CLASS 10TH DAY 2
INTRODUCTION
Origin of the Constellations
Ever since people first wandered the Earth, great significance has been given to the celestial objects seen in the sky. Throughout human history and across many different cultures, names and mythical stories have been attributed to the star patterns in the night sky, thus giving birth to what we know as constellations.
When were the first constellations recorded? Archaeological studies have identified possible astronomical markings painted on the walls in the cave system at Lascaux in southern France. Our ancestors may have recorded their view of the night sky on the walls of their cave some 17 300 years ago. It is thought that the Pleiades star cluster is represented alongside the nearby cluster of the Hyades. Was the first ever depiction of a star pattern made over seventeen millennia ago?
Learning the constellations is fun and easy. Moreover, knowledge of the night sky can provide hours of enjoyment whenever you look up on a clear night.
>>USING A STAR CHART
A star chart is a map of the night sky. With it, you can identify and locate constellations and stars. A typical star chart (see below) shows the relative positions of the stars and their brightness.
Chart of Winter Sky
To use a star chart to identify stars and constellations, you must first find the one appropriate for the time of year you are observing. Notice that the chart above is labeled “Winter.” Picking the chart appropriate for the season is important because as the Earth orbits the Sun, the Sun’s glare hides many of the stars.
Because each night the stars move across the sky, rising in the east and setting in the west, you also need to consider the time of night.
Once you have found the appropriate chart, you need to match it to the sky. First, you should match direction. That is, if you are looking south, you need to orient the chart so it shows the southern sky.
With the correct chart in hand you are now ready to match it to the night sky. Two steps are helpful here. First, look for star patterns. Second notice the relative brightness of stars in the pattern. The chart shows the relative brightness of the stars by their size. Dim stars are shown as tiny dots. Bright stars are shown by big dots.
Watch the documentary “Exploring The Southern Stars” to Explore stars in our galaxy!!👇 👇
Trigonometry
Hope you enjoyed the video..
Important Points
We can easily measure the height of the building and width of the river using trigonometry.
The word ‘Trigonometry’ is derived from three Greek words tri(meaning three), gon(meaning sides), metron(meaning measure).
Mnemonics to remember trigonometric ratios
Here, SOH means ‘sine’ is equal to ‘opposite/hypotenuse’ .
CAH means ‘cos’ is equal to ‘adjacent/hypotenuse’ .
TOA means ‘tan’ is equal to ‘opposite/adjacent’ .
You can easily solve exercise 8.1 from NCERT after attempting the quiz. You can also refer to examples on trigonometric ratios in NCERT and other mathematics textbooks to gain a better understanding of trigonometric ratios.