Hubble Space Telescope

Abnormal antennae nearer than we thought

For a long time the beautiful colliding galaxies known as the ‘Antennae Galaxies’, NGC 4038 and NGC 4039, (pictured above) have thought to have been somewhat unusual, a bit abnormal if you will. That’s because astronomers had thought they were between 65 to 100 million light years away. In order for them to be this distant, astronomers reasoned, their current appearance could only be explained by several strange intrinsic properties. To understand why they appeared this way, astronomers argued that they must be undergoing tremendous star formation, with super-massive clusters of stars and even hidden bright X-ray sources. But now new observations from Hubble seem to suggest that we don’t need all these unusual attributes to describe this intriguing merger.

Astronomers from the European Southern Observatory (ESO) using the Hubble Space Telescope’s Wide Field and Planetary Camera 2 have found that actually the Antennae Galaxies are closer than we thought. By observing red giant stars in the tidal tails of the colliding galaxies, the astronomers found that they are in fact about 45 million light years away. The red giant stars nearing the end of their life are good for measuring distances to galaxies; as, at certain points in their life, they have a known brightness which can make them good ‘standard candles’ or distance markers. So we now know that this beautiful merging swirl confirms to our models of galaxy evolution and is in fact how we expect a galaxy merger at this distance to look.

You can read the full story here.

Top image: The Antennae Galaxies by Hubble. Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration. Acknowledgement: B. Whitmore (Space Telescope Science Institute) and James Long (ESA/Hubble).
Lower image: The tidal tail where the red giant stars were studied. Credit: NASA, ESA & Ivo Saviane (European Southern Observatory)

Hubble’s magnificent mergers

OK I admit it. Galaxies are my favourite objects that the Hubble Space Telescope studies and images. But it’s true; there’s something so awesome about the HST images that ooze detail in a way that captures the vast and magnificent nature of these ‘stellar cities’. But it’s not all about the pictures. Hubble has allowed scientists to see the farthest galaxies in the Universe, that also happen to be some of the earliest too. Those observations have given us a real insight into how the galaxies we see today form. Hubble has studied Cepheid variables in distant galaxies too, allowing us to make accurate distance measurements of far off galaxies.

Today the Hubble team have released the most stunning collection of galaxy images I have ever seen. Fifty nine images in total showing many galaxies merging. What’s fascinating is that you can piece together a rough idea of how a merger takes place, out of several images of different ‘collisions’. This isn’t unusual. Astronomers do it all the time. If you wanted to see the lifetime of a Sun-like star you obviously wouldn’t hang around for 10 billion years to watch it from start to finish. What you do is look around the Universe for different Sun-like stars at different points in their life. We can do this now to get at a very basic overview of how a galaxy merger unfolds.

The above image is made from six separate images of differing collisions. Yet put together they show the progression of a galaxy merger. In reality a galaxy collision is a slow and stately affair. In fact during galaxy mergers the stars within the galaxy generally don’t smash together. That’s because of the vast distances between stars; however some stars will ultimately be thrown from the galaxies out into the depths of space.

Over millions of years the gravity of the galaxies begins to twist and shape streams of stars. In the first panel you can see the left hand galaxy is slowly starting to deform as the two galaxies begin to interact. Emerging from the lower left of the left galaxy is a noticeable stream of stars – the first sign that a merger is underway. In the second panel the merger is further along. Here much bigger streams, called ‘tidal tails’, extend out from the galaxies as the two get ever closer. In the third panel the merger is advanced even more with a massive bridge of millions of stars stretching between the two galaxies’ cores. In the last three images the mergers show dramatic twisting and swirling shapes. As the collisions of clouds of dust and gas take place, shockwaves travel through the galaxies. This results in a staggering burst of star formation (note the young blueish stars in the fourth image). Eventually the two galaxies will become one – usually a enormous dusty elliptical galaxy.

To see the full catalogue of the Hubble merger images view the press release here and of course you can watch the latest episode of the Hubblecast about the images here.

First image credit: NASA, ESA, the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration and K. Noll (STScI). Second image credit: NASA, ESA, the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University), K. Noll (STScI), and J. Westphal (Caltech). Third image credit: NASA, ESA, the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University)

Hubble finds methane on an exoplanet

The Hubble Space Telescope has recently found the organic molecule methane on the extrasolar planet HD 189733b. Here’s a section of the ESA press release below.

“Under the right circumstances methane can play a key role in prebiotic chemistry – the chemical reactions considered necessary to form life as we know it. Although methane has been detected on most of the planets in our Solar System, this is the first time any organic molecule has been detected on a world orbiting another star”

With an atmospheric temperature of around 900 degrees there certainly isn’t going to be life (at least as we know it) on HD 189733b. The importance of this observation is more that it is “proof that spectroscopy can eventually be done on a cooler and potentially habitable Earth-sized planet orbiting a dimmer red dwarf-type star” says Mark Swain who led the team that made the discovery at NASA’s Jet Propulsion Laboratory (JPL).

I saw this exciting news come in when I was working with the Hubble group in Germany and I began scripting a Hubblecast to cover the result. To see the finished piece visit the ESA Hubblecast no.14 page here.

Above: An artist’s impression of HD 189733b around its parent star.
Credit: Credit: ESA, NASA and G. Tinetti (University College London, UK & ESA)

Lecture reminder

Just a reminder to those of you in the south-west UK that on Thursday evening ( 20.03.08 ) I will be giving a lecture to the Torbay Astronomical Society. The title of the talk is “Not just pretty pictures – the science behind Hubble’s greatest images”.

All are welcome and the talk starts at around 7:30pm at Torquay Boys’ Grammar School. For information on how to get there and visitor fees see the TAS website.

