Tag: Stars

The death of stars

Most celestial events unfold over thousands of years or more, making it impossible to follow their evolution on human timescales. Supernovas are notable exceptions, the powerful stellar explosions that make stars as bright as an entire galaxy for several days. Although they are very rare – only a few such explosions take place every century in a typical galaxy – supernovas can be seen with the naked eye if they are reasonably nearby. In fact, when supernovas were discovered they were thought to be new stars appearing in the sky – ‘nova’ means new in Latin. Astronomers have recorded supernovas long before a theoretical understanding of these events as stellar explosions was developed in the 20th century. The most ancient documented record dates back to 185 AD, when Chinese astronomers saw a ‘guest star’ that remained visible for several months, in the vicinity of the two stars Alpha and Beta Centauri. The material ejected during these explosions sweeps up gas and dust from the surroundings, creating picturesque supernova remnants that can be observed long after the explosion. Modern astronomers believe that the object shown in this image, the supernova remnant RCW 86, is what remains of the supernova that was discovered in 185 AD. The blue and green glow at the edges of the bubble represents X-ray emission from hot gas, heated to millions of degrees by shock waves generated after the explosion. The diffuse red glow marks infrared emission from warm dust in the interstellar medium around RCW 86. Sprinkled across the image, in yellow, are young stars that shine brightly at infrared wavelengths. This image combines X-ray data from ESA’s XMM-Newton and NASA’s Chandra X-ray Observatory (combined to form the blue and green colours) with infrared observations from NASA’s Spitzer Space Telescope and Wide-Field Infrared Survey Explorer (yellow and red). The supernova remnant RCW 86 is some 8000 light-years away.

Stars inevitably run out of fuel to burn in the nuclear fusion reactions that burn in their cores and when this happen there are a number of spectacular events that occur in their death throes. As a star goes through its main sequence stage it burns hydrogen into helium through nuclear fusion. As it starts …

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What are the different types of stars?

Light Spectrum of our Sun. Credit: N.A.Sharp, NOAO/NSO/Kitt Peak FTS/AURA/NSF

In my last few posts I have talked mainly about the Sun, our closest star but what other types of star are there? Clearly by looking at the Hertzsprung-Russell diagram there are different types; cooler, dimmer smaller stars to brighter, hotter and massive stars. Astronomers class the stars according to a property called it’s Spectral …

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H-R Diagrams

I described stars in my last post and I talked about two that are different colours; Rigel and Betelgeuse in the constellation of Orion. Rigel is a blue super giant and Betelgeuse is a red super giant but what is the Sun, how do we classify stars as super giants and what other types of …

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What are Stars?

The constellation of Orion

Stars are all those little pin points of light in the night sky that slowly move around the sky throughout the year, but what exactly are they? Stars are the furnaces of the universe; a single star is a huge collection of matter that is gravitationally pulling itself together into a sphere and this gravitational …

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What did the Sun ever do for us?

The Sun. That great big ball of fire in the sky. But what did it ever do for us? At the simplest level the Sun gives us light and warmth. As humans this is what we need to survive. It provides us with day and night as it lights up the day side of the …

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Populations of Stars

How old are stars? Stars are categorised into three groups:- Population III – The oldest Population II Population I – The youngest (Our Sun) Population III are the oldest stars that are thought to have burned close to the big bang at around 400 Million years afterwards. In the time since recombination (~380,000 years after …

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Element Formation in Stars

We are all made of star stuff, the left of detritus from stars that exploded long ago. Nearly all the elements in the solar system, Milky Way and beyond were created in the extreme conditions at the centre of stars. Ultimately you and I are made from this star stuff. Were do the elements come …

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