Eta Carinae - Brightening??????

[Merlin66 (Ken)]

I just noted on a thread over here in the UK that it was suggested the Eta was "brightening" - never heard or seen anything.... anyone confirm or has details???

Ken

[CoolhandJo (Paul)]

Funny you should mention that! Check out what "Ausie Observer" posted in this thread! Claims Eta Carina is brighter !

http://stargazerslounge.com/picture-...8-04-10-a.html

[Suzy]

Funny you should mention this. I have been studying Eta Carinae for the last 4 months and three weeks ago I noticed that the star and it's associated nebula was amazingly bright. I have been searching ever since for any news on this but to no avail, until I came across this thread. Is there any information out there on it? As I'm new to this hobby (4 months), I just wasn't sure, but I knew that night it was spectacular. Unfortunately, since that observation, clouds and bad weather since have gotten in the way of me being able to take another look.

[bojan]

Originally Posted by Suzy

... I noticed that the star and it's associated nebula was amazingly bright......

Hmmm it must be something different... perhaps just your perception.
Nebula is huge (will check later for actual size) and any transient on eta itself (sudden brightening) will take quite some time to propagate through the nebula.

EDIT:
OK, found it.. the homunculus is ~40 light-days in diameter.. so, for the transient to propagate through would take couple of weeks.. so the nebula brightening (but delayed compared with eta itself) is plausible.

[PeterM]

If we are indeed (extremely) lucky in our lifetimes and we are to witness a Supernova in the MilkyWay then Eta Carinae would be a great candidate.
Since brightening back in around the late 1830s to early 1840s (it became as bright as about Sirius) it then faded to something like mag 8, I think and its brightness has been climbing since. Being estimated at 100-150 times the mass of the Sun then I guess if it goes, it goes Hypernova and at around 7500 light years away would certainly put on a nice show.
This is perhaps the most monitored star in the heavens both by professionals, amateur imagers and visual observers alike (see the links below).
Over the years I have often heard Kevin Dixon (SAS in Qld) talk of a brightening of the envelope that surrounds the star, people doubted him even when they looked at it , only to be followed by official confirmation on various sites of what he was seeing. So who knows, heck I haven't seen the sky in weeks. So maybe Suzy you have just seen the trailers so to speak before the main event, put me down for a ticket right in the front row. But don't observe it through a telescope as I understand from reading someones posts here a while ago its' concentrated laser like light would apparently be blinding, must find that post and use it as a programme of what to expect....let the show begin, on time please!

PeterM.

Radio outburst
http://www.astro.umd.edu/~white/imag...time_full.html

Optical monitoring

http://etacar.fcaglp.unlp.edu.ar/

[bojan]

Laser? no...
Supernova (hypernova) light will not be collimated like laser (Laser light is coherent and it has only one wavelength.. that is why it can be dangerous because it can be focused on a very small area of the retina).
Also, laser output power considered as dangerous is close to 1mW.. I am not sure now what is the power flux of a star of, say, 0 mag.. ( i have seen the numbers somewhere) but I feel it is way lower than 1mW (possibly pW? or even less)

[PeterM]

Thanks Bojan,
I have often wondered about that after reading in a well known amateurs post here on Ice In Space. I may have taken liberties on the "laser like" I think it was maybe concentrated into a point source but it was clear re the blinding light, which I know they backed up with some research. Unfortunately they don't post here anymore and just did a search and their posts seem to have all gone.
PeterM.

[bojan]

Here are some numbers for the start:
Sun's output is 1.3kW/m2 (above atmosphere, of course).
Sun's apparent magnitude is -29.
So, star of magnitude 0 has 2.5^29 lowr power flux, which is 0.000000003746994889972252672 W/m2, or 3.7nW/m2
This means, 10" mirror will collect ~0.23nW... very small power indeed, and this will be over the whole spectral bandwidth (so with apsorption in the atmosphere, this will be way below this value).
Now, this is for a star of mag 0.
It all depends how bright eta will be when it goes off :-)

[astroron (Ron)]

Surely it wont be mag 5.4 one second, then mag -8 the next?
From what I understand it would take a little time to brighten to it's brightest?

[astroron (Ron)]

The common perception is that Eta is a double star and does brighten over a five year period but I think more in the infrared.
It has been brightening over the last maybe 20 years or so?
From my place here in Cambroon I have noticed that it is now quite easy to see the Star! naked eye, I could not see it naked eye when I first moved here in 1990.
That said I would hazard a guess that the brightening seen at the present moment is just the quality of the Transparency/seeing by the observer.
I would imagine that the professionals would have noticed by now and it would be broadcast to the astronomical community

[PeterM]

I found this link in which Sydney Observatories Nick Lomb also appears to raise the possibility of danger to eyesight. Interesting, has me digging for more info now to see how this notion comes about. Could there be more to this than meets the eye? Should have done it when the other person posted I guess.
http://www.sydneyobservatory.com.au/blog/?p=344

PS. Ron raises a very good point re seeing and transparency at the time of observations. Perhaps checking any perceived brightness increases against the links provided and see how well they match might give an indication.



PeterM.

[astroron (Ron)]

Originally Posted by PeterM

I found this link in which Sydney Observatories Nick Lomb also raises the possibility of danger to eyesight. Interesting, has me digging for more info now.
http://www.sydneyobservatory.com.au/blog/?p=344

PeterM.

Peter just a bit of news, Nick Lomb has retired, but still does a bit of on line work

[Steffen]

Originally Posted by PeterM

I found this link in which Sydney Observatories Nick Lomb also appears to raise the possibility of danger to eyesight.

Hmm, what magnitude is it supposed to reach then? The Moon at -13m isn't dangerous to the naked eye, the Sun at -27m obviously is. Is Eta Carinae expected to go brighter than -13m when is goes supernova??

Cheers
Steffen.

[bojan]

The problem is also, Moon light is spread over large area. while Eta will be point-like.. and if all the light form it is focussed on single receptor in the eye, it may burn it (provided there is enough power for this to happen).
-13m may be dangerous it this respect, especially if telescope is used. I will do some more calc.

[PeterM]

Eta, at 4 million times brighter than the Sun so it will be bright, incredible. I've seen estimates at least as bright (not as large) as the full Moon, being able to read by it at night etc. Seems SN2006gy (NGC1260) about the same mass as Eta, instantly put out as much energy as the Sun does in 10 billion years.

PeterM.

[astroron (Ron)]

Is brightness equated with heat? I have observed a mag -7 iridium flair only maybe for a couple of seconds? and it did not as far as I am aware do any damage.
Would looking at a point source such as a mag minus thirteen star actually burn your eye?
I have had someone set off a camera flash very close to my 16" scope when I was observing, which other than being like the effect at looking at the Moon was all the effect I got.

[PeterM]

I think its more concentrating that amount of light onto the eye (ie Moon) as a point source, it will damage your eye. Happy to be corrected on this.
PeterM.

[astroron (Ron)]

If I was to Look at the Full Moon through my 16" with a 9 mm eyepiece but concentrated the light through a pin hole would that not be the same thing as looking at a star exploding 7000 lights away?
I know the Moon light is reflected light, maybe that could be the difference

PS I am not going to try it

[PeterM]

Suppose could be same as saying "equal in brightness to a 150 watt spotlight" as in your security lights. Ok you can look at that for a short while before it becomes uncomfortable, but squeeze all that light into a point source and look at it through a telescope and I think it would be more than uncomfortable.
PeterM.

[bojan]

Guys, it all depends on power density on the retina and amount of energy delivered per square mm of retina..
When I'm through with some basic math I will be back with numbers...