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Sun, 11 Jun 2017 - Miras near maximum

Four of the Mira type variable stars on the section's programme - T Cep, R Ser, R UMa and T UMa - are currently near maximum and readily visible in binoculars.

A fifth - R Leonis - is also near maximum but is already disappearing into the evening twilight.

T Cephei is predicted to reach maximum around mid June.

The peak brightness has, over the years, averaged around magnitude 6.0.

In 2017, it had already reached around mag 6.8 by early May, but then seemed to "stall".

Observations in early June have hinted that it might have started brightening again.

T Cephei is fairly easy to track down as it lies not far from the star Beta Cephei, as can be seen in this chart which covers approx 8 degrees by 6 degrees of sky and has north at the top. The chart also labels comparison stars with their magnitudes (decimal points omitted).

 

R Serpentis isn't actually due at maximum until around mid-July, but seems to be well "ahead of schedule" in its rise to maximum.

It was already visible in larger binoculars by mid May and was at around magnitude 7.4 by early June.

The long-term average peak brightness has been about mag 6.9, but maybe in 2017 it is either going to exceed this by some way, or is producing a peak well ahead of schedule.

R Serpentis lies just  below the "head" of the constellation of Serpens Caput, which in turn lies just below Corona Borealis.

The accompanying finder chart, which is approx 7 degrees by 5 degrees and has north at the top, shows the location of R Serpentis and its comparison stars.

 

R Ursae Majoris also seems to be ahead of schedule.

Peak brightness is predicted for the beginning of July but it had reached mag 7.3 by early June - close to its long-term average peak of mag 7.2.

R UMa lies to the "top right" of the main stars of the 'Plough'. The 'pointers', (Alpha and Beta UMa) are a good starting point when locating R UMa.

The accompanying chart, which is approx 7 degrees by 4 degrees and has north at the top, shows the location of R UMa in more detail and labels comparison stars with their magnitudes (decimal points omitted).

 

T Ursae Majoris is another Mira variable that seems to be producing a brighter maximum than usual in 2017 and one that is also somewhat early.

The 2017 maximum is predicted for mid-June and the average peak over the years has been about mag 7.7.

By late May, however, T UMa was already around a magnitude brighter than this and so similar in brightness to comparison stars E and F.

The accompanying finder chart shows the location of T UMa. The chart is approx 7 degrees by 4 degrees and has north at the top.

The star Delta UMa can be a good starting point when locating T UMa.

 

More information about these and other Mira type variables can be found via the section's  Observing Programme Listing. Clicking on the name of a star in this listing takes you to a guide to that star.

 

... and soon to come is the maximum of R Bootis, predicted for early July.

 

Added by: Tracie Heywood