# All Questions

8,493 questions
Filter by
Sorted by
Tagged with
30 views

### How can a mirror see what the eye can’t

How does a mirror pick up light from vast distances away and if that light can reach a mirror why can’t we see that light.
16 views

### Big what, how can we tell?

Why was the particle smaller than a grain of sand at the Big Bang and not something very massive that left all this dust and stuff out there.
16 views

### Does this CHEOPS first light image imply bad astronomy?

@KeithMcClary's comment under lousy mirror corrected by software links to Bad Astronomy's First Light for the Exoplanet Hunter Mission CHEOPS Goes Tetrahedral which shows the image below. I ...
29 views

### Satellites traveling in single file across the sky [duplicate]

I just watched 46 (best count) satellites traveling in single file, about 3 second intervals between them. Is that possible? I don't want to believe they were UFO's. Time was ...
22 views

### Why do radio telescopes, but not shorter wavelengths, have this Big Data problem?

Only with new radio telescope arrays like ALMA and SKA, have I heard of this "problem" with too much data come up. Too big to store. That one cannot archive it all for future studies, but that one has ...
74 views

### The Solar System formation

I've recently watched one conversation (I won't post a link since the conversation is not in english) involving a physicist (at least he claims so), who spoke about probabilistic estimates of the ...
78 views

### Largest body in the solar system that a baseball thrown by a professional pitcher could escape

What is the largest (most massive) known body in the solar system that a professional pitcher could throw a baseball off of, i.e. that has an escape velocity lower than ~102 MPH? (45.33 m/s)
29 views

### Where can I find data for fast radio bursts like FRB 180916?

Where can I find Strength over Time for FRB 180916? Or at least day+time of remarkable events. Is there some good data for other FRB that hit the earth for the last 2 years?
41 views

### How variable does a star have to be, to be a variable star?

Variable stars are stars whose apparent magnitude varies. But there are so many phenomena that can cause a star to be variable, that I would expect all stars to be variable. A rotating star has a ...
47 views

### lousy mirror corrected by software

Would it be possible to get a terribly shaped mirror, like a large sheet of something reflective, give it a general shape like a telescope mirror, but not anywhere near as precisely shaped as in a ...
72 views

### Was the Earth-Sun distance ever calculated based on the time difference between night and day?

If we define sunrise and sunset as the time when the center of the Sun goes over the horizon then day time is a little bit shorter than night time because from a single point one cannot see a complete ...
147 views

### Is there a distinction between NEOs and near-Earth asteroids? Is there a difference?

My "real question" is in Space Exploration Meta (neo (near-earth-object) and near-earth-asteroid tags, do we need both?), but I think that astronomers will be able to help understand the situation and ...
67 views

### At what gravity does a body's gravitational lensing become observable?

I wonder whether we know at how much gravitation a gravitational lensing around a celestial body becomes observable (visible in the sense of that we see stars on the wrong places, stars behind the ...
7k views

### Is there any point on earth where the moon stays below the horizon for an extended period of time?

When I was teaching a class why the earth has seasons today, I mentioned how the poles of the earth experience months of daylight and darkness. Then one of my students asked whether the moon ...
27 views

### Henyey method for interior parts of the star

Does there exist a code that implements Henyey method for interior parts of the star?
725 views

### Could mirrors be replaced with CCDs?

Why do telescopes use mirrors that simply reflect photons, when they instead could be covered with large sensors to register them? Reflection is all good and well, all thanks to silver and beryllium ...
1k views

### Are we seeing a conjunction these mornings?

I have a doubt about planetary conjunction. These days, we can see Saturn, Mars, Jupiter and the Moon close to each other. I mean if Saturn, Mars, Jupiter and the Moon were in conjunction with each ...
202 views

### Betelgeuse in false colors, is this common?

First, take the original Betelgeuse image from ALMA and remove red and green channels. Then boost the blue channel luminosity by x10 to x20 and a lot of detail pops out. This is the resulting image ...
175 views

### Creating an HR diagram from tabulated stellar data

I teach statistics and study Astronomy. I'd like to create an activity for my statistics students using star data. They could enter the data into Excel and create an HR diagram. We are currently ...
5k views

### What is this web on the surface of the Sun?

I was going through my Social Media Feed and found the attached post too frequent. The caption reads this is the best image of our Sun. Just as an example, the Universe Today's This is the Highest ...
114 views

### Consequences of strong wind on an alien Planet on the possibility of life

I was surprised to learn recently that Neptune has winds of 1500 miles an hour. My question is whether life could ever evolve on such a Planet that has such powerful winds? Not necessarily on ...
437 views

### What exactly is a “moon”?

Recently some new moons of Jupiter were discovered. However the moons are pretty damn small indeed - only a few kilometers wide. That makes me wonder if they should even be called moons in the first ...
99 views

### What is the difference between a moon and a random chunk in the rings

Jupiter has 79 (known) moons, Saturn 82, Uranus 27 and Neptune 14 (numbers come from Wikipedia). These planets also all have rings. The rings are made up of chunks of rock and ice. There also are ...
53 views

### Redshift and Velocity relation

Let us say that we have an object so its total velocity is defined as $$v_{tot} = v_{pec} + V_{rec}$$ Where $$V_{rec} = H_0r$$ and \...
221 views

