OrbBrowser – a Minor Planet Orbit Browsing Utility

In my “day job”, I’m a scientific applications developer working in the life sciences domain. I have a science background but have always used computers in one form or another in research, from time sharing main frames, to Unix workstations and servers to Linux clusters.

So I wanted to write a utility to extract orbital elements of minor planets from the flat-file distributions provided by the IAU Minor Planet Center, to help identify candidates for observation. I started with a basic PERL utility to filter the full MPCOrb data file based on input criteria. That was useful but not very exciting! So I’ve started to write an HTML/Javascript based utility to browse and filter some of the existing subsets provided by the MPC in an interactive fashion. The current version can be found on a demo site I’ve setup for the utility which is named OrbBrowser.

The site is quite simple to use. First, you need a data file in the MPC Minor Planet Orbit format containing the subset of interest. The current set of Near Earth Asteroids is available on the MPC data page in the file NEA.txt. Or you can download the DAILY.DAT file for the daily orbit updates to see what’s new and newly updated.

From the OrbBrowser site, select Choose File and select the local file of interest. After a few moments, the file should be read in and displayed in a table showing all of the fields present in the data file including orbital elements, orbital uncertainty and observation stats, etc. You can even see the published MPC “bit flags” giving the orbit type classification, PHA, NEA and critical flags.

Selecting the header of any column will sort the data by that column. At the bottom of the column are input fields to enter a min and max value for numerical fields, or a pulldown for categorical fields for filtering. So, for example, you can select U >= 2 and U <= 5 to see all objects in the data file with that range of uncertainty values. Adding another filter such as Orbit Type = Aten will intersect with the first filter to give all Atens having U from 2 to 5. And so on!

Once you have a subset of interest, you can export the filtered set back out to a file in MPC format or a text-delimited format. The MPC subset can then be loaded into a planetarium package such as C2A so you can see which objects in the list are currently visible from your favorite observing site at a given apparent magnitude limit. A text delimited export can be loaded into Excel or other data management programs to add additional information or more refined filtering and sorting.

Because OrbBrowser runs totally in a browser, there is no need to install any additional software to use the utility. However, you are subject to the javascript performance of your browser! On 64-bit Windows 10, I’ve had better luck with Chrome and Firefox for viewing the full NEA file with 15,000 some entries.

Also, you can download the main page of the site and supporting javascript and CSS files to your local desktop and run it totally off line. All of the source is available to read and it is available under an open source license, so you are free to modify it in any way and make use of it in your own site if that is of interest! See the Download and More Info tab for a link to the current ZIP archive and instructions to run it locally.

I’ve found the utility quite useful to help identify some of the Aten-class objects I’ve observed and submitted. I’ve even found and observed a couple of Atira-class bodies as well, which are totally within the Earth’s orbit and fairly elusive.

I hope OrbBrowser is of use to others. Feel free to send questions, suggestions and tomatoes to the email address listed on the site!

Screen shot example showing the current NEA.dat loaded, and filtered for Atens with U=2 through 5 to suggest potential objects that may need updating. (Of course, not all of these will be observable).

20161229-01-orbbrowser

Screen shot showing all NEA’s with U from 2 through 5 loaded into C2A with a magnitude filter. Objects can be selected that are well above the horizon – and out of the Milky Way.

20161229-02-c2a

Loading and working with the full MPCOrb database does not appear to be practical in javascript. So I’m working on another browser-based utility to filter and save subset of interest for interactive browsing. So stay tuned for a companion utility!

PHA 2016 WJ1

[Updated 3 Dec with new data available – see below]

As mentioned previously, the Spaceguard Priority List at the ESA is a great resource for finding Near Earth Objects (NEOs or NEAs) that are useful to observe – even by amateurs! The site assigns priorities to observable NEOs ranging from “Urgent” down to “Low Priority” in order to help triage candidates for the larger observatories (and others) for follow up, based upon a number of criteria.

One reason an NEA might be assigned to the Urgent category is having a narrow time window for observation. The surveys for minor planets often pick up smaller, bright objects that are only detectable because they are passing close by. These will tend to be moving fast and will only be visible for a relatively short time. So it’s important to get observations on these while they are still visible to determine a reasonably accurate orbit so they can be found again later. Also, some of these may even pass close enough to become targets for radar observation. In this case, priority visual observations can be made to help locate an asteroid well enough to point a radar at it. Radar observations can provide highly accurate locations and a variety of physical data for general research.

