# Tag Info

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If you discover an exoplanet via the Doppler (radial velocity) method, then the amplitude of the radial velocity variations depends on the inclination, $i,$ of the exoplanet's orbital axis with respect to your line of sight. Conventionally, $i=90^{\circ}$ corresponds to viewing an orbit "edge-on", which maximises the velocity variations, while a ...

14

On what basis is the information about the distance and velocity of the Voyager probes determined? For distance: round-trip travel time of radio signals For velocity: Doppler-shift of round-trip radio signals, and by the rate of increase in distance as discussed above. The Voyagers as well as many other deep-space spacecraft before and after carry what's ...

13

Scale invariance and self-similarity Power laws basically mean that there is no preferred scale, i.e. that a physical property is scale invariant. Any deviation from a power law means that the Universe somehow thinks that the scale where it breaks down has some special significance. In other words, a power law describes self-similarity$^\dagger$. You can see ...

10

I'm not sure this question really belongs here, but you mention the word "astronomy", and I'm an astronomer and I have an opinion on how to add numbers with asymmetric uncertainties: Inherent ambiguity in a solution If you have the full probability distribution functions (PDFs) of two asymmetric distributions, they should be added by a convolution. ...

8

I have to admit that power-laws (in general) used to be my shtick so I am happy to shed some light on their general importance in physics which obviously also hold for astronomy. The main idea of a power law is nicely written in Wikipedia, but the essential part is the I highlighted in the following quote: [A Powerlaw is] a functional relationship between ...

8

Welcome to the world of software developed by scientists for their own use. There are not many clues. The top-level README cites Nemravová et al. 2016. That paper mentions PYTERPOL briefly in section 3.4 and says "solar metallicity was assumed" for the components of ξ Tauri. pyterpol/fitting/parameter.py has this code: parameter_definitions=dict( ...

7

Right ascension is usually given in hours, minutes and seconds, but declination is usually given in degrees, arcminutes (') and arcseconds ("), with one arcminute being 1/60th of a degree and one arcsecond being 1/60th of an arcminute. This means that the declination of the source you list should be 40$^{\circ}$08"55.6', in accordance with the SDSS ...

7

I think the underlying premise of the question -- e.g., "Why was this sample bias not thoroughly addressed before?" -- is somewhat incorrect. Previous papers, including papers by those making the "Planet 9" claim, have attempted to address sample biases; a secondary issue is that the new paper uses data unavailable to previous studies (...

6

I think you've misunderstood the article - the quantity that seemed to be occurring at integer multiples of some number isn't the frequency of the radio emission but rather the dispersion measure (DM) of the source. As photons travel through the interstellar medium, interactions with free electrons mean that lower frequency photons take longer to reach the ...

6

You can do it via the astroquery SDSS module; there is a function called query_sql.

5

I was wondering why the absorbtion lines of the template are broader then those of the galaxy, since it actually should be the other way arround. You are correct that it should be the other way around. The reason the plot looks confusing is that you are not actually plotting the galaxy spectrum in the top panel; you are plotting some combination of noise ...

5

A solution would be attempts at measuring those parameters directly for a large number of disks (not possible at the moment, except for a few cases and few variables) or use population synthesis calculations, to plug all the planet formation physics we think we understand into a model and see what exoplanet populations it produces. Those populations are then ...

5

If handwritten notes of visual observation are valid, a good candidate is the observation of Neptune by Galileo in 1612, 234 years before the actual discovery. Also available without paywall here

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 ...

4

Konstantin Batygin, one of the authors of the original Planet 9 paper, has an interesting Twitter thread here where he discusses this paper. I encourage you to read that, but briefly, his argument is that the Dark Energy Survey (DES) is already biased (not a judgment term here, just describing the sky footprint) to discover objects that are in the cluster of ...

4

You can do this via VizieR (main site at CDS, Strasbourg, France linked; worldwide mirrors are available). You can search by catalog name from that form or enter I/345/gaia2 to get the specific catalog table we want. Assuming you have no other constraints other than what you specified in your question, we can enter the following into the constraint fields: ...

