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Thread: Comet ATLAS thread: will it be visible to us, a Great Comet?

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    Comet ATLAS thread: will it be visible to us, a Great Comet?

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    Quote Originally Posted by Roger E. Moore View Post
    I recall comet Kohoutek getting bright very fast, but that was apparently just an initial puff. In the final analysis it wasn't all that amazing.
    Forming opinions as we speak

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    While sheltering in place today, did a little research. One researcher said it has an orbit similar to the Great Comet of 1844. I looked at light curves and the comet is a little fainter than Comet Mcnaught (2006), it got up to -5. Hopefully, we'll get lucky. As they say: Comets are a lot like cats, they both have tails and pretty much do what they want to.

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    Quote Originally Posted by Superluminal View Post
    While sheltering in place today, did a little research. One researcher said it has an orbit similar to the Great Comet of 1844. I looked at light curves and the comet is a little fainter than Comet Mcnaught (2006), it got up to -5. Hopefully, we'll get lucky. As they say: Comets are a lot like cats, they both have tails and pretty much do what they want to.
    Excellent use of sheltering time! Yay, research! Also, very good cat analogy.
    Do good work. —Virgil Ivan "Gus" Grissom

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    For your consideration. Light curves of Comet Atlas and Mcnaught (2006)P. From Seichii Yoshida's web site. Just over one month before perihelion both comets were nearly the same.
    Mcnaught went on to achieve a mag. of -6, passing .17 AU from the Sun and .849 AU from Earth.
    Perihelion for Atlas will be .253 AU and will be .896 AU from Earth. Mag. ??? Fairly comparable figures.
    I hope it's an interesting spectical. After this pademic, I hope people can get together and enjoy the sky. With out "social distancing."

    https://forum.cosmoquest.org/attachm...1&d=1584836603
    https://forum.cosmoquest.org/attachm...1&d=1584836603
    Attached Images Attached Images

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    Oooo, here's hope for the future of Great Comets! Thank you!
    Do good work. —Virgil Ivan "Gus" Grissom

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    Quote Originally Posted by antoniseb View Post
    I recall comet Kohoutek getting bright very fast, but that was apparently just an initial puff. In the final analysis it wasn't all that amazing.
    I was a freshman in college when I saw fuzzy little Kohoutek through my telescope at the University of Kentucky, from the roof of the parking garage. Ah, youth.
    Do good work. —Virgil Ivan "Gus" Grissom

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    Do you remember comet West? It followed Kohoutek and didn’t get a lot of press, apparently because they had been burned with Kohoutek, but it was a very bright comet. No need for a telescope from my then light polluted yard, and it was beautiful. I remember it looking much like this:

    https://steemit.com/comet/@mahmoud9088/comet-west

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    Quote Originally Posted by Van Rijn View Post
    Do you remember comet West? It followed Kohoutek and didn’t get a lot of press, apparently because they had been burned with Kohoutek, but it was a very bright comet. No need for a telescope from my then light polluted yard, and it was beautiful. I remember it looking much like this:

    https://steemit.com/comet/@mahmoud9088/comet-west
    Would you believe... I missed it. Submerged in college classes and other stuff. Dang.
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    Quote Originally Posted by Roger E. Moore View Post
    Oooo, here's hope for the future of Great Comets! Thank you!
    I need a great comet, right about now. Here's hoping too.

    spaceweather.com has a good write up at the moment (though they change the content of the linked website all the time).

    No one knows how big the icy core of Comet ATLAS (C/2019 Y4) might be--possibly no wider than a few kilometers. One thing's for sure, though, the comet's atmosphere is huge. New images from amateur astronomers around the world show that ATLAS's gaseous envelope has ballooned in diameter to ~720,000 km--about half as wide as the sun.
    They have a nice finder chart for finding it in your telescope or binocs.
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    Ursa Major is easy to see from our house, hoping for the best.
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    Bright as Venus?

