Questions tagged [observational-astronomy]
Questions about the techniques and practice of observing the night sky.
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How does the Earth move in the sky as seen from the Moon?
I just want to be sure I am visualizing this correctly, because it seems odd. The Moon is tidally locked to the Earth but there are wobbles to its motion due to libration. So from a point on the ...
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Why hasn't the "9th Planet" been detected already?
In the comments to this question, there was considerable doubt placed as to the subject of if the so called "9th planet" really exists. That wasn't really the intent of the previous question, so I ask ...
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Is there any role today that would justify building a large single dish radio telescope to replace Arecibo?
It seems that most of the modern radio astronomy instruments and observations that make the news are interferometers or phased array systems of one kind of another.
Is there any application left for ...
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If Earth is tilted, why is Polaris always above the same spot?
Why is Polaris, the North Star, always above (or near) the North Pole? If Earth is tilted, Polaris' path should be in winter 23 degrees away from its path in summer, or not?
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If you lived on the far side of the Moon, how could you infer the existence of Earth?
Suppose that you deposit an astronomer, armed with our current knowledge of orbital mechanics, on a dome on the far side of the Moon, so that the Earth is perpetually hidden from them.
(And, of ...
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How was the mass of Venus determined?
The mass of Venus seems rather complicated to determine to me:
Venus doesn't have any satellites, so you can't just apply Kepler's third law (like you would with Jupiter or Saturn for instance) to ...
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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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If Alpha Centauri A's solar system exactly mirrored our own, what would we be able to detect?
Suppose there was an exact replica of our solar system 4.4 ly away (people included). What would we be able to detect and with what telescope(s)? Which planets? Could we detect radio transmissions and/...
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Why is there a gap in this image of supernova discoveries?
I came across this gif showing supernova discoveries from the late 19th century to 2010. Here's the data in 2010:
Notice that there's a prominent region shaped like an inverted U in which there are ...
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Why did it take so long to invent telescopes given glass was used 4000 years ago in Mesopotamia?
Is a telescope difficult to make? Does glass have to be polished and shaped very precisely? Or is a device using two or more lenses to magnify things just not obvious?
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Which of the planets would be detected if they were exoplanets?
An (almost-)omnipotent being selects the solar system, presses Ctrl+C, and then Ctrl+V several times, creating copies at distances of 5, 500, 50.000, and 5.000.000 light-years away. All in a direction ...
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Why can't we observe the Oort cloud with a telescope?
The Oort cloud is a hypothetical structure based on our observation of long-period comets. There are currently proposals to design probes to confirm the existence of the Oort cloud.
Now, sending a ...
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Why did they decide to hit Dimorphos in the retrograde direction rather than prograde; was it a "coin-toss" or were there implications for observing?
CNN Space and Defense Correspondent Kristin Fisher does a really good job of summarizing the current state of the Double Asteroid Redirection Test early observational results for general public ...
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How is it possible that we haven't discovered anything in the Oort cloud yet?
The Oort cloud is a hypothetical cloud of small icy bodies surrounding the Sun at more than 1000 AU. It is thought to be a vast reservoir of comets that occasionally get disrupted, sending comets ...
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Why is the summer solstice night shorter than the winter solstice day?
I was looking at the sunrise and sunset times where I live (Aberdeen, Scotland) and I noticed something odd: the time between sunrise and sunset in winter is longer than the time between sunset and ...
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Is it possible to detect gravitational lensing of stars behind the Moon?
Eddington waited for a total solar eclipse to happen to be able to observe gravitational lensing of the stars behind the Sun. And nowadays, amateurs can do the same thing.
Of course, the Moon is much ...
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Is it possible to do planet observation during the day?
Keep in mind I'm just a newbie. So.... I have a new Newtonian telescope. It has 150mm opening and 1400mm Focal Distance on top of an equatorial mount. I have 25 and 10 mm eyepieces... and a 2x Barlow. ...
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Are there any double stars that I can actually see orbit each other?
If I had a nice amateur telescope†, are there any multiple star systems that I could observe over a few years or a few decades and actually see the movement of one or both of them over time?
My short ...
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Do these results mean that I have found this exoplanet?
Yesterday I was going through the TESS mission data on mast portal and after applying some filters I found some data. I started analyzing that data using the lightkurve library.
plot without using the ...
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Why can't we see distant galaxies with the naked eye?
If light keeps travelling in a straight line, why can't we see distant galaxies with the naked eye? Surely if you stared long enough, the light from them would eventually hit your eye? I apologize if ...
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How can I measure the angle between two stars?
This is a backyard astronomy question.
My middle-school-aged son and I would like to measure the apparent angle between two easily-visible stars more precisely than measuring with our outstretched ...
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What observations can be expected on LIGO if any when Betelgeuse goes supernova?
What observations can be expected from the LIGO† gravitational wave observatory if and when Betelgeuse goes supernova?
Would we know that Betelgeuse has gone supernova before we see it light up our ...
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Why can't observatories just stop capturing for a few seconds when Starlink satellites pass though their field of view?
Given that the positions and trajectories of the Starlink satellites are public, why can't the telescopes just ignore the photons they receive when the satellites pass through the field of view?
It ...
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Puzzling quotes from astronauts about earth size
I have no doubt that we have been to the moon. This question has nothing to do with a moon landing hoax. But, there are two quotes from two different astronauts regarding the size of the earth as ...
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What ground-based observational evidence is there that the Moon doesn't have an atmosphere?
The Moon doesn't have any significant atmosphere (surface pressure is $3\times10^{-15}$ bar). Can the absence of atmosphere on the Moon be determined with ground-based observations? When was it first ...
