mages from Moon Zoo showing trails from tumbling boulders in the Montes Alpes/Vallis Alpes region on the Moon. Credit: NASA/LRO/Moon Zoo.
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There’s probably a great story in this image, if only someone was there to witness it as it happened! This is an image from Moon Zoo, the citizen science project from the Zooniverse that asks people to look at images from the Lunar Reconnaissance Orbiter and search for craters, boulders and more. And often, the Zooites find some very interesting features on the Moon, like this one and the ones below that include tracks from rolling, bounding, tumbling and sometimes bouncing boulders. Then the task for the scientists is to figure out what actually happened to get these boulders moving — was it an impact, are the boulder on the bottom of a hill, or was it some other unknown catalyst? As Zooniverse founder Chris Lintott says, “The Moon has its own landscape that is really quite dramatic, so it’s a world well worth exploring.”
LRO image from Moon Zoo.
Why look for tumbling boulders? Moon Zoo scientist Dr. Katie Joy gave this explanation:
“One of the main reasons we are asking Moon Zoo users to search for scars left behind by tumbling boulders is to help support future lunar exploration initiatives. Boulders that have rolled down hillsides from crater walls, or massifs like the Apollo 17 landing site, provide samples of geologic units that may be high up a hillside and thus difficult to access otherwise by a rover or a manned crew vehicle. If mission planning can include traverses to boulders that have rolled down hills, and we can track these boulders back up to the part of hillside from where they have originated, it provides a neat sampling strategy to accessing more geological units than would have been possible otherwise… Thus we hope to use Moon Zoo user data to produce a map of known boulder tracks (and terminal boulders) across the Moon.”
If you want to join in on the fun of looking for mysteries on the Moon, check out Moon Zoo, or the Zooniverse for more citizen science projects where you can get involved in helping scientists do real science.
Screenshot of Einstein@Home. Image courtesty of B. Knispel of Albert Einstein Institute
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Hooray for citizen scientists! The Einstein@Home project has discovered a unusual pulsar approximately 17,000 light-years away in the constellation Vulpecula. The project works by people “donating” idle time on their home computers. This is the first deep-space discovery by Einstein@Home, and the finding is credited to Chris and Helen Colvin, from Ames, Iowa in the US, and Daniel Gebhardt of Universitat Mainz, Musikinformatik,Germany.
The newly discovered pulsar, PSR J2007+2722, is an isolated neutron star that rotates 41 times per second and has an unusually low magnetic field.
Jim Cordes, Cornell professor of astronomy, said the object is particularly interesting because it is likely a recycled pulsar: a neutron star that once had a companion star from which it acquired mass; but whose companion exploded, kicking it free.
Unlike most pulsars that spin as quickly and steadily, PSR J2007+2722 sits alone in space, and has no orbiting companion star. However, the scientists say they can not rule out that it may be a young pulsar born with an lower-than-usual magnetic field.
“We think there should be more of these disrupted binary pulsars, but there haven’t been that many found,” said Cordes. “No matter what else we find out about it, this pulsar is bound to be extremely interesting for understanding the basic physics of neutron stars and how they form.”
The discovery demonstrates the power of the network used to collect and sort through vast amounts of data, Cordes said.
Einstein@Home was originally organized to find gravitational waves — ripples in space-time — using the Laser Interferometer Gravitational Wave Observatory (LIGO). In 2009, data from the Arecibo Observatory were included in the processing.
Chris and Helen Colvin who were credited with discovering a new pulsar. Image courtesy Chris Colvin.
Einstein@Home is based at the Center for Gravitation and Cosmology at the University of Wisconsin-Milwaukee and at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute, or AEI) in
Hannover, Germany. About one-third of Einstein@Home’s computing capacity is used to search Arecibo data.
Einstein@Home volunteer Daniel Gebhardt from Germany. Image couresty of Gebhardt.
“This is a thrilling moment for Einstein@Home and our volunteers. It proves that public participation can discover new things in our universe,” said Bruce Allen, leader of the Einstein@Home project, AEI director and adjunct professor of physics at the University of Wisconsin-Milwaukee. “I hope it inspires more people to join us to help find other secrets hidden in the data.”
Gebhardt and the Colvins will receive plaques noting their discovery, and all plan to stay involved.
