Topics

C/2019 Y4 ATLAS brightening rapidly

Michael Mattiazzo
 

Hi Folks,

 

C/2019 Y4 ATLAS appears to be brightening rapidly.

Image attached taken remotely on 2020 Feb 18 at 09:20UT.

Large aperture photometric V magnitude = 12.5

Coma diameter 4'

This comet has the potential to become seriously bright when 0.25AU from the Sun in late May 2020.

It will need to be since it will also lie very close to the Sun from our perspective at this time.

More observations are needed, especially visual attempts, so we can predict its peak brightness with more confidence.

The rapid brightening can be explained by its history. Typical behaviour from a long period, small perihelion object.

The nucleus has already been baked by the Sun at its previous encounter 5,000+ years ago when presumably a much larger comet broke into at least 2 pieces, that later return as great comet C/1844 Y1 and C/2019 Y4.

Stripped of volatiles, it has only become active now at 2.1AU when crossing the ice line.

I wonder if there are any more members to follow.

 

Cheers,

Michael Mattiazzo

 

Bob King
 

Hi Michael,
Thanks for sharing your image and information. I looked at this comet two nights ago from a dark sky with a 38-cm reflector and it was not brighter than 14.0. I strongly suspected a 20-30 arc-second coma with averted vision (Feb . 17.1 UT).

Best regards,
Bob 



On Feb 18, 2020, at 5:36 AM, Michael Mattiazzo <mmatti@...> wrote:

Hi Folks,

 

C/2019 Y4 ATLAS appears to be brightening rapidly.

Image attached taken remotely on 2020 Feb 18 at 09:20UT.

Large aperture photometric V magnitude = 12.5

Coma diameter 4'

This comet has the potential to become seriously bright when 0.25AU from the Sun in late May 2020.

It will need to be since it will also lie very close to the Sun from our perspective at this time.

More observations are needed, especially visual attempts, so we can predict its peak brightness with more confidence.

The rapid brightening can be explained by its history. Typical behaviour from a long period, small perihelion object.

The nucleus has already been baked by the Sun at its previous encounter 5,000+ years ago when presumably a much larger comet broke into at least 2 pieces, that later return as great comet C/1844 Y1 and C/2019 Y4.

Stripped of volatiles, it has only become active now at 2.1AU when crossing the ice line.

I wonder if there are any more members to follow.

 

Cheers,

Michael Mattiazzo

 

<2019y4_20200218_mmatti1.jpg>

Sección Cometas Liada
 

Hi

we request to publish

 

C/2019 Y4 (ATLAS)

2020 Feb. 18.39 UT: m1=12.5 CCD, Dia.=4', ... 28-cm SCT + CCD ... Michael Mattiazzo (T68 New Mexico remotly, Australia)

 

https://cometobservationsdatabase.wordpress.com/

 

 

 

De: Michael Mattiazzo
Enviado: martes, 18 de febrero de 2020 08:36
Para: comets-ml@groups.io
Asunto: [comets-ml] C/2019 Y4 ATLAS brightening rapidly

 

Hi Folks,

 

C/2019 Y4 ATLAS appears to be brightening rapidly.

Image attached taken remotely on 2020 Feb 18 at 09:20UT.

Large aperture photometric V magnitude = 12.5

Coma diameter 4'

This comet has the potential to become seriously bright when 0.25AU from the Sun in late May 2020.

It will need to be since it will also lie very close to the Sun from our perspective at this time.

More observations are needed, especially visual attempts, so we can predict its peak brightness with more confidence.

The rapid brightening can be explained by its history. Typical behaviour from a long period, small perihelion object.

The nucleus has already been baked by the Sun at its previous encounter 5,000+ years ago when presumably a much larger comet broke into at least 2 pieces, that later return as great comet C/1844 Y1 and C/2019 Y4.

Stripped of volatiles, it has only become active now at 2.1AU when crossing the ice line.

I wonder if there are any more members to follow.

 

Cheers,

Michael Mattiazzo

 

 

Bob King
 

Helpful details, Michael. Thanks!
Bob

On Feb 18, 2020, at 6:56 AM, Sección Cometas Liada <cometas.liada@...> wrote:

Hi

we request to publish

 

C/2019 Y4 (ATLAS)

2020 Feb. 18.39 UT: m1=12.5 CCD, Dia.=4', ... 28-cm SCT + CCD ... Michael Mattiazzo (T68 New Mexico remotly, Australia)

 

https://cometobservationsdatabase.wordpress.com/

 

 

 

De: Michael Mattiazzo
Enviado: martes, 18 de febrero de 2020 08:36
Para: comets-ml@groups.io
Asunto: [comets-ml] C/2019 Y4 ATLAS brightening rapidly

 

Hi Folks,

 

C/2019 Y4 ATLAS appears to be brightening rapidly.

Image attached taken remotely on 2020 Feb 18 at 09:20UT.

Large aperture photometric V magnitude = 12.5

Coma diameter 4'

This comet has the potential to become seriously bright when 0.25AU from the Sun in late May 2020.

It will need to be since it will also lie very close to the Sun from our perspective at this time.

More observations are needed, especially visual attempts, so we can predict its peak brightness with more confidence.

The rapid brightening can be explained by its history. Typical behaviour from a long period, small perihelion object.

The nucleus has already been baked by the Sun at its previous encounter 5,000+ years ago when presumably a much larger comet broke into at least 2 pieces, that later return as great comet C/1844 Y1 and C/2019 Y4.

Stripped of volatiles, it has only become active now at 2.1AU when crossing the ice line.

I wonder if there are any more members to follow.

