18 September 2014, 06:00 AM ET
Experts will debate different definitions of the term "planet" during a live webcast tonight at 7:30 p.m. EDT. Watch it live here on Space.com.
26 August 2014, 06:00 AM ET
NASA's Voyager 2 spacecraft made the first-ever flyby of Neptune on Aug. 25, 1989, zipping by the planet and its moon Triton in quick succession. The historic encounter gave a face to two worlds that until that time had dwelt in depth and shadow.
25 August 2014, 03:37 PM ET
New Horizons — which is scheduled to zoom through the Pluto system on July 14, 2015 — passed Neptune's orbit today, 25 years to the day after NASA's Voyager 2 probe executed the first-ever flyby of faraway Neptune and its icy moon Triton.
22 August 2014, 06:02 AM ET
The new map, made using photos taken by NASA's Voyager 2 probe in 1989, has also been turned into a movie reconstructing the spacecraft's historic Triton encounter — the only time a spacecraft has ever visited the Neptune system.
11 August 2014, 04:35 PM ET
The New Horizons probe used its onboard telescope to record a video of Charon orbiting Pluto. The movie is composed of 12 individual images taken July 19-24 — one year before the spacecraft's flyby of the distant dwarf planet.
11 August 2014, 11:17 AM ET
NASA’s New Horizons snapped the big dwarf planet and its nearby moon for 5 days (July 19th-24th, 2014). Charon is 750 - 753 miles diameter, the largest known compared to the size of its host planet. Some consider Pluto-Charon a binary planet.
22 July 2014, 05:50 PM ET
NASA's New Horizons' mission, which blasted off in 2006, will become the first spacecraft to orbit Pluto in July 2015. The flyby will give researchers their first good look at the distant, frigid dwarf planet.
15 July 2014, 08:00 AM ET
NASA's New Horizons mission will be within 6,214 miles (10,000 km) from the surface of the dwarf planet on July 14, 2015. Similar cameras on a probe that close to Earth would be able to resolve individual building and their shapes.
02 July 2014, 10:00 AM ET
Scientists are using the powerful Hubble Space Telescope to figure out where to send NASA's Pluto-bound New Horizons probe next — and they've already found some promising leads.
01 July 2014, 03:25 PM ET
Pluto reaches opposition and can be seen with a medium-sized telescope and dark skies. Dwarf planet Ceres and asteroid Vesta will be quite close to one another on the night sky. But each is a tough target.
25 June 2014, 07:22 AM ET
Using vintage telescope data, scientists have attempted to map Pluto's icy depths before a NASA spacecraft reaches the distant dwarf planet in 2015.
23 June 2014, 04:44 PM ET
When NASA's New Horizons spacecraft leaves the solar system, it will carry with it a digital message from people on Earth.
16 June 2014, 03:27 PM ET
Scientists will use the space agency's Hubble Space Telescope to search for another faraway object that could be visited by the New Horizons mission after the Pluto encounter, which is scheduled to take place in July 2015.
16 June 2014, 07:26 AM ET
A NASA spacecraft arriving in the Pluto system next year could help scientists figure out if the dwarf planet's largest moon Charon might have once harbored a subsurface ocean of liquid water.
10 June 2014, 03:43 PM ET
Alan Stern, the principal investigator of NASA's New Horizons mission to Pluto, has challenged astrophysicist Neil deGrasse Tyson to just such a debate, NBCNews reported last week.
10 June 2014, 12:00 PM ET
The world will get its first good look at mysterious Pluto a little more than a year from now, possibly reigniting the debate over the object's planetary status. NASA's New Horizons probe will make a historic flyby of Pluto in July 2015.
09 May 2014, 03:11 AM ET
Quaoar is a planetoid that lies in the Kuiper Belt, a region of space beyond Pluto that is filled with icy bodies.
30 April 2014, 02:22 AM ET
Sedna is a dwarf planet candidate that is one of the most distant bodies found in our solar system.
14 April 2014, 06:31 PM ET
Many attendees of the Pluto Science Conference in July 2013 referenced it as a planet. NASA's New Horizon mission, that will deliver the first reconnaissance of Pluto in 2015, will help resolve the long debate.
27 March 2014, 10:00 AM ET
A new analysis of data collected by NASA's WISE spacecraft revealed no sign of the mysterious Planet X hypothesized to exist in the outer solar system. But scientists are keeping up the search for a planet or dim star far from the sun.
26 March 2014, 02:01 PM ET
See images and photos of the icy world 2012 VP113, a potential dwarf planet at the extreme edge of the solar system, in this Space.com gallery.
26 March 2014, 02:00 PM ET
The newfound object, called 2012 VP113, joins the dwarf planet Sedna as a resident of a far-flung region called the "inner Oort Cloud." Further, 2012 VP113 and Sedna may have been pulled into their odd orbits by a big, undiscovered planet.
14 January 2014, 10:08 AM ET
NASA's New Horizon spacecraft left Earth in 2006 and is quickly approaching its fly-by of the icy dwarf planet and its moons. Its closest approach will occur on July 14th, 2015.
09 October 2013, 02:35 PM ET
The impact that formed Pluto’s largest moon, Charon, likely led to the formation and destruction of numerous smaller satellites shortly thereafter, eventually culminating in the strange configuration seen today, researchers said.
11 July 2013, 11:00 AM ET
See images and illustrations of the dwarf planet Pluto and its three — now FIVE! — moons.
03 July 2013, 07:00 AM ET
Some Pluto surface features may end up bearing the names of Captain Kirk and Mr. Spock.
02 July 2013, 12:00 PM ET
Pluto's two smallest moons are now named Kerberos and Styx.
26 April 2013, 04:32 PM ET
Lowell Observatory is best known for the discovery of Pluto. Astronomers there have also studied Halley's Comet and discovered an exoplanet in 2007.
24 April 2013, 02:37 PM ET
The names still have to be accepted by the International Astronomical Union.
19 March 2013, 07:00 AM ET
A look at the robotic spacecraft currently sending data home from beyond Earth orbit.
15 March 2013, 01:46 PM ET
The Keck Observatory will be looking for more donations to counteract a freeze on federal grant spending.
13 March 2013, 06:30 AM ET
One to 10 tiny, undiscovered moons could be circling Pluto, according to a new simulation.
27 February 2013, 03:29 PM ET
This space wallpaper shows an artist’s impression of the surface of the distant dwarf planet Makemake.
15 February 2013, 03:05 PM ET
Kansas farm boy Clyde Tombaugh looked to the stars and found a new planet.
11 February 2013, 09:59 AM ET
Vote online to name two of Pluto's moons.
03 January 2013, 06:00 AM ET
A brief rundown of the intrepid spacecraft currently sending data home from beyond Earth orbit.