The nova explosion 3,000 light-years away will make the new star visible on Earth
Frederick Walter, galactic astronomer and professor at Stony Brook University, explains what a nova explosion is and why we will be able to see the effects from it. Walter said the explosion will be visible for several days to most on Earth.
Solar eclipse fans still reeling from totality have something else to look forward to this year, which could also be a once-in-a-lifetime celestial event to witness.
A dance between two stars 3,000 light-years away will culminate in a massive explosion so bright that it will create the appearance of a “new” star in the night sky, visible to the naked eye for a few days and with a telescope for whole weeks.
Astronomers expect this nova explosion within the binary star system known as T Coronae Borealis, or T CrB, to occur between now and September. The last time this eruption was observed was in 1946.
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Stellar astronomer Gerard Van Belle, with the Lowell Observatory in Arizona, said the scientific community is eager for this burst to happen so they can use modern telescopes to study it.
“You have a star that’s aging and again, kind of expanding and being washed away by its outer material, and collapsing into the ashes of an even older star that all that’s left behind is this, this ember of fire, with true this thermonuclear core,” Van Belle said. “As material piles up on it from its companion, it finally explodes.”
A red giant star and a white dwarf orbit each other in this animation of a nova. The red giant is a large sphere in shades of red, orange and white, with its side facing the white dwarf, the lighter shades. The animation opens with the red giant on the right side of the screen, co-orbiting the white dwarf. When the red giant moves behind the white dwarf, a nova explosion on the white dwarf ignites, filling the screen with white light. After the light fades, a ball of ejected nova material appears in pale orange. A small white blob remains after the haze of material clears, indicating that the white dwarf survived the explosion. Credit: NASA Goddard Space Flight Center
A white dwarf star about the size of Earth and nearly as massive as the Sun is orbiting a red giant star, swelling in mass. The hydrogen that falls on the white dwarf accumulates over time, in this case, about 80 years.
How do astronomers know a nova explosion is going to happen?
Like the meteor showers we see every year, people on Earth have noticed changes in the night sky for a very long time. With T CrB, this bright burst was observed in the sky at least twice, 80 years apart, helping scientists determine that it was a periodic event.
“We’re starting to get very long timescales in astronomy for some of these things. And so this particular object, it was observed in 1866 to brighten. And then 80 years later, in 1946, it brightened again,” Van. said Belle. “It’s gone from something you can barely see with a pair of binoculars to something you can walk outside and see with your own two eyes.”
Van Belle said that in the previous two outbursts, the star brightened and dimmed over a two-year period, which has happened again.
“It looks like it’s ready to go,” Van Belle said.
When will the T CrB explosion occur?
Unlike a solar eclipse or a meteor shower, astronomers can’t give us an exact time and date for the Nova outburst, but that could change over the next 80 years when the next outburst occurs. Van Belle estimates that a future space telescope could make this possible.
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“Can we get to a point where we might be able to say, you know, ‘It’s going to be 5 o’clock Thursday’? But we’re not there yet,” Van Belle said.
Based on the observed brightening and dimming over the past two years, the best estimate is that the eruption will occur between now and September.
Astronomy technology has seen significant advances since the last time T CrB produced a visible explosion on Earth. This will be the first time scientists can study this event using state-of-the-art telescope arrays with extremely high resolution.
“Every telescope on Earth will probably make at least one observation of this particular event just to contribute to what is truly a once-in-a-lifetime kind of event,” Van Belle said.
A telescope at Lowell in Flagstaff is already observing the object to establish a baseline. This will help astronomers determine when the explosion begins and measure its expansion as the fireball expands.
Van Belle said many astronomers have been asking for observing time for telescopes while they wait for the event.
“These are some interesting requests where you don’t know where you need time, but you can do this where you can request something in advance and basically say, ‘OK, we’re going to take care of this thing, and we’re going to activate this target of opportunity when it happens’.”
When it does, array telescopes like those at Lowell Observatory can observe the explosion in detail. Van Belle said visitors to the observatory will also look through telescopes to see our young star in action.
Telescopes will see the brightness increase and, eventually, the spot will become larger as the fireball expands.
Van Belle said he is most interested in seeing the shape and direction of the eruption.
“Is it a big round thing? Is it bumpy on one side? Is it shooting a jet in one direction? It will probably start out as something that looks like a baseball, but eventually it will look more like a barbell by the time it’s done,” he said. “It’s probably going to be pretty pointed in the way it shoots the fireball.”
Where can you see T CrB in the sky?
The explosion will appear as a bright new star in the constellation Corona Borealis.
A conceptual image of how to find Hercules and its powerful globular clusters in the sky, created using a planetary software. Credit: NASA (NASA)
Before the nova explodes, it’s a good idea to start looking at the Big Dipper in the night sky, because Van Belle said it’s a useful finder for finding the new addition to the sky later this year.
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To find the new star, Van Belle said to follow the arm of the Big Dipper to the star Arcturus. During the summer, Arcturus can be found high in the sky just after sunset.
“About halfway along the arc, right above it, you’ll see a smiley face, which is the northern corona, the Corona Borealis. And this object is in the Corona Borealis,” Van Belle said. “Just look for something new, roughly above where your finger is on the smiley face of the Corona Borealis.”
According to NASA, the small, semicircular constellation Sagittarius is also near Bootes and Hercules.
When you look up and see something new, it indicates that the T CrB explosion has occurred.
What happens after the Nova explosion ends?
During the week of the explosion, Van Belle said that what we see as a “new star” in the sky is material thrown onto the white dwarf that acts as burning cinders.
After the whole matter has been burned, the process begins again and this dance in the T CrB system will continue beyond our lifetime.
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“The irony here is nova, the term we use to call this thing, is Latin for new. But actually, these are pretty old stars, and it’s just new because it’s new to us,” Van Belle said.
Van Belle said this explosive process could continue for the next 2 million years or so throughout the life of the red giant star until it eventually dies and becomes a white dwarf.
“It’s going to become something of a companion to it,” Van Belle said. “And then they’ll just circle around each other for the rest of the time.”