The Hubble Space Telescope is 20 years old on Saturday and, to mark this anniversary, all the world’s space and astronomy fans have a chance to become part of the Hubble team.
As part of the birthday celebrations NASA’s Space Telescope Science Institute and the online astronomy project Galaxy Zoo are making some 200,000 Hubble images of galaxies available to the public at Galaxy Zoo (www.galaxyzoo.org). They hope that volunteers looking for their own favorite galaxies will join forces to give the venerable telescope a present – classifications of each galaxy which will help astronomers understand how the Universe we see around us formed.
“The large surveys that Hubble has completed allow us to trace the Universe’s evolution better than ever before,” said University of Nottingham astronomer and Galaxy Zoo team member Dr. Steven Bamford. “The vast majority of these galaxies will never have been viewed by anyone, and yet we need human intuition to make the most of what they are telling us”.
More than 250,000 people have already contributed to Galaxy Zoo since its launch in 2007, but so far they have been looking only at the ‘local’ Universe, up to a hundred million or so light-years away. The galaxies in HubbleZoo are from some of the big surveys, such as GOODS, and the images were processed by the Galaxy Zoo team alongside Roger Griffith at JPL and the Space Telescope Science Institute (see this article, from my Universe Today series on the Hubble, for more details on GOODS).
“Hubble will enable us to look back in time, to the era when many of the galaxies we see today were forming,” said Dr. Chris Lintott of Oxford University, Galaxy Zoo principal investigator. “As a kid I always wanted a time machine for my birthday, but this is the next best thing!”
“We never dreamt that people would find so many fascinating objects in the original Galaxy Zoo,” said Yale University astronomer Dr. Kevin Schawinski. “Who knows what’s hiding in the Hubble images?” Lintott added: “As we recovered from the launch of the original Galaxy Zoo, we knew we’d want to have a look at Hubble. Now we realize the images are better and the galaxies weirder than we ever thought they would be.”
And how will you, dear zooite-to-be, contribute, and find a hidden gem among the Hubble galaxies? Once you log in, you will asked to answer simple questions about what you are seeing, for example, identifying the number of spiral arms visible, or spotting galaxies in the process of merging. And if you spot something odd, you can bring it to the attention of other zooites, and the Zoo astronomers. Arp147 (Credit: NASA, ESA, and M. Livio (STScI))
“Every galaxy is special in its own way,” said Stuart Lynn of Oxford University, Galaxy Zoo team member, “but some are worthy of individual attention. Anyone combing through the data using our site could make a spectacular discovery, and that would be the best birthday present of all.”
Galaxy SDSS J100213.52+020645.9 (SDSS) Galaxy SDSS J100213.52+020645.9 (Hubble)
Sources: NASA, HubbleSite, Oxford University, Galaxy Zoo Forum The two images above, of a galaxy called SDSS J100213.52+020645.9, highlight the sharpness and depth of the Hubble’s images (the SDSS telescope and the Hubble have primary mirrors of approximately the same diameter).
Mitch's Star; full caption below (Credit: Keel/PSS/SARA)
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“The most exciting phrase to hear in science, the one that heralds new discoveries, is not Eureka! (I found it!) but rather, ‘hmm… that’s funny…'” (Isaac Asimov)
A few short years ago, Zooite Hanny van Arkel discovered Hanny’s Voorwerp in an SDSS image of a galaxy (“What’s the blue stuff below? Anyone?”), and a new term entered astronomers’ lexicon (“voorwerpje”).
Very late last year, Zooite mitch too had a ‘that’s funny…’ moment, over a spectrum (yes, you read that right, a spectrum!).
Now neither Hanny nor mitch have PhDs in astronomy … Mitch's Mystery Star (SDSS, Galaxy Zoo)
But I digress; what, exactly, did mitch discover? Judge for yourself; here’s the spectrum of the star in question (it goes by the instantly recognizable name 587739406764540066): Spectrum of Mitch's Mysterious Star (SDSS)
“I asked a couple of white-dwarf aficionados, and neither recalls seeing any star with these features (nor does Jim Kaler, who wrote the book on stellar spectra),” Bill Keel, a Zooite Astronomer known as NGC3314 wrote, kicking off a flurry of forum posts, and a most interesting discussion!