Hubble finds a COSMOS of gravitational lenses

Hubble Space Telescope scientists have recently announced that they have discovered 67 gravitational lenses lurking in images taken for a survey of galaxies. Hubble has spotted the gravitational lenses as part of the COSMOS survey into large scale structure of the Universe. The scientists have found some really cool lenses like the ‘Einstein Ring’ on the left. The results show that if the number of lenses seen by Hubble in this survey is typical of large sections of the sky then there could be hundreds of thousands of this type of gravitational lens across the whole night-sky!

This is one of the press releases that I worked on whilst in Germany last year. If you want to read the full story check it out on the ESA Hubble website here. As an aside it’s great to see Atlantis landed safely. Columbus is now installed on the International Space Station which is now looking incredible. The Columbus module is the one jutting out to the right hand side of the line of vertical modules in that image.

Above: This incredible ‘Einstein Ring’ captured by the Hubble Space Telescope is the product of a rare line-of-sight alignment of massive lensing galaxy, background galaxy and Hubble itself.

Credit: NASA, ESA, C. Faure (Zentrum für Astronomie, University of Heidelberg) and J.P. Kneib (Laboratoire d’Astrophysique de Marseille)

Galaxy eating monster reveals its secrets

A monster so huge it is capable of slowly devouring whole galaxies at a time. Sounds incredible doesn’t it? But that is what astronomers working on the Hubble Space Telescope think that the giant elliptical galaxy NGC 1132 is – a cosmic cannibal if you will. In this stunning new image from the NASA/ESA Hubble mission astronomers are seeing the vast hulk of a galaxy, 320 million light years distant, whose past is much darker than it might at first seem. That’s because whilst the stunning elliptical in Hubble’s new image looks serene and peaceful, it is in fact the aftermath of gravitational dance which saw the death of many smaller galaxies; and it all clinches on how astronomers think galaxies form.

One of the most popular current theories is that giant galaxies like NGC 1132 are made from the merger and assimilation of lots of smaller galaxies. Over time these vast elliptical giants like NGC 1132 emerge as enormous conglomerations of stars. Sounds all very vicious but in fact this galactic cannibalism is probably quite commonplace in the Universe if our theories of galaxy evolution are correct. Indeed Hubble scientists believe that our own Milky Way may have been partial to devouring the odd dwarf galaxy which strayed too close to it.

Yet the one question that we are bound to ask is how do we know? Well the answer comes from two main lines of evidence. The first is globular clusters. Galaxies like the Milky Way are home to globular clusters which reside above and below the disc of the galaxy. These are extremely ancient (and fairly compact) balls of stars and are useful tools for studying the evolution of stars. If you know where to look you can spot them through a small telescope on a clear night.

When Hubble scientists looked at NGC 1132 they noticed something interesting. A vast collection of globular clusters around the massive galaxy. They believe that what they are seeing are the globular clusters of NGC 1132’s victims – whole globular clusters that have been cast away as NGC 1132 merges with their parent galaxies. Since the stars in globulars are packed much more densely than the normal stars in the unfortunate galaxies their collective gravity holds the globular together. This means they can survive the huge gravitational disruptions involved in the merger and breakup of their parent galaxy.

The second piece of evidence comes from material we can’t see in this image – dark matter. Observations have shown that NGC 1132 is surrounded by a truly enormous cloud of dark matter. The dark matter cloud is thought to hold quantities of dark matter that are normally found residing in whole galaxy clusters of between ten and a few hundred galaxies – not one galaxy as seen with NGC 1132! NASA’s Chandra X-ray observatory was able to show that the galaxy is also surrounded by a glow from X-rays emitted from hot gas – about 120,000 light years in diameter – roughly the size of a galaxy cluster, giving yet more support to the idea that NGC 1132 is the result of the merging of one entire galaxy cluster.

If you want to find about more about this fascinating new result visit the Hubble website and whilst you’re there check out the latest Hubblecast.

Above: NGC 1132 from the HST
Image credit: NASA, ESA and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration. Acknowledgment: M. West (ESO, Chile)

Book news (part I)

I achieved a milestone today in that I have finally got all the necessary image permissions for my book. The images are really cool and I can’t wait to submit my manuscript later in the year. Now I just have to finish the text…so it’s back to the word processor for me! In the mean time check out this incredible new image from Hubble and if you want to find out more about what’s going on in the image download the Hubblecast!

“Hazy red sunset on extrasolar planet”

Here is the latest release from the ESA/Hubble office that I have been working on. Hubble astronomers have used the orbiting space observatory to study the atmosphere of the extrasolar planet HD189733b (a number I can’t seem to get out of my head having written it so many times over the past few weeks). This world had previously been observed by the Spitzer Infrared Space Telescope but now Hubble has shown that it actually has a layer of hazes in its upper atmosphere made up of tiny grains of (probably) silicates, iron and aluminum oxide. To read the full press release visit the ESA/Hubble website and of course there is the latest episode of the Hubblecast out where Dr J talks to the head of the ESA/Hubble group Dr Bob Fosbury about this amazing world.

Image credit: ESA, NASA and Frédéric Pont (Geneva University Observatory)

Behind the scenes at Hubble

The latest Hubblecast is out! Episode number 10 explores behind the scenes of the NASA/ESA Hubble Space Telescope.

“We live in a Universe of unimaginable scale and almost incomprehensible beauty. How is the light from the Universe transformed into the images that have inspired generations by making the Universe come to life?”

If you have ever wondered how the incredible images from Hubble are made then this Hubblecast is for you!

Image credit: NASA, ESA, and the Hubble Heritage Team STScI/AURA)-ESA/Hubble Collaboration. Acknowledgement: B. Whitmore ( Space Telescope Science Institute) and James Long (ESA/Hubble).