The fast-moving NEOs can be hard to accurately observe with the modest telescopes I have access to, so I usually don’t try for things in the Urgent category. Observations on the “Needed” and “Useful” objects are often worthwhile, and even the Low Priority objects can be useful to observe for orbit improvement. But I was interested to see an object in the Urgent category this past week that was in a brighter magnitude range (around 18) and moving at the relatively modest rate of around 2 arcseconds per minute: 2016 WJ1. Certainly doable!

2016 WJ1 is likely listed in the Urgent category because it is identified as having a potential for a close approach or impact to Earth in the distant future and is of significant size to be designated a Potentially Hazardous Asteroid or PHA. It is not uncommon for newly discovered asteroids to be placed on the JPL and ESA “watch lists” for potentially hazardous NEOs. An orbit can be estimated for a solar system object after only 1 or 2 nights observation, but this will only be an approximate orbit until the it has been observed for an extended period of time. So newly discovered minor planets are sometimes found to have potential close approaches to Earth, based on a rough orbit, and so are placed on the watch list upon initial discovery. Sort of like a quarantine! These are often removed after more data comes in and more accurate tracks can be projected. For example, in the Sentry Risk Table maintained for NASA by the JPL, one can see that dozens of minor planets discovered in 2016 have been removed from the list after follow up observations, out of the 1700 or so that have been discovered this year in total. So it’s important to get data on these objects while they are still observable to help identify, or rule out, a close approacher as being a potential threat.

2016 WJ1 was in the northern sky this past week at with a declination of around +15. This would be best observed from the Slooh.com site in the Canary Islands, but they were closed due to an extended spell of bad weather. The object was lower in the sky from their observatory in the southern hemisphere near Santiago, Chile but still observable. And the weather has been very nice there of late, with sunny summer skies and warm temperatures, so this looked to be worth a try.

So I scheduled 4 “missions” on the night of Nov 27th from Santiago and got nice images back the next morning. After solving the images in Astrometrica, I could see a very faint moving object around the expected position for 2016 WJ1. To improve the signal and get a more accurate position I was able to stack the images from each set, giving 3-4 images taken about 1 minute apart for each stack. Here’s a portion of one of these stacks showing the presumed target, circled in purple:

20161202-1-2016-wj1-stack4

In this image stack, Astrometrica is shifting each image by the expected movement of our target object. The oval-shaped objects are stars that are offset between frames because they are moving relative to the asteroid. But the asteroid lines up between the images, giving a  nice circular shape and a better defined peak. (And the fact that it does also confirms we are seeing something moving at the expected rate and direction of our target). The red box marks the area where Astrometrica expected 2016 WJ1 to be. We are somewhat off (about 1.8 arc minutes in RA) but in the neighborhood. And this offset is consistent in each image, helping to confirm we are in fact seeing an object agreeing with the expected track of 2016 WJ1.

Now Astrometrica can give us the position in the sky at each time point for each stack, so we have 4 “observations”. I then ran these through the findOrb package along with other published observations to calculate the best orbit solutions for the combined set. This gives the position at each time point plus the delta or “residual” between the observed location and the location predicted for the orbit:

16 11 28.21566 W88 04 03 52.25 +14 38 35.3 .29+ .36+ .15613 1.1416
16 11 28.22933 W88 04 03 48.37 +14 38 24.5 .41- .34- .15603 1.1415
16 11 28.25381 W88 04 03 41.58 +14 38 06.4 .51+ .13- .15583 1.1413
16 11 28.27146 W88 04 03 36.61 +14 37 53.3 .06- .17+ .15570 1.1411

In the first line, the observed and predicted positions differ by around 0.3 arc minutes in RA and Dec respectively. This is pretty good accuracy for a stacked image and should be useful data. The second and third timepoints were a little more off but the 4th is good, so I submitted the first and last lines to the Minor Planet Center through their email submission mailbox.

The observations were accepted, but I missed that publication deadline for that day. A few more positions were obtained the next night and sent in on 29 November.  Both sets were published that later day in the MPC Minor Planet Electronic Circular (MPEC) 2016-W117.

These publications are rather technical and daunting to read. A more user-friendly form can be see in the Tracking News section of the Earth’s Busiest Neighborhood site here.