“Can we rule out something along the line of sight, possibly a cold molecular cloud?” EigenState wrote; “If both stars are moving SE (towards the bottom left corner), could Mitch’s star (square) be affected by debris in the trail of the bright red star (triangle)? I am thinking of the trail left by Mira. So the spectrum would be white dwarf shining through cooled red star debris?” said Budgieye. NGC3314 continued “It can’t be like our current Oort Cloud since we don’t see local absorption from our own in front of lots of stars near the ecliptic plane. To show up this strongly, it would then have to be either much denser or physical much smaller. This just in – this may be the most extreme known example of a DZ white dwarf, which have surface metals. White dwarfs aren’t supposed to, because their intense surface gravity will generally sort atmospheric atoms by density, so this has been suggested (with some theoretical backing) to result from accretion either from circumstellar or interstellar material (so it could be at the star’s surface but representing material formerly in a surrounding disk). Watch this space…”
Then, two weeks after mitch’s discovery, Patrick Dufour, of the Université de Montréal, joined in “Hi everyone, I have known this objects for many years. I have done fits almost 5 years ago but just never took time to publish it. Will do it in the next few weeks. Meanwhile, enjoy this preliminary analysis… The abundances are very similar to G165-7, the magnetic DZ, but it’s a bit cooler (explaining the strength of the features).” Patrick, as you might have guessed from this, is an astronomer with specific expertise in white dwarfs; in fact the abstract to his PhD thesis begins with these words “The goal of this thesis is to accurately determine the atmospheric parameters of a large sample of cool helium-rich white dwarfs in order to improve our understanding of the spectral evolution of these objects. Specifically, we study stars showing traces of carbon (DQ spectral type) and metals (DZ spectral type) in their optical spectrum.”
Somehow yet another astronomer, Fergal Mullally heard about mitch’s mystery star and joined in too “Many other WDs with strong metal absorption lines are surrounded by a cloud of accretable material. This makes sense because the metals quickly sink below the surface (as mentioned by NGC3314). In some cases, metals are only visible for a few weeks before they are sink too deep to be seen. The disks are exciting, not only because they can be so young, but their composition suggests we might be looking at the remains of an asteroid belt (see http://arxiv.org/abs/0708.0198).” To which Patrick added “Mitch’s Mystery Star is a cool (~4000-5000 K) helium rich white dwarf with traces of metals (abundances similar to G165-7). The metals most probably originate from a tidally disrupted asteroid or minor planet that formed a disk around the star.”
So, mitch’s mystery star is just a rather weird kind of DZ star, and DZs are just unusual white dwarfs?
Yes … and no. “The asymmetrical line near 5000 is almost certainly MgH. As for the one at 6100, I am open to suggestion. I have never seen it anywhere else. For G165-7, the splitting is Zeeman. But the broadening is van der Waals by neutral helium. No splitting is observed in this star (and I took a really good spectra at MMT a few years ago to be sure).” Patrick again; so what is the mysterious asymmetrical line at 6100 Å?
Two more weeks passed, and a possible reason for Fergal’s interest emerges, in a post by NGC3314 “While we wait to see how Patrick’s new calculation shakes out, here’s an interesting new manuscript he was involved with, that points to likewise interesting things about the DZ stars. [] Wow. White-dwarf spectra as tombstones for planetary systems… wonder how the system stayed close enough to end up on the white-dwarf atmosphere all through the red-giant phases? The binary systems we can see look awfully far apart to have had helpful dynamical effects for this.” (in case you didn’t read up on Fergal, he’s very keen on exoplanets and ET). Curiouser and curiouser
Then, in February, a tweet: “At campus observatory, seeing whether we can measure orbital motion between Mitch’s star and its K-dwarf companion.” The tale is becoming curiouser and curiouser (exoplanets in binary star systems? If life had evolved on a planet in orbit around the star which later went red giant then white dwarf, could it have somehow survived and landed on a planet in orbit around the K-dwarf companion?)
I’ll let NGC3314 have the final word: “This furnishes one more example of how the wide interest in Galaxy Zoo allows things once unthinkable – during the SDSS, the whole analysis plan never conceived that every bright galaxy in the survey, and every one of the million or so spectra would actually be examined by a human being.”
Oh, and the Asimov quote seems to be an urban myth (if any reader knows when, and where, Asimov actually said, or wrote, those words …).
