A star system 3,000 light-years away is predicted to become visible soon | Hacker News Reader

A star system 3,000 light-years away is predicted to become visible soon

blogs.nasa.gov

190 pointsgnabgib46 comments

Nasa's report, which BI cites (and blocks the link behind a regwall) is here:

"View Nova Explosion, ‘New’ Star in Northern Crown"

<https://blogs.nasa.gov/Watch_the_Skies/2024/02/27/view-nova-...>

This also adds the useful information that this is a recurring nova, though I'd like to know how the forecast is being made and what it's based on.

Just past observations. If you’ve seen it go nova exactly every 80 years odds are it will do it again. Some nova are very regular, others can be unpredictable.

That makes sense. As opposed to a main-sequence nova, in which a very-late-sequence star goes through the advanced burning phases, with fusion progressively of carbon, neon, oxygen, and finally silicon (to iron) occurs. The final stages of this occur quite quickly, on the order of months, weeks, days, and even hours, as I understand. Whether or not the burning phases can be astronomically observed and predicted I don't know, and was what inspired my question above.

<https://ned.ipac.caltech.edu/level5/Sept16/Rauscher/Rauscher...>

For a 25M star (one 25 times our Sun's mass), these phases last ~0.5 my (helium), ~600 years (carbon), 6 months (neon), 6 days (oxygen), and about a day (silicon).

(More massive stars burn much hotter and faster than lighter ones.)

Ok, we'll change to that from https://www.businessinsider.com/how-to-see-exploding-star-no... above. Thanks!

In case anyone is interested in learning more about this star, Dr. Brad Schaefer wrote a nice article about it in the March 2024 issue of Sky and Telescope (subscription required):

https://skyandtelescope.org/sky-and-telescope-magazine/insid...

There is also an open-access journal article from March 2023 that summarizes his research on the system:

https://academic.oup.com/mnras/article/524/2/3146/7077557.

And a blog post announcing the latest estimate for the eruption (2024.4 +/- 0.4):

https://www.aavso.org/news/t-crb-pre-eruption-dip

My organization, the AAVSO, has material that can help you learn how to observe variable stars and make scientifically useful measurements. You can do this by eye, with binoculars, with a telescope, or with various digital sensors. In the case of T CrB, visual observations will yield very useful information. Please see https://www.aavso.org/tutorials and https://www.aavso.org/observing-manuals for more information.

From the article: "As the red giant tears apart nearby stars, the dense white giant absorbs the shrapnel, a mixture of hydrogen-rich materials that come its way. The tiny dead star then gradually becomes hotter until it reaches a breaking point when all that energy is released in a huge cosmic explosion — a so-called nova."

That's the worst explanation of a nova I've ever seen. You'd think the author would have at least glanced at the Wikipedia article about novae.

The explanation isn’t good but they aren’t talking about a normal supernova here, it’s a recurring one that I too never heard about earlier.

Nitpicking: Don't confuse https://en.wikipedia.org/wiki/Nova and https://en.wikipedia.org/wiki/Supernova

From Wikipedia:

> For other uses, see Nova (disambiguation), Novas (disambiguation), and Novae (disambiguation).

> Not to be confused with luminous red nova, supernova, kilonova, or micronova.

(Disclaimer: I have no idea what half of them mean, but I guess they are nasty things that can make a star brighter.)

Yup, syndrome versus disease.

NB: The quoted text appears in the BI article originally submitted.

<https://www.businessinsider.com/how-to-see-exploding-star-no...>

The URL's been changed to the Nasa source it references.

T Coronae Borealis is overhead in the evening in July. It's expected to go nova in 2024 brightening from mag10 to mag3. https://en.wikipedia.org/wiki/T_Coronae_Borealis

> T Coronae Borealis is overhead in the evening in July.

Sort of depends on where your head is located.

It's unfortunate that where I live, it doesn't get dark until well after bedtime in July.

> The star system, normally magnitude +10, which is far too dim to see with the unaided eye, will jump to magnitude +2 during the event. This will be of similar brightness to the North Star, Polaris.

I've never been in the northern hemisphere so I don't know how bright the polaris is :(

Not that bright but it is visible to the naked eye even in presence of mild light pollution.

I've never been to the southern hemisphere either, but Wikipedia's got our back!

https://en.wikipedia.org/wiki/List_of_brightest_stars

Looks like similarly bright southern stars include some of the following:

https://en.wikipedia.org/wiki/Alphard

https://en.wikipedia.org/wiki/Beta_Ceti

https://en.wikipedia.org/wiki/Alpha_Pavonis

https://en.wikipedia.org/wiki/Alpha_Trianguli_Australis

It's pretty bright, but not uniquely so. It'd be about the 20th brightest object in the sky (assuming even distribution).

It's visible with the naked eye, even in the presence of light pollution. But it's not eye-catching.

