LOFAR discovers largest carbon atoms outside our Milky Way

The starburst galaxy M82, the size of the carbon atoms and the observed spectral line. 

Credit: NASA, ESA, and The Hubble Heritage Team (STScI/AURA)

An international team of astronomers under the guidance of graduate student Leah Morabito of Leiden Observatory has for the first time discovered the largest carbon atoms outside our Milky Way with the LOFAR radio telescope.

In the future astronomers will be able to measure how cold and dense the gas around these atoms is that influences star formation and the evolution of a galaxy. The results are published in the journal Astrophysical Journal Letters on October 28th.

"Carbon atoms are about half a million times smaller than the average thickness of a human hair, but they can be a billion times larger in the cold and sparse gas. The outermost electron is then orbiting the nucleus at a much larger distance," explains first author Morabito.

The outermost electron can be captured by an atom that is missing an electron. A spectral line will then be visible in the light spectrum. All spectral lines form the chemical fingerprint of an atom such as carbon.

Astronomers predicted in the 70's that the carbon spectral line would be detectable outside our galaxy. This first observation took 40 years to be made.

The line is hard to detect because it is too faint when the gas that is surrounding the atoms is too warm or too dense.

The cold, sparse gas is present in starburst galaxies, galaxies in which stars form at a high rate. For this reason the carbon spectral line is easier to detect in galaxies of this type.

Most radio telescopes observe at frequencies at which the carbon line can not be detected. Other telescopes are not sensitive enough to detect the spectral lines of the carbon atoms at low frequencies.

The LOFAR radio telescope, that stretches from the northeast of the Netherlands across Europe, is perfect for these kind of observations because of its frequency range and sensitivity.

Co-author Raymond Oonk from Leiden Observatory en ASTRON: "LOFAR is an unique telescope. This telescope opens up a new window on the universe."

The carbon atoms are present in the heart of the starburst galaxy M82, where 10 times more stars are being born in the same period as in our Milky Way.

The cold and sparse gas in this area impacts star formation, and the evolution of M82. "Since the co-discovery of the hydrogen 21-cm line by Dutch, American and Australian astronomers, we have been looking for a way to determine additional properties of the cold gas such as its temperature and density. It is fantastic that we now have found a way thanks to this carbon line.

We can now collect more and better observations, and compare them to predictions from theoretical models," says co-author Huub Röttgering (Leiden Observatory).

More information: "Discovery of Carbon Radio Recombination Lines in M82," Leah K. Morabito et al., Astrophysical Journal Letters, 28 October 2014 DOI: 10.1088/2041-8205/795/2/L33 . http://arxiv.org/abs/1410.1544

Arecibo observatory: Two New Programs Launching to Listen for Aliens

The 305-meter telescope at Arecibo Observatory is just one of a collection that SETI will use to search nearby stars for electronic signals that could indicate intelligent life. 

If such a civilization was utilizing a similar dish to image exoplanets, SETI's team should be able to detect it.

Credit: Arecibo Observatory

SETI is stepping up its search for alien lifeforms on far off worlds.

The Search for Extraterrestrial Intelligence (SETI) program recently announced two new methods to search for signals that could come from life on other planets.

In the Panchromatic SETI project, multiple telescopes will scan a variety of wavelengths from 30 stars near the sun; the project will look for powerful signals beamed into space, potentially by intelligent extraterrestrials.

SETI is also launching an interplanetary eavesdropping program that is expected to search for messages beamed between planets in a single system.

"If we are polluting space, perhaps other extraterrestrials are leaking signals," Dan Werthimer, director of the Berkley SETI Research Center, told an audience during the Smithsonian Magazine's "The Future is Here" Festival in May. "Maybe they're sending something our way."

'Everything we've got'
Since humans made their first FM radio and television transmissions, signals from Earth have been spilling out into space, announcing the presence of intelligent life to any group that might be searching for it.

According to Werthimer, signals from the 1950s television show "I Love Lucy" have reached thousands of stars, while the nearest suns have already enjoyed the "The Simpsons."

If Earth has unintentionally leaked signs of its presence, other alien civilizations may have done the same thing.

SETI's new Panchromatic project will utilize a variety of telescopes covering a range of frequencies to scour the nearest stars.

"We're going to throw everything we've got at it," Werthimer added.

The panchromatic project will examine a sample of the 30 stars that lie within 5 parsecs (16 light-years) from the sun. The list includes 13 single stars, seven binary systems and one triple system.

Most of the stars are smaller than the sun, but the project will also examine two white dwarfs and one moderately evolved F star. No confirmed exoplanets have been found around any of the stars.

By setting distance as the criteria, the SETI team hopes to alleviate any bias that might otherwise result from focusing on systems similar to that of Earth. The team selected stars for study based only on how far they lie from the sun.

According to SETI-Berkeley's Andrew Siemion, chief scientist of the eavesdropping project, the search will also probe a diverse stellar population already well studied at many wavelengths.

"In the event of a non-detection, these attributes of the sample will allow us to place strong and broadly applicable limits on the presence of technology," Siemion told Space.com via email.

Observations from the Low Frequency Array (LOFAR) telescope in Europe and the Green Bank Telescope (GBT) in West Virginia will begin over the summer and fall of 2014.

Instrument development and commissioning is still in progress for the Infrared Spatial Interferometer (ISI) at Mount Wilson Observatory and the Nickel Telescope at Lick Observatory, both in California.

But according to Siemion, the pair should be ready at about the same time. The Nickel Telescope will conduct the first-ever SETI observations done in the near-infrared.