How Will Aliens Find Us?

Trying to keep a low profile, to prevent the aliens from invading? Bad news. Life has actually been broadcasting our existence to the Universe for hundreds of millions of years.

Have you heard these crazy plans to send signals out into deep space? What if evil aliens receive them, come steal our water, enslave, eat, and use us as guinea pigs for their exotic probulators. How we could stop these madmen from announcing our presence to the galaxy? A petition on whitehouse.gov? An all caps Facebook group? An all pusheen protest? Somebody call Reddit, they’ll know what to do.

If this is a worry for you and your friends, I’ve got bad news, or possibly good news depending on which side you come down on. We’ve already been broadcasting our existence for hundreds of millions of years. If aliens wanted to know we were here, all they needed to do was look through their telescopes.

We’re in a golden age of extrasolar planet discovery, recently crossing the thousand-planets-mark thanks to Kepler and other space telescopes. With all these amazing planetary candidates, our next challenge will be to study the atmospheres of these planets, searching for evidence of life. There are chemicals which are naturally occurring, like water and carbon dioxide, and there are substances that can only be present if some source is replenishing them. Methane, for example, would only last only few hundred years in the atmosphere if it wasn’t for farting cows and colonies of bacteria eating dead things.

If we see methane or oxygen in the atmosphere of an extrasolar planet, we’ll have a good idea there’s life there. And if we see the byproducts of an industrial civilization, like air pollution, we can pinpoint exactly where they are in their technical development. It will work for us, and that means it would work for aliens.

For the first few billion years, oxygen was toxic. But then cyanobacteria evolved photosynthesis and figured out how to work with oxygen more than 2.4 billion years ago. This is known as the Great Oxidation Event.

For the first billion years, all this biologically generated oxygen was absorbed by the oceans and the rocks. Once those oxygen sinks filled up, oxygen began accumulating in the atmosphere. By 500 million years ago, there was enough oxygen in the atmosphere to support the kind of breathing we do today. And this much oxygen would have been obvious to the aliens. They would have known that life had evolved here on Earth, and they could have sent out their berserker spaceships to steal our water and made us watch while they ate all our small rodents.

If the aliens waited, we would have given them more signs. The Industrial Revolution began in the mid 1700’s. And this time, it was humans that filled the atmosphere with the pollution of our industrial processes. Again, aliens watching the planet with their space telescopes would know the moment we became a technological civilization.

The innermost antennae along the north arm of the Very Large Array, superimposed upon a false-color representation of a radio (red) and optical (blue) image of the radio galaxy 3C31. Image courtesy of NRAO/AUI
The innermost antennae along the north arm of the Very Large Array, superimposed upon a false-color representation of a radio (red) and optical (blue) image of the radio galaxy 3C31. Image courtesy of NRAO/AUI

In the 20th century, we harnessed the power of radio transmissions, and began sending our messages out into space. For about a hundred years now, our transmissions have been expanding into a bubble of space. And so, any aliens listening within this expanding sphere of space might have a chance of hearing us. They know we’re here, and they know some of us really like Ke$ha.

And finally, for the last few decades, a few groups have tried broadcasting messages using our powerful radio telescopes directly at other stars. These messages haven’t gotten very far, but I honestly wouldn’t worry. Life itself gave away our position hundreds of millions of years ago. And life will help us find other civilizations, if they’re out there.

What do you think? Should we turn out the lights and pretend like we’re not home or keep on actively broadcasting our presence to the Universe? Tell us what you think we should do in the comments below.

New Pulsar “Clocks” Will Aid Gravitational Wave Detection

This illustration shows a pulsar’s magnetic field (blue) creates narrow beams of radiation (magenta). Image credit: NASA

How do you detect a ripple in space-time itself? Well, you need hundreds of precision clocks distributed throughout the galaxy, and the Fermi gamma ray telescope has given astronomers a new way to find them.

The “clocks” in question are actually millisecond pulsars – city-sized, sun-massed stars of ultradense matter that spin hundreds of times per second. Due to their powerful magnetic fields, pulsars emit most of their radiation in tightly focused beams, much like a lighthouse. Each spin of the pulsar corresponds to a “pulse” of radiation detectable from Earth. The rate at which millisecond pulsars pulse is extremely stable, so they serve as some of the most reliable clocks in the universe.

Astronomers watch for the slightest variations in the timing of millisecond pulsars which might suggest that space-time near the pulsar is being distorted by the passage of a gravitational wave. The problem is, to make a reliable measurement requires hundreds of pulsars, and until recently they have been extremely difficult to find.

“We’ve probably found far less than one percent of the millisecond pulsars in the Milky Way Galaxy,” said Scott Ransom of the National Radio Astronomy Observatory (NRAO).

Data from the Fermi gamma-ray space telescope, which started collecting data in 2008, have changed the way millisecond pulsars are detected. The Fermi telescope has identified hundreds of gamma-ray sources in the Milky Way. Gamma rays are high-energy photons, and they are produced near exotic objects, including millisecond pulsars.

“The data from Fermi were like a buried-treasure map,” Ransom said. “Using our radio telescopes to study the objects located by Fermi, we found 17 millisecond pulsars in three months. Large-scale searches had taken 10-15 years to find that many.”

Ransom and collaborator Mallory Roberts of Eureka Scientific used the National Science Foundation’s Robert C. Byrd Green Bank Telescope (GBT) to find eight of the 17 new pulsars.

