row massive enough to capture hydrogen and helium, the lightest and most abundant elements.[ Ann Zabludoff (University of Arizona) (Spring 2003). "Lecture 13: The Nebular Theory of the origin of the Solar System". Retrieved 2006-12-27.] Planetesimals beyond the frost line accumulated up to four Earth masses within about 3 million years. Today, the four gas giants comprise just under 99% of all the mass orbiting the Sun. Theorists believe it is no accident that Jupiter lies just beyond the frost line. Because the frost line accumulated large amounts of water via evaporation from infalling icy material, it created a region of lower pressure that increased the speed of orbiting dust particles and halted their motion toward the Sun. In effect, the frost line acted as a barrier that caused material to accumulate rapidly at ~5 AU from the Sun. This excess material coalesced into a large embryo of about 10 Earth masses, which then began to grow rapidly by swallowing hydrogen from the surrounding disc, reaching 150 Earth masses in only another 1000 years and finally topping out at 318 Earth masses. Saturn may owe its substantially lower mass simply to having formed a few million years after Jupiter, when there was less gas available to consume. T Tauri stars like the young Sun have far stronger stellar winds than more stable, older stars. Uranus and Neptune are thought to have formed after Jupiter and Saturn did, when the strong solar wind had blown away much of the disc material. As a result, the planets accumulated little hydrogen and helium—not more than 1 Earth mass each. Uranus and Neptune are sometimes referred to as failed cores.[ E. W. Thommes, M. J. Duncan, H. F. Levison (2002). "The Formation of Uranus and Neptune among Jupiter and Saturn". Astronomical Journal 123 (5): 2862.] The main problem with formation theories for these planets is the timescale of their formation. At the current locations it would have taken a hundred million years for their cores to accr
