Posts Tagged ‘Planck’

Planck sees the Crab

September 29, 2009

[cross-posted from Planck UK site]

Last week, the Planck satellite observed the Crab Nebula, also known as M1 from Messier’s catalogue, and Tau A to radio astronomers. The Crab Nebula is one of the brightest objects in the sky at radio and sub-mm wavelengths, and is used by many astronomers to calibrate their instruments. It is the remnants of a star which underwent a violent and catastrophic explosion at the end of its life, an event known as a supernova. The Crab Nebula is associated with one of the few supernovae which was observed, as it was seen by Chinese and Arab astronomers in 1054.

Hubble image of the Crab Nabula
Hubble Space Telescope image of the Crab Nebula, showing the colourful nebula and filaments. Image credit: NASA/ESA

After the supernova, the outer layers of the star were scattered widely into a huge cloud of gas, which we now see as a nebula, and is frequently observed by amateur and professional astronomers. The core of the star ended up as a pulsar, a rapidly rotating, magnetised neutron star. However, it is the surrounding nebula that Planck is interested in. The nebula is around 13 lightyears across, which is around 10,000 times larger than our solar system (depending on where you define the edge). It is also relatively close in astonomical terms, at about 6 lightyears distance, and so is also relatively large in terms of astronomical objects see from Earth. It is around 7 arcminutes across, which is 7/60th of a degree, or about 1/4 the diameter of the full moon as seen from Earth. The smallest of Planck’s beams on the sky is 5 arcminutes and the largest 30 arcminutes, so to the majority of Planck’s detectors the Crab Nebula will have appeared as a “point source” – a single blip in the data. However, it is so bright that it would still be very obvious.

SCUBA measurements of the Crab nebula
SCUBA image of the Crab Nebula at 350GHz. The colour shows the brightness (blue/black=dark, red/white=bright), and the length og the black lines shows the relative amount of polarisation. Image credit: J.S. Greaves, W.S. Holland & T. Jenness (Joint Astronomy Centre)

Because the central pulsar is magnetised, the Crab Nebula is permeated by a magnetic field. This causes any electrons in the nebula, of which there are many, to spiral around the magnetic field lines and emit radiation known as synchrotron radiation. This radiation, which is brightest at radio wavelengths, but still very strong at Planck frequencies, is polarised, which makes the Crab an ideal object for calibrating the polarisation-sensitive detectors on Planck. Many experiments have observed its polarised radiation, including the SCUBA instrument on the JCMT on Hawaii, which observed it at 350GHz (a wavelength of 850 microns). One of the properties of synchrotron radiation is that it varies in a fairly predictable way with frequency, so it is possible to tell from an observation at one frequency what it will look like at another.

The data will take time to analyse, but will be ingested into the Planck database and used to help calibrate its instruments. The Crab Nebula is not the only calibration source, but is the best single source in the sky for calibrating the polarisation angles.  Other non-polarised sources include the planets in our own solar system, particularly Jupiter, which are very bright at Planck’s frequencies as well as to the naked eye.

Planck at the Royal Society

June 13, 2009

[cross-posted from Planck UK site]

The Planck mission will be represented at this year’s Royal Society Summer Science Exhibition. This prestigious event, hosted every year at the Royal Society, in London, allows around 20 different groups of scientists to present their work, covering all fields of science. This year, scientists from around the UK working on Planck and Herschel will be presenting an exhibit entitled “From the oldest light to the youngest stars: the Herschel and Planck missions“.

The exhibition is completely free to members of the public, and is open from Tuesday 30th June until Saturday 4th July. We will have scale models of Planck and Herschel, and will allow visitors to explore both the Universe and the world around them at different wavelengths. A key attraction should be an infrared camera, which will allow people to have their infrared portrait taken. There will also be an interesting way of viewing the sky at a number of wavelengths, and of course freebies to take away. The stars of the show, though, should be the scientists themselves. We will be there to explain what we are doing with these exciting missions, and to answer all the questions you might want to ask.

