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## Watch out for comet Lovejoy (C/2014 Q2)

This Saturday morning (the 10th) I will be on the BBC talking about comet Lovejoy, which is currently visible to the naked eye. This comet, more correctly known as C/2014 Q2, was discovered on the 17th of August last year by Terry Lovejoy. According to wikipedia, this is the 5th comet discovered by Lovejoy and he discovered it using a 0.2m Schmidt-Cassegrain telescope, which is not a particularly large telescope.

Comet C/2014 Q2 is just passing from the not very well-known constellation Eridanus (which is just to the South-West of the much better-known constellation Orion) into the constellation Taurus. Tomorrow (the 9th of January) it will cross the celestial equator, and so moves into the northern-half of the sky making it more visible to observers in the Northern Hemisphere. Below is a chart of its motion through the constellations between December of last year and January of this year. According to the comet’s ephemeris, it will pass from Taurus into Aries on the 22nd of January, and into Andromeda at the beginning of February.

The path of comet Lovejoy through the night-time sky from December to February. It is currently moving from the constellation Eridanus into the constellation Taurus and is now best seen from the Northern Hemisphere.

C/2014 Q2 is a long-period comet, it has been calculated that its period is about 11,000 years! Unlike short-period comets which come from the Kupier belt, such long-period comets come from the Oort cloud. I mentioned the Oort cloud, which has never been directly observed, in this blog here. As the diagram I showed there illustrates, it is believed to be a spherical cloud many thousands of Astronomical Units (AUs) away from the Sun, and hence comets from it can come into the Solar System at any angle. Comet C/2014 Q2 is coming in at a very steep angle to the Solar System, some $80^{\circ}$. The comet was at its closest to the Earth yesterday (the 7th of January), when its distance from us was only 0.47 AUs, just under half the distance from the Earth to the Sun. It will reach perihelion (its closest to the Sun) on the 30th of January, when it will be 1.3 AUs from the Sun.

Comet Lovejoy is a long-period comet, which means it comes from the Oort cloud rather than the Kuiper belt. Its orbit is highly inclined to the plane of the Solar system, at an angle of some $80^{\circ}$.

Comet Lovejoy should be visible to the naked eye over the next week or two, even if you don’t happen to live in a rural location. It should be at its brightest over the next week to ten days, reaching a peak brightness of nearly 4th magnitude, and remaining brighter than 5th magnitude until the end of January. As its location in the sky is so easy to find (you just need to find Orion and then – as seen from the Northern Hemisphere – go up and to the right from there), it should be a rare opportunity to see a naked-eye comet. So, make the most of these long winter nights and try to spot this comet in the evening sky!

## Comet ISON update

I was on the S4C programme “Heno” talking about Comet ISON on the 26th of November, just two days before its perihelion (closest approach to the Sun). I was the studio guest, so I appeared on the programme right at the beginning, then at about 8 minutes into the programme, and finally at the end. Here is the entire programme with subtitles (if you can bear it).

Here is an edited version, with just the parts of the programme where I appear :

It would seem comet ISON did not survive its passage around the Sun. All the evidence suggests that ISON broke up as it came within about 1.5 million km of the Sun, probably due to the nucleus of the comet being broken up by a combination of the heat of the Sun and the extreme tidal forces due to the Sun’s gravity. Here is a link to images of ISON at the time of its perihelion taken by the NASA Stereo Probes’ (which are in space observing the Sun)

The latest efforts now concentrate on trying to find ISON’s remnants and to understand in more detail what happened to the comet. You can read more about this in this story.

So, sadly, we did not get the spectacular cometary display in early December that many had been hoping for. But, that is the nature of comets, and part of their fascination. One never knows how they are going to turn out, they are very unpredictable and often surprise us. ISON proved ultimately to be a disappointment, but already there are other comets that astronomers have their sights on which may come and light up our skies over the next few months, such as Comet Lovejoy.