Ever wonder what makes the sun so hot and bright, or if it will ever burn out? In the past, some believed that the sun was a ball of hot metal, a gigantic chunk of burning coal, or that it was heated by gravitational contraction as it shrunk.

No one, however, could account for the tremendous amount of energy being released. The energy of the sun stems from a reaction called nuclear fusion in which four hydrogen atoms fuse together to form helium. The sun is roughly 73 percent hydrogen, nearly 25 percent helium, and a small fraction of a few other elements such as carbon. When hydrogen forms helium, a tiny amount of mass is lost and is converted to energy. Every second the sun converts 564 million tons of hydrogen to 560 million tons of helium while 4 million tons of mass is lost to energy formation. When the amount of matter lost is inserted into Einstein’s famous equation E=mc2. An unbelievable amount of energy is released. The amount of solar energy that reaches Earth is less than one-billionth of the sun’s output. Even though the sun is losing mass at a rate of 4 million tons per second, it is so massive that there is no danger of its burning out anytime soon. The sun is estimated to be 5 billion years old and will last at least that long again before it enters its death throes.

Focus on the planets

Mercury opens the month low on the west-northwest horizon about 9 p.m. It ascends gradually each night so that, by June 17, it is well up on the horizon with Castor and Pollux to the upper right and the closely paired duo of Mars and Saturn to the upper left.

Venus is brilliant on the east-northeast horizon during the pre-dawn hours throughout June. The Pleiades star cluster lies to the upper left of Venus.

Mars spends the first half of the month pursuing Saturn on the west-northwest horizon, catches up with the ringed planet for their closest conjunction since 1978 and pulls ahead for the remainder of the month. If you only look at the skies once this month, check out the extremely close pairing of Mars and Saturn well up on the northwest horizon about an hour after sunset on June 17.

Saturn is the pursued rather than the pursuer with Mars during the month as you view both together on the west-northwest horizon during the early evening hours.

Jupiter looms large and bright in the southeast at nightfall. Jupiter is starting to dim but is still rich in telescopic detail such as the dancing movements of its four major moons.

Uranus and Neptune are in the constellations of Aquarius and Capricornus respectively low in the east. Uranus is the best bet for planet watchers as the moon comes within 2 degrees the morning of June 17. Binoculars and a finder’s chart (see Sky & Telescope May 2006, page 66) will help locate these dim and distant planets for more experienced viewers.

June events.

1 Sunrise, 4:53 a.m.; sunset, 8:14 p.m.

3 Moon in first quarter, 7:06 p.m.

4 Moon at apogee, or farthest distance from Earth, today.

10 The orange star just to the upper right of the moon is Antares.

11 Full moon, 2:04 p.m. The full moon of June is called the Hay Moon, Rose Moon, Strawberry Moon or Honey Moon.

16 Moon at perigee, or closest approach to the Earth, today.

17 Look to the northwest an hour after sunset for the closest pairing of Mars and Saturn in 28 years. at to the lower right is Mercury.

18 Moon in last quarter, 10:08 a.m.

21 Summer solstice, 8:30 a.m. This is the when the sun is farthest north for the year and begins its descent back toward the equator. The sun enters the astrological sign of Cancer at the solstice but astronomically is just entering Gemini.

23 St. John’s Eve when midsummer was celebrated in England with great bonfires across the land. The moon, Venus, and the Pleiades form a triangle on the northeastern horizon during the pre-dawn hours.

25 New moon, 12:06 a.m.

29 Starting well up on the northwest horizon, the faint star to the immediate left of the moon is Regulus about 45 minutes after sunset. To their lower right in a descending diagonal line is Mars, Saturn and Mercury in that order.

30 Sunrise, 4:52 a.m.; sunset, 8:25 p.m. On this date in 1908, a comet or asteroid exploded above Tunguska, Siberia, with a force so great that it leveled trees outward over an area the size of Rhode Island.

Clair Wood taught physics and chemistry for more than a decade at Eastern Maine Technical College in Bangor. Send astronomical queries to him at cgmewood@aol.com or care of the Bangor Daily News, Style Desk, P.O. Box 1329, Bangor 04402.