 

Cheers,

Michael Mattiazzo

 

 

michaeljaeger
 

Hello Bob and Michael
It should be a gas rich comet. The outer coma is still visually weak, but could change quickly. An exciting comet. For us here in Austria, it is well placed before perihelion.
Michael

------ Originalnachricht ------
Von: "Bob King" <nightsky55@...>
Gesendet: 18.02.2020 14:45:06
Betreff: Re: [comets-ml] C/2019 Y4 ATLAS brightening rapidly

Helpful details, Michael. Thanks!
Bob

On Feb 18, 2020, at 6:56 AM, Sección Cometas Liada <cometas.liada@...> wrote:

Hi

we request to publish

 

C/2019 Y4 (ATLAS)

2020 Feb. 18.39 UT: m1=12.5 CCD, Dia.=4', ... 28-cm SCT + CCD ... Michael Mattiazzo (T68 New Mexico remotly, Australia)

 

https://cometobservationsdatabase.wordpress.com/

 

 

 

De: Michael Mattiazzo
Enviado: martes, 18 de febrero de 2020 08:36
Para: comets-ml@groups.io
Asunto: [comets-ml] C/2019 Y4 ATLAS brightening rapidly

 

Hi Folks,

 

C/2019 Y4 ATLAS appears to be brightening rapidly.

Image attached taken remotely on 2020 Feb 18 at 09:20UT.

Large aperture photometric V magnitude = 12.5

Coma diameter 4'

This comet has the potential to become seriously bright when 0.25AU from the Sun in late May 2020.

It will need to be since it will also lie very close to the Sun from our perspective at this time.

More observations are needed, especially visual attempts, so we can predict its peak brightness with more confidence.

The rapid brightening can be explained by its history. Typical behaviour from a long period, small perihelion object.

The nucleus has already been baked by the Sun at its previous encounter 5,000+ years ago when presumably a much larger comet broke into at least 2 pieces, that later return as great comet C/1844 Y1 and C/2019 Y4.

Stripped of volatiles, it has only become active now at 2.1AU when crossing the ice line.

I wonder if there are any more members to follow.

 

Cheers,

Michael Mattiazzo

 

 

Bob King
 

That could be it, Michael J. I may only have seen the innermost coma.
Bob



On Feb 18, 2020, at 9:03 AM, michaeljaeger <michaeljaeger@...> wrote:

Hello Bob and Michael
It should be a gas rich comet. The outer coma is still visually weak, but could change quickly. An exciting comet. For us here in Austria, it is well placed before perihelion.
Michael

------ Originalnachricht ------
Von: "Bob King" <nightsky55@...>
Gesendet: 18.02.2020 14:45:06
Betreff: Re: [comets-ml] C/2019 Y4 ATLAS brightening rapidly

Helpful details, Michael. Thanks!
Bob

On Feb 18, 2020, at 6:56 AM, Sección Cometas Liada <cometas.liada@...> wrote:

Hi

we request to publish

 

C/2019 Y4 (ATLAS)

2020 Feb. 18.39 UT: m1=12.5 CCD, Dia.=4', ... 28-cm SCT + CCD ... Michael Mattiazzo (T68 New Mexico remotly, Australia)

 

https://cometobservationsdatabase.wordpress.com/

 

 

 

De: Michael Mattiazzo
Enviado: martes, 18 de febrero de 2020 08:36
Para: comets-ml@groups.io
Asunto: [comets-ml] C/2019 Y4 ATLAS brightening rapidly

 

Hi Folks,

 

C/2019 Y4 ATLAS appears to be brightening rapidly.

Image attached taken remotely on 2020 Feb 18 at 09:20UT.

Large aperture photometric V magnitude = 12.5

Coma diameter 4'

This comet has the potential to become seriously bright when 0.25AU from the Sun in late May 2020.

It will need to be since it will also lie very close to the Sun from our perspective at this time.

More observations are needed, especially visual attempts, so we can predict its peak brightness with more confidence.

The rapid brightening can be explained by its history. Typical behaviour from a long period, small perihelion object.

The nucleus has already been baked by the Sun at its previous encounter 5,000+ years ago when presumably a much larger comet broke into at least 2 pieces, that later return as great comet C/1844 Y1 and C/2019 Y4.

Stripped of volatiles, it has only become active now at 2.1AU when crossing the ice line.

I wonder if there are any more members to follow.

 

Cheers,

Michael Mattiazzo

 

 

Tavcso.hu
 

Let me share my recent visual observation:
 
C/2019 Y4 (ATLAS)
2020 Feb. 18.81 UT: m1=14.7, Dia.=0.5', DC=4... 60.0cm L f/4 (305x)
The comet is easy with averted vision. Motion is seen in 30 min obsetvation.
 
Sandor Szabo
 

From: Bob King
Sent: Tuesday, February 18, 2020 6:25 PM
Subject: Re: [comets-ml] C/2019 Y4 ATLAS brightening rapidly
 
That could be it, Michael J. I may only have seen the innermost coma.
Bob

 

On Feb 18, 2020, at 9:03 AM, michaeljaeger <michaeljaeger@...> wrote:

Hello Bob and Michael
It should be a gas rich comet. The outer coma is still visually weak, but could change quickly. An exciting comet. For us here in Austria, it is well placed before perihelion.
Michael
 
------ Originalnachricht ------
Von: "Bob King" <nightsky55@...>
Gesendet: 18.02.2020 14:45:06
Betreff: Re: [comets-ml] C/2019 Y4 ATLAS brightening rapidly
 
Helpful details, Michael. Thanks!
Bob

On Feb 18, 2020, at 6:56 AM, Sección Cometas Liada <cometas.liada@...> wrote:

Hi

we request to publish

 

C/2019 Y4 (ATLAS)

2020 Feb. 18.39 UT: m1=12.5 CCD, Dia.=4', ... 28-cm SCT + CCD ... Michael Mattiazzo (T68 New Mexico remotly, Australia)

 

https://cometobservationsdatabase.wordpress.com/

 

 

 

De: Michael Mattiazzo
Enviado: martes, 18 de febrero de 2020 08:36
Para: comets-ml@groups.io
Asunto: [comets-ml] C/2019 Y4 ATLAS brightening rapidly

 

Hi Folks,

 

C/2019 Y4 ATLAS appears to be brightening rapidly.

