Babe Among The Stars - September 2009

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Galaxy Babe's column banner, showing a full moon and some little folk looking up at the sky

Mortal as I am, I know that I am born for a day. But when I follow at my pleasure the serried multitude of the stars in their circular course, my feet no longer touch the earth - Ptolemy

Refurbished Hubble

The Hubble Space Telescope (HST), launched on 24 April, 1990, was named in honour of the astronomer Edwin Hubble (1889 - 1953). In almost two decades of service it has provided us with an insight of what is out there in the cosmos that our forefathers could only have dreamed of. In Jan 2002 the star V838 Monocerotis, 20,000 light years away, went nova. The HST captured the dramatic transformation for us. The HST has also provided us with the 'ultra deep field' (HUDF), a 'gap' in the constellation  Fornax. The online 'library' at the NASA website HubbleSite gives you options to search for galaxies, stars, nebulae, the unusual and the exotic. The Hubble Heritage Project website is an archive with a plentiful supply of images and background information on individual objects. It's well worth bookmarking. The HST has now had four major servicings since its launch, each time has involved shuttles taking astronauts to do the (dangerous) repair work. The final servicing mission it just had will hopefully extend its operational life by five years.

Omega Centauri

During its final servicing mission in 2009 the orbiting telescope was fitted with a new Wide Field Camera 3 (WFC3). One of the most spectacular images was that of Omega Centauri, the most luminous and massive globular cluster of the Milky Way. Omega Centauri was named by Johann Bayer in his star catalogue Uranometria of 1603, which is why it has the Greek letter nomenclature (like an individual star). It also has an NGC designation, NGC 5139, and Sir Patrick Moore included it in his catalogue for backyard astronomers as Caldwell 80. Omega Centauri was previously noted by Greek-Egyptian astronomer Ptolemy in his Almagest around 150 AD — but he listed it incorrectly as a star. Who could have guessed then that the cluster actually contained ten million stars? Correctly listed and so 'officially' discovered by Edmond Halley in 1677, he referred to it as a 'luminous spot or patch in Centaurus'.

Arp 185

Another refurbished Hubble image is that of NGC 621, a barred spiral peculiar galaxy over six million light years away in the direction of circumpolar constellation Ursa Minor, the little bear. Also catalogued Arp 185 in the Atlas of Peculiar Galaxies devised by astrophysicist Halton Arp in 1966, the image clearly shows past disruption. What we are looking at in the refurbished Hubble image is how the galaxy looked six million years ago  — it does not look like that 'now'. If we were in the neighbourhood looking at NGC 621 in real time it would be more symmetrical as gravity continues to do its job.

The Butterfly Nebula

Yet another new release is that of the Butterfly Nebula NGC 6302, a two-light-year long planetary nebula, the remnant of a dying star not unlike our own Sun. Astronomers think the same fate lies in store for the Sun after it has run out of hydrogen and swollen to red giant stage. What the resulting planetary nebula will look like is anybody's guess, and it's a real shame humans won't be around to see it in around four or five billion years. It's a nice thought though, that it may end up looking like something as exquisitely beautiful as the Butterfly Nebula.

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