“What was that bright light in the sky last night?” is a popular question NASA hears from the public and media, and one that the Meteoroid Environment Office (MEO), along with its All Sky Fireball Network, does its best to answer, in detail.
A fireball is a meteor brighter than the planet Venus, and in the first quarter of fiscal year 2017 (October-December 2016) a special team within MEO analyzed 16 bright fireball events. The team — formed in 2014 and made up of Rhiannon Blaauw, Steven Ehlert, Aaron Kingery and Danielle Moser (all Jacobs ESSSA Group/Marshall Space Flight Center) — analyzes these fireballs and shares the findings to keep the government and the public informed.
“When a rock hits the atmosphere, its light spreads out substantially so a piece of debris even a couple centimeters across is very bright to an observer on the ground,” explained Blaauw.
“The public is concerned about [bright fireballs],” continued Ehlert. “Every single one of these [16 events] involves a TV station inquiring to NASA Headquarters about something they saw in the sky the previous evening.”
Although the public has always been curious after spotting something in the night sky, MEO saw a spike in interest after the Chelyabinsk fireball over Russia in February 2013 made the news. In fact, the interest is so high that NASA policy now requires that the team update the government and public on circumstances surrounding events and, assuming the sighting was a fireball, characterize it. When a request comes in, the team spends a number of hours gathering as much information as possible. Members take advantage of data from the NASA All Sky Fireball Network, a network of 14 cameras in the United States set up by MEO to record fireballs, and also utilize eyewitness reports. They pull in data from publically available cameras located across the country as well. One of the biggest assets for gathering information and witness reports is social media.
“What always struck me was you’d be surprised how many videos surface of events,” said Kingery.
Rather than sift through social media post after post, Kingery developed a tool that looks at Twitter for tweets on the event. The team is looking to determine
- Where the event took place
- What direction the meteor was heading
- If the meteor was large enough to produce meteorites
- The orbit it followed in the solar system before it hit the atmosphere
To help answer some of these questions, Moser developed a tool that calculates the fireball’s trajectory based on eyewitness reports. Most of the sightings reaching the MEO are from heavily populated areas, such as the Northeast, specifically New York and Boston areas, as well as Los Angeles and southern California. To date, the team notes fireballs observed from the Washington Monument and the Statue of Liberty as some of the more unique sightings. However, the report pattern doesn’t mean that those are the only places fireballs are seen, but rather that there are more people in these areas to report them. In reality, these sky falls, as the team affectionately calls them, occur over the majority of the United States.
As people spot fireballs, they share this information in many ways from Twitter to local radio stations to official reports to the American Meteor Society (AMS). The submission form on the AMS website collects eyewitness information, including where the person was located, what time he or she saw the meteor and what direction it was moving.
Any and all information helps the team characterize fireballs and calculate their trajectories, allowing them to estimate whether the event resulted in meteorites and if so where they could be found. Although being accurate in sighting reports is important, the most helpful thing people can do, according to the team, is post a video with information about where it was recorded.
While characterizing fireballs is the main objective of MEO’s efforts, it’s worth noting that part of the job is determining when a sighting isn’t a fireball.
“Once, a number of people reported a bright light over Lake Michigan, and after some digging it was determined that it was not a fireball but a stunt put on by a popular energy drink company that involved a stuntman jumping out of a plane with a flare,” shared Moser.
Although the report turned out to not be a natural phenomenon, such anecdotes shouldn’t deter people from reporting what they see. It can be hard to know what’s right before one’s eyes, and that’s exactly why the MEO team is there to help increase public awareness of the fireballs in the night sky.
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