Four kilometers big asteroid "Florence" is already visible with small telescopes

Tomorrow, one of the largest known asteroids flies past the earth - fortunately at a safe distance. The 4.4 kilometer big "3122 Florence" passes us at about 2:00 pm in about seven million kilometers distance, the 18-fold moon distance. The asteroid is already so bright that it can be seen with a small telescope. For the astronomers, this passage is an opportunity to learn more about this as a potentially dangerous asteroid.

More than four kilometers large - the asteroid will pass us at a safe distance. © Pitris/ thinksto

3122 Florence was already discovered in 1981 by an Australian astronomer. The asteroid orbits the sun on a slightly eccentric trajectory, which allows it to oscillate between earth and half the distance to Jupiter. It needs two years and four months for one round.

Already visible with small telescope

Because of its enormous size of 4.35 kilometers and the regular approach to the Earth's orbit, Florence is one of the asteroids that is constantly monitored by astronomers. Officially, the asteroid is also classified as "potentially dangerous" because if a chunk of this size were to hit the earth, a global catastrophe could result.

In these days, the giant asteroid is particularly good to see at the night sky with a small telescope or good binoculars. As early as the 27th of August its slow movement was observed by the constellations of southern Pisces and Capricorn. The asteroid now moves through the constellations Aquarius and Dolphin.

3122 Florence is moving in the sky through the constellations Capricorn and Aquarius. © Sky & Telescope

So close, no other giant asteroid has come before

On 01 September 2017 about 14:00 o'clock 3122 Florence is about to pass the earth as close as since 1890 not anymore. With almost 50,000 kilometers per hour, the asteroid rushes past us about seven million kilometers away - which is about 18 times the distance from the moon. Therefore, we do not have to fear a collision, as the astronomers emphasize.

Many asteroids have already moved closer to us than Florence will do, but they were all much smaller, explains Paul Chodas of NASA's Jet Propulsion Laboratory in Pasadena. Florence has been NASA's largest asteroid since the beginning of surveillance of Earth-like asteroids.

The next similar flyby of Florence occurs only after the year 2500.

3122 Florence is passing us in 18-fold moon distance. © NASA

Does Florence have a moon?

The passage of this gigantic rock is especially exciting for asteroid researchers, because it offers the chance to learn more about this giant chunks. It is true that 3122 Florence rotates around itself every 2,4 hours, but the direction in which it is turning is still unknown. The exact shape and surface structure of the asteroid are still unclear.

The recordings could also reveal whether the asteroid has its own moon or even consists of two closely spaced chunks. For in previous observations the astronomers had recorded a regular, slight change in the light curve of the chunk. This could theoretically point to a moon.

If Florence has a moon, then our chance is now excellent to detect it, says a statement from NASA's Goldstone Observatory.

In the sights of several telescopes

Astronomers will be directed worldwide on the asteroids and also actively scan it by radar. The NASA radar system from Goldstone in California targets it during the pre-flight, and the Arecibo Radiotelescope in Puerto Rico is to watch Florence in the first week of September. In Australia, astronomers also want to scan the asteroids with an active radar.

The flyby gives us an excellent chance to perform detailed measurements of this large earth-like asteroid, says Chodas. Above all, we hope to get high-resolution images that show the surface of Florence up to about ten meters.

Source: NASA, CNEOS

Update: Live Webcast of giant asteroid 3122 Florence