Hubble Space Telescope

SM4: peering over the shoulders of giants


With the Space Shuttle Atlantis (STS-125) and her crew now waiting for the right conditions to come home and land after repairing and upgrading Hubble, I thought now would be a good time to look back at what has happened over the past ten days or so. Servicing Mission 4, to Hubble, has been nothing short of spectacular – with risky spacewalks, dramatic repairs and a real sense of cutting edge space exploration. Spaceflight author Andrew Chaikin has recently blogged on why he felt “amazed, inspired–and grateful” watching the Hubble Servicing Mission unfold, and it’s really worth reading his thoughts here. This mission has been especially exciting and indeed has been different – both in terms of the added public interest and in how the community of space and astronomy enthusiasts has followed along.


To me this has been largely, if not wholly, because of the constant stream of images, tweets, blogs and live video streams that NASA has been sending out on a frequent basis. With video cameras in the astronauts’ helmets we’ve been able to literally peer over their shoulders and watch live what they were doing up there on Hubble. This really hit home to me, a couple of days ago, when I saw a video that was filmed in the cockpit of the Shuttle Atlantis, as the astronauts parted ways with Hubble. The video gives a real sense of what it’s like to be working on the deck of the Shuttle and, as Phil says, there’s something about the clear audio which greatly adds to this. It’s a must see. Stuart has the story of the video here.

For my part I’ll be remembering and reliving the exploits of this incredible mission through the many pictures taken by the astronauts. I’ve put a few of my favourites in this post, but there are hundreds out there. Click on the images, in the post, to get the NASA high res. versions. And why not let me know what your favourites are in the comments below, or on my Twitter feed.


All images courtesy NASA.

Hiding Ganymede and an extrasolar connection

jupiterhubble1Jupiter & Ganymede. Credit: NASA, ESA, and E. Karkoschka (Univ. of Arizona)

Jupiter might not exactly be well placed for observing from the Northern Hemisphere this year, due to its relatively low altitude, but all is not lost. NASA have just released this beautiful, “close to natural” colour, image from the Hubble Space Telescope. It shows the Galilean moon Ganymede beginning to disappear behind the southwestern part of Jupiter’s enormous disc. You can watch a video of Ganymede disappearing behind Jupiter (over the course of two hours) on the NASA Hubble site. The images were taken in April 2007 and, as can be seen in the crop of the main image below, they show the huge rocky and icy moon in quite some detail.

ganymedehubbleGanymede disappearing. Credit: NASA, ESA, and E. Karkoschka (Univ. of Arizona)

Compare this new Hubble image of Ganymede to the one (below) from the New Horizons mission en-route to Pluto and you get a feel for just how good Hubble’s resolution is! The bright splodge towards the upper middle of Ganymede’s terminator in the New Horizons image is a huge crater known as Tros and it’s clearly visible, as a bright white spot, in Hubble’s shot as well. There are features smaller than Tros visible in the Hubble image too. That’s not to say that the New Horizons image isn’t any good. Far from it, it’s amazing — it’s just that Hubble is one impressive instrument!

newhorizonsganymedeA view of Ganymede from the New Horizons spacecraft as it whisked by.
Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

Anyway I’m moving a little away from my point. Not only is Hubble’s new shot a wonderful picture, full of intriguing details on both Jupiter and Ganymede (especially the high resolution versions), it also illustrates nicely how astronomers have been able to study Jupiter’s atmosphere. The method astronomers have been using to do this is also similar to how astronomers ‘probe’ the atmospheres of distant exoplanets. Ganymede is reflecting light from the Sun back towards us (that’s how we can see it). That light passes through the upper reaches of Jupiter’s atmosphere, towards us, as Ganymede disappears behind the limb of the huge planet. By spectroscopically studying the chemical fingerprints stamped on this light, by Jupiter’s atmosphere, astronomers can then work out important properties and compositions of the gases in this part of the Jovian atmosphere.

exoplanetlimbAn illustration showing light passing through the atmosphere of an exoplanet.
Credit: ESA, NASA and Frederic Pont (Geneva University Observatory)

In a very similar way, when studying exoplanets, astronomers have been able to detect the chemical signatures of interesting molecules in exoplanetary atmospheres, that have been stamped on the light from the exoplanet’s parent star. So it isn’t just in studying the gas giants of our own Solar System that this versatile astronomical technique is used. It will be interesting to see what these observations from Hubble tell us about Jupiter’s atmosphere. If they are anything like the results seen from studying the atmospheres of distant exoplanets, they will be very interesting indeed.

Hubble, Keck and Gemini directly image distant exoplanets

An artist’s impression of Formalhalt b orbiting its parent star.
Credit: ESA, NASA and L. Calçada (ESO)

In two separate papers published in the journal Science today, astronomers announced that they have directly imaged several extrasolar planets around other stars. One team used Hubble to find an approximately 3 Jupiter mass planet orbiting the star Formalhalt, whilst another team used Keck and the Gemini telescopes to find a family of planets around the star HR8799. Hubble studied Formalhalt in visible light and was able to make what can only be described as a truly remarkable image (see below), of the planet embedded within the star’s dusty disc. I think Stuart’s suggestion for its name is spot on.

