Super Planetary Nebulae

August 14, 2009 by Robert Massey
Super Planetary Nebulae

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An optical image from the 0.6-m University of Michigan/CTIO Curtis Schmidt telescope of the brightest Radio Planetary Nebula in the Small Magellanic Cloud, JD 04. The inset box shows a portion of this image overlaid with radio contours from the Australia Telescope Compact Array. The planetary nebula is a glowing record of the final death throes of the star. (Optical images are courtesy of the Magellanic Cloud Emission Line Survey (MCELS) team).

(PhysOrg.com) -- A team of scientists in Australia and the United States, led by Associate Professor Miroslav Filipović from the University of Western Sydney, have discovered a new class of object which they call “Super Planetary Nebulae.” They report their work in the journal Monthly Notices of the Royal Astronomical Society.

Planetary nebulae are shells of gas and dust expelled by stars near the end of their lives and are typically seen around stars comparable or smaller in size than the Sun.

The team surveyed the Magellanic Clouds, the two companion galaxies to the Milky Way, with of the Commonwealth Scientific and Industrial Research Organisation (CSIRO) Australia Telescope National Facility. They noticed that 15 radio objects in the Clouds match with well known planetary nebulae observed by optical telescopes.

The new class of objects are unusually strong radio sources. Whereas the existing population of planetary nebulae is found around small stars comparable in size to our Sun, the new population may be the long predicted class of similar shells around heavier stars.

Filipović’s team argues that the detections of these new objects may help to solve the so called “missing mass problem” - the absence of planetary nebulae around central stars that were originally 1 to 8 times the mass of the Sun. Up to now most known planetary nebulae have central stars and surrounding nebulae with respectively only about 0.6 and 0.3 times the mass of the Sun but none have been detected around more massive stars.

The new Super Planetary Nebulae are associated with larger original (progenitors), up to 8 times the mass of the Sun. And the nebular material around each star may have as much as 2.6 times the mass of the Sun.

“This came as a shock to us”, says Filipović, “as no one expected to detect these object at radio wavelengths and with the present generation of radio telescopes. We have been holding up our findings for some 3 years until we were 100% sure that they are indeed Planetary Nebulae”.

Some of the 15 newly discovered planetary nebulae in the Magellanic Clouds are 3 times more luminous then any of their cousins. But to see them in greater detail astronomers will need the power of a coming radio telescope - the Square Kilometre Array planned for the deserts of Western Australia.

More information: http://www3.inters … 603/abstract

Provided by Royal Astronomical Society (news : web)

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yyz
Aug 14, 2009

Rank: 5 / 5 (1)
A preprint of this paper entitled "Radio Planetary Nebulae in the Magellanic Clouds" was recently posted at the arXiv site: http://arxiv.org/...88v1.pdf . A very interesting discovery but I doubt that the small number of known 'super PNe' would only make no more than a small dent in the 'missing mass' problem.
frajo
Aug 15, 2009

Rank: 1 / 5 (1)
This is very interesting. How can there still be electromagnetically undetected objects in the vicinity of our Local Group?

Obviously, we don't know the complete galactic inventory. Worse - we don't even know the initial inventory, do we? (Because we don't know the beginnings of a galaxy.)



An inventory sorted according to mass and temperature is needed.

Only then let there be models describing the evolution of that inventory in space and time.

May be that way we can draw conclusions which parts of the inventory are visible, i.e. detectable to electromagnetic receptors, and what percentage of the whole inventory is invisible in the electromagnetic spectrum.



In this picture, there is no need for any mythical "Dark Matter", consisting of some hitherto unknown kind of elementary particles.

It just seems to be naive to assume that more than a few percent of the complete inventory is visible at any given time.
Fazer
Aug 15, 2009

Rank: 5 / 5 (1)
I don't think they are talking about the universe-scale dark matter theory here. I think what they mean is that larger nebulae have been expected to exist, but not found, thus a specific species of nebulae was considered to be 'missing', until now.

From the linked abstract:

"We argue that these detections may help solve the 'missing mass problem' in PNe whose central stars were originally 1%u20138 M"
omatumr
Aug 15, 2009

Rank: 1 / 5 (4)
SUPERNOVA => PULSAR PLANET => PLANET EARTH

How sad that it has taken astronomers 35 years to acknowledge that:"Planetary nebulae are shells of gas and dust expelled by stars near the end of their lives and are typically seen around stars comparable or smaller in size than the Sun."

Yes, indeed! That is exactly the scenario of events that produced the iron-rich planet Earth orbiting an iron-rich Sun (a supernova remnant) - as first revealed by measurements made over three decades ago!

1. "Elemental and isotopic inhomogeneities in noble gases: The case for local synthesis of the chemical elements", Transactions of the Missouri Academy of Sciences 9 (1975) 104-122.

2. "Strange xenon, extinct superheavy elements and the solar neutrino puzzle", Science 19 (1977) 208-209.

3. "Isotopes of tellurium, xenon and krypton in the Allende meteorite retain record of nucleosynthesis", Nature 277 (1979) 615-620.

With kind regards,
Oliver K. Manuel
http://www.omatumr.com
yyz
Aug 15, 2009

Rank: not rated yet
@Fazer: You're correct about the 'missing mass' relating to massive progenitors of planetary nebulae and not the cosmological 'missing mass'. As the paper I linked to above noted, these new massive radio PNe were predicted to exist along the AGB but had yet to be discovered. My mistake for confusing their use of the term 'missing mass'.
smiffy
Aug 16, 2009

Rank: not rated yet
Seems odd that this new class of nebula were discovered outside of the Milky Way galaxy, at a distance of 150,000 light years (a third as much again as the diameter of the Milky Way disc). If I've read this article right it seems to be suggesting this type of nebula is specific to dwarf galaxies, and that therefore dwarf galaxies are different in more ways than just size? Or is it that observatiomal problems like dust explain the lack of home galaxy sightings? (Though the fact that these observations were RF should discount the dust problem.)
Fazer
Aug 17, 2009

Rank: 5 / 5 (1)
It caught me off gaurd, too, when I first read it, yyz...'missing mass' is such a debated topic these days.

smiffy, I was surprised as well by the fact that they would make such a large discovery by looking OUTSIDE the Milky Way. It does seem counterintuitive.
yyz
Aug 18, 2009

Rank: 5 / 5 (1)
The astronomers conducting this study chose to look at planetary nebulae in the Magellanic Clouds in order to reduce confusion of these objects with with the much more numerous number of sources that could mimic or be confused with the 'heavy' planetary nebulae in our own galaxy. Confusion of sources within our galaxy( planetaries in our galaxy are mainly seen in or near the plane of the Milky Way ) could produce a large number of false-positive detections. Observations away from the galactic plane (such as the Magellanic Clouds) make it easier to spot these objects. Also, these radio observations were cross-correlated with infrared and visible light sources, again making observations away from the galactic plane less prone to 'source confusion'.

smiffy, planetary nebulae occur at roughly the same frequencies in dwarf galaxies as in larger spiral or elliptical galaxies. As noted above, the researchers observed these relatively nearby planetary nebulae in the Magellanic Clouds in order to reduce false-positive detections.
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planetary nebula, stars, magellanic clouds, milky way, radio telescopes
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