Memorial Day weekend was very productive for me. A couple weeks ago I purchased my first DSLR camera, a Nikon D3100 and I’ve been itching to start photographing the night sky. My first big target was the planetary alignment of Venus, Jupiter, and Mercury over the weekend which did not disappoint. I was able to shoot the planets on both Saturday and Sunday nights under perfectly clear skies. This was a relatively easy target for my first foray into the world of astrophotography.
On Saturday night I took my camera and tripod up to my dark sky site in Fawn Grove, Pennsylvania. I arrived around 8:30 just as the sun was setting. While darkness was gathering I set up the camera and punched in the initial settings and waited for Jupiter to appear. Venus was already brilliant approximately ten degrees above the horizon by 8:45. Jupiter appeared minutes later, followed by Mercury visible to the naked eye around 9:00. I played with the aperture and shutter speed until I captured an image I really liked. I ended up with a focal ratio of f/8 and a 1.6 second exposure at ISO 100. The final result once I played with it in Photoshop was very nice, as far as my inexperienced self is concerned. That’s Venus at the bottom of the triangle, Jupiter at upper left, and tiny Mercury at upper right.
This was just practice for Sunday of course. Sunday’s alignment was the one that captured everyone’s attention. The almost equilateral triangle of planets is something you won’t easily forget if you saw it for yourself. If you missed it you’re in luck because photographers all over the world captured the stunning alignment. I’m relatively happy with how mine came out. The only drawback is that the planets are slightly out of focus. I should have been paying closer attention to that. However, them being out of focus kind of allowed more color to come out, especially in Mercury. I worked with the same camera settings as Saturday night. After some adjustments in Photoshop this was my final result.
After the planetary imaging session I was feeling lucky so I tried my hand at some wide-angle constellation shots. I turned the camera towards Ursa Major and took 200×10″ frames and went to stack them in Deep Sky Stacker only to find that my images were out of focus and DSS couldn’t recognize any stars. Not so lucky I guess. I was determined to get it right so I went back outside around 11:30 and decided to shoot the constellation Lyra and it’s bright star Vega. This time I took 200×1.6″ frames at f/4, ISO 3200 and went in to stack them in DSS. The result was much, much better. About 2 hours later I had a decent image with which to work with. I gave it several editing passes in Photoshop before I produced an image I was happy with. Not only are all five of Lyra’s main stars visible, the double star Epsilon Lyrae showed up which really made me proud. This is my first constellation shot so I guess it’s the small things that bring me joy.
Overall, it was a very productive weekend. I learned a lot about how important it is to really nail the focus before shooting anything. Trial and error is how you improve in this hobby. I’m hoping to get a few more practice shots under my belt before taking the camera up to Cherry Springs State Park in a week and a half to shoot under a real dark sky. As I produce more images I will post them here so I hope you stick around and if you have any suggestions or critiques to help improve my technique I’d gladly appreciate it.
I think it’s a safe assumption to say that whenever anyone gets into astronomy their greatest desire is to be able to take pictures of what they observe. The saying that a picture is worth a thousand words is certainly true of astrophotography. There is certainly a great joy in observing the universe with your own eyes at the eyepiece and that should unequivocally be any amateur’s first love. Given the mass-availability of photography equipment and astro-imaging software and techniques it is no surprise that astrophotography has risen to such popularity in the 21st century. All someone has to do is watch a couple of tutorial videos on YouTube and you have a pretty good sense of what equipment and software you need and it’s easy to practice the techniques employed by more experienced photographers.
I’ve decided to jump on the astrophotography train myself. Mind you, I don’t own a fancy equatorial mount for my telescope or even a DSLR camera for that matter so I have to try a slightly different method to get images. By far the best and easiest way to do astrophotography with a Dobsonian mounted telescope is with a webcam. This method is really only useful for planets, the moon, and sun given that images of deep-sky objects requires long exposures that would produce star trails if not tracked. However, it was extremely rewarding producing my first planetary image.
I’m not going to go into detail on how I captured my images because that would just be an incredibly long post. Instead, I just want to share the equipment and software I used to give you a sense of how easy (and inexpensive) it is.
