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Another one bites the dust...
This post over at Skymania tells the very sad news that the London planetarium will soon be no more. This is a very bad thing. Does anyone else feel like we're running out of serious science exhibits? When the planetarium at Jodrell Bank was demolished in 2003, a lot of the staff were very upset about it. The visitor centre is now much smaller than it once was, but the staff are trying to make the most of what they have until the powers that be get around to building the long-promised new one. It was bad enough to lose ours through politics, but to lose the London one in favour of a show about celebrities?!? What is the world coming to? I'm feeling rather disillusioned right now, this isn't helping.
Posted by Megan on Monday 30th Jan 2006 (23:26 UTC
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Jodrell's new space race
What with telescope time coming up, schedules to prepare, funding applications due in soon (not that I stand much chance of succeeding mind you) and a school visit coming up on Tuesday, things are a bit busy just now! Teaching starts this week as well, so I'll be spending one day a week travelling to Manchester and back for the next three months or so. Still, I'm making time to keep visitors entertained with Ask an Astronomer sessions again this weekend and this afternoon, as the Sun was setting, my rocket flew from the Mk 2 field.
This little rocket is a good few years old now, and has flown successfully on many occasions. Today's launch was a good one. The weather was perfect: clear blue skies with only the tiniest bit of wind. Once all the minor hiccups had been resolved (like having the right key for the explosives box, wedging in the ignitor with a stick and putting new batteries in the launch controller) the rocket blasted off from the pad watched by Bill, the security guard, and Mark and Ian, two of the telescope controllers. A perfect launch was followed by a not-so-perfect descent as the old elastic shock cord gave up and snapped, leaving the body and parachute seperate. While the body came down with a muddy splat in the next field, the nose cone and 'chute drifted off into the sunset, unlikely to be seen again.
Still, it was fun. The body was recovered suprisingly easily, after climbing through a hedge and squelching round the field for a bit, but there was no sign of the rest of it. It will fly again, though, as a new nose cone can be easily made from some good card, a new 'chute can be made from a plastic bag, and the shock cord is just a piece of light elastic. May be I'll build a new pad too, then we can drag race rockets at the summer barbecue...
Posted by Megan on Saturday 28th Jan 2006 (23:43 UTC
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Smallest planet yet found
Using a technique known as gravitational microlensing, an international team of astronomers have detected the smallest known extra-solar planet. The discovery, made by the PLANET collaboration who use a network of telescopes in the Southern hemisphere to monitor stars in the Galactic bulge for microlensing events, was published today in Nature magazine.
Gravitational lensing is where one massive object bends the light from a more distant object along roughly the same line of sight (actually it is space which is bent, light just follows the distortion). The more massive the intervening object, the stronger the effect. Lensing is also strongest for objects which line up perfectly, producing a ring of emission known as in Einstein ring. Often, this effect is studied on huge scales where a galaxy lenses the light of a more distant quasar. In this case, however, the astronomers were looking for events much closer to home, they were watching for lensing by stars in the centre of our own Galaxy.
There are many ways to find planets around other stars: dimming caused by transits and Doppler shifts caused by radial motions as the planet pulls the star slightly in it's orbit are two of the most common, but both of these methods are sensitive only to massive planets which either block large amounts of the star's light, or pull the star by a significant amount. Microlensing, on the other hand, is capable of detecting Earth-mass planets by perturbations in the light curve of a lensing event.
An ordinary microlensing event (see a groovy demo of this by the MOA team) produces a sharp spike in brightness of the background star being lensed. A planet around the lensing star will cause an additional perturbation in the brightness measurements, which may look something like this:
Microlensing event OGLE 2005-BLG-71, evidence for an extra-solar planetCREDIT:
A. Udalski and the PLANET collaboration (astro-ph/0505451
In 2004, astronomers using this technique discovered a planet
orbiting a star at a distance of 17,000 light years, the most distant extra-solar planet discovered at the time. The discovery reported today is a planet around a cool, red star at a distance of almost 25,000 light years, with a mass of merely five times the Earth. That's pretty small! This is, in fact, the smallest extra-solar planet ever detected, and it is especially impressive given the distance. It's rather catchy name is OGLE-2005-BGL-390Lb, surely someone can come up with a nickname for it?! The discovery could not have been made by any of the other techniques, they are just not sensitive enough. Why look towards the Galactic bulge? There are huge numbers of stars there so it is the area with the highest probability for a microlensing event to occur, so with a bunch of small telescopes monitoring the area pretty much constantly (PLANET uses 1-m telescopes spread around the Southern hemisphere so that it is always night somewhere
), they are likely to pick up any events.
This really is very, very cool. If you have access to Nature
, go read the article. You never know, they may find something even smaller yet....
Posted by Megan on Wednesday 25th Jan 2006 (17:27 UTC
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Just goes to show...
