Here attached is an updated montage of the last 2 weeks of this comet's
life.

Enjoy,
Richard Miles

----- Original Message -----
From: "Richard Miles" <rmiles.btee@btinternet.com>
To: <baa-comet@simplelists.com>
Sent: Saturday, May 16, 2020 5:26 PM
Subject: Re: [BAA Comets] C/2019 Y4 (ATLAS) sudden brightening

> Nick,
>
> Can you update your plot?
>
> It looks like another disruption event occurred on 2020 May 08.1±0.3 that
> ejected a cloud of debris sunwards at speeds of about 50-100 m/s. Such an
> energetic event must have involved considerable force / internal pressure
> so
> the nucleus may very well have broken up. Eight days later, the nuclear
> magnitude has faded by about 60%.
>
> Images attached.
>
> The timing fits in perfectly with your attached email from a week ago!
>
> Richard
>
> ----- Original Message -----
> From: "Nick James" <ndj@nickdjames.com>
> To: <baa-comet@simplelists.com>
> Sent: Saturday, May 09, 2020 8:35 AM
> Subject: [BAA Comets] C/2019 Y4 (ATLAS) sudden brightening
>
>
>> Morning everyone,
>>
>> Up until yesterday the central region (11 arcsec radius) of C/2019 Y4
>> has been brightening at around 0.05 mag per day but last night it had
>> jumped by a whole magnitude compared to the night before (May 7.9 vs May
>> 8.9). The attached plot is from my astrometry with a 0.28-m, f/10 SCT in
>> Chelmsford.
>>
>> Terry Lovejoy, via the CometWatch FB group, reports a similar sudden
>> increase between May 8.12 and May 9.12 using the iTelescope T11 system
>> in New Mexico.
>>
>> With all the excitement over C/2020 F8 (SWAN) please remember to keep
>> observing Y4 for as long as you can.
>>
>> Nick.
>>
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>