Image attached taken remotely on 2020 Feb 18 at 09:20UT.

Large aperture photometric V magnitude = 12.5

Coma diameter 4'

This comet has the potential to become seriously bright when 0.25AU from the Sun in late May 2020.

It will need to be since it will also lie very close to the Sun from our perspective at this time.

More observations are needed, especially visual attempts, so we can predict its peak brightness with more confidence.

The rapid brightening can be explained by its history. Typical behaviour from a long period, small perihelion object.

The nucleus has already been baked by the Sun at its previous encounter 5,000+ years ago when presumably a much larger comet broke into at least 2 pieces, that later return as great comet C/1844 Y1 and C/2019 Y4.

Stripped of volatiles, it has only become active now at 2.1AU when crossing the ice line.

I wonder if there are any more members to follow.

 

Cheers,

Michael Mattiazzo

 

 

Thomas Lehmann
 

I managed to image the comet the night before yesterday remotely from
New Mexico (iTelescope.net, T11) using CCD and green filter The coma appears
to be really huge, with the fainter parts reaching almost 10' in diameter!

Results from large aperture photometry (APASS, V):
2020 02 17.28, m1=12.2mag, aperture diam. 8.6'

Exciting object, definitely.
Clear skies,
Thomas

Am Tue, 18 Feb 2020 21:07:01 +0100
schrieb "Tavcso.hu" <info@...>:

Let me share my recent visual observation:

C/2019 Y4 (ATLAS)
2020 Feb. 18.81 UT: m1=14.7, Dia.=0.5', DC=4... 60.0cm L f/4 (305x)
The comet is easy with averted vision. Motion is seen in 30 min obsetvation.

Sandor Szabo

From: Bob King
Sent: Tuesday, February 18, 2020 6:25 PM
To: comets-ml@groups.io
Subject: Re: [comets-ml] C/2019 Y4 ATLAS brightening rapidly

That could be it, Michael J. I may only have seen the innermost coma.
Bob




On Feb 18, 2020, at 9:03 AM, michaeljaeger <michaeljaeger@...> wrote:


Hello Bob and Michael
It should be a gas rich comet. The outer coma is still visually weak, but could change quickly. An exciting comet. For us here in Austria, it is well placed before perihelion.
Michael

------ Originalnachricht ------
Von: "Bob King" <nightsky55@...>
An: comets-ml@groups.io
Gesendet: 18.02.2020 14:45:06
Betreff: Re: [comets-ml] C/2019 Y4 ATLAS brightening rapidly

Helpful details, Michael. Thanks!
Bob


On Feb 18, 2020, at 6:56 AM, Sección Cometas Liada <cometas.liada@...> wrote:


Hi

we request to publish



C/2019 Y4 (ATLAS)

2020 Feb. 18.39 UT: m1=12.5 CCD, Dia.=4', ... 28-cm SCT + CCD ... Michael Mattiazzo (T68 New Mexico remotly, Australia)



https://cometobservationsdatabase.wordpress.com/







De: Michael Mattiazzo
Enviado: martes, 18 de febrero de 2020 08:36
Para: comets-ml@groups.io
Asunto: [comets-ml] C/2019 Y4 ATLAS brightening rapidly



Hi Folks,



C/2019 Y4 ATLAS appears to be brightening rapidly.

Image attached taken remotely on 2020 Feb 18 at 09:20UT.

Large aperture photometric V magnitude = 12.5

Coma diameter 4'

This comet has the potential to become seriously bright when 0.25AU from the Sun in late May 2020.

It will need to be since it will also lie very close to the Sun from our perspective at this time.

More observations are needed, especially visual attempts, so we can predict its peak brightness with more confidence.

The rapid brightening can be explained by its history. Typical behaviour from a long period, small perihelion object.

The nucleus has already been baked by the Sun at its previous encounter 5,000+ years ago when presumably a much larger comet broke into at least 2 pieces, that later return as great comet C/1844 Y1 and C/2019 Y4.

Stripped of volatiles, it has only become active now at 2.1AU when crossing the ice line.

I wonder if there are any more members to follow.



Cheers,

Michael Mattiazzo








Tavcso.hu
 

I made another attempt some hours later when the comet is higher:

C/2019 Y4 (ATLAS)
2020 Feb. 18.93 UT: m1=14.4, Dia.=0.7', DC=3... 60.0cm L f/4 (305x)

Sandor

----- Eredeti üzenet -----
From: Thomas Lehmann
Sent: Tuesday, February 18, 2020 11:38 PM
To: comets-ml@groups.io
Subject: Re: [comets-ml] C/2019 Y4 ATLAS brightening rapidly


I managed to image the comet the night before yesterday remotely from
New Mexico (iTelescope.net, T11) using CCD and green filter The coma appears
to be really huge, with the fainter parts reaching almost 10' in diameter!

Results from large aperture photometry (APASS, V):
2020 02 17.28, m1=12.2mag, aperture diam. 8.6'

Exciting object, definitely.
Clear skies,
Thomas


Am Tue, 18 Feb 2020 21:07:01 +0100
schrieb "Tavcso.hu" <info@...>:

Let me share my recent visual observation:

C/2019 Y4 (ATLAS)
2020 Feb. 18.81 UT: m1=14.7, Dia.=0.5', DC=4... 60.0cm L f/4 (305x)
The comet is easy with averted vision. Motion is seen in 30 min obsetvation.

