2,000-Year-Old Nova Remnant Spotted In One Of The Brightest Globular Clusters In The Milky Way

ESA/Hubble & NASA

Some 10,000 light-years from Earth, in the center of one of our galaxy’s brightest globular clusters, a dying star ignited 2,000 years ago in a luminous event known as a nova explosion. The blast left behind an object called an emission nebula – a nova remnant dating back two millennia and which has now been spotted by astronomers in a rare scientific feat, Science Daily is reporting.

The credit belongs to a team of European researchers led by Fabian Göttgens of the Institute for Astrophysics at the University of Göttingen in Germany. After scouring several globular star clusters in the Milky Way with the help of the European Southern Observatory’s Very Large Telescope (VLT) in Chile, the astronomers eventually locked eyes on the nova remnant in a star cluster known as Messier 22, or M22.

The interesting thing about their finding is that the nebula – one spanning a diameter of about 8,000 times the distance between the Earth and the sun – may have been originally detected by ancient Chinese scholars shortly after it first sparked into existence all those years ago.

“The position and brightness of the remains match an entry from 48 BC in an ancient collection of observations by Chinese astronomers,” Göttgens said in a statement.

“They probably saw the original nova in the same place.”

If this supposition holds true, then this latest detection, one made possible by modern instruments, serves to “confirm one of the oldest observations of an event outside the solar system,” details a news release issued yesterday by the University of Göttingen.

According to the German university, the astronomers stumbled upon the nova remnant after scouring the globular cluster with the VLT’s MUSE instrument. Aside from imaging the sky, MUSE is also able to split starlight by color, separating and measuring the brightness of differently colored light. This makes it particularly helpful in locating nebulae, which usually shine in a bright red color.

Unlike a supernova explosion, which spells stellar death and is so violent that it ends up disintegrating the star by spewing most of its mass out into the cosmos, a nova is a bright explosion of hydrogen gas occurring on the surface of a star. Novae usually take place within double star systems that contain a white dwarf (a collapsed, dead star) which suffers an outburst after absorbing a consistent amount of matter. The nova explosion makes the star temporarily shine brighter than usual, enshrouding the star in a ghostly shell of gas – but doesn’t actually destroy the star.

Photo of a nova remnant in the double star system Z Camelopardalis, showing a white dwarf, its stellar companion, and a massive shell of material leftover from a nova explosion.Featured image credit: NASA/JPL-Caltech/M. Seibert(OCIW)/T. Pyle(SSC)/R. Hurt(SSC)Wikimedia Commons/Resized

This was exactly the case with this particular nova explosion. As the astronomers point out in a paper describing their finding, despite the vast abundance of this type of binary star systems in our galaxy’s globular clusters, “only two novae from galactic globular clusters have been observed” to date.

In the aftermath of the event, an emission nebula began to take shape, one boasting a mass about 30 times that of planet Earth. As The Inquisitr previously reported, an emission nebula is an interstellar cloud of ionized gas and dust that emits light of various wavelengths.

“With this discovery, this nova may be one of the oldest confirmed extrasolar events recorded in human history,” the team wrote in their paper, due to be published in the journal Astronomy & Astrophysics and currently available on the preprint server arXiv.

The glowing nebula was uncovered in a portion of sky near the center of Messier 22. Known as one of the brightest globular clusters in our galaxy, Messier 22 was among the first objects of its kind to ever be discovered. Nestled about 10,600 light-years away in the Sagittarius constellation, this globular cluster is one of the closest to Earth, notes the European Space Agency.

The center of the globular cluster Messier 22, as imaged by the Hubble Space Telescope.Featured image credit: ESA/Hubble & NASA

Globular clusters are among the oldest stellar formations in the universe. Named for their spherical shape, these ancient bundles of thousands of stars are extremely dense and are held together by gravity. Often referred to as relics from the early days of the universe, globular star clusters date back to 12 to 13 billion years, or just a few hundred million years after the Big Bang, as previously covered by The Inquisitr.

Lying near the heart of the Milky Way, also known as the galactic bulge, Messier 22 is one of about 150 globular clusters discovered within our galaxy – and a captivating one to boot.

“M22 has some additional features that are particularly fascinating: two stellar-mass black holes, and six planet-sized objects (discovered by Hubble) that are not orbiting stars,” states NASA.

“The cluster is also one of only four of its kind ever found to host a planetary nebula — a short-lived gaseous shell ejected by a star at the end of its life.”