Fall is just around the corner here in the northern hemisphere, so it’s the time of year when we write observing proposals! And last week, we submitted the first Backyard Worlds: Planet 9 proposal of the season–to follow up some of our brown dwarf candidates using the Astrophysical Research Consortium (ARC) 3.5 meter telescope at Apache Point Observatory. We asked for half a night of time on Near-Infrared Camera & Fabry-Perot Spectrometer (NIC-FPS), to perform J band photometry of 10 objects. Photometry means you take a picture of the object and sometimes a picture of a reference star, and you use the image to figure out how bright your object is. J band corresponds to a wavelength of light of about 1.25 microns, about the size of a virus or a particle of soot.
Here’s why we we need these brightness measurements (the photometry). While many of our brown dwarfs have infrared photometry from surveys like 2MASS and Pan-STARRS, the reddest, coldest, and probably the most interesting objects are too faint for these surveys! 2MASS went as faint as about 16th magnitude in J band. Pan-STARRS data goes down to about 21st magnitude in y band (a wavelength of around 1.02 microns). But ultracool brown dwarfs are faint, faint, faint. So we need to make our own measurements.
Once we have the new photometry, we will be able to do two new things. First, we will be able to get much better estimates of the spectral types of these objects. As you may recall, the spectral type of the coldest brown dwarfs is Y. Only 25 Y dwarfs are presently known. T dwarfs are the next coldest, but hundreds of T dwarfs are have already been discovered, so Y dwarfs are much more exciting. So far, all we know about the targets we have in mind is that they have WISE colors that are similar to those of Y dwarfs (i.e. brighter in W2 than W1 by at least 2.5 magnitudes). But they might still turn out to be late T dwarfs. The near infrared photometry will help make that distinction.
Second, we will be able to apply for time on still larger telescopes to get their near-infrared spectra. The photometry will tell us what instrument we will need, and how long we need to keep the shutter open while were are collecting the spectra. These spectra will tell us for sure what the spectral type is (Y or T?), and maybe even lead to a big discovery.
Here’s a link to the full proposal, if you are curious: APO_BWs The final target list is not set yet, but the 10 targets that meet our cutoff of W1-W2 > 2.5 were found by Guillaume Colin, Sam Goodman and Dan Caselden. Nice work, guys!
I’m sure we’ll be writing several more telescope proposals over the next month—stay tuned!
Enjoy this guest post by one of our moderators, Michaela Allen, featuring a video by Guillaume Colin!
Hello newcomers to Backyard Worlds: Planet 9! Or maybe you are a returning citizen scientist to this project… whatever the case, welcome! My goal for this post is to give you a basic beginner’s guide to classifying objects on BW (Backyard Worlds: Planet 9). I am in NO way an expert, but I’d like to share what I have learned so far so that maybe you can learn something too!
A little about me first… My name is Michaela Allen, (@mallen33 on Zooniverse) and I am a current college undergrad student studying physics and astronomy. I’ve been helping classify objects on BW since the project launched, and I’ve learned so much since then! Going into this project I had no idea what it entailed—I was just excited at the prospect of potentially finding something that hadn’t been discovered before!
The first thing I want to share with everyone is a YouTube video made by fellow citizen scientist Guillaume Colin (@karmeliet on Zooniverse) all about his method of analyzing flipbooks on BW. This is a great video where he talks about the basics of BW, SIMBAD, and IRSA. He also goes through the steps of filling out the Think-You’ve-Got-One Form, which can be tricky to find all of the information needed for the form. Seriously, go check it out, and thanks to Guillaume for making this video!
Now, for the rest of this post, we going to look at some of my favorite subjects on BW. So let’s get started!
When you first go on BW, you get to go through a tutorial that shows you all kinds of examples of dipoles, movers, artifacts, etc. You also have a handy field guide on the right of the screen that shows examples of these as well. The tutorial and the field guide are great references to go back and look at– do not forget to use them! I still reference back to them all the time. While those are great examples to get started with, classifying your first subject can still be kind of overwhelming! I’d like to give y’all a few more examples of types of objects and subjects you may encounter while classifying.
In terms of fast movers, I haven’t come across any (yet!). The example in the field guide of Y Dwarf WISE 0855-0714 is what I still go off of. And remember, a true fast mover will appear in all four frames of a subject.