What we see in the first section in the link above are observations of 6 different minor planets that have been recently discovered and being followed up as potential risks, including our 2016 WJ1. My observations from Slooh station W88 program code 7 are listed for both nights, along with data from other observatories from England, Germany, the Czech Republic and an ESA observatory in the Canary Islands. Adding in a few positions from the Southern Hemisphere is likely helpful to estimating the minor planet’s orbit as a balance to all of the other submissions from the North.

The Daily Orbit Update on the next date (MPEC 2016-W127) shows observations on 2016 WJ1 from over 10 observatories, so it’s certainly getting a lot of attention. I also submitted a third set on 30 Nov which was published in 2016-X07 on 1 Dec. As of today, there are 220 observations over a mere 12 days, so there are certainly a number of eyes on this NEO.

2016 WJ1 is still on the risk list, but certainly needs to be observed for a longer period of time to really understand how concerned we need to be about it. It’s discovery was confirmed and then published just recently on 22 November, so it’s still very “new”. It was one of 18 new designations published that day, ranging in estimated sizes from 10 meters up to 1000 meters, so it is of moderate size at around 180 meters. Fifty meters is considered to be a significance threshold in terms of potential damage, so the object is certainly worth tracking – but is not a monster! An object’s speed relative to the Earth is also highly important to consider when assessing risk.

Another factor is the number of potential encounters, which depends upon the orbit type. 2016 WJ1 is an Apollo-class minor planet which means that is primarily located outside of the Earth’s orbit but crosses it. It’s orbit is rather elongated and ranges from inside of Venus’ orbit to beyond that of Mars. In fact, it seems to make close passes to Venus, Earth and Mars on a fairly regular basis in an orbit close to the solar plane. We are seeing it now because it is in our neighborhood and will pass by at a very safe 0.05 AU (~ 5 million miles) around mid December.

It is projected to come back around in 2023 at an even safer distance but will observable. So we’ll get to check up on it again in a few years, which is re-assuring! Then it will continue to come around every 7-10 years or so for more viewing chances too, and can likely be seen in between those visits by the larger guns. Each of these approaches will help refine the orbit’s accuracy further and check against course changes caused by encounters with the 3 planets it interacts with.

A pass in 2065 looks like a close shave and that is currently contributing to much of the estimated risk. But, again, this is a very long extrapolation of a 3 week old orbit to really worry about just yet. And that fact that it is expected to make a series of close passes could well be an advantage. One could imagine launching missions to encounter it and study if further. And it could well be a good test or subject for risk mitigation – such as steering it away from us. I even wonder if somebody somewhere is thinking it might be a good candidate for asteroid mining. One could imagine valuable ore being offloaded each time it comes back in the vicinity perhaps.

2016 WJ1 is expected to have a much more rapid motion in the sky as it gets closer and then passes by over the next few weeks, so further observations are probably best left to the professional observatories. And there are always other candidates to follow up on. If the weather clears in the Canary Islands some time, I’d like to try another newly discovered ‘risk’ candidate – 2016 TF94. Unless there’s something more interesting on the list!

Update: new observations dated from 2003 were published yesterday from the observatory at Mauna Kea in MPEC 2016-X21. I’m guessing these are “pre-covery” data. When a new object of interest is discovered, observatories often go back through their data to see if was observed before. Perhaps they had seen it in 2003 but it was never confirmed and was not published as a new object at that time. But now, the older observations are found to be consistent with those of 2016 WJ1 and are now added to its history.

Now the known arc spans for about 13 years instead of a month, greatly reducing the long-term uncertainty of the minor planet’s trajectory. 2016 WJ1 was removed from the JPL Sentry list yesterday. The NEODyS close approach table shows that close approaches in the next 100 years will be just that – approaches that should safely pass us by.

More observations during this and subsequent passes will tighten this up further, but this is certainly good news!

2016 BC14 and Jupiter’s Influence

After learning about and publishing a few observations of Near Earth Objects (NEOs), I came across cool website titled Earth’s Busy Neighborhood. My day job is a scientific software engineer and I really admire this stunning example of a data aggregation web site. The main page shows an HTML5 animation of all of the NEO’s currently passing close to the Earth and also lists details on each one, gathered from the MPC observation database, JPL orbits, links to articles and other sites and all sorts of detail. Also, summaries of confirmation candidates, Minor Planet Circulars and risk updates are gathered and published in The Tracking News section each day. Apparently the authors gather data from various sources using Python scripts to generate the HTML pages. Great stuff!

