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Under close surveillance, the asteroid Apophis will pass near Earth on Saturday

2021-03-05T15:16:35.055Z


Astronomers, who for a time considered this large stone as a serious threat, take the opportunity to observe it and prepare its


It measures 340 m, a little longer than the Eiffel Tower, and has, in the past, given a cold sweat to astronomers.

Saturday, at 2:15 am (Paris time), the asteroid Apophis will cross the road of our planet before moving away, to better come back in the vicinity in eight years.

Does the one named after the Egyptian god of chaos want to send us some kind of warning?

Relax: If this isn't the last you'll hear about it, the probability of this object hitting Earth in the course of the century is currently one in 220,000.

"It does not represent a danger in the short term", confirms Patrick Michel, research director at the CNRS at the Lagrange observatory in Nice.

So much the better, because an object of this size could cause destruction on a regional scale ...

A monitored threat

A threat like this is constantly reassessed as astronomers measure it.

Thus it was estimated, a time after the discovery of Apophis in 2004, that the risk of impact for 2029 was 3%!

Fortunately, a danger quickly averted!

But it was not until his previous "cuckoo", in 2013, to be reassured about the impossibility of a disaster in 2036 ...

As we never know enough about these cumbersome visitors that are the so-called “near-Earth” asteroids, dozens of scientists are currently taking advantage of the arrival of Apophis in the vicinity of the Earth to amass knowledge.

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For several weeks now, these specialists have been engaged in an astonishing exercise: to act as if this object were not known to them and as if it was really threatening.

They thus tested the detection capabilities of current systems.

Good news: Apophis has been "spotted" by the NEOWISE infrared space telescope.

The participants also tested their coordination and reaction skills.

“This is a semi-virtual exercise carried out within the international asteroid warning network.

We take the opportunity to organize ourselves on a global scale, to see if there are things to improve, ”explains Patrick Michel, who is co-piloting this campaign.

“The risk of impact by an asteroid is the least likely natural risk, but it is the only one that, if organized well, can be predicted and avoided.

"

Because Apophis will be "only" 17 million kilometers from Earth on Saturday, experts will be able to more clearly identify its shape, more precisely calculate its location and better observe how it turns on itself.

To do this, they can count on the radio telescopes of the Goldstone observatory, in California, pointed since Wednesday on the impudent pebble that they will scrutinize until March 14.

On the other hand, we will have to do without an even more powerful instrument, the Arecibo radio telescope in Puerto Rico, which collapsed last December after 57 years of loyal service.

Visible to the naked eye in eight years

The data collected will allow researchers to prepare for the next passage of Apophis, much more impressive this one.

On April 13, 2029, the asteroid will be only 38,000 km away, or one tenth of the Earth-Moon distance, at an altitude where we can find artificial satellites.

Not enough to pose a security problem, reassures Jean-Yves Prado, former engineer at the National Center for Space Studies (Cnes): “It is true that geostationary satellites are at the same distance from the Earth as the place where it will pass, but they are in the plane of the equator.

However, the point closest to Apophis when he is at this distance, is not in the equator.

He's in the northern hemisphere.

When Apophis crosses the plane of the equator, it will be 60,000 km away, so there is no risk for the satellites.

"

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During this event, the asteroid will be visible to the naked eye, a spectacle that humans will not see again anytime soon ... Such large objects passing so close to Earth?

There is only one per millennium!

Not sure that Apophis comes out unscathed.

Its sudden proximity to our planet will be such that it could be distorted by Earth's gravity, which could otherwise influence its rotation.

"The conditions of the passage of 2029 will depend on the probabilities of impacts in the decades to come", affirms Jean-Yves Prado.

As with the weather, the further in time, the less reliable the forecast.

Astronomers are currently trying to measure tiny changes in trajectory linked to a thermal effect, the Yarkovsky effect: millimeters which, accumulated over time, turn into kilometers.

According to one of the discoverers of Apophis, researcher Dave Tholen, of the University of Hawaii, taking this parameter into account does not completely and definitively exclude a collision in 2068. “Apophis, we're not going get rid of it like that.

It is an asteroid that must be taken into consideration for future generations, ”warns Jean-Yves Prado.

Patrick Michel tempers: “For 2068, the probability is currently one in 380,000. For an object of this size, the impact frequency is once every 100,000 years. There is nothing to worry about. Certainly, from the moment when the probability is still not zero, it must be monitored. But 2068, that would give us time to deal with it. For us, this question of planetary defense is not a source of anxiety. On the contrary, it is an opportunity! “Currently under study, a mission, in which the Cnes would participate, to place a probe on Apophis before he presents himself in 2029. History to mark this stone well in the pants.

Source: leparis

All tech articles on 2021-03-05

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