    "Some astronomers think the comet, formally called C/2019 Y4, could put on a big show, perhaps growing as bright as Venus."
    https://www.cnet.com/news/brightenin...just-a-little/
    Do good work. —Virgil Ivan "Gus" Grissom

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    Problem though. It'll be very close to the sun and visible low on the horizon.

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    Quote Originally Posted by Superluminal View Post
    Problem though. It'll be very close to the sun and visible low on the horizon.
    ?? In the northern hemisphere it looks like Atlas Y4 will be near Cassiopeia on May 1 and in the northern part of the sky, relatively far away from the Sun. Same for Atlas Y1; it'll be near Ursa Minor.

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    Well, I just used the JPL Horizons site to compute the position of the object between late April and early June,
    and it is certainly not in Cassiopeia, nor far from the Sun. It really will be low in the sky before dawn and
    close to the Sun at its brightest.

    Code:
    *************************************************************************************
     Date__(UT)__HR:MN     R.A._____(ICRF)_____DEC Azi_(a-appr)_Elev a-mass mag_ex  T-mag
    *************************************************************************************
    $$SOE
     2020-Apr-27 00:00 *m  05 33 18.68 +61 50 48.8 320.0076  53.5885  1.241  0.331   7.45
     2020-Apr-28 00:00 *m  05 29 21.16 +61 25 34.2 319.1946  52.6825  1.256  0.335   7.23
     2020-Apr-29 00:00 *m  05 25 25.97 +60 59 29.6 318.4368  51.7494  1.272  0.339   7.01
     2020-Apr-30 00:00 *m  05 21 32.56 +60 32 31.0 317.7312  50.7887  1.289  0.344   6.78
     2020-May-01 00:00 *m  05 17 40.42 +60 04 33.3 317.0744  49.7998  1.308  0.349   6.54
     2020-May-02 00:00 *m  05 13 49.03 +59 35 31.2 316.4634  48.7817  1.328  0.354   6.30
     2020-May-03 00:00 *m  05 09 57.90 +59 05 18.1 315.8952  47.7333  1.350  0.360   6.04
     2020-May-04 00:00 *m  05 06 06.55 +58 33 46.6 315.3668  46.6531  1.373  0.366   5.78
     2020-May-05 00:00 *m  05 02 14.53 +58 00 48.5 314.8755  45.5394  1.399  0.373   5.51
     2020-May-06 00:00 *m  04 58 21.41 +57 26 14.1 314.4183  44.3903  1.427  0.381   5.23
     2020-May-07 00:00 *m  04 54 26.80 +56 49 52.7 313.9926  43.2033  1.458  0.389   4.93
     2020-May-08 00:00 *   04 50 30.34 +56 11 32.2 313.5956  41.9758  1.493  0.398   4.63
     2020-May-09 00:00 *   04 46 31.75 +55 30 59.0 313.2246  40.7048  1.531  0.408   4.31
     2020-May-10 00:00 *   04 42 30.76 +54 47 57.6 312.8768  39.3869  1.573  0.420   3.98
     2020-May-11 00:00 *   04 38 27.22 +54 02 11.0 312.5495  38.0183  1.620  0.432   3.64
     2020-May-12 00:00 *   04 34 21.03 +53 13 19.7 312.2395  36.5948  1.673  0.447   3.28
     2020-May-13 00:00 *   04 30 12.20 +52 21 02.4 311.9439  35.1117  1.734  0.463   2.91
     2020-May-14 00:00 *   04 26 00.89 +51 24 55.0 311.6593  33.5639  1.804  0.481   2.52
     2020-May-15 00:00 *   04 21 47.39 +50 24 31.1 311.3819  31.9458  1.884  0.503   2.12
     2020-May-16 00:00 *   04 17 32.23 +49 19 21.7 311.1079  30.2517  1.978  0.528   1.70
     2020-May-17 00:00 *   04 13 16.15 +48 08 55.2 310.8327  28.4753  2.089  0.557   1.25
     2020-May-18 00:00 *   04 09 00.19 +46 52 37.7 310.5511  26.6105  2.222  0.593   0.79
     2020-May-19 00:00 *   04 04 45.79 +45 29 54.0 310.2574  24.6512  2.384  0.636   0.31
     2020-May-20 00:00 *   04 00 34.81 +44 00 08.0 309.9446  22.5920  2.585  0.690  -0.20
     2020-May-21 00:00 *   03 56 29.66 +42 22 45.3 309.6049  20.4291  2.840  0.758  -0.72
     2020-May-22 00:00 *   03 52 33.41 +40 37 15.2 309.2293  18.1605  3.172  0.846  -1.26
     2020-May-23 00:00 *m  03 48 49.89 +38 43 15.5 308.8073  15.7883  3.619  0.966  -1.81
     2020-May-24 00:00 *m  03 45 23.86 +36 40 38.3 308.3271  13.3198  4.247  1.133    -2.
     2020-May-25 00:00 *m  03 42 21.00 +34 29 38.0 307.7761  10.7701  5.175  1.381    -3.
     2020-May-26 00:00 *m  03 39 48.00 +32 11 00.8 307.1411   8.1646  6.651  1.775    -3.
     2020-May-27 00:00 *m  03 37 52.30 +29 46 16.0 306.4105   5.5411  9.251  2.469    -4.
     2020-May-28 00:00 *m  03 36 41.57 +27 17 43.4 305.5763   2.9511 14.548  3.882    -4.
     2020-May-29 00:00 *m  03 36 22.77 +24 48 34.2 304.6375   0.4573 27.407  7.313    -5.
     2020-May-30 00:00 *m  03 37 00.76 +22 22 38.2 303.6034  -1.8724   n.a.   n.a.    -5.
     2020-May-31 00:00 *m  03 38 36.89 +20 03 53.0 302.4956  -3.9767   n.a.   n.a.  -4.95
     2020-Jun-01 00:00 *m  03 41 08.12 +17 55 44.3 301.3458  -5.8119   n.a.   n.a.  -4.80
     2020-Jun-02 00:00 *m  03 44 27.42 +16 00 30.4 300.1908  -7.3610   n.a.   n.a.  -4.49

