What’s Up in the Night Sky? October 2021 by Fred Barrett

Fred Barrett | Oct 06, 2021

What’s a sunspot? We’ve often heard about these blemishes on the Sun. The Sun appears like a smooth, flawless white-hot sphere but if you took a closer look, you would find pairs or groups of dark spots on the surface. Some are large and some are small and they can last for a few weeks before fading and disappearing back into the Sun’s interior.

Before I continue, you need to know that it is very dangerous to look directly at the Sun. Besides being outright painful, your eyes can be permanently damaged! It takes special filters to dim down the Sun enough to see sunspots. Sunglasses will not protect you at all. This column is about sunspots and not how to look at them with your naked eyes and risk going blind!

Big sunspots can be as large as the Earth and magnetic fields generated by flowing gases within the Sun can be thousands of times stronger than the Earth’s magnetic field. Most sunspots are too small to be seen without using a telescope. Galileo, using his newly invented telescope in 1610, observed that sunspots changed in size and shape. Also, he saw that sunspots near the equator move across the solar disk more rapidly than those positioned near the poles. The rotation period ranged from 27 to 30 days. This meant that different latitudes of the Sun rotated at different speeds. This can only happen with a gaseous body like the Sun. The Earth being solid rotates with the same speed near the poles and at the equator. Galileo seriously damaged his eyes making his observations.

The reason that sunspots are dark is because they are relatively cool with respect to their brighter and hotter surroundings. For example, a sunspot is roughly 5800 degrees Fahrenheit while the regions around it are at about 10,000 degrees Fahrenheit. Note that the sunspot still radiates light. Powerful magnetic fields choke off the heat and energy flowing from the Sun’s interior and cause the cooling of the dark sunspot area.

Each sunspot has a magnetic field that points into or out of the Sun and has a single polarity. Sunspots usually travel in connected pairs and are linked by magnetic loops that extend up into the solar atmosphere. These are powerful, active regions of the Sun. The number and positions of these active regions change over an eleven year cycle. Solar flares or coronal mass ejections (CME) are more frequent and more explosive at the maximum of this cycle than at its minimum.

Sunspots don’t directly affect Earth’s weather but the explosive violence in their active regions produce space weather. Coronal mass ejections and solar flares emit powerful radiation and hurl energetic particles into space that are carried along with the solar winds blowing from the Sun. Earth is shielded from the radiation and violent particles by its atmosphere and magnetic field but out in space, our satellites and astronauts have no such protection. When the Earth is in the path of CME’s, they can produce geomagnetic storms that alter the terrestrial ionosphere and interfering with radio communications. The troposphere is below the ionosphere and is where all Earth’s weather occurs. There doesn’t seem to be any indication that solar active regions have any effect on weather near the ground but if a very serious CME hit the Earth it would induce power surges in our power grids and possibly cause massive long term damage to our electrical systems.

This month look south for wonderful views of Jupiter and Saturn about 30 degrees above the horizon in early evening. In the southwest at midmonth, the Moon is nestled below and between Jupiter and Saturn about 1 hour after sunset. Don’t miss this special sight. A modest telescope can provide a stunning view of the 19 degree tilt of Saturn’s remarkable rings. Venus is bright and low in the southwest just after sunset. It‘s always between 7 and 11 degrees high about an hour after sunset. Mercury, the solar system’s smallest planet, is about 5 degrees above the eastern horizon just before sunrise on the 21st. Start looking for Mercury low to the horizon about an hour before sunrise after the 9th when it has reached inferior conjunction with the Sun.

Unfortunately this month’s full Moon occurs just before the peak of the Orionid meteor shower on October 21.The Orionid shower occurs as we pass through debris left by Halley’s Comet. It’s active from early October through early November but meteor streaks are much fewer than at its peak. A maximum rate of 20 per hour is possible but the full Moon hides all but the brightest.

The winner of last month’s contest prize of the book “The Elements” is Rob Boyer of Maberly. Besides being an accurate description of various elements and curiosities of the Moon’s orbit about Earth, it was very witty and laugh out loud funny.

Here are this month’s highlights. Oct. 3 -17: The Zodiacal light can be seen in the east before morning twilight. A dark site is needed. Oct. 6: New Moon. Oct. 8: The Moon is at perigee – 361,280 Kms. Oct. 9: Mercury is at inferior conjunction. The Moon passes 3 degrees north of Venus. Oct. 12: First Quarter Moon. Oct. 14: The Moon is nestled below and between Jupiter and Saturn about 1 hour after sunset. Oct 20: Full Moon. This Moon is called the Pekelanew Full Moon. It means that it turns leaves white! It’s also called the Hunter’s Full Moon. Watch out! Oct. 21: The Orionid meteor shower peaks. At 6 pm, the Moon passes 1.3 degrees south of Uranus. Oct. 24: The Moon is at apogee – 403,260 Kms. Oct. 28: Last Quarter Moon. On November 7th, daylight savings time ends.

Stay safe and keep looking up!