Starship Asterisk*

[b][i]Credit: ESO/J. Colosimo[/i][/b]

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This beautiful image taken at ESO's Paranal Observatory shows the four Auxiliary Telescopes of the Very Large Telescope (VLT) Array, set against an incredibly starry backdrop on Cerro Paranal in Chile.

The Auxiliary Telescopes are each 1.8 metres in diameter and work with the four 8.2-metre diameter Unit Telescopes to make up the world's most advanced optical observatory.

The telescopes work together to form the VLT Interferometer (VLTI), a giant interferometer which allows astronomers to see details up to 25 times finer than would be possible with the individual Unit Telescopes.

Hanging over the site are the prominent Small and Large Magellanic Clouds, visible only in the southern sky. These two irregular dwarf galaxies are in the Local Group and so are companion galaxies to our own galaxy, the Milky Way. ...

[b][i]Credit: ESA/Hubble & NASA Acknowledgement: A. Aloisi (STScI) and N. Rose[/i][/b]

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The bright streak of glowing gas and stars in this NASA/ESA Hubble Space Telescope image is known as PGC 51017, or SBSG 1415+437. It is type of galaxy known as a blue compact dwarf.

This particular dwarf is well studied and has an interesting star formation history. Astronomers initially thought that SBS 1415+437 was a very young galaxy currently undergoing its very first burst of star formation, but more recent studies have suggested that the galaxy is in fact a little older, containing stars over 1.3 billion years old.

Starbursts are an area of ongoing research for astronomers — short-lived and intense periods of star formation, during which huge amounts of gas within a galaxy are hungrily used up to form newborn stars. ...

[b][i]Credit: ESO/Babak Tafreshi (TWAN)[/i][/b]

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This image shows the dome of the Danish 1.54-metre telescope that has been in operation at La Silla Observatory since 1979.

The telescope has been involved in several breakthrough astronomical observations including the discovery of merging neutron stars as the possible origin of gamma-ray bursts (eso0533) and finding an exoplanet only five times more massive than the Earth (eso0603).

Above the telescope, our home galaxy the Milky Way stretches across the sky with the bright central bulge aligned with the dome of the telescope.

In the background to the right you can spot the dome which once held the MarLy 1-metre telescope. The telescope saw first light in 1996 and was decommissioned in 2009. Before the MarLy, this dome hosted the 40-centimetre Grand Prisme Objectif, a photographic astrograph. In front of the MarLy dome, the enclosure of the small Marseille 0.36-metre telecope is visible.

[b][i]Credit: ESA/Hubble, NASA[/i][/b]

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This NASA/ESA Hubble Space Telescope image shows an edge-on view of the spiral galaxy NGC 5023. Due to its orientation we cannot appreciate its spiral arms, but we can admire the elegant profile of its disc. The galaxy lies over 30 million light-years away from us.

NGC 5023 is part of the M51 group of galaxies. The brightest galaxy in this group is Messier 51, the Whirlpool Galaxy, which has been captured by Hubble many times. NGC 5023 is less fond of the limelight and seems rather unsociable in comparison — it is relatively isolated from the other galaxies in the group.

Astronomers are particularly interested in the vertical structure of discs like these. By analysing the structure above and below the central plane of the galaxy they can make progress in understanding galaxy evolution. Astronomers are able to analyse the distribution of different types of stars within the galaxy and their properties, in particular how well evolved they are on the Hertzsprung–Russell Diagram — a scatter graph of stars that shows their evolution.

NGC 5023 is one of six edge-on spiral galaxies observed as part of a study using Hubble’s Advanced Camera for Surveys. They study this vertical distribution and find a trend which suggests that heating of the disc plays an important role in producing the stars seen away from the plane of the galaxy.

In fact, NGC 5023 is pretty popular when it comes to astronomers, despite its unsociable behaviour. The galaxy is also one of 14 disc galaxies that are part of the GHOSTS survey — a survey which uses Hubble data to study galaxy halos, outer discs and star clusters. It is the largest study to date of star populations in the outskirts of disc galaxies.

The incredible sharp sight of Hubble has allowed scientist to count more than 30 000 individual bright stars in this image. This is only a small fraction of the several billion stars that this galaxy contains, but the others are too faint to detect individually even with Hubble.

Credit: ESO/Baback Tafreshi (TWAN)

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With all 66 of their backs turned to the constellation of Orion, the antennas of the Atacama Large Millimeter/submillimeter Array (ALMA) sit high on their perch on the Chajnantor Plateau in the Chilean Andes.

Illustrating nicely why this spot was chosen for the array is an impressively clear view of the Orion Nebula — otherwise known as Messier 42. It lies in the centre of the image, with the dazzling red of the star Betelgeuse, otherwise known as Alpha Orionis, off to the right. These are two of the most impressive sights in the night sky.

Betelgeuse is a red supergiant and notable for being a likely candidate amongst the stars in our galaxy to become a supernova in the near future. Near future on a cosmic scale — a recent report suggests in around 100 000 years, which is a mere galactic blink. When this does happen, it will become the brightest object after the Moon in our night sky.

ALMA itself, however, is looking deeper into the cosmos to study the oldest and coldest of places by detecting light at millimetre and submillimetre wavelengths. Its antennas can be moved about the site independently and they search the skies in perfect synchrony, using a process known as interferometry to achieve results that would otherwise require a single telescope of about 14 000 metres in diameter.

[b][i]Credit: NASA, ESA; Acknowledgement: A. Riess (STScI)[/i][/b]

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This NASA/ESA Hubble Space Telescope image shows the spiral galaxy NGC 3021 which lies about 100 million light-years away in the constellation of Leo Minor (The Little Lion).

Among many other types of stars, this galaxy contains Cepheid variable stars, which can be used work out the distance to the galaxy. These stars pulsate at a rate that is closely related to their intrinsic brightness, so measurements of their rate of pulsation and their observed brightness give astronomers enough information to calculate the distance to the galaxy itself.

Cepheids are also used to calibrate an even brighter distance marker, that can be used over greater distances: Type Ia supernovae. One of these bright exploding stars was observed in NGC 3021, back in 1995.

In addition, the supernova in NGC 3021 was also used to refine the measurement of what is known as the Hubble constant. The value of this constant defines how fast the Universe is expanding and the more accurately we know it the more we can understand about the evolution of the Universe in the past as well as in the future. So, there is much more to this galaxy than just a pretty spiral.