Z Canis Majoris
Young Stellar Object in Canis Major
RA: 07 03 43
Dec: -11 33 06
Mag: Variable, 11th mag to ~7th mag
It looks like I'm alternating between ring galaxies and young stellar objects this year. I didn't have a lot of time to research this object, so I apologize if I omitted some interesting information. This is indeed a fascinating object with gazillions of research articles on it.
As we know well, young stars do strange things. We already met with a FUor, or an "FU Orionis" type star in a previous post on Parsamian 21. A FUor is a pre—main sequence star (which means it isn't still fusing hydrogen) which shows extreme variability in its brightness. The drastic variation in brightness is believed to come from variations of the rate of accretion of material onto the young formative star from a highly luminous accretion disk which surrounds it. Indeed, the luminosity of Z CMa is about 3500 times that of the sun! [1]. Z CMa is about 3750ly away.
ZCMa_LightCurve.png
Light Curve of Z CMa from [7]
For a while, Z Canis Majoris was thought to be a FUor, because it's optical spectrum is characteristic of one, but it was discovered through speckle imaging in 1991 [2] that there is an infrared companion to this FUor, now believed to be a Herbig Be star. A Herbig Ae/Be star is a high mass (2—8 solar mass) pre—main sequence star with an A or B spectral type.
ZCMa_POSSIIBlue.png
DSS2 Blue Image of Z CMa
It appears that this is a subject of many infrared and radio studies, but there is not much in the way of optical imagery beyond the DSS and the long bipolar outflow identified in [1], a reference that Steve Gottlieb kindly shared with me. Perhaps this is only natural given that a lot of the action is enshrouded inside clouds. It is now understood that both stars drive jets, and the long jet identified in [1] is associated with the Herbig Be star [7].
ZCMa_Schematic.png
Schematic of Z CMa from [7]
In radio and infrared, the jets from both stars have been well-studied, and there are beautiful images:
ZCMa_IR.png
Infrared image of Z CMa from [3]
ZCMa_Radio.png
Radio image of Z CMa from ALMA / VLA [4]
Any optical images I could find [5] focused on the region of about 1"—2", which seems to be the scale on which the two stars and their bipolar outflows can be resolved.
However, none of these jets line up with the "jet" that is seen in the optical POSSI or PanSTARRS-1 images, which lies within the purview of our visual observations, and is on a scale of tens of arcseconds at best. Whereas Steve and I were not aware of any references that discuss this jet, it may perhaps simply be a reflection nebulosity around the stars. Its strange shape makes me wonder if perhaps some of the dust was cleaned out into this formation by the jets which run NE-SW as per [1] (just like the model for Parsamian 21 featured in the previous OOTW), but I'm no astrophysicist.
There is more to this extensively studied object: Radio observations [4] indicate that the disk around these stars has been disturbed, perhaps by a passer-by.
It's interesting to note that Z CMa is a member of the "CMa R1" stellar association, a group of younger stars associated with the highly photographed Seagull Nebula (IC 2177), speculated to be a region of star formation triggered by a supernova explosion front [6].
In any case, coming to visual observation, I perhaps had the good fortune of catching it when it was bright. On a night of subpar transparency at Pinnacles National Park in February 2022, I decided to find a few high surface brightness targets from my observing list and this one landed in it maybe from Steve's March 2012 Sky & Telescope article. Through my 18" at 200x (2.22mm Exit Pupil) with averted vision, I was able to see a clear streak of nebulosity "jutting out" from the star. I wrote "looks like a comet tail". Racking on more power (340x, 1.3mm EP), I noticed that the ray of nebulosity seemed slightly offset from the star in the northern direction.
If anyone knows what this ray of nebulosity spanning several arcminutes is all about, I would love to learn.
As always,
GIVE IT A GO AND LET US KNOW
[1] Z CMa: A large-scale high velocity bipolar outflow traced by Herbig-Haro objects and a jet
[2] An infrared companion to Z Canis Majoris
[3] The inner environment of Z CMa: High-Contrast Imaging Polarimetry with NaCo
[4] Snapshot: Astronomers catch a stellar drive-by
[5] Sub-0.1?? optical imaging of the Z CMa jets with SPHERE/ZIMPOL
[6] CMa OB1 (+ CMa R1) (use Google Translate for English)
[7] Constraining the circumbinary envelope of Z Canis Majoris via imaging polarimetry
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Originally Posted by wvreeven