Sandor Szabo

From: Bob King
Sent: Tuesday, February 18, 2020 6:25 PM
To: comets-ml@groups.io
Subject: Re: [comets-ml] C/2019 Y4 ATLAS brightening rapidly

That could be it, Michael J. I may only have seen the innermost coma.
Bob




On Feb 18, 2020, at 9:03 AM, michaeljaeger <michaeljaeger@...> wrote:


Hello Bob and Michael
It should be a gas rich comet. The outer coma is still visually weak, but could change quickly. An exciting comet. For us here in Austria, it is well placed before perihelion.
Michael

------ Originalnachricht ------
Von: "Bob King" <nightsky55@...>
An: comets-ml@groups.io
Gesendet: 18.02.2020 14:45:06
Betreff: Re: [comets-ml] C/2019 Y4 ATLAS brightening rapidly

Helpful details, Michael. Thanks!
Bob


On Feb 18, 2020, at 6:56 AM, Sección Cometas Liada <cometas.liada@...> wrote:


Hi

we request to publish



C/2019 Y4 (ATLAS)

2020 Feb. 18.39 UT: m1=12.5 CCD, Dia.=4', ... 28-cm SCT + CCD ... Michael Mattiazzo (T68 New Mexico remotly, Australia)



https://cometobservationsdatabase.wordpress.com/







De: Michael Mattiazzo
Enviado: martes, 18 de febrero de 2020 08:36
Para: comets-ml@groups.io
Asunto: [comets-ml] C/2019 Y4 ATLAS brightening rapidly



Hi Folks,



C/2019 Y4 ATLAS appears to be brightening rapidly.

Image attached taken remotely on 2020 Feb 18 at 09:20UT.

Large aperture photometric V magnitude = 12.5

Coma diameter 4'

This comet has the potential to become seriously bright when 0.25AU from the Sun in late May 2020.

It will need to be since it will also lie very close to the Sun from our perspective at this time.

More observations are needed, especially visual attempts, so we can predict its peak brightness with more confidence.

The rapid brightening can be explained by its history. Typical behaviour from a long period, small perihelion object.

The nucleus has already been baked by the Sun at its previous encounter 5,000+ years ago when presumably a much larger comet broke into at least 2 pieces, that later return as great comet C/1844 Y1 and C/2019 Y4.

Stripped of volatiles, it has only become active now at 2.1AU when crossing the ice line.

I wonder if there are any more members to follow.



Cheers,

Michael Mattiazzo








David Seargent
 

It may mean nothing, but C/1844 Y1 may also have been a "late bloomer". Given the comet's magnitude in late December 1844/January 1845, it would seem that it should have been a pretty easy object for telescopic discovery in the northern morning skies several weeks pre-perihelion. I'm not implying that Y4 will be a replay of 1844 (though that would be nice!!) but the two objects might follow similar brightness trends. 

David



----- Original Message -----
From:
comets-ml@groups.io

To:
<comets-ml@groups.io>
Cc:

Sent:
Wed, 19 Feb 2020 00:03:38 +0100
Subject:
Re: [comets-ml] C/2019 Y4 ATLAS brightening rapidly


I made another attempt some hours later when the comet is higher:

C/2019 Y4 (ATLAS)
2020 Feb. 18.93 UT: m1=14.4, Dia.=0.7', DC=3... 60.0cm L f/4 (305x)

Sandor

----- Eredeti üzenet -----
From: Thomas Lehmann
Sent: Tuesday, February 18, 2020 11:38 PM
To: comets-ml@groups.io
Subject: Re: [comets-ml] C/2019 Y4 ATLAS brightening rapidly


I managed to image the comet the night before yesterday remotely from
New Mexico (iTelescope.net, T11) using CCD and green filter The coma appears
to be really huge, with the fainter parts reaching almost 10' in diameter!

Results from large aperture photometry (APASS, V):
2020 02 17.28, m1=12.2mag, aperture diam. 8.6'

Exciting object, definitely.
Clear skies,
Thomas


> Am Tue, 18 Feb 2020 21:07:01 +0100
> schrieb "Tavcso.hu" <info@...>:
>
> Let me share my recent visual observation:
>
> C/2019 Y4 (ATLAS)
> 2020 Feb. 18.81 UT: m1=14.7, Dia.=0.5', DC=4... 60.0cm L f/4 (305x)
> The comet is easy with averted vision. Motion is seen in 30 min
> obsetvation.
>
> Sandor Szabo
>
> From: Bob King
> Sent: Tuesday, February 18, 2020 6:25 PM
> To: comets-ml@groups.io
> Subject: Re: [comets-ml] C/2019 Y4 ATLAS brightening rapidly
>
> That could be it, Michael J. I may only have seen the innermost coma.
> Bob
>
>
>
>
> On Feb 18, 2020, at 9:03 AM, michaeljaeger <michaeljaeger@gmxat> wrote:
>
>
> Hello Bob and Michael
> It should be a gas rich comet. The outer coma is still visually weak,
> but could change quickly. An exciting comet. For us here in Austria, it is
> well placed before perihelion.
> Michael
>
> ------ Originalnachricht ------
> Von: "Bob King" <nightsky55@...>
> An: comets-ml@groups.io
> Gesendet: 18.02.2020 14:45:06
> Betreff: Re: [comets-ml] C/2019 Y4 ATLAS brightening rapidly
>
> Helpful details, Michael. Thanks!
> Bob
>
>
> On Feb 18, 2020, at 6:56 AM, Sección Cometas Liada
> <cometas.liada@...> wrote:
>
>
> Hi
>
> we request to publish
>
>
>
> C/2019 Y4 (ATLAS)
>
> 2020 Feb. 18.39 UT: m1=125 CCD, Dia.=4', ... 28-cm SCT + CCD ...
> Michael Mattiazzo (T68 New Mexico remotly, Australia)
>
>
>
> https://cometobservationsdatabase.wordpress.com/
>
>
>
>
>
>
>
> De: Michael Mattiazzo
> Enviado: martes, 18 de febrero de 2020 08:36
> Para: comets-ml@groups.io
> Asunto: [comets-ml] C/2019 Y4 ATLAS brightening rapidly
>
>
>
> Hi Folks,
>
>
>
> C/2019 Y4 ATLAS appears to be brightening rapidly.
>
> Image attached taken remotely on 2020 Feb 18 at 09:20UT.
>
> Large aperture photometric V magnitude = 12.5
>
> Coma diameter 4'
>
> This comet has the potential to become seriously bright when 0.25AU
> from the Sun in late May 2020.
>
> It will need to be since it will also lie very close to the Sun from
> our perspective at this time.
>
> More observations are needed, especially visual attempts, so we can
> predict its peak brightness with more confidence.
>
> The rapid brightening can be explained by its history. Typical
> behaviour from a long period, small perihelion object.
>
> The nucleus has already been baked by the Sun at its previous
> encounter 5,000+ years ago when presumably a much larger comet broke into
> at least 2 pieces, that later return as great comet C/1844 Y1 and C/2019
> Y4.
>
> Stripped of volatiles, it has only become active now at 2.1AU when
> crossing the ice line.
>
> I wonder if there are any more members to follow.
>
>
>
> Cheers,
>
> Michael Mattiazzo
>
>
>
>
>
>
>
>
>