Right now astronomers have only barely enough millisecond pulsars to make a convincing gravitational wave detection, but with Fermi to help identify more pulsars, the odds of detecting these ripples in space-time are steadily increasing.

Ransom and Roberts announced their discoveries today at the American Astronomical Society’s meeting in Washington, DC.

(NRAO Press Release)

35 Radio Observatories Link to Break Record

Ever wondered what the largest telescope on the Earth is? Well, this coming Wednesday and Thursday of this week, the largest telescope ever assembled here will take observations for a whole day. How big is the telescope? About the size of the whole Earth! 35 radio telescopes on 7 continents will link together for one whole day in an effort to observe distant quasars as part of an initiative to improve the reference frame that scientists use to measure positions in the sky.

Radio telescopes in Asia, Australia, Europe, North America, South America, Antarctica, and in the Pacific will all be linked together to measure the same 243 quasars over a 24-hour period. Quasars are galaxies that have a supermassive black hole at the center, which has strong emissions in the radio spectrum. The quasars being monitored are so far away from the Earth that they appear to be motionless in the sky. This makes them a perfect candidate for setting up a grid in the sky to use as a frame of reference, against which the positions of other objects can be determined.

This monitoring session comes out of a meeting of the International Astronomical Union in August, during which it was decided to start using a set of 295 quasars as a celestial reference frame starting January 1st, 2010. This is not a new reference frame to be used by astronomers – the current one was adopted in 1998 –  but an important update to the existing reference frame, the International Celestial Reference Frame.

The session, called the Very Large Astrometry Session is coordinated by the International VLBI Service for Geodesy and Astrometry. Several of the participating observatories will have live webcams running during the event (check for the observatory in your language!), and a public outreach page on the event,  hosted by the Bordeaux Observatory, can be found here. The public outreach page will post images as they are taken during the session, with information about observation coordinates.

Radio telescopes like the Very Long Base Array in the United States already link together observatories that are far apart to take observations. This technique is called very long baseline radio interferometry (VLBI), and allows for the use of smaller telescopes that are distant from one another to be linked together and have the same angular resolution as if they were one larger telescope. Doing these observations all in one go will reduce some of the errors that occur when disparate observatories take images at different times.

The previous record for radio observatories linked together to create a larger telescope for one monitoring session is 23. That means that this observing session will beat that record by a whopping 12 additional observatories. Even with this unprecedented amount of observatories monitoring the quasars, there will be a few gaps in the sky, mostly in the Southern hemisphere. Only 243 of the total 295 quasars in the reference frame will be observed this week, though that will break another record for the amount of objects observed in one session using this method. The image below depicts the locations of the participating observatories.A map of the observatories participating in the Very Large Astrometry Session. Check your local listings for live webcam images! Image Credit:IYA09

By taking data on the 243 selected quasars, astronomers will be able to more accurately pinpoint objects in the sky in all wavelengths, and gather more precise data. For instance, many objects of scientific interest are monitored by separate telescopes operating in the visible, radio, x-ray and infrared wavelengths. Having a more accurate frame of reference to tell these different telescopes where to point in the sky will improve the ability of the different telescopes to gather information from the same place in space.

Source: NRAO, IVS

Arecibo Observatory

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Named after the nearby city in Puerto Rico, the Arecibo Observatory (or Arecibo Radio Telescope) is the largest single-aperture (radio) telescope ever built, 305 m in diameter.

Taking advantage of a karst sinkhole, Cornell University built a spherical reflector out of wire mesh, with receivers at the focus suspended by 18 steel cables strung from three concrete towers on the rim. It took three years to build, and was completed in 1963. Since then it has been upgraded several times; for example, in 1974 perforated aluminum panels replaced the wire mesh, and a Gregorian reflector system added to the receiver mechanism in 1997. Among other things, these upgrades have extended the range of radio wavelengths Arecibo can operate at, both as a radio telescope and for radar astronomy.

Such a visually interesting piece of scientific hi-tech has lead to Arecibo playing a role in many movies and TV shows, from James Bond’s Golden Eye to Contact to X-Files.

Everyone knows about [email protected], right? Well, it’s receivers on Arecibo that supply the data which the millions of PCs crunch!

Arecibo has played a key role in many astronomical discoveries, from the rotation period of Mercury (a radar astronomy application, in 1964), to the pulses of the Crab Nebula (1968), to studies of pulsars by Hulse and Taylor (1974) that lead to their Nobel Prize (1993), and to direct imaging of asteroids (another radar astronomy application, first done in 1989).

Due to budget cutbacks and changes in research priorities, the future of Arecibo is uncertain (most of its funding comes from the National Science Foundation); maybe you can find a way to save it?

Here’s the official Arecibo Observatory website; ALFA is a current large-scale astronomical survey being done at Arecibo, in case you don’t already know about [email protected], and click here to read more about planetary radar.

Calling All Amateur Astronomers: Help Comb Through Arecibo Data for Gems, Arecibo Spots Triple Asteroid, Arecibo Gets an Upgrade: just three of the many Universe Today stories featuring the Arecibo Observatory!

Some of the ways Arecibo contributes to astronomy are covered in Astronomy Casts The Rise of Supertelescopes, and Across the Electromagnetic Spectrum.

Source: National Astronomy and Ionosphere Center: Arecibo Observatory