Source: Galaxy Zoo Forum thread Mitch’s Mystery Star
Full caption for image at the top of this article (Credit: Bill Keel): I had a look with the SARA 1m telescope in BVR filters last week, to check for obvious variability. Pending more exact measurements, it’s about as bright as it was in the SDSS images and the older Palomar plates. As SIMBAD shows, this is known as a star of fairly high proper motion (and that’s about all). You can see this when I register the original red-light Palomar photograph to the image from last week, a time span of almost 59 years. The attached picture compares red-light data from the original Palomar Schmidt sky survey in early 1951, the second-epoch Palomar survey around 1990, and SARA on Jan. 7, 2010. You can also see that the bright red star to the southeast has almost exactly the same (large) proper motion.
It goes by the super-catchy (not!) title “A Catalog of MIPSGAL Disk and Ring Sources”. I chose it, over 213 competitors, because it’s pure astronomy, and because it’s something you don’t need a PhD to be able to do, or even a BSc.
Oh, and also because Don Mizuno and co-authors may have found two, quite local, spiral galaxies that no one has ever seen before!
Some quick background: arXiv has been going for several years now, and provides preprints, on the web, of papers “in the fields of physics, mathematics, non-linear science, computer science, quantitative biology and statistics”. It’s owned, operated and funded by Cornell University. astro-ph is the collection of preprints classified as astro physics; the “recent” category in astro-ph is the new preprints submitted in the last week.
When I have any, one of my favorite spare-time activities is browsing astro-ph (Hey, I did say, in my profile, that I am hooked on astronomy!)
Briefly, what Mizuno and his co-authors did was get hold of some of the images from Spitzer (something that anyone can do, provided their internet connection has enough bandwidth), and eyeball them, looking for things which look like disks and rings. Having found over 400 of them, they did what the human brain does superbly well: they grouped them by similarity of appearance, and gave the groups names. They then checked out other images – from different parts of Spitzer’s archive, and from IRAS – and checked to see how many had already been cataloged.
And what did they find? Well, first, that most of the objects they found had not been cataloged before, and certainly not given definite classifications! Many, perhaps most, of the new objects are planetary nebulae, and their findings may help address a long-standing puzzle in this part of astronomy. MGE314.2378+00.9793 (Mizuno et al./Spitzer)MGE351.2381-00.0145 (Mizuno et al./Spitzer)
But they also may have found two local spiral galaxies, which had not been noticed before because they are obscured by the gas-and-dust clouds in the Milky Way plane. How cool is that!
Here’s the ‘credits’ section of the preprint: “This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA in part through an award issued by JPL/Caltech. This research made use of the SIMBAD database and the Vizier catalog access tool, operated by the Centre de Donnees Astronomique de Strasbourg. This research has also made use of NASA’s Astrophysics Data System Bibliographic Services.”
And here’s the preprint itself: arXiv:1002.4221 A Catalog of MIPSGAL Disk and Ring Sources; D.R. Mizuno(1), K. E. Kraemer(2), N. Flagey(3), N. Billot(4), S. Shenoy(5), R. Paladini(3), E. Ryan(6), A. Noriega-Crespo(3), S. J. Carey(3). ((1) Institute for Scientific Research, (2) Air Force Research Laboratory, (3) Spitzer Science Center, (4) NASA Herschel Science Center, (5) Ames Research Center, (6) University of Minnesota)
PS, going over the Astronomy Cast episode How to be Taken Seriously by Scientists is what motivated me to pick this preprint (however, I must tell you, in all honesty, that there are at least ten other preprints that are equally pickable).
A coronal mass ejection. Credit: Solar Storm Watch
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Sun-worshiper alert! Now you can have the chance to help scientists spot and track solar storms and be involved in the latest solar research. The ‘hottest’ new Citizen Science project from the “Zooniverse” is Solar Storm Watch. Volunteers can spot storms and track their progress as they hurtle across space towards our planet. Your “clicks” and input will help solar scientists better understand these potentially dangerous storms and help to forecast their arrival time at Earth. “The more people looking at our data, the more discoveries we will make,” said Dr. Chris Davis, Project Scientist with the STEREO mission. “We encourage everyone to track these spectacular storms through space. These storms are a potential radiation hazard for spacecraft and astronauts alike and together we hope to provide advanced warning of their arrival at Earth.”