So if you’re in London on a couple of weeks, pop in to the Royal Society and see the exhibition. With 21 exhibits covering a huge range of groundbreaking research areas there should be something for everyone – and there’ll almost certainly be something that grabs your attention that you had no idea existed.

Tracking Planck and Herschel

May 21, 2009

As well as the official ESA ground stations which are tracking Planck and Herschel, a group of (mainly) Spanish astronomers have been observing them with optical telescopes.  They’ve also identified a few other pieces of the Ariane 5 upper stage travelling along with them, as well as the Sylda adapter which separated them within the rocket fairing.

Optical observations of Planck, Herschel and the Sylda adapter

Optical observations of Planck, Herschel and the Sylda adapter

On their “Images” page, you can see some light curves – which show how the brightness of the objects varies with time – for Herschel, Planck, Sylda, and a few other fragments.  The vertical axis, labelled “R”, is the brightness in astronomical units of “magnitudes“.  For comparison, the faintest stars visible with the naked eye are around magnitude 6, and a higher number means fainter – I’m sure this made sense to Ptolemy and Hipparchus.  In fact, the scale is logarithmic, so a magnitude of 17 is about 10,000 Ifainter than magnitude 6, putting them at around the same brightness as a small asteroid or a larger Kuiper Belt Object.

Light curves of Herschel, Planck and a few other fragments

It’s interesting to see that Herschel brightens by about 2.5 magnitudes (about a factor of 10) at one point.  There is one very plausible explanation for this: the timing coincides pretty much with the orbital manoeuvre which Herschel executed on 18th May, which must have oriented the solar panels to a more favourable angle for reflecting sunlight back to Earth.  Planck and the other fragments show smooth gradual declines in brightness over time as they get further from Earth.

So here’s where I make a prediction, just as any scientist should.  I predict that Sylda and the fragments will eventually fall back to Earth and burn up, so they might brighten a little.  They’re almost certainly in elliptical orbits so may vary slightly as their distance from Earth changes, and also if they’re spinning or tumbling at all. [I've been corrected by Bill Gray (see comment), who informs us that Sylda and the fragments will end up in heliocentric orbits - i.e. orbiting the Sun]. Planck’s brightness should stabilise when it reaches its final orbit around L2, as its angle realtive to the Earth and Sun should stay pretty much constant.  I predict that Herschel, however, will show slight variations in brightness as it slews to point at various objects around the sky – though it has to keep its solar panels pointed somewhere towards the Sun.  Whether the variations will be large enough to observe with telescopes on Earth remains to be seen.

If you want to see how far Planck and Herschel are from Earth, then you can use the JPL Horizons catalogue.  It’s somewhat self explanatory, but the output can look a little technical.  Change the “Target Body” and search for “Herschel” or “Planck”.  You also have to make sure that the time span covers the range you want.  For teh table output, I recommend selecting “Obsrv range and rng rate” and “One-Way Light-Time” – though there are many to choose from (though not all applicable).  You can set some of the units in the “optional” section.  When you hit “Generate ephemeris” you’ll get a table showing the numbers you’ve requested, and even a table explaining what they all mean.  There are a few options if you want to export the results to a file your favourite spreadsheet programme can read, so you can make your own plots.  You can play with a few other things too, such as setting the observer location to L2 (by putting “@392″ in the “Lookup Named Location” box).  It’s not certain that the orbital parameters used are exactly what Planck and Herschel will actually use, but they’re probably not too far off.

On their “Images” page, you can see some light curves – which show how the brightness of the objects varies with time – for Herschel, Planck, Sylda, and a few other fragments.  The vertical axis, labelled “R”, is the brightness in astronomical units of “magnitudes“.  For comparison, the faintest stars visible with the naked eye are around magnitude 6, and a higher number means fainter – I’m sure this made sense to Ptolemy and Hipparchus.  In fact, the scale is logarithmic, so a magnitude of 17 is about 10,000 Ifainter than magnitude 6, putting them at around the same brightness as a small asteroid or a larger Kuiper Belt Object.