Many of the objects on the tracker are relatively small, 5-10 meters, and pose little risk of global destruction. Unless they are close by, these smaller bodies are generally very faint and are only accessible to 1 meter class telescopes.

But looking through the list a few weeks ago, I noticed an object 2016 BC14 classified as “Approaching” with an estimated size over 200 meters. So I figured this would be a good one to try to catch. The MPC Ephemeris service showed it to be readily accessible from the Slooh Canary Island Observatory on Mt Teide so I scheduled a set of “missions” on 7 March to try to spot it.

I have a couple of telescopes at home I like to take out from time to time. But conditions are often unfavorable living near the shore in Southern New England. It can be nice and clear out during the day only to cloud up and dew up after sunset. And I’m not as included to handle cold metal when it’s 20 degrees F outside! Having access to remote telescopes helps greatly, but even those are subject to clouds, snow and ice and even strong winds and there was a spell of all that at the Mt Teide site earlier this month. It took over a week of trying to get a couple of nights of pictures of BC14 but I did get there in time.

At that point, the object had brightened to around mag 17 and was clearly seen in each individual image. After selecting images from each timepoint on the 2 nights, I had a set of observations for a potential submission. Even after a week of trying, the object was listed as “Useful for orbit improvement” by the MPC, probably because of it’s status as a Potentially Hazardous Asteroid or PHA.

Before submitting the observations, I ran them through the find_orb Orbit Determination package from Project Pluto. One of the many things this software can do is to read in a series of observations of Solar Systems objects (of any kind) and determine potential orbit solutions. It will also report on orbit “residuals” which is the difference between the expected position (based on the orbit determined) and the measured position for a given observation. So to check my observations, I can download the current set of published observations on the object and add in my values in order to check for discrepancy with published results. If there are enough reliable observations, I can see if any of mine are out of whack due to some error – such as picking the wrong object on the screen when recording a measurement. Ideally, my values should be in line with the published values and have a reasonable small error – under 0.5 arc seconds or better. And for a newly or recently discovered object, adding “good” observations should improve the orbit fit and reduce the overall residuals in the combined set of published and new data points.

After running my observations through find_orb, the residual values in declination were quite good, but the RA delta was consistently over 0.5 arc minutes in all cases. This looked odd, so I went back and reviewed the workup in Astrometrica to see if anything was off there. I find that Astrometrica is rather robust and either returns a very good image solution, or no results at all. (And if no fit is obtained it usually means that I selected the wrong configuration file so the scale is way off!) Occasionally I find I need to tweak the magnitude setting used to select reference stars if the field is unusually sparse or crowded but that’s about it.

Since the workup looked OK so I loaded the observations again in find_orb. The program determines the orbit of minor planets around the Sun (or other bodies) and will also calculate perturbations caused by other objects such as the planets. By default, it will determine which bodies perturbing to use automatically. The fit of 2016 BC14 gave an orbit ranging from just over 1.0 AU to 0.7, so this is an Aten class asteroid staying rather close to Earth. The package determined that mainly Earth and Luna could be perturbing the object and selected those for the fit.

But when I selected to include perturbations from all planets in the orbit, the residuals for my observations improved greatly and varied +/- 0.2 arc seconds or less for all values. By selecting and deselecting the various planets, it looked like Jupiter had a pretty strong effect on the values, and including it gave a much improved fit. So how can Jupiter have such an effect of the asteroid only goes out to 1.03 AU?

Jupiter is currently rising in the evening and is up high in the sky around midnight, so it is currently in opposition to Earth. (The exact opposition was on 8 March not too far off from the date of these observations). Jupiter is 5.4 AU from the Sun and currently about 4.5 AU from us. It’s mass is about 1 thousandth of the mass of the Sun and it is farther away from us than the Sun, so I would expect it’s gravitational pull to be over 20,000 times weaker on the body then the Sun. I’m not sure if that is enough to cause the difference in the position of the minor planet.

Of course, the position I’m seeing is relative to Earth’s place in the sky. So if Jupiter is having an effect on the Earth’s position as well that could increase the effect on the observed location perhaps. I’m not sure how to sort this out – maybe it’s a good question to ask folks on the Minor Planet Mailing List.

