Discovery of Giant Bubble Nebula in Monoceros Constellation

Updated: Jul 16

"PaRasMoMi-1" Or, the"Bubblegum Nebula", is a new 'OIII' dominated Planetary Nebula candidate discovered by a group of amateur astronomers in April 2021.

The initials stand for: "Dana Patchick --Sakib Rasool--Sankalp Mohan--Utkarsh Mishra(Author)".

PaRasMoMi-1 lies in the constellation Monoceros and is 5942 ly (light-years) away from earth.

It is near the Rosette nebula/NGC 2237 and is officially designated at Hong Kong/AAO/Strasbourg H-alpha planetary nebula database. Comprehensive database of all known planetary nebulae.

Our potential planetary nebula candidate was discovered via examining amateur astrophotographs which revealed a shell structure in the extreme corner of the image.

PaRasMoMi-1 object details:

PN-G: 206.2+00.6

Coordinates: 06:41:30.00 +06:16:30.00

Size: 26 arcmins (Almost apparent size of the moon) Check out Patrick's wonderful version here Follow my instagram for more :@mr_deepsky

Read: how we discovered a potential planetary nebula through DSS

While examining the Monoceros region, we found a spot that showed a bluish shell of really big angular size. Later we searched this area using the HASH database & The Strasbourg astronomical Data Center (CDS ) but found nothing. This meant that the object was unknown and to be 100% sure we tried searching for any scientific research paper on arXiv and other places. We did not get any results except the E-BOSS paper which showed only the bow shock region and nothing regarding this OIII bubble. So, we continued our research on the object. Our main goal was to find a star candidate which was powering the structure. We tried looking for a hot white dwarf star and we found several candidates.

  1. Gaia DR2 3132665033065333120: Temperature 5994.96K is too low to create such a structure in space.

  2. Gaia DR2 3133423455568056960: Too far from the center, no temperature measurement available.

So these two were the White dwarf's we located and none of them gave us the confidence to select it as a CSPN candidate. So, we got into a serious discussion regarding this, and Dana Patchick suggested that HD 48099 could be our CSPN as it is very hot and is capable of producing such a structure. The spectral class of HD 48099 is O5V((f))z+O9:V.

An O-type star is a hot, blue-white star of spectral type O in the Yerkes classification system employed by astronomers. They have temperatures in excess of 30,000 kelvin (K). Stars of this type have strong absorption lines of ionized helium, strong lines of other ionized elements, and hydrogen and neutral helium lines weaker than spectral type B.

Stars of this type are very rare, but because they are very bright, they can be seen at great distances and four of the 90 brightest stars, as seen from Earth, are O type. Due to their high mass, O-type stars end their lives rather quickly in violent supernova explosions, resulting in black holes or neutron stars. Most of these stars are young massive main sequence, giant, or supergiant stars, but the central stars of planetary nebulae, old low-mass stars near the end of their lives, also usually have O spectra.

HD 48099 was our perfect candidate for the particular moment as it carried the majority of the properties that we need and when we checked the 12um and 22um plates it became clearer that 48099 was the star behind the structure.

Then we decided to photograph our new discovery, so we contacted Patrick Dufour and he it imaged for around 20hrs from his remote observatory in Chile. He used a 12" AG Optical RC Telescope and QHY 600 Mono CMOS camera with SHOLRGB filter to capture the region. Since the object was only visible in OIII we asked him to capture as much OIII as possible and Patrick did a great job by collecting the data quickly - as the object was close to the horizon.

Patrick supplied us with the data and I started examining it and created a few Continuum free images of OIII and H-alpha to really bring out the structure details.

OIII before vs after

Making a continuum-free image gave me an idea of how to work on this subject and it also revealed the structures that needed to be pulled out during processing. Now, if you examine the H-alpha continuum free image you would not find this bubble structure there.

When I subtracted the narrowband with broadband I got these results and the idea about how to work on this object during the processing. It is the most difficult object I’ve worked on by far, and it took me over 23 days to process completely. Usually, it only takes 1hr -2hrs to process an image.

Friendly Challenge: Whoever photographs this object and does a better job than ours will get a dedicated page on my website

Nature of this PaRasMoMi-1

Now the question is; What is this object? Note that our main goal here is to find hidden planetary nebulae. This could be one of them - but there are many mimics or maybe even more strange objects like PaRasMoMi-1. By studying the properties of the object we can understand what this object could be. To be honest, right now, we can only guess about this object as it has some properties of planetary nebula and shows properties of a Stromgren sphere. Speaking in theoretical physics terms - there can be a sphere of hydrogen (HII) around young stars of spectral class O or B. In short - it means that usually spectral class O or B stars are responsible for such structures. They are by nature on the hot side - around 30,000K+ and they emit very strong energetic UV radiation. If we check the Galex NUV survey we can see how strong the star shines there.

