Tag Archives: astronomy

Found a new planet? Pics or it doesn’t exist.

In January, right at the beginning of the Spring semester, Professor of Planetary Astronomy Michael Brown and Assistant Professor of Planetary Astronomy Konstantin Batygin, both from the California Institute of Technology, published a remarkable prediction in the Astronomical Journal, Evidence for a Distant Giant Planet in the Solar System (read the article here, http://web.gps.caltech.edu/~kbatygin/Publications_files/ms_planet9.pdf) In the article, Dr. Batygin, the theoretician of the pair, uses Dr. Brown’s observations of objects within the Kuiper Belt to argue for the existence of an object in a Sedna-like orbit and approximately ten times the mass of Earth. The basis for their claim is the ordered clustering of the perihelions of the orbits of multiple Kuiper Belt objects, a phenomenon that has a 0.007% of occurring randomly (yes, the significance of the number was not lost on me). After a significant amount of modelling and numerical analysis, Dr. Batygin predicts the likely orbital parameters of the Neptune-sized object as being inclined as much as 40 degrees to the ecliptic and having a semi-major axis of ~700 AU with an eccentricity of ~0.6. Kuiper_oort This places its perihelion around 280 AU. That’s really far out there, and places the proposed object as a member of the distant Kuiper Belt or inner Oort Cloud, or Hills Cloud, rather than a member of the inner Kuiper Belt wherein resides more familiar objects like Pluto and Eris. The mathematics are extremely compelling and the discussion and conclusions well-reasoned, but as the modern saying goes, “Pics or it didn’t happen.”

This certainly isn’t the first time that an object has been predicted to exist by mathematical analysis of the orbit of other objects. The most famous, and earliest, is the prediction by French astronomer and mathematician Urbain Le Verrier of the existence of an eighth planet beyond the orbit of Uranus that would account for the Uranus’ increase and subsequent decrease in orbital speed unrelated to its solar distance. Le Verrier worked on the problem in the summer of 1846 during his position at the Paris Observatory. Using Newton’s mechanics and Law of Gravity and the observed positions of Uranus, he calculated where a more distant planet would have to be and how massive it would have to be to produce the observed deviations. After completing his work, two astronomers, Johann Gottfried Galle and Heinrich Louis d’Arrest at the Berlin University, began searching in the vicinity of Le Verrier’s predicted position for the new planet. Galle, looking through the telescope, called out positions and brightnesses of the visible objects to d’Arrest who compared the observations to previously recorded charts until Galle called out an object that was not on the chart. They had found the planet that would later come to be called Neptune within a single degree of Le Verrier’s calculations. It was a remarkable piece of work from both Le Verrier and from Galle and d’Arrest, and it was a triumph for Newtonian mechanics.

This method of discovering new objects was later attempted by William H. Pickering, Professor of Physics at Harvard University. Based on his calculations, using the apparent discrepancies in the orbits of both Uranus and Neptune, he attempted to image the proposed trans-Neptunian object at the Mount Wilson Observatory outside of Pasadena, CA. His search was unsuccessful, but the hunt for “Planet X” was picked up by Percival Lowell who had founded the Lowell Observatory in Flagstaff, AZ. Lowell’s attempts were equally unsuccessful. After Lowell’s passing, the search was tasked to an amateur astronomer from Burdett, KS, 23-year old Clyde Tombaugh. Rather than relying on sophisticated calculations, Tombaugh was tasked with systematically searching the Zodiac for anything non-stellar. In late January 1930, he captured two images of the object that we now know as Pluto. As it turns out the position of Pluto did not in any way correlate to Pickering’s calculations. In this case, the discrepancies were due to the lack of precision in the measurement of the masses of the outer planets.


Today, modern astronomers use the periodic motion of stars to mathematically infer the presence of extrasolar planets. The first of these discoveries was 51 Pegasi b. As two bodies orbit each other, such as a planet around its host star, the two bodies both move about their common center of mass. The planet being significantly less massive moves far more noticeably than the star, but the star does still move. Its motion is detectable by analysis of its light spectrum’s becoming alternately slightly bluer and then slightly redder as the star moves towards us and then away from us, respectively. This method has been used to locate many such extrasolar planets that we’re still unable to image directly. These are generally accepted as exceptions to the “Pics or it doesn’t exist” rule in science. The mathematics and analysis are so strongly compelling and there is no other viable alternate explanation that it is accepted that orbiting planetary bodies are responsible for the variations in the radial velocity of 51 Peg and other stars.

So now if we’re willing to take the mathematical word of the existence of extrasolar planets such as 51 Peg b, then why not for this new object proposed by Dr. Batygin and Dr. Brown from Cal Tech? The difference lies in the complexity of the problem. The extra solar planet problem is by comparison a simple problem. The radial velocity curve for 51 Peg is very clean, and the analysis of the data use methods that have long been vetted and refined by astronomers studying binary stars for which one can see the two separate objects. In other words, there is precedent for the methodology. This is not to say that Dr. Batygin’s methods are controversial or that the mathematical tools are not well understood. The Hamiltonian mechanics he deploys in his paper are extremely well understood and have been for over a century, but the data with which Dr. Batygin is working and the significant complexity created by moving from a two-body problem to an n-body problem make the analysis more difficult and intricate as well as making the results of those analyses less precise. For this reason, while I am very excited about this new prediction, I want to see an image before I take it as fact.

The observational discovery this new object, if it exists, likely won’t happen soon. Even at its proposed closest approach to the Sun, 280 AU, the intensity of sunlight striking the object is 0.00128% that of what it is here at Earth. Not only is the light very dim at that distance, most Kuiper Belt and inner Oort Cloud objects are coated with carbonaceous dust making their surfaces very dark and non-reflective. As our observational tools and techniques improve, we may eventually be able to start imaging these remote sentinels of our solar system, but until then, we’re left with only the predictions.