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    Quote Originally Posted by StupendousMan View Post
    Well, I just used the JPL Horizons site to compute the position of the object between late April and early June,
    and it is certainly not in Cassiopeia, nor far from the Sun. It really will be low in the sky before dawn and
    close to the Sun at its brightest.
    I was using May 1 as a target date on Heavens Above when Y4 is close to Cameloparis. After that the comet progressively moves to a view nearer the horizon. (Or else HA is out if whack).

    https://www.heavens-above.com/comet....C%2F2019%20Y4&

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    I sure hope comets now foretell the end of a plagues rather than new ones.
    We know time flies, we just can't see its wings.

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    Quote Originally Posted by StupendousMan View Post
    Well, I just used the JPL Horizons site to compute the position of the object between late April and early June,
    and it is certainly not in Cassiopeia, nor far from the Sun. It really will be low in the sky before dawn and
    close to the Sun at its brightest.
    I notice they show as much as an 18 mag difference between the combined mag. (T-mag.) and the nuclear mag. (N-mag.), but that's a humongous difference. So is the nucleus really going to be that wimpy in brightness or am I not understanding what is meant by the nucleus region?
    We know time flies, we just can't see its wings.

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    The nucleus is the tiny chunk of ice and rock. By itself it wouldn't be very bright. The coma is the cloud of dust and gas surrounding the necleus.

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    Quote Originally Posted by Superluminal View Post
    The nucleus is the tiny chunk of ice and rock. By itself it wouldn't be very bright. The coma is the cloud of dust and gas surrounding the necleus.
    So the nucleus magnitude is hypothetical, I assume, since the coma would obscure its visibility during its perihelion trip. A coma mag. (C-mag. ?) would be nice.
    We know time flies, we just can't see its wings.

