By Mindy Weisberger
Huge asteroid set to fly past Earth Today
A skyscraper-sized asteroid will fly by Earth on Tuesday, making it the first space rock to come this close in nearly a century. While this asteroid will safely pass by our planet, NASA scientists are already preparing for closer calls in the future. NBC’s Gadi Schwartz reports for TODAY.
Mindy Weisberger is a LiveScience senior writer covering a general beat that includes climate change, paleontology, weird animal behavior, and space. Mindy holds an M.F.A.
in Film from Columbia University; prior to Live Science she produced, wrote and
directed media for the American Museum of Natural History in New York City.
Her videos about dinosaurs, astrophysics, biodiversity and evolution appear in museums and science centers worldwide, earning awards such as the CINE Golden Eagle and the Communicator Award of Excellence. Her writing has also appeared in Scientific American, The Washington Post and How It Works Magazine.
The space rock is more than twice as massive as the Empire State Building.
An enormous asteroid more massive than two Empire State Buildings is heading our way, but unlike the so-called planet-killer comet in the recent movie “Don’t Look Up,” this space rock will zoom harmlessly past Earth.
The stony asteroid, known as (7482) 1994 PC1, will pass at its closest on Jan. 18 at 4:51 p.m. EST (2151 GMT), traveling at 43,754 mph (70,415 km/h) and hurtling past Earth at
a distance of 0.01324 astronomical units — 1.2 million miles (nearly 2 million kilometers), according to NASA JPL-Caltech’s Solar System Dynamics (SSD).
That may sound like a safe distance — and it is! But by cosmic standards, it’s close for such a large object. Asteroid (7482) 1994 PC1 measures about 3,609 feet (1,100 meters) long, and even though there’s no danger of a collision with Earth, NASA classifies the asteroid as a potentially hazardous object. This term describes asteroids that measure over 460 feet (140 m) long and have orbits that carry them within 4.6 million miles (7.5 million km) of Earth’s orbit around the sun, according to NASA’s Asteroid Watch.
The approaching asteroid is also part of a larger category of space rocks known as near-Earth objects (NEOs), which pass within about 30 million miles (50 million km) of Earth’s orbital path. NASA’s NEO Observations Program finds, identifies and characterizes these objects; survey telescopes have found approximately 28,000 NEOs that measure at least 460 feet in diameter, and about 3,000 new sightings are added each year, according to the Center for Near Earth Object Studies (CNEOS).
“But as larger and more advanced survey telescopes turbocharge the search over
the next few years, a rapid uptick in discoveries is expected,” according to the CNEOS.
Once observers detect a near-Earth asteroid or comet, scientists analyze the object’s orbit to assess how close it might come to Earth. Though many thousands of asteroids and comets are currently zipping around the solar system, the objects in the CNEOS’ database pose no serious impact threats for the next 100 years or more, NASA says.
Astronomer Robert H. McNaught was the first to spot asteroid (7482) 1994 PC1, on
Aug. 9, 1994. Other scientists tracked its previous trips through our cosmic neighborhood by using McNaught’s observations to calculate the asteroid’s orbital path, speed and trajectory. They found that the asteroid orbits the sun once every 572 days, and they detected the visitor in telescope images going all the way back to 1974, according to Earth Sky. And on Jan. 18, if visibility is good, the asteroid will be bright enough to be seen in a dark-sky location at night with a backyard telescope, Earth Sky reported.
Close as the asteroid may be on Jan. 18, it came much closer on Jan. 17, 1933. That year, the space rock sailed past Earth — at a distance of about 699,000 miles (1.1 million km),
and it won’t come that close to us again until 2105, according to SSD. Watch Livestream
of Giant ‘Potentially Hazardous’ Asteroid 1994 PC1 Passing Earth Tomorrow.
Originally published on Live Science.
Some asteroids can ‘sneak up’ on us thanks to a quirk of the Earth’s rotation
that makes them seem like they are barely moving — making them hard to detect.
This is the warning of NASA-funded experts who investigated how telescopes nearly missed a 328-feet-wide asteroid that came within 43,500 miles of Earth back in 2019.
