(CNN) NASA's tractor-trailer-sized Dawn spacecraft is now in orbit around Ceres , becoming the first probe to orbit a dwarf planet.

The spacecraft was about 38,000 miles (61,000) kilometers from Ceres when it was captured by the dwarf planet's gravity, NASA said Friday.

Even before Ceres entered orbit, the early images from Dawn had mission scientists excited.

"Ceres has really surprised us," said Carol Raymond, Dawn's deputy principal investigator . "The first images have produced some really puzzling features."

One of the puzzles -- two bright white spots that showed up in photographs taken by Dawn in February.

"These spots were extremely surprising to the team, and they have been puzzling to the team and to everybody who's seen them."

The spots are in a crater that's 57 miles (92 kilometers) wide. The spot in the center of the crater is about twice as bright as the spot on the side of the crater.

"This extreme brightness was really unexpected," Raymond said. The Dawn team is "really, really excited about this feature because it is unique in the solar system."

Photos: Dawn: Mission to the beginning of the solar system Photos: Dawn: Mission to the beginning of the solar system Ceres has several craters and linear troughs. In this image taken by NASA's Dawn spacecraft on October 14, 2015, the large crater Lono can be seen near the top right of the photo. The crater below it is called Besua. Hide Caption 1 of 21 Photos: Dawn: Mission to the beginning of the solar system You can see part of Ceres' southern hemisphere in this image taken on October 18, 2015. The big crater in the middle of the picture is called Hamori after a Japanese god and protector of tree leaves. The crater is 37 miles (60 kilometers) in diameter. Dawn was 915 miles (1,470 kilometers) above Ceres when the photo was taken. Hide Caption 2 of 21 Photos: Dawn: Mission to the beginning of the solar system Ceres has more than 130 bright spots , according to NASA. This false color image shows one of spots -- this one in a crater called Occator. Scientists say the substance appears to be a type of magnesium sulfate called hexahydrite. Scientists use false color to help study differences in surface materials, NASA says. Hide Caption 3 of 21 Photos: Dawn: Mission to the beginning of the solar system You get a close-up view of the southern part of Ceres in this image taken on December 10, 2015. You can see craters, troughs and grooves. The spacecraft took these images while it was about 240 miles (385 kilometers) above Ceres, its lowest ever orbit. Dawn will remain at this altitude for the rest of its mission. Hide Caption 4 of 21 Photos: Dawn: Mission to the beginning of the solar system This tall, conical mountain on Ceres was photographed from a distance of 915 miles (1,473 kilometers) by NASA's Dawn spacecraft. The mountain, located in the dwarf planet's southern hemisphere, is 4 miles (6.4 kilometers) high. The photo was taken on August 19, 2015. Hide Caption 5 of 21 Photos: Dawn: Mission to the beginning of the solar system NASA's Dawn probe captured this image of a 3-mile-tall pyramid-shaped structure rising from a plain on the surface of the dwarf planet Ceres. The discovery has further fueled speculation about just what mysteries Ceres may hold. The image was taken on June 6, 2015. Hide Caption 6 of 21 Photos: Dawn: Mission to the beginning of the solar system Dawn gave scientists a big surprise: Ceres has a group of bright spots glowing inside a large crater. The above image is part of a sequence taken by Dawn on May 16, 2015 when the spacecraft was 4,500 miles (7,200 kilometers) away from Ceres. It's the closest view yet of the spots. But what are they? According to the mission's principal investigator, Christopher Russell, scientists have concluded the spots are "due to the reflection of sunlight by highly reflective material on the surface, possibly ice." Hide Caption 7 of 21 Photos: Dawn: Mission to the beginning of the solar system Dawn snapped this image of Ceres on March 1, 2015 just before entering orbit on March 6. The image was taken at a distance of about 30,000 miles (about 48,000 kilometers). Hide Caption 8 of 21 Photos: Dawn: Mission to the beginning of the solar system "Ceres has really surprised us," said Carol Raymond, Dawn's deputy principal investigator. "The first images have produced some really puzzling features." One of the puzzles: two bright white spots that showed up in photographs taken by Dawn on February 19. Hide Caption 9 of 21 Photos: Dawn: Mission to the beginning of the solar system Another puzzling feature on Ceres is a pancake-shaped basin seen in the lower right side of this image. The image was taken on February 19 from a distance of nearly 29,000 miles (47,000 kilometers). The basin is nearly 186 miles (300 kilometers) across. Hide Caption 10 of 21 Photos: Dawn: Mission to the beginning of the solar system This mosaic is made up of images taken by Dawn on February 19 from a distance of nearly 29,000 miles (47,000 kilometers). Hide Caption 11 of 21 Photos: Dawn: Mission to the beginning of the solar system These two views of Ceres were taken on February 12, when Dawn was about 52,000 miles (84,000 kilometers) from Ceres. The images were taken about 10 hours apart. Hide Caption 12 of 21 Photos: Dawn: Mission to the beginning of the solar system Dawn took this picture on approach to Ceres on January 25. It was about 147,000 miles (237,000 kilometers) from the dwarf planet. Hide Caption 13 of 21 Photos: Dawn: Mission to the beginning of the solar system On its way to Ceres, Dawn spent more than 300 days taking photos of the protoplanet Vesta. These three images show Vesta coming into view as the spacecraft approached in July 2011. Hide Caption 14 of 21 Photos: Dawn: Mission to the beginning of the solar system As the spacecraft prepared to leave Vesta behind, scientists created this mosaic of the best views taken during Dawn's stay. Hide Caption 15 of 21 Photos: Dawn: Mission to the beginning of the solar system This is Vesta's Numisia crater. It's about 19 miles (31 kilometers) in diameter. Hide Caption 16 of 21 Photos: Dawn: Mission to the beginning of the solar system This image compares an image of Vesta taken by Dawn as it moved in on the protoplanet with one taken by the Hubble Space Telescope. Before the Dawn mission, the Hubble image was the best available. Hide Caption 17 of 21 Photos: Dawn: Mission to the beginning of the solar system Workers check on the spacecraft, at left, as they prepare to mate it with the upper stage booster rocket on the right. Hide Caption 18 of 21 Photos: Dawn: Mission to the beginning of the solar system Workers at Cape Canaveral prepare Dawn for launch by removing its transportation canister. Dawn was then mated with a Delta II rocket. Hide Caption 19 of 21 Photos: Dawn: Mission to the beginning of the solar system A worker checks the xenon feed system on Dawn. Hide Caption 20 of 21 Photos: Dawn: Mission to the beginning of the solar system Dawn's mission started at 7:34 a.m. ET on September 27, 2007, at Cape Canaveral, Florida. Dawn was launched into space on a Delta II rocket. Hide Caption 21 of 21