I’ve never been in the southern hemisphere and have always wondered how easy it is to find the Southern Cross.

This was the first thing I did when I landed in the South.

Answer: very easy. You know the shape from the flags and logos, you can't miss it. Magellanic clouds are harder to see, and require a place with little or no light pollution, but they're there too.

Fun fact: in Chile they sell tours to look at the sky - in Atacama desert, where light pollution is very low. A bus brings you to the desert and you look up. They also provide a tour guide who knows the sky and has a laser pointer (yes, strong laser pointers can be used to point to objects in sky). Sounds ridiculous, but is 100% worth the money. The view of Milky Way in its full unpolluted southern glory is breathtaking.

A go-to joke of the tour guides. Question: "So, you are in Chile and there's no polar star. How do you tell where's north?". Answer, after some ideas from tourists: "See the mountains over there? That's east. Like I said, you're in Chile."

It's nice that the nuclear explosion of novas and supernovas occur on a human perceptible timescale -- taking weeks to months, instead of a nanosecond or ten million years. I'm not suggesting anything superstitious or supernatural about it. Just that it's oddly convenient.

The speed of light pretty much precludes anything happening to an entire star on a nanosecond timescale.

In the other direction, it's basically a tautology. A "nova" or "new star" is, by definition, a relatively fast change. Much slower changes to stars also occur, but they tend not to get news articles written about them when they happen gradually over millions of years, and we don't call them novas.

For a main-sequence star, yes.

For a neutron star, at ~12 -- 30 km diameter, light-speed timescales are on the order of 40--100 microseconds, which would be the lower bound on whole-star cataclysmic events.

(Time dilation might extend this somewhat, perhaps by a factor of two or so.)

For a white dwarf, ~10,000 km, lightspeed events would be about 30 milliseconds (~300 times longer than on the neutron star). That's about 1/10 of an eyeblink.

I’m not religious but my fav “that’s oddly convenient“ fact is that just by going fast enough you can cross the universe in a human lifetime because of time slowing down. As a biologist I find that much more fascinating than all those poor “irreducible complexity” anti-evolution arguments. Perhaps a physicist feels the other way around.

Well, you can cross the universe in any amount of time. The human lifetime isn't special in that regard. A photon crosses the universe in zero time, and anything with non-zero mass can get arbitrarily close to zero time.

As I've seen this point made in the past, it's that travelling at a constant 1g acceleration the subjective time for an astronaut would be about 45 years in traversing the observable Universe (~14 billion light years).

That is, a comfortable and familiar acceleration gives a human-lifetime-equivalent journey (subjective time).

If you're planning a round-trip, you'll find rather more time has transpired on what used to be Earth.

<https://www.universetoday.com/129086/far-can-travel/>

> If you're planning a round-trip, you'll find rather more time has transpired on what used to be Earth.

Or less, depending on the rotation of the universe as a whole.

Or no return may be possible at any speed/acceleration given the expansion of the universe.

Given that the outbound journey is already technically challenging, that's very nearly quibbling, despite cosmological accuracy.

That 1g constant acceleration requires practically infinite amounts of energy

True.

However it is also the specific context in which the lifetime-universe-traversal concept emerges.

> A photon crosses the universe in zero time

That is not consistent with my observations.

Multiple universes, perhaps, depending on your cosmology/eschatology:

https://en.wikipedia.org/wiki/Tau_Zero

Surely these are occurring very frequently as there are trillions of stars out there. I imagine that space is so vast that the vastness makes these events difficult to observe. Am I wrong with this thought?

> This recurring nova is only one of five in our galaxy.

> This could be a once-in-a-lifetime viewing opportunity as the nova ouburst [sic] only occurs about every 80 years.

Just like how you can't see much of your body (without mirrors) because your body is in the way, we can't see much of the galaxy because there's galaxy in the way.

It is only 2600 light years away. Our galaxy is a little under 100000 light years across, depending on how you measure. So it is a rare type of double star, and it is very close to Earth, the combination is what makes it special.

Example: the Crab Nebula was the result of a supernova that was seen by Chinese astronomers about 1000 years ago: https://en.wikipedia.org/wiki/Crab_Nebula

Is there a mailing list or something that I can register to in case that actually happens? I bet Ill miss the news.

Corona Borealis is easy to see from the northern hemisphere. This nova gets to around 2.5 magnitude which should make it fair game to pick out with the eye even with some light pollution as in the SF bay area.

business insider is maliciously unhelpful

The NYT posted the (better) article that BI cribbed from 10 days ago: https://www.nytimes.com/article/nova-new-star-t-coronae-bore...

The reason is predictable is that it repeats every 80 years or so - I guess that's the orbit of the dwarf sun it's eating.

The orbital period is 228 days. They are very close (relative to the size of the red giant) which is why the white dwarf is absorbing material from the other star.

https://en.wikipedia.org/wiki/T_Coronae_Borealis

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