My telescope is an Orion XT10i Dobsonian which already provides very nice planetary images in the eyepiece. Images are always sharp and bright when in focus. For this experiment I purchased a Microsoft HD Lifecam from my nearby Staples office supply store. I went with the Lifecam because it has a body that is perfectly designed to fit inside any 1.25″ focuser tube. The Lifecam can also shoot 1280×720 720p video at 30 fps (after some tinkering) which is something special for a webcam. I followed the instructions provided by Gary Honis, who is the authority on all things webcam photography related, on his website, found here. I didn’t use the 1.25″ barrel extenders like he did, rather I used a film canister. The film canister seems to work just fine and it fits snugly into the focuser.
To capture the video I downloaded a piece of software called AMCap which is freeware video capture. It’s available for a free download but a donation is asked for, but not required. Also, a jpeg video codec is needed to capture the raw video in .avi format. Any jpeg codec you can find will probably work but Gary recommends a particular one on his software tests page. Finally, I used Registax 6 to stack the images from the raw .avi video and touched it up a bit in Photoshop CS6 an voila! a nice, crisp, clean image of Saturn.
This method is very easy to do for anyone without a tracking mount and what’s best is that it only cost me $35 plus shipping and handling. If you have a Dobsonian telescope this method is definitely for you.
I’ve always been a conservationist and an eco-minded person since my days in Boy Scouts. We learned that nature is should be respected and cared for and as much as possible we should live in harmony with our surroundings. However, when you’re able to see pictures of the Earth from space your whole perspective changes. I’m sure most people are familiar with the famous “Earthrise” photograph taken by Apollo 8 astronaut William Anders in 1968. ”Earthrise” gave a whole new perspective of our home planet and gave realization to the fact that our planet is just a fragile little island floating in an unimaginably huge universe. Imagine being in the position of Anders or any of the Apollo astronauts as they saw the Earth rise over the lunar surface and realized that everything they’ve ever experienced, everyone they’ve ever known, all their prior life was 250,000 miles away on that small blue rock.
Few people have had the privilege to see the Earth from space, whether from low orbit or during a lunar mission but we’ve been able to vicariously experience it through the photos and films they’ve brought back that have left us stunned. One such striking video was recently compiled by NASA’s MESSENGER probe as it left the Earth on its way to Mercury. The probe had a camera pointed back towards the Earth as it left it behind and the stitched together frames produced in image of stunning beauty and inspiration. As the Earth slowly fades away into the blackness of space we realize our true place in the universe. We are but minnows swimming in a vast, vast ocean.
Even with the potential of planetary travel and colonization in the distant future we must still place immeasurable value on our home planet. The Earth has been so good to us for millions of years and will continue to do such if we take proper care of it. As a whole, the human race is awakening from a slumber of environmental torment. From the mid-to-late 1800′s and the dawn of industrialism we have polluted the planet to a sickening degree. We’ve deforested much of the rain forests and polluted the water we drink and the air we breathe. For over a century we were largely oblivious to the damage we were doing to our fragile environment. But now we’re waking up to the consequences of our actions. It is not too late to reverse the damage we’ve done to our planet because she is a resilient creature. But that should not give us a license to continue to damage her and squander the beauty and riches of our island home.
Even if we travel to hundreds of planets in the future we may never find one quite like Earth (if we find any like it at all). We were placed here on Earth by divine decree and it is that same decree that should guide our actions going forward to restore and protect our pale blue dot, our fragile island home because it’s all we have.
Spring is finally in full swing and if you’re like me observing season is about to kick off again. I hate observing in the cold so when April rolls around it’s usually an indicator that better nights are coming…unless you live on the East Coast where it’s been unseasonably cold and cloudy for the last month. April is also exciting because it is Global Astronomy Month. Each year since 2009 Astronomer Without Borders has designated April as Global Astronomy Month to raise awareness for the study of astronomy both professionally and amateur. In my opinion, the biggest part of GAM is International Dark Sky Week. Beginning tomorrow April 5 and continuing through April 11, Astronomers Without Borders and the International Dark Sky Association are teaming up to raise awareness of the issue of light pollution. If you’ve read this blog before you’re probably familiar with the light pollution as I write about it quite frequently.
