First Images Show Organic Molecules

The darker colors represent colder areas; the bright colors warmer areas.
Credit: NASA/IPAC.

The first images from the Space Infrared Telescope Facility (SIRTF) were made available this week, showing dazzling infrared views of distant stars and galaxies. In addition, the observatory was renamed the Spitzer Space Telescope, in honor of the late Dr. Lyman Spitzer Jr.

Some of the images indicate the presence of organic molecules and other chemicals thought to be necessary for the origin of life. But James Houck of Cornell University, the principal investigator for the infrared-spectrograph science instrument, says the implication for life in these places is uncertain.

"What we see is a bunch of building blocks, a bunch of bolts, some screws – that doesn’t mean that a car is going to appear soon," says Houck. "It just means there are a lot of pieces that are characteristic of the pieces that must have gone into building a car. Predicting life on the basis of the evidence we have now is going very far out on a limb."

The Spitzer Space Telescope is the fourth of NASA’s Great Observatories, which include the Hubble Space Telescope (visible light), the Chandra X-ray Observatory and the Compton Gamma Ray Observatory. The Spitzer Space Telescope senses infrared radiation, or heat, from distant, cold, and dust-obscured celestial objects.

To illustrate how things look different in visible light than they do in the infrared, Michael Werner, the project scientist from NASA’s Jet Propulsion Laboratory, offered an infrared image of a dog.

"In the infrared, we’re primarily seeing the temperature of the dog," says Werner. "You’ll notice that his eyes, his mouth and his ears are warm, because they’re closer to his blood, closer to the skin. The places where the fur is particularly thick are colder, because they’re further away from the interior heat of the dog. And since he is a proper dog he does have a cold nose."

The young star HH 46-IR in a distant galaxy 3.25 billion light-years away. Click image for larger view. Credit: NASA/JPL-Caltech/A. Noriega-Crespo (SSC/Caltech).

One of the most dramatic images produced by the Spitzer Space Telescope involves the galaxy HH46. A star in this galaxy, which is not observable with visible light telescopes because of an obscuring black cloud of silicate dust, is 3.25 billion light years away from Earth.

"The light that we collected a couple of weeks ago began its journey three and a quarter billion years ago, about the time that life was first emerging on the surface of the Earth, shortly after the formation of the solar system," says Houck. "Almost certainly using building blocks similar to the ones that we detected, life became prevalent on the Earth."

Houck says this star, named HH 46-IR, is similar to the sun, and in the process of forming. There is a disk of material surrounding the star, and jets of gas being ejected from the star. This may resemble what our own solar system looked like in its earliest years. There’s a very large range of molecules in this object, including cyanide compounds, hydrocarbons, and carbon monoxide.

"It’s a poisonous place, but those are the building blocks that go into assembling larger and larger organic molecules – the process that will eventually lead to life," says Houck.

A massive disc of dusty planet-forming debris encircling the nearby star Fomalhaut. Click for large view. Credit: NASA/JPL-Caltech/K. Stapelfeldt (JPL), James Clerk Maxwell Telescope.

Closer to home, at only 22 light years away, is the star Fomalhaut. Although it is the 17th brightest star in the sky, a ring of dust prevents a clear view of Fomalhaut.

"We see the system edge on, so it doesn’t look like a star system," says George Rieke of the University of Arizona, the principal investigator for the multiband-imaging photometer science instrument. "The donut of dust is about 3 times further out from the star than Pluto is from the sun, and it’s very cold. It’s so cold that if we took the atmosphere of the Earth out to that zone in the star, it would all freeze out and all the nitrogen would be like rock on the ground."

The 24-micron image from the Spitzer Telescope showed, however, that warmer dust is concentrated toward the center of the star system. Rieke says that this dusty material is the result of planets or other small bodies in the system crashing into each other, disintegrating, and throwing their material out into interplanetary space.

