I love libraries. I’m a member of four, not including University ones. Without libraries and the ability to borrow whatever I fancy, I think I’d be broke and living in a book-cave! So, I was sad this morning to hear that the number of adults visiting libraries in the UK has been decreasing steadily over the past couple of years.
“Ok”, I almost hear Niall saying, “that’s all very well Emma but this is an astronomy blog, do you have a point?” Well I can’t do anything about the drop in library visitors (except go more frequently myself and urge you all to do the same), but I can blog a little about one essential type of library used by astronomers.
The Herschel Space Observatory, launched last year, carries several spectrometers which are used to analyze the far-infrared light and look for the signatures of different chemicals that might be present. Obviously this only works if you can identify what it is that you’ve detected, and this is where the American Museum of Natural History comes in. They’ve got a large number of different minerals in their collection which they’ve been using to create a high-quality library of infrared spectra to which the Herschel data can be compared. This library might not feed anyone’s book habit, but it could potentially be vital in understanding the composition of various parts of the Universe.
Nissinboim, A., Ebel, D. S., Harlow, G. E., Boesenberg, J. S., Sherman, K. M., Lewis, E. R., Brusentsova, T. N., Peale, R. E., Lisse, C. M., & Hibbitts, C. A. (2010). The American Museum of Natural History Mineral Library for Spectroscopic Standards Lunar and Planetary Institute Science Conference
The first set of results from the Herschel Space Telescope have been flooding out over the past couple of weeks*, so it’s about time they got a mention here. Rather than rehashing one of the many press releases, I thought I’d focus on an interesting result that I doubt will get much attention – the detection of water vapour (and carbon monoxide) on Mars with the spectrometer within the SPIRE instrument.
I have to be upfront about this; the reason why you probably won’t hear much about this is that detecting water on Mars, whilst important for understanding its water cycle, is nothing new, though it is only present in small amounts (900 parts per million according to these observations). It was first seen in the Martian atmosphere in 1963, and since then has been extensively studied with many different observatories. The Opportunity rover even sent back images of cirrus clouds that are very similar to those we see here on Earth:
So what is special about these Herschel observations? Well, the telescope was never expected to be able to make them, because Mars is around 100 times brighter than SPIRE was designed to cope with. (Imagine taking a picture with your digital camera in the direction of the Sun on a really sunny day – the image you get looks overexposed because the excess light has overloaded (saturated) it.) However, the instrument team, led by Bruce Swinyard, didn’t let that stop them – they found a way to ‘desensitize’ the detectors in the instrument and avoid this saturation problem, enabling the water vapour to be seen.
This might not be as flashy as some of the other early results from Herschel but it does illustrate how well its been performing over this first year. This new ‘bright source’ mode will open up new targets to observe that were previously thought impossible and personally I think that’s something worth mentioning!
* For more Herschel results have a look at this audio slideshow from the BBC. There’s also this movie from the European Space Agency celebrating Herschel’s first year in space:
Image credits: NASA
B. M. Swinyard, P. Hartogh, S. Sidher, T. Fulton, E. Lellouch, C. Jarchow, M. J. Griffin, R. Moreno, H. Sagawa, G. Portyankina, M. Blecka, M. Banaszkiewicz, D. Bockelee-Morvan, J. Crovisier, T. Encrenaz, M. Kueppers, L. Lara, D. Lis, A. Medvedev, M. Renge, S. Szutowicz, B. Vandenbussche, F. Bensch, E. Bergin, F. Billebaud, N. Biver, G. Blake, J. Blommaert, M. de Val-Borro, J. Cernicharo, T. Cavalie, R. Courtin, G. Davis, L. Decin, P. Encrenaz, T. de Graauw, E. Jehin, M. Kidger, S. Leeks, G. Orton, D. Naylor, R. Schieder, D. Stam, N. Thomas, E. Verdugo, C. Waelkens, & H. Walker (2010). The Herschel-SPIRE submillimetre spectrum of Mars to appear in the Herschel Special Issue of Astronomy & Astrophysics arXiv: 1005.4579v1
Firstly, mustn’t forget to mention that the Carnival of Space has gone festive this week over at Cumbrian Sky.
Now, in the spirit of the season, I thought I’d bring you a Christmas star. Well, a Christmas star-forming region in the constellation of Aquila in fact – it’s one of the ‘wow’ pictures presented last week at the Herschel First Results Meeting in Spain (a place for all the astronomers working on the different Herschel projects to get together to show off their data!)
It’s a composite image, made up of data from both the PACS and SPIRE instruments. The fluffy-looking orange and red filaments are cool dust clouds, whilst the bluer areas show where the gas and dust has come together under gravity to make new stars.
Hang on, though. That’s a lovely picture, and the red and gold look very festive, but surely there’s some way of making it, well, more Christmassy…
Ahhh, that’s better
Just one more thing, don’t forget to track Father Christmas tonight over at NORAD (as I write this, he’s passing over Russia apparently)!
Hope you all have fun tomorrow whatever you’re doing and see you in the New Year.
Back in June and July Stuart and I talked about the very first images from PACS and SPIRE, two of the three instruments onboard the Herschel Space Telescope (for those of you who were wondering, the third instrument, HIFI, is currently switched off due to a malfunction but it should be back working properly soon). Well, the PACS and SPIRE cameras can also be operated in the versatile ‘Parallel Mode’ in which they observe the same patch of sky simultaneously. This is a very efficient way to take images in all of Herschel’s five available infrared wavelengths (3 from SPIRE, and 2 from PACS), and will eventually be used to survey large areas of the sky quickly.
