Questions tagged [observational-astronomy]
Questions about the techniques and practice of observing the night sky.
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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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Why aren't ground-based observatories using adaptive optics for visible wavelengths (circa 2016)?
Adaptive Optics (AO) techniques allow ground based observatories to dramatically improve resolution by actively compensating for the effects of Astronomical Seeing.
The atmospheric effects are quite ...
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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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What will it finally take to accurately measure the distance to Betelgeuse?
Comments below What is the maximum distance measurable with parallax? discuss challenges associated with parallax measurements of Betelgeuse and link to Wikipedia’s Betelgeuse; Distance measurements ...
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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 the blank wedges in this very early 21 cm map of the Milky Way? (Oort et al. 1958)
Jan Oort was a pioneer in radio astronomy. Wikipedia says:
It has been written that “Oort was probably the first astronomer to realize the importance” of radio astronomy. “In the days before radio ...
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How (the heck) was this photo of Venus at inferior conjunction (between us and the Sun) taken?
This great answer by @gerrit discussing planetary phases seen in visible light contains the image I've included below. According to the Wikimedia Commons link these are ESO images from the Venus ...
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What is the physical geometry of this apparent "eclipse" of a tiny moon of Asteroid Florence?
Below is a small GIF made from a small subset of images contained in the original 36MB GIF found at https://cneos.jpl.nasa.gov/images/news/florence.p5us.1Hz.s382.sep01.gif as I just found in the Sky ...
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Has optical interferometry been done at radio frequency using heterodyning with a laser in a nonlinear material?
If one collects narrow band optical emission from a large telescope with frequency $f_1$ and mixes it in a nonlinear crystal with laser light of a nearby frequency $f_2$, it would produce two new ...
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How did single dish (or single receiver) radio telescopes originally generate images?
That actually sums up my question nicely: How did single dish (or single receiver) radio telescopes originally generate images? - or at least 2D intensity maps or contour plots.
Early radio ...
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Will the Magdalena Ridge Optical Interferometer be able to image extended objects like the surface of the Moon?
Inspired by several questions:
When will a moon landing site be visible via telescope?
Could the E.H.T. produce an image of the human artifacts on the moon?
Picture of equipment left on the Moon?
...
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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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What is it exactly about these flares of infrared light from Sgr A* that "confirms" it is a supermassive black hole?
CNET.com's SCI-TECH
Scientists confirm a 'supermassive black hole' at the heart of our galaxy
It's "mind-boggling", they say.
This links to Astronomy.com's Scientists finally confirm the Milky Way ...
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Are astronomers waiting to see something in an image from a gravitational lens that they've already seen in an adjacent image?
@RobJeffries' answer to the question Does gravitational lensing provide time evolution information? points out that there can be a substantial different in arrival times of light from a given source ...
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How are rogue planets discovered?
Planets are usually found by observing a star and waiting for the light level to drop when a planet passes in front of it, but what about rogue planets that don't have host stars?
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What causes "North-South ambiguity" when doppler radar imaging a planet surface equator?
I'm having a hard time understanding why there would be this ambiguity. Also, why would this be not the case if the planet was viewed pole on?
Edit: "North South ambiguity" is a term used in ...
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What equipment and techniques were used to study Betelgeuse's diameter in 1920?
Comments below What is the maximum distance measurable with parallax? discuss challenges associated with parallax measurements of Betelgeuse and link to Wikipedia’s Betelgeuse; Distance measurements ...
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What can be learned from low frequency radio astronomy available outside of Earth's ionosphere?
As discussions and answers to How large does refraction become in radioastronomy? point out, it is difficult to do radio astronomy much below 30 MHz (or 10 MHz depending on how aggressive you are in ...
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Why did it take five years to "figure out" how to use astrometric calibration sources to deblur LOFAR images?
Quanta Magazine's The Hidden Magnetic Universe Begins to Come Into View is a fascinating review of a rapidly evolving field in astronomy.
It contains some statements:
In their paper last year, van ...
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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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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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Has Hawking Radiation Ever Been Observed?
I know Hawking Radiation has firm theoretical footing, but has a signal ever actually been observed? What observational research is being done to attempt to see this effect? Is it simply too tall an ...
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Can New Horizons be used to measure the distance to Betelgeuse (despite its fickle photocenter)?
The New Horizons spacecraft is almost 50 AU from Earth and near-simultaneous images taken by its telescope and one on Earth have demonstrated parallax without relying on the movement of Earth in it's ...
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Is 486958 Arrokoth (2014 MU69 aka Ultima Thule) the only solar-system object determined to be binary by occultation?
The asteroid 486958 Arrokoth was discovered to be binary by astronomers lugging a bunch of telescopes around (I think) camping with them. The timing offered additional astrometry for the orbit ...
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Will the first Event Horizon Telescope image of the Milky Way's black hole Sgr A* just be another lumpy orange donut?
@HDE226868's answer to Why doesn't the black hole in the center of the Milky Way glow similarly to the famous M87 image? explains that neither black hole is orange and any Event Horizon Telescope ...
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What does "GPU-accelerated butterfly matched filtering over dense bank of time-symmetric chirp-like templates" mean? (GW170817)
A new analysis of gravitational wave (and other data) from GW170817 on 2017-Aug-17 has been published, strongly suggesting that the merger of two neutron stars resulted in a large, rapidly rotating ...