farnham@...
 

Hi all

I don't want to dampen the excitement for this comet, but I did want to point out the geometric observing conditions, so that people have realistic expectations.  

The appearance of C/1844 Y1 was in a pretty much ideal situation, with the Earth positioned so that closest approach occurred just a few weeks after perihelion, when the comet was ~0.7 AU from the sun and about the time it reappeared after solar conjunction.  Perfect conditions for getting a "great comet".

Unfortunately, the timing of the C/2019 Y4 apparition is offset about 6 months in the Earth's orbit, so the conditions are pretty poor for post-perihelion observing.  The comet won't reappear for ~2 months after perihelion, and then the comet will be ~1 AU from the Sun and almost 2 AU from Earth.  (I've included plots showing the the 2 comets' motion in the co-rotating frame of the Earth.)  Thus, even if C/2019 Y4 exhibits the same activity as C/1844 Y1, it will not appear to be particularly spectacular by the time we can see it after perihelion. 

On the other hand, it is notable that the Earth's closest approach occurs around the time the comet disappears into solar conjunction, so it will be fairly bright at that point.  And it is supposed to appear in the STEREO field of view around perihelion, so that could give us a good show.

Tony


Alan Hale
 

Hi Tony, all,

One other factor to consider is that, as the comet approaches perihelion, it will be at a high phase angle (in excess of 130 degrees). If this comet has a substantial dust content and if it exhibits significant pre-perihelion dust release, there could be some distinct brightening due to forward scattering of sunlight.


Sincerely,
Alan

From: <farnham@...>
Reply-To: <comets-ml@groups.io>
Date: Wed, 19 Feb 2020 08:48:33 -0800
To: <comets-ml@groups.io>
Subject: Re: [comets-ml] C/2019 Y4 ATLAS brightening rapidly

Hi all

I don't want to dampen the excitement for this comet, but I did want to point out the geometric observing conditions, so that people have realistic expectations.  

The appearance of C/1844 Y1 was in a pretty much ideal situation, with the Earth positioned so that closest approach occurred just a few weeks after perihelion, when the comet was ~0.7 AU from the sun and about the time it reappeared after solar conjunction.  Perfect conditions for getting a "great comet".

Unfortunately, the timing of the C/2019 Y4 apparition is offset about 6 months in the Earth's orbit, so the conditions are pretty poor for post-perihelion observing.  The comet won't reappear for ~2 months after perihelion, and then the comet will be ~1 AU from the Sun and almost 2 AU from Earth.  (I've included plots showing the the 2 comets' motion in the co-rotating frame of the Earth.)  Thus, even if C/2019 Y4 exhibits the same activity as C/1844 Y1, it will not appear to be particularly spectacular by the time we can see it after perihelion. 

On the other hand, it is notable that the Earth's closest approach occurs around the time the comet disappears into solar conjunction, so it will be fairly bright at that point.  And it is supposed to appear in the STEREO field of view around perihelion, so that could give us a good show.

Tony


Alan Hale
 

Hi Tony, all,

Another factor to consider . . . 

Since this definitely appears to be a trailing — and, presumably, smaller — fragment of a previously-split comet, it may be a candidate for additional fragmenting, in a manner similar to that of Comet West in 1976. If that were to happen, we may see a significant upsurge in brightness.

On the other hand, it could pull a Comet ISON and disperse away completely.

Fred Whipple: “If you must bet, bet on a horse, not on a comet!”


Sincerely,
Alan

From: Alan <ahale@...>
Reply-To: <comets-ml@groups.io>
Date: Wed, 19 Feb 2020 11:45:28 -0700
To: <comets-ml@groups.io>
Subject: Re: [comets-ml] C/2019 Y4 ATLAS brightening rapidly

Hi Tony, all,

One other factor to consider is that, as the comet approaches perihelion, it will be at a high phase angle (in excess of 130 degrees). If this comet has a substantial dust content and if it exhibits significant pre-perihelion dust release, there could be some distinct brightening due to forward scattering of sunlight.


Sincerely,
Alan

From: <farnham@...>
Reply-To: <comets-ml@groups.io>
Date: Wed, 19 Feb 2020 08:48:33 -0800
To: <comets-ml@groups.io>
Subject: Re: [comets-ml] C/2019 Y4 ATLAS brightening rapidly

Hi all

I don't want to dampen the excitement for this comet, but I did want to point out the geometric observing conditions, so that people have realistic expectations.  

The appearance of C/1844 Y1 was in a pretty much ideal situation, with the Earth positioned so that closest approach occurred just a few weeks after perihelion, when the comet was ~0.7 AU from the sun and about the time it reappeared after solar conjunction.  Perfect conditions for getting a "great comet".

