Astronotes-Mar-2009

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March, 2009 Astronotes

Vol. 48, No. 2 ISSN 0048-8682 March 2009
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Map Diagram of the recent satellite collision
by Michael Earl


Ottawa Centre Meeting Report - February 6, 2009

Recorder's Notes by Estelle Rother

Meeting chair Attilla Danko opened the February meeting. Mike Moghadan began with an update on Outreach for IYA (International Year of Astronomy). The Tafelmusik astronomy concert would take place on Friday March 6. There would also be an indoor display. This event will be followed by 100 Hours of Astronomy, to be held between April 2 and April 5. International Astronomy Day, an annual event at the museum, will be held on May 2. The Galileo lecture will follow in June. And July 20 is the 40th anniversary of the Apollo 11 landing on the moon. Public star parties are planned throughout 2009. Mike would also like to include solar observing in his outreach program.

Mike then discussed ways to get involved in public outreach and the IYA. He suggested joining the Yahoo outreach discussion group or the speaker's bureau. Get involved with developing the 100 hours of astronomy. there is planning for star parties and events at shopping malls and libraries. Contribute to outreach web page development or work on developing and revitalizing the Centre's display. Mike concluded with a recommendation to check out the IYA web site.

The Canada IYA web site is http://www.astronomy2009.ca or in French http://www.astronomie2009.ca

Tim Cole followed with his presentation of Ottawa Skies for February (or what you would see if the sky was not cloudy). Comet Lulin is visible low in the sky. Saturn is back. It's rings are edge on and this time it appears at a sensible hour in the evening. A Kodak moment occurs before sunrise on February 22, when we would see the Moon, Mercury, Jupiter and Mars line up. On February 24, Jupiter, Mercury and Mars will be close together. And finally, near sunset on February 27, you would see Venus close to the crescent Moon.

Pierre Martin discussed Major Meteor Showers in 2009. 2009 is expected to be a very good year for meteor showers. And the moon will only affect the Eta Aquarids and the Perseids. But even with the moonlight, the Perseids are worth watching. Observers in Asia will be favoured for the peak of the Leonids on November 17. It will still be worth watching to see if anything unexpected does happen. In addition to the major meteor showers, there are dozens of minor showers and many more low level showers. There is a background of between 5 and 15 meteors an hour each night. One exciting thing about meteor observing is that we never know when one of these low level showers will come to life. This happened in September when one of these showers that followed the Delta Aquarids suddenly sprang to life, producing several bright meteors. But because it was not well known, only a few observers were covering the event.

Pierre then outlines the most promising showers for eastern Ontario. And since this is the IYA, when people ask about the night sky, tell them about these meteor showers and how little effort is needed to see them. The first shower of 2009 was the Quadrantids on January 3. The shower occurred in the east just before dawn. This was a good show, equal to the Perseids and Geminids. The Perseids is probably the most popular shower. For 2009, there is some good news - possible multiple peaks - and some bad news - the moon will be present. Jupiter and Saturn affect the Perseid meteoroids. In years when the densest part of the meteoroids is shifted closer to Earth, we get a better show. And 2009 is supposed to be one of these years. Activity begins in mid to late July and increases to a peak on April 12. A typical maximum rate is 80 meteors an hour. In 2008, a few hours after the normal peak, observers in Europe saw a new and unexpected peak of 120 meteors an hour. If this peak occurs in 2009, it will fall on August 13 at 4 am. The traditional peak is very broad and predicted to occur at midday. There are predictions for a sharp peak on the morning of August 12. The Orionids have produced abnormal activity for the past few years. October is known for bad weather. But the Orionids is a broad shower and even after the predicted peak of October 21, high rates should be observed. The good news is the moon will not be visible and enhanced activity is expected. The Geminids is the most reliable and prolific shower currently observable. This year, there will be a new Moon for the December 14 peak. The peak will occur near midnight, with the highest rates observable between 11 PM and 3 AM.

Shower predictions are regularly updated and refined as we continue to learn about meteorite science. Predictions can be updated until the last minute, but are not always posted everywhere on the internet. Several years ago, members of the North American Meteor Network set up an e-mail list called meteorobs to connect meteor observers around the world. Anyone with an interest in meteors is welcome to join.

