OT: imaging the close flyby of Amor asteroid (3122) Florence

On 1 September 2017 near 12:06 UT the Amor class Near Earth Asteroid (3122) Florence made a relatively close approach to Earth. The nominal pass distance, 0.047 AU or about 18 Lunar distances, was a safe distance. It does not often come this close: the asteroid had last been about similarly close in 1930, and will not be really close again until 2057.

(3122) Florence is one of the more rare larger NEA's. It is about 5 km in diameter and currently has a theoretical MOID (Minimum Orbit Intersection Distance) of 0.044 AU, only slightly less than the pass this year.

While this is a safe distance for now, orbital disturbances in the (distant) future could bring it closer, and the size of the object is such that it would be of future impact concern. It is therefore on the PHA list, where PHA stand for "Potentially Hazardous Asteroid" (for some reason, I always make "Potentially Hostile Asteroid" of this in my mind, probably because of the similar "Potentially Hostile Aircraft").

(3122) Florence became quite bright during this close pass, and was visible in binoculars at a maximum brightness of about magnitude +8.7 just before the moment of closest approach.

About 1.5 days after the moment of closest approach, near local midnight of September 2-3, I imaged the fast moving asteroid from Leiden with my Celestron C6 telescope. It was about mag +9.1 at that time. The movie above, and the stacked image below, was made from 87 images (each an exposure of 10 seconds with a 5 second interval) taken over a 17-minute period between 22:31:32 - 22:48:47 UT (Sep 2).

The asteroid was at a distance of 0.048 AU at that time and moving fast through Delphinus, at an angular speed of about 22".5 per minute.

The equipment used was a Celestron C6 (15 cm) Schmidt Cassegrain telescope with F6.3 focal reducer, and a Canon EOS 60D DSLR at ISO 3200 in the prime focus of the telescope.

(the satellite that can also be seen zipping past in the movie, is a Russian GLONASS, Kosmos 2425)

stack of 87 images taken over a 17-minute time interval
(click image to enlarge)

An 'asteroid' that wasn't: the Chinese Chang'e 2 upper stage (2010-050B) imaged at almost twice the Lunar distance

WJ297AD = Chang'e 2 r/b. Images (c) Peter Starr, Australia

On 7 May 2015 near 7:35 UT, the Catalina Sky Survey (MPC 703) in Arizona detected a bright mag. +17  fast moving object moving at about 12"/minute through Virgo. The object was reported as a potential Near Earth Asteroid and entered the NEO Confirmation Page (NEOCP) of the IAU's Minor Planet Center with temporary NEOCP designation WJ297AD.

Some 6 hours later, Peter Starr at Warrumbungle Observatory (MPC Q65) in Australia targetted the object with his 0.51-m Dall-Kirkham telescope, in order to confirm it and obtain more positions.

As he often does with NEOCP objects he images, Peter sent the imagery to me for astrometric processing.

image (c) Peter Starr. Click image to enlarge

After I measured the images (a part of one is shown above, showing the object as a short trail amidst the stars) and tried to fit an orbit to the astrometry obtained from Peter's images and the Catalina Sky Survey observations, the result was odd.

FindOrb suggested that this object was in orbit around the Earth, in a trans-lunar orbit with perigeum at  352 666 +/- 426 km, apogeum at 552 356 +/- 934 km, an orbital inclination of 41 degrees and an orbital period around the Earth of 35 days! The MPC itself, fitting several preliminary orbits, also presented solutions pointing to an object in an odd, very earth-like orbit with semi-major axis about 1.05 AU and a heliocentric orbital period of ~1.0 year.

At that time, after an initial "Huh? That's odd..." I already developed some feeling that this might perhaps be an artificial object, if this fit was not spurious. I was not sure though (preliminary orbit fits to small observational arcs can come out weird on occasion), so I sent Peter an e-mail mentioning that it was a "weird object that seems to be in a very Earth-like orbit".