Other mover “imposters” to look out for is extra noise surrounding the area of declination of the South Atlantic Anomaly. This is in the -25 degrees region of declination, give or take a few arcminutes. This anomaly, which Marc talks more about in his Fast Movers post, tends to cause more noise in the subjects—and the noise can often look a lot like fast movers. For example, take a look at this subject.
There are a few orange dots visible throughout the frames that do look deceivingly like fast movers, but they are just noise. The area of declination and the often sporadic movement of these dots give away that these are not movers.
In terms of dipoles or slow movers, I have seen many! Some are definitely easier to spot than others. A dipole is an object that is moving but in a different way to all of the other objects in the subject. This subject is one of the first subjects I classified on BW, and it has a dipole! See if you can find it.
There it is at RA 151.99, dec 25.51 . I think this one is a great example of a lot of the dipoles I have seen. It isn’t super bright, but it’s not too faint either. It immediately stuck out to me, so I commented on the TALK page and asked for other opinions– don’t forget to comment on the talk pages too! If you’re ever unsure about anything, TALK about it (pun intended)! Sure enough, some people commented back, and I had found my first dipole!
Now, they aren’t all as easy to spot as this one. Faint dipoles take a little more effort. And remember, the fainter a dipole, the better of a chance it has of not being discovered! See if you can find the faint dipole in this subject.
This one is at RA 161.21, dec 13.79— to the right of that artifact. In terms of bigger and brighter dipoles, most of them I have seen have been in SIMBAD and are high proper motion stars. But just because it is bigger and brighter doesn’t mean it is going to be in SIMBAD! Always check to make sure!
Now sometimes you may find multiple objects of interest in a subject, which is great! You have to be careful of misalignment errors sometimes, though. These errors, caused by slight movements of the telescope, make the subjects seem like there are multiple dipoles. We talked about this subject, mentioned by another citizen scientist, @Chrismkemp, in one of the BW hangouts. She had seen seven or eight dipoles in this one subject and was wondering if that was even possible. I’ve come across subjects like these a few times, and they can be pretty tricky to classify. Do you see how the “dipoles” seem to kind of elongate? Marc calls them petals. Unfortunately, they can’t actually be classified as dipoles. If you ever have a subject that seems as if it has multiple dipoles, look for this “petal effect”. There was one real dipole in this subject, though. See if you can spot it!
That real dipole is at RA 349.77 dec -53.63 . This object one doesn’t seem to grow petals like all of the other imposter “dipoles” do in this subject.
The last thing I have to share with y’all is bad frames in some of the subjects. These can range anywhere from stripes across the frame, completely black frames, to half of the frame being cut off like in frame 3 of this subject. While these frames may sometimes look interesting, they do not need to be reported. If you ever come across them, you can always add the #badimage hashtag on the talk page.
Well, I hope that my limited experience has helped some of y’all on classifying objects at Backyard Worlds: Planet 9. Thanks to Marc for letting me share with everyone here! I’ve loved getting to participate in this project, and I’m excited to continue working on it!
Of course, this paper is already out-of-date. In the time it took to write the paper, you’ve discovered at least twelve more good brown dwarf candidates. And we used those discoveries to make an even better estimate of the sensitivity of our search than the one that appears in the paper. But let’s talk more about the paper and our first discovery, a source called WISEA 1101+5400 which we now know is a real brown dwarf, spectral type T5.5. Here is WISEA 1101+5400’s flipbook.
You may recall that shortly after launch, we were all excited about a faint dipole/mover, which Bob Fletcher had flagged on talk and Tamara Stajic reported on the Think-You’ve-Got-One form. That’s WISEA 1101+5400. A few weeks later, science team member Jackie Faherty nabbed a spectrum of it using NASA’s Infrared Telescope Facility. Here’s a nice plot of the spectrum, created by science team member Joe Filippazzo comparing the our object’s spectrum (black) to the spectrum of another T5.5 brown dwarf (red). It’s a great match! The extra wiggles in our spectrum are simply noise.
The quality of the match demonstrates that WISEA 1101+5400 is indeed a brown dwarf, and tells us that its temperature is in the range 900-1500 Kelvin (1200 – 2200 degrees Fahrenheit). We can tell the temperature range by looking at what molecules show up in the spectrum. The spectrum shows features associated with water, methane, iron hydride, potassium, and molecular hydrogen, labelled above. If the brown dwarf were hotter or cooler, the relative sizes of the dips in the spectrum from each molecule would be different.
