All Questions

Filter by
Sorted by
Tagged with
0
votes
0answers
2 views

Is Betelgeuse is continually expelling material on the scale of the 2019/2020 event?

Results from Hubble suggest that Betelgeuse's recent dimming was due to material ejected from the star: ...the star's unexpected and significant dimming periods in late 2019 and early 2020 were most ...
0
votes
0answers
20 views

Would They Tell Us If An Unstoppable Threat Was Approaching

This recent piece somewhat kindled my thoughts on this question, but I've pondered it for a while now: https://www.scientificamerican.com/article/a-movie-of-the-evolving-universe-is-potentially-scary/ ...
0
votes
0answers
23 views

Is there any synthetic spectrum software for neutron star?

Is there any software that can calculate the emergent spectrum of a neutron star photosphere, for Teff is about 1e7K, density is above 1e21-1e22 cm^-3 ? Output line wavelength is about 0-100A is ...
2
votes
1answer
182 views

For what parameter does the abbreviation MA stand for?

In the sentence: "We added a Keplerian model with P = 120.713 days, m = 14.629M⊕, e = 0.0448, ω = 251.36°, and MA=216.88° plus Gaussian noise with rms=5.9696 ms-1." P is the orbital period, ...
2
votes
0answers
35 views

How do I plot orbit planets and satellites?

I need to find the way to plot orbit planets and satellites in a coherent way. Let's say I want to generate a chart of the Moon's orbit around the Earth, or the jovian satellites around Jupiter. The ...
1
vote
1answer
35 views

Converting Light curve to Luminosity

So I'm currently working around a specific variable star, α Ori and I want to determine it's luminosity...I do only have the light curve (driven from V-optical photometric band - Johnson V from AAVSO)....
3
votes
2answers
161 views

What is it about the layout of the three gratings in a Bahtinov mask that makes its indicate focus in this way?

The question Lucky imaging with Celestron 14 - is this result reasonable? includes a beautiful example of a focus test using a Bahtinov mask and the image below from Deep Sky Watch's Home Made ...
4
votes
1answer
207 views

What determines if a comet's debris will produce periodic meteor showers?

Background I was wondering if the debris from the comet NEOWISE that recently passed Earth would provide meteor showers in the future. I looked up that the Perseid meteor showers happen when the Earth ...
1
vote
1answer
46 views

Why is the Cosmic Microwave Background at the same distance no matter the direction we look?

I've read from different sources that: The CMB is visible at a distance of 13.8 billion light years in all directions from Earth, leading scientists to determine that this is the true age of the ...
3
votes
1answer
48 views

What name was voted for Tau Boötis b by the Name Exoworlds Project?

In 2015, the exoplanet Tau Boötis b was included in the Name Exoworlds Project, a project where various international astronomy organizations would propose names for a selection of known exoplanets ...
1
vote
1answer
35 views

how to find the approximate [stellar radius]? (distance from center to most distant star) of a circular flat disk galaxy based on its stellar mass?

I'm doing a high school programming project on drake's equation (simple galactic model) and wondered if there was a (simplified) way to find the radius (measured by the distance between the center and ...
4
votes
1answer
256 views

Why the number of Long Gamma Ray Bursts(LGRBs) is greater that number of Short Gamma Ray Bursts(SGRBs)?

I collected https://www.google.com/url?sa=i&url=https%3A%2F%2Fgammaray.nsstc.nasa.gov%2Fbatse%2Fgrb%2Fduration%2F&psig=AOvVaw09lbpxsH2xmfnCCXQh4cKn&ust=1597302004094000&source=images&...
1
vote
1answer
50 views

How to see Mars and Venus in color?

My telescope is Arsenal - Synta 70/700 AZ2 (refractor model). 140x max zoom (10 mm with Barlow). I could clearly see Jupiter and Saturn in color. I even saw brown stripes on Jupiter. Yet, when I tried ...
2
votes
2answers
97 views

can moon rise before sun and set after it in the same day

I found it mentioned in ancient Arabic astronomic book Kitāb al-Amwāl by Ibn Qutaybah (889 AD) Cresent can't be seen in the morning in the east in front of the sun and in the evening i the west ...
1
vote
0answers
20 views

What is the mass and momentum of a relativistic jet?

Relativistic jets from accreting black holes are powerful radiation sources, but carries some ionized matter along. What are the estimates or observations of the mass or momentum flow in such jets?
1
vote
1answer
64 views

What satellite is this?