Meanwhile, another asteroid observer, Jacques Cristovao, also thought that this NEOCP object was odd. Around the time Peter was doing his observations from Warrumbungle, Cristovao suggested in a message on the Minor Planet Mailing List that the object was artificial, and specifically was 2010-050B, the upper stage of the Chinese Chang'e 2 Lunar probe.

That turned out to be correct: WJ297AD indeed is the rocket stage from this launch.

This rocket stage moves in a very wide translunar orbit with perigeum close to one lunar distance, and apogeum at almost twice the Earth-Moon distance. At the time of the observations it was near apogee at a distance of about 535 500 km, well beyond the moon at almost twice the Earth-Moon distance.

Chang'e 2 orbit in the Earth-Moon system (based on May 7 observations)

The rocket stage was used to bring the second Chinese Lunar mission, Chang'e 2, into a temporary orbit around the moon. Chang'e 2 itself later left the Earth-Moon system for a journey to asteroid Toutatis, but the rocket stage it left behind is still in orbit around the Earth-Moon barycenter.

It was not the first time that the Chang'e 2 rocket  was initially confused with a Near Earth Asteroid. The same happened in 2013 when the rocket was briefly known as 'asteroid' 2013 QW1.

These days, even the asteroids are Made in China....

OT: another update on NEA 2015 CA40

 
Our Near Earth Asteroid discovery (see earlier post) 2015 CA40 is now past it's point of closest approach. It reached that point, at 6.3 lunar distances, on Feb 23 near 21:49 UT.

The animated GIF above shows the asteroid early on Feb 24, about 12 hours after closest approach, imaged with the 0.61-m F/10 Cassegrain of MPC G68 Sierra Stars Observatory in California, USA. The animation is made from 6 images taken over a 10-minute timespan. Each image was 30 second exposure, and the images were separated by 2 minutes.

The observed orbital arc of the asteroid now extends from Feb 15.93 to  Feb 24.58, or 8.5 days. Updated orbital elements from the MPC (MPEC 2015-D86, 26 Feb 2015):

Epoch 2014 Dec. 9.0 TT = JDT 2457000.5
M 298.05944              (2000.0)
n   0.84818796     Peri.  176.19408    T = 2457073.52693 JDT
a   1.1052859      Node   334.93169    q =     1.0044127
e   0.0912644      Incl.   15.06659    Earth MOID = 0.01553 AU
P   1.16           H   24.6
From 147 observations 2015 Feb. 15-24, mean residual 0".74.

13 observatories have now contributed to the observations, including our own MPC 461 Piszkéstetö where we discovered the object, and two observatories I used myself for 'remote' observations: MPC G68 Sierra Stars Observatory in the US and Q65 Warrumbungle observatory in Australia. The full list of contributing observatories (up to 24 Feb 2015) is:

461   Piszkéstetö Stn. (Konkoly), Hungary
J95   Great Shefford, UK
246   Klet obs. KLENOT, Czechia
J69   North observatory, Clanfield, UK
703   Catalina Sky Survey, USA
F65   Haleakala-Faulkes Telescope North, Hawaii, USA
C47   Nonndorf, Austria
G68   Sierra Stars Observatory, Markleeville, USA
474   Mount John Observatory, New Zealand
A48   Povegliano Veronese, Italy
B18   Terskol, Russia
Q65   Warrumbungle, Australia
W87  Cerro Tololo-LCOGT C, Chile

The asteroid is currently only observable from the southern hemisphere.

OT: An update on Near Earth Asteroid 2015 CA40

2015 CA₄₀, the Amor Near Earth Asteroid discovered by Krisztián Sárneczky and me with the 0.60-m Schmidt telescope of MPC 461 Piszkéstetö (Konkoly) in Hungary on Feb 15, 2015 (see previous post) has now been observed for a week.

