Questions tagged [observational-astronomy]

Questions about the techniques and practice of observing the night sky.

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4
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Significantly blueshifted Lyman-$\alpha$

Lyman-$\alpha$ line in galaxies is notably known to show a double peaked profile, mainly due to its scattering in a moving medium, see e.g., the very recent Matthee et al. 2021, The X-SHOOTER Lyman-α ...
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Can a star be massive enough to go 'supernova' yet not be massive enough to leave behind a neutron star? Or, perhaps vice versa?

From what I understand, stars that explode as a supernova at the end of their lives become either a black hole or a neutron star, and less massive stars that do not explode become white dwarves, but......
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Have there been any confirmed PISN supernovae?

I did some research on pair-instability supernovae (PISN), and wondered if there have been any confirmed superluminous supernovae caused by a pair-instability. Are there any confirmed PISNs out there, ...
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Pulsar signal periodicity detection algorithms?

I am currently working on pulsar signal periodicity detection. Most of the algorithm or paper which i read they use FFT (Fast Fourier Transform) and FFA (Fast Folding Algorithm ). Do we have any other ...
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2answers
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Delta Velorum - non-observed variable star

I am a beginner variable star observer from the Southern Hemisphere (but with experience in astronomy) and, when I was looking for VS to observe, I saw that Del Vel has almost no observations. Thus, ...
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How to identify a binary system moving over the night sky?

When I was about 13 (that's about nine years ago) I saw a star moving in a trochoidal motion only to realise it was a binary system. This binary system was traveling faster than a satellite but slower ...
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Sample bias' contribution to “Planet 9” hypothesis, why was this not thoroughly addressed before?

Science Claim for giant 'Planet Nine' at Solar System's edge takes a hit arXiv No Evidence for Orbital Clustering in the Extreme Trans-Neptunian Objects The brightness of distant solar system objects ...
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Effect of particulates on the visibility of stars?

I am looking for a (mathematical) relationship - either empirical or theoretical - which quantifies how the visibility of celestrial objects decreases with increasing amount of particulates in the air....
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Convert Object Intensity to Pixel Intensity

If I have an object of some size and spectral radiance, and it's some distance R from a camera, how would I calculate its digital count value in an image? I'm sure there's an equation out there, but I ...
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How can astrophysicists discriminate between pp-chain solar neutrinos and CNO-cycle ones?

Astrophysicists at the Borexino experiment in Italy have recently claimed that they have detected CNO-cycle neutrinos coming from the Sun. It was the Cover story for the November 26 issue of Nature. I ...
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Recently, the most distant object in the solar system was discovered. How was this accomplished?

It was recently announced that the most distant object in our solar system was discovered. This object averages 132 AU from the sun. The object, initially named Farfarout, was estimated to be 400 km ...
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How was the axial tilt of planets measured?

https://en.wikipedia.org/wiki/Axial_tilt#Solar_System_bodies gives the axial tilt of all planets with two decimal precision, but how and when were they measured so precisely ? I guess it's "easy&...
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Heat map of portion of the sky visible for a given observatory on Earth?

Reading Calculating area of visible sky I started wondering which portion of the sky one could observe how long given the 3D coordinates of an observatory, and two points in time. In other words, I ...
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What is the difference between 'Gravitational radius' (r_grav) and 'Schwarzchild radius' (r_Sch)?

From ResearchGate: https://www.researchgate.net/figure/Top-panel-Stellar-radius-as-a-function-of-stellar-mass-and-surface-temperature-given-by_fig3_313716289 I thought that 'Schwarzchild radius' ...
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Maritime telescopes: Stabilisation requirements for optical vs. radio telescopes?

SOFIA stands for Stratospheric Observatory for Infrared Astronomy. She says: My telescope stays stable with a spherical bearing, shock absorbers, and gyroscopes. I suppose a similar system would ...
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3answers
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What is a hard spectral state vs. a soft spectral state?

