Friday, November 29, 2013


UPDATE: 10:00 UT

It is clear that a part (reduced or fragment) of the nucleus of Comet ISON made it round the sun and is now moving away from the sun. After initally brightening and reforming a dust tail derived from its momentum as it swung around the sun, it seems to be fading now as it moves towards the outer FOV of the Lasco C3 camera of the SOHO observatory. The tail is gradually swinging around to the outbound direction. It will be interesting to see what the mission scientists can gleen from this from the multitude of data sets.

For now my rule of thumb, is really not very sciency, but if a naked eye comet reaches the Lasco C3 FOV - its going round! Not a lot of math in that, but its two from two in 3 years! Seriously though for the real science - read NASA's Comet ISON observing campaign blog which is being regularly updated by respected comet supremo Karl Battams.

UPDATE: 05:30 UT

ISON continues to brighten and a new dust tail appears to be swinging around from its transit path towards its outbound trajectory.

Image Credit: Solar and Heliospheric Observatory - Lasco C3 23:30 UT 28/11/2013

What we know about comets is alot more than we used to know, but not everything there is to know!

Like most people with a passing interest in astronomy I have been following the passage of Comet ISON as it approached perihelion. I have followed the intense debates about what might constitute a "secular light curve" and observed daily predictions and alerts about what was about to happen.

Today it has been hilarious to see people pronounce ISON dead on arrival at perihelion and wander off to their thanksgiving dinner thinking its all over red rover!

Currently twitter is ablaze with witty retorts and updates as some sort of remenant has re-emerged and continues to brighten. Most of the wise observers are doing the appropriate thing and "waiting for more information". So far on twitter it has been re-named Schrodinger's Comet, Schwartzneger's "I'll be back" comet.

Image Credit: Solar and Heliospheric Observatory - Lasco C2

As for me, I am reminded of Comet Lovejoy (2011) which surprised everyone and made it past perihelion and broke up outbound after a spectacular display at Christmas 2011. I couldn't help remembering that the tail didn't really return immediately after perhelion, until the Comet moved away from the immediate vicintiy of the Sun. In fact in 2011 Lovejoy's tail didn't really reform until it was even further out than it is now.

One thing to consider here is that the perspective from which we view these images is only two dimentional, ie whats in the image, and its very hard to tell from that perspective what at the front or behind.

Image credit: Comet Lovejoy (2011) Solar and Heliospheric Observatory - Lasco C3

Whilst comets are not made of sugar, think of creme brulee, the sugar gets heated up, some smoke comes off, it suffers intense heat, changes its composition and comes out the otherside a crunchy piece of toffee with roughly its same mass but slightly different texture. Now this is a bit of a stretch scientifically as I said, as comets are not made of sugar, but with the heat, the increase in speed, the change of direction, the resultant slowing and cooling after perihelion, there is alot going on there that we really just don't know enough about.

Which is why comets are, always have been, and always will be, incredibly undpredicatable.

Saturday, November 16, 2013

Comet C/2013 R1 (Lovejoy)

Comet Lovejoy is determined not to be outdone by Comet ISON. However, reports circulating through social media this morning that Comet ISON has now reached magnitude 4, will make sure it has more work to do - as if comets had opinions anyway.

Comet Lovejoy continues to brighten and its ion and dust tails continue to grow. It's coma is a massive 3.7 arcmins now in a 180sec image, which is probably closer to 2 arcmins in reality as the movement probably overstates it a little. It is very hard to make a magnitude estimate now from CCD images. Magnitude estimates are now best made by binocular observations and comparing the brightness with the known brightness of nearby stars. Comet ISON is now a naked eye object. Lovejoy, I suspect is not far away either.

The encroaching moonlight was not very kind to last night's attempt to capture a nice shot. Early this week Rolando Lingusti took a brilliant shot of Comet Lovejoy that was featured in Tony Flander's article in Sky and Telescope.

Comet Lovejoy was discovered by Australia's talented and "best practice" comet hunter Terry Lovejoy, who was a speaker at this year's Advanced Astro Imaging Conference on the Gold Coast. As a keynote speaker he outlined his search methods, which were, I have to say very comprehensive and methodical. Catching two brilliant Christmas Comets in three years is not a fluke, its through sheer hardwork and relentless persuit of what the Oort Cloud throws up each year.

Image Credit: P.Lake 3 x 180sec R,G,B T11

I found it a bit easier to observe the details in the tail in the individual subframes Luminance channel, which I didn't use in the R,G,B image as I ws getting too much light to manage with the intruding moonlight.

Image Credit: P.Lake 180 sec Luminance T11

I refered to Comet Lovejoy as the "one wood" comet (golf club) earlier this week in reference to its slightly out of shape coma. This can be mainly attributable to the fast speed of the Comet travelling at 9 arcsecs per minute in a direction of about 35 degrees across the line of its tail. Its pretty hard to pull up that speed at 0.81 arsces per pixel

Sunday, November 3, 2013

Comet C/2013 A1 (Siding Spring) November Update!

Comet Siding Spring continues on its merry way.

Currently overshadowed a little by the 2012 comets, ISON, Lovejoy, Linear 2012 X1 and Enke all feature this month in the northern skies. Siding Spring will have to wait till next year for its fanfare as it does a very close approach to Mars just after the MAVEN space mission arrives to sample Mars atmosphere.

None the less - Comet 2013 A1 (Siding Spring) is again high in the southern skies after midnight. These images are stacked in groups of 6 for the movement of the Comet to get a nice tight coma for astrometry.

All the scopes haev been very busy chasing the morning comets so I thought tonight after I collected my 2013 TV135 data for MPC, I'd jump onto T31 at Siding Spring and chase it's namesake comet.



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