Factual error: Science Officer Tilly calls the planet Trill a "very big" planet. It has an area of 500 million square kilometers. But that is not so large a planet. The Earth has an area of 510,100,000 square kilometers. So Trill is slightly smaller than Earth. Not really a "very big" planet.
The War Without, the War Within - S1-E14
Other mistake: In dialogue, Starbase 1 is described as "100 AU from Earth," which is over three times the orbital distance of Neptune, but still within the Solar System. But the onscreen graphic shows the starbase next to a planet that can be visually recognized as Earth; portions of North America, including the Florida peninsula and the Gulf of St. Lawrence, are visible.
Answer: The planet shown could well be a terraformed moon on the outskirts of the Solar System. The planet is not shown in great detail behind the damaged station.