Anyhow, after confirming the observations I formatted the report and submitted it to the MPC – with some help again from my friends on the Slooh A-team. Since this was my first report from the Canary Island location (observatory code G40), I’ll need to have a program code assigned for that location as well. So I’ll wait and check from time to time for the observations to be published, and think about what to look for next when the moon starts waning again.

2016 EL56 – a newly discovered PHA

After having my first NEO observations accepted and published, I’ve been looking to observe some other interesting objects and thought I would try some brighter entries on the MPC NEO Confirmation Page. This page lists newly discovered minor planets or comets thought to be in or potentially reaching our neighborhood in the Solar System. Most of these are very faint bodies picked up by large telescopes used in the various sky surveys and are typically confirmed by high powered professional or amateur observatories dedicated to follow up confirmation and recovery work.

Still, a few brighter objects can be found on the list, and it looks like these are a little more common in the Southern hemisphere. So I thought it would be worth trying some of these from the Slooh observatory in Chile.

The first one I tried was a NEO candidate designated M50sG6S on the list on March 8th. It had an estimated magnitude of 18.2 and a projected declination of 35S so it looked like it should be detectable from Chile. I scheduled missions from W88 that night but did not see any moving object in the images obtained. No confirmations were made for this object over the coming week so it was removed from the list and not confirmed.

The next day, I saw an entry A100jOx in the southern sky with an estimated brightness of 18.9 at declination 25S. This magnitude is a bit of a stretch but it looked to be fairly high up in the sky on a moonless night so I gave it a go. Image files came in the next day, and I also noticed that the object had already been confirmed and given the designation 2016 EL56 by checking on the previous designation page. So other observatories had already confirmed the object!

The images looked quite good, so I took a look in Astrometrica to see if I could pick up the new object. First, I updated the MPC orbit database since the object was just designated and should now have an orbit available. A faint moving object was seen in most of the images, near but not at the exact location predicted by Astrometrica. Since this was a newly discovered object with 2 days of observations, the orbit would have a significant degree of uncertainly and this discrepancy was to be expected.

Since the object was faint, I tried the “Stack and Track” feature in Astrometrica. Using the Slooh protocol “Faint Mono” normally produces 4 monochromatic or luminence files, though sometimes these are not all produced. I had 4 images from the first timepoint and 3 from the second, so I made 2 stacks from each set.

“Track and Stack” will read in a series of images and shift them according to the expected motion of the desired target. The motion can be entered, but if the object is known it can be looked up from the orbit database. So I selected the newly minted designation 2016 EL56 and the program shifted and stacked the images from the estimated motion rate and position angle or direction. Here is one of the stacked and shifted images:

20160315-01-2016EL56-stack

In the picture above, the images are shifted so the stars in the picture show up as a series of dots or a solid line. An object moving at the expected rate and direction will fall around the same position and show up as a single spot. So the weaker peaks in the individual images can add up to give a stronger signal over the background. The position will be a little less uncertain but the curve fit will work better so it can enhance the measurement overall. I’ve noticed that noise on a single image will also show up as a single spot so it’s important to look over the individual frames!

Running the observations in find_orb showed consistency with the other observations made to date and a positive influence on the overall fit. So I prepared a report and submitted it to the Minor Planet Center that day. Since I had a program code already assigned, this time the observations were published the very next day in the Daily Orbit Update MPEC 2016-E112 and later in the Minor Planet Supplement MPS 690473.

Minor planet 2016 EL56 is a Potentially Hazardous Asteroid (PHA) with an estimated size of 150 meters. The ESA site classifies it as an Apollo class asteroid ranging from around 4 AU down to about 0.3, with the next expected close approach in 2045 at 0.15 AU from Earth. It looks like the object was picked up after it passed by us in February, so it is now heading away and fading in brightness. It is not expected to have in impact in the future but any observations made while it is still accessible will help greatly in predicting it’s position and recovery when it returns!

 

(163243) 2002 FB3 – First Submission!

After getting my feet wet observing and measuring a few bright minor planets, I’ve been working on how to find and observe Near Earth Objects or NEOs. The resources and guidance I’ve been getting from the “A-Team” at Slooh.com have been invaluable in helping to identify and image NEOs, and to analyze and confirm results. And I even was able to get a set of observations accepted by the Minor Planet Center, and published just this week!

