Astropulse is a
volunteer computing
Volunteer computing is a type of distributed computing in which people donate their computers' unused resources to a research-oriented project, and sometimes in exchange for credit points. The fundamental idea behind it is that a modern desktop ...
project to search for
primordial black holes,
pulsars, and
extraterrestrial intelligence (ETI). Volunteer resources are harnessed through
Berkeley Open Infrastructure for Network Computing (BOINC) platform. In 1999, the
Space Sciences Laboratory launched
SETI@home, which would rely on massively parallel computation on desktop computers scattered around the world. SETI@home utilizes recorded data from the
Arecibo
Arecibo (; ) is a Arecibo barrio-pueblo, city and Municipalities of Puerto Rico, municipality on the northern coast of Puerto Rico, on the shores of the Atlantic Ocean, located north of Utuado, Puerto Rico, Utuado and Ciales, Puerto Rico, Ciale ...
radio telescope
A radio telescope is a specialized antenna (radio), antenna and radio receiver used to detect radio waves from astronomical radio sources in the sky. Radio telescopes are the main observing instrument used in radio astronomy, which studies the r ...
and searches for narrow-
bandwidth radio signals from space, signifying the presence of extraterrestrial technology. It was soon recognized that this same data might be scoured for other signals of value to the astronomy and physics community.
Development
For about 6 years, Astropulse existed in an experimental
beta
Beta (, ; uppercase , lowercase , or cursive ; or ) is the second letter of the Greek alphabet. In the system of Greek numerals, it has a value of 2. In Ancient Greek, beta represented the voiced bilabial plosive . In Modern Greek, it represe ...
testing phase not available to the general community. In July 2008, Astropulse was integrated into SETI@home, so that the massive network of SETI participants could also contribute to the search for other astronomical signals of value. Astropulse also makes contributions to the search for ET: first, project proponents believe it may identify a different type of ET signal not identified by the original SETI@Home algorithm; second, proponents believe it may create additional support for SETI by providing a second possible concrete result from the overall search project.
Final development of Astropulse has been a two-part endeavor. The first step was to complete the Astropulse
C++ core that can successfully identify a target pulse. Upon completion of that program, the team created a trial dataset that contained a hidden pulse, which the completed program successfully found, thus confirming the ability of the Astropulse core to successfully identify target pulses. Since July 2008, research has focused on a series of refinements to the beta version which are then rolled out to the full universe of SETI participants. At the programming level, developers first seek to assure that new versions are compatible with a variety of platforms, after which the refined version is optimized for greater speed. As of April, 2009, Astropulse is testing beta version 5.05.
The future of the project depends on extended funding to SETI@home.
The BOINC idea is to divide (split) large blocks of data into smaller units, each of which can be distributed to individual participating work stations. To this end, the project then began to embed the Astropulse core into the SETI beta client and began to distribute real data, split into Astropulse work units, to a team of beta testers. The challenge has been to assure that the Astropulse core will work seamlessly on a broad array of operating systems. Current research focuses on implementing algorithm refinements that eliminate or reduce false positives.
Scientific research
Astropulse searches for both single pulses and regularly repeating pulses. This experiment represents a new strategy for SETI, postulating microsecond timescale pulses as opposed to longer pulses or narrowband signals. They may also discover
pulsar
A pulsar (''pulsating star, on the model of quasar'') is a highly magnetized rotating neutron star that emits beams of electromagnetic radiation out of its Poles of astronomical bodies#Magnetic poles, magnetic poles. This radiation can be obse ...
s and exploding
primordial black holes, both of which would emit brief wideband pulses. The primary purpose of the core Astropulse algorithm i
coherent de-dispersionof the microsecond radio pulses for which Astropulse is searching.
Dispersion of a signal occurs as the pulse passes through the
interstellar medium
The interstellar medium (ISM) is the matter and radiation that exists in the outer space, space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, as well as cosmic dust, dust and cosmic rays. It f ...
(ISM) plasma, because the high frequency radiation goes slightly faster than the lower frequency radiation. Thus, the signal arrives at the radio-telescope dispersed depending upon the amount of ISM plasma between the Earth and the source of the pulse. Dedispersion is computationally intensive, thus lending itself to the distributed computing model.
Astropulse utilizes the distributed computing power of SETI@home, delegating computational sub-tasks to hundreds of thousands of volunteers' computers, to gain advantages in sensitivity and time resolution over previous surveys. Wideband pulses would be "
chirp
A chirp is a signal in which the frequency increases (''up-chirp'') or decreases (''down-chirp'') with time. In some sources, the term ''chirp'' is used interchangeably with sweep signal. It is commonly applied to sonar, radar, and laser syste ...
ed" by passage through the interstellar medium; that is, high frequencies would arrive earlier and lower frequencies would arrive later. Thus, for pulses with wideband frequency content, dispersion hints at a signal's extraterrestrial origin. Astropulse searches for pulses with dispersion measures ranging from to (chirp rates of to per microsecond), allowing detection of sources almost anywhere within the
Milky Way
The Milky Way or Milky Way Galaxy is the galaxy that includes the Solar System, with the name describing the #Appearance, galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars in other arms of the galax ...
.
Project proponents believe that Astropulse will either detect exploding black holes, or establish a maximum rate of , a factor of 10
4 better than any previous survey.
Challenges
Any radio astronomy project confronts issues arising from interference, and the challenges are especially great when the target signals are weak or of transient duration. Military radar noise which is regularly occurring and of known duration can be "blanked" at the radio telescope source. A variety of techniques have been explored in the literature to develop algorithms that detect and account for radar sources that cannot be blanked in this way.
