# Tag Info

29

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 an object that is moving around a point at one orbit per year you find that there are three saddle points, and these are L1, L2 and L3 If an object is in orbit ...

23

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 across the sky. But because they "come from space" and occur well above the clouds they are often considered to be part of astronomy. As you note, ...

9

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 distance of 26.4 Mpc, because at that time it was located near the zenith. The exposure time was 20 s. An analysis of his images show remarkably fast rise rate ...

7

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 the scale of years to months to weeks to sometimes days, are also variable stars. James K did mention Algol in his answer, but there are literally thousands of ...

7

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 on again as the eclipse each other, i.e. pass through each others shadows! This happens about twice every 12 years (Jupiter's orbital period) as the plane that ...

6

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. Yes, a ball at the exact top of a hill will sit there, but any tiny offset in position or tiny nonzero velocity will lead to it accelerating down the hill. As ...

5

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, with the secondary eclipse being shallower than the primary? Well probably because the surface brightness of the two stars is different - i.e. they have ...

5

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 behavior of magnetic fields in magnetars. Since the magnetar model was first proposed (Thompson & Duncan 1995), theory and observations have indicated that these ...

4

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 a rate of 0.02 and reaches its pre-burst luminosity with apparent magnitude of 10 to 12. Usually binoculars (take 8x42) will be able to spot this with ...

4

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? ASKAP has FREDDA which searches in total-intensity filterbanks (aka dynamic spectra) and triggers the voltages for imaging or localizing the FRB. general ...

3

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 Algol-type stars, try their observation planner tool with variable type EA. When you've selected a target, you can use their variable star plotter to make finder ...

3

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 for good S/N ratio, but not too long that CCD is saturated. 3. If you want to measure the length of the eclipse, you can follow since it is coming in until ...

3

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 that it should contain "cleaned" data. First, I would plot the dtr_flux column over bjd(time) to obtain a lightcurve. Depending on the type of eclipsing binary, ...

2

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 years, it means that its brightness varies as seen from earth when they are eclipsing (thats how we detect eclipsing stars and planets by the way), and that ...

2

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 up to 8 full 1k$\times$1k frames/second and considerably higher if windowed on an object. There is no need for photon-counting equipment for such a slowly ...

1

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 (ie sum of the power) with coarse spectral resolution (1 MHz) and relatively short integration time (~1 millisec). This data is searched in realtime and FRB ...

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