Solar Storm Watch has been in Beta testing for about two months, but is now officially open for business. “It’s been wonderful to watch the team get ready for a flood of data,” said Chris Lintott, one of the founders of the original Galaxy Zoo, and now Zooniverse — new citizen science projects that that use the Galaxy Zoo model — of which Solar Storm Watch is a part. ” I’m sure there are discoveries there already.”
“I’ve been sitting at my desk watching the results roll in and there are plenty of CMEs that just need a few more clicks,” said Arfon Smith from Oxford University, one of the developers of Zooniverse, who has helped solar astronomers at the Royal Observatory in Greenwich integrate their science projects into the Galaxy Zoo model.
STEREO spacecraft. Credit: NASA
The project uses real data from NASA’s STEREO spacecraft, a pair of satellites in orbit around the Sun which give scientists a constant eye on the ever-changing solar surface. STEREO’s two wide-field instruments, the Heliospheric Imagers provide Solar Stormwatch with its data. Each imager has two cameras helping STEREO stare across the 150 million kilometers from the Earth to the Sun.
“The Solar Stormwatch website has a game-like feel without losing any of the science,” said Julia Wilkinson, Solar Stormwatch volunteer. “I can click away identifying features and watch solar storms head towards Earth on the video clips and learn about solar science at the same time. It’s fun, it’s addictive, it’s educational and you get to contribute to real astronomy research without being an expert in astrophysics … The fact that any Solar Stormwatch volunteer could make a brand new discovery about our neighboring star is very cool indeed. All you need is a computer and an interest in finding out more about what the sun is really like. Solar astronomy has never been easier!”
Solar Storm Watch has made their project very interactive with social media, as you can share your discoveries on the user forum and Flickr, as well as follow the space weather forecast on Twitter. SSW also has a blog to shre the latest news and challenges.
Now that the Moon is absent from the early evening picture, are you ready to journey around a black hole? It’s not an easy observation, but it is one that doesn’t require highly specialized equipment and its not difficult to find. Can you identify Capella? Then let’s rock…
Using the map below to help you identify the constellation of Auriga, you won’t have any problem picking out the sixth brightest star in the northern hemisphere night – bright, yellowish-white Capella. While Alpa Aurigae is an interested spectroscopic binary star, it’s not our target. If your skies are fairly dark, look a few fingerwidths southwest for much dimmer Epsilon (the backward 3 on our map). Epsilon Aurigae is an eclipsing binary star, but one that has an extraordinarily long period -27.1 years. While it only drops .8 of a magnitude, it’s dark companion is a 10-12 solar mass black hole. According to studies done by Wilson and Cameron a ring of obscuring material surrounds the black hole and accounts for the magnitude drop. And it’s dropping now!
According to AAVSO Special Notice #192 prepared by Aaron Price: “Epsilon Aurigae continues to progress through its first eclipse since 1982-84. Visual and photometric observation means place it at around magnitude 3.7-3.8. Totality was likely reached sometime in January, but it will take some time to analyze the data to establish a specific date. Totality is expected to last about 15 months, but the system is not expected to remain quiet during this time. Small amplitude modulations are being detected which are likely not associated with the eclipse itself. However, their exact source is still debated. The amplitude of these modulations are at the limit of the average observer’s ability to detect visually. Therefore this may make a nice, challenging system to test your eyes. Right now, Epsilon Aurigae is well placed for observing high in the sky right after dusk.
In addition to these modulations, a mid-eclipse brightening of a few tenths of a magnitude have been reported in past eclipses. If confirmed, it would contribute significantly to our understanding of the structure of the eclipsing disk of material. The problem is this will happen next summer when epsilon Aurigae is near solar conjunction. So observations very early in the morning later this season will be very important. It may be a good idea to begin practicing twilight observations right now.”
What will it look like? Just a barely perceptible change in brightness, but observers interested in DSLR or photoelectric photometers may want to use this project as an entry point. A team of observers is working on a series of tutorials on the Citizen Sky web site. General information regarding the Epsilon Aurigae campaign and a series of online discussion forums can be found at the Citizen Sky web site. Information is also available to submit your observations to the American Association of Variable Star Observers (AAVSO), too!
Journey around a black hole… If you dare!
Epsilon Aurigae illustration is courtesy of Nico Camargo.
