Tag Archives: planet formation

The Cross in the Heavens

I was on the Hubble website and came across this intriguing image:

The Hubble gallery website  calls the image “Developing Star AB Aurigae, Viewed With a Coronograph.”

Other than that title, the website provides only this additional information on the image: “Credit: C.A. Grady (National Optical Astronomy Observatories, NASA Goddard Space Flight Center), B. Woodgate (NASA Goddard Space Flight Center), F. Bruhweiler and A. Boggess (Catholic University of America), P. Plait and D. Lindler (ACC, Inc., Goddard Space Flight Center), M. Clampin (Space Telescope Science Institute), and NASA.”

There’s no explanation for the black cross superimposed over the image of AB Aurigae. So I went looking for more information.

A coronograph is “A telescope or an attachment for a telescope equipped with a disk that blacks out most of the sun, used to photograph the sun’s corona.”

AB Aurigae is considered to be young, estimated to be 1 to 3 million years old.

From Wikipedia:

AB Aurigae is a star in the Auriga constellation. It is better known for hosting a dust disk that may harbour a condensing planet or brown dwarf. The star could host a possible substellar companion in wide orbit.

Auriga is a constellation in the northern sky. Its name is Latin for ‘charioteer’ and its stars form a shape that has been associated with the pointed helmet of a charioteer. It was one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and remains among the 88 modern constellations today. Its brightest star is Capella. The Milky Way runs through the Auriga constellation.

Here’s another NASA image of AB Aurigae, from Wikipedia:

This is what an article on ScienceDaily (Mar. 26, 2008) says:

“Astrophysicists have a new window into the formation of planets. Ben R. Oppenheimer, Assistant Curator in the Department of Astrophysics at the American Museum of Natural History, and colleagues have imaged a structure within the disk of material coalescing from the gas and dust cloud surrounding a well-studied star, AB Aurigae. Within that structure, it appears that an object is forming, either a small body currently accreting dust or a brown dwarf (a body intermediate between stars and planets) between 5 and 37 times the mass of Jupiter.”

The ScienceDaily article also gives us more information about the coronograph used to take these images of AB Aurigae:

“Finding planets outside of our solar system is a new phenomenon. It is only in the last 15 years that nearly 300 extrasolar planets have been identified around distant stars. Most of these objects are more massive than Jupiter, orbit very close to their stars, and are identified by indirect methods such as the wobble created by the gravitational pull. None of the known exoplanets have yet been imaged or seen directly, because the light of a star overwhelms the faint glow of a nearby planet.

Oppenheimer and his colleagues circumvented this glare by attaching a coronagraph to a unique U.S. Air Force telescope on Maui, Hawaii. The telescope compensates for turbulence in the Earth’s atmosphere, permitting extremely high image quality from the ground. The Lyot Project coronagraph [...] blocks light from the center of the image of a nearby star to reveal faint objects around it.”

And here’s the image of AB Aurigae (no black cross) that accompanies the article:

More from the ScienceDaily article:

“AB Aurigae is well-studied because it is young, between one and three million years old, and can therefore provide information on how stars and objects that orbit them form. One unresolved question about planet formation is how the initial thick, gas-rich debris disk evolves into a thin, dusty region with planets. The observation of stars slightly older than AB Aurigae shows that at some point the gas is removed, but no one knows how this happens. AB Aurigae could be in an intermediate stage, where the gas is being cleared out from the center, leaving mainly dust behind.”

“He telleth the number of the stars; he calleth them all by their names.” -Psalm 147:4

~Eowyn