Because of light pollution, the artificial brightening of the night sky, less than a third of Earth’s population lives under natural, starry skies. Fifty percent of Americans and 75% of Europeans have to travel at least an hour from their homes to see a natural star-filled sky unaffected by light pollution. From my home in Maryland I have to travel 4.5 hours to reach the only truly dark sky spot around, Cherry Springs State Park in Potter County, Pennsylvania. I am willing to make this pilgrimage once or twice a year but there should be somewhere closer to observe from that has a quality dark sky. The reality is, however, that these places are slowly dwindling in number. Artificial light, the scourge of the night sky, is slowly but surely conquering the beauty of the natural night sky.
Light pollution comes from poorly designed artificial light sources we use at night. Most of these light sources are from street lights that are unshielded so that light escapes upwards into the air which causes the light particles to scatter and create that familiar sky glow effect. Other problems are that we often use wattage that is too high for the task we’re trying to accomplish. If you’re using too bright of a light the light actually reflects off the ground and bounces back up into the sky to contribute to the sky glow.
You’ve also probably noticed the annoying glare that unshielded lights cause while driving. Glare comes from the bright ball of light generated by a typical drop lens or acorn style street light. See the example below for a typical “glare bomb”. The glare created by these lights can not only be annoying while driving, they can also be dangerous for people with poorer eyesight such as seniors or people with sight disorders. They are also so bright that they can mask important things like road signs and signals along with pedestrians and animals in the road.
Light trespass is also an result of poor lighting design. Light trespass occurs when a light from a neighbor or nearby building shines, or trespasses, on your property. For example, a stray light that shines into your bedroom at night that causes you to get inadequate sleep. To make a long story short, the lighting used should fit the requirements of the task it is trying to accomplish, no more, no less. We all agree that artificial light helps our society. But since when did extravagant over illumination become acceptable. Not only does light pollution affect the night sky, it is also a HUGE money waster! Every year over-illumination in the United States alone costs the same as approximately 2 billion barrels of petroleum and consumes unnecessary fossil fuels that are not replenish-able. Imagine how the cost of a gallon of gas could decrease if we didn’t over-illuminate our homes, businesses, and roads!
Fortunately, the solution for light pollution is relatively simple. Taking the time to assess your lighting needs and using the proper wattage and shielded fixtures will go a long way in reducing the amount of artificial light we send up into the night sky. Using shielded fixtures ensures that the light only goes where it is needed: the ground. This also allows for a lower watt bulb to be used and that in turn reduces the amount of light reflected back off the ground. Motion sensor are also useful to turn the light on only when there is movement.
Talking to neighbors about their lighting in a polite but concerned way is a great way to introduce the topic to them. Writing to legislators can be effective as well. There have been a number of municipalities that have incorporated lighting regulations into state, county, or local code in recent years. There is a bill in Maryland that is currently in the General Assembly that would require all new light fixtures purchased by state agencies to be fully shielded. The biggest hurdle we have to overcome is simply making people aware that there is a problem. Many people don’t even think about the light they see at night or how their lights are contributing to the pinkish glow we know all too well. In order to reverse the effects of light pollution we must use word of mouth to let people know that light pollution is real and it is diminishing the beauty of our night sky and wasting money in the process.
If you’d like to learn more about the issue of light pollution please read some of the other posts I’ve written on this blog and visit the International Dark Sky Association’s website www.darksky.org. Together we can put a cap on light pollution and restore the beauty of a star-filled sky!
A new space milestone has just occurred, or occurred around August 2012. The Voyager 1 space probe that was launched on September 5, 1977 has finally left the solar system. Thirty five years after its launch the audacious probe enters a new stage in its mission, exploring the region of space outside of the Sun’s influence.
The Sun’s influence in space extends way beyond the orbit of Neptune. We know that beyond the inner planets lies the Kuiper Belt which is home to Pluto and many, many other dwarf planets. Finally at about 18 billion kilometers from the Sun and four times the distance between the Sun and Neptune, is a region known as the heliopause. The heliopause is the region where the solar wind from the Sun collides with the interstellar medium, a collection of particles which is the collection of gas, dust, and cosmic rays. The solar particles are so dilute once it reaches the interstellar medium that the heliopause is considered the end of the Sun’s influence (although its gravity extends well beyond the heliopause to the Oort Cloud).
