Astroblog: Comet C/2026A1 (MAS) update and prospects.

Saturday, April 04, 2026

Comet C/2026A1 (MAS) update and prospects.


Comet C/2026 A1 (MAPS) in the STEREO H1 imager on 30 March. It's the faint streak at the bottom far right.	Comet C/2026 A1 (MAPS) in the SOHO LASCO C3 instrument on the 3rd of April. the "T" shaped head is an imaging artifact.

C/2026 A1 (MAS) is a Kreutz family comet, one of a group of related comets that pass close to the sun. Everyone was very excited that it might become an extremely bright ("great") comet. However, it’s brightness increase stalled (everyone gasped) then started up again (everyone cheered), with what looked to be an eruption plume. As the comet neared the sun all eyes turned to solar monitoring satellites to follow its progress (and possible demise).

C/2026 A1 as seen in the GOES-19 CCOR1 instrument.

The comet has passed intact through the STEREO H1 imager (see above) and was in the field of view of the PUNCH (Polarimeter to Unify the Corona and Heliosphere) satellite, It had a magnitude of 6.5 and a tail extending more than 3 degrees. It has now passed into the field of view of SOHO and the CCOR1 chronograph.

In both these imagers the comet continues to survive and brighten. It is now around magnitude 2-1, bright but a bit dimmer than the sungrazers C/2012 S1 (ISON) and C/2011 W3 (Lovejoy). and not dissimilar to C/2012 E2 (SWAN). SWAN disintegrated before it reached the sun, ISON disintegrated on its pass by the sun, Lovejoy survived solar passage then broke up shortly after.

Currently the two most likely outcomes are that the comet disintegrates before it reaches the sun (like comet SWAN) or it breaks up after perihelion and forms a “headless” comet like C/2011 (W3) Lovejoy. In the latter case we may see a bright tail stretching up from the horizon as twilight fades.

However, astronomer Pedro Rincon reports that MAPS is exhibiting "extremely high cohesion" and is "shedding thin layers from its volatile surface." This suggests there may be a possibility that the comet will survive perihelion. Fingers crossed it will survive after perihelion on the 4th.

If it does survive there is the possibility the comet head will be around -3 to -4 magnitude, (about as bright as Venus), but it will fade rapidly and may be difficult to distinguish against the twilight by the time it is above the horizon in Australia.

Western sky on the evening of Tuesday, April 7 as seen from Adelaide at 18:28 ACST (30 minutes after sunset, click to embiggen). If it hasn't disintegrated, Comet C/2026 A1 may be visible low in the twilight.

C/2026 A1 perihelion is 4 April, the soonest we can see the comet head is probably the 6th or 7th depending on how bright it turns out to be. If there is a decent tail we should see it as the twilight fades, possibly as early at the 5th.

Look to the west, bright Venus will be your guide, the comet should be to the west and a bit below. As the twilight fades the comet and its tail may become more visible. As the days progress the comet gets higher, but it will also be dimming rapidly.

Spotters chart for C/2026 A1 (MAPS) looking west from Adelaide at civil twilight (30 minutes after sunset) from the 7th. The circle is the field of view of 10x50 binoculars. Click to embiggen. Elsewhere in Australia will see a similar view at the equivalent local time (30 minutes after sunset).

Click this link for a printable black and white spotters chart.

We may see the tail in the late twilight, we may be in a C/2011 (W3) Lovejoy situation, where a bright, long headless tail was seen for a couple of days, or a C/2024 G3 Atlas situation, where a modest length but faint tail was visible in the late twilight for nearly a week, depending on how dusty the tail is. Either would be good.