How to catch a glimpse of a new star about to appear in the night sky:

[oldpaddoboy]

The following interesting article promotes awe and wonder at the power of science and the mathematics involved. A shame that such news and education isn't published in our every day newspapers and broadcasted on TV and radio. 

https://phys.org/news/2024-04-qa-glimpse-star-night-sky.html

Q&A: How to catch a glimpse of a new star about to appear in the night sky:

by Daniel Strain, University of Colorado at Boulder

"If you peer up at the constellation Corona Borealis—the Northern Crown—over the next several months, you may catch a glimpse: Astronomers predict that sometime this year, a new star will appear in the night sky, growing as bright as the North Star, then vanishing in a matter of days.

 

The source of that pinprick of light is a stellar system roughly 3,000 light-years from Earth called T Coronae Borealis, or T CrB. There, two stars circle each other, interacting in ways that—like clockwork—produce a powerful eruption of energy about once every 80 years—an event called a recurrent nova. T CrB became visible briefly in 1946, and scientists suspect that it's on the verge again.

David Wilson is an astrophysicist and research associate at the Laboratory for Atmospheric and Space Physics (LASP) at CU Boulder who studies the ultraviolet light that stars emit.

While astronomers wait for T CrB to burst, Wilson gives his take on what causes this impressive event—and how curious stargazers can catch a glimpse."

 

More at link..............................

Supplementary article....

https://phys.org/news/2024-04-huge-star-explosion-sky-lifetime.html

 

[oldpaddoboy]

A shame we won't get to see it from Australia and the Southern hemisphere!

[Daveman]

You can see Corona Borealis from Sydney right now if you have a clear view of the northern horizon. There is an excellent article in the March 2024 Sky & Telescope on T Corona Borealis.

[OceanBreeze]

20 hours ago, Daveman said:

You can see Corona Borealis from Sydney right now if you have a clear view of the northern horizon. There is an excellent article in the March 2024 Sky & Telescope on T Corona Borealis.

Looks dim right now but should be easy to see when the nova happens.

[OceanBreeze]

On 4/30/2024 at 4:31 AM, oldpaddoboy said:

A shame we won't get to see it from Australia and the Southern hemisphere!

According to Daveman, you will be able to see it unless you are down in Tasmania somewhere!

What I didn't find in the links was a good explanation of why the scientists are so sure the nova will happen this year.

The last one was in 1946, + 80 years is 2026. Why 2 years early?

[oldpaddoboy]

On 5/22/2024 at 6:01 PM, OceanBreeze said:

According to Daveman, you will be able to see it unless you are down in Tasmania somewhere!

What I didn't find in the links was a good explanation of why the scientists are so sure the nova will happen this year.

The last one was in 1946, + 80 years is 2026. Why 2 years early?

Great! Thanks for the update. 

 

[oldpaddoboy]

On 5/21/2024 at 9:21 PM, Daveman said:

You can see Corona Borealis from Sydney right now if you have a clear view of the northern horizon. There is an excellent article in the March 2024 Sky & Telescope on T Corona Borealis.

Thanks Daveman. My Northern horizon view is somewhat blocked from my position, so I may have to do  some driving.

 

[OceanBreeze]

On 5/24/2024 at 3:01 AM, oldpaddoboy said:

Great! Thanks for the update. 

 

Actually, I wasn't updating you. I was asking if you knew why the astrophysicists and astronomers were predicting the nova event to happen this year instead of 2026. I could not find an explanation in the links. Did they spot some specific activity that triggers the nova event? It seems odd to me that they are predicting this with a degree of certainty when 80 years have not yet elapsed.

Do you have any thoughts about that?

 

[oldpaddoboy]

8 hours ago, OceanBreeze said:

Actually, I wasn't updating you. I was asking if you knew why the astrophysicists and astronomers were predicting the nova event to happen this year instead of 2026. I could not find an explanation in the links. Did they spot some specific activity that triggers the nova event? It seems odd to me that they are predicting this with a degree of certainty when 80 years have not yet elapsed.

Do you have any thoughts about that?

 

Nice pickup. I went through the links myself, and like you, couldn't find anything specific. Perhaps as you say, when the nova event becomes likely, there are specific signs or activity. Other then the following taken from the article, which indicate an "error range" in predictability,  I couldn't really say.  

"But every 80 years or so, exchanges between its two stars, which are locked in a deadly embrace, spark a runaway nuclear explosion."

"Starrfield is currently rushing to finish a scientific paper predicting what astronomers will find out about the recurring nova whenever it shows up in the next five months.  "I could be today... but I hope it's not," he said with a laugh" 

"Once the mass roughly of Earth has built up on the white dwarf—which takes around 80 years—it heats up enough to kickstart a runaway thermonuclear reaction, Starrfield said."

end of quotes:

My only thought is perhaps the orbital ellipticity has some bearing on exactly when it is predicted and when it occurs?

"

[oldpaddoboy]

I also found this interesting comment....here: https://phys.org/news/2024-03-astrophysicist-science-lifetime-nova-outburst.html

"Outside of the novelty of these novae,, Blazek says systems like T CrB are particularly interesting for astrophysicists because they are prime candidates for Type 1a supernovae, even larger stellar explosions that are integral to mapping the cosmos.