Doug Ellison from UnmannedSpaceflight.com has done it again… and again… and again. Here are new Mars flyover videos Doug has created from data from the HiRISE camera on the Mars Reconnaissance Orbiter. Using DEM (Digital Elevation Model)– (also known as DTM Digital Terrain Model) files provided by the HiRISE team, Doug is able to render 3-D movies of a specific location on Mars. Since he is using actual high-resolution data from HiRISE, Doug says the terrain seen in the movies has accurate vertical scaling and is not exaggerated. These new views of the Red Planet are also stunningly beautiful! The video above is of the Mojave Crater wall on Mars, and below is Athabasca Valles. And Doug says more are on the way! If you recall, Doug created the flyover video of the Spirit rover’s location that was on Astronomy Picture of the Day. Continue reading “New Amazing Mars Flyover Videos”
Possible future landing site on Mars. Credit: NASA/JPL/University of Arizona
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The HiRISE science team is now taking requests! A new web tool called HiWish is now available for the high-resolution camera on the Mars Reconnaissance Orbiter which allows the public to suggest a location on Mars where the HiRISE instrument should take an image. If you don’t have a particular location, you can use the HiWish site to browse around the planet, examine the locations of other data sets, and find a place that should be imaged. The team will then put into their targeting database, and your suggestion may get selected as an upcoming observation. Furthermore, the HiWish site allows you to track your suggestions and be notified when one of your suggestions gets taken.
Maybe you could even find a really unusual feature on Mars, such as this race-track-like feature that may one day be a landing site for a future mission to the Red Planet. HiRISE images will help determine if this spot is sufficiently safe for landing, such as not too many boulders, steep slopes, or too many high speed MASCAR races — (that’s the Mars Association for Super Cool Aerodynamical Racing). If it is safe, it may be considered for the 2011 Mars Science Laboratory or the 2018 rovers that ESA and NASA are working on for a join mission.
The above image is actually a huge shield volcano in the northeast part of Syrtis Major, and near the Northwest rim of Isidis Planitia, a giant impact basin.
So, go create an account at HiWish and get wishing!
In a new paper recently uploaded to arXiv, Kevin Krisciunas from Texas A&M describes a method for determining the orbital eccentricity of the moon with a surprisingly low error using nothing more than a meter stick, a piece of cardboard and a program meant for fitting curves to variable stars.
This method makes use of the fact that the eccentricity can be determined from the ratio of the mean angular size of an object and one half of its amplitude. Thus, the main objective is to measure these two quantities.
Kevin’s strategy for doing this is to make use of a cardboard sighting hole which can slide along a meter stick. By peering through the hole at the moon, and sliding the card back and forth until the angular size of the hole just overlaps the moon. From there, the diameter of the hole divided by the distance down the meter stick gives the angular size thanks to the small angle formula (? = d/D in radians if D >> d).
To prevent systematic errors in misjudging as the card is slid forward until the size of the hole matches the moon, it is best to also approach it from the other direction; Coming from in from the far end of the meter stick. This should help reduce errors and in Kevin’s attempt, he found that he had a typical spread of ± 4 mm when doing so.
At this point, there is still another systematic error that must be taken into account: The pupil has a finite size comparable to the sighting hole. This will cause the actual angular size to be underestimated. As such, a correction factor is necessary.
To derive this correction factor, Kevin placed a 91 mm disk at a distance of 10 meters (this should produce a disk with the same angular size as the moon when viewed from that distance). To produce the best match, the slip of cardboard with the sighting hole should need to be placed at 681.3 mm on the meter stick, but due to the systematic error of the pupil, Kevin found it needed to be placed at 821 mm. The ratio of the observed placement to the proper placement provided the correction factor Kevin used (1.205). This would need to be calibrated for each individual person and would also depend on the amount of light during the time of observation since this also affects the diameter of the pupil. However, adopting a single correction factor produces satisfactory results.
This allows for properly taken data which can then be used to determine the necessary quantities (the mean angular size and 1/2 the amplitude). To determine these, Kevin used a program known as PERDET which is designed for fitting sinusoid curves to oscillations in variable stars. Any program that could fit such curves to data points using a ?2 fit or a Fourier analysis would be suitable to this end.
From such programs once the mean angular size and half amplitude are determined, their ratio provides the eccentricity. For Kevin’s experiment, he found a value of 0.039 ± 0.006. Additionally, the period he determined from perigee to perigee was 27.24 ± 0.29 days which is in excellent agreement with the accepted value of 27.55 days.
