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Last updated on April 17, 2014 at 21:23 EDT

Telescope Catches Surprise Ultraviolet Light Show

May 31, 2005

JPL — It was a day like any other for a nearby star named GJ 3685A until it suddenly exploded with light. At 2 p.m. Pacific time, April 24, 2004, the detectors on NASA’s Galaxy Evolution Explorer ultraviolet space telescope nearly overloaded when the star abruptly brightened by a factor of at least 10,000. After the excitement was over, astronomers realized that they had just recorded a giant star eruption, or flare, about one million times more energetic than those from our Sun.

This dramatic flare event is just one of many serendipitous discoveries made by the Galaxy Evolution Explorer since its 2003 launch. Though the telescope was originally designed to spot galaxies, it has repeatedly witnessed a sky flickering with ultraviolet flares, bursts and fast-moving streaks. While the flares and bursts are from different types of stars, the streaks are asteroids, satellites or possibly space debris floating across the telescope’s field of view.

The findings have led astronomers to conclude that the ultraviolet sky, once thought to be a quiet backdrop for viewing galaxies, is, in fact, a rather festive place.

“We had no idea that the ultraviolet sky would be filled with so many things that go bump in the night,” said Dr. Barry Welsh, University of California, Berkeley, co-discoverer of some of the flares. “All of these objects are a bonus to astronomers, since the observations come free when the telescope is aimed at distant galaxies.”

“I was surprised by how often we have observed stellar flares and by the amazing size of some of them,” said Dr. Chris Martin, principal investigator of the Galaxy Evolution Explorer, California Institute of Technology, Pasadena. “Nature rarely disappoints us.”

Welsh presented the findings today at the 206th meeting of the American Astronom ical Society, Minneapolis, Minn.

So far, the Galaxy Evolution Explorer has recorded 84 bonus astrophysical events occurring on flaring stars, binary stars called dwarf novae, and pulsating stars, as well as countless pieces of space debris. These data are already being collected into public databases for other astronomers to study. For example, astronomers are using the new set of flare stars to test their flare theories.

The Galaxy Evolution Explorer is surveying the entire sky at ultraviolet wavelengths for clues to how the earliest galaxies evolved into mature galaxies like our own Milky Way. To detect these early, faint galaxies, the telescope was outfitted with specialized cameras that allow the arrival of each photon of ultraviole t light to be timed with a precision of about a microsecond.

“The telescope’s detectors have provided an unprecedented time resolution of these astrophysical events,” said Welsh. “Now, we can say what happens during each one-hundredth of a second of a flare event. That’s better information than most video cameras have when they take slow motion shots of athletes.”

A preliminary analysis of the enormous flare witnessed by the Galaxy Evolution Explorer around GJ 3685A – the largest ever recorded in ultraviolet light – shows that the mechanisms underlying these stellar eruptions may be more complex than previously believed. Evidence for the two most popular flare theories was found .

Flares are huge explosions of energy stemming from a single location on a star’s surface. They happen regularly on many types of stars, though old, small “red dwarf” stars like GJ3685A tend to experience them most frequently and dramatically. These stars, called flare stars, can erupt as often as every few hours, and with an intensity far greater than flares from our Sun. One of the reasons astronomers study flar e stars is to gain a better picture and history of flare events taking place on the Sun.

Caltech leads the Galaxy Evolution Explorer mission and is responsible for science operations and data analysis. NASA’s Jet Propulsion Laboratory, Pasadena, Calif., manages the mission and built the science instrument. The mission was developed under NASA’s Explorers Program managed by the Goddard Space Flight Center, Greenbelt, Md. South Korea and France are the international partners in the mission.

Videos and Animations

Video 1: Dwarf Star Erupts in Giant Flare — This movie taken by NASA’S Galaxy Evolution Explorer show one of the largest flares, or star eruptions, ever recorded at ultraviolet wavelengths. The star, called GJ 3685A, just happened to be in the Galaxy Evolution Explorer’s field of view while the telescope was busy observing galaxies. As the movie demonstrates, the seemingly serene star suddenly exploded once, then even more intensely a second time, pouring out in total about one million times more energy than a typical flare from our Sun. The second blast of light constituted an increase in brightness by a factor of at least 10,000.

Flares are huge explosions of energy stemming from a single location on a star’s surface. They are caused by the brief destruction of a star’s magnetic fields. Many types of stars experience them, though old, small, rapidly rotating “red dwarfs” like GJ 3685A tend to flare more frequently and dramatically. These stars, called flare stars, can experience powerful eruptions as often as every few hours. Younger stars, in general, also erupt more often. One of the reasons astronomers study flare stars is to gain a better picture and history of flare events taking place on the Sun.

A preliminary analysis of the GJ 3685A flare shows that the mechanisms underlying stellar eruptions may be more complex than previously believed. Evidence for the two most popular flare theories was found.

Though this movie has been sped up (the actual flare lasted about 20 minutes), time-resolved data exist for each one-hundreth of a second. These observations were taken at 2 p.m. Pacific time, April 24, 2004.

In the still image, the time sequence of the panels is upper left, upper right, lower left and lower right.

The circular and linear features that appear below and to the right of GJ 3685A during the flare event are detector artifacts caused by the extreme brightness of the flare.

Click here for the QuickTime video. Image credit: NASA/JPL-Caltech

Video 2: It’s Not a Bird or a Plane — Galaxies aren’t the only objects filling up the view of NASA’s Galaxy Evolution Explorer. Since its launch in 2003, the space telescope — originally designed to observe galaxies across the universe in ultraviolet light — has discovered a festive sky blinking with flaring and erupting stars, as well as streaking asteroids, satellites and space debris. One such streaking object — possibly an Earth-orbiting satellite — can be seen here flying across the telescope’s sight in this sped-up movie.

This probable satellite appears during the last 5 minutes of a 13.5-minute observation. It looks elongated because each picture frame containing the moving object is 19 seconds long. Faint ghost images on either side of the source are detector artifacts caused by the object’s extreme brightness.

These bonus objects are being collected in to public catalogues for other astronomers to study.

Click here to watch the QuickTime video. Image credit: NASA/JPL-Caltech

Video 3: Surprise Ultraviolet Party in the Sky — Galaxies aren’t the only objects filling up the view of NASA’s Galaxy Evolution Explorer. Since its launch in 2003, the space telescope — originally designed to observe galaxies across the universe in ultraviolet light — has discovered a festive sky blinking with flaring and erupting stars, as well as streaking asteroids, satellites and space debris. A group of six streaking objects — the identities of which remain unknown — can be seen here flying across the telescope’s sight in this sped-up movie.

The two brightest objects appear to perform a sharp turn then travel in the reverse direction. This illusion is most likely the result of the Galaxy Evolution Explorer overtaking the objects as it orbits around Earth.

Careful inspection reveals four additional faint objects with the same timing and behavior. These faint objects are easiest to see during the retrograde portion of their paths. Three appear between the two bright sources, and one is above them, near the edge of the field of view.

These bonus objects are being collected in to public catalogues for other astronomers to study.

Click here to watch the QuickTime video. Image credit: NASA/JPL-Caltech

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Telescope Catches Surprise Ultraviolet Light Show Telescope Catches Surprise Ultraviolet Light Show Telescope Catches Surprise Ultraviolet Light Show