While out viewing the Perseid shower last night (8/11/20), we saw an interesting object that I'm trying to identify. We're in the vicinity of Portland, Oregon. It appeared to be traveling west->...
2
votes
0answers
37 views
+50

Determine spectral type of star from its properties

How can I determine spectral type of star, if I know all its another properties? For Example, Rigel A has spectral type B8Ia. Rigel has temperature 12 500 K. ...
1
vote
1answer
41 views

How can one determine the angle between the line of nodes and the major axis of the orbit of Mars?

Edit: What I really was looking for, was the difference in longitude on the orbit of Mars between its aphelion and the point where the north pole axis of Mars would point towards the Sun (northern ...
0
votes
1answer
43 views

Question about semi-major axis mean separation

I am currently doing an assignment but I cannot for the life of me understand what one of terms used means. Notice I am not trying to get help with the assignment itself, but rather to make me ...
6
votes
2answers
1k views

What color is a red dwarf star?

I read recently that a red dwarf star might actually look white. I realize there's a wide range in red dwarf surface temperature, 2,500 to 3,500 degrees K, compared to 5,778 for our Sun. Metal at ...
1
vote
2answers
27 views

How can I estimate the initial luminosity of a SNIa given initial mass of Ni-56?

The initial portion (and peak) of a SNIa's light curve is powered by the $\beta$-decay reaction: $$ ^{56}Ni \rightarrow ^{56}Co + e^+ + \nu_e + \gamma $$ Supposing we know how much Ni-56 is created in ...
1
vote
1answer
53 views

Celestron C14 collimation and cleaning

When checking the collimation of a Celestron 14" SCT I took this image: My question is: how much will the particles causing the local aberrations affect the image quality? (i.e. do I need to ...
2
votes
0answers
66 views

How did we measure the mass of the universe?

In an wiki article, observable universe, it was mentioned that, Mass (ordinary matter) 1.5×10^53 kg I wonder how did we measure the mass of our observable universe?
3
votes
1answer
85 views

Can a telescope ever increase the apparent luminance of an extended object?

From what I know about common telescope designs, telescopes don't increase the apparent luminance of extended objects compared to the luminance seen with the naked eye. In this sense extended objects ...
3
votes
0answers
55 views

How much (more or less) of the moon will be visible as it recedes from the Earth?

The Moon is receding from the Earth, at a rate of about 4 cm per year. We can currently see about 59% of the Moon's surface, from the Earth's surface. Will the amount of the Moon's surface we can see ...
1
vote
1answer
36 views

Why is the peak value(s) of the spectral radiance of the CMB different if you calculate with freq. instead of wavelength?

On Wikipedia, the calculated value of the peak frequency of the cosmic microwave background is 160.23 GHz, but it says if you do the calculating with wavelengths, then convert to frequency, you get a ...
0
votes
0answers
14 views

What was the energy/wavelength/frequency of the CMB when first emitted/released?

Given the z redshift of 1089, and the temperature difference between then and now of about 1089, I tried scaling the ev, freq. and wavelength by 1089.... Is that right? I get a freq. of about 240 ...
9
votes
4answers
3k views

How much does the sky change in a few thousand years?

The "fixed stars" are not actually fixed, the earth's tilt changes over time etc., but all that happens slowly on human timescales. Imagine a Babylonian astronomer (or astrologist?) ...
0
votes
1answer
51 views

360 degree image of the whole sky

I look for an image that I know exists. It is an image showing the whole sky, showing all stars and galaxies bright enough to be visible at the resolution, projected to the same shape that is commonly ...
3
votes
2answers
131 views

If the solar system is nearly flat, then why don't all the planets appear to lie on the same axis when viewed from earth?

For instance, consider the image below. The location of the planets seem to be so random relative to Earth. If the solar system was indeed flat, then I would expect the planets to lie on the same '...
1
vote
1answer
42 views

Picking two random points in space and drawing a line between them, what is the chance the line intersects anything?

I thought of this question after pondering how most of the observable universe is observable. If we can observe it, then the space between us and that object must have been unoccupied to allow the ...
3
votes
1answer
30 views

How can I calculate the uncertainties in magnitude like the CDS does?

When you check an entry of the Gaia DR2 stellar catalogue in Vizier, for example this one, you can see that there is a value for the G magnitude (in our case 18.0733 mag) and a value for the ...
35
votes
5answers
4k views

Why can't we see Saturn's phases from earth?

