Comet C/2014 Q2 (Lovejoy) has been photographed many times, by both professional and amateur astronomers, over the last couple of months as it brightens in the sun’s glare and forms a tail – this is caused by the solar wind warming the surface of the comet and turning its ice into a gas which streams behind the core (or nucleus) along with dust caught in that surface ice. Think of a snowball in front of a hairdryer!
The fantastic image at the top of this page, by Austrian astrophotographer Gerald Rhemann, shows perfectly how volatiles like water and carbon dioxide ice vent from the comet in the sun’s glare and stream away behind it. But a DSLR camera on an amateur telescope will allow you to take images of the comet like this one from astrophotographer Damien Phillips:
This most recent visitor from the outer reaches of the solar system continues its journey towards our parent star and reaches perihelion – its closest point to the sun – on 30th January, which in this comet’s case is 1.3 times the distance from the Earth to the sun, or 120 million miles. That means it's in a prime position right now to observe or photograph. Unlike the last comet to grab the headlines, Comet ISON, this one won’t get close enough to break up and we should be able to watch it with binoculars and telescopes as it races back out of the inner solar system during late winter and spring.
From now until 30th we can expect Lovejoy to develop a larger coma (fuzzy atmosphere around the nucleus) and tail. We can also expect it to become naked eye visible in darks skies between 8th and 30th January. You will most likely only see it as a faint and blurry star with the naked eye – but you will have seen a ball of ice from the theoretical Oort Cloud, a ring of comets at the far edge of our solar system, 30 times further from the sun than Pluto! In binoculars you should see a bright core and a diffuse ‘atmosphere’ or coma. A camera on a tripod will let you take images like this by UK astrophotographer Wendy Clark:
Gravity dominates the world of comets. It’s thought that long period comets, like Lovejoy, orbit quite happily in the aforementioned Oort Cloud, a quarter of the way to the next star system for millions of years. These are very stable orbits because space is big and, unlike science fiction movie depictions of the asteroid belt, comets in the Oort Cloud and asteroids in the asteroid belt are so far apart that they will go millions of years before a single collision – if at all.
But if there is a collision between two of the millions of comets suspected to be sitting in the Oort Cloud, one or both may find their stable orbit becomes elliptical and sends them in towards the sun. This journey will take many thousands of miles. In the case of C/2014 Q2 Lovejoy, it takes 14,234 years to complete one orbit (Earth taking just one year).
Due to gravitational disturbances on its way into the inner solar system – most noticeably the little tugs it gets from the ice giant planets, Neptune & Uranus, and the gas giant planets, Saturn & Jupiter, it’s orbital ellipse has already changed again. By the time the dominant gravitational pull of the sun has influenced the comet’s orbit as it swings around the sun, Lovejoy will no longer take 14,234 years to complete its next orbit, but 8,000.
But currently, Comet Lovejoy is accelerating as it gets ever closer to the sun at some 36 kilometres per second! Its closest point to Earth was on 7th January at 43.6 million miles but, as it’s still hurtling towards the sun it’s still brightening. The trade off between being closest to Earth on 7th January and closest to the source of it’s light (reflected star light from our sun) on 30th January means that it will appear at its brightest to us on Earth on the nights of 13th, 14th and 15th January 2015.
Here’s our guide to observing or taking images of this comet. Go out and take a look if you can. This is our only opportunity as comet C/2014 Q2 (Lovejoy) won’t be back in view again for another 8,000 years!