Results
Astropulse started computing in mid-July 2008. , the results have been used in a variety of ways. Development staff, aided by volunteers, have worked to assure that the client works effectively on a broad array of operating systems. Code has been refined and optimized to reduce calculation time on the local work station. Results have been analyzed so that the algorithms can be adjusted to reduce false positives that may result from interference or from random background noise. To date, a target signal has not yet been found.
Potential pulse finds
One goal of Astropulse is to detect postulated mini black holes that might be evaporating due to "
Hawking radiation
Hawking radiation is black-body radiation released outside a black hole's event horizon due to quantum effects according to a model developed by Stephen Hawking in 1974.
The radiation was not predicted by previous models which assumed that onc ...
". Such mini black holes are postulated to have been created during the Big Bang, unlike currently known black holes. The Astropulse project hopes that this evaporation would produce radio waves that Astropulse can detect. The evaporation wouldn't create radio waves directly. Instead, it would create an expanding fireball of high-energy
gamma rays
A gamma ray, also known as gamma radiation (symbol ), is a penetrating form of electromagnetic radiation arising from high energy interactions like the radioactive decay of atomic nuclei or astronomical events like solar flares. It consists o ...
and particles. This fireball would interact with the surrounding magnetic field, pushing it out and generating radio waves.
Rotating radio transients (RRATs) are a type of neutron stars discovered in 2006 by a team led by
Maura McLaughlin from the
Jodrell Bank Observatory
Jodrell Bank Observatory ( ) in Cheshire, England hosts a number of radio telescopes as part of the Jodrell Bank Centre for Astrophysics at the University of Manchester. The observatory was established in 1945 by Bernard Lovell, a radio as ...
at the
University of Manchester
The University of Manchester is a public university, public research university in Manchester, England. The main campus is south of Manchester city centre, Manchester City Centre on Wilmslow Road, Oxford Road. The University of Manchester is c ...
in the UK. RRATs are believed to produce radio emissions which are very difficult to locate, because of their transient nature. Early efforts have been able to detect radio emissions (sometimes called RRAT flashes) for less than one second a day, and, like with other single-burst signals, one must take great care to distinguish them from terrestrial radio interference. Distributing computing and the Astropulse algorithm may thus lend itself to further detection of RRATs.
Pulses with an apparent extragalactic origin have been observed in archived data. It is suggested that hundreds of similar events could occur every day and, if detected, could serve as cosmological probes. Radio pulsar surveys such as Astropulse-SETI@home offer one of the few opportunities to monitor the radio sky for impulsive burst-like events with millisecond durations. Because of the isolated nature of the observed phenomenon, the nature of the source remains speculative. Possibilities include a black hole-
neutron star
A neutron star is the gravitationally collapsed Stellar core, core of a massive supergiant star. It results from the supernova explosion of a stellar evolution#Massive star, massive star—combined with gravitational collapse—that compresses ...
collision, a neutron star-neutron star collision, a black hole-black hole collision, or some phenomenon not yet considered.
However, in 2010 there was a new report of 16 similar pulses from the Parkes Telescope which were clearly of terrestrial origin.
Previous searches by SETI@home have looked for extraterrestrial communications in the form of narrow-band signals, analogous to our own radio stations. The Astropulse project argues that since we know nothing about how ET might communicate, this might be a bit closed-minded. Thus, the Astropulse survey can be viewed as supplementing the narrow-band SETI@home survey as a by-product of the search for physical phenomena.
RF radiation from outer space was first discovered by
Karl G. Jansky (1905–1950), who worked as a radio engineer at the Bell Telephone Laboratories to studying radio frequency interference from thunderstorms for Bell Laboratories. He found "...a steady hiss type static of unknown origin", which eventually he concluded had an extraterrestrial origin. Pulsars (rotating neutron stars) and
quasar
A quasar ( ) is an extremely Luminosity, luminous active galactic nucleus (AGN). It is sometimes known as a quasi-stellar object, abbreviated QSO. The emission from an AGN is powered by accretion onto a supermassive black hole with a mass rangi ...
s (dense central cores of extremely distant galaxies) were both discovered by radio astronomers. In 2003 astronomers using the
Parkes radio telescope
A radio telescope is a specialized antenna (radio), antenna and radio receiver used to detect radio waves from astronomical radio sources in the sky. Radio telescopes are the main observing instrument used in radio astronomy, which studies the r ...
discovered two pulsars orbiting each other, the first such system known. Explaining their recent discovery of a powerful bursting radio source, NRL astronomer Dr. Joseph Lazio stated:
"Amazingly, even though the sky is known to be full of transient objects emitting at X- and gamma-ray wavelengths, very little has been done to look for radio bursts, which are often easier for astronomical objects to produce." The use of coherent dedispersion algorithms and the computing power provided by the SETI network may lead to discovery of previously undiscovered phenomena.
Astronomy in the schools
Astropulse and its older partner, SETI@home, offer a concrete way for secondary school science teachers to involve their students with astronomy and computing. A number of schools maintain volunteer computing class projects.
References
External links
Related websites
Astropulse ScienceVon Korff, Astropulse: A Search for Microsecond Transient Radio Signals Using Distributed ComputingAstropulse FAQWebsiteSETI@home forum thread about AstropulseSETI@home Beta forum thread about AstropulseAstropulse WikiElectromagnetic RadiationA multibeam sky survey
For teachers and students
Basics of Radio AstronomySETI Science Links
{{DEFAULTSORT:Astropulse
Free astronomy software
Berkeley Open Infrastructure for Network Computing projects
Volunteer computing projects