All Questions

1answer
28 views

What uncertainty does an error bar signify in astronomy?

When an astronomer talks about her/his topic and shows an X/Y-plot with error bars. What should one assume that those error bars represent? 1 standard deviation? Or 2? Or some specific significance ...
2answers
49 views

Is it proper to refer to objects beyond Neptune as “Kuiper Belt Objects?”

It seems to me that nowadays the more proper term is "Trans-Neptunian Object". Is there any difference between Kuiper Belt Objects and Trans-Neptunian Objects? If not, is one term preferred over the ...
1answer
30 views

Determination of orbital elements for Trans-Neptunian Objects, how?

How are orbits calculated for Trans-Neptunian Objects? I understand there are six standard parameters for defining an orbit (link) but I am not sure how telescope observations translate into these ...
1answer
49 views

How are parachutes usable in other places than Earth?

Mars landings, Moon landings. . . Wherever I see a documentary or still pictures in Wikipedia, there are parachutes in the landing of rovers. Whenever I see them, I ask myself, "How they can it ...
0answers
20 views

Estimates for how many Trans-Neptunian Objects there are [duplicate]

The Minor Planet Center shows that we know of about 1350 Trans-Neptunian Objects (TNO's). I think it is safe to assume that we have not found all the TNO's there are to find, even the ones that we ...
5answers
218 views

How far away is the light that would reveal the Big Bang?

I guess theoretically if we could go faster than light, which we clearly cannot, at some point we'd be able to see the big bang itself. Just curious - how far away is that light?
0answers
24 views

What happens to light that travels further than the universe's expansion?

I asked a question about how far away the light was that would reveal the Big Bang (I'll link momentarily). A number of people did their best to explain to me that, from what I gathered among other ...
0answers
51 views

Can an astronaut ever reach a Black Hole theoretically? [duplicate]

Ok, bear with me, while I try to explain the question I have. I read that time slows as we approach a black hole. So, suppose,theoretically, as astronaut is approaching a Black Hole. And he gets ...
1answer
65 views

If Kepler-444 planets existed for 11.2 billion years, why fear for life on Earth after six billion years?

According to recent news, Kepler-444, a 11.2 billion year old star, has a system of five planets. It has a mass of 3/4 of solar mass. So I believe both Kepler 444 and the Sun will share the fate of ...
3answers
147 views

How precisely is planetary tilt defined (the tilt direction, not just the angle)?

The earth's axis is titled 23.4 degrees with respect to the ecliptic. Since this tilt is responsible for the seasons, it's clear that the tilt is in the direction away from the sun on the shortest day ...
0answers
11 views

Binocular with features like gleam night sight advantage?

Im looking for binoculars, I have seen specs like DAY & NIGHT ZOOM BINOCULARS, Full size day and night vision ,binoculars gleam night sight. Are these thing helpful when i look in ...
0answers
30 views

Ice giants and Gas Giants

I had this speculation: I know that temperature and therefore internal pressure of a planet drops with its distance from the star, which explains why Uranus and Neptune are colder and smaller than ...
1answer
31 views

Why would all places appear to be at the center of the universe's expansion?

I just watched an iMax planetarium video that claimed that no matter where you are in the universe, it will appear that you are at the center of the universe and all things are expanding away from ...
1answer
44 views

Calculate the time when Arcturus passed through the meridian

If the observer observes Arcturus passed through the meridian about 23:00:00 of 28 April. Find the time that Arcturus passed the meridian in 29 April. And what day does the Arcturus will pass the ...
4answers
224 views

Burning Out Stars

In the book "A Really Short History Of Nearly Everything", I read that the larger the star is, the faster it burns itself. Whys that? Wouldn't there be more energy to burn if it's larger, and just be ...
1answer
49 views

Does one need to take into account finite gravity speed in N-body simulations?

