Flaming Star – The Sky is on Fire!

Flaming Star

When working on the atomic bomb in 1942, Edward Teller (fellow Hungarian) raised the possibility that a nuclear explosion might actually ignite the whole atmosphere. That is, it would cause a chain reaction of nuclear fusion. However, he and his colleagues’ detailed calculations later showed this is not the case (hallelujah!). The pressure in the atmosphere is just not high enough to maintain a chain reaction. But there are places where extreme physical conditions allow this: deep in the core of stars!

Burn, burn little star

In the 19th century the energy source of stars was not known. One could speculate for example that the Sun’s energy was from burning coal (the most widespread source of energy at the time). On the other hand, the Sun would not exist for more than ~6000 years in that case, while we know the Earth is much much older. Modern physics provided a solution: it is the fusion of hydrogen nuclei that provide the energy! Hans Bethe, who later worked on the Manhattan project alongside Teller, showed the ways stars can fuse hydrogen to helium in their cores.

Hydrogen is abundant in the Universe, our Milky Way has plenty of it in large reservoirs of gas. In these clouds hydrogen is often mixed with dust and other molecules, making them ideal birthplaces for young stars, like in the Rosette Nebula. Young stars start burning hydrogen, they get hot, and make these clouds glow: that is how an emission nebula is born. Curiously, not all emission nebulae are like that.

An Emission Nebula and the Flaming Star

The flaming star nebula shown here is a bit different story. In this case, the central star, AE Aurigae was not born in the nebula that surrounds it today. Instead, it is a so-called runaway star that is speeding through space at abnormally high velocities. On its way, it accidentally came across a large gas reservoir in the Milky Way. Guess what happened next! … No, it did not ignite the nebula, even though in the picture it may seem the whole thing is on fire! Because of the star’s radiation, the electrons in the hydrogen atoms get disturbed. As they relax from this excited state back to normal, in relief they emit light at a very specific frequency. Astronomers know this emission line as Hydrogen alpha (Hα). It appears in the red part of the spectrum, making the whole nebula distinct red.

Shooting the Flaming Star

This was our first chance after long weeks of cloudy nights. As the prediction was clear skies for several hours, we decided to go for a new target to be tracked longer, at high elevation. The Rosette Nebula before was very easy, because it was so bright. Now was the time to select a bit more challenging object. The story of the Flaming Star Nebula intrigued us, therefore we chose that one. We were disappointed first during the imaging session because the details of the nebula were barely seen in individual shots. But when we combined the data and processed the image, the true beauty of the Flaming Star Nebula revealed itself. As if indeed those were flames and red smoke from the star, spiraling upwards! This was a very unique experience for us – hope you like the picture, too!

Higher resolution image

And just a final note: during this imaging session I participated in an online event “Kérdezd meg a csillagászt!” (Ask the astronomer!; the first person shown in the trailer is me). This was organized by the VCSE amateur astronomical society and streamed by Galileowebcast. While we were answering the questions, the telescope -driven by the ASIair unit which I controlled through my mobile phone- was peacefully doing its labor. Cool, isn’t it?

In our coming post, we will trace the Flaming Star back to its origin, so watch this space…

Technical data

AE Aurigae + nebula (IC405), 60x300s
(total 5h; minus 4-5 pics removed because of intermittent clouds)
Hoogeveen, Netherlands
Tue-Wed, 12-13 Jan. 2021
William Optics GT81, f/5.9
Flattener 6AIII 0.8x
ZWO ASI533MC-P, gain 240, -20 deg.
WO Uniguide 50/200 with ASI120MMmini
iOptron CEM40
Optolong L-eXtreme
Bortle~5 (our region; in the town, it should be worse)
New Moon
ASTAP, StarNet++, Photoshop
(Note: ASTAP seems to have an issue with debayering when there is a meridian flip during the observations!)