A new paper that has been published confirms the conclusions that were drawn about the solar wind particles back in December. Data from the probe showed that the number of subatomic particles coming from the Sun dropped dramatically sometime around August 2012 while the number of cosmic rays from the interstellar medium spiked. While it’s not exactly new news, it still is exciting to think about. There is now a man-made object outside of the solar system and is still able to communicate with us 18 billion kilometers away.
Eventually the plutonium inside of Voyager will stop producing electricity and communications will cease. At that point, the probe will continue to sail in the direction of the galactic center. There is an estimated 10-15 years of power left on the probe so we need to enjoy it while it lasts. It will be a long time before human travelers can journey this far from our home, but we’ll do it one day.
With the mid-Atlantic region being covered by winter storm ‘Saturn’ (not a fan of naming winter storms), comet C2011/L4 PANSTARRS is about to make its debut in the northern hemisphere. Observers in the southern hemisphere have been enjoying PANSTARRS for about a month already and it finally brightened enough to be a naked-eye object in the last week or so. While the usual naked-eye threshold is between magnitude +5 and +6 depending on your eyesight and sky conditions, comets aren’t point sources of light like stars and planets and their light is spread out over a larger surface are with respect to the entire sky so their brightness in magnitude can be a little deceiving. Right now PANSTARRS is hovering right around magnitude +2 which puts it theoretically as bright as the brightest stars in Ursa Major, the Big Dipper. For us in the northern hemisphere though, it likely won’t appear as brilliant as it is in the southern hemisphere because of it’s proximity to the sun. The comet is expected to make its northern debut tomorrow, March 7th after sunset. The problem for us is that it is approaching its perihelion, its closest distance to the sun, so it will only be visible during twilight. Picking PANSTARRS out might be difficult and it might only appear to the naked-eye as a small fuzzy ball barely creeping over the western horizon.
That being said, binoculars will be a great aide to those looking to spot PANSTARRS early on. The comet won’t get much higher than 10° above the western horizon. Ten degrees is approximately the size of your clenched fist held at arms length. In order to spot PANSTARRS in its first couple of days in the north you’ll have to find a viewing location that has an unobstructed view of the western horizon that is reasonably dark. Getting away from street lights and house lights is key as they both create a glare that makes it difficult to see and limits your eyes’ ability to adapt to the growing darkness. A rooftop that can be safely accessed might provide a good vantage point to spot the comet.
In a simple pair of 10′x50′ binoculars you should be able to see the dust tail that stretches several degrees beyond the comet’s nucleus. Whether or not an ion tail produced by the solar wind will be visible remains to be seen. As March wears on the comet will steadily rise in the western sky each night as it moves further away from the sun. Again it won’t get very high in the sky but at least towards mid-March you should be able to view it in reasonable darkness until about 7 pm. I’ll be away on a retreat this weekend in a semi-dark region at the top of the Chesapeake Bay so I hope to be able to snap a few pictures of PANSTARRS. I will certainly post anything that is decent.
For now, as winter storm ‘Saturn’ dumps mostly rain on me, I had to settle for this amazing timelapse video of comets Lemmon and PANSTARRS in the sky together. This was taken by Australian astrophotographer and videographer Alex Cheney. It is quite a rare sight to be able to see two comets in the same sky together! I swear those southern hemisphere dwellers get to have all the fun!
I’m sure you’ve heard the reports of the meteorite that entered the Earth’s atmosphere over Chelyabinsk, Russia this morning. For me it was a really great way to wake up and begin the day! Not 15 minutes after waking up and taking a shower I checked my Facebook and saw Phit Plait’s article on Bad Astronomy. Man oh man were those videos cool! It’s been a while since we had a daytime fireball like this. Although it’s being reported that hundreds of people have been injured by shattered glass and such, no serious injuries were reported.
The fireball appeared around 9:30 am local time in Chelyabinsk, Russia which is a city near the Ural Mountains, about 1500 km east of Moscow. It is estimated that the meteorite weighed about 10 tons, or 20,000 pounds. Upon entering the atmosphere the space rock began to break apart as seen in the train (the smoke trail) where it forms two columns of smoke. One video included below shows someone driving and captures some amazing footage of the fireball at the moment of entry. The meteorite blazes almost as bright as the sun while it glows white-hot from the friction of the atmosphere! Although it broke apart upon entry reports have come in that small fragments did indeed impact the surface. Mostly raining down as relatively harmless small chunks, several impact areas have been proposed.
