Gaia discovers its first supernova

September 12, 2014
An artist’s impression of a Type Ia supernova – the explosion of a white dwarf locked in a binary system with a companion star. While other types of supernovas are the explosive demises of massive stars, several times more massive than the Sun, Type Ia supernovas are the end product of their less massive counterparts. Low-mass stars, with masses similar to the Sun’s, end their lives gently, puffing up their outer layers and leaving behind a compact white dwarf. Due to their high density, white dwarfs can exert an intense gravitational pull on a nearby companion star, accreting mass from it until the white dwarf reaches a critical mass that then sparks a violent explosion. Credit: ESA/ATG medialab/C. Carreau

(Phys.org) —While scanning the sky to measure the positions and movements of stars in our Galaxy, Gaia has discovered its first stellar explosion in another galaxy far, far away.

This powerful event, now named Gaia14aaa, took place in a some 500 million light-years away, and was revealed via a sudden rise in the galaxy's brightness between two Gaia observations separated by one month.

Gaia, which began its scientific work on 25 July, repeatedly scans the entire sky, so that each of the roughly one billion stars in the final catalogue will be examined an average of 70 times over the next five years.

"This kind of repeated survey comes in handy for studying the changeable nature of the sky," comments Simon Hodgkin from the Institute of Astronomy in Cambridge, UK.

Many astronomical sources are variable: some exhibit a regular pattern, with a periodically rising and declining brightness, while others may undergo sudden and dramatic changes.

"As Gaia goes back to each patch of the sky over and over, we have a chance to spot thousands of 'guest stars' on the celestial tapestry," notes Dr Hodgkin. "These transient sources can be signposts to some of the most powerful phenomena in the Universe, like this ."

Dr Hodgkin is part of Gaia's Science Alert Team, which includes astronomers from the Universities of Cambridge, UK, and Warsaw, Poland, who are combing through the scans in search of unexpected changes.

It did not take long until they found the first 'anomaly' in the form of a sudden spike in the light coming from a distant galaxy, detected on 30 August. The same galaxy appeared much dimmer when Gaia first looked at it just a month before.

"We immediately thought it might be a supernova, but needed more clues to back up our claim," explains Łukasz Wyrzykowski from the Warsaw University Astronomical Observatory, Poland.

Discovery of supernova Gaia14aaa Credit: ESA/Gaia/DPAC/Z. Kostrzewa-Rutkowska (Warsaw University Astronomical Observatory) & G. Rixon (Institute of Astronomy, Cambridge)

Other powerful cosmic events may resemble a supernova in a distant galaxy, such as outbursts caused by the mass-devouring supermassive black hole at the galaxy centre.

However, in Gaia14aaa, the position of the bright spot of light was slightly offset from the galaxy's core, suggesting that it was unlikely to be related to a central black hole.

So, the astronomers looked for more information in the light of this new source. Besides recording the position and brightness of stars and galaxies, Gaia also splits their light to create a spectrum. In fact, Gaia uses two prisms spanning red and blue wavelength regions to produce a low-resolution spectrum that allows astronomers to seek signatures of the various chemical elements present in the source of that light.

"In the spectrum of this source, we could already see the presence of iron and other elements that are known to be found in supernovas," says Nadejda Blagorodnova, a PhD student at the Institute of Astronomy in Cambridge.

In addition, the blue part of the spectrum appears significantly brighter than the red part, as expected in a supernova. And not just any supernova: the astronomers already suspected it might be a 'Type Ia' supernova – the explosion of a white dwarf locked in a binary system with a companion star.

While other types of supernovas are the explosive demises of massive stars, several times more massive than the Sun, Type Ia supernovas are the end product of their less massive counterparts.

Low-mass stars, with masses similar to the Sun's, end their lives gently, puffing up their outer layers and leaving behind a compact white dwarf. Their high density means that can exert an intense gravitational pull on a nearby companion star, accreting mass from it until the white dwarf reaches a critical mass that then sparks a violent explosion.

