30 votes

Why is the L3 Lagrangian point not perfectly stable? And why is the Earth-Sun L3 point a bit less than one A.U.?

L1, L2 and L3 are saddle points in the effective potential of the gravitational field in a rotating frame of reference. That is if you combine gravity (of Earth and Sun) with the centrifugal force on ...
James K's user avatar
  • 121k
23 votes
Accepted

Can you see something active in the sky apart from satellites? Can there be amateur time-domain astronomy?

If it moves or flashes it isn't astronomy, it is meteorology or technology. There are only a few exceptions to this: Meteors are an atmospheric phenomenon, and a meteor will appear to move rapidly ...
James K's user avatar
  • 121k
10 votes
Accepted

Can a Nova occur outside of a binary star system?

To form a classic nova you need a white dwarf to be accreting matter, specfically hydrogen, onto its surface. The "obvious" source of this matter is another star that is very close to the ...
James K's user avatar
  • 121k
9 votes

Intuitive connection between the periods of oscillation of Betelgeuse and the elemental concentrations at its core? (Betelgeuse; Saio et al. (2023))

Sensationalist stuff and the $10^1$ to $10^2$ years till supernova claim is not made by the authors. The radial pulsation frequencies of a ball of gas depend on mass and radius. For a given mass, the ...
ProfRob's user avatar
  • 152k
9 votes

Can you see something active in the sky apart from satellites? Can there be amateur time-domain astronomy?

On September 20th, 2016, Victor Buso was testing his camera mounted on his 40-cm Newtonian telescope when he captured the first moments of a supernova. He was observing NGC 613, a spiral galaxy at a ...
D Duck's user avatar
  • 191
7 votes

Can you see something active in the sky apart from satellites? Can there be amateur time-domain astronomy?

Many stars are double, and some orbit each other fast enough and far enough for amateurs to be able to detect them and measure them, and see the change in positions over the course of a few years. On ...
Pierre Paquette's user avatar
7 votes

Can you see something active in the sky apart from satellites? Can there be amateur time-domain astronomy?

If you have even a modest pair of binoculars and can hold them steady or support them against something so you can watch the four bright Galilean moons of Jupiter than you can watch them blink off and ...
uhoh's user avatar
  • 31.1k
6 votes

Why is the L3 Lagrangian point not perfectly stable? And why is the Earth-Sun L3 point a bit less than one A.U.?

Why is the L3 Lagrangian point not perfectly stable? In the circular restricted three-body problem (CR3BP or CRTBP) an object at any of the first Lagrange points L1, L2, L3 is unstable mathematically....
uhoh's user avatar
  • 31.1k
6 votes

Has the new type II supernova SN 2023ixf's subtype been determined yet, and is a tentative light curve possible? Is it still getting brighter?

The TL;DR is that in the optical, it rose in brightness over about a week and is currently in a plateau. It might stay that way for a few months or it might buck the trend and begin to dim -- we don't ...
HDE 226868's user avatar
  • 36.6k
6 votes

Multi-messenger astronomy: what is the potential of simultaneous detection of gravitational waves and neutrinos from a supernova?

This article basically seems to answer the question. They quote from an earlier study: "Although no CCSNe have currently been detected by gravitational-wave detectors, previous studies indicate ...
Steve Linton's user avatar
  • 10.3k
6 votes

How close are we to observing all of the sky all of the time?

To answer the first phrasing of the question: "Not yet". Approximate answer to the second phrasing below, after discussion. Adding to GrapefruitIsAwesome's answer, there are a couple of ...
Raffles's user avatar
  • 161
5 votes
Accepted

Is "magnetars don't last long — just a year to a few years" really true? Is it a misquote or perhaps taken out of context?

It's certainly not true. I've watched the linked video and read the linked articles, and even with that additional context, I don't see a way for the quote to fit with our understanding of the ...
HDE 226868's user avatar
  • 36.6k
5 votes

The definition of eclipsing binary star systems

I assume that the diagram indicates what the observer sees (if they had a big enough telescope!). i.e. The viewpoint is nearly in the orbital plane but not quite. Why then are the eclipses asymmetric, ...
ProfRob's user avatar
  • 152k
4 votes
Accepted

How much time do I have left to easily spot the recently brightened Recurrent Nova RS Ophiuchi with binoculars and mild light pollution?

