Largest Sunspot Group of Cycle 25

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    Peter Meadows

    In addition to producing 3 X-flares over the last day or so, sunspot group AR 13590 is also the largest of this cycle so far. Today (23rd Feb) it reached an area of 1800 millionths of the Sun’s visible hemisphere (MSH). It is an easy naked eye sunspot (using suitable eye protection such as eclipse glasses). It addition it is now ideally placed on the solar disk as it will approach the central meridian in a couple of days. Weather permitting it will be on the solar disk for another week or so.

    AR 13590 could become the first Great sunspot group of this cycle (The term great sunspot group generally refers to a group with a mean area for the solar disk-passage greater than or equal to 1500 MSH [1]. This size is about three times larger than of a sunspot that is just visible with the protected naked eye.
    [1] Newton, H.W., ‘The lineage of the great sunspots’, Vistas in Astronomy, Volume 1, Pages 666-674 (1955).

    The Solar Section welcomes your observations.

    Mr Jack Martin
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