THE STELLAR SYSTEM.

Hawera Star, Volume XLVI, 5 November 1926, Page 2

THE STELLAR SYSTEM.

ADDRESS BY MR P. O’DEA. An address was given to the Hawera Astronomical Society last evening by its patron, Mr P. O’Dea, who took as his subject, “The Stellar System.’ ’ Dr. A. M. Young occupied the chair. There was a good attendance of members, who listened with interest to a brilliant explanation of some of the mysteries of the heavens. The speaker opened his address with a discussion upon the stars as suns. The spectroscope showed them to be constructed of the same elements as our own sun, with temperatures in many cases much higher than that of our own sun, and in some, cases much lower. The temperature of our sun on its surface is calculated to be 5000 C. The temperature at the centre is much higher, being calculated at 7,000,000 C. The same temperature exists at the centres of the other suns also. Stars are at all stages of age and evolution. Our own sun is of the G type, and is on the downward path, having lost its youth. Stars when young are giants, but as they grow old their masses decrease, ana they become dwarfs. Our own sun, is considered a dwarf star. Giants are classified M, lx, G, l l ', A, B, and dwarfs B, A, F, G, lx, M, so that a star starts its life as a giant in the M stage, and ends its life as a dwarf, also in the M stage. The same spectral types exist in the giants as in the dwarfs. After a sun passes the M stage as a dwarf it is considered as becoming a dead dark sun, and astronomers think there are as many dead suns in the universe as there are bright ' ones. This probably accounts for the fact that collisions take place among the heavenly bodies. These collisions no doubt account for the novae, or new stars. Stars in their

early stage are more massive than in their old age, and it appears that in the course of evolution that they lose matter, and give it off as radiation. This leads to the question whether matter can be destroyed. Chemists formerly thought that matter was undestructible, but, the speaker stated, it is now clear that matter is destroyed, and the most noted physicists of to-day, such as Jeans and Edington, consider that the heat we get from our sun is due to the destruction of matter in the sub. Jeans puts it this way: Whereas the burning of one lb of coal, or of any substance, would yield one unit of electricity, the destruction of one lb of coal would yield 15,000,000,000 units of electricity. This does not mean that the universe is getting any smaller, because, although matter is destroyed, it is transferred into energy, and the energy

which is given out by the sun, and other heavenly bodies, must be recondensed in some other corner of the universe. Many of the suns are double or triple bodies. A bright star Algol is eclipsed for two hours every two days. The spectroscope shows that this is due to a dark sun passing in front of the bright sun in our line of sight. \

At the conclusion of Mr O’Dea's remarks a hearty vote of thanks .was passed to him. A prolonged discussion followed in which various theories were explained, and interesting points elucidated. Dr. W. M. Thomson will deliver the next lecture, taking for his subject, “The lee Ages of the World.''