4

No, automated algorithms won't ever be able to completely eliminate the effect of passing satellites. Some of the light reflected from the satellites into the atmosphere will then scatter and cause some amount of light pollution. The pollution isn't limited to just in the direction of observing. See: https://photo.stackexchange.com/questions/41722/can-you-...

3

The polytrope model of stars made early numerical calculations of stellar structure possible using anything from mechanical calculators to early electronic computers, and in certain cases, even analytically! In astrophysics, a polytrope refers to a solution of the Lane–Emden equation in which the pressure depends upon the density in the form $$P=K\rho ^{{(n+... 3 Different space agencies and different governments have different policies about archiving their data. One commonality that I have found, though, is that their systems are often difficult to find, they are often difficult to navigate or search and get the data, and then just as difficult sometimes to process. Sometimes, they also require an account. Doing ... 3 Splatalogue is an excellent resource that allows you to search for spectral line transitions for a given atomic/molecular species within a specified wavelength range. It compiles data from a number of sources, including JPL, the Cologne Database for Molecular Spectroscopy (CDMS), and Lovas/NIST. If you are looking for more detailed information than just the ... 3 This is a great question and sampling is always a little tricky. side note: It's important to make sure that no down-conversion has been done, that the " 1000-1400 MHz band" has not already been mixed with a 900 MHz local oscillator and shifted to 100-500 MHz before conversion. I had a hunch that you can get by with a lower frequency. I chose 1000 ... 3 From your comment I would take that you already know how to plot contours in python, but are not sure, at what level/height to plot them to get a 1-sigma/68% contour. The answer you can find, e.g., in table 1 from this paper: Avni 1976 Essentially, in case of a map of 2 parameters, your \Delta S = S - S_\mathrm{min} statistic follows a \chi² ... 3 Perhaps I am late, but the GCNS is available via VizieR. The data can be both queried there and downloaded via FTP: https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/649/A6#/browse, theoretically it is also available via the Gaia-Archive (https://www.cosmos.esa.int/web/gaia/), at least according to an announcement dating 21/12/2021, but I did not manage to ... 2 Neptune has an axial tilt of 28.3 degrees and an orbital period of 164.8 Earth years; currently, the north pole is tilted away from Earth. The maps in your question were each constructed from twelve exposures of Neptune: four each in 845 (red), 547 (green), and 467 nm (blue) wavelengths. Each of the exposures was then converted from an effectively-... 2 One thing you might try doing is to use the SkyServer Navigate interface to see if the object was imaged by SDSS. Enter the name in the "name" box in the upper left and then click on the "Resolve" button. If an image with the galaxy shows up, click on the "Object with spectra" checkbox in the "Drawing options" panel on ... 2 Say that you have an image with N \times N pixels that covers a region of sky of \theta \times \theta steradians. For each pixel i you have a value of flux density J_i, expressed in Jy/sr. The image contains a galaxy and you want to calculate its the total flux. If this were a continuum problem, you would need to do an integral$$F = \int_{\Omega_{...

2

I hope that someone more knowledgeable than me will answer this question, but this is what I understand it is happening. The bootstrap method gives an estimate of the probability distribution of the period, given the data. If the probability distribution were a Gaussian centered on the true period, you would probably see a Gaussian. But when estimating the ...

1

Please have a look at this forecast paper: 1611.00036. I will cite some important figures. There are two important observables in the large-scale structures: Baryon Acoustic Oscillations(BAO) and Redshift-space Distortions(RSD). BAO tells us the expansion history of the universe, so measuring BAO puts constraints on the equation of state(EoS) of dark energy. ...

1

The information you need to recreate the wavelength array is in the World Coordinate System (WCS) of the header, specifically: CRPIX1 = 1.00 CRVAL1 = 3500.0000 / central wavelength of first pixel CDELT1 = 0.900000 / linear dispersion (Angstrom/pixel) which lists the starting/reference pixel of the wavelength array (...

1

This is a partial answer based on the discussion in comments below the question. If one already has an "amplitude spectrum" and one wants to convert to a power spectrum, all you have to do is take the absolute value of the amplitude and square it. In Python (introduced in the question) that's just np.abs(amplitude)**2. When you take the Discrete ...

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