Posts tagged exoplanets
The two planets circling Kepler-36, a sun-like star in its senior years, are as different as Earth and Neptune. But unlike the hundreds of millions of miles that separate our solar system’s rocky worlds from its gas giants, Kepler-36’s brood come as close as 1.2 million miles (1.9 million kilometers, or 0.01 AU) from one another — about five times the distance between Earth and the moon.
“When they’re at their closest, it presents a spectacular view in the sky,” astronomer Josh Carter, with the Harvard-Smithsonian Center for Astrophysics, told Discovery News.
Image:David Aguilar, Harvard-Smithsonian Center for Astrophysics
What do you think? Is the term “super-Earth” misleading? Space blogger Amy Shira Teitel investigates a recent exoplanet discovery and concludes that being “super” is a matter of perspective.
Gravitational Tug of ‘Invisible’ Exoplanet Discovered
Although NASA’s Kepler space telescope can only detect exoplanets that pass in front of their stars, it seems the gravitational pull of non-transiting worlds can also be detected.
The biggest challenge facing astronomers hunting for a bona fide “Earth-like” exoplanet is: where do you look? In a galaxy stuffed with hundreds of billions of stars, it’s difficult to narrow the search.
Naturally, a key motivational factor behind planet-hunting missions (like NASA’s Kepler space telescope) is to hunt for small rocky worlds — not too dissimilar to Earth — that may play host to life as we know it.
So, Kepler astronomers have focused their search on sun-like stars in the hope of detecting Earth-sized exoplanets orbiting at a similar distance our planet orbits the sun — a “sweet spot” (or “habitable zone”) where the temperature may be just right for liquid water to exist on the surface. In our experience, where there’s liquid water, there’s life.
Image: A stellar nursery inside the Orion Nebula. Credit: NASA/JPL/Caltech
n 2010, a star 127 light-years away stunned the world — it had become the largest star system beyond our own, playing host to five, possibly seven, alien worlds. Now, the star (called HD 10180) is back in the headlines; it may actually have nine exoplanets orbiting it.
Interestingly, HD 10180 is a yellow dwarf star very much like the sun, so this discovery has drawn many parallels with our own Solar System. It is a multi-planetary system surrounding a sun-like star.
It is believed that one of HD 10180’s exoplanets is small — although astronomers only know the planets’ masses, not their physical size or composition. The smallest world weighs-in at 1.4 times the mass of Earth, making it a “super-Earth.”
Most Ancient, ‘Impossible’ Alien Worlds Discovered
As we discover more worlds orbiting distant stars, we are finding that “conventional thinking” doesn’t seem to apply to the growing menagerie of exoplanets. And this most recent exoplanetary discovery is no different.
In fact, the two exoplanets found to be orbiting a star 375 light-years away shouldn’t exist at all.
The two gas giant planets were spotted during a survey of “metal poor” stars. When focusing on a star called HIP 11952, researchers from the Max-Planck Institute for Astronomy in Heidelberg, Germany, discovered a slight wobble in the star’s position.
The wobble is being caused by the gravitational tug of two exoplanets — one is nearly the size of Jupiter and orbits the star every seven days, the other is approximately three-times the size of Jupiter and has an orbital period of 290 days.
Image credit: Timotheos Samartzides
The number of known multi-planetary star systems has just tripled. What’s more, the Kepler space telescope science team has just announced that they have doubled the number of confirmed exoplanetary sightings made by the observatory.
“Prior to the Kepler mission, we knew of perhaps 500 exoplanets across the whole sky,” said Doug Hudgins, Kepler program scientist at NASA Headquarters in Washington, D.C. “Now, in just two years staring at a patch of sky not much bigger than your fist, Kepler has discovered more than 60 planets and more than 2,300 planet candidates. This tells us that our galaxy is positively loaded with planets of all sizes and orbits.”
The exoplanet in question is 55 Cancri e and it orbits a star 40 light-years from Earth. It is also very well known to astronomers — having been detected in 2004.
In the last few years, our understanding as to the nature of 55 Cancri e has evolved and due to its rapid orbit (of only 18 hours) — which takes it across the star’s disk slightly dimming some starlight from view — this world is easy to observe.
Astronomers have also worked out its mass and physical size arriving at the conclusion that 55 Cancri e belongs to the rocky “super-Earth” class of exoplanets. It is nearly nine-times the mass of Earth and twice its radius.