Voyager voyages outside of the Solar System

The Voyager-1 spacecraft has become the first manmade object to leave the Solar System. Scientists say the probe's instruments indicate it has moved beyond the bubble of hot gas from our Sun and is now moving in the space between the stars. Launched in 1977, Voyager was sent initially to study the outer planets, but then just kept on going. Today, the veteran Nasa mission is almost 19 billion km from home. This distance is so vast that it takes 17 hours now for a radio signal sent from Voyager to reach receivers here on Earth. But what will not be leaving our Solar System for now is Twitter, which has filed for an initial public offering of stock. The company sent its filing confidentially to the Securities and Exchange Commission. Many soon-to-be-public companies have been taking advantage of new regulations passed last year in the Jumpstart Our Business Startups (JOBS) Act, which allows smaller businesses to keep its financial data out of the public's eye. Under the act, companies with less than US$1 billion of annual revenue can file for confidential IPOs. Nevertheless, it's a good time for Twitter to be going public, since the stock market has been treating social networks particularly well lately. After bumpy starts, both Facebook and LinkedIn hit all-time highs on Wednesday. But if precedent is followed, the social networking bubble will one day burst, so enjoy it while you can. And it's not just social networks who are after a piece of the pie - Hilton Worldwide has filed for an initial public offering to raise up to US$1.25 billion. It is being sold by the private equity group Blackstone, which bought Hilton in 2007 for US$26.7 billion. Blackstone's filing did not say how much of Hilton it plans to sell or which stock exchange it will use. It will use the proceeds to pay off debt.