March Night Skies and the Threat of Asteroids
Did you know that an asteroid the size of a mountain smashed into Earth and caused a blackout of several years and resulted in the extinction of Dinosaurs. That was 65 million years ago. The threat of something serious hitting us is ever present, though not perhaps as big as a mountain. Actually by certain calculations a major asteroid hit of this scale has struck Earth every 65 million years or so. So we are due for a hit that could wipe out humanity? Millions of years is a very long time compared to our lifetimes. In fact even hundreds of thousands of years is also just as long in human terms. So we do not have to worry unnecessarily about humanity being wiped out tomorrow.
However, the possibility of being struck by smaller objects from outer space is being increasingly reported in recent times. Last year in February, a 20 meter asteroid actually did strike Earth near a small town in Russia. It caused significant damage and caused injuries. Imagine what could happen if a bigger object was to hit us directly on a town or city. With advances in technology, more and more observatories are focusing attention on observing Near Earth Objects (NEO) and frighteningly close misses are being reported.
Last month on February 18, an asteroid the size of three football fields passed close to Earth just 10 lunar distances away. This is extremely close in space terms. More recently on March 7 an object whizzed past Earth only lunar distances away, and even more dangerously, on March 7, a 5 meter size asteroid came less than three quarter of the distance to the Moon. These are extremely close misses and are difficult to track in good time to give sufficient warning. The picture below gives an idea just how many there are that are known to orbit close to Earth.
Diagram adapted from: http://www.unsolving.com/news.php?name=2014075222
Thousands of NEOs crisscross the orbit of the Earth and sufficient attention is paid to observe them; and some may be even too faint to observe from a distance. Instruments that are currently focused on such observations have huge amounts of electronic signals that are stored in a database. It needs people to analyse them to find those that pose immediate danger. NASA has recently offered a prize of 35,000 USD (http://www.topcoder.com/asteroids/) for someone to come up with a computing method (algorithm) that will automatically filter the data to find the dangerous asteroids. If we can predict the approach of killer asteroids early enough we can find a way of deflecting them or even find a way of escaping from Earth ourselves!!
Let us get back to reality of the night skies this month. Jupiter shines extremely brightly directly overhead at 8 pm. It is in Gemini constellation and to the close to its left, if you are facing west, is Orion constellation near its red giant star Betelgeuse.
Mars rises in the east by 8:30 pm by mid March. It is now very bright red and increasing in brightness as it approaches closer to Earth and at opposition with the Sun on April 8. Mars continues its retrograde movement, shifting from east to west across the background stars. Follow the shifting position of Mars with respect to the nearby bright star Spica in Virgo constellation. You will be able to notice this eastward shift as it comes closer to Spica and passes it. Later in the year, from May, it will resume its normal shift from west to east and will approach Spica again, but this time from the west.
Mars will be most interesting to observe on Tuesday March 18 when the Moon will be seen close to Mars and a bright star Spica which will be even closer to the Moon. If you watch it over the course of a few hours, every hour, until after midnight, you will even see a change in the position of the Moon with respect to Mar and Spica. Soon after midnight the trio will be seen in a straight line! For further details visit http://www.astronomyintanzania.or.tz.
Another interesting date to observe is after midnight of Thursday March 20 when Moon will be seen extremely close to Saturn just a Moon diameter away. In fact if you watch it over several hours you will see the Moon coming closer and closer to Saturn. These are examples of observing movement of celestial object whose movements over a few hours we would otherwise not see. Of course if you follow the movement of the Moon day by day you will see that as it changes from crescent to full moon, it moves from the western sky as a crescent to the eastern sky when it rises as a Full Moon.
Venus shines extremely brightly in the early dawn skies and is at its highest elevation above the horizon. Through a telescope it will be seen in half phase.
The Moon will be full on March 24 and will be in New Moon phase on March 30.
The Milky Way dominates the night sky as it stretches right across the sky from southeast to northwest in early evening hours. It stretches from the Southern Cross in the southeast horizon, up through Sirius (the Dog), between Orion (the Hunter) and Gemini (the Twins) in the overhead skies, descending to Taurus (the Bull) and ending in Perseus in the northwest horizon. Leo (the Lion) fills the eastern sky.
The pointers, Southern Cross in the south, and Big Dipper in the north, rise early in the east and can be used to find north-south direction after 9 p.m. The long arm of the cross points directly south, while the edge stars of the dipper point north. Be careful not to confuse the False Cross with the real one! The southern sky also contains the brightest and second brightest stars Sirius and Canopus respectively (remember that planets can be brighter than these, e.g. Jupiter)
The Globe at Night campaign to measure the amount of darkness of our skies is conducted this month from March 31 to April 9. Log on to their website www.globeatnight.org for instructions about how to report the visibility of stars according to the amount of light pollution in your location.
March 20th is the day of Equinox when all over the world the length of day and night will be equal.
We hope the rainy season will provide some breaks in the clouds to allow us to enjoy the March night skies.