# All Questions

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### Where can I look up assigned origins of gamma ray bursts events? (GRBs)

Gamma ray burst GRB170817A is believed to have originated from the merger of Neutron Star(NS)-Neutron Star(NS). From this article on the associated gravitational wave detection GW170817: The ...
9 views

### What if a primordial black hole went through the Sun?

How much mass would the Sun lose to a primordial black hole that (initially) has 10 Earth masses, passing through the center of the Sun at solar escape velocity? How massive would the Sun end up and ...
27 views

### Source of red in earth's photographs

What is the red in this picture of earth? At first we thought it might be pollution, but Jupiter also has red. Picture source: https://education.seattlepi.com/primary-movements-motions-earth-4701....
47 views

### Are occultation observations used/useful for orbit determination?

The IAU Minor Planet Center lists $(486958)\space 2014 \space MU_{69}$ "Ultima Thule" as having an uncertainty parameter of 2, based on the observation arc of 851 days, from its discovery in 2014, to ...
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### Is 486958 Arrokoth (2014 MU69 aka Ultima Thule) the only solar-system object determined to be binary by occultation?

The asteroid 486958 Arrokoth was discovered to be binary by astronomers lugging a bunch of telescopes around (I think) camping with them. The timing offered additional astrometry for the orbit ...
80 views

### What's the temperature of Pluto's core?

The surface is freezing-nitrogen cold, but it's typical for the temperature to increase towards the core. What's the temperature of the core of Pluto? Is the planet icy and rocky all the way through? ...
44 views

### How would Earth's magnetic field change if the outer core was solid?

A widely accepted theory for how the Earth's magnetic field is generated is the dynamo theory. Dynamo theory describes how molten magma convection currents containing metal are locally spun the same ...
210 views

### Earth Versus Catastrophic Meteor

How evasive is the Earth to Catastrophic Meteors? Google says the Earth is approximately 92.96 million miles from the Sun. It also says the suns radius is 432,474 miles. Therefore, it is 93,392,474 ...
32 views

### redshift in astrophysical plots [closed]

Why do astrophysicists often use redshift in plots? Why it is important to know how an astrophysical object evolves in function of redshift? I was seeing an "cosmological time per redshift ...
8k views

### Do our sun and moon have names?

We seem to have named every moon orbiting other planets. Why haven't we named our own moon? And for that matter, why doesn't our sun have a name since we name or number stars?
327 views

### How would the sky look if Earth orbited a red giant at a safe distance?

Let's say that instead of the sun, we have a red giant, but are orbiting it at a safe distance, within the goldilocks zone. Would the sky actually look more red? Or would it be closer to white/...
3k views

### How far could be an object from the Sun and still be under the influence of its gravitational field?

I'm trying to see how far can our star reaches with its gravity. I'm asking if anyone could give info as to what's our star's limit or the furthest object found in our solar system.
90 views

### What would happen to the Sun's evolution if it collided with another yellow dwarf?

How would the Sun evolve if it collided with another G-type main sequence star, perhaps a more massive one like Alpha Cen A? Since its mass would then be above the Chandrasekhar limit, could it ...
114 views

### Grammar of stellar classification

How to write G2V correctly (I mean space)? I saw in articles $G\,2\,V$ and $G2\,V$, on the internet webside it is usually $G2V$.
22 views

### Is there a luminosity class for brown dwarfs?

I've been reading about brown dwarfs, and checking their spectral types, and I noticed that they do not have a luminosity class (V, VI, etc). So I am wondering, do brown dwarfs have a luminosity class,...
94 views

### Can lunar occultation of Venus occur during solar eclipse?

Moon can occult Venus. Venus can transit across the solar disc. Moon can elipse Sun. Can all three celestial events occur at the same time - Moon is at front of Sun (partial eclipse is fine) and Venus ...
44 views

### How to improve the precision in a star's distance

When I use the Gaia star catalogue, the parallax values often have large uncertainties which, therefore, leads to a large uncertainty for the distances to the stars. If you were interested in the ...
22 views

### Naming convention for multiple star systems

Okay, so I've seen different notations for the stars in β Capricorni. Some sources state that the stars are Aa, Ab1 and Ab2, Ba, and Bb, while others say that they are Aa, Aba and Abb, Ba, and Bb. So, ...
3k views

### If an exoplanet transit we are seeing is 13000 light years away, are we seeing a 13000-year-old orbit? [duplicate]

If a star is 13000 light years away, doesn't that mean we are seeing 13000-year-old light? If it does, then does that mean when we discover a planet with dimming star light, we are seeing a planet ...
77 views

### Why are telescope mirrors nearly flat?

My understanding of telescope mirrors is that they are (generally speaking) a slice out of an imaginary sphere. The center of this sphere is the focal point of the telescope, where the detector is ...
814 views

### “Periapsis” or “Periastron”?

I was taught from Bate Mueller and White, that the proper terms for the closest and furthest points and distances from a body in orbit around another unspecified body are "periapsis" and &...
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### Does a gravitational lens around a body look 3-dimensional?