After Pierre's presentation, Attilla commented that meteor observing is a stark contrast to all the high tech computer controlled equipment we use these days. He then asked how many people owned a computer controlled telescope. For his own telescope Attilla has 2 computers, 8 cables, 5 batteries, 2 versions of firmware, 1 radio link and 23 configuration options. And between 10% and 15% of the time he uses them, one of those things goes wrong. So what do you do? Learn to star hop.

Joe Silverman was next to show us how to do that. He presented Star Charts and Star Hopping. When high tech does not work, use a star chart. Many charts can be downloaded from the internet. Print the charts and put them in presentation folders. These folders do not reflect light. You can also download a planisphere. Google '7 mag chart', '8.5 mag chart', 'Telrad chart small' or 'washjeffplanisphere'. Begin star hopping by going after bright objects. M101 is a problem because it is dim. Joe suggests using Telrad charts. These charts show a wide area of the sky and there is one object for each chart. Joe knows many people who observe without using a finder scope. Instead they use a wide-angle eyepiece. Joe uses a refractor as a finder scope. When he looks through it, he is seeing stars down to mag 11 but he is using a 7 or 8.5 mag star chart. He starts with the Telrad and then goes to a wide-angle eyepiece. If he cannot locate the object, he switches to his finder scope. In his first examples, Joe showed locating a DSO near a bright star. In the case of M3, there is no nearby bright star. Then he sweeps using his finder scope. If there is no bright star close to your target, look at star patterns instead. Here is where the mag 7 star charts are better. M102 and M40 are two examples.

For star hopping, Joe's recommendations are Telrad, Telrad and Telrad. It is heavy, so just add weight. A Telrad is ugly, but you observe in the dark. It takes up a lot of space on the scope, but what else would you do with that space? The reticle brightness is adjustable so you can make it as dim as possible. There are circles that are 1, 2, and 4 degrees in diameter, which makes it easy to star hop. How are you going to find things you cannot see? The only way to do that is with star charts.

Joe concluded with a discussion about favourite observing sites. FLO is a good place for observing. There are very few places in North America where in less than 1 hour, you can be at a good observing site. You can also warm up in the building at the site and everyone is friendly. An excellent site is the Irvine Lake airstrip, also known as Nirvana. Everyone should try to visit this site at least once a year. La Verendrye is another good site but it is more than 3 hours away. He is often asked why drive all that distance, be bothered by mosquitoes, and lose sleep observing all night. Joe does it for the dark skies.

This was followed by a word from our sponsor. Tim Cole described the astronomy programs offered at the Museum of Science and Technology.

After a short break and the distribution of door prizes, the meeting continued with Members' Observations. Attilla Danko reported on observations of the January challenge objects: the Flame and Horsehead nebulas. Attilla recommended going to the Florida Keys for a good view of the Horsehead nebula. Gary Boyle reported that the brightest moon of the year occurred on January 10 and his yard was lit up by moonlight. He showed an image of Orion taken from the warmth of the house on a very cold night. And he photographed the ISS early in the month. Brian Burke began by showing the lights visible from his home. He also showed an image of the full Moon setting over the Gatineau Hills and one taken the following morning of the Moon over Metropole. Paul Comision then showed NGC6946,, Arp 29, and NGC1501. Paul Klauninger followed with comet Lulin, M31, M32, M110, lunar craters Alphonsus and Arzachel, the 600 kilometre long Apennine lunar mountain range and the Straight Wall, a 100 kilometre long lunar fault. Bob Olson showed the Flame and Horsehead nebulas.

