object was clearly visible and did not overlap any stars in a few of the images, so I was able to measure and submit a few observations from that session. I was successful again a couple of nights later, so there are visible observations on Atira from a couple of nights this year. The previous reports are from May 2015.


Atira is numbered and has an uncertainty factor of 2, so the orbit was not updated by the MPC. Still, it’s probably useful to confirm she is on track!

A few days later, I happened across the Arecibo Planetary Radar Science page and saw that they had observed Atira by radar a couple of weeks earlier on 20 Jan. At the time, she was passing 0.20 AU from Earth and reaching zenith around 1 PM, so I’m guessing they acquired the radar data during the day.

In the radar return image, a small satellite to Atira can be seen nearby, so the group discovered that 163693 is a binary system. From a Twitter posting on the finding:

It looks like Atira is continuing to move away from the Sun and should be well situated to try again on or after the next New Moon, so I’ll try to follow up.

I’ve made observations of a few other close approachers in 2017. In January I tried to pickup the NEO Confirmation object LM06iuE and was able to find it. I submitted the observations the following morning and just made the discovery publication for 2017 BQ6. The new Apollo-class PHA was first observed by the Space Surveillance Telescope, Atom Site on 2017-01-26. The NEO is estimated to be around 180m in size and passed by Earth at around 6 LD (Lunar Distances) on 7 Feb.

2017 BQ6 was imaged by the Goldstone radar site at that approach, showing a rough, jagged body compared to Dungeon and Dragon dice! It’s been a few years, but I seem to recall the game having a number of different kinds of dice. I suppose they meant the 20-sided die, but they did not mentioned whether or not we’d get a save through if 2017 BQ6 is ever on a collision course, as they measured it to be around 200m across.

More recently, I reported observations on 2017 BW which was pinged by Arecibo on 14 Feb. It was also imaged at Goldstone over several days and estimated to be around 40 m across on it’s longest axis. I also happened to catch 2015 BN509 which was imaged from Arecibo as well.

Though it was pure coincidence, it’s nice to see that a few of my recent observations may have contributed to refining the orbits of these radar candidates. Will have to keep an eye out on the radar groups’ sites to check for more!




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