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    If these magnitude estimates are accurate, Atlas maybe getting fainter. But I would not give up yet. It's still over an AU from the sun.
    https://www.cobs.si/

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    I've created two charts and an ephemeris for Comet C/2019 Y4 ATLAS: https://www.CurtRenz.com/comets.html
    For astronomical graphics and data visit
    https://www.CurtRenz.com/astronomy.html

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    Quote Originally Posted by George View Post
    So the nucleus magnitude is hypothetical, I assume, since the coma would obscure its visibility during its perihelion trip. A coma mag. (C-mag. ?) would be nice.
    From what we have learned so far about comets is that the nucleus is one of the lowest albedo bodies in the solar system, they are really "dark as night". The only reason that we have pictures from Rosetta is because there were very good cameras and the images were stretched in brightness and contrast by enormous values.
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    Quote Originally Posted by Centaur View Post
    I've created two charts and an ephemeris for Comet C/2019 Y4 ATLAS: https://www.CurtRenz.com/comets.html
    Thanks for the resource, I will have to wait a bit, still, in Graz, before I can see it. Nasty mountains around my house, we hates it, my precioussss.
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    Quote Originally Posted by tusenfem View Post
    Thanks for the resource, I will have to wait a bit, still, in Graz, before I can see it. Nasty mountains around my house, we hates it, my precioussss.
    I've been wondering, how do you pronounce Uhrturm?
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    Quote Originally Posted by tusenfem View Post
    From what we have learned so far about comets is that the nucleus is one of the lowest albedo bodies in the solar system, they are really "dark as night". The only reason that we have pictures from Rosetta is because there were very good cameras and the images were stretched in brightness and contrast by enormous values.
    Are they darker than the average KBO? If so, would that be due to their loss of ices in prior runs?
    We know time flies, we just can't see its wings.

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    Quote Originally Posted by Roger E. Moore View Post
    I've been wondering, how do you pronounce Uhrturm?
    Uhrturm (Clock Tower, Graz's landmark) is pronounced:

    U as in booh!, the first U a bit longer than the second, so that would then result in "ooohrtoohrm".
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    Quote Originally Posted by George View Post
    Are they darker than the average KBO? If so, would that be due to their loss of ices in prior runs?
    As far as I know, yes they are darker, and one of the reasons is the amount of (sintered) dust on the surface of the nucleus, which absorbs the light very very well (I cannot find a graph that explained it right now, maybe later). Exposed ice then stands out like a beacon, after e.g. a landslide on 67P.

    But if we can visit a dynamically new object with Comet Interceptor, it would be interesting to see what the albedo is of a "pristine comet". You will have to wait a bit, though, launch is in 2028.
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    Quote Originally Posted by tusenfem View Post
    Uhrturm (Clock Tower, Graz's landmark) is pronounced:
    U as in booh!, the first U a bit longer than the second, so that would then result in "ooohrtoohrm".
    Thank you. Sorry I got off topic.
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    Quote Originally Posted by tusenfem View Post
    As far as I know, yes they are darker, and one of the reasons is the amount of (sintered) dust on the surface of the nucleus, which absorbs the light very very well (I cannot find a graph that explained it right now, maybe later).
    "Sintered dust"? Is that some sort of solar-fried dust; a charcoaling-effect (ok,my word, I suppose) of the dust during a perhelion frolic? [Sorry. You're getting my mental release from my self-imposed restriction from punning in the pandemic pages.]

    But wouldn't the loss of much of the surface ices also decrease the albedo, though I suppose the dust will settle on the surface and negate their reflectivity, perhaps.

    Exposed ice then stands out like a beacon, after e.g. a landslide on 67P.
    That's cool.

    But if we can visit a dynamically new object with Comet Interceptor, it would be interesting to see what the albedo is of a "pristine comet". You will have to wait a bit, though, launch is in 2028.
    But would that be a pre-comet and just a KBO or an Oort Cloud object?
    We know time flies, we just can't see its wings.

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