Examples of Protoplanets
Like any scientific theory, it has to be proven. In order to prove the Protoplanet Hypothesis of Solar System formation, astronomers needed to find protoplanets. Have any been spotted? The answer is yes. Three so far in the asteroid belt, and one located outside our Solar System, in the constellation Taurus.
Pallas, is considered to be a protoplanet. It is one of the largest asteroids in the asteroid belt, and orbiting the Sun at a distance between 2.1 and 3.4 Astronomical Units. It also has about 7 percent of the total mass of the entire belt; so for an asteroid/protoplanet it is large. It has diameter between 530–565 km (329 - 351 miles) It was discovered by the German astronomer Heinrich Wilhelm Matthäus Olbers on March 28, 1802
Vesta, is an asteroid/protoplanet. It has a diameter of about 530 km. It comprises about 9% of the mass of the entire asteroid belt, it is the second most massive object in the belt). Vesta was the second asteroid discovered in by Olbers in March 1807.
Ceres has a diameter of about 950 km (590 mi), Ceres is by far the largest and most massive body in the asteroid belt, and contains almost a third (32%) of the belt's total mass. It was discovered in 1801 by Giuseppe Piazzi.
HL Tau B is thought to be a protoplanet and it is not in our Solar System. A team of astronomers located it in the constellation Taurus. A planet is forming in the dust and debris surrounding the star HL Tau. They named the protoplanet, named HL Tau B, and it may be the youngest one discovered so far. The protoplanet was discovered in 2008 by Dr. Jane Greaves of the University of St Andrews and her team and with the support of the British Royal Astronomical Society.
In the computer simulated image to the right, the bright circular spot on the upper right is the protoplanet.
To read about current protoplanet explorations see The Keck Telescopes--Progenitors of the 21st Century Giants