NASA is currently tracking four asteroids that are headed towards Earth. According to the agency’s Center for Near Earth Object Studies (CNEOS), the largest asteroid from the group is almost as big as the Leaning Tower of Pisa in Italy.

The first asteroid that will fly past Earth on Wednesday has been identified by the agency as 2019 SX3. As indicated in CNEOS’ database, this asteroid is currently traveling at a speed of almost 20,000 miles per hour and has an estimated diameter of about 164 feet.

2019 SX3 is expected to approach the planet on Oct. 2 at 2:00 am EDT. During this time, the asteroid will be about 0.02217 astronomical units or roughly 2.1 million miles from the planet’s center.

Trailing behind 2019 SX3 is an asteroid known as 2019 SA6. This space rock is flying with an estimated velocity of 37,000 miles per hour. CNEOS noted that the asteroid is about 167 feet wide, making it the biggest rock in the group.

According to the agency, 2019 SX3 will zip past Earth on Oct. 2 at 11:35 am EDT from a distance of about 0.03014 astronomical units or around 2.8 million miles away.

The third asteroid that’s expected to approach the planet on Wednesday is called 2018 LG4. As indicated in CNEOS’ database, this asteroid is moving towards Earth at a speed of about 18,000 miles per hour. CNEOS estimated that the asteroid has a diameter of around 69 feet.

2018 LG4 will fly past Earth on Oct. 2 at 5:49 pm EDT. During its approach, the asteroid is expected to be about 0.03531 astronomical units or roughly 3.3 million miles from the planet’s center.

The last asteroid that’s set to approach Earth tomorrow is called 2019 SL8. This asteroid is currently moving at a speed of almost 30,000 miles per hour and has an estimated diameter of around 131 feet.

CNEOS predicted that 2019 SL8 will fly past the planet on Oct. 2 at 10:40 pm EDT. During this time, the asteroid will be about 0.02021 astronomical units or roughly 1.9 million miles away from Earth.