The stunning picture at the top of this post is the result of colouring and combining all five images from the first trial Parallel Mode run. It shows an area of the Milky Way (our own galaxy) about 16 times bigger than the area of the full Moon (that’s 2×2 square degrees). Herschel is designed to see the cold clouds of dust and gas that are invisible to other telescopes like Hubble. In this case the clouds are surrounding newly forming stars – the turmoil suggested by all the twisting filaments makes this an exciting place to be born!
Herschel is now approaching the end of its testing and calibration phase and will soon begin what’s known as ‘science demonstration’, in which it will test out a range of different observations to make sure it’s performing as expected. The first science data has already gone to a select few astronomers – I think things are going to get very busy, very soon!
A couple of weeks ago ESA released the first images from the PACS instrument onboard the Herschel Space Telescope. This morning it followed them up with the equally impressive first light images from the longer wavelength, UK led, SPIRE instrument.
The images above show two spiral galaxies, M66 and M74. The wavelengths at which SPIRE operates means that it sees the glow from cold clouds of dust which occur in regions where lots of star formation is occurring (this is why the spiral arms show up so clearly). Even more interesting for me though are all the blobs that can be seen in the background to the images – each one is actually a much more distant galaxy, too far away from us to be seen as anything other than a point source. As the speed of light is always the same, looking at these galaxies is like looking back in time; the light Herschel has detected was emitted many, many years ago and has been travelling towards us ever since. This means that studying these objects can tell us about what things were like in the Universe when it was young.
This picture compares two images of the same nearby spiral galaxy, M74, one taken with the Spitzer Space Telescope and the other taken with the SPIRE instrument. It illustrates how much more detail Hershchel can see with its larger (3.5 m) mirror and more sensitive detectors.
More images from these first observations can be found here and see here for the UK Herschel Outreach Site which gives a good overview of the mission, including a fun counter showing how far away the satellite currently is along with how fast its now moving.
The quality of these images is amazing given that they were taken before the telescope’s been properly set up. I think it’s like buying a new TV, turning it on for the first time, and being able to start watching it after only half tuning it in. It’s all very exciting!
The first images from one of Herschel’s cameras are out! While not from the spire instrument which was worked on at Edinburgh this is still pretty exciting!
The Herschel Space Observatory, launched last month, achieved an important milestone this morning when the command to fire the bolts holding down the cryocover appears to have been executed successfully. The cover has been protecting the three science instruments from being contaminated during (and shortly after) launch. If this had failed the telescope would be blind (known in the trade as a ‘single point failure’), making it a tense moment for everyone involved in the project! There’s still a lot of work to be done in commissioning and testing though until the telescope can start its routine operations, but this is a very important step on the way.
There’s a neat video on youtube which shows what would have happened in slow motion.
So the European Space Agency’s Herschel and Planck telescopes are currently on their way and science teams are running around preparing for the start of observations. You may have seen various reports referring to their final destination, L2. I thought it would be a good time to write a quick bit about where this is and why it’s important.
L2 is the second Lagrange point. Lagrange is not only a reasonable rhyme for orange but is also the name of the designer of a system of mechanics that formed the basis for the only uni course I failed (the story involves a headache and a monkey). When studying gravity, finding the orbit of one body around another is fairly easy. Add a third body and the problem becomes pretty difficult. Lagrange used his new way of formulating mechanics to find a number of solutions to this three body problem. Imagine the Earth orbiting round the Sun. If you take the gravity of both into account along with the orbit of the Earth you get five special points where an object can sit without being pulled out of place (see the picture). L1, 2 and 3 lie on a line that connects the Earth and the Sun and L4 and L5 lie in the Earth’s orbit 60 degrees in-front and behind the Earth respectively. All five points stay in the same place relative to the Earth and Sun and Lagrangian points exist in all two body systems, the Sun-Earth system, the Sun-Jupiter system, planet-moon systems and even in planetary systems around other stars. In the case of the L2 point (and L1 and L3), a spacecraft can orbit around here with occasional small corrections from propulsion systems. For a space telescope this a pretty good place to be, you can orbit around L2 without using too much fuel and annoying things that get in the way like the Sun or the Earth are always in the same direction so you just need to point your telescope away from both (several telescopes that look at the Sun sit at L1 so the Earth doesn’t get in their way).
However in the L4 and L5 points are even more interesting. Not only are these points where objects can sit but nearby things are drawn towards them. Hence stuff tends to collect in these points. Saturn’s fourth largest moon Dione has two smaller moons Helene and Polydeuces sitting in in it’s L4 and L5 points respectively. Tethys, another of Saturn’s moons, also has two smaller moons in its Langrange points. In the Sun-Jupiter system there are loads of objects collected around the L4 and L5 points. These are asteroids that just seem to have wandered in there and got stuck. Those that lie at the L4 point are named after Greek characters from the Trojan war and those that lie around the L5 point are named after Trojan characters. In total there are maybe a million of these Trojans (a slightly confusing name for both the Trojan and Greek ones) over 1km in size, although I don’t think there are a million names in the Illiad so I doubt they are all named after Trojan war characters. Interestingly I read this paper a while back which came up with a way of detecting Trojans in planetary systems around other stars.