Comet PanSTARRS Is Tricky But Worth The Effort

There’s a comet in our skies this week! With Comet PanSTARRS being so close to the Sun and therefore so low to the horizon, seeing this first major comet of the year is tricky! The comet is viewable about a half hour to an hour after sunset, but don’t expect it to leap out at you. You’ll have to look hard for it. With the clear skies last night, I tried to see if I could spot the comet without aid, and it was tough. I couldn’t see it at all at first, not until the skies darkened considerably. I had to wait until a little before 8pm as Orion was starting to become visible before I could find the comet. Even then, I had to look very closely at the sky maps published at Sky & Telescope’s website to make sure I was looking in the right spot. Binoculars really helped. My 200-500mm zoom lens helped more! I finally did get an image of Comet PanSTARRS along side the Moon.

The image I captured was with my Nikon D7000 (a 1.5x crop sensor) with a focal length of 200mm (300mm 35mm equivalent) at f/5.6, a shutter speed of 2 seconds, and at ISO 800. I did some noise reduction in Photoshop, but didn’t do anything else to the image. I like how the night side of the Moon is visible when it’s just an ultra thin crescent like this.

Paul Tebbe and The Sun’s Analemma

When I first started teaching here at JCCC, I taught the General Physics I and II courses and the Physical Science course on occasion. In 1995, I was asked to fill in for a partial semester for Professor Paul Tebbe teaching Astronomy. Talking about astronomy, and especially astrophotography and photometry, with Paul was always a treat for me; his enthusiasm for astronomy was absolutely contagious! I especially enjoyed watching Paul talk to the public during the Evening With the Stars program and seeing his enthusiasm spread throughout his audience.  Paul’s wife, Dr. Anita Tebbe, found and sent to me a video of Paul talking about the analemma plank that’s part of the Galileo’s Garden sculpture back when it was still in the quad next to where the fountain is now.  Paul passed away in the Fall of 2000, but his passion for astronomy can still be seen and felt here at the JCCC campus and our observatory now bears his name in honor of all the hard work he’s done to build the Astronomy program.


The Joys of Country Living

People often ask me, “Doug, why do you live so far out in the country? Wouldn’t it be easier if you lived closer to campus?” Well, sure my commute would be a bit shorter, but then I’d never see night skies like this from my driveway.

Our Milky Way Galaxy extending up above my barn. This was taken on Friday, August 17th around 10pm-ish.

During late summer and early fall, if you look to the south in the evening, around 9-10ish, you’ll see the constellation Sagittarius, or more likely a subset of it the asterism of The Teapot. When you’re looking at The Teapot, you’re also looking toward the central core of our galaxy and the disc of our galaxy will extend almost straight upward from it. If you live in the city, this magnificent view will be denied to you by the copious amounts of light pollution from street lights and security lights. In order to get the view I get to see every clear night, you have to drive away from the reach of all those city lights. Getting to see the night sky like this is well worth the extra commute time for me!

This photo is a combination of 28 images each taken at a focal length of 18mm with an aperture f/5.6 and a shutter speed of 6 seconds at ISO 3200. I simply sat the camera on a tripod, locked down the shutter button, and walked away for a while. The images were combined using Deep Sky Stacker, a piece of freeware that automatically rotates and aligned a stack of individual images. It doesn’t take a fancy camera, just patience and good skies.

Imaging the Night Sky in Motion

So I’ve been meaning to try something new for a while now and I just got it worked out (sorta) this past week. I’ve always enjoyed photographing the night sky, but I really wanted to work on taking images that showed the sky in motion. It’s so easy to go outside, glance up at the sky, and think of it as static and unchanging, but if you look carefully enough, you’ll see that it’s in constant motion. I did a lot of work last year imaging the sky in a static way, either by shooting through a telescope with a clock drive, or by stacking a succession of individual images. While I really enjoyed some of the images that I captured through those methods, they didn’t really portray how rapidly things move around in our night sky.

In thinking of ways to demonstrate this motion, the first obvious choice was to do a typical “star trails” image. I’ve attempted these type of images before, but this past week, I tried to up my game a bit. My trails images before were only about 10 to 15 minutes in length, but the one I took last Thursday was approximately an hour-long exposure. The resulting image turned out pretty good, all things considered. I have a dusk-to-dawn light (that I need to put on a switch!) that’s great for security, but not so great for viewing the night sky. To combat its effects, I set my camera up on its tripod on the far side of my barn so that the barn blocked most of the light. The trees and surrounding ground, as you can see in the image, were still fully illuminated. My light and others around the area also light up the sky, so rather than a deep, dark background sky, I got a kinda pink-ish background. The star trails themselves, came out great.

Here’s the EXIF data for the image.

Camera Nikon D7000
Exposure 3099
Aperture f/5.0
Focal Length 18 mm
ISO Speed 200
Exposure Bias 0 EV

Even if you don’t have a tripod, you can still try this type of shot for yourself. You will need something to keep the camera steady. A beanbag or a bag of rice will work just fine. You will also need a remote shutter release. Find either a bright star or planet and manually focus on it, then set your camera to manual mode and set the shutter speed to “bulb”, and your aperture to your lens’ sweet spot. For the lens I was using, that happens to be about f/5.0. Even though it’s night, don’t use a high ISO. The length of the exposure will gather all the light you need. Once it’s ready, lock the shutter button down and go back inside where it’s warm and wait. 🙂

Practice, practice, practice, and share your star trails pics, tips, and suggestions in the comments section below.