### 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 ...
497 views

### Without using absolute magnitudes or isochrones, how might we tell a star's age and evolutionary status?

Usual methods of estimating stellar ages involve isochrone approximations. It can also help to estimate a star's radius by correlating its absolute magnitude with effective temperature and apparent ...
115 views

### “Pluto Time” for any solar system body

A while back NASA made a site called Pluto Time, where you can enter your address and find that "...moment near dawn and dusk each day, where the illumination on Earth matches that of high noon on ...
72 views

### What constellation is closest to the Zenith with RA=12 and Dec =47.6?

I have several options, but I do not know how to calculate which option is closest to the zenith in title. Could you please help me with this? Thank you. ...
52 views

### Encode place and date in star pattern

Disclaimer: I'm an astronomy noob You sometimes see in (B?) movies, that they infer dates from sky patterns. I was asking myself if you can encode a place and date in a mostly meaningful pattern? ...
44 views

### How to calculate the true length of day on a celestial body?

When I only know the sidereal rotation period, how do I determine the true length of day on a body? We know the Earth's sidereal day doesn't have full 24 hrs unlike the true length of day. It's ...
104 views

### Is there a stellar database that indicates how long ago stars in our Galaxy formed?

There are several ways of determining the age of a star: its position in the HR diagram, the presence of a protoplanetary disk, it belonging to a cluster... When did the stars in our Galaxy form? Do ...
2k views

### Daily magnitude of Betelgeuse

I tried searching on the internet and could not find anything, so does anyone know if there's a website which tracks and shows Betelgeuse's magnitude daily? I just went out today and saw that it's ...
37 views

### When Betelgeuse goes supernova, will the explosion hit any neighboring stars?

There is evidence Betelgeuse might go supernova "soon". Are there any stars in the vicinity of Betelgeuse that are close enough that they will be hit by the explosion of this supernova? What would be ...
2k views

### Are stars expected to become dimmer before a supernova?

With the recent news about the "fainting" of Betelgeuse and the speculation that this might be a precursor to a supernova, I'm wondering if there is any theoretical/observational basis for this ...
22 views

### What are good resources to study Gravitational Waves?

I am undergraduate student having basic knowledge of Physics. I'm looking for resources (books, video lectures, research papers, etc) to study Gravitational Waves from scratch, I think initially I ...
239 views

### Is there a way to tell the difference between earth andesite from Mars

I'm curios if there is a way to test if this sample might be Martian andesite. What type of oxygen isotope (or other) test can be done to address this in some way? As background, any information ...
52 views

### Would the Event Horizon Telescope be able to produce a superior image of Betelgeuse?

Current images of Betelgeuse are already amazing, but I was wondering if the EHT could be able to make a significantly better image, given that Betelgeuse is pretty big and pretty bright?
83 views

### Are Sun-Earth L1 & L2 points generally considered outside the Earth's Hill Sphere?

This image from Wikipedia of the SE Lagrange points and the Hill Spheres suggests that the SEL points are outside the Earth's Hill Sphere. (The Hill spheres are the circular regions surrounding the ...
90 views

### Why does the Sun track out a seemingly sinusoidal path on the celestial sphere?

The question arose because I wanted to understand the path of the ecliptic after reading about it here: https://community.dur.ac.uk/john.lucey/users/solar_year.html Is the sinusoidal path due to ...
554 views

### Is the moon's orbit circularizing? Why does tidal heating circularize orbits?

The moon has an elliptical orbit (of course), but as it inches away from the Earth each year, does its orbit become more circular and how come? Io's orbit is becoming more circular due to tidal ...
36 views

### Field rotation and observing the moon

For stars, field rotation can be accounted for with an equatorial mount aligned with the Earth's axis and turning at the correct rate. Since the Moon's orbit is on a different axis then the Earth's ...
26 views

### How to understand the meaning of this International Occultation Timing Association (IOTA) lunar occultation of Mars map?

Earthsky.org's Watch Mars disappear behind the moon on February 18 as well as Moon occults Mars morning of February 18 include the image below and credit it to The International Occultation Timing ...
1k views

### The deduction of the Hill Sphere formula

This question may be a little lazy, but can anybody give me a proof of the Hill sphere formula? Acording to wikipedia, the formula for the radius, $r$, is r\approx a(1-e)\left(\frac{m}{3M}\right)^{...
92 views

### Is it plausible to use other stars for the proposed FOCAL mission instead of the Sun?

For some time, the far-reaching and speculative idea of using the Sun as a gravitational lens has been floating around. See this and this. This would require sending a spacecraft about ~550 AU of a ...
76 views

### Do pulsar beams interact with the interstellar medium?

Pulsars are rotating objects that emit a beam in a direction that is not aligned with the axis of rotation. Because of this, we see them as a periodic pulse. If the beam isn't towards us, we don't see ...
19k views

### Why don't astronomers use meters to measure astronomical distances?

In astronomy distances are generally expressed in non-metric units like: light-years, astronomical units (AU), parsecs, etc. Why don't they use meters (or multiples thereof) to measure distances, as ...
55 views

### I saw this ball of light moving across the sky [duplicate]

As I stated in the title, I saw this ball of light moving across the sky. It wasn't moving fast, but it wasn't moving slow. So, I was sitting my dad's car when I looked through the windshield and at ...
8k views

### Is Jupiter still an anomaly?

I remember a few years ago hearing that Jupiter was an anomaly in the landscape of exoplanets. Back then, most Jupiter-mass planets discovered were Hot Jupiters, orbiting very close to their host star....