Planck and Herschel as seen from the ground

May 20, 2009

As they started on their way to L2, the Planck and Herschel satellites were observed from Earth.  The ESA “Optical Ground Station” on Tenerife, which is one of the stations that tracks ESA satellites and monitors their progress, observed them a few hours after launch and made this animation.  At this time – around 21:30 GMT on 14 May 2009, just over 8 hours after launch – they were 100,000 km from Earth.  That’s already a quarter of the distance to the Moon, but only around 1/15th of their final distance from Earth – L2 is 1,500,000 km from Earth.  They were also seen by the Faulkes Telescope in Australia.  In both images, there are 3 moving dots.  The two brighter ones are Herschel and Planck while the fainter one, which is quite close to Planck, is the SYLDA 5 fairing which separated the two spacecraft in the rocket.

Soon the spacecraft will be much, much further away, and much more difficult (if not impossible) to see – at a few metres across they’re right on the lower limit of the smallest near-Earth objects observed.  Their brightness will primarily be due to the reflectivity of the solar panels.  Since these are pointed towards the Sun, and therefore almost at Earth, it might work out now and again as Herschel and Planck move in their orbits.  I haven’t crunched the numbers to work out if this is possible (exercise for the reader?), but it should certainly be a challenge.

Launch!

May 14, 2009

Cross-posted on Andrew Jaffe’s Blog and the Planck Mission Blog.

Planck and Herschel are en route to their orbit at L2!

We were about 7.5 km from the launch, at the “Agami” viewing site. Here is my golden ticket:
Planck launch badge

We all milled around for half an hour, snapping pictures of friends, eminent scientists, and at least one Nobel prize winner, but it all went silent when they announced the last few minutes before launch. The inevitable 10.9.8.7.6.5.4.3.2.1 and ignition was followed by a still, silent seven or so seconds, and then we saw the smoke and flames.
Herschel/Planck Liftoff
(Apologies for the poor quality; there were many people there with far more powerful zoom lenses than my meagre 2.5x.)

The rocket then pierced the clouds:
Herschel/Planck in the sky
Soon after, the booster rockets separated (which those 200x telephoto lenses could capture), and soon all left to see with the naked eye was the rocket’s trail:
Herschel/Planck contrail

For the rest, we had to watch the video feed from the control room, and, about half an hour later we finally heard what we were waiting for: first Herschel, and then Planck, had separated from the rocket and were on their own, off to L2. Four or five hours later, Planck’s instruments had been turned on, and the ESA team in Darmstadt was monitoring their progress. There’s a lot going on now, but we won’t have anything like scientific data for two or three months — and then our work is cut out for us.

Huge thanks to the instrument teams for their hard work for more than the last decade. Soon, the hard part for us scientists and data-analysts begins: four or so years of data coming down from the satellite, being cleaned and calibrated, building and rebuilding our (computer) model of the instrument, letting us build and rebuild our models of the Universe.

Thanks also to the HFI Instrument Principle Investigator and co-PI, Jean-Loup Puget and Francois Bouchet (and especially Hélène Blavot) for arranging this extraordinary opportunity for us scientists to see this part of the fruits of our work.

Launch Blog — Day 2: Rollout

May 14, 2009

Cross-posted on Andrew Jaffe’s Blog and the Planck Mission Blog.

Today we saw the rollout of the gargantuan Planck/Herschel Ariane 5 rocket, when they move it from its assembly building to the launchpad. Spectacular!
Planck Rollout
There are plenty more pictures, and some movies, which I’ll try to edit and post shortly. At the end of the day, I was interviewed and inadvertently kidnapped by Chris Lintott and the BBC Sky at Night team. But I am here to tell the tale (and better fed for it) and ready for the — very — big day tomorrow.