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Which techniques are used to convert radio signals received by antenna to images?
I realized that after answering the question How do astronomers convert radio signals received by their antenna to images? I had missed the point that the OP was only asking about software.
I've ...
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When would we detect a tiny meter size natural satellite in a geostationary orbits?
A natural, tiny (meters-size, maybe 10.000kg mass) natural satellite could be trapped in a geostationary orbit. I wondered for quite some time:
When and how are we able to detect these satellites?
I ...
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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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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 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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What percent of planets are in the position that they could be viewed edge-on from Earth? (and thus able to undergo transits)
Star number 12644769 from the Kepler Input Catalog was identified as
an eclipsing binary with a 41-day period, from the detection of its
mutual eclipses (9). Eclipses occur because the orbital ...
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How was Earth's "quasi-satellite" 2016 HO3 "first spotted" and it's orbit determined?
Under a question I asked a few days ago Have there been any documented mini-moons since 2006 RH120? @Hobbes mentioned the recent news about 2016 HO3 - a near-Earth asteroid that stays near Earth ...
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Why moon sighted only in Kerala but not in rest of India?
I know for most of you the question may look silly, but Kerala is a state in India where the moon (Ramadan moon) will be sighted but not in rest of India.
I was reading the news article where I got a ...
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Radio telescope targeting
How do you target a radio telescope on the precise object you wish to observe? You can point it in the general direction but how do you get the information from the exact point in the sky that you are ...
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After only one eclipse of its X-ray bright primary, how can astronomers estimate the first extragalactic exoplanet's period to be about 70 years?
Phys.org's Astronomers may have discovered the first planet outside of our galaxy links to Di Stefano et al. 2021 A possible planet candidate in an external galaxy detected through X-ray transit (...
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How did VLT's adaptive optics obtain this resolution for Neptune? Is it really working in visible wavelengths?
This image of Neptune taken with the VLT is really impressive. The resolution is achieved by recent improvements in the adaptive optics.
Gizmodo: New Super-Crisp Images of Neptune Show How Far Our ...
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How bright is the Crab Pulsar's 30 Hz modulation in visible light? What color is it?
This answer to Has great eyesight been necessary for astronomers? mentions Astronomer Jocelyn Bell Burnell's recounting of a likely first visual observation of a pulsar. This can be found for example ...
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Is there a standardized "Astronomical Alert" system?
“Who saw” the binary neutron star merger first? What was the sequence of events? (GRB/GW170817) highlights a particularly notable astronomical alert, but I am sure that there are alerts triggered by ...
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How did Michelson measure the diameters of jupiter's moons using optical interferometry?
In Betelgeuse: How its Diameter was measured (Chant, C. A., Journal of the Royal Astronomical Society of Canada, Vol. 15, p.133, Bibliographic Code: 1921JRASC..15..133C) the author says:
The paper in ...
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Sunset on [Mountain] from [Viewing Point]
How do I get the days in this year when the sun will set exactly on top of Fuji as viewed from Enoshima.
I shamefully admit that I just want to take a nice picture of Fuji.
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Is the difference between LIGO & Virgo and their "Advanced" versions really generational, or were these just planned incremental upgrades?
I just learned the term "third generation gravitational wave detector" in answers to What would a kHz gravitational wave detector look like? (mountains on millisecond magnetars) How would it ...
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How do ASKAP's focal plane phased array feeds interact with the entire array phasing?
Sky & Telescope's ASKAP Joins the Hunt for Mysterious Bursts says:
A new telescope, the Australian Square Kilometre Array Pathfinder (ASKAP), has joined the search for energetic and elusive fast ...
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What is the LSST now? Where does LSST end and Vera C. Rubin Observatory begin?
Space.com's It's Official: Vera Rubin Observatory Named to Honor Dark Matter Scientist says:
"We're here today to focus on the major renaming of the facility after a pioneering astronomer, that ...
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In the 1950's how were radio-astrometric positions with portable dishes so precise they could be assigned to their dim optical counterparts (Quasars)?
In my question Why are quasars so far away that they couldn't be optically resolved in the 1950's? I included the following short paragraph, but then added strikethrough to the second sentence ...
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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 are all quasars so far away?
Why are all quasars so far away?
If the universe is homogeneous, we should expect to have a homogeneous distribution of quasars, but all of then seem to be far away from Earth. Why is that?
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Has radio astronomy ever been done on objects that appear very close to the Moon? Is this avoided?
This answer to Which kinds of astronomical observations most need to avoid the Moon being up? mentions
For completeness - radio, mid-infrared and mm-wave observations are unaffected (unless the ...
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What are the current observational limits on the existence of Dyson spheres/swarms/rings?
A Dyson sphere/swarm/ring is a hypothetical structure an extra-terrestrial entity would construct to collect a large fraction of its host star's light, and would likely generate a fairly strong ...
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How can we tell the difference between matter and antimatter by observation in space?
I just was wondering and searching on the internet with little luck in the topic. On Antimatter Wiki they tell the observable universe is built up by matter. I read antimatter can be detected in ...
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