Unfortunately, the timing of the C/2019 Y4 apparition is offset about 6 months in the Earth's orbit, so the conditions are pretty poor for post-perihelion observing.  The comet won't reappear for ~2 months after perihelion, and then the comet will be ~1 AU from the Sun and almost 2 AU from Earth.  (I've included plots showing the the 2 comets' motion in the co-rotating frame of the Earth.)  Thus, even if C/2019 Y4 exhibits the same activity as C/1844 Y1, it will not appear to be particularly spectacular by the time we can see it after perihelion. 

On the other hand, it is notable that the Earth's closest approach occurs around the time the comet disappears into solar conjunction, so it will be fairly bright at that point.  And it is supposed to appear in the STEREO field of view around perihelion, so that could give us a good show.

Tony


Thomas Lehmann
 

Hi Alan,

that's indeed a very good point. Maybe what we currently see is just an outburst
activity due to some - ongoing - fragmentation. We will probably know better in
2-3 weeks ...

Thomas

Am Wed, 19 Feb 2020 12:23:56 -0700
schrieb "Alan Hale" <ahale@...>:

Hi Tony, all,

Another factor to consider . . .

Since this definitely appears to be a trailing ‹ and, presumably, smaller ‹
fragment of a previously-split comet, it may be a candidate for additional
fragmenting, in a manner similar to that of Comet West in 1976. If that were
to happen, we may see a significant upsurge in brightness.

On the other hand, it could pull a Comet ISON and disperse away completely.

Fred Whipple: ³If you must bet, bet on a horse, not on a comet!²


Sincerely,
Alan

From: Alan <ahale@...>
Reply-To: <comets-ml@groups.io>
Date: Wed, 19 Feb 2020 11:45:28 -0700
To: <comets-ml@groups.io>
Subject: Re: [comets-ml] C/2019 Y4 ATLAS brightening rapidly

Hi Tony, all,

One other factor to consider is that, as the comet approaches perihelion, it
will be at a high phase angle (in excess of 130 degrees). If this comet has a
substantial dust content and if it exhibits significant pre-perihelion dust
release, there could be some distinct brightening due to forward scattering of
sunlight.


Sincerely,
Alan

From: <farnham@...>
Reply-To: <comets-ml@groups.io>
Date: Wed, 19 Feb 2020 08:48:33 -0800
To: <comets-ml@groups.io>
Subject: Re: [comets-ml] C/2019 Y4 ATLAS brightening rapidly

Hi all

I don't want to dampen the excitement for this comet, but I did want to point
out the geometric observing conditions, so that people have realistic
expectations.

The appearance of C/1844 Y1 was in a pretty much ideal situation, with the
Earth positioned so that closest approach occurred just a few weeks after
perihelion, when the comet was ~0.7 AU from the sun and about the time it
reappeared after solar conjunction. Perfect conditions for getting a "great
comet".

Unfortunately, the timing of the C/2019 Y4 apparition is offset about 6
months in the Earth's orbit, so the conditions are pretty poor for
post-perihelion observing. The comet won't reappear for ~2 months after
perihelion, and then the comet will be ~1 AU from the Sun and almost 2 AU
from Earth. (I've included plots showing the the 2 comets' motion in the
co-rotating frame of the Earth.) Thus, even if C/2019 Y4 exhibits the same
activity as C/1844 Y1, it will not appear to be particularly spectacular by
the time we can see it after perihelion.

On the other hand, it is notable that the Earth's closest approach occurs
around the time the comet disappears into solar conjunction, so it will be
fairly bright at that point. And it is supposed to appear in the STEREO
field of view around perihelion, so that could give us a good show.

Tony




michaeljaeger
 

so far it doesn't look like an outbreak to me. Photo from February 18, showing tail and coma more clearly - m1 13mag

Kenneth Drake
 

But is not the elongation at that time just 10-13 degrees?

Kenneth Drake Willis, Texas


On 2/19/2020 12:45 PM, Alan Hale wrote:
Hi Tony, all,

One other factor to consider is that, as the comet approaches perihelion, it will be at a high phase angle (in excess of 130 degrees). If this comet has a substantial dust content and if it exhibits significant pre-perihelion dust release, there could be some distinct brightening due to forward scattering of sunlight.


Sincerely,
Alan

From: <farnham@...>
Reply-To: <comets-ml@groups.io>
Date: Wed, 19 Feb 2020 08:48:33 -0800
To: <comets-ml@groups.io>
Subject: Re: [comets-ml] C/2019 Y4 ATLAS brightening rapidly

Hi all

I don't want to dampen the excitement for this comet, but I did want to point out the geometric observing conditions, so that people have realistic expectations.  

The appearance of C/1844 Y1 was in a pretty much ideal situation, with the Earth positioned so that closest approach occurred just a few weeks after perihelion, when the comet was ~0.7 AU from the sun and about the time it reappeared after solar conjunction.  Perfect conditions for getting a "great comet".

Unfortunately, the timing of the C/2019 Y4 apparition is offset about 6 months in the Earth's orbit, so the conditions are pretty poor for post-perihelion observing.  The comet won't reappear for ~2 months after perihelion, and then the comet will be ~1 AU from the Sun and almost 2 AU from Earth.  (I've included plots showing the the 2 comets' motion in the co-rotating frame of the Earth.)  Thus, even if C/2019 Y4 exhibits the same activity as C/1844 Y1, it will not appear to be particularly spectacular by the time we can see it after perihelion. 

On the other hand, it is notable that the Earth's closest approach occurs around the time the comet disappears into solar conjunction, so it will be fairly bright at that point.  And it is supposed to appear in the STEREO field of view around perihelion, so that could give us a good show.

Tony


P. Clay Sherrod
 

We all hope this comet is going to develop, but goodness the conjecture of splitting, fragmenting, exploding and becoming a spectacle.  Brian Marsden told me after Comet Kohoutek he would never go on record as predicting any "interesting activity" of a comet, even if his speculation was certain.  Let us give it time to at least do some of the things that are being speculated upon.
 