The first step is to identify objects that can be observed and are useful to report. One key resource is the European Space Agency’s Priority List. It classifies newly discovered and critical objects into priority categories for follow up observations. Many of these are recent discoveries of asteroids approaching Earth where it is vital to get accurate observation over as many days as possible in order to better determine their return time and potential risk. The list includes many small minor planets that can only be seen with very sensitive telescopes, but can be filtered by visual magnitude to highlight the current brighter targets.

The MPC also maintains lists of newly observed potential NEOs needing confirmation. It looks like these often originate from the large scale surveys and are confirmed by public and private observatories with high power gear. But there are usually a number of known minor planets needing follow up for various reasons and the more accessible ones can be found on the Bright Recovery Opportunity page. Note there is link near the top to customize the page allowing input of magnitude and position ranges. Again, filtering this list to mag 19 helps narrow this down to the lower hanging fruit. (Note that the magnitudes are approximate and can increase or decrease over time so its OK go a bit below what you can detect).

Back in early February, I noticed the minor planet (163243) 2002 FB3 on this recovery list. The body is numbered, so it has been observed for some time and should be well characterized. (The designation 2002 FB3 is the working identifier before it graduates with a permanent number). But the body had not been observed in a couple of years and turns out to be one worth checking up on from time to time. The object is fairly bright and was at a high southern declination, so I thought it would be worth a try from the Slooh observatory near Santiago, Chile.

The declination was actually very low, at over -70 degrees. From the Chile observatory W88 it would be found to the south at an elevation of 45-50 degrees. That is reasonably high up in the sky, but the Slooh observatory is on a mountain north of the city, so the view looking south over the town is subject to a fair amount of light pollution. But after solving the images in Astrometrica a moving object was visible right where expected:

20160313-01-2002FB3

Astrometrica has a feature that marks known objects according to the MPC orbit database currently loaded. The position can be approximate for newer objects with approximate orbits but it generally spot on for numbered objects. In the image above, there is moving object in the position expected for #163243 which should be our target. The identified object can be selected and the position determined from each of the images. Note the image above has a long streak which is fairly common in these pictures and are probably trails of meteors or artificial satellites.

The object was visible again on the following night, so it looked like I would have enough data for a submission to the Minor Planet Center!

After working up the observations for both nights and sharing with the “A-team” at Slooh, it was pointed out by the group’s mentor, Tony Evans, that the object I had picked up is on the MPC Critical NEO list and well worth reporting. It is a large enough asteroid to be classified as a Potentially Hazardous Asteroid (PHA), and at an estimated diameter of 1620 meters it would definitely be a bad day if it were to directly cross our path. The object has no predicted close encounters in the next 100 years, but is on the MPC Critical List as body worth checking on from time to time. Minor planet 163243 is also an Aten class asteroid. This class has an orbit that lies primarily between the Sun and the Earth. These have a relatively short orbital period (243 days in this case) and they are harder to observe since they are often located towards the Sun.

After checking my observations using a tool to calculate residuals and a few attempts at formatting everything properly, I got the green light to submit the data via email to the MPC. An acknowledgement was promptly received, so it looked like my report was accepted – the only thing left to do was to wait for publication!

If I were to establish my own observatory at home and wanted to submit results to the MPC, I would need to qualify for an observatory code by submitting observations of known objects for evaluation. The Slooh observatories have gone through this qualification and have received codes from the MPC – W88 for their Chile observatory for example. But in order for multiple people to observe from the same site, the MPC assigns a Program Code for each observatory user or team based upon their contact information, and one of these needed to be assigned to me before publication. This is a manual process and takes some time as the staff is quite busy. But after a few weeks the observations were published and I was assigned Program Code #7 at the the Chile site.

The MPC has daily updates known as MPECs or Minor Planet Electronic Circulars. These are released for new objects that have been found and confirmed with their temporary designations and current observations. There is usually a daily orbital update with recent observations all other objects. My results were included in MPEC 2016-E22 Daily Orbit Update on March 3 and look like so:

G3243        7C2016 02 04.06008 01 37 08.54 -71 51 22.2          16.3 VqEE022W88
G3243        7C2016 02 04.07019 01 37 22.37 -71 51 10.5          16.4 VqEE022W88
G3243        7C2016 02 05.10001 02 00 41.70 -71 27 30.0          16.4 VqEE022W88
G3243        7C2016 02 05.11556 02 01 02.27 -71 27 01.4          16.0 VqEE022W88

This gives the object and epoch in compressed format, the date, time, location and brightness of each time point. That’s it!

