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170 years late, light from star blast reaches Earth

UC SANTA BARBARA (US) — Astronomers are watching the astronomical equivalent of an instant replay of a spectacular outburst from Eta Carinae, a massive double-star system.

Dubbed the “Great Eruption,” the outburst lasted from 1837 to 1858 and temporarily made Eta Carinae the second brightest star in the sky. But luckily for today’s astronomers, some of the light from the eruption took an indirect path to Earth and is just arriving now.

The wayward light was heading in a different direction, away from our planet, when it bounced off dust lingering far from the turbulent stars and was rerouted to Earth, an effect called a “light echo.” Because of its longer path, the light reached Earth 170 years later than the light that arrived directly.

httpv://www.youtube.com/watch?v=_SXqf95rxvg


These images reveal light from a massive stellar outburst in the Carina Nebula reflecting off dust clouds surrounding a behemoth double-star system, a phenomenon called a light echo. The color image at left shows the Carina Nebula, a star-forming region located 7500 light-years from Earth. The massive star Eta Carinae resides near the top of the image. The three black-and-white images at right show light from the eruption illuminating the dust clouds over an eight-year span as it moves through them. The effect is like shining a flashlight on different regions of a vast cavern. Credit: NASA, NOAO, A. Rest (STScI) and N. Smith (U. Arizona)

Astrophysicists affiliated with the University of California, Santa Barbara, and Las Cumbres Observatory Global Telescope Network (LCOGT) report the findings in a letter to the journal Nature.

Armin Rest of the Space Telescope Science Institute in Baltimore, Md., initially discovered the light echoes, and was the leader of the study.

Federica Bianco, a postdoctoral researcher at UC Santa Barbara and LCOGT, used LCOGT’s Faulkes Telescope South in Siding Spring, Australia, to record the explosion after this time delay and compare it to eyewitness reports of the brightness of the star from the 1800’s to determine that the light echo was indeed from the “Great Eruption.”

“You are at the stadium, watching the game, and your team scores,” says Bianco. “But you are too far away to get the details of the action, or in the case of Eta Carinae’s great eruption, you do not have modern instruments, detectors, and spectrographs to study it.

“Now we are getting a replay—an up-close, detailed view of our cosmic eruption. And just like with the replay, we get to see the outburst from a different point of view, as the light that we see now was originally traveling in a different direction than the light seen in the 1840s.”

One of astronomy’s greatest hit

Andy Howell, a staff scientist at LCOGT and adjunct faculty member at UC Santa Barbara, adds: “We finally got to watch firsthand the event that created the iconic Hubble Space Telescope images of giant lobes of gas expanding away from Eta Carinae. It turns out it was an explosion—and a strange, cool one. It just blows my mind that we can go back in time and watch one of astronomy’s greatest hits, and greatest mysteries, with a cosmic instant replay.”

The observations are providing new insight into the behavior of powerful massive stars on the brink of detonation. Very massive stars, especially a pair of them, are exceedingly rare, and little is known about how they lose mass as they die.

The views of the nearby erupting star revealed some unexpected results, which will force astronomers to modify physical models of the outburst.

Located 8,000 light-years from Earth, Eta Carinae is one of the largest and brightest star systems in our Milky Way galaxy. Although the chaotic duo is known for its petulant outbursts, the Great Eruption was the biggest ever observed.

During the 20-year episode, Eta Carinae shed some 20 solar masses. Some of the outflow formed the system’s twin giant lobes. Before the epic event, the stellar pair was 140 times heftier than our Sun.

The team’s study involved a mix of visible-light and spectroscopic observations from ground-based telescopes. These observations mark the first time astronomers have used spectroscopy to analyze a light echo from a star undergoing powerful recurring eruptions, though they have measured this unique phenomenon around exploding stars called supernovae.

‘Oddball’ star

Spectroscopy captures a star’s “fingerprints,” providing details about its behavior, including the temperature and speed of the ejected material.

The replay is giving astronomers a unique look at the outburst, and turning up some surprises. The turbulent star does not behave like other stars of its class. Eta Carinae is a member of a stellar class called Luminous Blue Variables—large, extremely bright stars that are prone to periodic outbursts.

The temperature of the outflow from Eta Carinae’s central region, for example, is about 8,500 degrees Fahrenheit (5,000 Kelvin), which is much cooler than that of other erupting stars.

“This star really seems to be an oddball,” Rest says. “Now we have to go back to the models and see what has to change to actually produce what we are measuring.”

The team first spotted the light echo while comparing visible-light observations they took of the star in 2010 and 2011 with the U.S. National Optical Astronomy Observatory’s Blanco 4-meter telescope at the Cerro Tololo Inter-American Observatory (CTIO) in Chile. They obtained another set of CTIO observations taken in 2003 by astronomer Nathan Smith of the University of Arizona in Tucson, which helped them piece together the whole 20-year outburst.

The research group will continue monitoring Eta Carinae because light from the outburst is still streaming to Earth.

“We should see brightening again in six months from another increase in light that was seen in 1844,” Rest says. “We hope to capture light from the outburst coming from different directions so that we can get a complete picture of the eruption.”

More news from UC Santa Barbara: www.ucsb.edu/news-topics

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9 Comments

  1. Clayton

    It is so hard to grasp that there is no way it all just happened.Why is it so hard for man to accept a creator?

  2. Clayton Derp

    Is it so hard to grasp that I’m derp derp derp derp derp derp derp!

  3. Jesus

    You tell’em Clayton! You’re so smart and scientists and physicists are so dumb! Much ado about me merely farting in outer space!

  4. Darwin

    Just another fool with a god delusion

  5. Consider it

    Could it be possible that God is the master scientist? Consider the amazing amount of knowledge scientists and physicists have garnered since the 1840s…imagine what another 200 years or so of research will reveal. It all goes to show that we are barely scraping the surface of what we understand.

  6. Ramakishore

    Everybody trying to fool others in the name of Science. the referred Stars are 8000 light years from earth and how can the light come to earth immediately. What we see must be an old story. we have no technology with which we can assess anything as of now. What all we get is something that happened millions of years back. This information is just academic for those who study that subject. It is true that one should appreciate the creation itself which is Amazing. Since we do not know who the creator is , it is apt to call GOD (Generator Organizor and Destroyer) created everything like X factor in a mathematical problem solving.

  7. Edwin Nirdlinger PHD, MD

    What is being observed happened 8,000 yrs ago. But wait! The earth, sky etc etc were only created 6000 yrs ago! Just ask the ignorant religious folks who take the christion creation myths literally.. God must be trying to trick us. Why? “To test our faith”! Why doesn’t she just tell us and get on with things? I always hated tests!

  8. God

    To be honest, i created everything ! But honestly im also a liar !!

  9. Outsource a freelancer

    Stunning images but shouldn’t the title be 170 years later – not late?

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