Dr. Clay
-------
Arkansas Sky Observatories
www.arksky.org
ASO MPC H45 - Petit Jean Mountain South
ASO MPC H41 - Petit Jean Mountain North
ASO MPC H43 - Conway West
Publications:  http://arksky.org/publications
Join Arkansas Sky Observatories on Facebook
 
 

----- Original Message -----
From: Alan Hale <ahale@...>
Sent: 2/19/2020 1:23:56 PM
Subject: Re: [comets-ml] C/2019 Y4 ATLAS brightening rapidly

Hi Tony, all,

Another factor to consider . . . 

Since this definitely appears to be a trailing — and, presumably, smaller — fragment of a previously-split comet, it may be a candidate for additional fragmenting, in a manner similar to that of Comet West in 1976. If that were to happen, we may see a significant upsurge in brightness.

On the other hand, it could pull a Comet ISON and disperse away completely.

Fred Whipple: “If you must bet, bet on a horse, not on a comet!”


Sincerely,
Alan

From: Alan <ahale@...>
Reply-To: <comets-ml@groups.io>
Date: Wed, 19 Feb 2020 11:45:28 -0700
To: <comets-ml@groups.io>
Subject: Re: [comets-ml] C/2019 Y4 ATLAS brightening rapidly

Hi Tony, all,

One other factor to consider is that, as the comet approaches perihelion, it will be at a high phase angle (in excess of 130 degrees). If this comet has a substantial dust content and if it exhibits significant pre-perihelion dust release, there could be some distinct brightening due to forward scattering of sunlight.


Sincerely,
Alan

From: <farnham@...>
Reply-To: <comets-ml@groups.io>
Date: Wed, 19 Feb 2020 08:48:33 -0800
To: <comets-ml@groups.io>
Subject: Re: [comets-ml] C/2019 Y4 ATLAS brightening rapidly

Hi all

I don't want to dampen the excitement for this comet, but I did want to point out the geometric observing conditions, so that people have realistic expectations.  

The appearance of C/1844 Y1 was in a pretty much ideal situation, with the Earth positioned so that closest approach occurred just a few weeks after perihelion, when the comet was ~0.7 AU from the sun and about the time it reappeared after solar conjunction.  Perfect conditions for getting a "great comet".

Unfortunately, the timing of the C/2019 Y4 apparition is offset about 6 months in the Earth's orbit, so the conditions are pretty poor for post-perihelion observing.  The comet won't reappear for ~2 months after perihelion, and then the comet will be ~1 AU from the Sun and almost 2 AU from Earth.  (I've included plots showing the the 2 comets' motion in the co-rotating frame of the Earth.)  Thus, even if C/2019 Y4 exhibits the same activity as C/1844 Y1, it will not appear to be particularly spectacular by the time we can see it after perihelion. 

On the other hand, it is notable that the Earth's closest approach occurs around the time the comet disappears into solar conjunction, so it will be fairly bright at that point.  And it is supposed to appear in the STEREO field of view around perihelion, so that could give us a good show.

Tony



--
Dr. Clay
-------
Arkansas Sky Observatories
www.arksky.org
ASO MPC H45 - Petit Jean Mountain South
ASO MPC H41 - Petit Jean Mountain North
ASO MPC H43 - Conway West
Publications:  http://arksky.org/publications
Join Arkansas Sky Observatories on Facebook

P. Clay Sherrod
 

Totally agree....let us restrain our outlook for this comet until we see something that indicates that perhaps it actually WILL be something out of the ordinary.
A sudden brightening and expansion of the coma is not sufficient to get the media excited to where we all have a lot of explaining to do later.
 
Dr. Clay
-------
Arkansas Sky Observatories
www.arksky.org
ASO MPC H45 - Petit Jean Mountain South
ASO MPC H41 - Petit Jean Mountain North
ASO MPC H43 - Conway West
Publications:  http://arksky.org/publications
Join Arkansas Sky Observatories on Facebook
 
 

----- Original Message -----
From: michaeljaeger <michaeljaeger@...>
Sent: 2/19/2020 2:59:56 PM
Subject: Re: [comets-ml] C/2019 Y4 ATLAS brightening rapidly

so far it doesn't look like an outbreak to me. Photo from February 18, showing tail and coma more clearly - m1 13mag

--
Dr. Clay
-------
Arkansas Sky Observatories
www.arksky.org
ASO MPC H45 - Petit Jean Mountain South
ASO MPC H41 - Petit Jean Mountain North
ASO MPC H43 - Conway West
Publications:  http://arksky.org/publications
Join Arkansas Sky Observatories on Facebook

Alan Hale
 

Hi Kenneth, all,

That is correct . . . we really can’t have one (i.e., high phase angles) without the other (small elongations).

Comet West in 1976 and Comet McNaught C/2006 P1 both appeared at small elongations and high phase angles, and were brilliant objects; both were quite dusty comets. By way of contrast, Comet PANSTARRS C/2011 L4 was also a dusty comet, and appeared at a small elongation, but was beyond the sun and thus was at a significantly smaller phase angle (60 degrees) and didn’t exhibit forward scattering enhancement of brightness.


Sincerely,
Alan

From: Kenneth Drake <drako_kenneth@...>
Reply-To: <comets-ml@groups.io>
Date: Wed, 19 Feb 2020 15:21:07 -0600
To: <comets-ml@groups.io>
Subject: Re: [comets-ml] C/2019 Y4 ATLAS brightening rapidly

But is not the elongation at that time just 10-13 degrees?

Kenneth Drake Willis, Texas


On 2/19/2020 12:45 PM, Alan Hale wrote:
Hi Tony, all,

One other factor to consider is that, as the comet approaches perihelion, it will be at a high phase angle (in excess of 130 degrees). If this comet has a substantial dust content and if it exhibits significant pre-perihelion dust release, there could be some distinct brightening due to forward scattering of sunlight.


