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OUT OF THIS WORLD | What's Up In Space - a weekly look at the biggest news coming down to Earth from space

House-sized asteroid caught zipping through Earth's shadow


Scott Sutherland
Meteorologist/Science Writer

Wednesday, November 2, 2016, 4:47 PM - Astronomers capture what could be the very first video of a full asteroid eclipse, a bright fireball lights up the sky over Pennsylvania, and the tally of near-Earth asteroids now tops 15,000 objects! It's NEO week on What's Up In Space!

Asteroid's close flyby results in eclipse

In what may be a first for the astronomical community, the Virtual Telescope Project has captured a video of a small asteroid being eclipsed by Earth.

Asteroid 2016 VA was first spotted by the Catalina Sky Survey's Mt. Lemmon Observatory, at 4:24 a.m. EDT on November 1, 2016, about 16 hours before the space rock made its closest pass by Earth.


A look at how this close pass would have appeared for someone at station-keeping roughly 50 metres from asteroid 2016 VA, during its November 1 flyby of Earth. Credits: Data - NASA JPL, Background Image - Celestia space simulation software, Labels: S. Sutherland

At 8:42 p.m. EDT, 2016 VA came as close as 75,000 kilometres from the planet. That's roughly 20 per cent of the distance of the Moon, and a little over twice the distance to the ring of geosynchronous communication and weather satellites that orbit the planet.

Astronomers estimate it as being around 16 metres wide - although the estimate varies from 7 to 22 metres, depending on assumptions about its albedo (ie: how much sunlight it reflects) - or roughly the size of a house. That's smaller than the object that caused the Chelyabinsk bolide, in February of 2013. Still, if it had made a direct encounter with Earth, rather than passing by harmlessly, it would have made a spectacular showing over any populated area.

The most notable part of this flyby, however, is that the asteroid's path through space took it straight through Earth's shadow!

While this kind of event has apparently been observed before, astronomers with the Virtual Telescope Project believe that this is the very first time a complete asteroid eclipse has been recorded!


This animation tracks 2016 VA (the bright spot near the centre of the movie) as it slips into Earth's shadow and then re-emerges 10 minutes, 50 seconds later. Credit: G. Masi, Virtual Telescope Project.

Why wasn't this asteroid detected sooner? It's small, and it's fast.

It's an unfortunate fact that, even as good as the current monitoring programs are, and even as skilled as astronomers are in finding these objects and tracking them, the smaller an object is, and the faster that it's moving, the harder it is to find. So, smaller asteroids need to get fairly close to Earth before they can be picked out from the background of space.

(H/T to Universe Today)


The orbit of 2016 VA, compared to the inner planets. Credits: Background image - Minor Planet Center, Labels - S. Sutherland


DO YOU KNOW HOW TO FIND A METEORITE? In an upcoming feature on theweathernetwork.com, meteorologist Scott Sutherland speaks to scientists at the Royal Ontario Museum, to find out where meteorites come from, and how to find them here on Earth!


A bright green fireball flares over NY and PA

Who spotted this one?

At 8:15 p.m. EDT on Tuesday night, over 160 observers, from Detroit to Gananoque and as far south as Washington, D.C., spied a bright fireball in the night sky!


American Meteor Society's "heat map" of observations for the November 1, 2016 fireball over Pennsylvania. Brighter colours indicate more observations in an area, and the estimated trajectory of the fireball is plotted as the arrow, with the green marker at its start and the red marker at its end. Credit: AMS

Although this one was apparently not captured on camera (or at least no footage has yet surfaced), based on eyewitness reports, it was quite spectacular.

Twitter user "isabelle" reported seeing it "streaking downward (likely North to South)" from the Caledon, ON area, and said that it was "bright green and very prominent," and that it "varied in brightness as if passing through clouds."

We'll post more on this as updates come in!

Near-Earth asteroid log tops 15,000 entries!

Astronomers have been spotting and cataloguing near-Earth asteroids for decades now, and their records just surpassed 15,000 entries!

According to NASA:

The 15,000th near-Earth asteroid is designated 2016 TB57. It was discovered on Oct. 13 by observers at the Mount Lemmon Survey, an element of the NASA-funded Catalina Sky Survey in Tucson, Arizona. 2016 TB57 is a rather small asteroid - about 50 to 115 feet (16 to 36 meters) in size...

2016 TB57 safely passed by Earth on October 31, 2016, at a distance of over 5 times the distance to the Moon.


Orbit of NEO 2016 TB57. Credit: NASA

A near-Earth object, or NEO, is defined as being a comet or asteroid with a minimum distance to the Sun (perihelion) of 195 million kilometres or less. Thus, this includes all objects that come to within at least 50 million kilometres or so of Earth's orbit. Given the potential dangers of a close-approaching NEO, there are several survey projects around the world that are constantly on the lookout for these objects, and according to NASA, the catalogue grows by an average of 30 entries every week.

The increased rate of discoveries shown in the Tweet above is not due to any increase in the actual number of asteroids and meteoroids out there. It's due to advances in technology and the dedication of those involved in surveying for NEOs. These 15,000 NEOs include over 90 per cent of the estimated population of asteroids over 1 kilometre wide, however, according to NASA, it only includes 27 per cent of the estimated number of asteroids that are greater than 140 metres in size.

The goal of these programs is to locate all NEOs, and in particular the Potentially Hazardous Asteroids (PHAs) - those that are at least 150 metres wide and come closer than 7.5 million kilometres to Earth (or about 19 times the distance to the Moon). Of the over 15,000 NEOs that are known, NASA currently tracks 1,739 PHAs.

Even with over 15,000 near-Earth asteroids now catalogued, it should be noted that we are in no danger of being hit by any of these objects.

The NEO that perhaps poses the greatest risk of impact is currently half-a-kilometre wide asteroid 101955 Bennu, which has a cumulative chance of about 1 in 2,700 to hit Earth sometime between the years 2175 and 2199. Even that still means a 99.963 per cent chance that the asteroid will miss us, though. So, it's really not something to worry about, and hopefully we'll have the technology to divert Bennu, should it actually turn out to be a true hazard to us in the future. NASA's OSIRIS-REx spacecraft is currently on its way to Bennu, to map the asteroid and return a sample of it back to Earth for study.

The true danger from NEOs may be from those we do not yet know about.

"While no known NEO currently poses a risk of impact with Earth over the next 100 years," NASA Planetary Defense Officer Lindley Johnson said in a statement on Thursday, "we’ve found mostly the larger asteroids, and we have a lot more of the smaller but still potentially hazardous ones to find."

Sources: Virtual Telescope Project | American Meteor Society | NASA

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