The space rock, dubbed ‘2019 OK‘, was the first object of its size to get that close to our planet since 1908 — but it was only spotted 24 hours before its closest approach.
The reason, the team determined, is because it was moving towards us in
such a way that its motion across the night sky was counteracted by the Earth’s spin.
Thus, to early warning systems like Pan-STARRS1 at Hawaii’s Haleakala Observatory — 2019 OK looked stationary, so did not set off the automated detection software.
In fact, the experts said, up to half of asteroids approaching Earth from a danger
zone east of ‘opposition’ likely undergo periods of such apparent slow motion.
An asteroid is said to be at opposition when its position in the night sky
places it along a line that intersects both the Earth and the sun.
This means that half of these asteroids could presently also be difficult to detect —
and computerized telescopes will need to be updated to take account of the effect.
Appear at practically the exact same point in the sky as they get closer.
This is because as the asteroid would appear to move eastward across the night sky,
such motion is counteracted by the Earth’s rotation — meaning it is seen from the exact same angle from the Earth even as it gets closer (represented by the series of parallel, dashed orange lines)
WHAT IF… 2019 OK HAD STRUCK EARTH?
While not big enough to cause a global catastrophe, 2019 OK would have wreaked considerable devastation had it impacted the Earth — especially in a densely-populated setting. ‘It’s a city-killer asteroid,’ Swinburne University astronomer Alan Duffy told the
Sydney Morning Herald.
‘It would have hit with over 30 times the energy of the atomic blast at Hiroshima.’
The study was undertaken by astronomer Richard Wainscoat of the University of Hawaiʻi at Mānoa and his colleagues.
‘Near-Earth Objects that approach from a direction east of opposition — most notably
0–2 hours [0–30°] east of opposition — are prone to periods of slow motion during their approach,’ the researchers explained in their paper.
“Potentially hazardous” asteroid to have close encounter with Earth Today.
‘The induced topocentric motion coming from Earth’s rotation cancels the natural eastward motion in the sky, making the object appear to be almost stationary, this makes discovery difficult.
‘Surveys should take extra care when surveying the sky in this direction, and aggressively follow-up new slow-moving objects.’
Had the apparent slow-motion phenomena not been in play with asteroid 2019 OK, the researchers said, the near-Earth object would likely have been detected up to four weeks before it made its closest approach to our planet.
As NASA defines it, a near-Earth object — or ‘NEO’— is anybody that comes within
28 million miles (45 million kilometres) of the Earth’s orbital path around the sun.
Any NEO whose orbit crosses that of our planet’s and is larger than 460 feet (140 meters) in diameter is further classified as a ‘potentially hazardous object’ (PHO).
In 1994, the US Congress mandated that NASA should catalog at least 90 per cent of NEOs larger than 0.6 miles (1 kilometre) across — that is, large enough that they would cause a global catastrophe should one ever impact the Earth.
That goal was achieved in 2011. In 2005, however, the directive was updated to include the cataloging of 90 per cent of all PHOs by the year 2020 — a goal which, to date, has still not been achieved, with the figure currently at around 40 per cent. ‘We’ve got a way to go,’ Professor Wainscoat told the Telegraph.
The risk of devastating impactors was recently highlighted in the Netflix film
“Don’t Look Up,” Leonardo DiCaprio and Jennifer Lawrence, star as scientists trying to warn a disinterested public about a comet on course to wipe out humanity. In case you are worrying about an Armageddon-themed demise, however, Professor Wainscoat said that people ‘shouldn’t lose sleep’ over the possibility. However, he added: ‘In the event that we find something that is going to hit the Earth we would like to do something about it!
‘It’s not a matter of finding them and sitting there and letting it hit.’
In fact, NASA is presently undertaking a mission to explore the feasibility
of diverting the course of an asteroid by crashing a space probe into it.
The DART ‘Double Asteroid Redirection Test’ mission launched from the Vandenberg Space Force Base in California last November and is expected to reach its target — the minor-planet moon Dimorphous — around late September this year. The full findings
of the study were published in the journal Icarus.
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