Radio Supernovae and the ATA

by Paul Gilster on May 28, 2009

We think of the Allen Telescope Array, currently comprising only 42 of the 350 radio dishes planned, as a SETI instrument, capable of digging faint signals out of a wider field of stars than ever before. But the ATA is also engaged in an astrophysical survey of the sky at radio wavelengths, one that will look for radio bursts from supernovae. A glimpse of what it is looking for has just been reported in M82, a small irregular galaxy about twelve million light years from Earth.

We’re talking about a so-called ‘radio supernova,’ an exploding star undetectable by optical or X-ray telescopes. The new object is the brightest supernova seen in radio wavelengths in the last twenty years, and one of only a few dozen of its kind observed so far. And while the ATA will help us locate future radio objects of its kind, this one was found with the Very Large Array in New Mexico, and later confirmed through the NRAO’s Very Long Baseline Array.

radio_m82sn_engl_nocoin_small

Image (click to enlarge): Zooming into the center of the galaxy M82, one of the nearest starburst galaxies at a distance of only 12 Million light years. The left image, taken with the Hubble Space Telescope (HST), shows the body of the galaxy in blue and hydrogen gas breaking out from the central starburst in red. The VLA image (top left) clearly shows the supernova (SN 2008iz), taken in May 2008. The high-resolution VLBI images (lower right) shows an expanding shell at the scale of a few light days and proves the transient source as the result of a supernova explosion in M82. Credit: Milde Science Communication, HST Image: /NASA, ESA, and The Hubble Heritage Team (STScI/AURA); Radio Images: A. Brunthaler, MPIfR.

Both the VLA and the VLBA have narrow fields of view, but the ATA will offer full-sky scanning on a daily basis, and will be able to find objects ten times fainter than this radio supernova. In the process, we’ll learn much about how radio supernovae work even as we continue the hunt for life around other stars. All of this should bring a more cohesive approach to the study of these objects, says Geoffrey Bower (UC-Berkeley):

“This supernova is the nearest supernova in five years, yet is completely obscured in optical, ultraviolet and X-rays due to the dense medium of the galaxy. This just popped out; in the future, we want to go from discovery of radio supernovas by accident to specifically looking for them.”

A supernova can produce radio emissions when it’s found in an active region of star formation, where the density of gas and dust is high — that very gas and dust is, of course, the reason why it is so hard to detect these objects in optical, ultraviolet and X-ray wavelengths. Those supernovae that have not lost large parts of their envelope before collapsing to form a neutron star or black hole produce few radio emissions.

The team has found indications of a ring structure produced by a shock wave around this object, one that has grown to about 2000 AU across and is consistent with a year-old supernova. Astronomers hope the emissions from these objects will offer up information about how stars explode and how their cores collapse. Debris colliding with the stellar wind should provide rich data to observers, while the ATA’s ongoing survey should take us deep into the realm of transient and variable sources.

The paper is Brunthaler et al., “Discovery of a bright radio transient in M82: a new radio supernova?,” accepted at Astronomy & Astrophysics and available online. More in this news release from the Max-Planck-Institut für Radioastronomie.

{ 6 comments }

bigdan201 May 28, 2009 at 14:26

This is why its important to look at the sky using all wavelengths. Radio astronomy helps paint a fuller picture of the skies.

James M. Essig May 29, 2009 at 22:45

Hi Folks;

Imaging the sky at all wavelengths can help us map the distribution of primordial hydrogen and helium, a very important consideration when designing future version of interstellar ramjets. If we can map out the density concentrations of such gas, then perhaps fusion powered ISRs can be given a good look again, and certainly ISRs that are able to convert mass almost entirely into energy by some unspecified process.

I like to say, before we plan our travels, we must have a road map and due to the emmission spectra of interstellar hydrogen and helium, RF astronomy has added importance in mapping the visible cosmos

Pat Galea May 30, 2009 at 13:35

James, good call. Road maps would be essential for ISRs. I imagine they would also be essential for *any* ship that travels at significantly high speeds!

Can we get a genuine 3-D model of interstellar H & He? From our vantage point, it feels like we could only get 2-D spherical info i.e. readings from every point of the sky, but not from various distances outward. I assume that what we do is we map the readings we get onto the objects we know are there.

