Satellites and climate change threaten the night. This October meteor shower celebrates it.

By Susan D’Agostino | September 30, 2021

Orionid Star Trail Composite. Credit: ikewinski. Accessed via Creative Commons. CC BY 2.0. Orionid Star Trail Composite. Credit: ikewinski. Accessed via Creative Commons. CC BY 2.0.

Astronomy is in crisis. A growing fleet of satellites, discarded rocket parts, and tiny fragments of space garbage, including millions measured in micrometers, are reflecting and scattering sunlight throughout the night sky. This skyglow makes it difficult for astronomers to see celestial objects and phenomenon. The light pollution now exceeds 10 percent of the night sky’s natural-light baseline, which the International Astronomer’s Union long ago set as a red line that should never be crossed.

Meanwhile, telescopes, including the Very Large Telescope at the Paranal Observatory in Chile’s Atacama Desert, are struggling amidst rising temperatures due to human-made climate change. A telescope’s cooling system is designed to keep the instrument cool under a dome during the day. This way, when its dome opens at night, the temperature inside and outside of the dome are the same. Any temperature difference will cause air turbulence that leads to blurry, low-resolution observations. Yet on many days, the target temperature for the Very Large Telescope exceeds the system’s ability to cool it, according to a study published in Nature. The study’s authors advise those who are building the Extremely Large Telescope at the Cerro Armazoes not far away to factor climate change into the new construction.

Light pollution and climate change are bad news for astronomy. Yet late October’s Orionid meteor shower offers an invitation to appreciate the dark.

Very Large Telescope. In mid-August 2010, European Southern Observatory Photo Ambassador Yuri Beletsky snapped this photo at the European Southern Observatory’s Paranal Observatory, Chile. A group of astronomers were observing the centre of the Milky Way using the laser guide star facility at Yepun, one of the four Unit Telescopes of the Very Large Telescope. Accessed via Wikimedia Commons. Credit: European Southern Observatory. CC BY 4.0.
Very Large Telescope. In mid-August 2010, European Southern Observatory Photo Ambassador Yuri Beletsky snapped this photo at the European Southern Observatory’s Paranal Observatory, Chile. A group of astronomers were observing the centre of the Milky Way using the laser guide star facility at Yepun, one of the four Unit Telescopes of the Very Large Telescope. Accessed via Wikimedia Commons. Credit: European Southern Observatory. CC BY 4.0.

If you have time after midnight but before dawn this October 20th or 21st, go outside and find a treeless area away from city lights. With some luck, the night will be cloudless. Look to the sky in the southeast if you are in the Northern Hemisphere or northeast if you are in the Southern Hemisphere. There, you will find an exquisite display of “shooting stars.” These natural fireworks, known as the Orionid meteor shower, offer fleeting evidence that Earth is, at that moment, passing through a stream of cosmic debris in the trail of Halley’s comet.

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Halley’s comet passes Earth only once every 76 years, but the Orionid meteor shower can be seen from Earth every October. In this annual show, dust particles and icy rocks in the comet’s long path collide with Earth’s atmosphere. Friction from the collision heats up the debris into objects known as meteors. These meteors travel at speeds up to 41 miles per second and glow for seconds or minutes—or even burst into a fireball—before burning out. When many meteors appear in the same region of the sky, the event is called a meteor shower. The Orionid meteor shower is active from September 26th through November 22nd, though its peak in late October showcases approximately 15 meteors per hour—or one shooting star every few minutes.

“The Orionid meteor shower is not the strongest, but it is one of the most beautiful showers of the year,” Bill Cooke, the head of NASA’s Meteoroid Environment Office, notes on a NASA website. The shower takes place against a backdrop of some of the brightest stars in the night sky, including Sirius—the brightest star of all.

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The Orionid meteor shower appears to come from its namesake, the constellation Orion. But the constellation neither causes the shower nor frames the event. The brightest lights in the Orionid meteor shower take place just off center from Orion.

As moonlight may wash out the light show, wait to watch until the moon is low in the sky. Plan to look with your naked eye as binoculars and telescopes tend to narrow the field of view. Your eyes may need up to 45 minutes to adjust to the dark, so avoid your smartphone as you wait for the display to start. You will be looking up at the sky for a long time, so consider bringing a blanket to lie down. (Your neck will thank you.) If you plan to take pictures, use a tripod for long exposures that will capture the meteorites’ long tails and a wide-angle lens to appreciate the breadth of the celestial show in your frame.

If you cannot see the Orionid meteor shower due to the short notice or light pollution, you may need to hunt for another shower on a different day in a spot farther afield. (There is some irony here, as Orion was a hunter in Greek mythology.) Check out the International Meteor Organization’s calendar, which promises showers every month of the year. But do not wait too long to pursue your stargazing yearnings. Darkness, like water and air, is a natural resource, and right now, access to that resource is losing ground to space junk, light pollution, and the atmospheric perturbations of climate change.


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