Since there is no nuclear reaction inside the protostar , a protostar is not a star yet 由于在原恒星的核心尚未发生核聚变，它们仍不能称为真正的恒星。
With an infrared telescope , we can peek through the cooler dust in the elephant trunk nebula to reveal the luminous proto stars behind 利用红外线拍摄的象鼻星云，可以穿透前面的尘埃，看到背后发光的原恒星。
If the protostar is slightly more massive than a planet , but not massive enough to burn its nuclear fuels , it becomes a 如果一颗原恒星的质量只是比行星大少许，它的中心便不能产生热聚变，成为一颗昏暗而难以被发现的
Most of the energy generated in the protostar stage comes from the gravitational energy of the cloud , just like a ball will drop with increasing speed from your hand if you release it 在原恒星阶段，星体的能量主要来自星际云引力塌缩时所释放的位能，犹如树上的苹果会向下掉一样。
The luminosity per surface area will increase because the temperature increases . but if a star is not very massive , its luminosity will drop because the size of the star protostar decreases much faster 每单位面积的光度会随著恒星的温度增加而上升，但假若恒星原恒星质量不足，它的光度会由于星体体积下降过速而不升反减。
Which is very dim and hence very difficult to find . if it is massive enough though model dependent , the lower mass limit is about 0 . 1 solar mass , the gas in the protostar continues to heat up until the central portion becomes hot and dense enough for , say , the hydrogen nuclei to overcome their mutual electrical repulsion . nuclear fusion will then take place and a star is finally born 如果原行星质量足够大下限约为0 . 1个太阳质量，要注意的是，不同的理论模型会给出不同的下限，原恒星会不断变热，直至核心部分足够热和高压，令氢原子核克服质子间的电排斥力，产生核聚变，成为一颗真正的恒星。
