In the news this month: pulsar irregularities
Crab nebula CREDIT:
X-ray: NASA/CXC/SAO/F.Seward; Optical: NASA/ESA/ASU/J.Hester & A.Loll; Infrared: NASA/JPL-Caltech/Univ. Minn./R.Gehrz
After massive stars like Eta Carinae
explode, the object left behind is thought to be either a neutron star
or a black hole, depending on the final mass of the progenitor star. Pulsars
are neutron stars that have strong magnetic fields and behave somewhat like cosmic lighthouses, projecting beams of radio emission into space as they spin. Studying the pulses of radiation as the beams sweep past the Earth can provide valuable information on the physics of these extreme objects, allowing astronomers to probe physics under conditions which are not possible to create in a terrestrial laboratory. While pulsars are known to be extremely accurate natural clocks
, their pulse rates are very stable over time, there are however unexplained deviations from the expected spin rate, a phenomenon known as timing noise. Now, a team led by Andrew Lyne at the University of Manchester
, have uncovered a mechanism which could explain this noise.
Over long timescales, the rate at which a pulsar spins (known as the spin down
rate) decreases slowly in a predictable way due to the conversion of rotational energy into photons. By studying a large number of pulsars repeatedly over 40 years, the team found that the deviations from the expected spin down rate were actually quasi-periodic on timescales between one and ten years, and that several other pulsar characteristics may be linked to the same phenomenon. One particular pulsar, known as B1931+24, only displays radio pulses intermittently, and long term study showed that it also had two different spin down rates: its spin rate decreased faster when the radio signal was detectable.
The team analysed the data on a large sample of pulsars and found a further seventeen which show evidence of quasi-periodic spin down rates, many of which also show variations in the shape of the pulse profile. The authors suggest that the likely explanation is that the pulsar's magnetosphere
is switching between two distinct states. Exactly what causes the pulsar to switch between states is not yet known, but if the changes can be accurately modeled then the timing noise can be reduced, and astronomers will find it easier to compensate for errors in pulsar “clocks” in highly sensitive experiments designed to detect gravitational waves
This blog post is a news story from the Jodcast
, aired in the July 2010
edition.Lyne, A., Hobbs, G., Kramer, M., Stairs, I., & Stappers, B. (2010). Switched Magnetospheric Regulation of Pulsar Spin-Down Science, 329 (5990), 408-412 DOI: 10.1126/science.1186683
Posted by Megan on Monday 23rd Aug 2010 (15:04 UTC
) | 1 Comment
Astronomical Awesomeness: Profs and Pints at the Flying Scotsman
Last Tuesday night was the final event in a series of public debates hosted by the Flying Scotsman in Mount Lawley and MC'd by Scitech
(yes, it's taken me a while to get around to posting this). The series was named "Profs and Pints
" and featured local academics and experts in various fields debating with an audience of the general public. The final in the series was titled Astronomical Awesomeness - why we ask why
and featured Prof. Cheryl Praeger
, mathematician extraordinaire from UWA, Carmelo Amalfi
, journalism guru from Murdoch, Carley Tillett, manager of Scitech's planetarium
and all-round space enthusiast, and, erm, me. I'd been to the first of these events a couple of months ago as a spectator and thoroughly enjoyed it, but wasn't looking forward to this one as *I* was going to be on the stage as one of the "Profs" (thanks, Duffy).
Anyone who knows me in Real Life
will have a pretty good idea just how nervous this made me. One of the reasons I started doing outreach in the first place was my dislike of public speaking - when I started my PhD I was very dismayed to find that talking in front of an audience was something I would have to do if I chose to pursue a scientific career. So I started doing bits in the Visitor Centre
and, gradually, I became better at it. I still get *very* nervous (those pterodactyls still play havoc with my guts before I go on stage), and I know I have a long way to go to improve my public speaking (I'll never be anywhere near as good as the likes of Carl Sagan
), but I'm getting better.
This event was something a bit different. It was a public debate with a panel on stage discussing, debating and arguing with an audience over a pint or two. Like the other Profs and Pints events, the evening started with a short speech from each person on the couch explaining their take on the evening's topic, followed by throwing it open to the floor with questions, comments and arguments from the audience, both physical and on Twitter.
Despite my trepidation, in the end it seemed to go ok. Topics covered everything from the risks of space travel, private vs public space programs, science funding, whether scientists do a good job of communicating their work, accountability, the quality of science journalism, science blogging, dark matter, aliens, and much more. The initial speech wasn't the most coherent talk I've ever given, but the discussion was a lot of fun. Listening back to it, I still say "erm" a bit too often, but comparing it to recordings from two years ago I am a lot better these days, which is good, but there's still plenty of room for improvement.
The audience was full of questions and the tweeters among them kept the twitterfall full of entertaining comments (the suggestion of sending Justin Bieber into space was one of my favourites). Afterwards I met a few of them in person: @Grendels
. I didn't know at the time, but @podblack
was also there live-blogging
As with the previous events in the series, ABC 720 were podcasting
the event and Scitech ran a webcast on UStream
. I took my audio recorder too. Should you really want to listen, my recordings of the introduction
and the debate
are here too.
Thanks to Scitech for putting on these events, to the audience for turning up and having fun with the topic, the other members of the panel who were all astronomically awesome, and to "Prof" Duffy for getting me into it in the first place (cheers, mate).
Posted by Megan on Monday 02nd Aug 2010 (15:48 UTC
) | Add a comment