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.
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.
The sky is always stunning to look at no matter what day it is, but this week promises some pretty cool activity for stargazers. The emphasis this week is on the solar system. To begin with, the pairing of Jupiter and Venus in the west has been stunning for several days now and is approaching the two planets are approaching their closest distance. Tonight (Monday) they will be 3.1° apart (roughly two finger widths at arm’s length, your clenched fist is about 10°). The two planets will be just 3.0° apart on Tuesday night as Venus and Jupiter begin to switch orientations. This conjunction promises a stellar view for binocular viewers and some telescope viewers at lower power.
Next up is Saturn which rises just before 10pm (EDT). Always a stunning sight no matter what time of year, but Saturn’s rings are tilted just about at the optimal angle for viewing from Earth. Over the next couple months the rings will start to flatten out until they will be seen edge-on. Also, Saturn, the moon, and the star Spica will dazzle in the sky around midnight tonight and Tuesday.
Mars is currently trekking its way through the constellation Leo this month. Each day it is getting closer to Regulus, the brightest star in Leo and the foot of the lion. Mars is just past its closest distance from Earth and is quite a pleasing sight in a larger telescope at its highest point from 11pm to 1am.
Since the moon is rising late this week we have another chance to view comet Garradd as it zooms through the inner solar system. Garradd is still at magnitude 6.0-7.0 so you likely still need to drive away from the city lights a bit to see it with a telescope. The comet is currently hanging out near the bowl of Ursa Minor and λ Draconis on Friday night.
So since I’m new to the whole astronomy gig I figured I must do what every new amateur astronomer must do and start mapping out the night sky on your own! I have no idea how I’m going to do it just yet but hey, it can’t be that hard! The ancient Egyptians figured it out 5000 years ago so I should be able to do it completely with my iPhone in one week, right? But seriously, I think it would be really cool to make a record of the movements of the stars and planets on my own. I’ll start with the planets to keep it simple for now. Jupiter, Venus, and Mars are all fairly visible at night right now. The moon should be pretty easy also. As long as there’s no complex math involved in the process I’ll be OK. I have a compass on my phone and I know all about angles of declination and the parallax angle and all that fun stuff but if you have suggestions feel free to comment away!
As I’m writing this I’m regretting not thinking of this sooner so I could have started on the first of the year But such is my life. For now I’m waiting here drinking some Jack Frost tea waiting for the clouds to break so I can log Jupiter and the moon for tonight. That is all for now. Good night planet Earth!
I’m home from work sick today and I’m watching a show called “The Planets” on the Science Channel about the gas giants and I have to say that it is fascinating! I didn’t know that NASA’s 1977 Voyager mission to the outer solar system was executed to coordinate with a perfect planetary alignment that happens only once every 175 years. Although we don’t know for sure how the outer planets formed you sure do learn something new everyday on the Science Channel!