Stars over Sisters

Normally these articles are written to highlight interesting facts associated with a constellation of the season that can be viewed from our latitude. This month's edition, however, should generate a heightened level of excitement among the readership because it describes the possibility of seeing a nova. (Nova is Latin for "new star.")

Many astronomers expect a nova will appear in the constellation of Corona Borealis sometime in the next few months. Designated T Coronae Borealis, this object is a recurring nova. It flares in cycles of about 80 years, the last event occurring in 1946.

This time around, scientists say the nova could happen anytime between now and September. T Coronae Borealis normally shines at tenth magnitude, far too dim to see with the naked eye. But when it "goes nova" again, it's predicted to become as bright as Polaris (the North Star) for a few days. To see this event, you need to know where to look.

Corona Borealis (the Northern Crown) is located between the constellations of Boötes to the west and Hercules to the east. The arrangement of its primary stars forms a small half circle, depicting the shape of a crown. Although you can't see it (yet), the recurring nova lies near the eastern edge of the crown. Corona Borealis is near the meridian at about 11 p.m. by mid-June (earlier as the season progresses).

For a nova to appear multiple times at roughly regular intervals, two components of a binary star system must orbit one another at a close distance. Furthermore, the two interacting stars must be a red giant and a white dwarf. The phenomenon occurs when the white dwarf, a hot, dense remnant of a star that has exhausted its nuclear fuel, draws material from its companion red giant.

As this material accumulates on the white dwarf's surface, it eventually triggers a thermonuclear explosion. This process causes the system to dramatically increase in brightness, making it visible even to naked-eye observers on Earth. According to NASA, T Coronae Borealis is one of only 10 recurring novae in our galaxy.

If you do spot the nova, realize that because the star system is approximately 3,000 light-years away, it exploded before the Great Pyramid of Giza was built in Egypt.

According to Greek mythology, Corona Borealis is mostly associated with the crown of Ariadne, daughter of King Minos of Crete. Ariadne fell in love with Theseus who married and later abandoned her on the island of Naxos, after killing the part human, part bull Minotaur beast. When the god Dionysus found Ariadne weeping, the two fell in love and were married. As a wedding gift, Dionysus gave the princess a gem-encrusted crown made by Hephaestus, the god of fire and forge. When Ariadne died, Dionysus flung the crown into the sky, which became the constellation of Corona Borealis.

Summer begins in the Northern Hemisphere on June 20 at 1:51 p.m. At that time, the sun will be directly above the Tropic of Cancer, resulting in the longest interval of daylight in a 24-hour period.

All the planetary action takes place in the morning sky during June. Early in the month, from lowest in the sky to highest, Mercury, Jupiter, Mars, and Saturn form a nearly straight line. Uranus and Neptune are there too, just not bright enough to be seen. As the month progresses, Mercury drops below the horizon. Venus is too close to the sun to be viewed as it transitions from the morning to the evening sky.

This month's dark sky tip: To help limit light pollution, make sure your outdoor lamps emit warm colors and are no brighter than necessary. Limit the use of string lights and turn them off when not needed.