Astronomers find elusive target hiding behind dust
Discovery resolves longstanding question

Date:
June 8, 2020
Source:
National Radio Astronomy Observatory
Summary:
Some young, still-forming stars are surrounded by regions of complex
organic molecules called ''hot corinos.'' In some pairs of young
stars forming together as binary pairs, astronomers found a hot
corino around one, but not the other. Guessing that the unseen
one might be obscured by dust, researchers studied such a pair
with the VLA at radio wavelengths that readily pass through dust,
and found the other one.



FULL STORY ========================================================================== Astronomers acting on a hunch have likely resolved a mystery about
young, still-forming stars and regions rich in organic molecules closely surrounding some of them. They used the National Science Foundation's
Karl G. Jansky Very Large Array (VLA) to reveal one such region
that previously had eluded detection, and that revelation answered a longstanding question.


==========================================================================
The regions around the young protostars contain complex organic molecules
that can further combine into prebiotic molecules that are the first steps
on the road to life. The regions, dubbed "hot corinos" by astronomers,
are typically about the size of our Solar System and are much warmer
than their surroundings, though still quite cold by terrestrial standards.

The first hot corino was discovered in 2003, and only about a dozen
have been found so far. Most of these are in binary systems, with two protostars forming simultaneously.

Astronomers have been puzzled by the fact that, in some of these binary systems, they found evidence for a hot corino around one of the protostars
but not the other.

"Since the two stars are forming from the same molecular cloud and
at the same time, it seemed strange that one would be surrounded by
a dense region of complex organic molecules, and the other wouldn't,"
said Cecilia Ceccarelli, of the Institute for Planetary Sciences and Astrophysics at the University of Grenoble (IPAG) in France.

The complex organic molecules were found by detecting specific radio frequencies, called spectral lines, emitted by the molecules. Those characteristic radio frequencies serve as "fingerprints" to identify
the chemicals. The astronomers noted that all the chemicals found in
hot corinos had been found by detecting these "fingerprints" at radio frequencies corresponding to wavelengths of only a few millimeters.

"We know that dust blocks those wavelengths, so we decided to look for
evidence of these chemicals at longer wavelengths that can easily pass
through dust," said Claire Chandler of the National Radio Astronomy Observatory, and principal investigator on the project. "It struck us
that dust might be what was preventing us from detecting the molecules
in one of the twin protostars." The astronomers used the VLA to observe
a pair of protostars called IRAS 4A, in a star-forming region about
1,000 light-years from Earth. They observed the pair at wavelengths of centimeters. At those wavelengths, they sought radio emissions from
methanol, CH3OH (wood alcohol, not for drinking). This was a pair in
which one protostar clearly had a hot corino and the other did not,
as seen using the much shorter wavelengths.

The result confirmed their hunch.

"With the VLA, both protostars showed strong evidence of methanol
surrounding them. This means that both protostars have hot corinos,
and the reason we didn't see the one at shorter wavelengths was because
of dust," said Marta de Simone, a graduate student at IPAG who led the
data analysis for this object.

The astronomers caution that, while both hot corinos now are known to
contain methanol, there still may be some chemical differences between
them. That, they said, can be settled by looking for other molecules at wavelengths not obscured by dust.

"This result tells us that using centimeter radio wavelengths is
necessary to properly study hot corinos," Claudio Codella of Arcetri Astrophysical Observatory in Florence, Italy, said. "In the future,
planned new telescopes such as the next-generation VLA and SKA, will be
very important to understanding these objects."

========================================================================== Story Source: Materials provided by
National_Radio_Astronomy_Observatory. Note: Content may be edited for
style and length.


========================================================================== Journal Reference:
1. Marta De Simone, Cecilia Ceccarelli, Claudio Codella, Brian
E. Svoboda,
Claire Chandler, Mathilde Bouvier, Satoshi Yamamoto, Nami Sakai,
Paola Caselli, Cecile Favre, Laurent Loinard, Bertrand Lefloch,
Hauyu Baobab Liu, Ana Lo'pez-Sepulcre, Jaime E. Pineda, Vianney
Taquet, Leonardo Testi. Hot Corinos Chemical Diversity: Myth
or Reality? The Astrophysical Journal, 2020; 896 (1): L3 DOI:
10.3847/2041-8213/ab8d41 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/06/200608114701.htm

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