RS Ophiuchi is "Currently" Shining at a apparent magnitude of 5.12 (initially 4.6.) . It is fading at a rate of 0.01 and continues this progress for the next 43-47 days. Then it will fade at ...
Kavin Ishwaran's user avatar
4 votes

Observing eclipsing binaries

The AAVSO eclipsing binary section is a good place to start reading. Their how-to articles address eclipsing binary specific issues such as predicting times of minimum. To get a list of observable ...
Mike G's user avatar
  • 18.7k
4 votes

Observing eclipsing binaries

www.skymaponline.net might be the one you want. Main goal when taking images in terms of timing and exposition: 1. Choose time with good sky condition (e.g., clear sky, no wind) 2. Expose long enough ...
Kornpob Bhirombhakdi's user avatar
4 votes
Accepted

Do ASKAP and ALMA have "fast dump" interferometric modes? Can they see and perhaps report Fast Radio Bursts in real time?

Short answer: No and yes. Do ASKAP and/or ALMA have "fast dump" interferometric modes? Or do they have at least some way to extract dispersion of transient events at the millisecond level? ...
Surya's user avatar
  • 56
3 votes

How close are we to observing all of the sky all of the time?

If we limit ourselves to defining "all of the time" to at least once per day while it is night to avoid the issue raised by Aaron F of only observing optically when the sun isn't in the sky (...
GrapefruitIsAwesome's user avatar
3 votes

Which data should I use to take the fast Fourier transform (FFT) to find time period for eclipsing binaries?

For this, you should create a lightcurve, a graph of brightness over time, to view the data. For Kepler data, the bjd(date) column is the time in BJD. The dtr_flux stands for detrended flux, meaning ...
AstronomyGeek's user avatar
3 votes

Are chirped gravitational wave events generally first identified by searching through libraries of chirps?

LIGO/Virgo has multiple detection pipelines. Several of them (GstLAL, MBTA, PyCBC Live and SPIIR) are "modelled" searches which use large grids of pre-computed models to compare the signal ...
Rob's user avatar
  • 2,035
2 votes

Automated (and hopefully free) systems I can subscribe to sending email or SMS text message when the T Coronae Borealis Nova becomes visible?

You can create a (free) account with the AAVSO, and then subscribe to the "Time Sensitive Alerts" forum. The forum will then email you any reports of brightening of T CrB that variable star ...
James K's user avatar
  • 121k
2 votes
Accepted

Are chirped gravitational wave events generally first identified by searching through libraries of chirps?

If I’m understanding everything about what you’re asking and how it relates to this other thing, I believe a kind of library you’re thinking of refers to a surrogate model. The idea behind a surrogate ...
Justin T's user avatar
  • 3,404
2 votes

period of an eclipsing binary

The period (at least in physics) is defined the time an oscilating system needs to get back to its starting point (for a sinus curve its 2*pi). Now when they say an eclipsing binary has a period of T ...
RononDex's user avatar
  • 466
2 votes
Accepted

Time domain astronomy and fastest eclipsing binary ZTF J1539+5027 (+20 mag, 6.91 minutes): How to measure its minimum brightness?

Unless I've done my maths wrong, the period of total eclipse is about 18 seconds. The CHIMERA camera at Mt Palomar, the instrument which followed up the discovery of this system, can take exposures at ...
ProfRob's user avatar
  • 152k
1 vote
Accepted

How to derive gravitational-wave frequency vs time from strain vs time

It turns out there are many ways to do this. A, conceptually, straight forward way is to differentiate the phase, $\Phi_{lm}$, of the gravitational wave. Expanding the strain of the gravitational wave ...
Daddy Kropotkin's user avatar
1 vote

What is the fraction of the time that the JWST could view a short transient event on-demand as a function of position on the celestial sphere?

Depends largely on the targets elevation/altitude/latitude above the solar ecliptic. Best case is for targets that are within 5° of the poles of the solar ecliptic. These targets never leave the Field ...
Gabriel's user avatar
  • 111
1 vote

Do ASKAP and ALMA have "fast dump" interferometric modes? Can they see and perhaps report Fast Radio Bursts in real time?

Further to Surya answer, yes ASKAP can and does detect FRBs in semi-realtime. The reporting to the outside world is far from realtime, unfortunately. In summary an incoherent sum all antennas is made (...
Chris's user avatar
  • 306

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