All Questions

Filter by
Sorted by
Tagged with
17 votes
2 answers
3k views

How do planetarium apps and software calculate positions?

In the most general terms (I'm not asking for the actual calculations), how do popular planetarium apps and software calculate the positions of celestial objects? Planets, for example. Do they use ...
2 votes
0 answers
54 views

The necessary conditions for driving winds with dust (Dust-driven Wind)

So lately I've read Intro to stellar winds (particularly chapter 7 Dust-driven winds) by Lamers & cassinelli, I forget how many times I've read this but I still don't really understand. So in the ...
4 votes
2 answers
778 views

Does the luminosity of a star have the form of a Planck curve?

Figure shows the intensity of the radiant energy emitted from stars A and B over a unit time according to the wavelength. The area between the graph and the horizontal axis is S and 4S, respectively. ...
2 votes
0 answers
71 views

Mathematical condition of Stationary Planet

In an old astronomy book I find the following definitions: $\vec r_1$ Position vector of Earth (heliocentric) $\vec r_2$ Position vector of a Planet (heliocentric) $\vec v_1$ Velocity vector of Earth (...
4 votes
3 answers
135 views

Is there a logical reason why we see no back and forth aberration effects when observing binary stars?

I read this article, Questioning Einstein: Is Relativity Necessary? (Bethell (2010), Proc. Natural Philosophy Alliance, v.6, no. 2), regarding the 2 stars of Mizar A and wondering if it is true that ...
7 votes
3 answers
25k views

Why does Venus flicker?

I was watching Venus with the naked eye yesterday at about 7 pm and I noticed that it was flickering, almost like a star. I have always learned that planets don't flicker to the naked eye, only stars ...
7 votes
2 answers
431 views

Venus' magnitude during inferior conjunction

I was doing an assignment on Stellarium when I observed Venus to have an apparent magnitude that didn't become less negative than -3, even at inferior conjunctions when we faced the dark side of Venus....
1 vote
1 answer
97 views

A night caused by an eclipse

Is there a term or a name for the darkness caused when a planet eclipses its moon? For example; if people lived on Titan, a small portion of the near sides lunar day would be eclipsed or partially ...
8 votes
2 answers
1k views

Would Hubble Space Telescope improve black hole image observed by EHT if it joined array of telesopes?

My question is related to black hole image released in April. As far as I understand idea of EHT, it joins observations from multiple locations to work like one telescope with radius that is equal to ...
7 votes
5 answers
6k views

What is the likelyhood that planet X is a glass (not a typo for gas) planet? What would it mean if it were for what we know of astronomy?

Scientists have been looking for an explanation for the unusual orbits of extreme trans-neptunian objects. One of the possible explanations some astrophysicists have come up with was the possibility ...
2 votes
0 answers
68 views

Why did Jupiter spiral into the inner solar system? [duplicate]

We know over 4 billion years ago, Jupiter was created and started to head into the inner solar system until Saturn pulled Jupiter back out. In fact, we wouldn’t be here if Jupiter stayed inside the ...
4 votes
1 answer
95 views

"To date we have covered 624 square degrees of sky near to and interior to the orbit of Venus" meaning wrt Asteroid survey Interior to Earth and Venus

CNN's October 31, 2022 ‘Planet killer’ asteroid spotted hiding in the sun’s glare links to Sheppard et al. (2022) A Deep and Wide Twilight Survey for Asteroids Interior to Earth and Venus. The ...
6 votes
1 answer
1k views

How does the James Webb Space Telescope achieve a focal length of 131.4m?

How does the James Webb Space Telescope achieve a focal length of 131.4m ?
0 votes
1 answer
117 views

Time and space travel as applied to expanding space and the ratio of/between time and distance

If a place is 500 light years away, then I set out to this place, then is it true to say that, the place which I set out from, will be 750 light years away from my destination, once I have reached it? ...
2 votes
0 answers
90 views

"Opacity" in red dwarfs

One day, while researching on blue dwarfs in Wikipedia, I stumbled across something that I cannot understand: Rather than expanding, however, red dwarfs with less than 0.25 solar masses are predicted ...
10 votes
3 answers
6k views

If an Asteroid was to strike the Earth, would it affect the Earth's rotation?

