Watch live NASA coverage of spacecraft buzzing Pluto on Tuesday

The New Horizons probe of NASA also settled one of the most basic questions about Pluto – its size. As NASA awaits more results, they’ve already released a sneak-peak shot of Pluto taken by New Horizons on Instagram. “You can use a “live” mode to see what New Horizons is doing right now, or preview the flyby of the Pluto System”. “It would be a great disappointment of New Horizons is lost”, Stern added. It doesn’t sound much of a reward for all the effort of designing and building the spacecraft – but for planetary scientists, the data coming back from the mission is pure gold.

After the spacecraft went quiet several members of the New Horizons team remained in the operations room anyway. However, we didn’t even know how big poor Pluto was, until now. The closet any spacecraft has been in history.

But spaceflight is a risky business, and Stern described the Kuiper Belt, where Pluto resides on the edge of the solar system, as “more or less a shooting gallery, with lots of small primordial comets and other things much smaller than Pluto”.

Those were the waning days of the Voyager spacecrafts’ encounters with Jupiter, Saturn, Uranus, and Neptune, and scientists were hungry for the next world in the lineup.

But with Pluto, the dynamics are different. It shows the planet in its most detailed resolution to date, 4 kilometers per pixel, and indicates possible tectonic activity, snowfall and varying terrain on Pluto’s surface, Stern said. It weighed 1,054 pounds (478 kilograms) at launch.

Since Eris’ discovery in 2005, it was most often regarded as the larger – one reason that Pluto got downgraded from being regarded as a “planet”. But the two look very different, according to fuzzy images that New Horizons took from millions of miles away.

For the plutophiles among us, it will be cause to celebrate, especially for those gathered at the operations center at Johns Hopkins University’s Applied Physics Laboratory in Laurel, Maryland.

As astro-boffins prepare themselves for the arrival of data from New Horizons’ nearest approach in its Pluto fly-by, the little probe has already revised opinion about how big/small the planet/dwarf planet really is.

Over the weekend, scientists discovered that it is a bit bigger than they expected. It’s about 50 miles bigger, for a grand total of 1,473 miles in diameter.

[Everything you need to know about Tuesday’s Pluto encounter].

But the New Horizons team is not saying what the new data might mean until they’ve been able to study it.

During that time, powerful radio signals from NASA’s Deep Space Network will be sent through Pluto’s atmosphere and, if all goes well, into New Horizons’ receiver for later analysis.

There is, however, a slight risk of calamity.

Measuring Pluto’s size has been a decades-long challenge due to complicating factors from its atmosphere. It culminated an unprecedented journey spanning 9½ years and 3 billion miles. It is expected to arrive at 6:02 p.m.

Pictures beamed back to Earth from Pluto should finally be revealed to the world tomorrow, giving us an up-close glimpse of the surface of Pluto, the planet on the outskirts of our solar system. New Horizons will be too busy gathering data to touch base with mission control immediately, and the signal will take hours to get all the way back to Earth. Scientists now think that there are thousands of other icy objects beyond Pluto in a region known as the Kuiper Belt.

Decisions about extending missions aren’t made until the primary mission is complete, but in the fall of 2014, scientists identified three additional bodies that would be worth a visit. We understand Mars well, we’ve seen the rings of Saturn up close, and we’ve explored some fascinating worlds like Titan and Europa.

It was downgraded from a planet to a dwarf planet in 2006 and is thought to contain important clues about the origins of the solar system.