Stars and Constellations

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Email:raghua4@gmail.com

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Our Family : Solar System

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Earth’s axis of rotation is inclined to its orbital plane by 23.5°, which causes the seasons.

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They are not related to Earth’s distance from the sun. In fact, Earth is slightly closer to the sun in (northern-hemisphere) winter than in summer.

Light from the sun

Steep incidence → Summer

Shallow incidence → Winter

The Seasons are only caused by a varying angle of incidence of the sun’s rays.

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The Celestial Sphere (R UÉÆà ¼À)

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•Geographic latitude l (northern hemisphere), you see the celestial north pole l degrees above the horizon.

•If l = 90⁰, then north pole will coincide the zenith.

l

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India is in the northern hemisphere

MysoreLatitude 12.3024° NLongitude 76.6386° E

The Celestial north pole

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The Celestial South Pole is not visible from the northern hemisphere.

Celestial North Pole

12.300

Horizon

North South

Horizon

Mysore: l ≈ 12.3024º N

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The Circling Sky Earth rotates from west

to east. The celestial sphere

appears to rotate east to west.

Apparent path of a particular star

In the Northern Hemisphere, stars near the North Celestial Pole are always above the horizon. Therefore, they are visible all time and they are called Circumpolar Stars

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Different sets of constellations are visible in northern and southern skies.

The Altitude of the celestial pole (Polaris) = your latitude

Constellations £ÀPÀëvÀæ gÁ²UÀ¼ÀÄ

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In ancient times,

constellations only referred

to the brightest stars that

appeared to form groups, representing mythological

figures.

Constellations £ÀPÀëvÀæ gÁ²UÀ¼ÀÄ

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Today, constellations are well-defined regions on the sky, irrespective of the presence or absence of bright stars in those regions.

A constellation is any one of the 88 areas into which the sky is divided

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How can we identify constellations in the night sky?

The use of a star chart can help us!

A STAR CHART is a map of the stars in the night sky.

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Big DipperBig Dipper

Big dipper is a constellation which is a part of Ursa Major, the Great Bear. This is visible in the Northern Hemisphere all year long.

Pointer Stars

The Dome of the Sky

MANDYALatitude 12.52° NLongitude 76.9 ° E

Angular size of moon ~ ½ o Angular distance between the “pointer stars” ~ 5o

To Polaris

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Ursa MinorUrsa Minor

Arundhathi= Vasishta

Saptarishi Mandala

Kratu

Brighu

Modern names1.Atri2.Bharadvaja3.Gautama4.Jamadagni5.Kashyapa6.Vashista7.Vishvamitra

Counter-Clockwise Rotation

Clockwise Rotation

Northern Hemisphere Southern Hemisphere

The Altitude of the celestial pole (Polaris) = your latitude

Apparent Motion of The Celestial Sphere

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Orion Not a circumpolar constellation, but a seasonal

constellationBetelgeuseBetelgeuse,, the right arm of Orion, glows with a dull red. RigelRigel,, in the opposite corner of the constellation, is blue and much brighter.

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Views of Orion from Tasmania (Australia) and Iran (Asia)

Northern hemisphere

Southern hemisphere

Orion from India

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Ecliptic Constellations & Zodiac Signs A band of 12 constellations around the

sky entered on the ecliptic (apparent path of the sun on the earth as the earth revolves around it).

Born under the sign of…

Aries Libra

Taurus

Scorpio

Gemini

Sagittarius

Cancer

Capricorn

Leo Aquarius

Virgo Pisces

gÁ² (ªÀiÁ¸À)

gÁ² (ªÀiÁ¸À)

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Libra vÀįÁ (D±ÀéAiÀÄÄd)

Taurus

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Scorpio ªÀȲÑPÁ (PÁwÃðPÀ)

Gemini

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Sagittarius

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Cancer

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Capricorn

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Leo ¹AºÀ (±ÁæªÀt)

Aquarius PÀÄA¨sÀ (ªÀiÁWÀ)

Virgo PÀ£Àå (¨sÁzÀæ¥ÀzÀ)

Pisces «ÄãÀ (¥Á®ÄÎt)

Ecliptic Constellations & Zodiac Signs

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Hindu Calendar Rashi

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Ecliptic Ecliptic ConstellationsConstellations

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1. What is changing at the same (annual) timescale that we are observing the changing zodiac?

Earth’s revolving.

2. Do the constellations appear to change positions in the night sky as Earth travels around our Sun throughout the year?

YES

3. Are the constellations themselves moving?

NO

4. What causes this apparent change in positions?

As Earth orbits the Sun, our perspective changes

5. Do all stars appear in different positions at different times of the year?

All except Polaris

6. Why is Polaris the only star that appears “fixed”?

Earth’s axis points to Polaris

Constellations

Milky way Galaxy. We are Nothing?...!

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