SCIENTISTS say the Earth is about to get a second moon, on Wednesday. A small asteroid is going to be captured by Earth’s gravitational pull and temporarily become a “mini-moon”. This space visitor will be around from Sept 29 for a couple of months before escaping from Earth’s gravity again. However, the second moon is going to be too small and dim to be seen, except through a professional telescope. The asteroid was first spotted by Nasa’s Asteroid Terrestrial-Impact Last Alert System (Atlas) on August 7. Scientists worked out its trajectory in a study published in Research Notes of the American Astronomical Society. The asteroid, which scientists refer to as 2024 PT5, hails from the Arjuna asteroid belt, which contains rocks that follow an orbit quite similar to Earth’s. Occasionally, some of these asteroids get relatively close, getting as near as 2.8 million miles (4.5 million km) from our planet. According to the researchers involved in the study, if an asteroid like this is moving at a relatively slow speed of around 2,200mph (3,540km/h), Earth’s gravitational field can exert a strong influence, enough to trap it temporarily. Which is exactly what’s about to happen — starting this weekend, this small asteroid will spend about two months orbiting Earth. Dr Jennifer Millard, astronomer and host of the Awesome Astronomy podcast, told the programme that the asteroid would enter orbit on the 29th of September and then was predicted to leave on 25 November. “It’s not going to complete a full revolution of our planet, it’s just going to kind of have its orbit altered, just twisted slightly by our own planet and then it’ll continue on its merry way,” she said. The asteroid is approximately 32ft (10m) long, which is tiny in comparison to Earth’s moon, which has a diameter of approximately 3,474km.