Sincerely,
Alan

From: <farnham@...>
Reply-To: <comets-ml@groups.io>
Date: Wed, 19 Feb 2020 08:48:33 -0800
To: <comets-ml@groups.io>
Subject: Re: [comets-ml] C/2019 Y4 ATLAS brightening rapidly

Hi all

I don't want to dampen the excitement for this comet, but I did want to point out the geometric observing conditions, so that people have realistic expectations.  

The appearance of C/1844 Y1 was in a pretty much ideal situation, with the Earth positioned so that closest approach occurred just a few weeks after perihelion, when the comet was ~0.7 AU from the sun and about the time it reappeared after solar conjunction.  Perfect conditions for getting a "great comet".

Unfortunately, the timing of the C/2019 Y4 apparition is offset about 6 months in the Earth's orbit, so the conditions are pretty poor for post-perihelion observing.  The comet won't reappear for ~2 months after perihelion, and then the comet will be ~1 AU from the Sun and almost 2 AU from Earth.  (I've included plots showing the the 2 comets' motion in the co-rotating frame of the Earth.)  Thus, even if C/2019 Y4 exhibits the same activity as C/1844 Y1, it will not appear to be particularly spectacular by the time we can see it after perihelion. 

On the other hand, it is notable that the Earth's closest approach occurs around the time the comet disappears into solar conjunction, so it will be fairly bright at that point.  And it is supposed to appear in the STEREO field of view around perihelion, so that could give us a good show.

Tony


Alan Hale
 

Hi Clay, all,

I actually quite agree . . . mostly, anyway. I would argue that “predictions” and “speculations about possible behavior” are not quite the same thing, though — as long as the various types of reasonable possible behavior are considered. There is a reason that I cited Fred Whipple . . . In the end, the comet is going to do whatever it is going to do, and we’ll find out as it happens.


Sincerely,
Alan


From: "P. Clay Sherrod" <drclay@...>
Reply-To: <comets-ml@groups.io>
Date: Wed, 19 Feb 2020 15:27:38 -0600
To: "comets-ml@groups.io" <comets-ml@groups.io>
Subject: Re: [comets-ml] C/2019 Y4 ATLAS brightening rapidly

We all hope this comet is going to develop, but goodness the conjecture of splitting, fragmenting, exploding and becoming a spectacle.  Brian Marsden told me after Comet Kohoutek he would never go on record as predicting any "interesting activity" of a comet, even if his speculation was certain.  Let us give it time to at least do some of the things that are being speculated upon.
 
Dr. Clay
-------
Arkansas Sky Observatories
www.arksky.org
ASO MPC H45 - Petit Jean Mountain South
ASO MPC H41 - Petit Jean Mountain North
ASO MPC H43 - Conway West
Publications:  http://arksky.org/publications
Join Arkansas Sky Observatories on Facebook
 
 
----- Original Message -----
From: Alan Hale <ahale@...>
Sent: 2/19/2020 1:23:56 PM
Subject: Re: [comets-ml] C/2019 Y4 ATLAS brightening rapidly

Hi Tony, all,

Another factor to consider . . . 

Since this definitely appears to be a trailing — and, presumably, smaller — fragment of a previously-split comet, it may be a candidate for additional fragmenting, in a manner similar to that of Comet West in 1976. If that were to happen, we may see a significant upsurge in brightness.

On the other hand, it could pull a Comet ISON and disperse away completely.

Fred Whipple: “If you must bet, bet on a horse, not on a comet!”


Sincerely,
Alan

From: Alan <ahale@...>
Reply-To: <comets-ml@groups.io>
Date: Wed, 19 Feb 2020 11:45:28 -0700
To: <comets-ml@groups.io>
Subject: Re: [comets-ml] C/2019 Y4 ATLAS brightening rapidly

Hi Tony, all,

One other factor to consider is that, as the comet approaches perihelion, it will be at a high phase angle (in excess of 130 degrees). If this comet has a substantial dust content and if it exhibits significant pre-perihelion dust release, there could be some distinct brightening due to forward scattering of sunlight.


Sincerely,
Alan

From: <farnham@...>
Reply-To: <comets-ml@groups.io>
Date: Wed, 19 Feb 2020 08:48:33 -0800
To: <comets-ml@groups.io>
Subject: Re: [comets-ml] C/2019 Y4 ATLAS brightening rapidly

Hi all

I don't want to dampen the excitement for this comet, but I did want to point out the geometric observing conditions, so that people have realistic expectations.  

The appearance of C/1844 Y1 was in a pretty much ideal situation, with the Earth positioned so that closest approach occurred just a few weeks after perihelion, when the comet was ~0.7 AU from the sun and about the time it reappeared after solar conjunction.  Perfect conditions for getting a "great comet".

Unfortunately, the timing of the C/2019 Y4 apparition is offset about 6 months in the Earth's orbit, so the conditions are pretty poor for post-perihelion observing.  The comet won't reappear for ~2 months after perihelion, and then the comet will be ~1 AU from the Sun and almost 2 AU from Earth.  (I've included plots showing the the 2 comets' motion in the co-rotating frame of the Earth.)  Thus, even if C/2019 Y4 exhibits the same activity as C/1844 Y1, it will not appear to be particularly spectacular by the time we can see it after perihelion. 

On the other hand, it is notable that the Earth's closest approach occurs around the time the comet disappears into solar conjunction, so it will be fairly bright at that point.  And it is supposed to appear in the STEREO field of view around perihelion, so that could give us a good show.

Tony



--
Dr. Clay
-------
Arkansas Sky Observatories
www.arksky.org
ASO MPC H45 - Petit Jean Mountain South
ASO MPC H41 - Petit Jean Mountain North
ASO MPC H43 - Conway West
Publications:  http://arksky.org/publications
Join Arkansas Sky Observatories on Facebook