Starship Asterisk*

Posted: **Mon Feb 01, 2010 9:41 pm**

Is M82, the "Cigar Galaxy," one of the "active" galaxies that are considered a source of high-energy cosmic rays?

--Bill

Posted: **Mon Feb 01, 2010 11:10 pm**

Westwind wrote:Is M82, the "Cigar Galaxy," one of the "active" galaxies that are considered a source of high-energy cosmic rays?

Possibly.

http://apod.nasa.gov/apod/ap080325.html
http://asterisk.apod.com/viewtopic.php? ... m82#p92316
http://asterisk.apod.com/viewtopic.php? ... 82#p114228

However, Centaurus A (NGC 5128) is a much more likely source for Ultra-high-energy cosmic ray (UHECR).
Unlike the slightly more distant M82, NGC 5128 is a non-starburst radio galaxy with an Active Galactic Nuclei.

http://en.wikipedia.org/wiki/Cosmic_rays wrote:
<<Cosmic rays are energetic particles originating from outer space that impinge on Earth's atmosphere. Almost 90% of all the incoming cosmic ray particles are simple protons. The variety of particle energies reflects the wide variety of sources. The origins of these particles range from energetic processes on the Sun all the way to as yet unknown events in the farthest reaches of the visible universe.

Ultra-high-energy cosmic ray (UHECR) have energies of over 10²⁰ eV. The source of UHECR has been a mystery for many years. Results from the Pierre Auger Observatory show that UHECR arrival directions appear to be correlated with extragalactic supermassive black holes at the center of nearby galaxies called active galactic nuclei (AGN). UHECR might be protons accelerated to those energies by magnetic fields associated with the rapidly growing black holes at the AGN centers. Interactions with blue-shifted cosmic microwave background radiation limit the distance that these particles can travel before losing energy.>>

Posted: **Tue Feb 02, 2010 3:05 am**

Thanks, Art. I was hoping to use M82 as an example of possible sources for cosmic rays. We have a public star party coming up next month, and M82's location near the Big Dipper would have made it a perfect example for use with a laser pointer.

I'll have to try something else.

--Bill

Posted: **Tue Feb 02, 2010 3:23 pm**

Does anyone have a list of "active" galaxies that are considered possible sources of cosmic rays? I've tried an Internet search and have found information about active galaxies and cosmic rays, etc., but so far haven't been able to find a list of active galaxies.

Our astronomy club is giving four public star parties this summer for the local county park system. We usually get a good turnout of young families with children of varying ages. I would like to be able to point out some object in the night sky and mention it as a possible source of cosmic rays, etc. I think that adding bits of information about the objects people are viewing makes stargazing more interesting. And I enjoy it, too.

Can anyone help?

--Bill

Posted: **Tue Feb 02, 2010 4:19 pm**

You might try the Pierre Auger Observatory at http://auger.colostate.edu/ or http://www.auger.org/.

You could do an APOD Search for active galaxy or cosmic ray.

Posted: **Tue Feb 02, 2010 4:34 pm**

Thanks for your suggestions!

--Bill

Posted: **Tue Feb 02, 2010 4:38 pm**

There's lots of active galaxies listed on APOD but the only one I could find specifically for gamma rays was the aforementioned Centaurus A. There are a lot more if you include x-rays.

Posted: **Tue Feb 02, 2010 8:31 pm**

Thanks. I'm looking for sources of intergalatic cosmic rays. I know about Centaurus A, but it appears to be at or below our horizon throughout the year. Not good for my purpose.

I would like to find an active galaxy near an easily recognized constellation that I can point to with my laser at public star parties and identify as a likely source of cosmic rays.

I was hoping M82 would work, but it may not be a defined active galaxy, even though it is a "starburst" galaxy with lots of star formation.(??)

--Bill

Posted: **Tue Feb 02, 2010 8:51 pm**

Posted: **Wed Feb 03, 2010 12:23 am**

geckzilla,

Thanks very much for your help! I'll check the sources you cited. I would be delighted if M82 qualifies as an active galaxy.

--Bill

P.S. I'm in northeast Ohio in the U.S., latitude 41 north.

Posted: **Thu Feb 11, 2010 7:52 pm**

Thanks to the Pierre Auger Observatory and to forum members here for help in locating an "active" galaxy that I can refer to in my park-system presentation, and then point to with my laser in the stargazing session that follows.

The Pierre Auger staff suggested using elliptical galaxy M87 for my example. It not only is active but it also features a focused sychrotron energy jet that is about 5 million light years long. If we have clear skies when I give my talk on March 20, M87 should be visible to the east of Saturn.

--Bill

Starship Asterisk*

Nature of M82?

Nature of M82?

Re: Nature of M82?

Re: Nature of M82?

List of Active Galaxies?

Re: List of Active Galaxies?

Re: List of Active Galaxies?

Re: List of Active Galaxies?

Re: List of Active Galaxies?

Re: List of Active Galaxies?

Re: List of Active Galaxies?

Thanks for Help