Skywatchers are crossing their fingers that, early this Tuesday morning, they may witness a brief outburst of a dormant meteor shower that has not been seen in over eight decades.
If astronomers' predictions hold true, the Gamma Delphinids may undergo a rare outburst that could even equal the famed August Perseids—with rates of meteors reaching as high as one or two shooting stars per minute. (Related: "Perseids Quiz: Are You a Meteor Shower Mastermind?")
The Gamma Dephinids were first discovered on the evening of June 10, 1930, when two astronomers from Baltimore, Maryland, noticed that despite the glare of a full moon, a fast and furious flurry of shooting stars was radiating out from a previously unrecorded spot in the sky. Most of the meteors were reported to be as bright as the brightest stars in the sky, making them quite spectacular. (Related: "Perseid Pictures: Meteor Shower Dazzles Every August.")
"Starting at 9:15 p.m. EST, they started seeing meteors pouring out of the small constellation Delphinus (the dolphin). The meteors had short trails and brief duration and were yellowish white," says Peter Jenniskens, co-author of a 2003 study that predicted a new outburst might take place this year.
"In total the observers [in 1930] saw 51 [meteors] in the next half hour and after that, it was all over," says Jenniskens, an astronomer at the SETI Institute and NASA's Ames Research Center in Mountain View, California.
Jenniskens analyzed the path the meteor shower took in 1930 and says we may be in for a return of the Gamma Delphinids. For the sky show to happen, however, Earth must directly cross a debris stream left behind by a mysterious, yet-to-be-discovered comet that passed through the inner solar system sometime in the distant past. (See also "New Comet Discovered—May Become 'One of Brightest in History.'")
"In most other years, that stream of dust of a long-period comet just passes by the Earth's orbit, completely invisible and undetectable," says Jenniskens. "But the point where the trail passes through the orbital plane of Earth [can] move around, and sometimes that trail wanders in Earth's path. This year, it is predicted to do so again."
When is the best time to look up?
The predicted peak time is 8:28 UT (1:28 a.m. PDT, 4:28 a.m. EDT) on the morning of Tuesday, June 11, favoring observers who live in the Americas and the Pacific as far as the Hawaiian Islands. But because that peak time could be somewhat uncertain, Jenniskens suggests that observers should get a head start and begin looking up an hour or two before the predicted peak time.
Where in the sky will the meteors appear?
The shooting stars will appear to radiate out from the namesake constellation, Delphinius, which rises after nightfall in the east for mid-northern latitude observers this time of the year.
By the predawn hour, when the Gamma Delphinids are predicted to peak, observers should face the southern sky where the constellation will be located.
What can meteor watchers expect to see if this outburst occurs?
Meteors will suddenly start to appear out of the constellation of Delphinus, explains Jenniskens, with most being as bright as stars like Polaris, Deneb, and Vega; a few of the meteors will be faint.
The best places to view the outburst are dark locations away from city lights with a clear view of the overhead skies.
"The whole display will last only about half an hour, so key is to be watching at the right time, " adds Jenniskens.
What can science hope to learn from this event?
Jenniskens theorizes that there may be an undiscovered comet that once passed close to Earth's orbit and that we may now be passing through its trail of dust once again.
Astronomers hope to confirm the orbit of that comet and measure the density of dust that it left behind in its trail. That information will give them a better idea of where to look for the parent comet itself and ultimately determine if it is a potentially hazardous object for Earth.
For more sky events check out our weekly skywatching column.