When a star like T CrB's white dwarf hits a certain mass after repeated novae and it can't support its own mass, it starts to collapse and erupts into a massive, bright explosion, known as a supernova. Novae occur every 80 years, but supernovae are one-time events because they are so powerful that they end up destroying a star. Type 1a supernovae are even more notable because they seem to always have the same brightness, which means they likely always happen to stars of the same mass, Blazek says."

 

Which prompts the question, Will this be a nova, or a type 1a supernova, and how can they predict the difference? 

[OceanBreeze]

On 5/26/2024 at 4:58 AM, oldpaddoboy said:

Nice pickup. I went through the links myself, and like you, couldn't find anything specific. Perhaps as you say, when the nova event becomes likely, there are specific signs or activity. Other then the following taken from the article, which indicate an "error range" in predictability,  I couldn't really say.  

"But every 80 years or so, exchanges between its two stars, which are locked in a deadly embrace, spark a runaway nuclear explosion."

"Starrfield is currently rushing to finish a scientific paper predicting what astronomers will find out about the recurring nova whenever it shows up in the next five months.  "I could be today... but I hope it's not," he said with a laugh" 

"Once the mass roughly of Earth has built up on the white dwarf—which takes around 80 years—it heats up enough to kickstart a runaway thermonuclear reaction, Starrfield said."

end of quotes:

My only thought is perhaps the orbital ellipticity has some bearing on exactly when it is predicted and when it occurs?

"

Ok, I believe I have finally found a detailed explanation about why astronomers are fairly certain about the T CrB nova happening this year.

From this link:

/Quote

Recurrent nova T CrB has just started its Pre‑eruption Dip in March/April 2023, so the eruption should occur around 2024.4±0.3

 

Authors: B. E. Schaefer (Louisiana State Univ.), B. Kloppenborg (AAVSO), E. O. Waagen (AAVSO), and the AAVSO observers

 

T Coronae Borealis (T CrB) is a famous recurrent nova with known eruptions in the years 1217, 1787, 1866, and 1946.  Many workers have realized that the rise in brightness from its low state (1954.5 to 2015.0) to its high state (2015.0 to the present) is a precursor and harbinger for an upcoming eruption around 2025.5±1.3 or so (Munari et al. 2016; Schaefer 2023).  A distinct and under-appreciated close-up harbinger is the unique and mysterious Pre-eruption Dip (Schaefer 2023).  The Dip in 1945-1946 started around 1945.0 (1.1±0.3 years before the 1946 eruption), with the B-band magnitude fading from near 10.5 to 12.0 mag, while the V-band magnitude faded from around 9.8 to 12.3 mag. This fading ended abruptly with the nova eruption.

 

In anticipation of the start of this Pre-eruption Dip, we have been frequently monitoring the up-to-date light curve as collected into the AAVSO International Database.  The AAVSO B and V band light curves from 2021.0 to present, with 2-day binning, for 4330 B-band mags and 12734 V-band mags, all with CCD photometry, are linked below.  The normal light curve since 2016 shows the usual ellipsoidal modulation, with a full amplitude of ~0.4 mag for a sinewave at half the orbital period.  The light curve shows variations about this average curve on all time scales, with larger variations in the B-band than in the V-band, all arising from ordinary flickering always present since 1867.  Starting around 2023.25, T CrB shows a systematic fade from its long-time ellipsoidal variations.  This fading is far outside of any historic variations since 2016.  The fading in the blue was 0.4 mag in 2023.3 to 0.8 mag in 2023.5.  The fading in the V-band was 0.25 mag in 2023.3, and 0.35 mag in 2023.5.  The fading in the R and I bands are substantially smaller.  This color dependency in the fading is consistent with increasing dust absorption, for a scenario featuring a recently discrete mass ejection in which dust formation occurs (much like for R CrB stars).

 

So the T CrB Pre-eruption Dip has already started in March/April of this year.  If the Dip in 2023 is similar in timing to that in 1945, then the primary eruption should occur roughly 1.1±0.3 years later, or in 2024.4±0.3.  This prediction is substantially improved over the prior predictions based only on the 2015 rise to the high-state.  Still, possible deviations from the behavior in 1946 could create an early or a late eruption.

 

This announcement of the start of the Dip and the prediction of the eruption date (2024.4±0.3) will hopefully be of use for researchers for making proposals with a wide variety of telescopes.  Further, this serves as advance notice to take all needed pre-eruption baselines, for example obtaining infrared fluxes and background nebulosity images over a wide field for later light echo detections.  And it is not too late to try to understand the pre-eruption high-state, with it still being unclear whether the increased luminosity comes from increased accretion or from nuclear burning on the white dwarf.  For observations before the upcoming eruption, we particularly point to U-band photometry, UV spectrophotometry, and spectral line profiles, all for measuring the energetic physical mechanism of the Pre-eruption Dip, while long-running infrared photometry might detect dust formation.

/Unquote

 

My understanding from reading this, is there is a pre-eruption dip in the binary star system’s brightness, just about a year before the nova event. The actual mechanism behind the dip doesn’t seem to be well understood. It could be from formation of a dust cloud due to a large mass ejection from the red giant that gets absorbed by the white dwarf. The increased mass of the white dwarf causes a thermonuclear reaction, which is the nova.

The pre-eruption dip, before the nova, brings to mind how the tide goes out before a tsunami hits the shore. Of course, this is just an analogy; the mechanisms are totally different.