We currently know about 2,300 potentially hazardous asteroids or PHAs (and quite a few comets) that could damage Earth one day. These are objects that pass close to Earth’s orbit and have diameters of 460 feet (140 meters) or larger. At a minimum, this is large enough to cause regional devastation or a major tsunami in the event of an impact. Fortunately, such encounters are rare, occurring approximately once every 10,000 years.

PHAs are larger—one kilometer (0.6 mi) and above—they number about 153 and strike once every 500,000 years. Astronomers are tracking each of them and assure that no attacks are expected in the foreseeable future.

NEA totals

This latest graph shows the statistics for the detection of Near-Earth Asteroids (NEAs), Potentially Hazardous Asteroids (PHAs) and Near-Earth Comets (NEC) as of October 30, 2022. Compiled by the Center for Near-Earth Object Studies (CNEOS) .
Contribute / JPL-CNEOS

There is only one problem. we did not find All of potential killers so far. NASA satellite data suggests there are 4,000 to 6,000 potentially hazardous asteroids larger than 328 feet (100 meters), so we still have about half of them left. This is why the recent discovery of three “aurora” asteroids is good news and a harbinger of the future.

Using the Dark Energy Camera at the Cerro Tololo Inter-American Observatory in Chile, astronomers have found three Near-Earth Asteroids (NEAs) in the twilight sky almost hidden in solar flare. They’re part of an elusive group of asteroids that lurk within the orbits of Earth and Venus. Like Venus, it is only visible during twilight because it never appears far from the sun. One of them, called 2022 AP7, is the largest PHA discovered in the past eight years.

PHA 2022 MYR 4

PHA regularly passes safely near the ground. For example, asteroid 2022 RM4 (pictured here) flies the planet on Tuesday afternoon, November 1 at a distance of 1.4 million miles (2.3 million kilometers). Its width is estimated to be between 1,100 and 2,400 feet (330-740 metres).
Contributed by / Gianluca Massi, The Virtual Telescope Project

The ejector is 0.9 miles (1.5 km) wide and has an orbit that may one day put it in Earth’s path. Other asteroids – 2021 LJ4 and 2021 PH27 – have orbits that remain safely within Earth’s orbit. The latter is of particular interest to astronomers and astrophysicists because it is the closest known asteroid to the Sun and has a surface temperature hot enough to melt lead.

“Our aurora survey roams the region within the orbits of Earth and Venus in search of asteroids,” said Scott Sheppard, an astronomer at the Earth and Planetary Laboratory at the Carnegie Institution for Science and lead author of the paper describing this work. “So far we have found two large asteroids near Earth that are about one kilometer in diameter, a size we call planetary killers.”

Finding asteroids near the sun is not easy for obvious reasons. So far, only about 25 of them have been captured with orbits within Earth’s orbit entirely of glare.

twilight with crescent

Twilight is a tough time to look for asteroids orbiting closer to the sun than Earth, but it’s the only time. Hopefully, additional searches with the Dark Energy Camera and the like will give us a more realistic idea of ​​how many asteroids populate the space near the Sun.
Contribute / Bob King

The team had two short 10-minute windows each night when the sky was dark enough to survey the area. Moreover, they had to make those observations near the horizon, as the atmosphere haze and distorted their images. This is where the Dark Energy Camera proves its power. It can capture large expanses of sky with great sensitivity – exactly what you need when you’re on a deadline.

“Large swaths of sky are required because inner asteroids are rare, and deep images are needed because asteroids are faint and you counteract bright twilight skies near the sun as well as the distorting influence of Earth’s atmosphere,” Sheppard said.

Asteroids far from the sun are relatively easy to spot, as we can spot them in dark skies. This biases our ideas about how these objects are distributed across the solar system. Those that come closer to Earth from the direction of the Sun are harder to detect, which makes dealing with them more important than ever before – dare I say – it’s too late.

North and South of Torres

The northern and southern meteor showers will be active between now and mid-November. Bull rates are usually low and meteors move relatively slowly across the sky, but fireballs are common. The meteors will appear to stream from two locations west of Taurus below the Pleiades.
Contribute / Stellarium

While we’re on the topic of space rocks, fragments of Comet 2P/Encke will light up the sky around mid-month in a pair of meteor showers, south and north of the Taurids. At best we’ll only see about 10 meteors per hour. On the bright side they are known for their fireballs.

Both displays will radiate from points in the constellation Taurus not far from the Pleiades star cluster. Meteor shower experts are also anticipating a contribution from a related shower called the Taurid Swarm, so keep your eyes peeled for sparks.

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