Protostar
The following citations listed in this article are from What is a Protostar? - Universe Guide, What is nuclear fusion | IAEA, The Life Cycle Of A Low Mass Star - BosCoin, and Astronomers Detect Spiral-Arm Structures around High-Mass Protostar | Sci.News.
As noted in the previous entry, the first phase any star goes through is the Pre-star, or Protostar phase. According to previously cited sources, Protostars are "the pre-Main Sequence [phases] of a star [in] which it is accumulating its mass and not yet fusing hydrogen into helium." Comparing a star's lifetime to a human being's, think of this phase as the time a being spends as a fetus.
See, before a star becomes, well, a star, it's just a cloud of gas and dust. Eventually, this cloud will "collapse" on itself after an impactful event; a neighboring or passing star will most likely be responsible for this event. When this happens, said cloud will begin its first official phase: the Protostar phase. A Protostar isn't necessarily an actual star, but it's not a cloud anymore either. This phase can last anywhere from 100,000 to over 10 million years, depending on the star's mass: "the higher the mass, the quicker the time, the less mass, the longer the time."
A star's entire life goal is to achieve nuclear fusion. According to previously cited sources, nuclear fusion is "the process by which two light atomic nuclei combine to form a single heavier one while releasing massive amounts of energy." A Protostar's job is to transfer hydrogen into helium. It does this because its mass isn't plentiful enough to generate the fusion. Rather than nuclear fusion, a Protostar's heat emission relies solely on its gas, which collapses on itself over and over again to create a sustainable amount of energy.
Protostars aren't developed enough to be seen by the human eye without a telescope. Their lights are dim, and the gas and dust surrounding them obscure one's vision even more. All stars have their own magnetic field. During the Protostar phase, one's magnetic field can grow and develop a lot. Eventually, the star's magnetic field will become so strong that it will be able to generate solar winds, which will clear the debris around it and make it easier to see.
According to previously cited sources, Protostars are believed to have "accretion disks," which are basically disks made up of space matter that are gravitationally attracted to said star. One can easily compare these disks to a weak black hole: they suck everything towards the star to help it increase its mass, but in a less destructive and brutally terrifying way. When the Protostar phase of a star's lifetime is over, the star will shed these disks and move onto the main sequence phase.
High-mass Protostars acquire a good amount of their mass from their accretion disks. There isn't a lot of information on this topic, since they are very difficult to study, however, scientists were able to study a high-mass Protostar in 2020, which they named G358. 93-0.03-MM1 (See image below). As you can probably see, this star is made up of mainly warmer colors, but high-mass stars are actually blue. This is because they are insufferably hot. This specific star's accretion disks are very easy to see, and they seem to wrap their arms around the nucleus of the star. Personally, it reminds me of a spiral galaxy's structure!
A low-mass Protostar's fuel tends to run out quickly. They usually appear redder, due to their lower temperatures. They also tend to be smaller than high-mass stars. As you look at the image below, notice the pale blue fog that surrounds the nucleus. Those are called jets. Think of it like water shooting out of a hose. The jets propel matter and space debris from out of the Protostar to help get rid of anything holding said star back from entering its main sequence.
High-mass Protostars and low-mass Protostars differ from each other in some ways, but overall, they are actually very similar. Remember to think of the Protostar phase as the fetal stage of a star!
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