Astronomers using Japan's Subaru 8.2-meter telescope, located atop Mauna Kea in Hawaii, have reported discovering a new planet around the star Kappa Andromedae. With all the planets being discovered lately, that wouldn't seem like a big deal, but this is only one of (now) 13 planets classified as 'directly-imaged', and is actually only one of maybe six that have actually been pictured (the rest have only been inferred by seeing the effects they have on objects around them).
"Our team identified a faint object located very close to Kappa Andromedae in January that looks much like other young, massive directly imaged planets but does not look like a star," said University of Toronto post-doc fellow Thayne Currie, who co-authored the study that reported this find, according to Science Codex.
Kappa Andromedae (Kappa And or Κ Andromedae) is the one of the bright stars of the constellation Andromeda. It is a blue-white, B-class 'sub-giant' star, about 2.5 times the size of the Sun, located roughly 168 light years away, and it is a fairly young star, about 30 million years old (a baby compared to our roughly 5-billion year old Sun). It is thought that Κ Andromedae, despite its young age, can no longer sustain hydrogen fusion in its core, but is still able to maintain it in its outer layer, thus keeping its blue-white glow rather than becoming a typical red-giant star.
The newly discovered planet, designated Κappa Andromedae b (Kappa And b or Κ Andromedae b), is estimated at roughly 13 times the mass of Jupiter, and orbits its star at a distance further than Neptune orbits our Sun (so more than 30 times farther than Earth's orbit). This combination or size and distance from its star is what made viewing the planet so easy, compared to others, however, before claiming its status as a planet, the team still had to separate it from any background 'noise'.
"Kappa Andromedae moves fast across the sky so it will appear to change position relative to more distant, background objects," said Currie. "When we re-observed it in July at multiple wavelengths, we saw the faint object again, located at about the same position as it was in January. This indicates that it is bound to the star and not an unrelated background object."
Typically, planets cannot be directly imaged, because the light from the star completely overwhelms any light from the planets that orbit it. In this case, the astronomers looked at K Andromedae with infrared light and used a special filtering technique to pick out the light emitted by the planet's atmosphere.
If an alien race were to be watching our solar system with telescopes, they would likely detect the slight 'wobble' that the orbits of all the planets around the Sun rather than actually see the planets. This Radial Velocity method is how we have been able to find some alien worlds. The star appears to wobble because the exact center of a solar system with planets is actually a bit off from the center of the Sun. Picture it like packing a snowball and then putting a stick through it, but just slightly off from the middle. If you spin the snowball around on the stick, it will have a lop-sided wobble to its spin.
In other cases, we have found the worlds because our point of view happened to coincide with the 'ecliptic' of the star, so that the planets orbiting the star 'transit' between its star and us - called the Transit Method. A transit is similar to an eclipse, but like when Mercury or Venus transits across the Sun, there is absolutely no way that the planet would be large enough to completely block out its parent star's light. All we can see is a slight dip in the star's intensity, but that is enough to tip us off that something passed between the star and us. If it shows up regularly, it is likely a planet orbiting that star.
One other aspect of this new discovery is of importance to astronomers. Up until now, it was assumed that large, powerful stars like Kappa Andromedae were not capable of producing planets, due to their intense radiation possibly disrupting the normal process of planetary formation. Kappa Andromedae b shows that these stars are perfectly capable of producing planets, even massive ones.
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"This planetary system is very different from our own," said Currie. "The star is much more massive than our Sun and Kappa And b is at least 10 times more massive than any planet in the solar system. And, Kappa And b is located further from the star than any of the solar system planets are from the Sun. Because it is generally much harder to form massive planets at large distances from the parent star, Kappa And b could really be a challenge for our theories about how planets form."