By far the coolest part of the “impact” is the shock wave felt by residents that was caused by the meteorite breaking the sound barrier several times over. People hundreds of miles away from where entry occurred could hear the sonic boom. In Chelyabinsk, many windows were shattered and car alarms blared from the shock wave. I can imagine how startled and confused the residents might have felt seeing the giant train and hearing sonic booms like artillery fire. If I didn’t know anything about space and astronomy I’d probably assume that North Korea was attacking!
In case you haven’t already had this confirmed by dozens of media members and scientists, this is NOT related to the close shave we’re about to have with asteroid 2012 DA14 . The meteorite entered the atmosphere too early and was travelling the wrong direction to be a fragment of the asteroid. But it is a very cool coincidence that these two events would happen on the same day! That’s the nature of meteors and space, they can be totally unpredictable. I think this is further proof that we need to be able to detect things like this before they happen in case a much larger and more deadly meteorite were to impact us. Maybe it’s not a coincidence that both events occurred today. This Russian fireball and the close approach will hopefully serve as a wake-up call that more extensive near Earth object detection systems are needed to prevent casualties from impacts.
Anyway, enough rambling from me. Here’s some of the videos posted on YouTube from eyewitnesses. They’re pretty cool!
Car dashboard camera capture the fireball as it enters the atmosphere
I love this video because you not only hear the sonic boom, but you see the person’s reaction to the boom as almost jumps out of his pants!
Another longer video of a city street where you can hear glass shattering from the sonic boom.
I love hearing about light pollution in the news and media, especially when the stories are about people, towns, or governments taking action. That’s why when I read an article on guardian.co.uk about a new light pollution law in France I nearly did my version of the Ray Lewis dance! The new law is an attempt to both curb several aspects of light pollution. France’s Minister for Ecology, Sustainable Development and Energy, Delphine Batho, announced the new law yesterday directed towards lighting on non-residential buildings across the country. The new law will make it obligatory for shops and commercial buildings in France to shut off their interior, window, and exterior lighting at night.
The main aspects of the new law are as follows:
- Interior lighting in office buildings must be switched off one hour after the staff leaves the building
- Exterior lighting used for illuminating building facades may be turned on one hour before sunset but must be switched off by 1 a.m.
- Window lighting in commercial buildings must be switched off between 1 a.m. and 7 a.m.
Minister Batho announced the law hopeful for France’s future as a global leader in the fight against light pollution and all its negative effects. According to the non-governmental organization the Agence de l’environnement et de la maîtrise de l’énergie(ADEME), the new law will help France save two terrawatthours of energy each year (1 terrawatt is 1 million megawatts) which is enough to power 750,000 homes in France every year. These energy savings results in a reduction in France’s CO2 output by 250,000 tons each year.
As with almost every light pollution ordinance there are exceptions. Buildings that are tourist attractions year-round are exempt from the new law, as well as Christmas lights, and local holidays and festivals.
Minister Batho is hopeful that the new regulations will not only reduce France’s energy consumption, but also help preserve the nocturnal environment, limit health problems caused by excess light, and of course help improve the quality of the night sky. The law will go into effect on July 1, 2013 so if you’re an astronomer, professional or amateur, in France make sure you wait until after 1 a.m. to set up your telescope for the night! I can only hope this snowballs into bigger and better things for France and all of Europe in regards to fighting light pollution. Well done.Sources: Davies, Katie, The Guardian Online,
Myels, Robert, Digital Journal
de la Baume, Maïa, New York Times
Additional Resources: http://www.lampclick.com “Light Pollution: Effect on Humans and Energy Efficient Solutions“ Astronomers Without Borders Dark Skies Awareness Blog International Dark Sky Association
Last year I had the privilege of writing a short piece about the Dark Sky Festival in Harmony, Florida. I really enjoyed learning about the town of Harmony and the Festival they host every year so when I was asked again this year I jumped at the opportunity. This year’s Dark Sky Festival promises to be the most successful yet.
