Tag Info

Hot answers tagged

13

One way to answer would be to consider the brightest star in our sky (other than the Sun), which is Sirius. Then determine how far you would have to be from our Sun for it to be as bright as Sirius is from here. That turns out to be 1.8 light years. That's not even halfway to the nearest star, so if you're in any other star system, then our Sun is just ...


12

You could confirm with taking an image of the star trails. They would form a circle with the apparent center at the zenith of the location. You do not need a pole star at all. Just a night of viewing. You would also be able to tell based on the height above the horizon that the sun is. On the equinox, the sun would be on the horizon at noon (when it is ...


12

A lot of satellites are visible under the right conditions. Usually up to 2 hours after sunset and 2 hours before sunrise. This allows the sun to strike the satellite when you are on the dark side. Depending on the orbit, it will take between 1 and 5 minutes to traverse most of the sky. Usually, they will enter the shadow and you lose sight of them.


10

Two basic conditions need to be met for anyone on the globe to observe the International Space Station (ISS) from any location: ISS needs to pass roughly overhead of your location, and it needs to do that during night so it's visible to the naked eye Now, obviously there are other requirements, like e.g. weather (if it's overcast we won't be able to see ...


9

As Mark Adler mentioned, the best way is to compare the brightness to other nearby stars. I'm going to assume that you have instantaneous travel time, and also take into account that you are actually getting closer to stars depending on the direction you go. I'm using this table from Wikipedia. I'm going to go no further on the list than Sirius, and assume ...


9

Key factors: How close is perihelion? Too close and it may be destroyed on its first pass. We know Halley's Comet, which has a perihelion of about 0.6AU, has been orbiting for over 2000 years, passing the sun every 74-76 years and is still going strong. How big is it? Every pass loses material, so a bigger comet could last longer. What is its composition? ...


7

Here's an answer I wrote for a question on Space.SE, but which applies equally well here. Let's talk about the Hubble space telescope, which would be much better at observing these comets than any ground telescope: From astroengine.com Using the equation: (d / D) × c = φ where d is the diameter of the Oort Cloud comet (some estimates put this ...


6

Yes, there are filters which do block out the vast majority of light from the sun. I think it's actually only a very small (~1 angstrom) wavelength band of light which gets through. You can see some pretty amazing features, including sunspots, and solar flares. Here's a composite image as an example (taken through a Hydrogen alpha filter): Those smallish ...


6

Your guess was correct. It is the Andromeda Galaxy, M31. Here is a map of the part of the sky near zenith at the place and time you provided: Sky map for Taganrog, Russia on 11/23/2013 5:00:00 PM UTC. Even the rotation is small. The sky map is rotated approximately 30° counter clockwise relative to the photo. You were approximately facing south when taking ...


6

Is there any publicly available, NEO-related database out there? Or is there a specific institution a hobby-astronomer can/should turn to to be able to learn more about individual NEOs? Yes, there is NASA's Near Earth Object Program that catalogues all detected NEO's and had advanced reporting and seearch capabilities (a bit overwhelming number of ...


6

The real reasoning has nothing to do with some civilization "deliberately" hiding its radio emissions. Rather, the problem is that we can not expect some other civilization to do something we would not do ourselves. It makes no sense whatsoever to radiate large amounts of energy into space when there exist other, more economical alternatives. Radio ...


6

The answer to your question is yes. Many times discoveries in astronomy are serendipitous in nature - some of the most well-known discoveries fall into this category: the discovery of the cosmic microwave background, the discovery of some of the planets in our solar system, are but two examples of this. However, many times they are not serendipitous. ...


5

As for projecting the Sun onto a screen at a low cost, I would recommend starting with a ~50-200$ sunspotter box, which is basically a lens mounted on a wooden box, that projects the sun onto a white piece of card. The advantage of using a telescope is that it can be programmed to track the Sun, so that if you want to trace sunspots, for instance, you can do ...


5

(Source, Wikipedia Commons) The moon is generally called a "Harvest Moon" when it appears that way (i.e. large and red) in autumn, amongst a few other names. There are other names that are associated with specific timeframes as well. The colour is due to atmospheric scattering (Also known as Rayleigh scattering): may have noticed that they always ...


