In a surprising new discovery, astronomers found that the closest neighbor to the sun is not Mercury but instead a fast-moving asteroid. This newly identified asteroid, which has been named 2021 PH27, zips around our sun at such an incredible speed that it completes a full orbit of the star in just 113 Earth days. In fact, it is by far the fastest orbiting asteroid that has ever been discovered in our Solar System and the second shortest orbital period among all space bodies as Mercury completes a full orbit in 88 days.
But unlike Mercury, 2021 PH27 orbits the sun in an elliptical path which brings it much closer to the star at an estimated distance of just 12.4 million miles (20 million kilometers) during its closest approach. To put this into better perspective, Mercury’s closest approach to the sun is at a distance of 29 million miles (47 million kilometers). When 2021 PH27 gets close to the sun, the surface temperature on the asteroid heats up to a whopping 900 degrees Fahrenheit (482 degrees Celsius) – hot enough to melt lead.
With that being said, the asteroid will not continue on this orbit as it will probably crash into the sun, Mercury, or Venus in approximately a few million years. On the other hand, it could be thrown out of orbit by gravitational interaction. But as of right now, it is zipping around our sun at exceptional speeds.
The asteroid was discovered on August 13th by astronomers who were using the Dark Energy Camera (DEC) on the Víctor M. Blanco 4-meter Telescope at the Cerro Tololo Inter-American Observatory in Chile. Based on their observations, the researchers believe that 2021 PH27 measures approximately 0.6 miles in width (1 kilometer).
As for how it ended up so close to the sun, it might have gotten thrown inwards out of the main asteroid belt between Mars and Jupiter. Another observation they made was that it has a 32 degree tilt in its orbit which may indicate that it is an extinct comet that was once located in the far areas of our Solar System and was pulled inwards when it traveled by one of the rocky planets.
For now, 2021 PH27 is moving behind the sun and won’t be visible again from Earth until the early part of next year. At that point, researchers will be able to study the asteroid in further detail.
An artist’s illustration of 2021 PH27 can be seen here.