Once again the town of Harmony, Florida is pleased to present to you the 10th annual Dark Sky Festival! For the last ten years Harmony, a small town southeast of Orlando, has hosted a festival to celebrate the wonder of the Earth’s most beautiful natural resource, the night sky. On the night of February 2nd, 2013 the public is invited to attend a night of celebration and education focused on learning about the night sky and the benefits of living under a night sky free from the effects of excessive artificial lighting. The effects of excessive artificial lighting are scientifically proven to have negative effects on human and wildlife health, to damage the nighttime ecosystem, and of course mask the beauty of the starry night sky.
Harmony, Florida was founded in 2003 by Orlando’s former Humane Society/SPCA director Martha Lentz with the goal of creating a community where humans can live in harmony with nature and the environment. The town was master planned into one of the most unique communities in Florida. One of the goals of the community is to limit its impact on light pollution to preserve a natural view of the night sky. Light pollution is the sum of all the wasted artificial light that is shined into the sky as a result of poorly designed lighting fixtures. This wasted light produces the all too familiar sky glow effect that turns the sky pink near the horizon and washed out overhead. The effects of light pollution can be limited, and even reversed as residents of Harmony know. By taking simple and inexpensive steps to ensure all outdoor lighting fixtures are fully-shielded (meaning no light escapes upward from its source) Harmony has created a very aesthetically pleasing and environmentally friendly lightscape. Furthermore, the lighting regulations created for Harmony are so impressive that the surrounding county which includes parts of Walt Disney World has adopted them as a lighting ordinance.
This year’s Dark Sky Festival promises to be the most successful one yet. Over 5,000 people attended the 2012 Festival and again the town expects to see growth in attendance. Attractions of this year’s Festival include the following:
- Public stargazing with over 50 telescopes
- Speakers from NASA, Seminole State College Planetarium, the International Dark Sky Association, and more
- Two mobile planetariums with presentations and NASA Exhibits
- Variety of kids activities including Mad Science, demos from high school robotics clubs, glow-in-the-dark mini-golf and the Kids Zone
- Music, food, specialty booths, and presentations from scientists
This year’s speakers include International Dark Sky Association’s Executive Director Bob Parks and Jon Cowart, Deputy Partner Manager of NASA’s Commercial Crew Program. If you stick around long enough you might even run into some Star Wars characters from the famous 501st Legion!
Don’t miss this wonderful opportunity to learn more about astronomy and the dark sky movement as well as a chance to explore the universe first-hand through some incredible telescopes! Astronomers from around the state have their telescopes set up for free, public viewing. If you’re completely new to the field of astronomy or a seasoned pro the Dark Sky Festival at Harmony surely has something for everyone. Make sure you stop by the beautiful town of Harmony on Saturday February 2, 2013 to enjoy this rapidly growing annual celebration of the night sky. Festivities begin at dusk at 5 pm and continue until 10 pm.
To learn more about the town of Harmony please visit the town’s website www.harmonyfl.com.
When we look back, 2013 may be remembered as the Year of the Comets. As I’m sure you may have heard already we have two potentially immensely wonderful comets heading our direction this year; the first of which will be its closest to the Sun on March 10th. The more you learn about comets the more you appreciate how amazing the solar system is! When you consider what comets are, how they get here, and what on Earth makes them shine so beautifully then fade into oblivion for thousands of years you are left with a sense of awe because the answer to all of these questions is…the Sun.
Thanks to Nicolas Copernicus we know that the Sun is the center of our solar system and that everything in the solar system orbits the Sun on regular and predictable paths. You have the 8 major planets, the asteroids in the asteroid belt, the minor, or dwarf, planets of a region called the Kuiper belt, of which Pluto is a member, then far, far away from the Sun at a distance of almost one light year you is the region known as the Oort Cloud. The Oort cloud is a massive region of space mostly by tiny chunks of ice and rock left over from the formation of the solar system. These chunks of ice and rock are so far away from the Sun that they are approximately one-quarter the distance to the nearest star, Proxima Centauri. The Sun is barely more than a pin point of light out here and its gravity is just strong enough to keep these tiny chunks of ice loosely in orbit. However, the gravity is so weak that objects in the Oort Cloud are influenced by passing stars and the Milky Way itself. All it takes is the slightest gravitational nudge from another star to dislodge an ice chunk from its happy orbit and send it drifting slowly towards the inner solar system.