"What we see around this star is not the planetary system itself, but the debris from which the planetary system evolves," says Rieke.

Lumps in the donut ring of dust indicate the presence of massive planets. They are creating a wake in the debris disk, pulling the dust into the inner system while deflecting comets from the outer part. This structure corresponds to our own solar system, with the Kuiper Belt and Oort Cloud located in the outer solar system, and the rocky planets having formed from dust and debris in the inner solar system.

Red regions in the spiral arms represent infrared emissions from dustier parts of the galaxy where new stars are forming. Click for larger view. Credit: NASA/JPL-Caltech/S. Willner (Harvard-Smithsonian Center for Astrophysics).

The Spitzer Space Telescope also produced an image of the spiral galaxy M81. This galaxy is located in Ursa Major (the Big Dipper). Not only were scientists able to dissect the galaxy into its component parts, but they found that the galaxy is coated with polycyclic aromatic hydrocarbons (PAHs).

PAHs are the building blocks for more complex organic molecules, and they appear to be widespread throughout the universe. PAHs may have played a vital role in the origin of life on Earth.

"Everywhere (PAHs are) on the Earth," says Giovanni Fazio of the Harvard-Smithsonian Center for Astrophysics, and principal investigator for the infrared-array camera science instrument. "It’s in the black part of your toast, and the grit on your grill. But most amazingly, it’s all over the surface of that galaxy M81, which is 12 million light years away."

The infrared image brought into focus what only looked like a fuzzy smudge when viewed through a visible light telescope. By peering through the dust, Spitzer is helping scientists learn about the regions of star formation, as well as the total energy emitted by the newly forming stars in the M81 galaxy.

"Because of (Spitzer’s) sensitivity, and its ability to view large areas of the sky, we are now able to lift the cosmic veil that has been blocking this view, and see the galaxy in all its components," says Fazio.

The Elephant’s Trunk Nebula is an elongated dark globule within the emission nebula IC 1396. Proto-stars are the bright red-tinted objects. These stars were previously undetected at visible wavelengths due to obscuration by the thick cloud and by dust surrounding the newly forming stars. Click for larger view. Credit: NASA/JPL-Caltech/W. Reach (SSC/Caltech).

Spitzer also found star-forming regions in the Elephant Trunk nebula. The nebula winds through the star cluster complex IC 1396, which is over 2,000 light years away and located in the constellation Cepheus. The Spitzer telescope looked through the gas and dust of the nebula to see proto-stars in the process of forming.

"In the optical, you primarily see a dark cloud, illuminated from the outside by a bright star," says Werner. "In the infrared, you don’t see the outside of the cloud, you see into the interior of the cloud. You can see new stars that are forming. This shows the ability of infrared wavelengths to look into dark places."

Launched from Cape Canaveral, Florida on August 25, 2003, the Spitzer Space Telescope is orbiting the sun. "It trails behind the Earth, like a faithful puppy dog," says Werner. This unusual orbit allows the telescope to get away from the heat of the Earth, and it also prevents the Earth from blocking the telescope’s field of view. The telescope will move away from the Earth at about a tenth of an AU per year. It is currently 5.4 million miles away. If you were to try to locate Spitzer in the night sky, currently it would be in the constellation Pisces.

The new name for the telescope was chosen through a contest sponsored by NASA. More than 7,000 names and supporting essays were submitted, with more than a third coming from outside the United States. Jay Stidolph, 28, a Canadian resident, submitted the winning entry.

Lyman Spitzer (1914-1997) was the first to propose placing a large telescope in space, and he devoted his career to furthering that idea. His efforts led to two successful NASA space telescopes: the Copernicus satellite and the Hubble Space Telescope. Spitzer also made significant contributions to the fields of stellar dynamics, the interstellar medium, and plasma physics.

The Spitzer Space Telescope has a projected life span of 5 years. The amount of liquid helium onboard (100 pounds) determines how long the telescope can be used effectively.