“Gravity’’ won’t be held down. The Warner Bros. astronaut adventure directed by Alfonso Cuaron and starring Sandra Bullock and George Clooney landed in the top spot at the box office for the second weekend in a row, according to studio estimates Sunday. ‘‘Gravity’’ earned $44.3 million, raising its domestic total to $123.4 million. ‘‘They say what goes up must come down, but that’s not really true with ‘Gravity,’ ’’ said Paul Dergarabedian, senior media analyst for box-office tracker Rentrak. ‘‘To have opened as big as it did last week and only drop 21 percent, that’s really an amazing hold. It’s a direct testament to the word of mouth on the movie.’’ Sony’s ‘‘Captain Phillips’’ launched in second place with $26 million. The high seas drama directed by Paul Greengrass stars Tom Hanks as a cargo ship captain held captive by Somali pirates. ‘‘We think the success of ‘Gravity’ will also bode well for ‘Captain Phillips,’ ’’ said Rory Bruer, head of distribution for Sony Pictures. The animated Sony movie ‘‘Cloudy With a Chance of Meatballs 2’’ took third place in its third weekend with $14.2 million, bringing its domestic haul to $78 million. The weekend’s only other new release, ‘‘Machete Kills,’’ opened in fourth place with $3.8 million.