This is how we believe most long period comets are born. Long period comets are comets with highly eccentric (or lopsided) orbits that span between 200 and thousands, or even millions of years. Comet McNaught that passed through the solar system back in 2007 is a long period comet with an orbit of about 92,600 years. It’s safe to say that we won’t see that bad boy again in our lifetimes!
Once the ice chunk is dislodged from its orbit in the Oort Cloud it begins its long, slow journey towards the Sun. The Sun’s gravity begins to pull it in towards itself on an epic tour of the solar system that spans almost an entire light year (one light year is 6 trillion miles). Comets are typically no bigger than a hundred or so meters across but the Sun causes something to happen on their surface that makes them spectacular sights in the night sky. Out in the Oort Cloud it is mind-bogglingly cold. Before they turn into comets the chunks rocks and dust mixed with chunks of frozen water, ammonia, carbon dioxide or methane that are so cold they’re as hard as steel. But once they get close enough to the Sun they begin to heat up.
Once the comet arrives in the inner solar system the Sun’s heat begins to melt the ice and it begins to evaporate and glow brightly which is caused by solar ionization. The glowing cloud of evaporating gas is called the coma. Once the coma is formed the tell-tale…well, tail of the comet begins to form as the solar wind from the Sun blows against the comet. The comet, tail, and coma steadily brighten as the comet gets closer and closer to the Sun. They also begin to pick up more speed the closer they get. By the time a comet is visible on Earth it already has a dazzling coma and tail that can be as bright as the stars and perhaps even the planets!
It is once the comet is within the orbit of Mercury that the fate of the comet is determined. Most comets slingshot around the Sun at a safe distance that they make it around without a problem and begin their lonely journey back out of the solar system into oblivion. Other comets called sun grazers get so close to the Sun that they actually pass through the Sun’s upper atmosphere, the photosphere, or even the solar corona where the temperature is millions of degrees Fahrenheit. Some sun grazers make it out intact while others break apart and disintegrate, much like a frozen coffee mug when boiling water is poured in it. Others still are known as sun divers which literally plunge right into the Sun and are never heard from again.
Once the point of perihelion, or the comets closest approach to the Sun is reached the comet begins it’s journey back to where it came from. Depending upon the positioning of the planets on its return journey, some comets stay in orbit around the Sun and will eventually return. If a planet’s gravity nudges the comet on the way out it could end up being ejected from the solar system entirely and be doomed to roam the void of interstellar space forever. Whatever the fate of the comet we get to observe the magnificent effects of the Sun on them from the Earth, both visually and scientifically.
This year we have two potentially dazzling and memorable comets heading our way! The first of which is named comet C/2011 L4 PANSTARRS, or PANSTARRS for short. With a perihelion of March 10, 2013 it promises to put on a nice show throughout the months of March and April. Observers in the northern hemisphere won’t be able to see the comet until after its perihelion though. So be sure to get outside during clear nights in March and April to see this orbiting rocky ice clump. Currently, PANSTARRS is projected to get as bright as the planet Venus if everything goes according to plan with its passage around the Sun. PANSTARRS will be bright and low in the sky about 30 minutes after sunset in mid-March.
If you miss PANSTARRS or couldn’t get enough comet viewing action for one year you’re in luck! Even brighter and more spectacular than PANSTARRS will be comet ISON in the fall months. ISON is currently close to Jupiter on its voyage towards the Sun but will begin to be visible in binoculars in the beginning of October. By November 1st ISON will be within the orbit of Earth and should be a spectacular -6 magnitude! Astronomers measure brightness by magnitude with the lower the number being a brighter object. The planet Saturn is +1 magnitude and the brightest star in the sky, Sirius, is -1.46. By the time it reaches its perihelion on November 28th it is expected to reach a -12.6 magnitude which is as bright as the full moon! That means that as it passes next to the Sun it will be visible during the daytime if you use your hand to cover the Sun! ISON should put on a show of a lifetime during November and December and will truly be something to tell your kids and grandchildren about because ISON will likely never return. If you own a telescope or a pair of binoculars make time to get out with your friends and observe this marvelous comet. This one has the potential to be the brightest comet in recent history, brighter even than the famous Halley’s comet.
It never ceases to amaze me that all the wonderful things we love about comets, their beautiful tails and diamond-like sparkle is all due to the power of the Sun. We live in an active solar system that is constantly moving and it is all thanks to the Sun’s influence.