There’s not much cooler in the night sky than a comet.
That’s why we are all (yes, that should include you) getting very excited by the progress of Comet ISON.
“Hubble provides a close-up look of Comet ISON (C/2012 S1) from April 10, when the comet was slightly closer than Jupiter’s orbit at a distance of 386 million miles from the sun.”
Image credit: NASA, ESA, J.-Y. Li (Planetary Science Institute), and the Hubble Comet ISON Imaging Science Team
This celestial runaway began its journey over a million years ago and now it’s finally here as it makes its first trip through our inner solar system, stopping by to say hi to us folk.
(Image courtesy of cosmostv.org)
This comet is known as a ‘sun-grazer’. The clue is in the name. As it makes its orbit it gets very close to the sun. Its perihelion, meaning when it is the closest it will ever get to the sun, will be on November 28th. Now the question remains. Will ISON survive its close perihelion journey? Most sun-grazers don’t.
I mean really.
Look at that.
I sure wouldn’t want to get a mere 730,000 miles away from the surface of that thing.
And it’s not like ISON’s journey has been a carefree jolly from the outset.
Let’s see, over a million years ago, good ol’ ISON left his comfy home, otherwise known as the Oort cloud region of our solar system.
Something more like this:
(Image courtesy of http://downhousesoftware.wordpress.com)
If you ever fancy a trip, it’s on the very outskirts of our solar system where the sun still just about has the ability to exert its gravitational pull. Just go straight past Neptune and then about half way to the nearest star – you can’t miss it, I mean it stretches 5 trillion miles into deep space!
It’s a bustling place – scientists have predicted it to be the home of a trillion comets – all in need of a place to live after the formation of the solar system.
So, after years on end living in the same place, ISON eventually became gravitationally perturbed and began his sun-bound trip in search of new adventures.
When comets make these trips they pay no heed to the organised flow of the solar system and just come bombarding their way through, crashing into things if needs be (like 65 million years ago when the dinosaurs became extinct perhaps)? They certainly don’t travel around the sun in neat, little circles but rather trek in extended ellipses, which may or may not include a suicide approach towards the ball of flames.
(Image courtesy of http://starryskies.com)
It was Edmund Halley who first determined that comets return to our inner solar system on a periodic basis and are therefore predictable. Comet Halley who everyone has come to (sorry) know and love is due back in 2061, 75 years after its appearance in 1986.
We’ve been witnessing comets since the dawn of time. Here’e a depiction of The Great Comet of 1680 over Rotterdam. This comet was famously used by Newton to verify Kepler’s Law. Many people are drawing several distinctions between this comet and ISON, perhaps it is conceivable the two are related.
It’s worth mentioning at this point that the Oort Cloud is not the only home of comets. Comets that tend to make shorter trips i.e. have less than a 200 year orbit, like Halley, come from the Kuiper Belt which is closer to Neptune’s orbit. The long haul journeys are reserved for comets originating from the Oort Cloud. Of course, this place is simply a hypothesis as it is so far away we don’t actually know it exists, but it helps to explain the presence of long-period comets like ISON.
Comets are comprised of dust, ice, carbon dioxide, ammonia, methane etc etc etc. They are often referred to as dirty snowballs, although more recently snowy dirtballs.
See what they did there, those scientists heh?!
(Image courtesy of Gregory Kehrig http://www.flickr.com/photos/looking_and_learning/)
When they’re not playing with words some scientists theorise that comets are responsible for bringing some of the water and organic materials that made life here possible. But anyway, enough of this ‘beginning of the world’ chat, let’s crack on with the perilous adventure ISON is on.
So, right now he’s in a cool spot. Inside the orbit of Venus. You may have heard people bragging about the fact they can see it with binoculars. In the coming week it will be easier to spot for amateurs as it will be right by the constellation of Virgo, next to the bright star Spica. You’ll need to get up before sunrise to see it though.
In fact November has proved to be quite fruitful and there are currently 4 comets visible to amateur astronomers in the night sky.
So what makes ISON more popular and the most talked about comet of the lot, in fact, the most talked about comet of 2013?
Well, if he survives his journey around the sun we are in for a treat. ISON is predicted to be bright, particularly handsome and visible to the naked eye, maybe even in daylight. Oh la la.
I know. Amazing.
(Image courtesy of http://giphy.com)
Now that ISON is approaching the sun, his icy body has begun to melt and vaporise (along with loads of juicy gossip from the beginning of time) and we can see the tail that comets are so famous for. Did you know comet tails can be as long as the distance between the Earth and the Sun?! (That’s the same as 1AU or Astronomical Unit, in case you need to know).
Another taily tidbit: The tail of a comet always points away from the sun, so after a comet goes around the sun, it actually travels tail first.
So there you have it.
Let’s hope ISON survives his trip being the daredevil, sun-grazer that he is. This is his first shot at it, so we have no idea how he’ll cope but let’s keep our fingers crossed and our eyes peeled in December for an extra special Christmas gift– he’ll certainly have been on one heck of a journey.