The thousands of observations received each week are consolidated into bi-monthly publications and supplements as the official record. But the results are also included in the database of observations maintained for each body and these can be retrieved when calculating orbits to confirm new observations or other scientific work. So every bit contributes to further orbit refinements and risk assessment.

Now that I have a program code for the Chile observatory, accepted observations should go through more quickly, so on to other targets!

 

 

C/2013 US10 Catalina

Comet Catalina C/2013 US10 is currently visible in the Northern Hemisphere using binoculars or a small telescope. After rounding the Sun late in November, it has been up in the pre-dawn sky, creeping up higher each night.

It was observable in early December in New England, but very low in the sky before sunrise. I tried to get a look at it a few times using binoculars but was not able to see it well between the trees at home! Had hoped to see it later in December, but skies have been very cloudy and foggy for the past few weeks as part of a very unusually mild and damp weather pattern.

Having some time off recently, I thought I would try to see the comet using one of the internet telescope services available, and was able to get some images of it after signing up for a trial on slooh.com

After logging in and watching some of the getting started videos, I was able to book a timeslot (or “mission” as they call it) to see the Catalina comet on one of their telescopes in the Canary Islands . The site has a page titled “What’s Up” that gives a lot of great suggestions for currently observable objects to look at including planets, deep sky objects and visible comets. You simply select an available time, select the desired object you’d like to see and you are all set!

But for comets and other moving objects you need to determine the coordinates the target will be at and create a “Coordinate Mission” for that location of the sky. I used Stellarium to determine where Comet Catalina would be from the observatory location at the time of the reservation. Since the reservation times are in UTC, it is also handy to set the TimeZone plugin in Stellarium to work in that time zone. That way, you can check the position at a given time in UTC and not have to convert to your local time. (Or I guess you can change your workstation to UTC time and keep it there)! The coordinates calculated in Stellarium can be a bit off, so to get accurate positions expected from the coordinates of the actual observatory it’s good to use the MPC Minor Plan and Comet Ephemeris Service or the JPL Horizons site.

After you enter the coordinates, you select the type of object you are observing, so I selected the “bright comet” option. Apparently this setting determines the exposure time and image processing used for the session. The site appears to confirm that the coordinates are observable at the time selected and will even warn you if a fainter object is too close to the moon to be seen.

Once you set this all up, that’s it! You can stay on and watch the images from the telescope as they are taken. Since my reservation was around 1 AM local time, I just went to sleep while my images were being acquired!

The next day, I signed back into the site, selected the My Images page and found 4 images taken of the comet. The session used both a high magnification telescope (17″ CDK af f7) and a wide field APO refractor telescope. Images were taken at the same time, processed and made available as color and mono PNG files in the size of the original CCD images. These can be viewed on the site, downloaded, or annotated and emailed or shared to your favorite social media site.

Here is the high magnification image of C/2013 US 10 Catalina from this session on 30 Dec 2015:

20160108-01-catalina-2015-12-30-hm

It’s hard to see in the above version, but there is a faint tail extending up and right – I believe this is the dust tail. The ion tail extends a short ways down from the comet center. (North is up in this image).

I noticed several fuzzy objects around the comet. Not more comets, but apparently Catalina US10 was passing through an area with a few galaxies.

Slooh also provides FITS files from the CCD cameras. These are downloaded from the observatory at the end of each night and made available through the Slooh website and as well as an email notification.

So I was able to take the FITS file of the unfiltered or luminance image and reduce in Astrometrica. Then I could take estimated coordinates of each of the galaxies visible in the picture and check them against positions in TheSky. In the image above there are 5 clearly visible. I marked these in Astrometrica and they are shown in the image below, along with the fit and estimated location of the comets:

20160108-C2013-US10-SloohT2HM17

The dual tails are more clearly visible in the inverted image. I could also try stacking the color and luminance FITS files to see if I could bring these out better in the positive image. But I kind of prefer the above as it reminds me of working with AgBr imaging!

I took an image of the comet on the next night, and recently tried combining the FITS files to make my own LRGB composite using MaximDL. I need to better understand how to bring out the tails in that package but got a fairly good result:

20160108-C2013US10-2015-12-31-comb

The dust trail to the upper right appears to have a fork in it at this time – taken on 31 December.