The animated GIF above shows the asteroid zipping through the FOV of the 0.61-m Cassegrain telescope of MPC G68 Sierra Stars Observatory in Markleeville, USA, in the morning of Feb 21. It was made from 5 images of 30 seconds exposure each, separated by 5 minutes each. A single frame from this sequence (taken 21 Feb 2015 at 09:45 UT) is below. Even at a relatively short exposure of 30 seconds, the asteroid has trailed:

With an observational arc of over 6 days, the orbital solution already is much better than it was when the discovery MPEC was issued. A number of observatories have now contributed to the observations. As of 22 February, these included, apart from our observatory MPC 461 Piszkéstetö (Konkoly):

246 Klet obs. KLENOT
703 Catalina Sky Survey
C47 Nonndorf
F65 Haleakala-Faulkes Telescope North
G68 Sierra Stars Observatory, Markleeville
J69 North observatory, Clanfield
J95 Great Shefford

The G68 observations are 'remote' observations by myself (see images above) on Feb 21.

Current orbital elements (source MPC, MPEC 2015-D57 of Feb 22):

Epoch 2014 Dec. 9.0      TT = JDT 2457000.5 
M 298.04783 (2000.0) 
n 0.84852056     Peri. 176.17901      T = 2457073.51198 JDT 
a 1.1049971      Node 334.93125       q = 1.0043903 
e 0.0910471      Incl. 15.04633  
P 1.16           H 24.5             Earth MOID = 0.01551 AU

From 104 observations 2015 Feb. 15-21, mean residual 0".54.

When we discovered 2015 CA₄₀ on Feb 15 it was at 15.6 lunar distances. Tomorrow near 21:48 UT (Feb 23, 2015) it will have its closest approach, to 6.3 lunar distances. In the days following this it will move out of view of the Northern hemisphere, but I hope to be able to follow it a few days using the 50-cm telescope of MPC Q65 Warrumbungle Observatory in Australia.

NASA has placed 2015 CA₄₀ on the NHATS page. This page lists objects in orbits suitable for potential future crewed space missions. NHATS stands for Near-Earth Object Human Space Flight Accessible Targets Study.

Last but not least, a picture of the 0.60-m Schmidt telescope at MPC 461 Piszkéstetö (Konkoly) in Hungary with which we discovered the asteroid (image Krisztián Sárneczky/Miclós Rácz):

For those able to read Hungarian (or use Google Translate), a nice story about the discovery in Hungarian is here. Stories in Dutch are here, here and here (and of course my previous blogpost).

OT: the discovery of Near Earth Asteroid 2015 CA40 (updated)

Satellites is not the only thing I dabble with: as some long-time readers of this blog know, I am also involved in asteroid searches.

Since 2012 I am part of a small team that searches for asteroids with the 60-cm Schmidt telescope of Piszkéstető (MPC 461, Konkoly obs, Szeged university) in Hungary. The project is run by Dr Krisztián Sárneczky from the Szeged university.

My task in this project is to visually inspect the images for objects that have been missed by the automated (computerized) moving object detection routines. Typically, Krisztián sends the images to me via Dropbox within hours of the observing session. I then inspect them on my pc at home here in the Netherlands and measure any unidentified objects I encounter on the images. Over the years I have fished out a number of new main belt asteroids from our imagery.

This weekend, I found a Near Earth Asteroid in the imagery, my first NEA find in this project and my second in total (10 years ago I found NEA 2005 GG₈₁ when I was a plate reviewer with the Spacewatch FMO project).

Part of one of the discovery images from Feb 15. Note the faint trail.

We had a run of several nights with the Piszkéstető Schmidt telescope last week. On Monday around lunchtime I was inspecting images taken Sunday-on-Monday night by Krisztián at high declination (+56 degrees) in Ursa Major. Usually, images at this high a declination are devoid of asteroids. But this time I noted a small moving streak in the images near RA 14h 22m 32.6s, dec. +56 16' 37". See above for (a part of) one of the images, and the animation below. Each frame in the animation below is a 5-minute exposure.

Animation of the discovery images.

Initially I was a bit cautious. As can be seen in the animation above, the object was very faint in the first two frames and brighter in the last two. This is a bit unusual (it can be due to rapid rotation of the object, or -most likely in this case- to changing sky conditions). My first thought therefore was a high altitude slowly flaring satellite: but checking the image times it was clear that this object moved much too slow for a satellite. So: a Near Earth Asteroid?!