Al Scott presented Spectroscopy - Fingerprint of the Cosmos Part 2. He gave part 1 of this talk back in 2002. This talk was about the Doppler shift: the frequency shift in the light emitted from an object due to the relative motion between the object and the observer. If the object is approaching, the light is blue shifted to a shorter wavelength, while if it is moving away, the light is red shifted to a longer wavelength. This is similar to the Doppler shifting of sound waves. As a train approaches, we hear higher pitches sound and we hear lower pitched sound as it moves away. The Doppler shift can also be used to detect planets orbiting around other stars and many planets have been detected. This is done by looking at a particular emission line in the star's spectrum over a long period of time and comparing it to the same emission line measured in the lab. If you have a hydrogen alpha line being emitted by a star, you can measure how the line moves over time compared to the stationary lab frequency. The Doppler shift of the stellar line tells you how fast the star is moving toward you or away from you. You are really measuring how a planet is pushing a star backward and forward as it orbits. If there is more than one planet, the closest and heaviest one will have the biggest effect on the star's motion. Most planets discovered so far are at least the size of Jupiter, since they are the ones big enough to pull the star around so its motion can be detected. Scientists have only had the tools to accurately measure this motion for about 10 years. Many corrections are needed including correcting for the motion of the Earth relative to the stars as it orbits the sun. We are seeing planets that orbit close to their star because we have not been observing long enough to detect other planets.

You can also measure H alpha emission from all the stars in a galaxy and see the rotation of the galaxy. If you add up the mass of all the stars in the galaxy, it is not enough to account for the measured velocities. So there is dark, or unseen, matter in the galaxy that is causing the rotation speeds. This is also how scientists measure the mass of a black hole at the center of a galaxy. You can measure the Doppler shift of x-ray peaks. The iron K line is an isolated line used to learn about black holes. And the Doppler shift of the 21 centimetre line is also measured. Hubble measured the red shifts of galaxies and discovered that the farther away the galaxy, the farther the lines of its spectra were shifted to the red. The most distant galaxies are moving away so fast that the H alpha has been shifted to the infrared. The most distant object we can see is the echo of the Big bang. It has been shifted to radio frequencies. We cannot see any farther back than to the time when the universe was 3000 Kelvins and atoms first formed. This has been red shifted to 3 Kelvins. Some of the static on our TV is from the Big Bang. Spectroscopy is the fingerprint of the cosmos.

Attilla then explained the process of giving a talk with Guidelines for Presenters. Propose a talk. Send him an e-mail at danko@pobox. com or talk to him with an idea. The qualifications are it should be about astronomy and it should be fun. If you are afraid of Power-Point, there is help. And if you are afraid to get up and talk, remember we are all friends. Attilla's suggestions for great talks include a constellation tour, favourite objects or a favourite observing site. Other ideas are gear for the cheap and clever (gear you have tested),gear for the rich and friendly, telescope making, gear you have built or outreach reports. To encourage telescope and equipment making, Attilla is offering a prize for the best talk about a construction project.

Pierre Martin gave the first brief outreach report. On December 6, Dr Jaymie Matthews lectured at the museum. His talk was about the MOST telescope. Unfortunately, the public star party was clouded out. But there was a telescope display and handouts were available.

Eric Kujila reported on a visit to his son's school and took his first telescope and Hubble slides. The kids want to learn. They like things they can touch and enjoy question and answer sessions. Eric told the kids they could go to space if they study. He encouraged others to go and give a talk.

Astronotes editor, Paul Wefers Bettink, presented Astronotes Article of the Year Award to Mike Earl. He has written many articles. The award was given for his July article about the Hickson 50. This was the first award he has won in astronomy. Mike writes because he wants to learn and share what he has learned. He puts 100% into his writing. Thanks to Paul Comision for introducing him to the Hickson galaxies.

Mike is coordinator for the night sky conservation program. He suggests getting people interested in astronomy first and then introducing light pollution. Check out his web site: www.castor2.ca/nsc

February Observing Challenges:

Deep Sky: Attilla's Pick Observe M44, the Beehive Cluster. Observers with appropriate equipment (large scopes or imaging capability) are challenged to observe the galaxy cluster behind M44.

Lunar: Brian's pick

This challenge is for a technique, not a specific target. Taking photographic negatives of lunar images often reveals detail not visible in the normal positive shots, because our eye is optimized to detect certain types of contrast. The challenge is for lunar imagers to use their image-editing software to produce photo-negative versions of some of their images, and to bring examples of images where the use of positive and negative images reveals interesting different details.

Thanks to Ann and Art Fraser for the after meeting refreshments. Special thanks for a $500 donation to the Centre from the coffee fund.

