115
votes
Accepted
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 ...
- 5,324
56
votes
Accepted
Have any of the rovers ever recorded a solar eclipse on Mars?
No, because Mars can't have eclipses. Strictly speaking, Mars has only transits. The difference is that Mars's moons are smaller than the Sun as viewed from Mars, thus they don't block out the entire ...
- 121k
47
votes
Accepted
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 ...
- 9,915
37
votes
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 ...
- 3,687
36
votes
Accepted
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 ...
- 178k
34
votes
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 ...
- 6,906
32
votes
Accepted
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 ...
- 58.5k
31
votes
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. ...
- 18.2k
31
votes
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 ...
- 927
28
votes
Accepted
Is this really an image of the sun, or an "artist's conception"?
You can find the image on Flickr.
On August 31, 2012 a long filament of solar material that had been hovering in the sun's atmosphere, the corona, erupted out into space at 4:36 p.m. EDT. The ...
- 126k
28
votes
Accepted
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 ...
- 7,780
25
votes
Accepted
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 msneuver.
To begin with, the closest stars (apart from the Sun) are not ...
- 8,445
24
votes
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
24
votes
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 ...
- 1,023
23
votes
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 ...
- 12.5k
23
votes
Accepted
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
23
votes
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 ...
- 1,831
19
votes
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 ...
- 5,908
17
votes
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 ...
- 11.5k
16
votes
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
votes
Accepted
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 ...
- 6,667
15
votes
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 ...
- 3,585
14
votes
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 ...
- 14.9k
14
votes
Accepted
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 ...
- 5,410
13
votes
Accepted
Which of the planets could we detect today from just the movements of the sun?
Getting hard numbers about how accurate measures we can get from current systems, adapted to the Sun instead of far away stars is difficult, bordering to impossible. But we can get data about the ...
13
votes
Is this really an image of the sun, or an "artist's conception"?
I'm posting these images as a supplement @Hobbes's accepted answer and @TildalWave's comments (which includes links to these images). I started reading some of those links. The gallery is a good ...
- 149k
13
votes
A probe floating in Sun's surface
Thermodynamics says there's no such thing as a completely internal cooling system. The best you can do is pump heat to a cooler location. That's very difficult to come by in the photosphere. ...
- 6,667
13
votes
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 ...
- 6,427
13
votes
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 ...
12
votes
Accepted
Nuking the Sun?
What would happen? Not much. The Sun is mindbogglingly vast. Even our biggest nuclear bombs don't fuse more than 1 ton of hydrogen. Compare that with the Sun's 620 million tons burned per second: the ...
- 126k
Only top scored, non community-wiki answers of a minimum length are eligible