Image: McNeil's Nebula
Adam Block  /  NOAO / AURA / NSF
McNeil's Nebula, a newborn star surrounded by gas and dust, shows up in detain in a photograph made by the Kitt Peak Observatory.
By Senior Science Writer
updated 7/21/2004 8:52:13 PM ET 2004-07-22T00:52:13

In a rare find, astronomers have glimpsed the birth of a sunlike star whose environs might resemble our solar system in its infancy.

The discovery of a new bright spot in the sky earlier this year by an amateur astronomer spurred follow-up observations by professionals. The result, they said Wednesday, is a unique view of a dust-encircled newborn star that could aid in finding nascent planet systems around other stars.

The newborn star, less than a million years old, lights up a surrounding dust cloud called McNeil's Nebula, named for Kentucky amateur astronomer Jay McNeil, who first spotted the fuzzy patch of light with his backyard telescope on Jan. 23.

Rare outburst

Observations in visible and infrared light, during January and February, suggested the nebula had appeared in the sky because the star was having a radiation tantrum, which was probably related to an unseen disk that surrounds the star. Some of the gas and dust from this disk — the leftovers of the star's birth — was likely falling on the star to generate the outburst, researchers said.

A review of historical images of the same region in space found that the nebula was not visible in seven photographs made between 1951 and 1991, but it did show up in a 1966 photo. Other researchers were eager to jump on the case.

The new observations, made with NASA's Chandra X-Ray Observatory, show that the star was also flaring in X-rays in early March, but that the outburst was decreasing toward the end of March.

Important archive images of the region, made in 2002 for other purposes, revealed almost no X-rays, said astronomy professor David Weintraub from Vanderbilt. The X-rays in March were at least 100 times stronger, he said.

Weintraub said that because the X-rays and visible light seemed to ramp up and down during the same time frame, they were likely caused by the same mechanism, all supporting the original hypothesis of material falling in from what's called a "protoplanetary disk." That disk might be forming planets, but it's not yet possible to tell, Weintraub said.

Behind the eruption
Here's what probably caused the flare-up:

Natal gas and dust swirls around the fledgling star, now named V1647 Ori. The star grows by gathering this material, a process known as accretion. The star's gravity tugs at the material, but outward radiation pressure or some other mechanism works against the gravity, effectively creating a dam that can hold up for years or decades.

"The dam breaks and all this material just falls on the star," Weintraub told "It's a massive avalanche of material from the disk onto the star."

Similar to the sun
Only two other young, sunlike stars — one in 1936 and another in the 1950s — have been seen undergoing similar outbursts. This was the first to be observed in X-rays.

The eruption is probably similar to episodes the sun went through in its earliest epoch, Weintraub said.

More observations are planned over the next year to confirm that the outburst of V1647 Ori was caused by infalling material. An alternative explanation is that the event was similar to contemporary solar flares on the sun, which are generated by magnetic energy at the sun's surface. That appears unlikely, based on the characteristics of the event at V1647 Ori, scientists say.

If the radiation discharge from V1647 Ori is an indicator of a protoplanetary disk, similar X-ray observations could help find young stars that might be in the process of forming planets, Weintraub said.

Joel Kastner of the Rochester Institute of Technology also worked on the study, which is detailed in Thursday's issue of the journal Nature.

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