Most small-scale N-body simulations (e.g., planetary systems, solar system, stellar clusters, ...) use classical Newtonian gravity. Most large-scale N-body simulations (e.g., galaxy clusters, ...) ...
2answers
87 views

Why are gas giants colored the way they are?

As I understand it, Jupiter, Saturn, Uranus, and Neptune are all made primarily from varying proportions of hydrogen and helium. Despite this, Jupiter is very red, Saturn is yellow, and Uranus and ...
3answers
141 views

What are the arguments against the Feng and Gallo thin disk explanation of galactic rotation curves?

The well-known galaxy rotation problem is described here. Basically (as one moves outward from the galactic centre, $R$ increasing) the observed pattern of variation in orbital speed $V$ is very ...
1answer
67 views

Are a black hole's jets caused by the black hole's magnetic field?

Do the jets sometimes emitted by a black hole result from its magnetic field? It would seem Jupiter's magnetic field tends to be concentrated at the poles, and I would imagine this might extend to ...
1answer
137 views

Cancelling out earth rotation speed, Altazimuth mount

I have a Dobsonian telescope. It is using Altazimuth mount. Basic idea of using it is to target the object by moving telescope vertical axis perpendicular to the ground, and an elevation axis that ...
2answers
70 views

Galaxy rotation curve and dark matter

I am reading "The Essential Cosmic Perspective" by Jeffrey O. Bennett, Megan O. Donahue, Nicholas Schneider, Mark Voit. In Chapter 14, it is stated that an evidence of the presence of dark matter in ...
2answers
62 views

What will happen when landing on Jupiter?

Jupiter is a gas giant, so landing on it will not be like Earth, our moon or Mars etc., as it does not have a surface like these. If we have a hypothetical spaceship or probe landing on Jupiter, ...
2answers
50 views

Does the cosmic microwave background change over time?

Does the cosmic microwave background pattern change over time? I would assume it is getting "cooler" as in more redshifted as time passes, but I am more interested if the pattern on the background, ...
2answers
954 views

Does a black hole become a normal star again?

Stars which satisfy the Chandrasekhar limit can become a black hole. What happens to star after it becomes a black hole? Does it regain its status of star?
1answer
106 views

Entropy of black hole

A line from one of the answers on a different question got me thinking: The simplest way to see this is probably that a black hole has a much higher entropy than a star or even another type of ...
1answer
33 views

Does the cosmic microwave background recede at the speed of light?

Does the cosmic microwave background recede at the speed of light? Is it possible it recedes even faster because of the stretching of space?
1answer
48 views

Find the height of the shooting star from the Earth's ground

One night, you and your friend were talking to each other. Your friend far about 20 km. from you. You told your friend that you see the shooting star pass through the sky at altitude of 75 degrees. ...
2answers
865 views

Is C/2012 S1 (aka ISON) the fastest comet on record to-date?

This source may be nebulous (no pun intended!) for some. It writes to say Starting at around 95,000mph at the start of this month, Comet ISON will eventually reach an astonishing 845,000mph on ...
1answer
53 views

What are the exact physical parameters used to calculate Mercury precession with Einstein theory?

NASA measured 43,13 arc seconds per century. General relativity predicts 42,98 arc seconds per century. I try to find out what the parameters' values such as $G$, $M_{sun}$, $\omega_{min}$ at ...
1answer
349 views

How much mass does an object in space need to keep a human on its surface?

Assume there were a roughly spherical object in space like a meteorite or a comet. If I weighed 80kg on Earth, how much mass would be required for an object in space so that I could stay on its ...
2answers
290 views

Telescope buying guide for a beginner in India

I am located in the southern part of India and am looking forward to buy a telescope to gaze up to look ay farther planets, moons in our solar system and take pictures. How should I go about getting a ...
3answers
887 views

When we see half moon, why is it always the lower half?

Even if we see a crescent moon, always the lower circumference is visible. Why we never see this? PS: this image is vertically inverted.
3answers
106 views

Is it possible to disprove geocentrism without telescopes?