If an Asteroid was to strike the Earth, would it affect noticeably the Earth's rotation, and if so, how large would this Asteroid have to be?
18 votes
3 answers
3k views

Non-anthropic, universal units of time for active SETI

Is there a universal time (duration) reference, an intuitive focal point that works for long periods (compared to the Planck time), and can be used as a signal of intelligence? Assuming a Kardashev ...
4 votes
0 answers
88 views

First satellite of an asteroid (or double asteroid) ever imaged by delay-Doppler radar?

In comments about my previous bounty on the Space SE question Which deep-space spacecraft flew closest by Earth during a gravitational assist?, I started to look at the Galileo mission and ran across ...
8 votes
3 answers
330 views

How do we know that ice from the S1094b event was from Mars surface and not from the impactor?

The recent news story NASA’s InSight Lander Detects Stunning Meteoroid Impact on Mars, about an impact that occurred on Mars on December 24, 2021 (event S1094b), shows a picture of the impact crater, ...
11 votes
1 answer
1k views

How much more life could the Sun acquire via star lifting?

It has been proposed before that we could use this technique to remove hydrogen from the Sun to lower it's rate of fusion and extend it's life, so it doesn't fry our planet. I am wondering how much ...
8 votes
1 answer
1k views

How does the Sun orbit the Sun-Jupiter Barycenter?

I got the Orbital Elements of Jupiter around the Sun, which describe how it orbits relative to the "fix" Sun. Jupiter Semi Major Axis (AU): 5.20336301 Eccentricity: 0.04839266 Inclination to ...
3 votes
0 answers
55 views

Negative flux values in radio maps?

I am trying to understand some maps of radio emission in e.g the Milky Way. I continue to see in papers that these radio maps report negative values of the flux in Jansky units, although no ...
4 votes
3 answers
2k views

Motion of rogue planets

Two Questions: 1) Are rogue planets in motion, i.e. are they just wandering freely in space or stationary? 1) Do rogue planets have defined path or a one which can be anticipated? I understand that ...
8 votes
1 answer
6k views

I saw a short-lived brightening and fading of a light in the sky. Was that a star imploding, exploding or going super-nova?

I was looking over the north-eastern skyline from a west coast location and notice something very bright for well over about 10 or 15 seconds, and then it faded completely. I didn't notice it before ...
8 votes
2 answers
518 views

Trying to understand lunar phases

Complete novice here. I'm trying to understand what appears to be two approaches to quantifying lunar phases. Have I got this right? Named lunar phases can be understood as the Moon's ecliptic ...
24 votes
4 answers
2k views

Metallicity of Celestial Objects: Why "Metal = Non-metal"?

Metallicity of objects refers to the amount of chemical elements present in it other than Hydrogen and Helium. Note: The other elements may or may not be actual ...
1 vote
4 answers
145 views

Stellar aberration without relative motion between source and observer

According to SR, there should be no aberration if source and observer move uniformely (as would be the case in terrestrial aberration). In this case we should find at least some celestial bodies that ...
4 votes
0 answers
44 views

What special auxiliary equipment / modeling are needed for ground-based sub-milliarcsecond astronomy?

I'm not asking about the astronomical equipment itself. I'm asking about the auxiliary equipment and modeling needed to enable the primary astronomical equipment to work properly at the sub-...
6 votes
2 answers
206 views

When will the last total lunar eclipse happen?

Since the moon is receding from earth, solar and lunar eclipses become more rare. Earth will receive the last solar eclipse in around a billion years, but at the same time the Earth will look smaller ...
3 votes
1 answer
1k views

What would our Sun look like from other solar systems?

I came across an article that shows how the Sun looks from other planets of our solar system. Now I am wondering, how does our Sun look from an exoplanet? I am guessing it must be looking like a 'star'...
6 votes
1 answer
215 views

How diverse are chemical reactions outside Earth?

Chemical reactions we are used to here on Earth are hardly possible in most of interstellar space due to extremely low temperature and density (though some pretty complex molecules are found there, ...
3 votes
0 answers
90 views

How do you keep your astronomy computer precisely on time?

I have two laptops running astronomy projects but the clocks are imprecise. I set the specialpollinterval to update the time to windows time once a day 86400s. This eventually worked after I set the ...
1 vote
0 answers
65 views

What do negative values on bright sources in TIRSPEC mean?

I opened a FITs image data from TIRSPEC (NIR imaging) (an HgCdTe infrared imaging sensor) on DS9 and I saw that some of the bright stars have black patches at the center (negative values). Can you ...
3 votes
0 answers
161 views

How a sunspot number is calculated by an individual observer?