In X-ray astronomy, the source is considered to be in the hard or soft spectral state. So what is the meaning of the hard spectral state? What are the soft state and hard state in spectroscopy?
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Do higher-metallicity elliptical galaxies, that formed rapidly, have a larger velocity dispersion (lowercase-sigma)?

https://academic.oup.com/mnras/article/445/3/3092/1036122?login=true And, ..... https://www.newscientist.com/article/mg24933160-200-how-every-galaxy-comes-from-quantum-fluctuations-billions-of-years-...
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Eccentricity of Exoplanets

The field of astrobiology specifically discovering other planets that revolve around the sun-like star (also known as Exoplanets) has risen since 1990, but certain orbits of exoplanets are observed to ...
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Do some comets spin? If so, how fast?

The GIF below is copied from my question earlier What might a CN filter be in the context of comet watching? Is it showing dust, or gas, or something else? where I'd said: In this post on the website ...
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What does a “point spread function” look like for long exposures from the VLT's large interferometric aperture?

In interferometric radio astronomy UV plots are the first step in understanding what a point spread function (PSF) will look like for a given location in the sky observed over a period of time. The ...
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New method for exoplanet detection?

Could it be possible to detect exoplanets that have an abundance of iridescent minerals by analyzing their star's spectra over time as the angle in observation would lead to changes in absorbed ...
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What are recent discoveries with Earth-based radar telescopes?

The Wikipedia article on radar astronomy lists a few important discoveries using radar technology in general, i.e. also using space-crafts: The following is a list of planetary bodies that have been ...
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In how far is Hipparcos data still being used?

I remember being excited when ESA launched Hipparcos in 1989 and was in operation until 15 August, 1993. Later, Gaia came into operation in 2013. Reading What is the overlap between the Gaia and the ...
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Statistics of the purposes of archeoastronomical sites?

Archeoastronomy is not the most prominent tag used here at astronomy SE. It can be defined as the interdisciplinary or multidisciplinary study of how people in the past "have understood the ...
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1answer
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Observatories with public access in Europe

This is a follow-up to Observatories that allow public access with a smaller (geographical) scope. I am interested in getting to know observatories in central Europe (e.g. France, Germany, Poland, ...
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Why wasn't CHEOPS data taken during passage through the South Atlantic Anomaly downlinked in this case, resulting in gaps in photometry?

Section 4.1.2. CHEOPS in Six transiting planets and a chain of Laplace resonances in TOI-178 says Due to the low-Earth orbit of CHEOPS, the spacecraft-target line of sight was interrupted by Earth ...
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What is the completeness of an observation and how do I calculate it?

Many publications write about "completeness". I have a vague idea that it has to do with the ratio of how many sources from an observation are detected and how many sources are actually in ...
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Why does Nancy Grace Roman = 100 × Hubble? Why is the new space telescopes wide field camera so much wider than the old one's?

The title of the WFIRST project description (before it was named the Nancy Grace Roman Space Telescope) is The Wide Field Infrared Survey Telescope: 100 Hubbles for the 2020s. Question: Why does Nancy ...
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How often are electron-multiplying CCDs used in telescope focal planes? Will Nancy Grace Roman be the first use in a space telescope?

Section I. of The Wide Field Infrared Survey Telescope: 100 Hubbles for the 2020s says: Table 1 summarizes the WFIRST instrument suite, and Figure 1 presents the effective area of the Wide Field ...
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1answer
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Radial Velocity Graph and Rossiter Mclaughlin Effect

I am trying to understand the effect of the Rossiter–McLaughlin effect on radial velocity plots. Can someone help me and explain what exactly is happening in the red circle?
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What exactly would the resolution of an exoplanet hypothetically imaged by using the Sun as a gravitational lens be?

This video talks about how by sending a spacecraft to around 600 AU and beyond, we would could use the Sun as a gravitational lens and take clear detailed images of exoplanets light-years away. What ...
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In what ways are neural net classifiers “better” than search algorithms for eclipsing star system searches? (1D time series, not images of cats)

Neural net classifiers are both "hot" and useful. TIC 168789840: A Sextuply-Eclipsing Sextuple Star System is quite an interesting read, and describes the use of one trained on a ...
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From what distance could the Sun's planetary nebula be seen entirely with free eye?