Knowing the brown dwarf’s spectral type also teaches us roughly how bright it is, intrinsically. And since we know that the brightness of an astronomical object falls off as the inverse distance to it, squared, we can compare our images of WISEA 1101+5400 to those of other brown dwarfs to estimate its distance: roughly 34 parsecs or about 111 light years. For comparison, the closest known brown dwarf is the binary Luhman 16AB at 6.59 light years.
So what does this discovery mean for our understanding of brown dwarfs? Well, there are already a few hundred T dwarfs known–and this new one turns out to be somewhat run-of-the mill. It’s not super cool, and it’s not in a moving group, for example. Its infrared colors are close to the average colors for brown dwarfs with this spectral type. So we haven’t shattered any paradigms or broken any records with this object just yet.
But the discovery is a dramatic proof-of-concept. Just the fact that we found it, only six days after launch, shows that we’re on the right track toward lots more discoveries. Also, Zooniverse founder Chris Lintott tells me that our paper now holds the record for fastest publication from a Zooniverse project. How cool is that?
This is a moment to celebrate. Congratulations to us!! Let’s make some more discoveries and write some more papers together.
Hey everyone! It’s proposal season here at NASA. Every spring, NASA offers astronomers opportunities to apply for grant funding to do their research, and we’ve been busy taking advantage of that, writing proposals.
In the meantime, you’ve been hard at work, discovering stuff. We’re up to twelve brown dwarf candidates now plus one real verified brown dwarf. Holy smoke! We can estimate their spectral types based on their relative flux in the WISE 1 and WISE 2 bands (3.5 and 4.6 microns), and it looks like we have 7 new candidate L dwarfs and five new candidate T dwarfs. We’re going to try to get spectra for as many of these as we can.
In the meantime, did I mention we’ve been writing proposals? Well in a proposal, you try to make predictions about what you’re going to be able to learn or discover. You also try to show how your work compares to other work in the field. So we started by taking all thirteen objects and putting them on a plot, showing their proper motions and magnitudes in the WISE 2 (W2) band. Those are the red stars on the plot below, which was made by science team member Jonathan Gagne.
Then, as you can see, we plotted lots of other interesting stuff on here. For starters, we did our best to add all the brown dwarfs that were previously known. The little blue dots show every other brown dwarf in this database, which is every brown dwarf we could find in the literature. You can see right away that our discoveries, the red stars, fall towards the bottom of the cloud of blue dots made by the other discoveries. So our discoveries are fainter than average.
Next, we plotted some lines indicating the detection limits of some other recent surveys, by Adam Schneider et al and by Davy Kirkpatrick et al. (That’s Adam Schneider from our science team.) Those are the two biggest brown dwarfs searches made using WISE before we began ours. The survey done by Schneider et al. only detected brown dwarfs that fall above the orange dashed line. The survey done by Kirkpatrick et al only detected brown dwarfs that fall above the black dash-dot line. Those lines slant upward to the right because the WISE images they used were not divided into as fine time slices as ours, so some faster moving objects got blurred out.
Finally, we added some green lines showing what we think are the limits of Backyard Worlds: Planet 9. Now this part is harder since our survey, of course, isn’t complete yet. But we do know more or less what the shapes of the curves should be. We know that they slant up on the left side of the plot because that’s where the motion is too slow and the images of a moving object start self-subtracting. And we know that the objects we have already detected, the red stars, must lie above the lines. So we draw the curves and shift them around till they hug the bottom of the cluster of red stars—and that’s our best guess at our detection limits.
Note that there are two green lines. That’s because WISE spent more time making images at higher latitudes (here the symbol, beta, means latitude), so our survey is a bit more sensitive there. There’s only one brown dwarf candidate that’s up at a high latitude where this effect comes into play, though—it’s the one sitting on the lower green line.
So there we have it: a prediction for the sensitivity of our search. We will spot any brown dwarfs that fall above the green lines (pick the right one based on latitude). And we are the first to make an all-sky survey of the region above the green lines and below the orange and black lines. (A few brown dwarfs are already known in this region, but they came from surveys that only covered relatively small portions of the sky).