The view of Formalhalt (masked by a coronagraph) showing the new planet embedded within a dusty disc (inset). See the annotated full-resolution image here.
Credit: NASA, ESA and P. Kalas (University of California, Berkeley, USA)

These discoveries clearly mark an important waypoint in our efforts to image an Earth like planet around a distant star, but they are also absolutely amazing in their own right. There’s far more in-depth commentary out there in the blogosphere, so I’ll point you in the direction of Sarah Askew, Phil Plait, Dave Mosher (who has a great IM interview with an exoplanet expert) and of course there’s an episode of the Hubblecast that you can watch below!

Hubble videos

For any of you reading the blog who came to my Hubble talk last night, hello! As promised here are a few select links to some of the videos from the presentation. First up is a zoom into the Hubble Ultra Deep Field.

Next is a pair of videos showing the creation of the stunning Cat’s Eye nebula – first the companion star dies creating the concentric shells of material, then the jets and magnetic field of the other (alive) star warp and twist into the nebula to create the central detail and swirls. The first part is here and the second you’ll find by clicking here.

Lastly then is a video of the bizarre object called V838 Monocerotis. You can download the video by clicking here. And remember that you can see more videos and (almost) all of the images from my talk on the ESA Hubble website here –

Final Hubble talk for 2008

On Monday (13th October) I will be giving my final Hubble talk of the year to the West of London Astronomical Society (WOLAS). It will be, once again, entitled “Not just pretty pictures – the science behind Hubble’s greatest images”. The society has written a nice synopsis of the background of the talk, on their meetings page here.

What are these (different) things coming out of this cloud? Come to my lecture to find out! Credit: NASA and Jeff Hester (Arizona State University)

I’ve really enjoyed giving this particular talk this year however I’m going to be busy working on something else for the next few months, so this will be my last one for a bit. For now though if you are interested in coming along to the WOLAS meet-up here’s a map to Christ Church, Redford Way, Uxbridge where the meeting is being held.

Super sharp Hubble shows stars in nearby galaxies

The Hubble Space Telescope is renowned for its incredible resolution used in studying the depths of the Universe – from the earliest galaxies to some of the grandest spirals. Recently though it has been using these superb capabilities to observe nearby galaxies – that is, a selection of galaxies between about 7 and 13 million light years from the Earth.

Above: Hubble’s resolution has revealed NGC 253 as a swirl of countless stars and dust lanes, enabling new insights into the character and structure of this beautiful galaxy.

At this time of year I love to get out a wide-field refracting telescope and use it to spot the relatively bright galaxies M31 (the Andromeda Galaxy) and M33. Through the eyepiece they appear as bright smudges of light, M31 being slightly elongated in shape. Those smudges are in fact the accumulated light of billions of stars shining away brightly, inside their respective galaxies. Yet we can’t see the individual stars in the galaxy with our amateur telescopes because their resolving power is simply too low, they appear blurred and merged together. But with Hubble things are much different.

When it looked at 69 nearby galaxies, its powerful optics were able to show individual stars and glittering star clusters within them. This ability to look at the fine detail has allowed astronomers to make important studies into the lives of these stars, how they are born and more. Astronomers can then also use the observations to make detailed conclusions about the shape and structure of the (often intricate) galaxy they are studying.

We can liken some of the previous observations to trying to understand how the population of a city lives, interacts and moves around, just by looking at a street-map. With Hubble’s brilliant resolution astronomers have been able to get a far more detailed view of the lives of galaxies and their stars – we can study the people in the street as it were. As Benjamin Williams, of the University of Washington says in the ESA press release “With these images, we can see what makes each galaxy unique”.

Left: A maelstrom of thousands upon thousands of individual stars reveals itself in this Hubble Advanced Camera for Surveys image of NGC 300, some 7 million light years away from Earth.

These observations are important because it is essential for astronomers to build an understanding of galaxies close to the Milky Way, in order to investigate (and hopefully understand) those which might be subtly different in the farther, or even extremely distant Universe. How are stars forming and how fast? Where are the old stars and why are some galaxies so massive? These are all questions which studies like these look to answer. Thankfully the survey which Hubble was working on (the ANGST or ACS Nearby Galaxy Survey Treasury) is wide ranging and shows a diverse sample of galaxies. It aims to create a practically complete study of all the galaxies in what is known as the Local Neighbourhood. So slowly but surely we are getting to know our cosmic neighbours!

Meanwhile, with the Hubble Servicing Mission 4 postponed until further notice (due to an anomaly with Hubble’s control unit) we are going to have to sit back and wait patiently to see if, and when, Hubble can get back to doing its usual spectacular science.

Image credits – Top; NASA, ESA, J. Dalcanton and B. Williams (University of Washington), T.A. Rector/University of Alaska Anchorage, T. Abbott and NOAO/AURA/NSF: Left hand side; NASA, ESA, J. Dalcanton and B. Williams (University of Washington)

Hubble’s history of the telescope

One of the legacies of next year’s International Year of Astronomy will be the education of people from around the world about the history of the telescope and astronomy. As part of this, the team at ESA Hubble has just released a great new vodcast/mini-documentary about the history of the telescope’s invention, in preparation for next year. This first episode introduces the great players in the telescope’s design and invention – including Galilei, Lipperhay and the pioneers of early observational astronomy like Huygens, Herschel (whose house is just down the road from where I am writing this!) and the Earl of Rosse.

This vodcast is actually part of a series that the ESA Hubble team are making so look out for the next few episodes. It’s a perfect introduction to the history of the telescope if you’re learning astronomy, or if you’re simply interested in the halcyon days of leviathan telescopes and the great discoveries of those brilliant early astronomers. Check it out below, or download different formats of the video here.

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)