Last night, I started getting emails and tweets asking about a possible detection of a radio signal coming from two of the newly-discovered planets orbiting other stars.
Cutting to the chase: yes, a signal has been seen, but no, it’s not coming from some alien civilization. It’s almost certainly something much closer, like a satellite interfering with the observation.
So what’s the deal?
You talkin’ to me?
The Search For Extraterrestrial Intelligence (SETI) is a
privately-funded group of scientists and engineers who are trying* an ongoing effort to figure out ways to detect signals from space that could be coming from other intelligences: aliens. They focus (haha) mostly on radio signals, since it’s very easy to send radio waves across the vast light years separating stars, it’s easy to detect radio waves (so primitive life like us can pick up the call), and it’s easy to encode information that way. Heck, we’ve been broadcasting coded radio waves for over a century now!
Currently, no unambiguous alien "Hello there!" has been detected. The sky is big, there are a lot of stars out there, and the radio spectrum is really wide, too. Think of how many radio stations there are on a typical radio dial from top to bottom; now divide that up into a billion tiny slices and try to find the one that’s playing the song you want to hear. It’s something of a painstaking process.
Recently, astronomers came up with a clever idea: the Kepler space mission is finding tons of planets orbiting other stars. It may find an Earth-like planet orbiting a Sun-like star at just the right distance to allow life to evolve, though no such planet has been found just yet. Still, why look all over the sky when we know where there are lots of planets?
Can’t stop the signal
So a search targeting those stars with planets has been set up. And that’s where our story picks up: using the ginormous 100 meter Green Bank Telescope, astronomers from UC Berkeley found what look like artificial signals when observing two different stars. The stars are called Kepler Object of Interest 812 and 817 (or just KOI 812 and 817 for short). Here’s an example of a signal they found from KOI 817:
Some 60 million light years from Earth is the monster galaxy M87. It’s a massive elliptical galaxy, one of the largest such in the nearby Universe… if you count 600 quintillion kilometers away as "nearby".
And when it comes to the Universe, I do.
It sits in the center of the Virgo cluster, a collection of roughly 1500 galaxies all bound to each other by gravity. At the heart of M87 is one of the biggest black holes ever seen: something like 6 billion times the mass of the Sun (the Milky Way has one as well, but it’s a paltry 4 million solar masses). It’s called a supermassive black hole, and it’s active. That means it’s a sloppy eater: as matter falls in to the hole, it piles up outside and forms a giant disk, which gets hot… millions of degrees hot. The tremendous heat and other titanic forces join up to blast away a huge amount of the otherwise incoming material. It’s not a nice, neat process, and when a black hole on that scale lets out a belch, it’s felt for hundreds of trillions of kilometers… as you can see in this image:
[Click to supermassivize.]
This is a composite of two images, one taken in radio wavelengths by the Very Large Array (in red) and the other in X-rays by the orbiting Chandra Observatory (in blue). The X-rays are being emitted by gas blasting away from the black hole, heated up by the disk and the magnetic fields affiliated with the hole itself. The radio waves are from gas that previously existed outside and farther away from the black hole, which is being slammed into, stirred up, and swept away by the outflowing gas.