I mailed Krisztián the positions noting that it looked like an FMO, a fast moving NEA. Krisztián remeasured the images (measuring is difficult with trailing objects, and certainly faint trails) and sent the observations to the Minor Planet Center (MPC) of the IAU in Harvard, under our temporary object designation "SaLa122".

It was then posted on the MPC's "NEOCP" page, a webpage that lists potential Near Earth Asteroid discoveries with a request to other observatories for confirmation. Due to a mistake it initially appeared as "SaLa123" there (see below) with only 50% of our data: this was however quickly corrected and soon it was on under the correct designation "SaLa122".

SaLa122 (under the erroneous designation SaLa123) on the NEOCP

At that moment we had a 30-minute observational arc, which is very short. It was vital that the object should be recovered over the next day, otherwise the object would be regarded as "lost" and would not count as a discovery.

Luckily, that recovery happened! The next night (16-17 Feb) Krisztián managed to relocate the object with the 60-cm Schmidt (see image below) and could follow it for several hours. In addition, astronomers at the Czech Klét observatory and British amateur astronomer Peter Birtwhistle at his private Great Shefford Observatory in the UK looked for the object too and could confirm it. This expanded the observational arc to 29 hours, enough for a preliminary orbit determination.

Stacked follow-up images from MPC 461 in the night of Feb 16-17

In the late afternoon of Feb 17 the MPC made the official discovery announcement in MPEC 2015-D10: the object now has the official designation 2015 CA₄₀.

2015 CA₄₀ is a borderline Amor/Apollo asteroid with [updated 22 Feb 2015] a semi-major axis of 1.1049538 AU, an eccentricity of 0.0910145 and an orbital inclination of 15.04 degrees. The perihelion is just outside the orbit of the earth at 1.004 AU. The aphelion is at 1.20 AU, well within the orbit of Mars. The orbital period of the asteroid is 1.16 years. With H=24.5 the asteroid is estimated to be about 45 meters in diameter.

Orbit of 2015 CA₄₀

[Updated] 2015 CA₄₀ orbital elements (MPC, from MPEC 2015-D47)

Epoch 2014 Dec. 9.0   TT = JDT 2457000.5 
M 298.04901 (2000.0) 
n 0.84857047     Peri. 176.17310     T = 2457073.50630 JDT 
a 1.1049538      Node 334.93131      q = 1.0043870 
e 0.0910145      Incl. 15.04278      Earth MOID = 0.01551 AU
P 1.16           H 24.5 

From 98 observations 2015 Feb. 15-21, mean residual 0".51. 

The theoretical minimum distance (MOID) of the asteroid's orbit  to the orbit of the Earth is 0.0155 AU or about 6 times the Earth-Moon distance. Closest actual approach of the asteroid to Earth this year, to about 6.3 times the lunar distance, is in the night of Feb 23-24 when it might reach mag. +16.6 and will be moving at a speed of 42" per minute.

Objects in this kind of orbit with a semi-major axis of ~1.0 AU (similar to the orbit of the Earth) are objects that already must have had one or more close encounters with the Earth and/or Mars.

We plan to follow the object over the coming nights, to expand the observational arc as much as possible, in order to increase the chances of it being found back during the next similarly close approach, which will be on 23 February 2066. There are some earlier dates at which the asteroid comes near Earth too (indicated in the diagram below: e.g. 2022, 2029, 2037, 2044, 2051 and 2058), but at a clearly larger distance than in 2015 and 2066. It will be much fainter and hence harder (but not impossible, given a big enough telescope) to detect during those years.

click diagram to enlarge: distance (in AU) of 2015 CA₄₀ to earth over the coming century

Earlier close approaches to less than 0.1 AU over the past 200 years were in 1813 (0.0161 AU);  1849 (0.0429 AU); 1863 (0.0245 AU); 1899 (0.0773 AU); 1928 (0.0469 AU); 1950 (0.0503 AU); and 1979 (0.0665 AU).

