Astronomers have detected our “grotesque” twin: A planetary system arranged much like our own solar system, a new study says.
Dubbed GJ676A, the system has two rocky planets orbiting close to its host star, and two gas giants orbiting far away. This means the system is arranged like our system—though in GJ676A, everything is much larger.
For instance, the smallest rocky planet in GJ676A is at least four times the mass of Earth, while the largest gas giant is five times the size of Jupiter.
Other multiple-planet systems have been discovered, such as HD10180, which has been called the richest exoplanetary find ever because of the seven to nine planets orbiting its host star.
But HD10180’s planets are all gas giants in relatively close orbits, while GJ676A has both rocky and gas planets—and its “Neptune-like” planet takes 4,000 days to make one orbit.
The long orbits of GJ676A’s gas giants and the short orbits of its close-in, extremely hot super Earths are what led the astronomers to dub GJ676A our solar system’s twin.
Source: National Geographic News – Solar System’s “Grotesque” Twin Found
How big is Jupiter’s moon Io?
The most volcanic body in the Solar System, Io (usually pronounced “EYE-oh”) is 3,600 kilometers in diameter, about the size of planet Earth’s Moon.
Gliding past Jupiter at the turn of the millennium, the Cassini spacecraft captured this awe inspiring view of active Io with the largest gas giant as a backdrop, offering a stunning demonstration of the ruling planet’s relative size.
Io hurtles around its orbit once every 42 hours at a distance of 420,000 kilometers or so from the center of Jupiter. That puts Io nearly 350,000 kilometers above Jupiter’s cloud tops, roughly equivalent to the distance between Earth and Moon.
The Cassini spacecraft itself was about 10 million kilometers from Jupiter when recording the image data.
Does the Moon rotate?
And if the Moon rotates, why do we alway see the same side – it never seems to change.
Well, the Moon does rotate. In fact, the Moon takes 27.3 days to turn once on its axis. But the Moon also takes 27.3 days to complete one orbit around the Earth. Because the Moon’s rotation time is exactly the same amount of time it takes to complete an orbit, it always presents the same face to the Earth, and one face away (the Dark Side).
Because it only presents one face to the Earth, astronomers say that the Moon is tidally locked to the Earth. Although the Moon looks like a perfectly smooth ball, it has slight differences in the shape of its gravity field. A long time ago, the Moon did rotate. But each time it turned, the Earth’s gravity tugged at it, slowing down its rotation until it only presented one face to the Earth. At that point, the Moon was tidally locked, and from our perspective, it doesn’t seem to rotate.
Many other moons in the Solar System are also tidally locked to their planet. In fact, most of Jupiter’s large moons are tidally locked.
via Universe Today