Don't miss the chance to witness tonight's Jupiter-Saturn great conjunction as you may not want to wait until March 15, 2080 to see the giant planets lying right next to each other again.
Mario Raymundo, chief of the PAGASA's Astronomical Observation and Time Service Unit, said this rare astronomical event can be observed after sunset at 5:32 p.m. today (Dec. 21).
Jupiter and Saturn can be viewed standing 20 degrees above the western horizon and best observed between 6 p.m. and 7 p.m., when the two giant planets are "six arc minutes" apart and appear as one bright light in the night sky, Raymundo said.
A conjunction happens when planets appear incredibly close to one another in the sky because they line up with Earth in their respective orbits, he explained.
It is called a "great" conjunction because it is the "rarest and one of the brightest and closest on average of the conjunction between 'naked eye' planets' -- Mercury, Venus, Mars, Jupiter, and Saturn, Raymundo pointed out.
"The last time these two planets appeared so close was on July 16, 1623, when they were only 5 arc minutes apart--that's actually 397 years ago," he said.
Although Jupiter-Saturn conjunctions appear once every 20 years, the next comparably close conjunction would not be until March 15, 2080.
Raymundo said the "rarest" great conjuction will be happening on Dec. 25, 2874 when Jupiter and Saturn will appear just two arc minutes apart.
Moreover, the December 21 great conjuction of Jupiter and Saturn coincidentally happens on the day of the winter solstice, when the Philippines will have the longest night of the year.
Raymundo noted that there is no available data as to the last time the Jupiter-Saturn great conjuction and winter solstice happened simultaneously in the past.
However, he stressed that these events will have no significant effect on the Earth.
Christmas star?
Some have suggested this holiday season that these two planets might be a replica of the legendary star of Bethlehem.
"Actually, one of the more popular theories for the Christmas Star was a series of conjunction between Jupiter and Saturn in 7 BC. For in that year Jupiter and Saturn met not once but three times that year (in May, September, and December)," Raymundo said.
He said there is no scientific data regarding the "Christmas Star" and is still debatable.
"But one thing is certain. If you consider a very close conjunction between Jupiter and Saturn as a 'Christmas Star,' you'll find our two planets will scrunch even closer together on Dec. 25, in the year 2874," he added.
Raymundo said the chances of those in Luzon to view the rare occurrence tonight may be spoiled by the cloudy skies, but those in the Visayas and Mindanao may have a better chance of witnessing the heavenly spectacle.
It may appear as one bright light to the naked eye but will appear to be two planets very near each other through a telescope, he added.
"Those who won't be able to see it tonight can still see it on Dec. 22 but will no longer appear as bright and close during its peak on Dec. 21," Raymundo said.
Filipinos may still observe Jupiter and Saturn adjacent to each other until the end of the month, although the planets will begin to gradually move apart, he pointed out.