The Catalina comet will continue to be visible through January and then fade as it moves away from the sun. Turns out this comet will not be back to greet us but will continue on outside of the solar system for parts unknown. Apparently is was a deep solar object that had its orbit perturbed enough to be knocked into an ejection trajectory that will take it outside of the Solar System.

Next, I will try capturing some of the other comets in the sky using Slooh and perhaps another similar service.

 

 

 

Bogeys

After getting back into astronomy recently, one new development I’m really enjoying is the great abundance of astronomical events, exploration and research on social media. Following progress, discoveries and images from the New Horizons mission in near real-time on Twitter, for example, has been a thrill and quite addicting!

But there has always been a fringe element around this subject, and that comes up in SM as well.Last month I saw some fear mongering about a major comet or asteroid due to hit the Earth in September, and subsequent rebuttal and denial by professionals. I don’t even want to post a link to the sites purporting this nonsense – but you could look it up! But it’s got me thinking about whether a really big celestial object could catch us by surprise..

I’ve also re-joined a local astronomy group and am looking forward to getting out with them again. Many of the members have changed, but they still have a core group of very dedicated observers. One of the former members I knew was a dedicated comet hunter, and would go out on many clear nights with a wide-field telescope or binoculars and scan the sky for fuzzy objects.

To hunt for comets by eye, you have to become acquainted with existing nebula, galaxies and other fuzzy objects. In fact, Messier developed his catalog for this very reason! He had identified over 100 objects (and these have been added to), and today there are a number of more comprehensive catalogs for all of the “fixed” deep sky objects visible in the sky.

The club also co-hosted a talk by Thomas Bopp a while back, who, of course, is one of the co-discoverers of the spectacular Hale-Bopp comet. He described stargazing with friends and noticing a faint fuzzy object he did not recognize. After checking start charts for known objects he suspected he had found a comet. After watching it for a while, he noticed movement, confirming that it was not a nebula or galaxy. He did not have a way to take a picture, so he sketched the comet relative to nearby stars and was able to work out a location for the new comet. Then he sent in the discovery the old-fashioned way – by telegram!

Alan Hale is an avid observer and hunter of comets and had also noticed the new visitor and sent in his observations as well. The comet was confirmed to be new and was named for the two co-discoverers.

When Hale and Bopp first viewed the comet, it was determined to be about 9 AU out from the sun or well over 1 million km from Earth. The comet was one of the largest and brightest seen in recent times and would surely cause major damage if it happened to hit the Earth, but how likely is that?

After a newly discovered comet or minor planet is observed for a few days, it’s quite straight forward to calculate it’s orbital path. The motion of any body in orbit around the Sun was determined by Kepler and others in the 16-17th centuries and explained by Newton. Any body captured by the Sun will travel in an ellipse – or a perfectly round circle which is a specific type of ellipse. The orbit of the planets is roughly circular for the most part, but long period comets like Hale Bopp move in a very elongated or eccentric track. Hale-Bopp makes a trip around the Sun every 2500 years or so and when it comes to visit it approaches 0.93 AU before traveling way out to the fringes of the Solar System at 370 AU. It’s thought that it used to go further out before it’s orbit was brought in a bit closer by Jupiter.

Given the orbital parameters for a comet, one can work out the probability for impact developed by Opik over 50 years ago and refined by scientists in the field since. The probability is determined by whether the orbits cross and how often, and the chance that both objects will be in the same place at the same time. This gets fairly complicated as the orbit of a comet or other smaller body is subject to precession as well as perturbation by other bodies. So the orbits can align from time to time increasing the chance of a crossing. But since there is lots of room out there and the visits infrequent, the collision probability from a long-period comet is estimated to be in the tens or hundreds of millions per year per potential impact.

Perhaps people imagine the probability of these collisions to be more likely than this very small number because of the pictures we’ve all seen of the Solar System. These are fine conceptually but impossible to draw at actual scale. As this page from the NOAO shows, if the Earth were represented as a small peppercorn, or about 1/10 of an inch across, it would be located about 25m from the Sun. And Hale Bopp would travel about 10,000 m away on every orbit, coming back every 2500 year for another shot. Another awesome, live scale model was made recently by Wylie Overstreet and Alex Gorosh in the Nevada desert and posted here.

So I don’t see how a big comet could take us by surprise, but we’ll soon see! Anyhow I’m still waiting for Planet-X to end us, which was another doomsday hoax propagated on Usenet a while back. Perhaps things have not changed so much after all..