...you should never write off an evening. Half an hour after writing my last post, I went back on the roof to check I hadn't left anything up there and discovered that the fog was thinning out. So, the telescope came back up the corridor and out onto the terrace outside the control room. With (almost) all the lights switched off, the sky really did look very good. Orion was dipping towards the horizon by this time, Saturn was high in the South and the Milky Way stretched over the Lovell telescope. After an hour or so touring the sky it was getting quite cold so Mark, that night's controller, and I went in for a mug of tea. The weather came and went a bit after that, the fog came back for long periods and was still patchy when I left at gone 5am.
After all that I still woke up at 11am this morning. I headed over to the Observatory to find the visitor centre was as busy as Saturday, so at half two I was outside doing Ask an Astronomer again! It was very cold so I was glad to get back indoors an hour later for a warm drink.
I think I'm going to have an early night tonight...
Posted by Megan on Sunday 22nd Jan 2006 (20:46 UTC
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This morning (after watching From the Earth to the Moon last night until silly o'clock) I did an "Ask an Astronomer" session in the office when Mike, our site manager, brought his diving club round the Observatory. They asked quite a few questions and seemed quite interested which is always good. When they went off to take a look in the control room, I finished installing the last part of a 1/250th scale model of a NASA Deep Space Network tracking antenna, the plans for which can be found at JPL, which I started building while waiting for New Horizons to launch the other day.
After they left I wandered over to the visitor centre and found that they were very busy which is great to see as winter is usually a very quiet season. (There is a book of old press cuttings in the library here which show that when the site was first opened to the public on open days in 1965 there was so much interest that 5,500 people were turning up on some days and there were huge traffic jams blocking the local roads for miles!) I figured it was a perfect opportunity for some guerilla astronomy, so I offered to do an Ask an Astronomer session for them as well. Normally these sessions only run during the school holidays when it is busy, but there were enough visitors to make it worthwhile today. The 3D theatre was full and the audience were very talkative (they even laughed at my jokes, very unusual!), one of them came to talk to me afterwards and had loads more questions. As much as I hate public speaking, it is great when people really take an interest.
The weather had been nice all day so I left fairly early to have dinner, the plan being to come back and get out the telescope when the atmosphere had settled down a bit. As I cycled back down the road to the Observatory earlier I had to try hard to concentrate on the road as the Milky Way was quite prominant overhead. I got out the telescope and assembled it on the roof while Andy, this evening's controller, kindly turned off the floodlights. I left the 'scope outside to cool while I went to put on some extra layers and get a cup of tea. By the time I got back outside the stars were fading rapidly and within ten minutes it was foggy enough that the top of the telescope was starting to disappear. Grrrr. Hopefully everyone out there in blog-land is having better weather...
Posted by Megan on Saturday 21st Jan 2006 (23:49 UTC
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New Horizons, take-2
After yesterdays power failure at the Applied Physics Laboratory (APL), the organisation in charge of the New Horizons probe, the launch was scrubbed once again. Today's launch window opens at 18:08 UTC and so far everything looks good. The countdown clock is running, the virtual launch centre is operational, and the wind is within limits.
In about half an hour, the fuel will start to be loaded into the rocket so the pad is being cleared and checks of the cryogenic systems and tanks are being carried out.
T-2 hours and holding.
Posted by Megan on Thursday 19th Jan 2006 (15:42 UTC
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New Horizons is go!
With any luck, the New Horizons - NASA's mission to Pluto and its satellites - will be taking off on board an Atlas V rocket in less than half an hour. NASA have a continuously updating webpage showing the current status if (like me) you can't watch the launch. Everything looks good so far, the fuel has all been loaded and there appear to be no problems. Fingers crossed!
Posted by Megan on Tuesday 17th Jan 2006 (18:10 UTC
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How to confound an astronomer
Generally, or so the folklore goes, if you want to annoy an astronomer who is busy talking excitedly about some new observation (or theory), just say something along the lines of "fascinating, but what about magnetic fields?" The truth is, a lot of the time we just don't know as much as we'd like to about what magnetic fields are doing and just how they are influencing what we see. That's why we keep looking and keep modelling, one day we'll get there. Anyway, a group of astronomers at Berkeley have been looking for magnetic fields in giant molecular clouds and have found what they describe as a magnetic slinky in Orion.
The Orion molecular cloud (OMC) is absolutely stunning when you see it in photographs as it is absolutely huge (it is also quite faint so you can't see it with your eyes, which is a real shame). Centred on a region of star formation within our own Galaxy, the complex contains loops, spurs and clouds, all glowing faintly red due to emission from warm hydrogen gas.
A magnetic "slinky" in Orion CREDIT:
Saxton, Dame, Hartmann, Thaddeus; NRAO/AUI/NSF
It is thought that magnetic fields can shape gas clouds (and jets), but it is very difficult to detect these fields as they are often very weak. This is one example of where radio telescopes are particularly useful as they can detect the signals that characterise magnetic fields. What the researchers found when looking at the OMC using the Green Bank Telescope (GBT
) at a frequency of 1420 MHz, the radio frequency at which neutral hydrogen emits, was that the field was orientated towards us on one side of a filament and away from us on the other. This is a dead givaway for a helical field, something like a corkscrew shape, hence the slinky analogy. Now, there are other possible explanations for the observed field orientations (as the authors themselves point out in the press release
) but this seems the most likely one. Wow, slinkys in space, whatever next?!