Iridium 33 & Cosmos 2251: Historic Collision

By Michael A. Earl

On June 16, 1993, a Russian satellite was launched from the Plesetsk Cosmodrome, 800 kilometres north of Moscow. Cosmos 2251 was a military communications satellite that served faithfully in this capacity until 1999 when it was deactivated and left a derelict spacecraft. It remained that way for nearly 10 years.

On September 14, 1997, an American satellite was launched from the Tyuratam Cosmodrome, 2,100 kilometres Southeast of Moscow. Iridium 33 was a telecommunications satellite that was a part of the worldwide Iridium satellite telephone service. It faithfully served until the sudden end of its life nearly 12 years later.

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Figure 1: The American Iridium 33 & Russian Cosmos 2251 satellites.

At 11:56 a.m. EST February 10, 2009, the unthinkable happened. These two satellites made history by being the first fully intact payloads to collide. The satellites destroyed each other, leaving several hundred pieces of debris in its wake. This debris will be posing a major threat to other active satellites for several decades.

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Figure 2: The orbits of Iridium 33 and Cosmos 2251 at the time of the collision, as viewed directly above the collision point (black dot). Earth and orbit imagery by Analytical Graphics Inc.

Iridium 33 (600 kilograms) and Cosmos 2251 (900 kilograms), collided at an angle of 103.3 degrees with a relative velocity of 9.2 kilometres per second. That’s 33,000 kilometres per hour or 26 times the speed of sound. The two satellites collided 788.6 kilometres directly above a point on the Earth 97.86 degrees east longitude and 72.51 degrees north latitude; the extreme north of Siberia.

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Figure 3: The collision angle of Iridium 33 and Cosmos 2251 as viewed from directly above the collision point, denoted by the black dot. Earth and orbit imagery by Analytical Graphics Inc.

Shortly after the collision, accusations flew from all directions. Iridium stated that “it had no advance warning of the impending collision”. A Pentagon spokesman stated that "We did not predict this collision," and "There are limits on your ability to track and compute every piece of orbiting man made object." A Russian technology expert had stated, “The U.S. side might have been unaware of, or had ignored, the possibility of the two satellites smashing into each other”. This is not surprising behaviour, given such an unprecedented event.

This is somewhat reminiscent of an elementary school, in which something has been accidentally broken and nobody wants to admit they had any part in it. The first kid is saying, “Don’t look at me, I should have been told that my toy was in danger”. The second kid is saying, “Don’t look at me, I don’t have eyes in the back of my head.” Finally, the third kid is saying, “Don’t look at me, I was just minding my own business, but those two should have known better.” The damage to Iridium’s 66-satellite infrastructure was minimal. After the loss of Iridium 33, the Iridium Company immediately moved one of its orbiting spares to take Iridium 33’s place. Regular service was restored in a matter of a few days. The damage to the orbital vicinity of the collision might be more severe, as up to 1,000 pieces of debris from the collision will be orbiting for several decades, threatening other functioning satellites, including the remaining functioning Iridium payloads.

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Figure 4: 153 pieces of Iridium 33 debris are plotted to 35 minutes after the collision. Notice how the debris spreads out after the collision. The collision point is denoted by the white dot. Earth and orbit imagery by Analytical Graphics Inc.
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Figure 5: 354 pieces of Cosmos 2251 debris are plotted to 35 minutes after the collision. Notice how the debris seems to spread out more than the Iridium 33 debris. Earth and orbit imagery by Analytical Graphics Inc.
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Figure 6: 153 known pieces of debris from the Iridium 33 satellite are shown here at 00:00 UTC March 6, 2009. There are likely many more pieces of debris to be found. Satellites are not to scale. Earth and orbit imagery by Analytical Graphics Inc.
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Figure 7: 354 known pieces of debris from the Cosmos 2251 satellite are shown here at 00:00 UTC March 6, 2009. There are likely many more pieces of debris to be found. Satellites are not to scale. Earth and orbit imagery by Analytical Graphics Inc.

