It appears likely that ‘Oumuamua is not the only known interstellar object anymore. NASA has just provided more data regarding comet C/2019 Q4, and they think it is likely that the object originated far from the Solar System.
The discovery of the object was reported just a few days back after it was first observed on August 30 by Gennady Borisov at the MARGO observatory in Nauchnij, Crimea. This is not an official confirmation that the object is truly interstellar but the speed estimate and orbital parameters are so far strongly leaning in that direction.
"The comet's current velocity is high, about 93,000 miles per hour [150,000 kilometers per hour], which is well above the typical velocities of objects orbiting the Sun at that distance," Davide Farnocchia of NASA's Center for Near-Earth Object Studies at JPL said in a statement. "The high velocity indicates not only that the object likely originated from outside our Solar System, but also that it will leave and head back to interstellar space."
The object has a fuzzy appearance suggesting it has a core of ice materials that are evaporating as it gets closer to the Sun. It is currently 420 million kilometers (260 million miles) from our star coming in at a 40-degree angle with respect to the plane of the ecliptic (the orbit of the Earth), which C/2019 Q4 will cross on October 26. It will then reach its closest point to the Sun on December 8, being roughly 300 million kilometers (190 million miles) away, double the average distance between us and our star.
"The object will peak in brightness in mid-December and continue to be observable with moderate-size telescopes until April 2020," added Farnocchia. "After that, it will only be observable with larger professional telescopes through October 2020."
Observations by Karen Meech and her team at the University of Hawaii led to the estimation that the comet's nucleus is between 2 and 16 kilometers (1.2-10 miles) across. For better estimates of its size as well as other properties such as its rotation, we will have to wait for more observations.
When ‘Oumuamua was first discovered, researchers were able to estimate that at any given time there is at least one interstellar object within the orbit of Mars, but most of these will be too small and faint to be discovered.