What’s Up in the Night Sky – March

Fred Barrett | Mar 03, 2011

By Fred Barrett

This month let’s have a look at where White Dwarf stars come from. We learned last month that stars under 8 times the mass of our Sun do not blow up as Supernovae. Stars with less than 8 solar masses fuse hydrogen to helium in the star’s core until all the hydrogen there is used up. Now helium starts fusing into oxygen and carbon. The fusion of helium gives off more heat than hydrogen fusion and increases the temperature of the core. Also, since the products of helium fusion are denser than helium, the core shrinks and this makes the core even hotter. The higher temperature and density causes the hydrogen surrounding the core to start fusing. The pressure from this fusion causes the outer layers of the star to expand in size and it becomes a Red Giant (stars on their way to becoming supernovae pass through a Super Red Giant phase). Heat is spread out over a bigger area, the average temperature falls and its colour dulls to red. As the helium fusion stage progresses, energy in the core powers a solar wind that blows away the outer layers of the star. Eventually as the helium is consumed, the oxygen and carbon at the centre of the star do not have enough density and heat to fuse. What is left is a small, hot core called a white dwarf. A typical white dwarf has about the Sun’s mass packed into a space the size of the Earth. Radiation from the white dwarf energizes the surrounding clouds of gas that were blown off earlier, and causes them to glow. At this stage it is called a planetary nebula. This name came about because a famous 18th century observer, Sir William Herschel, thought the nebulae looked like the planet Uranus. This stage only lasts about 50,000 years, until the gas layers have expanded too far to be seen. If you look carefully through your telescope at a planetary nebula, you can see the white dwarf at its centre. Eventually white dwarfs radiate away their heat to become cold lumps of carbon called black dwarfs. This takes so many billions of years that it is thought that the universe isn’t old enough yet for there to be any black dwarfs in existence yet. Our own Sun will end up as a white dwarf in about 5 billion years.

Saturn is the telescope object to observe this month. It will be at its brightest and largest diameter in late March. It can be found just above Spica in the southeast. To find Spica, follow the arc of the Big Dipper handle to bright Arcturus. Continue along the arc an equal distance to an equally bright Spica. It is the bottom star in the constellation Virgo. The rings will be tipped at a respectable 9 degrees from edge on.

Jupiter sets about an hour or two after the sun in the west early in March. Find an unobstructed horizon and look for Mercury below and to the right of Jupiter on the 12th of March shortly after sunset. It will be about 5 degrees from Jupiter and that gap slowly closes on succeeding evenings until on the 15th and 16th, Mercury is above Jupiter. Venus is called the ‘Morning Star’ and rises in the east southeast about an hour and a half before the Sun. Watch for the crescent moon to the left side of Venus on the 1st. The distance slowly increases on the 2nd and 3rd. On the 6th, a new crescent moon can be seen to the right of Jupiter in the west about 30 minutes after sunset. On the 31st the crescent moon is again close to Venus in the southeast and is 6 degrees above it.

This month’s full moon is on the 19th and is the largest full moon of 2011. It is called the “Worm Moon”. Spring is in the air and robins are arriving to snap up the emerging worms. It is also known as the “Sap” moon and I’d better have all my buckets hung from my maple trees and be squared away to boil sap before it appears!

The Zodiacal light is the light reflected from particles in the plane of the solar system. The best time to view this phenomenon this month is the 2 weeks following March 21st. It will appear in the west after evening twilight and will look like a left leaning broad based cone rising up towards the zenith. Make sure you are at a very dark site!

Orion is still prominent in the sky in the southwest at 9 PM and the area above and to its east is filled with deep space objects for your telescope and binoculars. One such object is the globular cluster Messier 44 in the constellation Cancer. Cancer looks like a lopsided propeller and is 30 degrees (3 fist widths) to the east of Orion and about 10 degrees (1 fist width) higher. The cluster is magnificent in binoculars!

Don’t forget that Daylight Savings Time begins Sunday, March 13th at 2 AM. Spring Equinox occurs at 7:21 PM EDT (Eastern Daylight Time) on March 20th. An equinox occurs twice each year when the centre of the sun is in the same plane as the equator.

If you have questions or suggestions, Fred Barrett may be contacted at This email address is being protected from spambots. You need JavaScript enabled to view it.

The Beginner’s Observer’s Guide by Leo Enright is available at the Sharbot Lake Pharmacy or by contacting the Royal Astronomical Society of Canada www.rasc.ca/publications, subscriptions for our very own excellent Canadian astronomy magazine, Sky News, are also available from RASC..