Currently, our known satellite population contains 13,000 to 19,000 objects, depending on which press release you read. Imagine trying to determine all the potential collisions 24 hours a day, 7 days a week! With each new satellite launch, the number of satellites grows, thereby increasing the probability of collision. Despite enormous efforts to prevent this type of satellite mishap and the often-stated “improbability” of collision, two full size satellites still managed to collide. Maybe the attitude that prevailed until now was: “Until a collision actually happens, it is impossible”.

The problem inevitably comes down to who had too little responsibility and who had assumed too much responsibility with respect to conducting regular tracking of debris, producing collision reports and especially investigating the liability of collisions. You might imply from the respective press releases that Iridium is assuming too little responsibility, NORAD is assuming too much responsibility and Russia is assuming very little to no responsibility. If true, is this the right balance of responsibilities for the current circumstances?

Hindsight being 20/20, many have been saying that this collision could have been avoided. Unfortunately, that does not help Iridium 33. Yes, the collision could have been avoided, but it wasn’t. Now is the time to figure out why, not dwell on something that has already happened and cannot be reversed.

CASTOR’s wide field camera was able to detect both Iridium 33 and Cosmos 2251 during its “Sputnik 50th Anniversary Bonanza” in 2007. The question I have is why should two large satellites so easily detectable be so easily overlooked as far as a collision is concerned? Was the calculated probability of two fully intact payloads colliding much smaller than that of a piece of debris hitting a payload?

Collision probability reports are everywhere, but they obviously did nothing to help Iridium 33. The best method of protecting our active satellites is not only to calculate collision probabilities, but to track all detectable satellites as accurately and as frequently as possible. The aforementioned Pentagon statements suggest that this is no longer being done as frequently as required.

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Figure 8: Negative cropped CASTOR images of Iridium 33 and Cosmos 2251. Iridium 33 was detected at 00:20:47.481 UTC February 11, 2007 (nearly two years before the collision). Cosmos 2251 was detected at 01:54:16.495 UTC on April 20, 2007. Iridium 33 was 783km in altitude and Cosmos 2251 was 785km in altitude, respectively.

Using orbit elements from both satellites, I had determined that the minimum predicted distance between Iridium 33 and Cosmos 2251 at the time of the collision was 830 metres, much smaller than the 5 kilometre threshold that NORAD uses for its collision reports.

Currently, there are two strategies to reduce the probability of satellite collision:

1) Constant vigilance over the entire satellite population. This would involve spending larger amounts of money to increase the tracking frequency and accuracy of all detectable satellites orbiting the Earth; and/or

2) Debris removal and disposal. This would involve spending even larger amounts of money to design, implement and launch specialized satellites that would capture and de-orbit derelict satellites.

Strategy #2 has never been implemented in all 51+ years we have been launching satellites. However, several satellites, including SkyLab and MIR, were deliberately de-orbited. The Chinese used an anti-satellite missile to destroy a Fengyun 1C weather satellite in 2007. One year later, the American classified USA 129 satellite was destroyed the same way. With the Pentagon’s admission that the U.S. military cannot possibly know the whereabouts of all satellites at all times, strategy #1 is now cast into some doubt.

What NORAD has been doing over the past 51+ years is nothing short of phenomenal. It has been actively tracking the vast majority of satellites and producing collision avoidance reports for satellite companies; warning them of potential collisions. The hardworking men and women likely received little or no praise preventing collisions before this collision occurred, but get most of the blame (from Iridium, the Russians and possibly the Pentagon) afterward. A fair question to ask would be: How many satellite collisions have been prevented because of NORAD’s efforts?

Several days after the collision, a chance fireball was spotted over Texas and Oklahoma. Many believed that it was a piece of the collision debris. Although the object in question was eventually proven to be a meteor, the event shows that many were still very much focused on the collision's after-effects.

There are currently no international laws regarding satellite traffic control in place; especially when collision liability is concerned. The long-held belief that throwing satellites into "wide open space" is a harmless exercise is now gone forever. What will be replacing it?

Maybe one day the satellite industry will begin acting as its own satellite traffic controlling body. This move could serve to offload responsibility, stress and blame from NORAD as well as focus the satellite industry to produce more accurate satellite tracking data and collision avoidance strategies. Meanwhile, NORAD can spend more time on its “high priority” satellites and dealing with potential security threats. Would NORAD agree to offload a portion of its satellite tracking responsibilities to private industry?

