115
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Why is it easier to escape the solar system than get to Mercury or the Sun?
Because the earth goes very fast around the sun.
If you want to get to the sun, you need to slow down almost completely so that your speed relative to the sun becomes almost zero.
If you don't slow ...
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47
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Do you need 0 km/s velocity to crash into the sun?
Wouldn't i inevitably spiral to sun surface even if i was faster than 0km/s ?
No. On reasonable timescales, an orbit will have a fixed distance of closest approach, called "periapsis." (These ...
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37
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Why is it easier to escape the solar system than get to Mercury or the Sun?
Changing orbits requires delta-v. To reach the Sun, you need to subtract delta-v such that your velocity relative to the Sun is near zero, which allows you to "fall straight down" into the ...
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What would happen if a satellite took a direct hit from a coronal mass ejection (CME)?
We can look at what happened when this actually occurred.
The geomagnetic storm of March 1989 was caused by a Coronal Mass Ejection.
Here are just a few of the many effects on satellites.
One ...
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34
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Has any object launched from Earth gone into the Sun?
No, not yet. The Parker Solar Probe became the closest ever artificial object to the sun on October 29th, 2018, surpassing Helios 2 which held the record since 1975 [1].
No other human-made object ...
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Is it really ~648.69 km/s delta-v to "land" on the surface of the Sun?
Addressing
is the sun's mass and other quantities known well enough for this to be absolutely accurate?
Well, the key to this is the vis-viva equation in your question. It's not actually important ...
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How to check, if there is currently an increased solar activity?
Looks pretty darned quiet to me right now:
You can find that here, along with other measures of space weather.
By the way, cosmic rays and solar activity are two entirely different things. Cosmic ...
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31
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What would happen if a satellite took a direct hit from a coronal mass ejection (CME)?
I spent a couple of years working in the Astrophysics and Space Physics Section of JPL. Working with the Space Physics folks taught me a lot about the solar wind and other space weather phenomena. ...
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28
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Why does the ISS need thermal blankets if the Sun is hot?
As noted in another question, the ISS faces some pretty hot temps. Remember, the Sun heats radiantly. When you're sitting in that much radiant heat, without an atmosphere to dissipate it, you're going ...
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Is it really ~648.69 km/s delta-v to "land" on the surface of the Sun?
The Vis-viva equation is
$$ v = \sqrt{ GM \left(\frac{2}{r} - \frac{1}{a} \right) }, $$
The $GM$ product for the Sun is 1.327E+20 m^3/s^2.
If 1 AU is 150E+09 meters, then when you are in a ...
- 149k
27
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Did any spacecraft ever use the Sun's gravity for acceleration?
It doesn't really work that way. We can use the Sun to change direction, but we need rocket thrust to increase speed with the maneuver.
To begin with, the closest stars (apart from the Sun) are not ...
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Where exactly was this picture of a huge solar eruption taken?
The photo was taken from the Skylab space station in Earth orbit using a telescope.
The telescope was part of a solar observatory known as the Apollo Telescope Mount, which was specifically designed ...
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25
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Why is it easier to escape the solar system than get to Mercury or the Sun?
Escaping the solar system requires adding orbital velocity to the spacecraft. Similarly, getting closer in the solar system requires removing orbital velocity. It turns out Earth is more out of the ...
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Is oxygen present in the sun?
The sun is not "burning" in the sense you are used to: there is no chemical reaction going on. Instead, there is a very high pressure in the core of a star (like our sun) due to the high mass that ...
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23
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Did any spacecraft ever use the Sun's gravity for acceleration?
The "gravitational" (slingshot) maneuvers space probes are performing are actually not so much about gravity. The gravity is method to "tie" temporarily these two bodies, but you could (purely ...
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Could we possibly see the shadow offset from Parker Solar probe on Earth?
The closer an object to the source of light, the larger the shadow it casts.
That's true if we're talking about a point source or at least a compact source of light and "shadow" refers to ...
- 149k
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Do you need 0 km/s velocity to crash into the sun?
You need below 2866 m/s of orbital velocity at 1 AU to crash into the Sun.
You technically don't need to slow down exactly to 0 m/s relative to the Sun in order to crash into it. Let's calculate the ...
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Do you need 0 km/s velocity to crash into the sun?
And note that if you want to hit the sun the cheaper (but slow!) way to do it is to head out. 12.32km/sec will take you to infinity, at infinity a burn of 0m/sec will kill your orbital velocity and ...
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16
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For an object in a geostationary orbit to have the same apparent diameter as the sun, how big would it have to be?
If something is twice as far away, it has to be twice as wide to have the same apparent size.
If it's 10x farther away, it needs to be 10x bigger.
The Sun is 4250 times farther away than GEO, so the ...
15
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Is it possible to reach the Sun without expending any fuel/reaction mass?
If you're already in a solar orbit, then yes. You can use a sail at an angle and send the reflections prograde. The result is to reduce your orbital energy and you spiral in.
I recall it was a ...
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15
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Icy Hot Astronauts
Common wisdom says that space is cold. I wouldn't go so far as to call that a misconception, but it's certainly a bit of a misunderstood fact.
See, space is not cold in the way your fridge or a block ...
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Where exactly was this picture of a huge solar eruption taken?
Going to the skylab 3 wiki article and clicking on the image reveals the following information:
Photo credit: NASA -
http://spaceflight.nasa.gov/gallery/images/skylab/skylab3/html/s74-15583.html
...
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14
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Did any spacecraft ever use the Sun's gravity for acceleration?
I think the question is based on a misconception about how gravity assists work.
If you just let yourself get pulled to a distant object then continue out the other side, the same gravity that ...
14
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Why is it easier to escape the solar system than get to Mercury or the Sun?
Based on the calculations presented by @uhoh I generated a plot showing the necessary delta-V for
a fly-by mission, i.e. entering into a Hohmann transfer with a far point intersecting the orbit of a ...
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14
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If JWST can look into 13 billion years past then why it cannot check sun formation which happened only 4.603 billion years ago?
The James Webb Space Telescope has the potential to observe things that occurred thirteen billion years ago, because those objects were at sufficient distance at that time that the light they emitted ...
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13
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Why does the ISS need thermal blankets if the Sun is hot?
Insulation can function in both ways, keeping heat on whichever side is desired. In space limiting the amount of thermal input from the sun is very valuable since that heat is easily acquired but hard ...
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13
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How far is the solar system's center of mass from the sun?
The solar system barycenter, as it's called, is a dynamic point that moves (or the Sun moves relative to, depending on how you think about it) depending on where the planets are in their orbits and ...
- 10.1k
12
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Most distant photo of the sun?
Voyager 1 took an image of the sun on February 14, 1990 at a distance of 6 billion kilometers. The famous Pale Blue Dot was captured at the same time and is superimposed here as well as a narrow angle ...
- 23.8k
12
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Which spacecraft will be the first for which the Sun would become the second brightest object in the sky?
As a reference, part of this question I answered at Astronomy.SE. The closest point at which the Sun would not be the brightest object in the sky is if we headed directly towards Sirius A, at a ...
- 122k
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Is it really ~648.69 km/s delta-v to "land" on the surface of the Sun?
It's a "real number", a delta-v chart isn't really concerned with the realism of various missions. It's quite simply a table of velocity changes, how you would go about achieving these velocity ...
Only top scored, non community-wiki answers of a minimum length are eligible