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Observations can be made using different parts of the electromagnetic spectrum. Many of them not within the range of the spectrum that can be made with optical telescopes. Other messengers than photons (e.g gravitational waves, neutrinos,...) can also be observed. Optical counterparts are observations made in the spectrum observable using optical ...


10

“No one thought of this,” she said. “We didn’t think of it. The astronomy community didn’t think of it.” What utter nonsense. SpaceX are either lying or they didn't bother to go looking for any other opinions. Astrophotographers have been complaining about satellites messing up their photos for years. When Starlink was announced astronomers complained even ...


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A recombination line is a special case of an emission line. Emission lines An emission line is any spectral feature that rises above the continuum — i.e. the average amplitude of the spectrum (in some wavelength region) — and is due to atomic transitions (where "atomic" include atoms in molecules and dust grains, and "transitions" may be electronic, ...


3

They are mostly empirical. Found by measuring the $B-V$ for stars of known $T_{\rm eff}$ (which are in turn measured by knowing the luminosity and radius of a star, and this is only known for a small number of stars). The relationships also depend on stellar surface gravity and composition. An alternative approach is to derive "synthetic" relationships by ...


3

You are correct that M81 transits the meridian at upper culmination just past mid-February in the eastern US. As long as the Moon is well below the horizon, as it will be in Feb. 2020, this will be the best time to observe M81, and its neighbor, M82. Since these galaxies are relatively bright, good views are available from late December through early May ...


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You can use the software Stellarium, which is available on most plateforms, and in-browser. With this software, you can show the constellations and the planets at any time and date, and see where the planets are in the sky. For instance, here you can see that Mars is in Libra and Mercury is in Scorpius. At the dates you specified, the positions of the ...


2

The biggest contributor to these two observations happening so close to each other is capability and interest. Our ability to observe such objects is ever increasing. Once we saw one, our interest increased and we looked harder ie. lots more funding for the necessary observations to be made that would identify such objects. We saw the next one soon after. ...


2

You can use astrometry.net to get the exact WCS of your image. From the website: If you have astronomical imaging of the sky with celestial coordinates you do not know—or do not trust—then Astrometry.net is for you There is a web application where you can just upload your image and it returns accurate calibrations.


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