Suppose we approach a neutron star or a stellar black hole close enough, is the gravitational lens around it 3-dimensional (like a tunnel) or is it 2-dimensional? It's 3-dimensional as if you entered ...
3k views

### Where can I find the positions of the planets, stars, moons, artificial satellites, etc. and visualize them?

What resources are available to find the positions of planets, stars, moons, artificial satellites, asteroids, and other heavenly bodies?
54 views

### When does a solar eclipse become noticeable?

For a human viewer located on Earth, is there an approximate apparent magnitude at which a solar eclipse becomes apparent in the form of a noticeable change in ambient brightness? Assume normal ...
78 views

### Was there ever a meteorite with a measurable gravity?

Did we ever find a meteorite (a meteoroid that has fallen down to Earth) whose mass, density and gravity were high enough to demonstrate their gravity similar to the Cavendish experiment, so that ...
15 views

### Constants of three body problem(2 fixed centers)

I was solving two fixed centers problem and got answer in quadratures. After that i want to find constants of motion. First one is full energy - E. Second is $p_{\varphi}$. And third one comes from ...
116 views

### How to derive Kepler's 1st Law?

I was going through the derivation of Kepler's 1st Law in the textbook "An Introduction to Modern Astrophysics" by Carroll and Ostlie. From there, I got stuck in a few places in their ...
165 views

### How do ASKAP's focal plane phased array feeds interact with the entire array phasing?

Sky & Telescope's ASKAP Joins the Hunt for Mysterious Bursts says: A new telescope, the Australian Square Kilometre Array Pathfinder (ASKAP), has joined the search for energetic and elusive ...
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### Relationship between Periapsis and apoapsis longitude

What is the relationship between Periapsis and Apoapsis longitude ? Are they 180° apart ? (ie) Periapsis + 180° = Apoapsis ? Related question: if apoapsis is not known, what orbital elements are ...
60 views

### Accuracy of the Inflation theory

In the Inflation theory, it said that the Inflationary epoch has happened $10^{-32} \,\mathrm{s}$ after the Big Bang, and I cannot find anything related to how this number was calculated and how ...
367 views

### Are we less safe now that Arecibo is no more?

update 3: uhoh! Source: Reddit update 2: Sadly, parts of the dish have collapsed, several cables have snapped, and the Arecibo radio telescope is now decommissioned and demolition has been ...
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### What are the prime challenges in search for extraterrestrial intelligence? [closed]

What have we been able to accomplish so far and what are the prime obstacles that block our sight? My understanding is that Radio Telescopes are the prime tool for the search. I wonder what kind of ...
243 views

### Is the wind's intensity on Mars similar to Earth?

I've read that in Mars' poles, the winds can be as fast as 400 km/h, when the poles are exposed to sunlight because the frozen $CO_2$ sublimes. I know that the Martian atmosphere is much thinner than ...
100 views

### When was the last time a great conjunction coincided with a solstice?

This December, a great conjunction will occur nine hours after winter solstice, which means that for much of the world the two events will be on the same day. When was the last time a great ...
6k views

### Did I see a supernova explosion?

I think I just saw a supernova explode with my own eyes through my GSO 12 inch Dobsonian. Please tell me what it was! I am still trying to find what it was it was mindblowing! I went out on my roof ...
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### Callisto's orbit: circular vs JPL is periodic 4 degree error, why?

I am approximating the azimuthal angle of Callisto from Jupiter or the Jupiter+moons barycenter using a constant angular speed circular orbit. This differs from the JPL ephemerides by only about 4 ...
1k views

### Size and Mass of a typical “small” asteroid that impacts the Earth?

I'm looking for some realistic data about the size (in meters) and mass (in kg) of a typical small asteroids that impact the Earth, without disintegrating in the atmosphere. Any suggestion ?
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### How fast is Neptune getting brighter? When was was this first noticed and reported?

This answer to Compute Planet's Apparent Visual Magnitude reports the new work on planetary magnitudes, and contains an intriguing blurb about Neptune: Neptune keeps getting brighter. No one knows ...
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### Blackbody curve in RGB for objects less than 1500 K?

We know the colors of stars that have a temperature greater than 1000-1500 K, shown here. However, I am wondering about those stars/brown dwarfs with surface temperatures of less than 1500 K. Is there ...
70 views

### Why 2014-2015-2016 were the years when the number of discovered exoplanets increased the most?

So, if we look into the cumulative number of exoplanets discovered by year, you can appreciate a huge rise in the number of discovered exoplanets in the years 2014 and 2016: Credit to NASA Exoplanet ...
50 views

### If the Earth circled a red dwarf/giant or a brown dwarf, would its sky still look blue? [duplicate]

I have the impression that in brown dwarf and weak red dwarf systems, everything looks more reddish on a planet, including its atmosphere regardless of composition. Suppose there's a planet having an ...
50 views

### “LinAlgError: SVD did not converge in Linear Least Squares” with eleanor.py

I'm doing some tests with eleanor module (i'm a novice). I'm using the example code written on eleanor.py website ...
29 views

### Hypothetical CMB space telescope design problem, received power from extended thermal source versus receiver front end NEP?

Consider the example of a large radio dish antenna in space equipped with a heat shield protecting it from the Sun. Let's say the amplifiers front-end effective temperature (for purposes of noise ...
150 views

### Trans-Neptunian Dwarf Planet near Heliopause

Is there any reason to think a Trans-Neptunian dwarf planet, the size of Pluto, could not exist in a Keplerian orbit 120AU from the Sun? If such an object existed, and came within 0.1AU of the ...
35 views

### What does the “a” at the end of a spectral type mean?

Looking at the chart for spectral type peculiarities (here), I noticed that the letter a was missing from the chart. This seems to be an error, as the star Vega has spectral type A0Va, with the a ...
456 views

When making an observation using a radio telescope, is it possible to filter out noise coming out from a known source by using another telescope that will focus on that noise source? By filtering, I ...
2k views

### What gases are needed to make a star?

What gases do you need to start the creation of a star, and why do you need these gases? What are their functions?
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### Formation mechanism of a non-barred 6-arm spiral galaxy

UGC 12588 has an unusual morphology of an old dwarf spheroidal with six very young spiral arms. None of the 24 Simbad references describe its morphology or recent history from the galactic assembly ...