5

This would be the SETI's Colossus telescope project, that aims to build a high-resolution, multiple-mirror instrument with ability to directly image the heat generated by other civilizations on planets orbiting stars near us:          Artist's impression of the proposed SETI's Colossus Telescope (Credit: Innovative ...


5

The answers provided to this question so far seem to be good. The easiest way I'd say is to take a long exposure picture in one of two places: 1) At the zenith (directly overhead), if you see that your picture looks like this: you are at either one of the poles. If the center of rotation of the stars is off by some angle (in degrees), you are that same ...


5

There are a couple of things you have to think about in order to understand the problem at hand. The first is that there are three coordinate systems at play. The first is the celestial coordinate system, which is a coordinate system based upon the latitude and longitude of the Earth (the celestial equator is the Earth's equator projected out into space). ...


5

There exist many astronomical catalogs, reaching from rather simple catalogs like the Bayer catalog for stars, or the Messier catalog for galaxies, nebulae, etc., to huge catalogs with millions of entries. A catalog with about a billion objects is scheduled for 2022. There exist also printed editions of some catalogs. Objects in the sky have several ...


5

It's a broad question, but I'll take a stab trying to provide the essentials for a good start. Also see this post which contains important additional information: Best telescope for the viewing of Nebulae, Stars and Planets There are many, many factors involved in choosing a telescope. You seem settled on a dobsonian. That's not the only possible choice, ...


4

To determine if you're at a pole: Be there during that pole's half-year "night". Better around the solstice, when the sun will be well below the horizon Pick some of the brighter stars visible, scattered at different azimuths. Measure the altitude above the horizon of each. Tricky if you don't have a sea level horizon. Stay warm for a few hours. Measure ...


4

There are many such online services, most of them free and a Google search away, so I won't make this a list answer, and since you didn't specify what data in particular you're hoping to find, here's one of my favorite satellite trackers with fairly complete position data, ground track display, map options and so on: NASA iSAT (Interactive Satellite Viewer). ...


4

Direct observation of exoplanets (and then of traces of life on them) is still a big challenge. Up to now, there are several indirect methods (effects on the parent star or on other stars), and direct detection is performed by using devices such as coronagraphs on faint stars, where very bright planets are imaged. A way to image things such as as ...


4

Parallax measurement in practice is not as is explained above using the popular diagram you have used. The parallax causes the star to prescribe an ellipse in the sky, the semi-major axis of whose is equal to the parallactic angle. The telescopes generally measure the shift in co-ordinates of star(RA and Dec) and then translate the information to that of ...


4

I had a chat with a European PhD student who plans to make an attempt to find Oort cloud objects in data from the Gaia space telescope. This could be possible thanks to microlensing events when an Oort object transits (near) a background star and relativistically magnifies the star's light for a moment. Best case is that in a few years we will have a map of ...


4

Ask Wolfram Alpha. Here is an example.


4

I'm trying to imagine what a hypothetical observer on the surface of Alpha Centauri Bb would see in the daytime sky. I know it would vary depending on the orbit of b around B, as well as the position of B and A in relation to each other. My calculations are based on data from these wiki pages: http://en.wikipedia.org/wiki/Alpha_Centauri ...


4

This is a spectral energy distribution (SED). Since astronomical objects don't emit light a single frequency an SED tells you how much emission you're getting across a range of frequencies. "log" indicates it's on a logarithmic scale $\nu$ represents frequency in Hz (e.g. $log~\nu=12$ is $10^{12}$ Hz) Jy is a unit of specific flux density $f_{\nu}$ is the ...


3

Because there are so many planets out there! There just happens to be an entire web page dedicated to calculating that answer. Transits can only be detected if the planetary orbit is near the line-of-sight (LOS) between the observer and the star. This requires that the planet's orbital pole be within an angle of $d_/a$ (part 1 of the figure below) ...



Only top voted, non community-wiki answers of a minimum length are eligible