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Please check my Mars photo
Hi built my own newtonian telescope for the first time. Up until that point I had never used a telescope.
Can you please look at the photos attached and tell me if this is what Mars should look like ...
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At what distance from Earth would our Sun be the same apparent magnitude as the next brightest star in the sky?
When I stand outside looking at the night sky, to my untrained eye, everything except the moon looks like a star. I know intellectually that some are planets circling our sun, and some are entire ...
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Why are wavelengths shorter than visible light neglected by new telescopes?
The diagram below, which I stole from this post by @HDE226868, shows that angular resolution as a function of wavelength suddenly drops by three orders of magnitudes from visible to UV-light. The ...
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Where is it possible to observe the Moon for 24 hours?
I wrote an astronomy olympiad yesterday and there was one task I couldn't figure out an answer to:
Estimate at what latitudes it is possible to observe the Moon for at least 24 hours. Under what ...
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How was Trappist-1 discovered?
I was going through all the questions in this community related to TRAPPIST-1 in order to know how planets TRAPPIST-1b to TRAPPIST-1h were discovered, but there aren't any.
How were they discovered?
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Why doesn't dark matter clump strongly in the center of galaxies, since it doesn't feel either radiation pressure or the Pauli exclusion effect?
Dark matter is described as being spread not only throughout a galaxy, but also around it in a halo of some sort that extends far beyond the visible parts of the galaxy...
In fact, dark matter haloes ...
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Are there any galaxies which fell out of sight horizon due to cosmic expansion?
If farthest galaxies run away from us with acceleration making them exceed speed of light, we should expect them to disappear from sky among time with increasing quantity. Did we observe this? Can we ...
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How will Starlink affect observational astronomy?
I have recently found that people around the world have been posting observations of a line of moving objects in the sky which is very likely to be a part of Starlink satellite constellation, such ...
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How Would a Neutron Star Actually Appear?
Having seen many pictures produced by artists of neutron stars and planets that orbit some of them, I was wondering how a pulsar would appear to a human being, in visible light (assuming the intense ...
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How many pixels could an image of Proxima b taken by James Webb have?
I know it's very difficult for the James Webb Space Telescope to image the exoplanet Proxima b without an external coronograph (I have been told by NASA scientists that they don't know yet whether ...
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Why will HD 84406 be chosen as the first target for testing JWST?
HD 84406, is a star approximately 241 light-years away in the constellation of Ursa Major. HD 84406 will be the first star to be imaged by the James Webb Space Telescope in order to test the focus of ...
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"Next Generation Arecibo Telescope (NGAT)... would combine a 314-metre-wide platform with a swarm of 9-metre dishes on top" What would that look like?
In Nature News' August 11, 2023 Closing down an icon: will Arecibo Observatory ever do science again? found in The Observatory there is discussion of the Next Generation Arecibo Telescope (NGAT):
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When was the martian dichotomy first observed?
The North and South hemispheres of Mars are very different one from another. They have different elevations, different crust thickness, different surface ages. This is known as the martian dichotomy.
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How often do comets survive passage by the Sun?
I had heard that comet ISON might not survive a close pass by our Sun, and I was curious about the odds of how other comets had fared. So, how often do other comets survive a close pass by our sun? ...
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Could we detect the light of cities at night in other solar systems?
Would it be possible to see electric lights on distant planets using current telescopes?
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Why do small mirror imperfections matter with modern computers
Modern telescopes go to great lengths to have perfectly shaped parabolic mirrors. My question is, why go to the trouble of having a perfect mirror? Why not take a mirror roughly the right shape, and ...
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Why can space telescopes see through a planetary nebula?
I recently read the book "An Introduction to Planetary Nebulae" by Jason J. Nishiyama. Although I'm not an astronomy student, I could at least understand the written texts and less the ...
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What's the difference between minutes and arcminutes?
I read in trigonometry class that 1 minute is equal to 1/60 degrees. So, 'minute' is an angular unit. But also 'arcminutes' are used to measure seperation between celestial objects and also equals to ...
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Why does the Fourier transform of this CMB image have a hole in it?
The BBC's Desert telescope takes aim at ageing our Universe contains the image below of the Cosmic Microwave Background from the Atacama Cosmology Telescope or ACT. It looks like this is plotted with ...
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How can astronomers pinpoint the location of the source of a neutrino?
In the popular press, in recent months, we have heard a lot about high-energy neutrinos from far outside our solar system reaching our detectors....
But I wonder...
If a single neutrino from a great ...
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Did nobody in the Astronomy community think 12,000 new satellites in LEO might be a problem?
This answer to Can / should the Starlink satellites be blackened? mentions Space News' SpaceX working on fix for Starlink satellites so they don’t disrupt astronomy where SpaceX chief operating ...
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Have we ever observed a body, such as a large asteroid, "hitting" the Sun?
Some other SE questions about launching ICBM's into the sun got me wondering whether we have ever observed an object on a path that intersected with the Sun? How close did it get?
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Why does the moon sometimes appear giant and a orange red color near the horizon?
I've read various ideas about why the moon looks larger on the horizon. The most reasonable one in my opinion is that it is due to how our brain calculates (perceives) distance, with objects high ...
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How long should it take for us to observationally determine if Caltech's Planet Nine is really there?
Caltech just released a report that says there is possibly a large (10 earth mass) planet in a remote orbit (10 - 20 thousand year) that explains a lot of observations of Kuiper Belt objects. How long ...
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Will the Vera C. Rubin Observatory (formerly the LSST) make a significant increase in the rate of astronomical event alerts?
The NPR news article and podcast New Telescope Promises To Revolutionize Astronomy updates the status of the "Large Synoptic Survey Telescope under construction on Cerro Pachón in Chile".
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