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Wed, 15 Jan 2014 - R Scuti starts Apparition

15th January 2014

Apparition of the variable star R Scuti has began. John Toone of the British Astronomical Association reports his observation of the star, which is now visible in the morning sky, as follows:

14 Jan 2014    0652GMT    4.7    15X70B

R Scuti can be found in the constellation Scutum which is pictured below (many thanks to Robin Scagell for the graphic)

A chart to locate the star can be found HERE

Amateur astronomer and SPA Meteor Section Director, Tony Markham, added:

For Deep Sky observers Messier 11, the 'Wild Duck Cluster' is the highlight of the constellation of Scutum. Deep Sky observers have no need to leave their warm beds on cold winter mornings to observe this cluster, however, since it will look the same during warm summer evenings.

For Variable Star observers there is only one candidate for the highlight of Scutum and that is the variable star R Scuti. With R Scuti constantly changing in brightness, observers don't want to miss something dramatic that might happen during the winter months.

Although R Scuti is routinely described as spending most of the time around 5th magnitude and showing two fades (one deep and one shallow) in each of its 140 day cycles, that gives a false impression. It is much less predictable (and a lot more interesting) than that. It can sometimes change from being visible with the unaided eye to being a challenging binocular object (or the reverse) in as little as two weeks.

2013 was a particularly dramatic year for R Scuti. After a quiet start, a fade set in during late April and it was soon obvious that this would be a deep minimum. However, rather than brightening again after a couple of weeks, R Scuti kept on getting fainter and didn't reach minimum brightness until early June ... and stayed there through to early July. Eventually it brightened again. Then, in early August, just as it seemed to be getting close to 5th magnitude, R Scuti faded again. Would this be the expected shallow minimum? No - it turned out to be another prolonged deep minimum. Indeed, this minimum was showing signs of lasting even longer than the earlier one when R Scuti dramatically shot up in brightness in late October, brightening by nearly 4 magnitudes in only about a fortnight. Finally, in December,  just as R Scuti was sinking into the evening twilight it started to faded into another(!) deep minimum, reaching magnitude 7.1 by the evening of Dec 22.

The Light Curve above shows the magnitude fluctuations as recorded by Tony Markham

How will R Scuti perform in 2014?  We don't know! The only way to find out is to go outside and observe it.

Mid January sees R Scuti low in the ESE as it emerges from the morning twilight and Variable Star observers are keen to spot it as soon as possible. The SPA's Tony Markham scanned the ESE sky on the morning of Jan 13, but was thwarted by cloud close to the horizon. However John Toone of the BAA VSS had more luck the following morning and has reported an observation of R Scuti at magnitude 4.7.

This shows that R Scuti has brightened again following the minimum at the end of 2013. It takes a brave man to predict the future brightness changes in R Scuti, However, given R Scuti's behaviour during 2013, there is a good chance that it may fade again in the coming month.

You can locate R Scuti using this finder chart. When near maximum brightness, R Scuti will be the brightest of the stars in the small trapezium that it makes up along with the comparison stars labelled D, E and F. In shallow minima (of which we didn't see any in 2013!), R Scuti becomes fainter than star D, but remains brighter than F. Deep minima take it fainter than star H and, in exceptional minima, such as those seen in 2013, it can become as faint as the stars labelled I and J. If you keep an eye on R Scuti throughout 2014, you will be able to plot your observations and produce an impressive light curve showing its rises and falls in brightness.

Fascinating as it is to monitor, R Scuti isn't only of interest to amateur astronomers. It is of interest also to professional astronomers because it and several other similar yellow supergiant stars appear to be going through a (astronomically speaking) short lived phase in their evolution. Changes in their behaviour give clues as to whether models of stellar evolution are correct or may need tweaking. Where do professional astronomers get their light curves from?   They rely on observations made by amateur astronomers.

 

Added by: Tracie Heywood