Here comes the sun - or at least, part of it

Whilst several of the planets are still in view in the evening sky, the astronomical highlight of March is the Sun. First of all, the Spring or Vernal Equinox occurs on the 20th of March. This day marks the beginning of spring and is the day when day and night are of almost equal length (hence equinox) with 12 hours of light and dark. Then, on Saturday, March 29th, there will be a partial solar eclipse with about 305 of the sun obscured by the moon, as seen from Torbay. 

When eclipses occur, there are two zones of shadow cast onto the Earth. The central zone, or umbra, is where the eclipse can be seen as “total”. On the Earth's surface, this region is just 100–160 kilometres wide, which is one reason that total solar eclipses are relatively rare. However, outside of the umbra lies the penumbra, within which a partial eclipse can be observed and which can be as much as 6800 kilometres wide at the Earth’s surface. This makes partial eclipses much more common. Historically, there have been as many as 5 eclipses in a single year due to this.

The eclipse on March 29th is of a type that is visible in the (North) Polar region of the Earth. When this type of eclipse occurs, the polar region lies beneath the track of the penumbra, giving rise to a partial eclipse, but the much narrower track of the umbra misses the Earth altogether, so no total eclipse is seen at all. The exact opposite, a partial eclipse visible in the South Polar Region, will then occur in September.

On the morning of 29th March, Torbay Astronomical Society observers will be at the observatory site in Torquay Boys’ Grammar School to help people safely view the eclipse. In order to facilitate this, the society has purchased a number of solar viewing glasses and will also have appropriate viewing platforms set up. The eclipse will begin at 08:51 am with the maximum obscuration occurring at around 10:48 and finally ending at about 12:45. This event is entirely weather dependent and will only happen if there are clear skies on the morning in question. WARNING: Never look directly at the Sun with any optical aid, nor even with the naked eye!

If you wish to attend, please contact the Secretary at the address below with your estimated time of arrival, as we will have to comply with new weekend security arrangements at the school.

Skynotes

Please note all times given in this article are in GMT, which is the current time until the end of the month. 

Sun: From the beginning to the end of March, the hours of daylight increase from 11 to 13 hours. The Spring or Vernal Equinox (the day when night and day are of equal length) occurs on March 20. The clocks go forward by 1 hour to British Summer Time at 02.00am on March 30th.

Mercury: Mercury joins the “parade of planets” this month, although it will always be difficult to see as it remains low in the evening sky. It reaches its farthest distance from the Sun on the 8th and so is in the best possible position to observe this elusive planet. As Mercury is the closest planet to the Sun, it is often lost in the glare of the Sun. The sky will still be quite bright, but, with the sun out of the way, it will be safe to search the sky with binoculars or a telescope. 

Venus: Venus still stands out as a brilliant object seen against the background stars of Pisces in the early evening, setting just before 21:00.

Mars: Mars is visible through most of the night, reaching magnitude +1 and seen against the background stars of Gemini. 

Jupiter: Jupiter dominates the evening sky until it sets around 1:30am. The giant planet is seen against the background stars of Taurus. With a large pair of binoculars or a small telescope, you should be able to follow the movement of the planet’s four largest moons, Io, Europa, Ganymede, and Callisto, that were discovered by Galileo in 1610 when he observed them whilst first using his telescope.

Saturn: Saturn is no longer visible. 

Uranus and Neptune: Uranus is seen against the background stars of Aries but will move into Taurus as the month progresses. At magnitude 5.8, it is visible in binoculars. Look for a tiny greenish disc compared to the pinpoints, which are the stars. Neptune is in conjunction with the Sun and is not visible this month.

Meteor Shower: There are no regular meteor showers this month. However, stray or sporadic meteors can still be seen at any time. Some of these can be very bright. 

Deep sky: March is also the time of year when the greatest number of deep sky objects—star clusters, nebulae, and galaxies—can be seen. Amateur astronomers often do an “all-nighter” observing session to see as many of the brighter “Messier” objects as they can in a single night. This is known as a Messier Marathon. Die-hards stay all night, but it can be fun to “drop in” for an hour or two during the night. In order to see many of these objects, even the Moon has to be out of the way. There are, however, two opportunities this year. Of course, all of this is entirely dependent on the weather, so check the society website for details of arrangements for this event. 

The First Quarter Moon occurs on March 6th, with the Full Moon on the 14th, the Third Quarter then follows on the 22nd, and the New Moon is on the 29th. 

Data supplied by Dale Giles, Torbay Astronomical Society. 

Diary Dates

The next meetings of the Torbay Astronomical Society will be held at Torquay Boys Grammar School, Shiphay Manor Drive, TQ2 7EL. On March 13th in the Forum Lecture Theatre, our speaker will be Chairman John Stapleton, who will give a talk entitled . “A True and Accurate History of the TBGS Observatory—Part Two.” This talk includes a brief recap of “Part One” for the benefit of those who may have missed it. And on March 28th an observational evening will be held in Room PL4 and the Observatory (weather permitting) when members will be delighted to provide views of the objects discussed in this article. In the event of bad weather, short talks and videos will be presented alongside informal discussion and an opportunity to get to know the Society. Then on March 29th we will, again, be at the observatory (weather dependent) for the partial eclipse of the sun (see main article). For details, contact the Secretary TAS at astrosecretary@gmail.com. Visitors and prospective members are especially welcome.