Astronomers at the UA have observed neon, a gas best known for its use in colorful electric signs, in disk-shaped clouds of dust and gas that form around young sun-like stars.

It is in such clouds, called “”circumstellar disks,”” that new planets are formed, according to an article published in the July edition of the Astrophysical Journal.

Researchers used the

Spitzer Space Telescope to look at the disks around 328 young sun-like stars and found that four contained small amounts of neon. The study was conducted as a part of the Formation and Evolution of Planetary Systems (FEPS) Spitzer legacy program, said astronomy professor Michael Meyer.

Circumstellar disks also play an important role in the ability of terrestrial planets, like Earth, to sustain life. Planets that do not have circular orbits, but instead have oblong orbits, spend some of their time very close to their parent star and some of their time farther away.

As the distance between a planet and its star changes, the temperature on the surface of that planet fluctuates dramatically, making it difficult for life to thrive, Meyer said.

Astronomers suggest that the gas and dust in the circumstellar disk can make oblong planetary orbits more circular, thereby stabilizing the temperature on the planet’s surface, making it more habitable, said Ilaria Pascucci, a research scientist in astronomy at the UA, and principal investigator for the study.

Most of the gas in the disk is molecular hydrogen, which is the most abundant element in the universe, Meyer said. Observing the small traces of neon in the circumstellar disk provides a means for researchers to better understand what is happening to the gas in the disk in the early stages of planet development.

“”The studies of gas in forming solar systems helps us to understand how our own solar system might have formed and evolved,”” Meyer said.

Neon in the circumstellar disk is heated by the star at the center, which causes the neon to become electrically charged, or “”ionized.”” As a result, the neon emits infrared light (heat) of a particular wavelength. That heat signal from the neon is what the researchers detected, Meyer said.

“”The particular observations that we published in the July edition of the Astrophysical Journal report detections of ionized neon, which is a species that we weren’t initially looking for. Thus it was somewhat of a surprise to see the neon in our Spitzer data,”” Meyer said.

By examining the behavior of gas in the circumstellar disk, the investigators conducting the study hope to answer some of the outstanding questions about how planets are formed. Among such questions, astronomers would like to know when, where and how frequently gas-giant, ice-giant and terrestrial planets form, Meyer said.

Gas giants are planets like Jupiter and Saturn while ice-giant planets include Neptune and Uranus. Terrestrial planets include the Earth and Mars, he added.

Heat from the young star also influences the chemical content of the disk during planet formation, which may play a role in the emergence of life.

“”We have recently realized that that high-energy emission (heat from the star), in addition to ionizing neon, can affect other atoms and molecules in gas-rich disks, thus changing the chemistry of those disks and helping to understand the abundance of molecules and atoms in those disks, some of which might eventually give rise to life,”” Meyer said.

UA astronomers hope to conduct future studies that will examine the influence of circumstellar disks on planetary orbits.

“”What we are hoping is to observe some hot, older (circumstellar disks) and trace how the gas is dissipating with time in the circumstellar disk,”” Pascucci said. “”We want to trace small amounts of gas in the region where, especially, terrestrial planets are forming, because it’s important for the circularization of the orbit of the planet.””

Neon, like most elements heavier than helium, is produced in stars through the process of nuclear fusion, Meyer said.

The Spitzer Space telescope was launched in 2003, and is operated by NASA. According to the Spitzer website, it is the largest infrared space telescope ever launched.