Eager sky watchers are turning to the heavens as Comet NEOWISE, one of the brightest comets in a generation, starts climbing ever higher among the evening stars.
A majority of comets fly through the solar system invisible to humans, usually too small and dim to be seen with the naked eye. The last frozen ice ball that gave us a big show was Hale-Bopp, a comet that was visible for nearly 18 months around its closest approach to Earth in 1997.
Officially designated C/2020 F3, Comet NEOWISE was discovered on March 27 and had until this week been visible only to committed comet viewers willing to wake up in the early pre-dawn hours. But on Monday, NEOWISE tipped into the post-sunset sky and has even been spotted by people living near city centers with all the light pollution.
“It’s the first time in 23 years that this is possible,” said Federica Spoto, an astronomer at the Harvard & Smithsonian Center for Astrophysics. “You can watch it from your backyard and you don’t need a telescope.”
To catch NEOWISE yourself, look up at the northwest skies about an hour and a half after sunset. Experts suggest going to the darkest area you can for best viewing. Find the Big Dipper and follow its ladle as it arcs in the direction of the horizon.
NEOWISE will appear under the Big Dipper about 10 degrees above the horizon and be about as bright as that constellation’s stars. If you hold out your arm, 10 degrees is roughly the part of the sky covered by your fist. Over the next few days, NEOWISE will move higher in the sky and be easier to spot, reaching its apex on July 23, when it makes its closest approach to Earth.
Good binoculars will allow you to see more of the comet and its spectacular dust tail. Lucky viewers might even catch the fainter blue ion tail, made from charged particles flying off the comet’s icy nucleus. NEOWISE is visible only to observers in the Northern Hemisphere and should remain bright enough to spot into mid-August.
For those looking to capture a souvenir of their experience, a digital camera placed on a tripod and set to a five- or 10-second exposure could do the trick, said Ernesto Guido, an amateur astronomer in Italy. Many cellphones allow users to change the settings on their cameras and achieve surprisingly good results. Try framing NEOWISE against a nice background such as a tree, Mr. Guido suggested.
A ball of ice that beat the odds
Comet NEOWISE gets its name from NASA’s Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE), a space-based infrared telescope dedicated to looking out for potentially hazardous asteroids and comets. Researchers who manage the observatory spotted the comet in March when it was headed in the direction of the sun.
Comet NEOWISE made its closest approach to our star on July 3, coming within the orbit of Mercury.
“A smaller or weaker comet would have crumbled under the pressure,” said Amy Mainzer, principal investigator of the NEOWISE mission.
That’s exactly what happened earlier this year to Comet SWAN, which was just barely visible to naked-eye viewers in the Southern Hemisphere, before fizzling as it rounded the sun. Another comet, ATLAS, disintegrated into more than two dozen pieces in April.
NEOWISE comes to us from the distant outer reaches of the solar system, having spent most of its life in a frigid field of icy bodies called the Oort cloud. When far from the sun, comets are inert and lack their beautiful dust tails, which can be 10 million miles long. The sun’s heat causes them to expel gas and dust, forming an atmospheric shell called a coma and then the pressure of solar radiation extends this structure out into a long tail.
Comets like NEOWISE are leftovers from our solar system’s creation. Since they retain the building blocks of planets in their frozen ice, they can provide scientists with important information about our origins. Dr. Mainzer likened its approach to a mission that collects samples and returns them to Earth, except “the sample comes to us.”
NEOWISE won’t make it back to the inner solar system for 6,800 years. So enjoy it while you can.
“Things are really tough right now for lots of people,” Dr. Mainzer said. “But this is a chance to look up and reconnect with the big picture stuff.”