However, I know enough of other areas of astronomy to know that there are all kinds of clever hacks to extract seemingly unobtainable information. :-)

ljk June 4, 2009 at 9:21

VB 10: A Large Planet Orbiting a Small Star

Illustration Credit: JPL-Caltech, NASA

Explanation: Can a planet be as large as the star that it orbits? Recent observations have discovered that nearby Van Biesbroeck’s star might have just such a large planet. Although VB 10 lies only about 20 light years away, it is a small red dwarf star so dim, at 17th magnitude, that a telescope is needed to see it.

Van Biesbroeck’s star was previously known for its rapid proper motion across the sky — it moves so fast it could cross a full moon in only about 1,000 years. By noting a wiggle in VB 10′s sky trajectory, astronomers were able to infer the existence of a planet several times the mass of Jupiter.

Although the star VB 10 is perhaps 10 times more massive than the discovered planet VB 10b, the star is likely more highly compressed and so the two might be closely matched in size. Such a system is envisioned above with an artist’s illustration. Since faint M-type stars like VB 10 are so common, planetary systems surrounding them, including planets larger than their parent star, might be more common than planetary systems like our own Solar System.

http://antwrp.gsfc.nasa.gov/apod/ap090603.html

ljk June 15, 2009 at 22:36

Radio quiet, please! – protecting radio astronomy from interference

Authors: W. van Driel

(Submitted on 12 Jun 2009)

Abstract: The radio spectrum is a finite and increasingly precious resource for astronomical research, as well as for other spectrum users. Keeping the frequency bands used for radio astronomy as free as possible of unwanted Radio Frequency Interference (RFI) is crucial.

The aim of spectrum management, one of the tools used towards achieving this goal, includes setting regulatory limits on RFI levels emitted by other spectrum users into the radio astronomy frequency bands. This involves discussions with regulatory bodies and other spectrum users at several levels – national, regional and worldwide.

The global framework for spectrum management is set by the Radio Regulations of the International Telecommunication Union, which has defined that interference is detrimental to radio astronomy if it increases the uncertainty of a measurement by 10%.

The Radio Regulations are revised every three to four years, a process in which four organisations representing the interests of the radio astronomical community in matters of spectrum management (IUCAF, CORF, CRAF and RAFCAP) participate actively.

The current interests and activities of these four organisations range from preserving what has been achieved through regulatory measures, to looking far into the future of high frequency use and giant radio telescope use.

Comments: To appear in IAU Symposium 260 The Role of Astronomy in Society and Culture, 8 pages

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

Cite as: arXiv:0906.2268v1 [astro-ph.IM]

Submission history

From: Wim van Driel [view email]

[v1] Fri, 12 Jun 2009 14:20:27 GMT (2679kb,D)

http://arxiv.org/abs/0906.2268

ljk August 13, 2009 at 10:20

http://www.technologyreview.com/blog/arxiv/23983/

Thursday, August 13, 2009

First Results From The Allen Telescope Array

No word from ET (yet) but some useful data that could help solve one the great mysteries about star formation

The Allen Telescope Array, a few hundred miles north of San Francisco, is one of the world’s most unusual and innovative radio telescopes. When completed, the facility will consist of 350 dishes , each just 6 metres in diameter. This provides it with a huge angle of view of some 2.5 degrees, some 17 times larger than its nearest rival. It is also able to monitor simultaneously an unprecedented range of radio frequencies from 0.5 to 11.2 GHz.

The facility is a joint operation between the SETI Institute in Mountain View and the University of California, Berkeley, which determines where to point it. Wherever the array points, its large angle of view means that several stars of interest to the SETI Institute can always be studied as well.

The facility began operating in 2007 with an array of 42 dishes and today the team have posted an interesting update of its first results and progress towards its various scientific goals.

The highlight is the images it has made of the movement of atomic hydrogen clouds in the intergalactic space between nearby galaxies, whihc could help solve one of the big mysteries of star formation.

Many galaxies do not appear to contain enough gas to sustain star formation in the way astronomers expect. That’s a puzzle but atomic hydrogen may be the solution. Astronomers do not include atomic hydrogen gas in the reservoir from which they make their calculations because the gas is found largely in intergalactic regions where star formation does not take place.

What the Allen Array team are looking for is evidence that atomic hydrogen clouds are sucked into star forming regions of galaxies where they can contribute to stellar formation.

That’s interesting stuff and may yield some fascinating results in the near future.

But no word yet on any broadcasts from ET.

Ref: http://arxiv.org/abs/0908.1175: The Allen Telescope Array: The First Widefield, Panchromatic, Snapshot Radio Camera

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