(CNN) -- In many ways Sandra Bullock is an unlikely star -- just as "Gravity," the film that may earn her another Oscar nomination, is an unlikely runaway hit. And it's just opening Friday.
In order to not give too much away (we know how much you hate spoilers), we will just say that "Gravity" is about some astronauts who run into trouble while in space. So, how can a 90-minute film about two very likable people -- Bullock and George Clooney -- floating beyond Earth be termed a "thriller"?
The same way Bullock, who for the most part eschews the trappings of Hollywood, has managed to become such a huge celebrity, who can seemingly do no wrong. If ever there was a contest for "America's sweetheart," the actress would be tough to beat, since that has been her moniker for the past few years.
Examine the evidence: Bullock is a woman who -- at the height of a devastating marital breakup from Jesse James in 2010, when lurid tabloid headlines appeared about his alleged affairs -- shocked the world with news that she had secretly adopted an African-American son from New Orleans. Not only was it surprising that the Oscar-winning actress had such a tight circle that she was able to conceal a monumental personal moment, but unlike some other celebs who had been criticized in the black community for transracial adoptions, Bullock and her decision were mostly embraced.
The "Blind Side" star has made paparazzi literally chase her outside the usual city limits, choosing to build her life in cities like Austin, Texas, and New Orleans. Articles about her are apt to contain lines like those in a recent Vogue piece: "The beloved -- and eminently bankable -- Sandra Bullock soars to new heights in the season's hotly anticipated outer-space thriller, 'Gravity.'"
She is firmly in the top 10 list of Hollywood's highest paid actresses and her films tend to make money. Even other celebrities adore her. "Avengers" star Chris Evans has been quoted as saying Bullock was his first celebrity crush.
"I saw 'Speed' when I was in seventh grade, and I was like, that's my lady," Evans said. "I literally had a big poster (of her)."
It's easy to see why a preteen Evans fell for Bullock. The daughter of an Army employee and a German vocal coach, Bullock has continually struck a chord with fans -- coming across as extremely genuine in a field which makes its magic through pretending. When Bullock won the best actress Oscar for "The Blind Side" in 2010, she brought some to tears with her heartfelt tribute to her late mother.
"If I can take this moment to thank Helga B. for not letting me ride in cars with boys until I was 18 -- because she was right. I would have done what she said I was going to do," Bullock said. "For making me practice every day when I got home. Piano, ballet, whatever it is I wanted to be -- she said to be an artist, you had to practice every day. And for reminding her daughters that there's no race, no religion, no class system, no color, nothing, no sexual orientation that makes us better than anyone else. We are all deserving of love. So, to that trailblazer, who allowed me to have that. And this."
In interviews Bullock can be funny, self-deprecating and just downright cool. During an appearance in June on "The Late Late Show with Craig Ferguson" to promote her buddy cop comedy, "The Heat," she and the host good-naturedly took verbal swipes at each other. When Ferguson mentioned the film "Dumb and Dumber" (in an apparent reference to the way their interview was going), Bullock volleyed back about that movie.
"Poop humor is fun," she said jokingly. "If you do the toilet scenes well and commit to them they can be really, really powerful."
Not many Academy Award winners would tackle such a subject, but it's not surprising from Bullock, who recently proudly told Us Weekly that her now-3-year-old son, Louis, is fully potty-trained. While the actress has almost always been tagged as more girl next door than vixen, motherhood has clearly helped settle her even more.
She's been very outspoken about the fact that she would give it all up, the career and the fame, if it wasn't good for her son in any way.
"I don't want him to have pressures brought on by what I do. I will quit. I will leave," she told Vogue. "If I see whatever I'm doing affecting him negatively, I will pack up and move to Alaska."
Which probably helps explain why the self-professed homebody would much rather be spending time with her toddler than working the press, as she did recently at the premiere of "Gravity." In the Alfonso Cuaron-directed film, she plays Ryan Stone, a medical engineer on her first space mission. The movie calls for Bullock to be in some pretty out-there situations, but she told CNN at the premiere that being on the red carpet was extreme enough for her.
"That's the most extreme situation I've experienced in a long time," Bullock said. "Being in front of a camera, in a nice dress, getting all dressed up is extreme. There's a lot of other extreme situations, you know, just getting out of bed sometimes is extreme -- but I do it. Just got to do it, just got to get up. Put your sweatpants on, brush off the dog hair and just get out of the house!"
Following the film's debut at the Toronto International Film Festival in September, chatter immediately started that Bullock could once again be a contender for an Oscar. For director Cuaron, his star's performance was so strong, it overshadowed even the special effects and technology used to make her appear weightless in "Gravity."
"When you see Sandra performing ... with the truthfulness she performed, you forget it was any technology around," he told Access Hollywood.