Galex Near UV

As can be seen in the above picture –this is how our bright candidate star appears on a GALEX Near UV survey plate of the region. It shows an optimum amount of output, and that this star is well capable of creating the structure.

  • The hotter and more luminous the exciting star, the larger the Stromgren sphere.

  • The denser the surrounding hydrogen gas the smaller the Stromgren sphere is.

It would be interesting to know the rate of expansion of this nebula. What are the other examples of this type of region?

The Rosette Nebula (Sharpless 275) is a bright HII region with a ring-like appearance and the similarity here is that both lie in the same Monoceros region. The Rosette nebula's primary source of ionization is the O5 star 'HD 46223' and the O6 star 'HD46150'. So maybe this nebula could be some rare type of Stromgren sphere which is OIII dominant. Of course, these are just theories derived during our discussion with each other and to make things clear we need a spectrum of this nebula.

Dr. Quentin Andrew Parker has given it an official designation and has added it to his list. Maybe soon we’ll get to know what this object is. There could be another theory regarding this object. One day Marcel Drechsler and I had a chat regarding this object and he gave a really nice theory that has promise to it. 'HD 48099' re-ionizes atomic oxygen gas from the Monoceros SuperNova-Remnant and causes the bubble to form. The star 'HD 48099' is a spectral class O which is kind of good for creating a Stromgren sphere. Oxygen gas (created by the supernova remnant) is ionized by the big hot star. The big star might be moving fast through the interstellar medium (oxygen) and forming this bubble and the bow shock. The arc shock is only visible with OIII because there are no large amounts of molecular hydrogen in the immediate vicinity of 'HD 48099' that could be Ionized. HD 48099 is an O-type star with a surface temperature of 41000 K. The star produces extreme UV radiation that is very capable of producing this arc that is well visible on WISE. The distance of 'HD 48099' and that of the Monoceros SNR coincide so that ionization of the oxygen shell of the SNR is likely.

Credit : Marcel Drechsler

The white lines are the solar wind of the hot star, which is compressed and heated by the interstellar medium of the Monoceros Loop. Everything in the background is OIII from Monoceros, there is simply not enough HII in this region to also form an HII arc. OIII, on the other hand, is plentiful

Akari Survey showing immense UV radiation

Here you can see the star's immense UV radiation, which is concentrated in the direction of the arc. These kinds of bubbles are extremely rare. If only because such dense OIII areas are very rare. Around Wolf Rayet stars, however, such bubbles are common. I presented all these scenarios to our Teammates Dana, Sankalp, and Sakib and we somewhat agree upon that it could be a type of ionized bubble/Stromgren sphere and that we need experienced astronomers to study this object in detail.

Planetary Nebula

PaRasMoMi-1 could be a very old and evolved planetary nebula - as it does have some properties of PNe. There is also a White dwarf near the center and another W.D. further off-center that are contenders, but the temperatures required are not sufficient. On occasion, the temperature of a cspn (central star of the planetary nebula) is indeed misleading, or simply wrong. This can have several causes, e.g. cosmic gas scattering blue components of the star's light. Then even Gaia has no chance of determining the correct temperature. Even with multiple star systems, where one part is a WD, the temperature reading is almost always wrong. On the plus side - it is also nicely visible on the 12um WISE plate, where a majority of PN shines nicely. Even Dr. Quentin Parker said that this object does have some properties of PN

Wide Field Image of PaRasMoMi-1

Before publishing our discovery I made an Instagram story regarding collaborating on a confidential project and a few of them including Jasa Rebula showed interest, I briefed them about our newly discovered nebula and told them that I would like some skilled amateurs to photograph it, but unfortunately, the Monoceros region was not visible in the northern hemisphere. I was pushed to withdraw this proposal but after few weeks Jasa approached me on my Instagram and send me really nice Wide field image of PaRasMoMi-1. Rune matthijssens shot this using Takahashi FSQ-106ED, 16803 CCD hosted by telescope live and Jasa rebula skillfully processed the data using Pixinsight, total imaging was time: 6 hours 10 min. I really appreciate their e