In a vacuum, there is no medium to conduct or transfer heat away from the object, so the only way for it to lose heat is through radiation. The rate of heat loss through radiation depends on the object's surface area, emissivity, and the Stefan-Boltzmann law.
Assuming that the object's surface area and emissivity remain constant, and that the initial conditions are the same (temperature, atmospheric pressure, etc.), the time it takes for the object to reach a temperature of 25°C in a vacuum would be significantly longer compared to a scenario with atmospheric pressure.
Without specific information about the object's properties or the environment, it is challenging to provide an accurate estimate. However, it is safe to say that the cooling process would be considerably slower in a vacuum due to the absence of convective heat transfer.
If you can provide more details about the object or the specific conditions, I may be able to give you a more precise answer.