The development of telescopes enabled the discovery of moons orbiting around Jupiter, and the existence of a full set of phases of Venus, as opposed to a limited set which would be predicted by ...
0answers
26 views

Multi Universe theory [duplicate]

I understand and also believe that there can be other Universes but what I don't understand is why these other Universes have to be weird ? Why can't they be like our Universe ? Also I don't ...
4answers
58 views

Light Cone Explanation

Not sure if this question belongs here, or on Physics. Would someone please describe the "anatomy" of a light cone and provide an intuitive example? I have read the Wikipedia article ...
1answer
60 views

Mass, Radius, Colour, Size, Type of a Star from the Hipparcos Catalog

Using data from the Hipparcos Catalog download file, is there a way to determine the Visual or Apparent Magnitude from the data within? Can I obtain the Mass, Radius, colour, temperature, type ...
2answers
70 views

Could there be another planet between Mercury and the Sun?

Could there be another planet between Mercury and the Sun? Kepler found a lot of planets orbiting its star even 20 times closer than Mercury. If there were such planets in our system - would it be ...
2answers
40 views

What qualifies as a local star?

My professor used the term 'local star'. What range of distance is generally considered 'local' for a star? And what would be considered distant?
2answers
79 views

In geocentric models, did the earth rotate?

Under geocentric models, did the earth rotate around its axis? I assume that if the earth rotated around its axis, then the sun would not have to orbit around the earth at a very fast rate, whereas ...
0answers
25 views

Can you suggest telescope for beginners? [duplicate]

I am interested in astronomy and want to look deep into the awesome sky . So, suggest me an economic telescope or the specifications that are to be considered. I am from India.
2answers
79 views

How gently could a comet/asteroid/meteorite “hit” Earth?

Could an object from outer space with the right velocity and orbit come into contact with the surface of our planet in a "slowish" manner?
3answers
134 views

Gallery of 'actual images' from space?

Where can a gallery of actual unaltered photographic images taken in (or of) space be found? Specifically ones that are untouched, not colorized (not necessarily black and white), and taken by natural ...
6answers
811 views

How are black holes found?

Black holes have so much gravity that even light can't escape from them. If we can't see them, and the suck up all electromagnetic radiation, then how can we find them?
2answers
146 views

Can we conclude with reasonable certainty that there is/are no Type 3 Civilizations in our galaxy?

As per the Kardashev Scale, type-3 civilizations are defined as "civilization(s) in possession of energy on the scale of its own galaxy, with energy consumption at ~ 4 x 10^44 erg/sec". Considering ...
4answers
898 views

By putting a mirror in space, would we be able to see into the past?

I only ask this because of how fast light travels. The question remains in the title. Why, or why not, would this work?
1answer
53 views

Why do not we use optical telescopes to study cosmic rays directly?

HESS, CTA, and VERITAS are used to study cosmic rays. What they receive are optical (maybe very blue) photons. So my question is: Why don't we use optical telescopes to study cosmic rays directly?
2answers
80 views

earth is spherical , does it mean the ground on earth is like a ball? [closed]

I know earth is spherical in shape. Does this means earths atmosphere is spherical in shape or the ground/(land+water combined) is in spherical shape. I have some doubts if the second is true. ...
2answers
47 views

Why do we have so few neutrinos to study?

According to Wikipedia most neutrinos passing through the Earth emanate from the Sun. About 65 billion (6.5^10) solar neutrinos per second pass through every square centimeter perpendicular to the ...
2answers
114 views

What proportion of planetary systems have been found with 'Hot Jupiters'

According to the NASA website "The strange attraction of Hot Jupiters", one of the main types of exoplanets that have been detected are Hot Jupiters, which are These are behemoth worlds that ...
2answers
78 views

Likelihood of a stable system with a dwarf planet's orbit inside that of a gas giant

I keep thinking of various planetary system configurations, and would like to know: What are the fundamental references based on Monte Carlo long-term simulation of planetary systems' evolution that ...

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