Talk about a cosmic outsider! A newfound exoplanet sets the record for orbital distance from a host star.
Dubbed GU Psc b, the giant planet is on an orbit more than 2,000 times farther away from its star than the one the Earth circles around the sun. You wouldn’t see many birthdays on this exotic world, since it takes about 80,000 years to make a single trip around its star!
For comparison, the farthest large planet in our solar system, Neptune, orbits at only 30 times the Earth-sun distance. Its “year” is just shy of 165 Earth-years.
The newly discovered exoplanet lies some 155 light-years from Earth in the constellation Pisces, and it is huge, estimated at about 11 times the mass of Jupiter.
Current theories, however, cannot explain how a large planet like GU Psc b could form at such a great distance from its star, so the discovery may refine our understanding of how planets are born.
The international discovery team, led by Marie-Ève Naud of the Université de Montréal in Quebec, found and directly imaged the planet by combining observations from observatories in Canada, Hawaii, and Chile. The announcement made this week, published in the Astrophysical Journal, comes hot on the heels of the release of the best direct image ever taken of an exoplanet.
See for Yourself
While GU Psc b is an extremely faint 14th-magnitude star, visible only through the largest of backyard telescopes, we can look at a much brighter and closer analogue—the giant Neptune. Neptune is the most distant planet in our solar system, leaving aside comet-belt dwarf planets such as Pluto and Eris.
Over the next few weeks Neptune will be some 2.8 billion miles (4.5 billion kilometers) away from Earth—so distant that reflected sunlight off its icy cloud tops takes nearly four hours to reach us. At this distance the planet’s 33,000-mile (53,000-kilometer) diameter is reduced to a mere 2.3 arc-seconds wide (compared to much closer and bigger Jupiter’s 40 arc-seconds), but it still shines at 7.9 magnitude—making it invisible to the naked eye but an easy target for binoculars.
The key in finding this denizen of the outer solar system is to know when and where to look.
It’s quite easy to find the general vicinity of Neptune, which lies among the starry background of the southern constellation Aquarius. The hard part is pinpointing which of those tiny points of light is the actual planet.
The planet rises above the eastern horizon after 3 a.m. local time and climbs higher until dawn in the Northern Hemisphere. For those with detailed star charts and GoTo scopes, its coordinate is RA 22h 37.2m, Dec -9º 28.9′.
Start your hunt with a visible star low in the sky in Capricornus called Deneb Algiedi. Draw an imaginary line toward the left until hitting the next faintly visible star, Hydor (Lambda Aquarii) in Aquarius. Neptune is about one-quarter of the way from Hydor to Deneb Algiedi. The separation between Hydor and the planet is approximately 4 degrees, slightly less than the width of your three fingers at an outstretched arm’s length.
I recommend first trying to spot Neptune with binoculars, using the above sky chart for reference.
The best way to confirm your sighting is through a telescope. Center the object in the field of view and insert a high-power eyepiece. If the object appears as a small blue-gray disk and not a point of light, then you’ve bagged Neptune!
While there isn’t much Neptunian detail even through a large telescope, the real satisfaction comes from knowing you are actually watching the most distant major planet in the solar system with your own eyes.