This drawing shows how forming planets drew gas to themselves.
Click on image for full size
Image from: The New Solar System
How a proto-planet sweeps up nearby material
As shown in this picture, while they were forming in the solar nebula, the nuclei of the protoplanets drew material to themselves from the cloud of gas and dust around them. The bigger a protoplanets was the more gaseous material it was able to attract to itself.
Big protoplanets such as Neptune were positioned far out from the protosun in the primordial nebula where the concentration of gas was quite low. Therefore Neptune was not able to sweep up as much gas as other gas giants like Jupiter and Saturn.
Shop Windows to the Universe Science Store!
Our online store
on science education, classroom activities in The Earth Scientist
specimens, and educational games
You might also be interested in:
The solar system contracted, or shrank together, out of a spinning cloud of hydrogen and helium gas. This spinning cloud had a certain amount of momentum, which caused it to flatten, somewhat the way a...more
This image shows the new Great Dark Spot of Neptune, which was discovered using the Hubble Space Telescope. The image shown here, shows a "hole" in the clouds of Neptune in pink, in the northern hemisphere,...more
Atmospheres of the giant planets have definitely evolved from their formation out of the primitive solar nebula. How much they have evolved remains to be seen, however. Because of their enormous gravity,...more
This image shows some cirrus clouds, extending for many kilometers across the disc of Neptune. These clouds are somewhat high up, for they can be seen to cast shadows on the lower clouddeck, which is 35...more
This image of Neptune uses false colors to bring out the hazes of smog, which can be seen in red along the limb of Neptune, at the edge of the picture. These hazes of smog are found at very high altitudes,...more
Like Jupiter and all the giant planets, Neptune's appearance shows a striped pattern of clouds. Other cloud shapes seen over time include a small dark spot, the "scooter" and the Great Dark Spot. The Great...more
If you had a quiz question in school that asked what year Neptune was discovered, you'd probably choose 1846. But Neptune wasn't discovered the way all the other planets in our solar system were. Astronomers...more
In astronomy, it is a usual procedure to calculate the luminosity of a star, and this calculation indicates the energy and the temperature of the star. When the luminosity of the outer planets was calculated,...more