Supernova Gaia14aaa and its host galaxy. Credit: M. Fraser/S. Hodgkin/L. Wyrzykowski/H. Campbell/N. Blagorodnova/Z. Kostrzewa-Rutkowska/Liverpool Telescope/SDSS

To confirm the nature of this supernova, the astronomers complemented the Gaia data with more observations from the ground, using the Isaac Newton Telescope (INT) and the robotic Liverpool Telescope on La Palma, in the Canary Islands, Spain.

A high-resolution spectrum, obtained on 3 September with the INT, confirmed not only that the explosion corresponds to a Type Ia supernova, but also provided an estimate of its distance. This proved that the supernova happened in the galaxy where it was observed.

"This is the first supernova in what we expect to be a long series of discoveries with Gaia," says Timo Prusti, ESA's Gaia Project Scientist.

Supernovas are rare events: only a couple of these explosions happen every century in a typical galaxy. But they are not so rare over the whole sky, if we take into account the hundreds of billions of galaxies that populate the Universe.

Gaia spectrum of supernova Gaia14aaa. Credit: ESA/Gaia/DPAC/N. Blagorodnova, M. Fraser, H. Campbell, A. Hall (Institute of Astronomy, Cambridge)

Astronomers in the Science Alert Team are currently getting acquainted with the data, testing and optimising their detection software. In a few months, they expect Gaia to discover about three new supernovas every day.

In addition to supernovas, Gaia will discover thousands of transient sources of other kinds – stellar explosions on smaller scale than supernovas, flares from young stars coming to life, outbursts caused by that disrupt and devour a nearby star, and possibly some entirely new phenomena never seen before.

"The sky is ablaze with peculiar sources of light, and we are looking forward to probing plenty of those with Gaia in the coming years," concludes Dr Prusti.

Explore further: Image: Where's Gaia?

Related Stories

Image: Where's Gaia?

February 18, 2014

(Phys.org) —Disguised in a crowded field of stars, the tiny white dot highlighted in these two images is none other than ESA's Gaia satellite as seen with the Very Large Telescope Survey Telescope at the European Southern ...

New suspect identified in supernova explosion

June 4, 2014

(Phys.org) —Supernovas are often thought of as the tremendous explosions that mark the ends of massive stars' lives. While this is true, not all supernovas occur in this fashion. A common supernova class, called Type Ia, ...

Spectacular supernova's mysteries revealed

August 22, 2014

(Phys.org) —New research by a team of UK and European-based astronomers is helping to solve the mystery of what caused a spectacular supernova in a galaxy 11 million light years away, seen earlier this year.

Recommended for you

Rocky planet found orbiting habitable zone of nearest star

August 24, 2016

An international team of astronomers including Carnegie's Paul Butler has found clear evidence of a planet orbiting Proxima Centauri, the closest star to our Solar System. The new world, designated Proxima b, orbits its cool ...

WISE, Fermi missions reveal a surprising blazar connection

August 24, 2016

Astronomers studying distant galaxies powered by monster black holes have uncovered an unexpected link between two very different wavelengths of the light they emit, the mid-infrared and gamma rays. The discovery, which was ...

Test for damp ground at Mars streaks finds none

August 24, 2016

Seasonal dark streaks on Mars that have become one of the hottest topics in interplanetary research don't hold much water, according to the latest findings from a NASA spacecraft orbiting Mars.

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

no fate
not rated yet Sep 15, 2014
A core collapse SN (not what Gaia saw).....

Here's a neat comparison. This is one of many proposed solutions to the mean free path of a photon produced in the core of the sun, this one says 4000 years to travel to emission surface. This is due to the assumed density of the core and various assumed layers making up the solar structure.

http://image.gsfc...354.html

SN1987A was several solar masses. The equations relevant to this phenomenon come up with...somehow, a kinetically powered explosion lasting a few days, which manages to propegate through several solar masses of matter. Sooo, light takes 4000 years...kinetic energy transfer through many times the matter...considerably less time.

Yet another math win....not.

All things being equal it would seem that a core collapse supernova explosion for a several solar mass star should take alot longer to manifest visually.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.