North Hawaii News Articles from CFHT

The Night Sky in February

February 5th will mark the start of year 4698 in the Chinese calendar, arguably the oldest one in the world. People all over the world will celebrate the beginning of the year of the Dragon by eating noodles and potstickers, setting off firecrackers and giving 'hong bao' (red envelopes with money) and other gifts. Why mention this in an article about astronomy? Calendars are one of the first practical products of astronomy, and this seems like a good time to discuss the relationship.

You may have noticed that Chinese New Year does not fall on the same date in the Western (Gregorian) calendar each year, but did you realize this was because the moon orbits the earth in roughly 29.53 days, and not exactly 28 or 30? Nearly all types of calendars ever used in the world are based on either the motion of the earth around the sun, or the moon around the earth, or both. Understanding these cycles was the job of early astronomers in many cultures. The fact that the two cycles are not synchronized has led to the variety of calendars which different cultures have created.

The Chinese calendar is primarily based on the cycles of the moon, with regular adjustments to match the solar year. Every month starts on New Moon, when the moon is hidden by the glare of the sun, and lasts roughly roughly 29 days. A year is 12 moon cycles (months), or roughly 354 days. Oops, that is 11 days too short by the Western idea of a year. The Chinese calendar adds an entire extra month (a 'leap month') roughly once every 3 years to keep synchronize with the solar year. Why bother synchronizing? The solar year determines the seasons, so if leap months were not added occasionally, the beginning of the year would drift from the end of winter to autumn, summer, and so on. This brings us back to the idea of the New Year.

In the Chinese calendar, the New Year marks the beginning of Spring. To be precise, the New Year is the date of the second New Moon following the Winter Solstice. Thus, February 5th will be a New Moon, and the skies over the Big Island will be very dark. If you step outside on a dark night this time of year, you have a nice variety of interesting objects to look at, whether you have a small telescope, a pair of binoculars, or the oldest astronomical detectors: your unaided eyes. In winter time (or as the Chinese astronomers might say, at the beginning of spring), several constellations with bright stars are visible.

Face south, and you will easily see the Warrior Orion high in the sky, with two of the brightest stars in the sky, one on his left shoulder, the other on his right knee. The middle of the three stars which make up his sword (the line of stars 'hanging' below his belt) is an excellent target for a small telescope -- there is a small cluster of stars embedded in a the bright Orion Nebula. This nebula is a site where stars have recently been formed, or are still being formed from the gas which makes up the nebula. These stars you see are very young, in an astronomical sense: the bright ones are only a million years old or so, and the youngest visible ones may be only a few hundred thousand years old. (If this doesn't seem so young, consider that the Sun is 5 billion years old, over 5000 times older than the oldest stars in the Orion Nebula).

Near Orion, and towards the south, is the brightest star in the sky - Sirius. The reason this star looks so bright to us here on Earth is that it is actually very close: It is the 9th closest star to the sun, and the closest star visible without a telescope this time of year. If this star were as far away as either of the two bright stars in Orion, it would barely be visible: these stars are 100 times further than Sirius.

North of Orion is a V-shaped clump of stars which makes up the face of Taurus the bull. The bright reddish star Aldebaran is near this group. The group of stars has the name 'the Hyades', and is actually a small cluster of stars which formed in a cloud much like the Orion Nebula. This group is much older than the stars in Orion, and probably formed over 500 million years ago. The gas that these stars formed from has long since been used up or dispersed.

Near the Hyades is a faint object that you can see only if you have a small telescope. This object is the Crab Nebula - another cloud of gas and dust. Unlike the Orion Nebula, however, this cloud marks the end of the life of a star, not the beginning. At this location, a large star died a violent death, exploding in what is called a 'supernova'. In this explosion, this star became briefly brighter than all of the other stars in our galaxy combined. This explosion took place on July 4, 1054 and was observed by Chinese astronomers, who recorded their observations of the bright, new star in their extensive annals. In 1942, two astronomers in the US demonstrated that the cloud of gas we now see was left behind by the explosion observed by the Chinese astronomers 900 years before.

Astronomical objects such as these make excellent subjects for astrophotography, and are always very popular with lay people. Astronomers frequently try to provide the public with nice images, even though they are not the main science products of an observatory. For example, you can view regularly produced pictures from the Hubble Space Telescope on their web site ( or from the Canada France Hawaii Telescope's Picture of the Week ( In the spirit of the association between Calendars and Astronomy, CFHT has recently produced a calendar for 2000 featuring images of the sky taken with the CFHT. For information on the calendar, see

Eugene Magnier