March Night Skies
March Highlights:
· Saturn is back in the evening skies
· Saturn is retrograde (moving backward)
· Mars shows movement across the sky
· Direction pointers up in the sky
· Globe at Night and light pollution
· Milky Way best viewed this month
· Orion is a prominent constellation
· Equinox on 20th March
· International Space Station on 20th and 21st
· Hubble Space Telescope (HST) on 9th and 10th
The lunar eclipse last month disappointed many in Tanzania due to the heavy cloud cover coming from cyclonic activity of Cyclone Ivan that caused a lot of damage in Madagascar. Astronomers will have to contend with the changing global climate when observing from earth. Though the next total lunar eclipse is in December 2010, it will not be visible from Tanzania. So it will not be until June 15 2011 that Tanzanians will get another chance. However, we can still witness the wonders of our world later this year when a partial lunar eclipse occurs on 16th of August.
Saturn is Back
Saturn is back in the evening sky and we will follow the progress of this beautiful ringed planet for the next six months. Though not too brilliant, its sharp steady stare makes it easy to identify it in the east. Sitting in the lap of Leo (the Lion), notice how far Mars is from Regulus, the brightest star at the neck of Leo. The gap between Saturn and Regulus will decrease by half as Saturn shifts slowly in retrograde (i.e. opposite, east to west) movement. Regulus can be identified as the dot in the question mark shape that forms the head of Leo.
Mars
Meantime, Mars moves quickly and normally (i.e. west to east across the background stars) as it closes the gap with its nearby star Mebsuta in Gemini (see map). They will come closest to within quarter of a degree (half a finger apart) by 30th March. Retrograde movement occurs for short periods during a planet’s journey across the skies. It is an apparent backward motion that is seen in the skies when the earth overtakes a planet in its orbit around the sun.
Finding direction at night using the direction pointers
The month of March also ushers in the pointers that point out the poles. The South Pole can be located using the Southern Cross, which is up in the south east by 8 pm (see map). Early in the evening, the longer diagonal of the kite shaped constellation is parallel to the horizon. This is because we are 6 degrees south of the equator and the South Pole point in the sky is 6 degrees above the horizon. If you want to find the south direction you will have to wait a couple hours when the Southern Cross will have swiveled up and its longer diagonal can be extended to the south point in the horizon. In the north, the edge stars of the Big Dipper (see map) point towards the North Pole. To check if you have located the poles accurately, point one arm toward the north you located and point the other arm south. If you have located the two poles accurately your arms will be outstretched.
Globe at Night
Stargazers, young and old, students and teachers, amateur and professional astronomers are all currently taking part in a global experiment to document and understand the amount of light pollution in our night skies. Between February 25 and March 8, you can also go out into the night to determine how many stars can be seen (or not seen!). The more the light there is around you, the fewer the stars you will see. And I am not talking about the lights that shine around you – those will certainly blind you and you will see hardly anything. What the experiment is about is the amount of light coming from the sky. Any light from the bulbs that unnecessarily and wastefully point up into sky gets scattered (reflected back) by the molecules and particles in the atmosphere. This makes the atmosphere brighter so you can’t see the dimmer stars. When traveling upcountry, you will have seen the breathtaking skies and notice the difference between that and the stars you can see in a town or city.
Join this exciting project, called “The Globe at Night” to understand how bad the light pollution is at your location. You will also be able to make an impact on how we use our lights, and contribute to the protection of our beautiful dark skies. Go to website http://www.globe.gov/GaN/ and follow the few simple instructions. You will be guided to how you can locate the Orion constellation (which is well up in the eastern skies by 8 pm. Refer to the sky map). Match the stars that you see with several star charts given in the website that show the constellation in various light conditions. Report your observations using the form provided in the website. Note that the report form works best with the Internet Explorer browser.