Now, remember that this plot uses logarithmic scales! Each of the big ticks on the x axis is a factor of 10. Each magnitude (the y axis) represents a factor of about 2.512. So that space on the plot could contain lots of brown dwarfs and other interesting objects, especially at high proper motions. Good luck!
Let’s talk about L dwarfs. The L spectral type contains object with temperatures in the range of about 1400-2200 Kelvin. It was first established in 1999 by Kirkpatrick et al.. They chose the letter “L” because it is next to “M” in the alphabet; M was the coolest spectral type in the literature at the time, and “N” was already taken to describe a class of evolved stars. Amazingly, L dwarfs are about twice as common as main sequence stars. They are just harder to spot because they are so much more faint and red.
The first L dwarf discovered was GD 165B, found by Becklin & Zuckerman in 1988. Curiously, 165B orbits another special kind of astronomical object: a white dwarf. Nowadays, about 1300 L dwarfs are known. So discovering one new one doesn’t usually merit a paper on its own. But when we collect a batch of 50 or so we will definitely want to announce them with a publication, especially if one or more turn out to be in moving groups of young stars. For example, here’s a recent paper by our own Adam Schneider announcing the discovery of 47 new L dwarfs, including seven that are in young moving groups. Membership in a moving group is important because it establishes the objects age.
A good clue that you might have an L dwarf is if it doesn’t appear in the DSS images, only in 2MASS and WISE. That’s because the DSS images were taken in visible wavelengths, and L dwarfs are too cool to shine in visible light, so they only show up in 2MASS and WISE bands, which are infrared. (T and Y dwarfs may not even show up in the 2MASS images). Just remember, the rule of thumb is that if it’s not in SIMBAD, we want to see it on the Think-You-ve-Got-One form. There are still interesting objects to find that are in DSS images.
Here’s one of the ones you found. It’s a great test for the eyes!
It’s a faint bluish dipole. Can you spot it in this flipbook? If not, scroll down to the answer key at the end of this article.
Here’s another one. Remember, each one of these is a real new discovery–not a recovery of an object that was known before!
Can you see it there? Here’s a third on to challenge yourself with.
OK here’s one more for you to test your skill on…
Ignore that giant blinking blue ghost in the middle! They are tough to spot. If you need help, here are the answers, below. Congratulations to @Andy_Arg, @karmeliet, @graham_d, @stevnbak, and @NibiruX for their exceptional eyesight And keep up the good work, everybody!!
You may have heard of the spectral sequence, OBAFGKM. What may be less well-known is that new brown dwarf spectral classes have been added in the past few decades. Now the full spectral sequence is OBAFGKMLTY, where the O stars are the most luminous, most massive, and hottest stars, while Y dwarfs are the lowest-mass, faintest, and coldest objects.
While the temperature drops through the MLTY spectral sequence, the chemistry occurring in the atmospheres of theses objects changes dramatically. This can be seen most clearly when looking at the spectra of these objects. The figure below shows what happens to the infrared spectra of objects spanning the MLTY spectral classes. On this figure, we have also marked the positions of the WISE filters (W1 and W2). Note that how bright each spectral type is in each filter changes. This is seen most dramatically in the Y dwarf, where almost no flux is emitted in the W1 filter and a relatively large amount of flux is emitted at W2. This is because large amounts of methane are present in the atmospheres of T and Y dwarfs, and methane absorbs light in the wavelength range covered by W1, and there are no absorbing sources at W2.
We can look at how this difference between W1 and W2 changes as a function of spectral type by finding their “color”. In astronomy, “color” refers to the difference in brightness of an object at different wavelengths. So when we look at the W1-W2 color of objects, large values mean that an object is much brighter at W2 than W1. The next figure shows how WISE colors vary with spectral type. The coldest objects, T and Y dwarfs, have very distinct WISE colors.
In fact, the WISE filters were built specifically to exploit this color difference in cold brown dwarfs. Thus, the WISE images of a very cold brown dwarf will show nothing in W1 and a bright point source in W2 (third figure). This is why some objects look orange in our WISE images. The mover example in the field guide is a good example of an orange-looking brown dwarf.