Posted by Megan on Friday 13th Jan 2006 (22:33 UTC
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This is the latest press release from the Galaxy Evolution Explorer (Galex), and it is absolutely stunning. The Cartwheel galaxy is a partcularly impressive example of a starbust galaxy, one undergoing an enormous burst of intense star formation. In this case, the star formation was triggered by a direct collision with a smaller galaxy.
Multi-wavelength view of the Cartwheel galaxy CREDIT:
NASA/JPL-Caltech/P. N. Appleton
(Spitzer Science Center/ Caltech)
A long time ago, the smaller galaxy involved in this system passed straight through the middle of the larger galaxy, creating a huge shockwave propagating outwards through the interstellar medium of the larger galaxy, like ripples in your tea when you drop in a sugar cube (should you want to do such a thing!). The shock wave causes gas clouds to collapse as it passes which, in turn, causes stars to form. The bigger the collapsing gas cloud, the more massive the stars which form. These stars burn bright and quick, and violently explode as supernovae when they run out of fuel. These explosions leave behind remnants and cause their own shock waves which could trigger further star formation.
Each colour in this picture represents a section of the electromagnetic spectrum. The purple is X-ray emission seen by the Chandra satellite, green is visible light from Hubble, red comes from an infra-red observation made with Hubble, while the blue represents ultra-violet light as seen by Galex itself. This shows that the warm gas and dust (as seen in the infra-red) is concentrated in the centre of the galaxy while the largest concentration of young, hot stars are found in the outermost ring where the ultra-violet and X-ray emission is strongest. This galaxy is also bright when you look with radio telescopes. A group of researchers did just this with the VLA
last year and detected many of the supernova remnants, you can find their paper on astro-ph
Posted by Megan on Friday 13th Jan 2006 (11:44 UTC
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One of the best bits about research astronomy is getting to play with some pretty cool telescopes. It's not simple though. Telescope time is expensive and scarce, if you want to use a telescope you have to justify your plan to a panel of other researchers. This means writing a proposal outlining what you want to look at, why you want to look at it (how will it further our understanding?) and the specific set up you want to use (the technical justification). There are usually so many proposals that there is physically not enough time to do everything that astronomers around the world would like to do, so the job of the panel is to read all the proposals and decide which ones should actually be given time. This whole process, as you might imagine, is not a quick one. It can take months from the proposal deadline before you finally hear a result from the panel, also known as a time allocation committee (TAC). The last deadline for the Very Large Array (VLA) was in October 2005 and today the decisions of the TAC were sent back to the researchers who asked for time.
My group asked for two chunks of time for two different proposals. The first is to look at M82, a nearby galaxy which is undergoing a burst of star formation more intense than anything occuring within our own Galaxy. We want to look at a group of objects known as OH masers (kind of like lasers, but naturally occuring in space and in the radio part of the spectrum rather than the visible) in more detail than has been done before in order to look for structure. This will hopefully tell us something about the physics of these star forming regions. Absorption and emission by the OH molecule across this galaxy can be seen in this little movie.
The other proposal was a continuation of a program monitoring ten star-forming galaxies every few months for five years. What we are looking for are new supernovae, massive stars which have reached the ends of their lives in massive explosions. In active star-forming regions such as the cores of these galaxies there is often a lot of dust which can block out ordinary visible light. This can mean that searches for new supernovae using optical telescopes may miss some if they occur within or behind a dust cloud. Radio waves pass straight through this obscuring dust so we should be able to spot any supernovae occuring in these regions. This project has already been going for two years and we've observed several supernovae already.
Happily for us, although some of the panel weren't totally convinced by our justifications (you can rarely convince everyone), both of our proposals have been given time on this occasion. Now we have to write a couple of schedules telling the telescope where to point and what calibrators to look at so we can make sense of the data. It takes quite a long time from writing the proposal to getting the data, but if you discover something exciting then it is worth the wait...
Posted by Megan on Thursday 05th Jan 2006 (22:59 UTC
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A good start
Backwoods tea CREDIT:
Last night may have been a bit of a wash-out, but it was clearing by 1am and Mars was appearing from the clouds. The clear skies lasted as today has been beautiful. This morning I made the most of the sunshine and went for a ride, stopping to watch the geese slipping around on the ice that covered the western side of Redesmere
on the way back. A lot of other people had the same idea (although most of them drove there as the car park was busy) but I think the ice cream man might have been a little optimistic! The sunset was pretty impressive too, so I made the most of having a garden and a ready supply of dead (although rather damp) wood. Mmmm, tea.
All in all, after the last few weeks, it has been a nice peaceful start to the year.
All I need now are some stars to look at... the forecast is looking good for Tuesday night. Fingers crossed.
Posted by Megan on Sunday 01st Jan 2006 (22:06 UTC
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