With astronomical images, the colours can be set to mean different things if special filters were used. In this image the red channel was through a [SII] filter, the green through a Halpha filter and the blue through a [OIII] filter. This means red shows S, green H and blue O.
Can you spot Pluto in these two images taken 2 nights apart?
M16 - the Eagle Nebula from last night. 0.2m f3.9 telescope. 8 min L, 2 minutes each R, G, and B. This is an active star formation nebula approximately 7000 ly distant. The famous Hubble "Pillars of Creation" are in this nebula and can be seen in the centre of this image.
The magnitude scale in astronomy gives an indication of an object's brightness. The larger the number, the dimmer the object. It is a logarithmic scale, that is a 5th magnitude star is 100 times dimmer than a 1st magnitude star.
Under general relativity the faster your are moving, or the stronger the gravity field you are in, the slower clocks will run compared to those moving slower or in weaker gravity. This is enough that the clocks on the GPS satellites have to compensate for it.
The Apollo astronauts left laser retro-reflectors on the Moon which allowed us to measure the distance to the Moon to an accuracy of a few centimetres.
The Virgo cluster of galaxies is one of countless large grouping of galaxies in the universe. Our own Galaxy is a member of the Virgo cluster. Rothney Astrophysical Observatory Baker-Nunn telescope mosaic.
This is the Hubble extreme deep field. With the exception of (from what I can find) 3 foreground stars, every object you see in this picture is a galaxy. Can you find the foreground stars? Know the trick?
If what's left over after a supernova explosion is less than about 3.5 times the mass of the Sun it will be a neutron star. If it's larger than 3.5 solar masses it will become a black hole.
The arcs around the two galaxies in the centre of this Hubble image are caused by the light from galaxies behind the galaxy cluster in the centre being bent by the gravity of the cluster. This is gravitational lensing.
M17- the Omega or Swan Nebula is a star formation region about 5000ly from us. It glows red because the young stars excite the gas of the nebula.
The ecliptic is the Sun's apparent path through the sky. The Sun's motion along the ecliptic is actually due to the Earth's orbit around the Sun. The 23° angle the ecliptic makes with the celestial equator is due to the Earth's axial tilt.
Open clusters of stars, such as M11 (The Wild Duck Cluster) are amazing labs for stellar evolution. Since the stars in the cluster were formed at roughly the same time one can work out how mass and stellar lifetime relate to one another. More massive stars live shorter lives.
M42- The Great Nebula in Orion, is a massive star formation region. It's also relatively close being in the 1400-1500 ly range of distance.
Planetary nebulae are generally round/elliptical or bipolar-butterfly shaped.
We don't know exactly what the collimation mechanism is for the bipolar PNe. (Left my image of M97, right Hubble image of M2-9)
Stars between about 1 times the mass of the Sun and 6-8 times the mass of the Sun end their days as a white dwarf after becoming a planetary nebula. Some planetary nebulae shown: Owl Nebula, Ring Nebula, and Dumbbell Nebula.
Stars with a mass greater than 8 times that of the Sun die spectacularly. Once the matter in their cores is fused in to iron, fusion shuts down and the star then explodes in a supernova explosion.
The Crab Nebula, shown, is the remnant of a supernova recorded in 1054 by Chinese astronomers.
The amount of energy recieved by the Earth from the Sun has increased about 1 W/m^2 over the past 1000 years. The average variance over the 11 year sunspot cycle is about 3 W/m^2. The average total amount is about 1300 W/m^2.