The WISE colors of Planet 9 have been estimated to be very different than the colors of brown dwarfs. This is why the point source in the Planet 9 simulation in the field guide looks blue.
It’s only 23 days since launch. And you’ve already discovered stuff!
We are still working on interpreting your classification clicks, and we probably will be for many months to come. But people have already submitted more than 1100 interesting subjects using the Think-You’ve-Got-One form, which is a bit easier for us on the science team to use right away. Among these objects, science team member Adam Schneider quickly spotted at least three interesting ones that we’ll want to include in an upcoming paper. Let me tell you about them.
This one has got the science team all abuzz.
It’s either a fast dipole or a slow mover. It mover about 1.25 pixels between the first and last epochs. And it’s faint. Faint is good! That means it’s less likely to already have been discovered.
It’s a little red (maybe pink) in color, meaning it’s significantly brighter in the WISE 2 band than in the WISE 1 band. In fact, if you look at how bright it is in the WISE 1 and WISE 2 bands, and the fact that it doesn’t appear in the 2MASS catalog at all, you would infer that it is likely to be a kind of brown dwarf called a “T dwarf”. If it is a T dwarf, it is about 30 parsecs (98 light years) away. PLEASE FIND MORE OF THESE!!
We are trying right now to find someone who is at the right telescope at the right time to take a spectrum of it, which would confirm that it really is a T dwarf. A colleague offered to observe it for us this week using NASA’s Infrared Telescope Facility. Alas, the weather was bad, and they didn’t even open the observatory dome. There are some opportunities coming up for us to get a spectrum from other telescopes in Hawaii. We will keep you posted.
Take a peek at this subject. At R.A. 11.8858634 degrees, declination -34.5458256 degrees (halfway up, near the left edge) is a blue-white dipole that appears to be a previously undiscovered M dwarf. This flipbook is a bit tricky, since if you only looked at frame 1, for example, you might think it were covered with dipoles! But when you play the animation, it becomes clear that most of those sources are ordinary artifacts. Thanks to @raychieng for submitting it.
Finally, check out this subject. Near the top, slightly left of center, at R.A. 217.8208564 degrees, declination 86.2991835 degrees (it’s almost at the north pole), is a moderately bright white dipole, which also appears to be a previously unreported M dwarf. A VizieR search turns up a high-proper motion source at those coordinates in the PPMXL catalog and the URAT1 catalog, but without a spectral type. However, the photometry (i.e. how bright the star is, in magnitudes) across the suggests that this star is probably an M dwarf. Thanks to @stevnbak for submitting it.
How can you tell the spectral type of an object from its photometry? How can you recognize if your dipole/mover is an earth shattering new Y dwarf, a dazzling new T dwarf, a cool new M dwarf, or just a boring old early-type star? Stay tuned–we’ll talk about that in the next blog post.
Great work, everybody! These discoveries are the proof of concept that we were hoping for. And I’m sure there will be more to come.
If you’ve found something interesting in a flipbook and you want to know more about it, SIMBAD is the right place to start. Just figure out the object’s coordinates using the numbers on the left and bottom of the images, type them in to SIMBAD’s coordinate query page. And poof, you’ll have all the answers! Right?
Well it’s not always that simple. So let’s talk for a bit about what SIMBAD can tell you–and what it can’t tell you–about your favorite patch of sky. I’m going to try to explain here, from start to finish, how to use SIMBAD to reliably determine if if you have rediscovered a well known object with high proper motion, or if you have possibly found a new high-proper motion object, worth submitting on the Think-You’ve -Got-One form.
First of all, SIMBAD is an acronym. It stands for Set of Identifications, Measurements, and Bibliography for Astronomical Data. SIMBAD began in 1972 as database of stars only (no galaxies, asteroids,planetary nebulae, clusters, novae, supernovae, etc.). But other objects have since been added in. SIMBAD now contains about 4.5 million stars and 3.5 million nonstellar objects.
Note that SIMBAD’s inventory is still heavily biased towards stars. Astronomers have cataloged far more galaxies than stars, for example, and a small fraction of these appear in SIMBAD. The NASA/IPAC Extragalactic Database (NED), for example, contains more than 214 million distinct sources. The VizieR database contains even more. But those extragalactic objects are not the high-proper-motion object we are seeking. And VizieR is much less user friendly than SIMBAD. So you’re better off sticking with SIMBAD to start.
