Weird and Wonderful of Universe: Stars in The Sky

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A protostar continues contracting and heating up. As the nebula disperses, it continues in its own orbit.

2 Main Sequence

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The star is hot enough to sustain nuclear reactions in its core.

3 Death

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This begins when hydrogen in the core runs out. It takes one of three courses depending on the star’s size.

A medium star expands into a red giant, cools and shrinks into a white dwarf, then cools further to form a black dwarf.

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A large star explodes as a supernova, then collapses under its own gravity into a neutron star. Some neutron stars rotate.

A giant star explodes as a supernova, then collapses completely, forming a black hole.

Hertzsprung-Russell Diagram

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This graph is used to work out a star’s type and age. The star’s surface temperature (calculated from the colour of the light it emits) is plotted against its brightness, and the star is classified according to where it falls on the graph. Main sequence stars, such as our Sun, fall in the band across the middle.

Telescopes

Different types of telescope are used to study the stars:

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Optical telescopes use either lenses to refract or mirrors to reflect distant objects. The world’s largest reflecting telescope is in Zelenchukskaya, Russia. Its biggest mirror weighs 70 tonnes and is 6m (20ft) wide.

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Radio telescopes use giant dishes- or an array of linked dishes-to pick up radio waves. At 305m (1000ft) wide, Arecibo in Puerto Rico is the world’s largest dish telescope.

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Space telescopes placed in orbit observe stars without interference form the Earth’s atmosphere.

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Listening to the stars: The massive dish of the Parkes radio telescope in NSW, Australia.

Supernovae – Stellar Recyclers

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A supernova is the explosive death of a giant star.

The last one seen was in 1987 in the Large Magellanic Cloud. Elements heavier than iron, such as gold, are created in the intense heat of a supernova. They are scattered as interstellar dust, from which new stars and planets form.

Variations

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Pulsar: A spinning neutron star that sends out a regular pulse of radio waves.

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Binary star: Two stars, held together  Inby gravity, that circle around each other. Optical binaries are stars in the same line of sight that appear linked but are actually separate.

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Variables: Star that display fluctuating brightness.

Star Songs

Musicals invoking the stars include: Singin’ in the Rain (1952), with Gene Kelly and Debbie Reynolds singing ‘You Are My Lucky Star’; Pinocchio (1940), with ‘When You Wish Upon A Star’; and Paint Your Wagon (1969) with Lee Marvin singing ‘Wand’ rin’ ‘Star’.

Well Known Stars

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Star                                Claim to Fame

Pistol Star                    – Brightest known star (10 million times more powerful than the Sun)

Sirius A            – Brightest-looking star in night sky; 24 times brighter that the Sun. Also known as the Dog Star

Proxima Centauri         – Nearest (4.23 light years). Nexy nearest are Alpha Centauri A and B

Betelgeuse                  – One of the largest known  (diameter 1000 million km (620 million miles)

Shurnarkabtishashutu – Longest name Arabic for “under the southern horn of the bull”

Hydes (300 stars)        – Nearest star cluster. c.150 light years away on Taurus constellation

PSR B1937+214           – Fastest spinning pulsar (642 revolutions per second)

Weird and Wonderful

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The first researchers to spot pulsars gave them the nickname LGMs (Little Green Men), because these stars emit signals so regular and precise, it is as if they were produced by an intelligent alien life-form.