When collapsing to a white dwarf, a red giant Sun would emit a planetary nebula. How far from the Sun would that nebula stretch at most? Also: At about what distance could you see the planetary nebula ...
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Different approaches to quantify light pollution on a given location on Earth?

The question Light Pollution: what is the difference between artificial brightness and brightness and SQM made me wonder which different ways exist to directly and indirectly quantify light pollution ...
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1answer
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Why was StDr56 discovered only now?

StDr56 is a newly discovered planetary nebula (maybe). link1 link2 It was found by amateur astronomers Marcel Drechsler and Xavier Strottner. According to the above articles, it's pretty big: With an ...
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Is it possible to use something besides emulsion to directly record the image of a nighttime object using a telescope?

The following questions have got me thinking. Is it possible to use Photolithography for telescope image sensor? Fresnel lenses for a makeshift Galilei telescope? Has anyone ever tried to make a ...
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1answer
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How many Kuiper Belt objects have moons? How do we know this?

On 2012 in the New Horizons' The PI's Perspective Alan Stern wrote The Kuiper Belt at 20: Paradigm Changes in Our Knowledge of the Solar System (more also archived) which includes: Most of the known ...
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Cross-matching astronomical catalogs

A project I'm working on involves getting data from SDSS DR12, and cross-matching it with NED, as described in Section 2 of this paper: 2.1 The sample From the SDSS Data Release 12 (DR12, Alam et al. ...
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About coordinate systems and angle differences

If I want to measure the beam-width of a radio telescope sweeping through a ~ puntual object (the Sun) with a ~ constant flux output when measured: The value measured sweeping in one frame of ...
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Can Pluto be seen with the naked eye from Neptune when Pluto and Neptune are closest?

When Neptune and Pluto are closest, about 100 million mi (160 million km) from each other, would an observer on Neptune (or rather on one of its moons, since Neptune is gaseous) be able to see Pluto, ...
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1answer
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Significance of astronomical twilight

What is the significance of astronomical twilight? Astronomical twilight is when "the geometric center of the Sun's disk is between 12 and 18 degrees below the horizon" , but what, if any, ...
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Line Flux Ratios in Active galaxies

Good day to everyone. I wanted to know what is the importance of estimation of line flux ratios in active galaxies? What does it help in characterizing? As in Lyman $\alpha /$Carbon IV, or Mg II$/$...
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537 views

Can we visually perceive exoplanet transits with amateur telescopes?

Is it possible for an amateur astronomer to visually perceive an exoplanet transit by the change of brightness of the star via observations spaced over time, or is the variation of the brightness too ...
2
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1answer
51 views

A factor of cos(declination) in the formula of apparent of drift velocity of stars

The angular drift velocity of stars is not the same for all stars and goes as $\frac{1}{\cos(\delta)}$. I don't understand why it should depend on the declination. All stars have to cover an angle of ...
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1answer
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How do we differentiate between a star or planet and noise introduced due to equipment?

I understand that differentiating between celestial bodies and noise due to equipment is a fundamental problem in astronomy. I also understand that we solve this problem by looking at something called ...
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1answer
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Ptolemy’s understanding of the planet’s whereabouts

I imagine that Ptolemy’s epicycles were performed as real circles - around equants - in two dimensions, e.g that he was able not only to give the angles to planets and the Sun as seen from the Earth, ...
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2answers
1k views

Is there a webpage that shows the night sky but can filter out dim stars?

This webpage is very good for viewing the night sky and learning the names of the stars Timeanddate - Astronomy However, it shows too many stars. Because I live in the city, I can only see about 50 ...
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2answers
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Understanding energy loss in a telescope aperture due to atmospheric dispersion

I'm trying to understand energy losses due to atmospheric dispersion, given the plot below from the Keck telescope. For a typical seeing I'm told that there's 80% encircled energy in 1". The ...
2
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1answer
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Optical emission line data archives

I am trying to do exhaustive optical emission line analysis of some active galaxies using archival data. What are some of the publically available data archives from where one could obtain optical ...
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Is the age of the Universe really 13.8 billion years?

Ok, I know this has been asked by a lot of people, but my reason for asking this question is a bit different. Please read further. I was watching a video by Fermilab (Start at 6:30, at 8:30 he ...

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