Star Nucleation Amped Up by Tidal Effects

Star Nucleation Amped Up by Tidal Effects

Spiral galaxies can vary widely in the amount of stars they are generating. It is asserted that star nucleation, via the imposition of high pressure over small volumes of molecular cloud, is the rate determining step. Turbulence of molecular clouds in galaxies is greatly increased when the chaotic, but stable, spiral galactic structure is disturbed by tidal effects of nearby galaxies. In this posting, the three main galaxies of the Leo triplet are used to illustrate and link the chain of events from tidal influence to rapid star production in the galaxies we image.

Fueling up a New Star – Gravity vs Angular Momentum

Fueling up a New Star – Gravity vs Angular Momentum

In order to grow, a nucleated (condensed), cold star core must accumulate hydrogen as future mass and fuel before igniting to fusion and becoming a full fledged shining star. But there is a problem in the way. Just as the sun cannot accumulate planets via gravity, without some mechanism to shed angular momentum, hydrogen will just orbit the baby star and not accumulate upon it. Viscous drag both dissipates angular momentum and allows hydrogen molecules to accumulate by spiraling down to the star. Unlike a planetary orbit, in a spiral gravity, angular momentum, and viscous drag (friction) are not orthogonal to one another, allowing friction to dissipate momentum as the gravitational fall increases it. Upon arrival at the star, there remains a lot of angular momentum that still need dissipating. Compressed, hot hydrogen forms a metallic core on the star where it creates an electromagnetic magneto – a sort of electric motor. The magneto converts angular momentum into linear momentum that squirts out as jets from the poles. Both mechanisms allow hydrogen to accumulate without spinning the young protostar to death. The jets also advertise to us that star formation is going on and results in beautiful images.

The Hidden Galaxy – Now you see it

The Hidden Galaxy – Now you see it

IC342/Caldwell 5 – The Hidden Galaxy in LHaRGB Planewave CDK 12.5in; AP 1100GTO AE; QHY600M, – Baader Cmos Opt Broadband and 6.5nm Ha FiltersL: (50 x 180s, Bin 1, Gain 100); H: (29 x 720s Bin 1, Gain 100); R,G,B: (25,23,22 x 210s, Bin 1, Gain 100)Total integration time = 12.4 hrs (Feb 10-12, 2025) Maple Bay, BC, Canada For full resolution, downloadable image, visit my gallery at Victoria RASC Zenfolio or Astobin The Hidden Galaxy gets its name from its position in the sky, near the Milky Way and partly obscured by our galaxy’s dust.   If not for the dust, IC342 would be visible with the naked eye and occupy about the same size as the moon. In reality

Its Supersonic! – But it’s complicated

Its Supersonic! – But it’s complicated

The massive explosion of a supernova sends material (and light) outwards in all direction, at velocities greater than the speed of sound. The speed of sound is another way of saying the speed that pressure or density waves can travel or disperse through the medium that it is moving through. The particles ejected by the supernova are moving so fast and so much momentum that they don’t disperse but act like a moving wall of material, bulldozing and sweeping up any additional material in its path. Along the way, the particles that make up this moving wall, or shock front involves a lot of friction between particles so that it heats up to extreme temperature (million of degrees) and the wall emits light that we see as the remnants or remains of a supernova.
This wall, known as a shock-front, eventually runs out of momentum due to is expanding spherical geometry and sharing of momentum, but remains visible to our cameras long afterwards, until it fades through cooling. The patterns of emitted light are both beautiful and distinctive from other subsonic flow patterns, and these patterns enable us to identify these objects as supernova remnants. or leftovers from the supernova explosion.

More than Dust in the Wind

More than Dust in the Wind

There is no deny that the dark nebula, LDN 534, makes an interesting target for astrophotography. It has all the earmarks of sky clouds being transformed by the wind. In fact it is likely a section of molecular cloud ripped out of the spiral arms, and being eroded by the winds of ISM. Unlike star fields that appear like foggy light that gets more disperse as concentration drops, the eroded molecular cloud seems to be much more wispy and reluctant to yield its integrity. Undoubtedly the hydrogen molecules do yield to the wind, disassociating to become atoms while the dust gets dispersed. We are lucky in this one, as a few stars make some nice blue reflections. In other cases, the eroded molecular cloud forms very coincidental shapes – included some naturally streamlined ones.

A Rotting Fish tells no tails

A Rotting Fish tells no tails

In this website’s second look at the Rotten Fish dark nebula, I wanted to bring home the concenpts involved in star nucleation. In case you were wondering, the answer is yes, star formation can happen in clouds not emitting Halpha light, even though we can certainly assiciate Haspha with star cluster / stellar nurseries. The answer lies in the mechanism of pressure buildup at points allowing diatomic molecular hydrogen and dust to nucleate a star. In both cases, dust provides the necessary cold temperature in addition to critical point temperature suppression. However, in the case of a dark cloud, the pressures required to nucleation is based on cloud turbulence alone, while stellar nursery clouds are aided in pressure build-up by stellar winds. It seems from images, that star formation in clouds is much more sporadic, while star clusters are more likely to be formed in stellar nurseries shining in Halpha light.