Citizen Scientists Discover New Pulsar With Einstein@Home
By Matthew T. Dearing
| August 14th 2010 08:57 PM | Print
You must be quite familiar with what happens when you toss a pebble into a pond. You might describe the simple event as a massive rotating object splashing into a deformable fluid. Or, you might… not. However, astronomical bodies are like these pebbles sloshing around in a deformable fluid, called space-time, and this interaction, too, can produce those expected waves extending out from where the pebble drops.
So claimed Albert Einstein in 1916 when he hypothesized that the universe is filled with special waves, called gravitational waves, that are the rippling effects from stars, pulsars, and black holes… all of which are the massive pebbles in our little pond of the Universe.
These waves of space-time, however, have never yet been directly observed. So, the phenomena, although it might seem reasonable, remains only a hypothesis. This is where the Laser Interferometer Gravitational Wave Observatory, or LIGO, comes into play.
Operated by CalTech and MIT, the LIGO device is a giant interferometer, which uses lasers bouncing off mirrors to try to detect changes in the interference patterns of superimposing waves. In this case, LIGO is looking for interference patterns in gravitational waves. For example, let’s imagine two neutron stars far far away that have been stably orbiting one another for a really long time. One day, they fall into one another and merge into a single massive body. That’s a really big pebble splashing into the space-time pond, and the result might be sinusoidal ripples pouring outward from the collision. Eventually, these ripples–which apparently don’t diminish much as they traverse through space-time–come rolling toward Earth, like a tsunami of space-time.
The waves, then, will pass through the LIGO interferometer detectors, which are zapping laser beams back-and-forth and precisely measuring the intensity and time of travel of the beams, and temporarily alter the local structure (or flow) of space-time thereby altering both the physical and temporal paths taken by the high-precision lasers. The detectors record an unexpected time of travel between laser reflections, and so something must of happened to space-time! (Learn more about how LIGO actually works.)
Now, a whole lot of data comes out of this sort of detector. We’re talking 24/7/365 measurements of precision-timed instruments that are looking for a nearly random event that could occur at any instant in time; at time which would be nearly impossible to predict and prepare for. So, you might image that analyzing a constant stream of dense data such as that from LIGO would require a great deal of computation time and resources.
And, this is where the mighty citizen scientist comes into play. Since 2005, citizen scientists have had the opportunity through Einstein@Home to help process all of this data collected from the LIGO gravitational wave detector in addition to radio signals from the Arecibo Observatory in Puerto Rico. By simply installing a convenient interface program on the computer, the system quietly cranks through all of the radio data and interferometric information, and looks for signs of astronomical pebbles that might be the source of gravitational waves.
Constructed image of gamma rays from the Vela pulsar, spinning at 11 times per second. Courtesy Wikimedia Commons. Currently, the Einstein@Home analysis is largely focused on the radio data from Arecibo. The idea with this focus is to first detect interesting pulsar systems that can be later used for directly tuning into for dedicated gravitational wave detection. Pulsars are rather exciting massive astronomical pebbles (dense neutron stars) that have extremely large magnetic fields and actually spin at crazy fast rates. These stars are typically 1 1/2 to 2 times the mass of our sun, but about 60,000 times smaller in size. They spin at high rates thanks to the conservation of angular momentum; the large spinning star shrinks in size, so the spinning speeds up, just like the ice skater pulling in her arms to gain speed (view a demonstration). As recently as last month, and just published in Science Express (read the abstract), the Einstein@Home team and their participating citizen scientists had their first major discovery. With the analysis from the computers of an American couple, Chris and Helen Colvin, of Ames, Iowa, and a German, Daniel Gebhardt, of Universität Mainz, Musikinformatik, along with the important "ah-ha!" moment from a dedicated graduate student, Benjamin Knispel, a new, and interesting pulsar was discovered. The pulsar is cleverly named PSR J2007+2722, and is special because it apparently rotates at a whopping 41 times per second, it has an unusually low magnetic field, and it spins alone. Most pulsars discovered to date exist with a companion neutron star orbiting about one another. J2007+2722 likely once had a partner, but it may have escaped or blew up in an unpleasant breakup. Einstein@Home discovery plot. Left: significance as a function of DM and spin frequency (all E@H results for the discovery beam). Right: the pulse profile at 1.5 GHz (GBT). The bar illustrates the extent of the pulse. Courtesy AEI Hannover. The discovery was taken from a five minute segment of Arecibo radio data recorded in 2007, but the candidate event was just realized last month after it had made its rounds through the Einstein@Home computer network. Subsequent observations were taken by other observatories, and the candidate pulsar was quickly confirmed. The results having been published in just a little over one month, this discovery is not only an example of a wonderful connection between citizen scientists and professionals, but also demonstrates incredible–and maybe a little rare–efficiency in the science discovery-to-press timeline.
The ultimate goal at this point for the Einstein@Home team is to discover a pulsar orbiting another object with a fast period, say, less than one hour. With this astronomical laboratory tagged, they would be able to closely monitor the system with many observatories at the same time collecting a dense array of information, which could then all be used to test Einstein’s general theory of relativity and his predicted gravitational waves. The second goal is to find a pulsar orbiting a black hole allowing the scientists to explore the unknown space-time directly around the black hole, and thereby having a rather direct look into the mysterious dark pit that defies so much common sense and gives us extreme wonder as to the incredible nature of our Universe.
And, all of these grand adventures probing some of the most fundamental issues of all of physics can be experienced and directly influenced by the citizen scientist. If you would like to participate in basic physics research, simply download the BOINC
computing platform, and register (for free) with Einstein@Home
. With a little luck, and a lot of background computing time, maybe you, too, can personally contribute the needed resources to discover the next game-changing observation in astrophysics.