In the Astronomy Picture of the Day from August 8, 2020 ("Crescent Saturn"), the caption states From Earth, Saturn never shows a crescent phase Why is this? We can observe phases on ...
1
vote
1answer
47 views

Timekeeping on other celestial bodies than Earth

I have looked for months for any site capable of calculating solar altitude w.r.t an observer located on the surface of a generic celestial bodies, but with no luck as of now. Even NASA does not ...
3
votes
1answer
49 views

Black Hole - energy and matter

Can someone explain what is happening with energy (e.g. light) and matter which was collected by a black hole? I suppose that matter builds a black hole's mass and size, but what about light? Does it ...
-2
votes
0answers
31 views

Problem 7- chapter 13 of the Astronomy Principle and practice.-Calculate the radius of Venus

Well, this is one of the exercises from chapter 13 of the Astronomy Principle and Practice, which using Kepler's Laws to solve it. But if there are other ways to solve that would be great. Thank you!
1
vote
1answer
65 views

How does a cross dispersed spectrum look like in a reality (from echelle spectrographs)?

I am an analytical chemist with some interest in amateur spectroscopy. Since astronomers use echelle spectrographs to study the high resolution spectrum of the stars, someone suggested to post the ...
12
votes
2answers
1k views

Shouldn't tidal locking be impossible for a satellite that has a considerably eccentric orbit?

This popped up into my mind just now. The Moon is tidally locked to Earth, and also has a significantly eccentric orbit. This means that its orbital velocity near periapsis is considerably faster than ...
4
votes
2answers
491 views

What is meant by “vastness of space, which now filled a volume of a hundred million light years”?

I am reading the book Cosmic biology: How life could evolve on other worlds (citation below) and do not understand the meaning of the following paragraph from page 4 (emphasis mine): It took 200,000 ...
8
votes
2answers
2k views

Where is the Perseids meteor shower coming from?

Swift–Tuttle Comet has orbital period of 133.28 years. Yet, people say that debris and dust from this comet causes this meteor shower. This does not make any sense. Or do they want to say that from ...
5
votes
1answer
53 views

Strange trail left by shooting star [duplicate]

I saw something really odd last night that I cannot understand. Last night I got up around 3am to catch a glimpse of the upcoming Perseids meteor shower, now I know it's not peaking until next week ...
3
votes
2answers
192 views

Are all solutions of the 3-body problem restricted to 2 dimensions?

I am not a physicist. Suppose there are two massive bodies orbiting each other. Their orbit will presumably define a plane. As far as I know, the existing solutions to the 3-body problem are limited ...
3
votes
1answer
35 views

What is wrong with my calculations of Jupiter's apparent magnitude?

I was searching for a formula to calculate the apparent magnitude of a planet knowing its physical characteristics and stumbled upon this answer. The final formula given is: $$m_{planet} = V_{planet} +...
1
vote
3answers
59 views

Practicality of Dobsonian telescopes

I've been using binocular for more than a decade for visual observation. I'm thinking of upgrading to a telescope. The Dob caught my attention due to its simplicity in setup and also cost ...
1
vote
1answer
17 views

Approximate formula to find velocity from cosmological redshift

From IOAA 2013 (Greece) Theory question no. 15, they stated that the approximate formula to find velocity from cosmological redshift is $$v = c*log_e (1+z)$$ and that it is often used by cosmologists. ...
8
votes
1answer
422 views

Why can there be several seconds of lag between a binary neutron star merger and the emission of gamma rays from the same area?

Answers to: Gravitational waves and gamma ray burst: how were the error bars determined for this speed of gravity calculation? Was $H_0$ used? go into substantial detail explaining this determination. ...
0
votes
1answer
84 views

how long a light year on earth will seem [closed]

First of all, sorry if this is not the right StackExchange to ask this question, but i don't know a better place (open to suggestion in case). So, the question: Suppose that for some reason, we can ...
3
votes
3answers
89 views

Impact on the rest of the solar system if Mercury or Venus were disassembled?

I've watched a few theoretical videos about Dyson spheres where they mention that the most practical way to do that would be to disassemble a planet - preferably one already close to the sun - Mercury ...
2
votes
1answer
50 views

Can an event horizon form with the observer already inside?

I am on a planet orbting a star around the center of the milky way (assume no supermassive blackhole there). By some mechanism, mass starting from the outer part of the galaxy gets pushed inward until ...
1
vote
2answers
91 views

Events I cannot explain

In the last few days I experienced two events I cannot explain. I watch the sky since I was a child so I'm aware of most events like satellites, ISS, Iridium flares, etc... First event It was about 22:...

15 30 50 per page
1
2 3 4 5
188