When you do a SIMBAD search, start by typing in the coordindates of your object. No comma needed. SIMBAD offers you chance to select a coordinate system; go with the default, which is FK5. Leave the epoch and the equinox (i.e. for the coordinate system) both set to the year 2000. But where it says “define a radius”, change that number to 1 arc min. Objects further than one arcminute from your search location are probably too far away to be the object you are looking for.
After you hit return or click, “Submit Query,” SIMBAD will take you to one of three places: a page saying “No astronomical object found”,a table of objects it found, or a page that’s all about one specific object. Here’s what the “No astronomical object found” page looks like. If you end up here, be sure to flag your object with the #notinsimbad tag in TALK and submit your object using the Think-You’ve-Got-One form! If not, it’s still possible that your object is not in SIMBAD, and hence an interesting find. So read on!
If SIMBAD finds more than one object within the radius you chose, it will take you to a table listing all the objects, in order of how far away they are in angular separation from the coordinates you typed in. Here’s an example table.
The first place to look on the table is the column that says dist(asec). That’s because your fist task is to make sure the object SIMBAD is showing you corresponds to the object you care about! If the distance in this column is more than about 60 asec (arcseconds), i.e. one arcminute, from the coordinates you entered, it may be too far away on the sky to match the object you care about, unless you were sloppy when you looked up its coordinates. Note that the spacing between the tick marks on the left of the flipbooks is about 3 arcminutes (180 arcseconds). I bet you were much more accurate than that with your measurement.
Next, since Backyard Worlds: Planet 9 is all about finding objects with high proper motions, you’ll probably want to check the Otype column and the Proper motions column. The Otype column lists some codes that indicate what kind of object the object is, according to SIMBAD.
“PM*” means star with high proper motion. If you spot an object with this label, there’s a good chance you’re seeing it as a dipole or mover. But note that objects with high proper motion are also sometimes labeled “BD*”, “WD*”, “Fl*”, “LM*”, “SB*”, or even “*i*” or “Q?”! Here is a guide to all of SIMBAD’s object type codes, and here are a few more, defined.
Keep in mind that one star can sometimes have many known properties that would demand multiple classifications in SIMBAD’s system. For example, you could have a low mass star that is also a flare stare and is in a spectroscopic binary system with a white dwarf. That object should probably be labeled something like “LM*, Fl*,SB*, WD*”. But SIMBAD only gives it one of those labels. Bummer. So check that column for objects called “PM*”. But just because you don’t see “PM*” on the table you get, doesn’t mean SIMBAD hasn’t located the dipole or mover you’re looking at. It might just have given it a different Otype label.
As a next step, you’ll want to look at the column labeled “Proper Motion”. This column is really sort of two columns smushed into one; it lists a pair of numbers. The first number is its motion west to east due to its proper motion. The second number is its motion from south to north) due to its proper motion. That first number is motion in the direction of increasing Right Ascension, so it’s sometimes called the Right Ascension component. The second number is motion in the direction of increasing declination, so it’s sometimes called the declination component. Just note that there are some additional weird subtleties about actually figuring out how the Right Ascension of a star actually varies in time because of the nature of the equatorial coordinate system.
Proper motion, as you may recall, is how an object moves on the sky as a result of having a different orbit around the Galactic center than the Sun does. Objects near the Sun (Planet nine is an extreme example) can also shift around on the sky due to parallax, i.e. the effect of the Earth’s orbit. Parallactic motion alone would make a star move round and round in an ellipse. Proper motion goes in a straight line. Together, parallactic motion and proper motion combine to make stars move in a squiggly path like this (below). Experts in astrometry (the craft of measuring stellar positions) look at plots like this one and disentangle the two kinds of motion from it.
Now, what really matters to us is figuring out if the object might be a dipole or mover that we could spot. And that depends on a different number than what’s listed in SIMBAD: the total proper motion. To get the total proper motion, you need to add together the two proper motion numbers you read in SIMBAD in a kind of funny way: you square them both, sum the squares and take the square root. Anyway, if a object’s total proper motion is bigger than about 100 milliarcseconds per year, it will probably show up as a dipole. If it’s bigger than about 1000 milliarcseconds per year, it will probably show up as a mover. If you don’t see any objects with total proper motion greater than 100 milliarcseconds per year on this table, flag your object as #notinsimbad and submit your object on the Think-You’ve -Got-One form!
