Here comes the sunspot! – Astronomy Now


The Sun on 24 October, showing sunspot AR2887 near the Sun’s south-eastern limb. Image: SDO/HMI.

A major new sunspot has just rotated into view at the south-eastern limb area of the Sun’s photosphere. Officially designated sunspot AR2887, it was first seen peeping around the Sun’s limb on 22 October. Just 24 hours later, it had doubled in size and shown significantly increased complexity as it cleared the Sun’s limb and astronomers were able to get a better look at it.

The Sun captured on 24 October in extreme ultraviolet (304 angstroms – 0.0000000304m) by NASA’s Solar Dynamics Observatory (SDO). Sunspot AR2887 is clearly very active and more active regions are poised at the eastern limb.

Furthermore, solar spacecraft are keeping tabs on three more active regions on the far side of the Sun (yet to be numbered) which will shortly rotate into view. Indeed, the image above, taken on 24 October by NASA’s Solar Dynamics Observatory, already shows evidence of them at the Sun’s eastern limb.

What are sunspots?

Sunspots are are temporary regions of intense magnetic disturbance which result in cooler regions on the Sun’s photosphere which look darker in contrast with their surroundings. Sunspots can appear individually or in groups and can last for weeks or months.

Sunspots occur over an average 11-year cycle and presently the Sun is not long into Cycle 25, which began in December 2019 and is expected to continue until 2030. In 2019, 281 days – 77 per cent – were spotless, improving to 208 spotless days (57 per cent) in 2020. So far this year only 60 days (20 per cent) have gone without a visible sunspot, so solar activity is picking up as we head toward solar maximum and we experience sunspot maximum; then the Sun seems never to be without some sunspots. The last solar maximum occurred in 2013/2014.

A release of pent-up energy in the sunspot region can cause solar flares and colossal solar storms termed coronal mass ejections (CMEs). NOAA’s (National Oceanic and Atmospheric Administration) Space Weather Prediction Center (SWPC) has already reported AR2887 has produced multiple B-class flares (flares are classified A, B, C, M or X, with X being the most powerful).

As AR2887 turns to face Earth in the coming week or so, astronomers will be looking out for further ejections which could potentially head our way. CME’s can interact with Earth’s magnetic field to give us splendid auroral displays. On a more sober note, very powerful flares can cause CME’s which can reek havoc with orbiting satellites and even affect Earth-based technology such as power grids and long-distance radio communications.

Observe sunspot AR2887 for yourself

Although the Sun culminates presently at a relatively lowly altitude when compared with high-summer, you can still easily follow the progress of AR2887 and the potential new sunspots. One of the safest and easiest methods to observe the Sun in white light is by the tried-and-trusted method of projection.

The Sun’s disc can easily be projected through a small refracting telescope onto a piece of white card. Note the cardboard shield. Image: Geoff Elston.

A small telescope, of 60–100mm (2.5- to 4-inches) in aperture (or a pair of binoculars) is used to project the Sun’s image onto a piece of white card held about eight inches behind the eyepiece. Never look directly at the Sun when aiming your telescope; rather, watch for the tube’s smallest shadow on the ground. Indeed, never look directly at the Sun at anytime, as ding so can cause severe and even irreversible damage to your eyesight.

A dedicated H-alpha telescope gives great views of sunspots and other solar phenomena such as prominences.

A full-aperture white-light solar filter, made of either metallised Mylar film or, preferably, coated glass, and supplied by a reputable astronomy dealer, will give great views. You can also go down the H-alpha or Calcium route by purchasing a dedicated small telescope, such as those manufactured by Lunt and Coronado.





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