Star caught exploding after long hibernation
In 2009, astronomers watched as a star suddenly and unexpectedly brightened.
This brightening event, which happened in the V1213 Centauri star system, grew more and more luminous over the course of several days, putting on a show for people on the ground. But that extreme brightening didn't come from just anywhere.
A new study in the journal Nature this week tracks the evolution of the star system's brightening and eventual fading using data collected by a telescope, which just happened to be keeping an eye on its part of the sky.
You May Also Like
Astronomers think that a brightening event like the one that happened in 2009 occurs when a white dwarf star pulls matter from a companion star onto its surface, causing instability and an explosion known as a "classical nova" which makes the star glow more brightly than usual.
In general, novas are types of exploding stars which can become thousands of times brighter than usual.
By properly characterizing more of these systems in our galaxy and beyond, scientists can learn more about how various star systems evolved in our part of the universe.
"Classical novae [novas] attract attention during eruptions, when they are bright and easy to observe," Przemek Mróz, co-author of the new study, told Mashable via email.
"Because of [their] unpredictable nature, very little is known about pre-eruption behavior of novae. This work is the first case when the evolution of a classical nova can be investigated so precisely with long-term pre- and post-eruption observations."
A hibernating nova
The new study may help solve a stellar mystery.
Scientists have known for a while that a small number of novas explode on short time scales, brightening multiple times in a century, according to Mróz.
However, the populations of these "recurrent" novas and binary systems that seem to be pre-nova can't explain the numbers of novas astronomers observe in the Milky Way and the Andromeda Galaxy.
"You can try and explain the observed number of nova explosions by invoking short recurrence periods -- that each nova explodes quite frequently, say every 100 years," astrophysicist Jeremy Drake, who was not involved in the new study, told Mashable via email.
"But this does not match with observations, and typical nova recurrence times are thought to be more like thousands to hundreds of thousands of years."
Mróz said that V1213 Centauri appears to be a nova that "hibernates" and then explodes every several thousand to a few million years, and it could be one of many.
Mróz and the science team used data collected by the Optical Gravitational Lensing Experiment survey to check out what V1213 Centauri has been up to since the survey started to monitor the system in 2003.
From 2003 until the major nova event in 2009, the scientists saw a few "dwarf nova" events that caused sporadic brightening of the system.
This may have occurred as an irregular amount of mass transferred onto the white dwarf from its companion.
The research team found that once V1213 Centauri exploded, the mass that was transferred from the large companion star to the white dwarf was much higher.
This can be explained by the fact that the white dwarf likely heated the outer layers of the companion, fueling a higher rate of mass-transfer, also known as accretion, according to the study.
Now, however, the white dwarf should be cooling somewhat, allowing the heat to decrease and eventually going into a hibernation marked by very little accretion.
"It looks like V1213 Cen is a rare smoking gun for hibernation theory," Drake said.
Stellar family portrait
This hibernation theory -- which has been kicking around in the astronomy community for years -- could help explain why astronomers don't detect nova systems earlier: The systems don't look like novas.
"no one knows of their existence before they explode"
"It has been very difficult to confirm the theory, because the first one sees of a nova is usually when it explodes," Drake added.
"We can study it afterward in great detail, but since no one knows of their existence before they explode there are no observational data with which to probe the pre-explosion history."
Of course, while this may be something of a "smoking gun" for hibernation theory, it still isn't a sure thing.
V1213 Centauri only represents one system in a cosmic sea of novas.
"While V1213 Cen does look like it was hibernating, the observations that revealed by this are still very brief -- just a snapshot -- compared with the evolutionary timescale of the system," Drake said.
"We always have to be careful that the snapshot is truly representative of the general behavior of the system pre-outburst. To be sure of the hibernation theory, we would like to collect a much larger sample of objects observed extensively pre- and post-outburst."
Miriam Kramer worked as a staff writer for Space.com for about 2.5 years before joining Mashable to cover all things outer space. She took a ride in weightlessness on a zero-gravity flight and watched rockets launch to space from places around the United States. Miriam received her Master's degree in science, health and environmental reporting from New York University in 2012, and she originally hails from Knoxville, Tennessee. Follow Miriam on Twitter at @mirikramer.
