Data science pipelines consist of data preprocessing and transformation, and a typical pipeline comprises a series of operators, such as DataFrame filtering and groupby. As practitioners seek tools to handle larger-scale data while maintaining APIs compatible with popular single-machine libraries (e.g., pandas), scaling such a pipeline requires efficient distribution of decomposed tasks across the cluster and fine-grained, key-level intermediate storage management, two challenges that existing systems have not effectively addressed. Motivated by the requirements of scaling diverse data science applications, we present the design and implementation of Xorbits, a native scalable data science engine built on our decentralized actor model, Xoscar. Our actor model can eliminate dependency on a global scheduler and enable fast actor task scheduling. We also provide reference-based distributed storage with unified access across heterogeneous memory resources. Our evaluation demonstrates that Xorbits achieves up to 3.22X speedup on 3 machine learning pipelines and 22 data analysis workloads compared to state-of-the-art solutions. Xorbits is available on PyPI with nearly 1k daily downloads and has been successfully deployed in production environments.