Live coverage of the launch, scheduled for 2:13pm on 14 May, at:

Launch blog — day 1

May 13, 2009

Cross-posted from Andrew Jaffe’s Blog and the Planck Mission Blog

Today was spent in Cayenne — the capital of French Guiana, where most of the hotels are located, and Kourou — home of ESA’a Centre Spatial Guianaise. We climbed up a nearby peak for a look over the Spaceport, but mostly we saw hand-sized spiders and a hazy view of what some very large if indistinct structures.

Closer up, we (about a hundred scientists, obviously more than the ESA staff were used to) got a tour of the facilities, starting in the “Jupiter II” control room where the launch will actually be, um, controlled:
Arianespace control room

We also saw the launch sites for the Vega and Soyuz rockets, and of course for our own Ariane 5:
Ariane launch pad
But better will be tomorrow, when we get to see the rocket — our rocket — rolled the few kilometers from its current building to the pad in preparation for Thursday’s (hoped-for) launch.

Pre-launch blitz

May 8, 2009

Cross-posted from Andrew Jaffe’s Blog:

With less than a week to go before its planned launch, The Planck Surveyor Satellite has been loaded into the fairing of its Ariane 5 rocket along with its sister satellite, Herschel. It is scheduled to be rolled out to the pad on May 13, and the launch window opens on May 14 at 13:12 GMT. Within three months, it will be at the Lagrange 2 (L2) point, from where it can watch the sky with the Sun, Earth and Moon all comfortably shielded from view.

Once there, Planck will scan the sky for at least 14 months. But don’t expect to see much out of the mouths (or blogs, or printers) of Planck scientists for a while: we’ve got a full year thereafter to analyze the data, followed by a year’s “proprietary period” during which we’ll do our best to extract the most exciting science. But until then — the first rule of Planck is: you do not talk about Planck. The second rule of Planck is: you DO NOT talk about Planck. (Luckily, Herschel expects to release its pictures of the infrared and submillimetre universe much more quickly.)

For now, the European Space Agency, the UK’s Science and Technology Facilities Council, and of course us Planck scientists ourselves have been gearing up both for the scientific data — and the press.

ESA has a Herschel and Planck launch campaign page with a nifty live countdown (which users of Apple’s Safari browser can make a dashboard widget out of). Last week, STFC held a pre-launch press event in London, which got us some coverage in The Independent, The Daily Mail, The Telegraph, The Times, as well as BBC Radio and TV news. (And Sky at Night will have coverage from the launch.)
We’ve also been covered in New Scientist (complete with always-exciting quotes from me).

If this media saturation isn’t enough, you can check out the page dedicated to Planck in the UK, Follow Planck on Twitter (and Herschel too), read the Planck Mission Blog (there’s one for Herschel, too).

As for me, I’m taking a break from this term’s teaching — off to French Guiana next week for the launch (barring further delays). For those of you less lucky, it will be visible on satellite tv and streamed by ESA. I’ll do my best to keep up the twittering and blogging, probably cross-posting from here to the Planck Mission Blog. Wish us luck!

According to New Scientist…

May 5, 2009

Planck (and Herschel) are ‘space science as it used to be: big and bold – and risky. Not for decades has there been so much riding on a rocket launch, literally and metaphorically.’

This makes me feel rather proud for us to be working in such a grand tradition. It’s also scary to hear that ‘if we lose Herschel and Planck, the heart of ESA’s – and arguably the world’s – space science programme would be ripped out..’

Read the rest of the article here.

(And thanks to the person who tipped me off to this article!).

Planck is in the Launch Vehicle!

April 30, 2009

New pictures from ESA show Planck installed in the Arianne 5 rocket that will send it into space.

Planck being lifted onto the rocket

Planck being lifted onto the rocket

Planck in the launch vehicle

Planck in the launch vehicle

This will be almost the last time we see Planck before it launches!


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