The science of satellite tracking has officially entered a new phase in its evolution. No matter what chain of events led to the collision, warning signs had certainly been missed. This oversight led to the destruction of an expensive piece of space hardware. Whoever takes the blame will ultimately decide what happens next.

Iridium 33 and Cosmos 2251 will always be part of the CASTOR Satellite Catalogue as #0237 and #0534 respectively. The catalogue now has two disturbing additional amendments: “destroyed by collision at 11:56 a.m. EST February 10, 2009”. In the realm of the satellites, this date should never be forgotten.

A Local Observer’s Report of Comet Lulin

Hello Pat (Browne),

Comet Lulin (Comet c/2007 N3) seems to be a strange one. Although it orbits in the same plane as the major planets, it’s going in the opposite direction. It has a short spiky tail, but it seems to be pointing towards the sun instead away from it. The green colour just adds to it’s the unusual nature.

Before I went to bed Monday night [Feb 23] , I checked the sky and saw more clouds. Knowing that a clear sky could happen during the night, I made a mental note to get out of bed and look again if I woke up in the early morning. It was 4:15 a.m. when I next peeked at the clock, so I tiptoed to the front window. When I saw stars, I put on a housecoat, pulled on socks, slipped on shoes, and headed for the back door.

Saturn was easy to spot without binoculars or a telescope, and close by was a fuzzy spot – Comet Lulin. Although, I didn’t stay outside in my pyjamas very long standing in the snow, I was happy to see Comet Lulin at last. The forecast is more clouds tonight, so I don’t know when good viewing conditions will be back for another sighting.

Neil Carleton

Almonte, Ontario

Seasons for the Astronomer and the Astrologer

by Richard P. Taylor RASC Ottawa Centre and PAS Manila

Last month I wrote about the very obvious effects of the tilt of the Earth's axis: the seasons. This month I would like to continue with some more subtle effects that are of interest to astronomers. But some of these effects were noticed by ancient astrologers and still have an impact on people's superstitions.

The 23.5 degree tilt of the Earth's axis relative to the plane of the Earth's orbit around the sun makes it appear that the sun follows a particular path in the sky that is tilted relative to the projection of the Earth's equator. In summer for the Northern Hemisphere, the sun appears to be north of the equator; in winter it is south of the equator and at the spring and fall equinoxes it crosses the equator. This path is called the ecliptic, and ancient astronomers highlighted it with a set of 12 constellations called the zodiac. The progress of the sun on this path in the sky is so regular and predictable, we can figure out which constellation of stars the sun is in at any time of the year, even though it is impossible to see that constellation at that time because of the sun's glare. The zodiac constellation that is highest at midnight is the one where the sun will be six months later. This amazing ability to predict the future by observation and calculation tempted people to make further, less accurate predictions, called horoscopes.

As I write this at the end of January, I can't predict exactly when you will be reading it, so let me be cautious and make some predictions for the Ides of March (March 15). If you go outside at noon on March 15, I predict you will not be able to see any constellations. Furthermore, you will definitely NOT be able to see the constellation Pisces on that day because the sun will be in that constellation. On the other hand, if you go outside at midnight that day, and if it is clear, you will be able to see the constellation Leo. No, I can't predict if you will meet the love of your life, nor if someone will stab you in the back that night. However, I am fairly confident that you will also be able to see the planet Saturn amongst the constellation Leo if it's clear on the evening of the Ides of March this year.

This is the other amazing and magical thing about the zodiac. Not only does it mark the path of the sun in the sky, but it also marks the paths of all the other planets! They don't all stay exactly on the ecliptic, but in general, all the planets stay within a few degrees on either side of it. This makes for some interesting conjunctions (times when two of more planets are close together in the sky) and even the occasional occultation (when the moon passes in front of a planet). The sun's overwhelming brightness prevents us from seeing when it passes in front of a planet, but very rarely, we do see Mercury or Venus pass in front of the sun. I was lucky enough to see the last transit of Venus in 2004, and the next will be in June 2012. All of these coincidences come about because of the way our solar system formed. We now know that because of gravity, friction and conservation of angular momentum, a cloud of slightly rotating gas and dust will first collapse into a rotating disk, and then into a flat solar system with planets orbiting a star all in the same plane and same direction. It took thousands of years for people to figure out our own solar system, but now we are discovering new, similar solar systems around other stars.

