Skylights Bite Size 27 - April 2013 Night Sky Guide

By ANDY FLEMING

The ringed world Saturn is looking particularly stunning at opposition this month. (Image courtesy, NASA/JPL).

Our night sky guide for April 2013. Highlights this month are Saturn, Venus, The Moon, The Pleiades and The Hyades.

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Skylights Bite Size 27 - April 2013 Night Sky Guide

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Skylights is featured on Solid Gold Sunday each Sunday afternoon at 1425h UTC on 102.4FM in Hartlepool/East Durham, UK and live around the world online at www.radiohartlepool.co.uk

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Show Notes and Transcript

Orion marches into the western evening twilight this month as Leo reaches the Greenwich meridian and the Plough stands overhead. Meanwhile, the glorious ringed world Saturn has just reached opposition; that is on opposite side to the Sun from the Earth.  It is now the sole planet on view during darkness as the others are unfortunately gathering in the Sun's glare at dusk.

Saturn is brighter than it has been for three years, and is at its closest to the Earth at a mere 1.3 billion kilometres distant! From low in the east at nightfall, it passes due south later in the night. It stands above-right of Virgo's leading star Spica, and creeps west during April towards the double star Porrima, whose components are so close together at present that we need a good telescope and perfect conditions to separate them. However, even a modest telescope reveals Saturn’s beautiful ring system which is currently tipped at nine degrees to the Earth.

The Moon lies to the right of Saturn on the evening of April 16th and below Spica on the following night. There will be splendid views of the earth-lit crescent Moon in the lower western sky at nightfall.  This beautiful glow on the part of the Moon unlit by the Sun is called ‘Earthshine’.

Look for the Moon between the Hyades and the Pleiades (or Seven Sisters) open clusters in the Constellation of Taurus the Bull tonight.  Without optical aid and with a dark sky, we might glimpse the instantaneous disappearance, or what astronomers call an occultation, of the fairly dim star 37 Tauri by the Moon. This will occur at around 8.05pm in Hartlepool.

Brilliant Venus hugs the eastern horizon in the pre-dawn and stands eight degrees (or approximately eight lunar diameters) below the Moon on April 30th when Mercury, Jupiter and Mars are still hidden in the twilight below and to Venus's left.

Planck Reveals an Almost Perfect Universe

ByANDY FLEMING

European Space Agency's Plank Satellite.

Acquired by the European Space Agency’s Planck space telescope, the most detailed map ever created of the cosmic microwave background – the relic radiation from the Big Bang – was released today revealing the existence of features that challenge the foundations of our current understanding of the Universe.

The image is based on the initial 15.5 months of data from Planck and is the mission’s first all-sky picture of the oldest light in our Universe, imprinted on the sky when it was just 380 000 years old.

At that time, the young Universe was filled with a hot dense soup of interacting protons, electrons and photons at about 2700ºC. When the protons and electrons joined to form hydrogen atoms, the light was set free. As the Universe has expanded, this light today has been stretched out to microwave wavelengths, equivalent to a temperature of just 2.7 degrees above absolute zero.

This ‘cosmic microwave background’ – CMB – shows tiny temperature fluctuations that correspond to regions of slightly different densities at very early times, representing the seeds of all future structure: the stars and galaxies of today.

Astronomers Discover New Kind of Supernova

ByANDY FLEMING

(Image Credit: NASA)

Supernovae were always thought to occur in two main varieties. But a team of astronomers including Carnegie's Wendy Freedman, Mark Phillips and Eric Persson is reporting the discovery of a new type of supernova called Type Iax. This research has been accepted for publication in The Astrophysical Journal and is available online.

Previously, supernovae were divided into either core-collapse or Type Ia categories. Core-collapse supernovae are the explosion of a star about 10 to 100 times as massive as our Sun. Type Ia supernovae are the complete disruption of a tiny white dwarf.

This new type, Iax, is fainter and less energetic than Type Ia. Although both types come from exploding white dwarfs, Type Iax supernovas may not completely destroy the white dwarf.

"A Type Iax supernova is essentially a mini supernova," says lead author Ryan Foley, Clay Fellow at the Harvard-Smithsonian Centre for Astrophysics (CfA). "It's the runt of the supernova litter."

Young, Hot and Blue!

ByANDY FLEMING

This pretty sprinkling of bright blue stars is the cluster NGC 2547, a group of recently formed stars in the southern constellation of Vela (The Sail). This image was taken using the Wide Field Imager on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile. (Image credit: European Southern Observatory).

The Universe is an old neighbourhood — roughly 13.8 billion years old. Our galaxy, the Milky Way, is also ancient — some of its stars are more than 13 billion years old (eso0425). Nevertheless, there is still a lot of action: new objects form and others are destroyed. In this image, you can see some of the newcomers, the young stars forming the cluster NGC 2547.

But, how young are these cosmic youngsters really? Although their exact ages remain uncertain, astronomers estimate that NGC 2547’s stars range from 20 to 35 million years old. That doesn't sound all that young, after all. However, our Sun is 4600 million years old and has not yet reached middle age. That means that if you imagine that the Sun as a 40 year-old person, the bright stars in the picture are three-month-old babies.

Spiral Beauty Graced by Fading Supernova

ByANDY FLEMING

Spiral galaxy NGC 1637 (Image credit: European Southern Observatory).

About 35 million light-years from Earth, in the constellation of Eridanus (The River), lies the spiral galaxy NGC 1637. Back in 1999 the serene appearance of this galaxy was shattered by the appearance of a very bright supernova. Astronomers studying the aftermath of this explosion with the European Southern Observatory’s (ESO’s) Very Large Telescope at the Paranal Observatory in Chile have provided us with a stunning view of this relatively nearby galaxy.

Supernovae are amongst the most violent events in nature. They mark the dazzling deaths of stars and can outshine the combined light of the billions of stars in their host galaxies.

In 1999 the Lick Observatory in California reported the discovery of a new supernova in the spiral galaxy NGC 1637. It was spotted using a telescope that had been specially built to search for these rare, but important cosmic objects. Follow-up observations were requested so that the discovery could be confirmed and studied further. This supernova was widely observed and was given the name SN 1999em. After its spectacular explosion in 1999, the supernova’s brightness has been tracked carefully by scientists, showing its relatively gentle fading through the years.