London, September 16 : A new study has reported an object that brightened intensely and then faded back into obscurity over a period of about seven months, which is unlike anything astronomers have seen before.

According to a report in New Scientist, the Hubble Space Telescope first spotted the object, called SCP 06F6, in the constellation Bootes in February 2006 in a search for supernovae.

Nothing had been seen at its location before it started to brighten, and nothing was spotted after it dimmed, which suggests it is normally too faint to observe and that it brightened by at least 120 times during its firefly-like episode.

Stars are known to brighten dramatically when they explode as supernovae. But supernovae reach their maximum brightness after about 20 days, and this object took a leisurely 100 days to hit its peak.

The object’s spectrum is also bizarre.

It does not match that of anything seen in the mammoth Sloan Digital Sky Survey, which has mapped more than a quarter of the sky.

The spectrum shows a handful of spectral lines, but when astronomers try to trace any one of them to an element – such as magnesium, the other lines fail to match up with known elements.

“Because we can’t see anything we recognize in the spectrum, we can’t tell if it’s even in the galaxy or in another galaxy,” said Kyle Barbary of the University of California, Berkeley, lead author of the new study.

If it’s inside the galaxy, it might be a dim stellar ember called a white dwarf.

White dwarfs can brighten suddenly when they steal matter from a nearby stellar companion or suck in matter from a disc of debris around them.

If the object lies outside the galaxy, explaining its provenance is no easier.

When its discovery was first reported in 2006, astronomer Stefan Immler of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, suggested to New Scientist that the object might be a very distant supernova, lying about 12 billion light years away.

If it was that distant, the expansion of the universe would relativistically draw out a supernova explosion, making a 20-day event stretch out over a period of 100 days.

But, according to Barbary, that idea is unlikely because the object lies no farther than 11 billion light years away.

The team may try to re-observe the same region of space, just in case the object flares up again.

“It’s possible that it’s a cyclical thing and would come back, but it would be good to know if it doesn’t,” said Barbary. (ANI)