Comet C/2021 D1 (SWAN) will make its closest approach to the Sun, at a distance of 0.91 AU.
|28 Feb 2021||–||C/2021 D1 (SWAN) at perihelion|
|07 Feb 2021||Aquarius||Not observable|
|09 Feb 2021||Aquarius||Not observable|
|11 Feb 2021||Aquarius||Not observable|
|13 Feb 2021||Pegasus||Not observable|
|15 Feb 2021||Pegasus||Not observable|
|17 Feb 2021||Pegasus||Not observable|
|19 Feb 2021||Pisces||Not observable|
|21 Feb 2021||Pegasus||Not observable|
|23 Feb 2021||Pegasus||Not observable|
|25 Feb 2021||Pegasus||Not observable|
|27 Feb 2021||Pegasus||Not observable|
|01 Mar 2021||Pegasus||Not observable|
|03 Mar 2021||Pegasus||Not observable|
|05 Mar 2021||Pegasus||Not observable|
|07 Mar 2021||Pegasus||Not observable|
|09 Mar 2021||Pisces||Not observable|
|11 Mar 2021||Pisces||Not observable|
|13 Mar 2021||Andromeda||Not observable|
|15 Mar 2021||Andromeda||Not observable|
|17 Mar 2021||Pisces||Not observable|
|19 Mar 2021||Pisces||Not observable|
At the moment of perihelion it will not be observable – it will reach its highest point in the sky during daytime and will be no higher than 8° above the horizon at dusk.
The chart below shows the path of C/2021 D1 (SWAN) over the course of its apparition, as calculated from the orbital elements published by the Minor Planet Center (MPC). It is available for download, either on dark background, in PNG, PDF or SVG formats, or on a light background, in PNG, PDF or SVG formats. It was produced using StarCharter.
Comets are intrinsically highly unpredictable objects, since their brightness depends on the scattering of sunlight from dust particles in the comet's coma and tail. This dust is continually streaming away from the comet's nucleus, and its density at any particular time is governed by the rate of sublimation of the ice in the comet's nucleus, as it is heated by the Sun's rays. It also depends on the amount of dust that is mixed in with that ice. This is very difficult to predict in advance, and can be highly variable even between successive apparitions of the same comet.
In consequence, while the future positions of comets are usually known with a high degree of confidence, their future brightnesses are not. For most comets, we do not publish any magnitude estimates at all. For the few comets where we do make estimates, we generally prefer the BAA's magnitude parameters to those published by the Minor Planet Center, since they are typically updated more often.
Based on the magnitude parameters published for this comet by the BAA Comet Section, we estimate that it may be around mag 9 at perihelion. This estimate is based on observations that the BAA has received from amateur astronomers, assuming that its current level of activity will remain constant.
You will probably require a telescope to see this comet. It is unlikely to be visible through bird-watching binoculars, and even less likely to be visible to the unaided eye.
The comet's position at perihelion will be:
|Comet C/2021 D1 (SWAN)||23h29m20s||13°18'N||Pegasus||9.4|
The coordinates are given in J2000.0.
|The sky on 28 February 2021|
17 days old
All times shown in EST.
This event was automatically generated on the basis of orbital elements published by the Minor Planet Center (MPC) , and is updated whenever new elements become available. It was last updated on 21 Sep 2021.
© Andy Roberts 1997. Pictured comet is C/1995 O1 Hale-Bopp.