NEW YORK, Oct 28 (Reuters) - Blackstone Group LP said on Wednesday third-quarter distributable earnings rose 9% year-on-year, as the world’s largest manager of alternative assets such as private equity and real estate took advantage of a rise in corporate valuations to cash out on some of its leverage buyout investments. Distributable earnings - the cash available for paying dividends to shareholders - totaled $772 million, up from $710 million a year earlier. This translated into distributable earnings per share of 63 cents, surpassing analysts’ average estimate of 57 cents, according to data compiled by Refinitiv. Blackstone said its private equity portfolio appreciated 12.2% in the third quarter, compared with an 8.5% rise in the benchmark S&P 500 stock index over the same period. Opportunistic and core real estate funds rose 6.4% and 3.5% respectively.