2015 CA₄₀ is  the 7th Near Earth Asteroid discovered by the Konkoly survey and my second NEA discovery (and my first in the Konkoly project).

More on my other asteroid discoveries here.

Update (21 Feb 2015): we are still following this object and the arc now includes observations from early Feb 21.


Acknowledgement: we thank Peter Birtwhistle and the people of Klet observatory for their follow-up observations.

OT: Near Earth Asteroid 2012 LZ1 fly-by imaged, June 15

On June 10, 2012, Australian Siding Spring astronomer Rob McNaught and colleagues discovered a bright Near Earth Asteroid (NEA). It got the provisional designation 2012 LZ1 and turned out to be large: it is estimated to be about 500 meter in diameter (UPDATE 22 June 2012: radar observations from Arecibo obtained during the fly-by actually showed it to be twice as large, i.e. 1 km diameter! This suggests a low albedo, which might imply a carbonaceous composition). It made it's closest approach to the earth/moon system around midnight of June 14/15. With a pass distance of 5.3 million km (a multitude of the Earth-Moon distance), this flyby was not particularly close. But because the asteroid is large, it became quite bright, ~ mag. +13.

In the early morning of June 15, some 9 hours after closest approach, I used the "remote" 37-cm F/14 Cassegrain of UoI Rigel observatory at Sonoita, Arizona, USA (MPC 857, the same telescope that I often use to image geostationary satellites)  to image the asteroid (I also obtained some imagery using the larger 61-cm telescope of Sierra Stars Observatory in California).

click image to enlarge

The image above is a stack of 4 CCD images, each of 30 second exposure and spaced 5 minutes in time, obtained with the Rigel telescope. The asteroid can be seen as a set of 4 short trails lining up. It was moving at a rate of about 35"/minute near the Aquila-Capricorn border at that time and was near mag. +13.

Another close encounter of a rocky kind....: 2005 YU55

Half a year after the close approach of asteroid 2011 MD (see my images here and here), another one whizzed by the Earth last night. It was 2005 YU55, a 400-meter wide asteroid discovered in 2005 by Spacewatch. It came to within 0.85 lunar distances at 23:28 UT (Nov 8, 2011), with a maximum brightness near +11.

click image to enlarge

Four hours after closest approach, I made the image above, using a "remote" 61-cm F/10 Cassegrain telescope at Sierra Stars Observatory (MPC G68). It is a 30 second exposure starting at 03:21:41 UT (9 Nov 2011), during which the asteroid (moving from right to left) has trailed considerably.

Astrometry from my images has been included in MPEC 2011-V34 (the G68 observations at

09.11922, 09.14006 and 09.32778).

OT: more imagery of the earthgrazing asteroid 2011 MD

Like yesterday, I used the 0.61-meter F/10 Cassegrain of Sierra Stars Observatory (G68) in California again to image the earthgrazing asteroid 2011 MD, this time a few hours after closest approach.

Below animated GIF was made from three 30 second exposures, spaced 30 seconds, starting at 09:35:01 UTC (28 June).

OT: Close Encounters of a Rocky Kind (2011 MD)

Today, a small asteroid, 2011 MD, made a very close pass by the earth, coming to within a distance of 12,400 km at about 13:30 UTC (June 27). That is well within the distance of geostationary satellites, and even within the distance of GPS satellites in MEO!

This morning, some 5 hours before closest approach, I used the 0.61-meter F/10 Cassegrain of Sierra Stars Observatory (G68) in California, to capture this PHA earthgrazer.

click image to enlarge

This image is a 30 second CCD exposure taken between 08:32:00 and 08:32:30 UTC (June 27, 2011). In these 30 seconds, the fast moving object left a notable bright trail on the image. Star field is in Serpens, image center approximately RA 15h35m57s, dec. +19.441 degrees.

UPDATE: more of my 2011 MD imagery shot on the 28th here.