The astronomer Scott Shepard discovered an asteroid that was renamed 2025 SC79approximately 700 meterswhich orbits the Sun in just 127.5 daysplacing it third in the list of the fastest known asteroids in the Solar System (despite many reporting that it is the second fastest). The only fastest asteroids we know of are 2025 GN1 (114.7 days) e 2021 PH27 (114.6 days). Like the two roommates on the podium, 2025 SC79 – discovered on September 27, 2025 – is an asteroid with ainternal orbit to the terrestrial one: in these cases we speak of asteroids of the Atira groupof which only a few dozen are known. They are in fact asteroids very difficult to observe because, having an orbit inside the Earth’s, they are always at a small angular distance from the Sun and therefore are practically observable only at twilight, when the sky is not yet perfectly dark: this is why some have nicknamed them “twilight asteroids”. Despite its generous size and its not enormous distance from Earth, currently 2025 SC79 it poses no danger to our planet.
New asteroid 2025 SC79: orbit and risk of impact with Earth
Like the other Atira asteroids, 2025 SC79 was discovered while bathed in the glow of twilight. During subsequent observations, its position in the sky was calculated orbitwhich is internal not only to that of the Earth but also to that of Venus and crosses the orbit of Mercurythe planet closest to the Sun. Al perihelionthat is, at the point of maximum proximity to the Sun, the asteroid is just 4 million km from our star; at aphelion (maximum distance from the Sun) it reaches i 10.6 million km from the Sun.
Estimating its ability to reflect light (in technical jargon called albedo) for this asteroid a size of approximately is estimated 700 meters: in the event of an impact with the Earth, the destruction would extend to entire regions if not entire countries. Fortunately, however, there is currently no reason to worry about such a scenario: distance minimal between the orbit of this celestial body and the orbit of the Earth (which astronomers call MOID, Minimum Orbital Intersection Distance) is of 4.3 million kmenough to avoid any danger.
That doesn’t mean the situation will stay like this forever, however. Being in a rather “crowded” point of the Solar System, in relative proximity to the Sun, Mercury, Venus and Earth, over the millennia the gravitational perturbations of these celestial bodies can modify the orbit of 2025 SC79 perhaps reducing the MOID with the Earth. Predictions of this type are however very complex and certainly premature at the moment.
The asteroid’s orbit has already taken him to “hide” behind the Sunso it will not be visible from Earth for a few months. When it “re-emerges” it will be possible to study it in more depth: the main objectives of astronomers are to understand its nature chemical compositionwhat dynamics may have brought it so close to the Sun and how it can resist the high temperatures it faces.
Because faster asteroids are closer to the Sun
It is no coincidence that the entire podium of the fastest asteroids ever discovered is populated by covers from the Atira group, with an orbit inside the Earth’s. The reason lies in Kepler’s third lawaccording to which the closer a body is to the Sun, the less time it takes to complete an orbit. A consequence of this law is that the bodies closest to the Sun are also those that move most rapidly.
An example: the Earth it is located on average 150 million km from the Sun and has an average orbital speed of approximately 30km/s; Mercurythe closest planet to the Sun about 58 million km from our star, is moving at about 47 km/swhile Neptune, the farthest at about 4.5 billion km, has a speed of approx 5km/s.