How a sunspot number is calculated by an individual observer? I would like to learn how to calculate the daily number of sunspots and where to get daily input images of the Sun. I have read tens of ...
3 votes
3 answers
174 views

What kind of beast is Daylight Savings Time and Standard Time?

I understand that UTC, for example, is a "time system" and that there are regions of the globe that are divided into "time zones" (offsets from UTC); but what class of thing is, ...
7 votes
1 answer
517 views

Are lunar phases and lunar standstills in sync with each other?

Do either of the standstills (N/S) coincide with full/new moon? If yes - what is the relationship? If no - what factors impact the relationship between the two?
6 votes
1 answer
162 views

What is the equation for the radius of a star trail?

I have been studying star paths, and have successfully used the following equations to map star paths in a multiple exposure photograph onto circles of a radius determined by the star's declination ...
4 votes
1 answer
495 views

What is the mass of exoplanet HD 100546b?

What is HD 100546b's real mass? In Wikipedia I found that its mass is 3.1 Jupiter's masses but at Nasa official site I found that it was 752 Jupiter masses, which sounds unbelievable. And on the ...
19 votes
6 answers
11k views

Why do stars become red giants?

Disclaimer: I’m not a career astronomer. I don’t own a telescope. I have no professional credentials. But I do find this stuff fascinating, and I consume all the astronomy documentaries I can. ...
4 votes
2 answers
643 views

Why do post main sequence stars enter the red giants branch?

I am an early graduate student in astronomy and have hard time understanding why do post-MS stars move up the RGB. Here is what I understand about post main sequence evolution of stars. As their ...
7 votes
1 answer
121 views

How could ultracompact galaxies form?

Normally, most galaxies such as our Milky Way tend to be diffused. Sure, the Milky Way, for example has 400 billion stars, but it is spread out over 150,000 light years. Which means that the Milky Way ...
2 votes
2 answers
188 views

Draco, Thuban and Northern Ecliptic Pole

I want to try confirm my thoughts on the position of Thuban (Alpha Draconis) in relation to the Northern Ecliptic Pole (NEP). I have been asked to specify how many degrees Thuban is from the NEP today ...
3 votes
0 answers
79 views

Deviations of conservation laws in the context of cosmological evolution?

If energy is "not conserved" in General Relativity (or at least, it is difficult to define it) in the context of an accelerating expanding spacetime (like it happens in our Universe), are ...
1 vote
1 answer
429 views

Is a Gravastar with no horizon with ultracompact and extreme density possible?

Is that possible with some strange Quantum Effect could give rise to a completely new kind of a star? Gravastar(Gravitational Vacuum Star) an object hypothesized in astrophysics as an alternative to ...
-6 votes
1 answer
153 views

Super conductivity of black holes

We all know that we cannot see black holes due to its strong gravitational force. But I think gravity is not the cause for invisibility of black holes. The temperature of a black hole is 1.4×10-14. ...
2 votes
1 answer
74 views

How are the products of stellar nucleosynthesis sorted as found in planets?

Stellar nucleosynthesis is responsible for creating the elements heavier than lithium (except perhaps some of the heaviest that might result from neutron star collisions). Eventually, the star goes ...
9 votes
2 answers
982 views

Lightest Neutron Star ever observed?

Fundamentally, my question is, is this a real and confirmed observation? Or is there a too-high margin of error for now? Inspirational discoveries, Lightest neutron star ever discovered might ...
4 votes
1 answer
296 views

Is pointing a telescope at a random place a viable astronomical strategy?

Recently I happened to be on the MAST portal, looking at jwst data. I happened to come across 2 interesting targets, “random place” and “another random place” This got me thinking. It’s almost ...
6 votes
1 answer
179 views

Does anybody know how to solve this Earth-Venus-Sun problem?

How can I find (in terms of the angle) the moment when in the system Sun-Earth-Venus, Venus can be seen the most bright if its brightness (flow received in Earth) is proportional to the size projected ...
3 votes
1 answer
108 views

Does JWST have the largest bandwidth of any telescope?

If the longest and shortest wavelengths that JWST can focus are 28.3 and 0.6 microns respectively, then it has a bandwidth (max/min) of a factor of about 47. That's a lot, and of course it needs ...

15 30 50 per page
1
43 44
45
46 47
294