A third possibility is that SIMBAD will find only one single object within the search radius you entered. In that case, SIMBAD will jump right to a page on that specific object, like the one below for the star Vega (its proper motion and parallactic motion are shown above). You’ll notice that this page also lists the object’s proper motion, if it is known. I’ve circled it in red on the screen shot below. The units here are milliarcseconds per year again, which is what we want.
Let’s pretend your SIMBAD search pulled up this page. I’m super lazy so I’m just going to do it using Google as a calculator. Type sqrt(200.94^2 +286.23^2) into a Google search bar and you get 349.720597763. That’s clearly higher than 100 but less than 1000. So this star should show up as a dipole. Too bad. It’s already a well known high-proper-motion object. You can flag it with the #known tag on talk. But don’t submit it to the Think-You’ve-Got-One form.
Of course, sometimes, SIMBAD only finds one object, and it takes you directly that object’s page, and the object is clearly not the one you’re seeing in the flipbook! What if SIMBAD sends you directly to a page like the one below, for an active galaxy called M 81? There’s no proper motion listed because object outside the Milky Way don’t have proper motions.
If this happens, it means SIMBAD couldn’t find any high-proper-motion objects near the one you found. So go ahead and flag your object as #notinsimbad and submit your object on the Think-You’ve -Got-One form.
To summarize: SIMBAD can send you to one of three different pages. But–no matter where it sends you–if you can’t find an object on that page with TOTAL proper motion > 100 milliarcseconds per year, then you have an object worth flagging with #notinsimbad and submitting on the Think-You’ve-Got-One form.
One last comment. Good scientists take lots of notes. So I strongly encourage you to write notes in a subject’s TALK page about what you learned from SIMBAD. If you did find a high-proper-motion object in SIMBAD within a 1 arcsec search radius, type in some information about it, like its name, proper motion, otype, and distance to the coordiantes you used. That way people can check your work, and maybe they won’t need to repeat your search. We can also use your notes to develop a better understanding for our ability to recover known objects at Backyard Worlds: Planet 9. That’s an important way to measure the power of our search.
OK I think that’s enough for now. There’s lots more you can learn from SIMBAD of course. But maybe we’ll come back to that another day.
Since Mike Brown and Konstantin Batygin announced evidence for the existence of a distant ninth planet in the solar system, astronomers have been furiously analyzing and collecting data in hopes of being the first to spot it. A lot of the excitement is driven by the fact that planet nine may already have been detected in existing data sets. Astronomers love the idea of sifting through a huge pile of data to make that one epic discovery, and planet nine is the ultimate “needle in a haystack” adventure.
The standard approach to detecting a faint Trans-Neptunian Object (TNO) such as planet nine is to look for its reflected sunlight using the biggest ground-based visible light telescopes on Earth. There are several planet nine searches of this type currently underway. Mike Brown is using the Subaru 8 meter telescope on the Mauna Kea mountain top in Hawaii. Scott Sheppard is leading a dedicated TNO survey using the Dark Energy Camera (DECam) instrument on the Blanco 4 meter telescope at Cerro Tololo, in Chile. David Gerdes is also using archival DECam data to hunt for planet nine, and recently discovered “DeeDee” a possible dwarf planet over ninety times more distant from the Sun than the Earth. However, none of these surveys has yet or ever will cover the entire sky.
Since April 2016, I have been performing an automated planet nine search using WISE data, with help from my colleagues Benjamin Bromley, Peter Nugent, David Schlegel, Scott Kenyon, Edward Schlafly, and Kyle Dawson. WISE is a bit of an “X factor” when it comes to the search for planet nine, because using it to look for TNOs is very unconventional. WISE is comparatively a tiny telescope (0.4 meter diameter), and observes in the infrared from low-Earth orbit (as opposed to visible light from the ground). With WISE, we are searching for intrinsic emission from planet nine itself, rather than reflected sunlight. The big advantage of WISE is that it has already covered the entire sky more than six times. However, the main disadvantage is that there is an enormous uncertainty in how bright or faint planet nine might appear in the infrared. So planet nine might very well exist, even if it turns out that WISE can’t detect it.