The Milky Way
The Milky Way is a band of dense collection of stars, nebulae and interstellar dust that stretches across the March evening sky. It is marked by the Southern Cross, Canis Major (Big Dog), Orion, Taurus (Bull) and Perseus (see map). The Milky Way is actually a galaxy which is a huge collection of 100 billion stars. Our Sun is an average star among those billions. From earth we see the Milky Way as a narrow strip because we our galaxy is a flat, plate-shaped collection of stars. When we are looking at the band, we are observing the stars in our galaxy along its flat plane. If you turn your head away on either side of the band you see very few starts because you are watching the flat galaxy along its slender thickness. The true glory of the Milky Way can only appreciated away from the city lights where it becomes a truly milky band with distinctly fewer stars on either side.
Besides the myriads of stars, the Milky Way galaxy contains star clusters, and interstellar matter in diffuse nebulae. Young stars are continuously born within these nebulae due to the gravitational force which acts for billions of years over huge distances to pull together the wispy interstellar matter. Gravitational force also keeps together our Milky Way galaxy by pulling towards the massive black hole at the centre. The enormous system is 100,000 light years across (that would be the distance that would be covered in 100,000 years while traveling at the speed of light - 300,000 km per second). Until recently, our galaxy’s thickness was believed to be only a few thousand light years, but recent measurements show that it is actually 12,000 light years thick. All the galactic stars and material are contained in spiral arms, which rotate around the centre, making one revolution every 250 million years.
Bright Stars and Constellations
We in Tanzania are very well positioned to view the best of the southern skies because there is a far higher concentration of stars than in the north. Besides the Milky Way we can see the two brightest stars in the sky, Sirius and Canopus which you can locate using the star map. The constellation that is easiest to recognize is Orion with it huge rectangle taking up a large part of the over head sky around 8 pm. Once you have oriented the sky map with sky using these stars and constellations as pointers and the compass direction shown on the map, you will be able to follow the rest of the constellations and stars marked on the map. The middle part of Orion is an area known as the ‘sword of Orion’ contains the most beautiful collection bright interstellar dust or nebulae and even with the naked eyes you can see a patch of nebulous cloud one of them known as the ‘horse head nebula’. Of course you would need a telescope to make out such a horse shape.
There are plenty of deep sky objects that you can observe with the naked eyes. Among these is the Pleiades star cluster, also know as ‘seven little sisters’. It is an open cluster of newly formed stars embedded within bright interstellar matter where new stars are still forming. Another similar cluster is the Hyades cluster in Taurus Constellation near its red giant star Antares. An area close to the Southern Cross contains material which is not bright so we see a patch of darkness within a region of bright stars, hence its name the ‘coal sack’.
Moon
The moon is New on 7th March and Full on 21st. On 12th March, a crescent Moon cradles the Plaiedes star cluster, with the two separated by less than two degrees (3 fingers apart). On 14th the moon will be in First Quarter phase and will also be closest to Mars. By 19th, an almost full moon will be close to Saturn within two and a half degrees. The Last Quarter moon will be on 29th March.
Eqinox
20th March is the day of vernal equinox when the sun will be directly above the equatorial plane of the earth. Day and night will be equal lengths throughout the world that day.
Satellites
The US Navy managed to blast away a failed satellite that was out of control using a missile fired from a navy ship. Perhaps they can also clear up the debris of many other dead satellites that have completed their missions.
International Space Station (ISS) an be seen this moth on March 20 and 21. On 20th it begins to rise in the south a few minutes before 7 pm and will rise to about 20 degrees altitude and will set a few minutes later in the east. On 21st it will be seen at a quarter past seven and will be much brighter as it rises higher to 55 degrees altitude in the south west. It will set in the north 5 minutes later. The Hubble space telescope is best seen on 9th and 10th March a few minutes before seven on both days. It will rise in the west, passing south west and sets in the south east 10 minutes later. On 9th it will be much brighter because it will rise to almost overhead skies. For more up to date times and other satellites, visit http://heavens-above.com. Remember to enter the latitude and longitude of you location, or 6 degrees south and 30 degrees east for Tanzania in general.
**End**