Raymond says the brightness is consistent with highly reflective materials such as ice or salts. This might help add more credence to a discovery made in 2014 by the European Space Agency's Herschel infrared space observatory . The telescope detected water vapor around Ceres coming from the same area where the spots are.

"It might be related to that water vapor emission," Raymond said. Herschel's scientists also said their research showed Ceres has an atmosphere. Raymond said her team is keen to confirm that.

Scientists expect to learn more as Dawn is gradually lowered to about 235 miles above the surface of Ceres in December. "The mystery will be solved," she said.

But Ceres seems to have lots of oddities.

"We see many strange features," Raymond said. "We see smooth areas, some areas that are chaotically fractured and we see craters of all sizes."

One of the other things scientists noticed is how round Ceres is. Being round is very important because it is the main characteristic of a planet -- a title that Ceres had, and then lost.

Ceres was demoted to an asteroid because 19th-century astronomers couldn't be sure it was round. But it was bumped up to a dwarf planet when that category was created in 2006.

According to the International Astronomical Union -- the group that came up with the definition -- a dwarf planet is similar to the eight main planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune) except it has a lot of other stuff orbiting with it around the sun.

The IAU recognizes five dwarf planets: Eris, Pluto, Ceres, Makemake and Haumea. Scientists say there could be many more of these small worlds that haven't been discovered.

On Friday, Dawn will make its closest approach yet to Ceres, flying about 25,000 miles from it, said Robert Mase, project manager for the Dawn mission at NASA's Jet Propulsion Laboratory in Pasadena, California . "That's about 10 times closer than the moon is to the Earth," he said.

But the beautiful images coming in from Dawn will stop for a while.

"We're now on the dark side, so we're going to have a blackout for about the next month until we get back over toward the lit side of the body," he said.

But he says the "floodgates will open" when its main science mission starts in April.

Dawn will stay in orbit around Ceres for years, even after its primary mission ends in June 2016. But at some point, it will run out of hydrazine, the fuel used to guide the spacecraft.

Between now and then, mission managers hope Dawn will help solve the mysteries of Ceres and add to our knowledge of how our solar system formed.