My automated planet nine searches will likely have major problems in certain areas of the sky, particularly in the plane of our Milky Way galaxy, where there are huge numbers of background stars. This is where we really need Backyard Worlds: Planet 9. In the search for rare moving objects, professional astronomers often painstakingly blink through thousands or even millions of images by eye. Having a team of citizen scientists look through the WISE images will help make sure that no brown dwarf or ninth planet in this data set evades discovery.
Backyard Worlds: Planet 9 is my first time being involved in a citizen science project, and it’s been a lot of fun so far, even though I know we’re just getting started. Thanks for joining the search!
This post was updated on 1/20/19 to go with the reboot images.
There! In frame one: a red dot. And there it is in frame two, halfway across the image!
Fast movers. They are tantalizing. A nearby star or brown dwarf can only crawl so far in the four year time span of our data. The star that currently holds the record for the highest proper motion is Barnard’s Star, which plods along at a leisurely 10.36 arcseconds per year (3.8 pixels per year). If you see an object that moves more than about 0.01 degrees (16 pixels) between the first and last frames, it may be moving too fast to be a star or brown dwarf; you’d have to consider the possibility that it might be in our own solar system.
But are those flying red dots Planet Nine?? Well, it’s not that simple.
Let’s start by take a closer look at how planets move on the sky. Here’s a spectacular multi-exposure image of the planet Mars from Astronomy Picture of the Day. As you can see, Mars takes a complicated, looping path through the sky. So do all planets in the solar system. As you may know, that’s why they are called “planets”; the word stems from a Greek word meaning “wanderer”.
Planets in the solar system move in these loops because their motion on the sky is the sum of two components: the planet’s orbital motion around the Sun, and the motion of the Earth around the sun, which changes our point of view. The component of the planet’s motion that is caused by the Earth’s orbiting around the sun is called “parallactic” motion.
So what does this mean for us here at Backyard Worlds: Planet 9? We can’t see the planet’s whole looping path because we have only four exposures. But we still know a fair bit about what the motion will look like. It will be the sum of two components: the planet’s slow orbital motion and the relatively speedy parallactic motion. We know that the parallactic motion will be the faster, dominant component, simply because the Earth is much closer to the Sun than Planet Nine is, so it orbits faster. And we know what the Earth’s orbit is, so we know a lot about that dominant parallactic component of the motion.
Here is a simulation, from the field guide, of how Planet Nine might appear in a Backyard Worlds flipbook. First of all, notice that Planet Nine’s motion is more or less right to left (West-East) because it’s roughly in the plane of the solar system. If you see a fast mover moving vertically in the flipbook, be very suspicious. We can not really see asteroids or comets in our images. So a fast vertical mover is probably just noise.
Second of all, notice that there are two copies of planet nine! The second copy is created by the motion of the Earth around the sun: the “parallactic” motion. If the planet is closer than 700 AU, the parallactic motion will be bigger, and the two images will be farther apart. They might not even fit in one image. The size of the images we show is a compromise; if we made them too big they might be better suited for finding some nearby versions of Planet Nine, but then they would each take forever to scan. For that reason, we’ve provided links in the metadata (click the “i” button under the flipbook to see the metadata) that allow you to visit adjacent (pre-reboot) images to trace your favorite mover from one subframe to the next.
So what are those bright spots you’re seeing flying across that flipbook? Some of them are random noise, caused by the non-zero temperature of the detectors (you might call that “heat”). Some of them are probably caused by cosmic rays, those vagrant high energy protons and atomic nuclei that traipse in from beyond the solar system, sometimes bearing fascinating news of distant explosions, sometimes just being nuisances. If the images you are looking at are from a declination of roughly -25 degrees, the cosmic rays can be especially pesky. At this declination, a droopy bit of the Earth’s magnetic field called the South Atlantic Anomaly allows cosmic rays to get a little bit closer to the WISE satellite than we might prefer. Here are some examples of what cosmic ray hits do to WISE images. Cosmic ray hits are another reason why we need human eyes to examine these images.
Hey, nobody said finding Planet Nine would be easy. But, hey, in the reboot images, we’ve been able to made those cosmic rays much fainter, and Planet Nine easier to recognize. Thanks to @RonArzi for requesting this post, and thanks to you for reading it!