What else can we observe that is related to the Earth's orbit and tilt? Well, once again we can use the magic words "conservation of angular momentum" to explain that the Earth's axis of rotation always points in the same direction, even as we revolve around the sun.

Observationally, this means that the stars seem to be moving in circles around us, but the star that is in line with the Earth's axis doesn't seem to move at all. Polaris, the North Star, is almost in line with the northern extension of the Earth's axis (it's actually about 3/4 of a degree away, and makes a very small circular path in the sky.) Navigators have used this star for centuries to show them the direction of North. Polaris can also be used to find your latitude: the angle that Polaris makes with the horizon is about equal to your latitude. Where I am now in Ottawa, Polaris is about 45 degrees above the horizon, and the constellation it is in, the Little Dipper, rotates on its handle once per day. Where I was in the Philippines, Polaris was about 15 degrees above the horizon, so the Little Dipper dipped below the horizon for half the time. If you were to move to the Southern Hemisphere, Polaris would never be visible, and unfortunately there is no bright star near the southern extension of the Earth's axis. So the constellations that you can see will be different depending on your latitude.

People near the equator can see all parts of the sky at some time of the year, but the farther north or south you move, the less variety you will see. At the North and South Poles, half the zodiac constellations cannot be seen. Just recently, my daughter was watching a science fiction show and it described a quest for a place where all the constellations of the zodiac were visible at once, in a big circle in the sky. She asked me is this was possible. It took some thinking, but here's the answer: yes, the constellations of the zodiac will be arranged in a big circle around the horizon if you were on the Arctic or Antarctic circle (latitude 76.5 degrees north or south) at sunrise or sunset. However, since the sun would also be on the horizon, its glare would prevent you from seeing any of the constellations. Just before sunrise, or just after sunset you might be able to see some of the brighter stars in the zodiac constellations, but only parts of each constellation would be above the horizon anyway. So the real answer is no, there is no place and no time when all the zodiac constellations are visible at once.

I've just spent the entire morning puzzling over that last paragraph, and re-writing it three times. It's really hard to visualize without a three dimensional model! Here's some more explanation (now that I have done all that thinking, I don't want to forget it.) Picture the solar system as a flat disk with the Sun in the middle and the Earth moving in a counter-clockwise circle on the disk (viewed from "above" in our Northern tradition.). Since the Earth's axis is tilted 23.5 degrees relative to the disk, the part of the Earth that is "on top" will not be the North Pole, but will be a place on the Arctic Circle. From that place "on top" the plane of the solar system, the ecliptic, will be on the horizon, and the Sun will be on the horizon too. So it is sunrise or sunset - but which one? Well now we have to think about what happens on the Arctic Circle throughout the year. On December 21, the North Pole is tilted away from the Sun, so on the Arctic Circle you would see the Sun briefly on the horizon at noon. Each day after that, the sun would rise a bit earlier before noon and set a bit later after noon; the ecliptic would be on the horizon at sunrise when you are "above" the North Pole and the ecliptic would be tilted to hide the Sun at night and show it during the day. This will continue until June 21 when the day will be 24 hours long. The ecliptic and the Sun will be on the horizon at midnight. Then from June 22 to December 20, the days will get shorter and the ecliptic will be on the horizon at each sunset.

     
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The Arctic Circle is a place with major variations in the length of day throughout the year, and major variations in the appearance of the Ecliptic. However the pattern is similar but less pronounced everywhere else in the Northern Hemisphere. The important result for amateur astronomers is that the best times for observing planets is Winter and Spring when the ecliptic is maximally tilted (relative to the horizon) during the evening and early part of the night. In summer and fall, it might be warmer and more comfortable to be outside, but the planets will be closer to the horizon until early morning.
     
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Polaris and the Little Dipper (Guardians of the Pole) from the Philippines.
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