M108 is a nearly edge on spiral galaxy located about 46 million ly away in the constellation of Ursa Major.

Adding a luminance channel (L) of an unfiltered image can improve a RGB image by providing better brightness and detail information. RGB only on left, LRGB on right.

Galileo's discovery of the moons of Jupiter was one of the nails in the coffin of the geocentric model of the solar system.

NGC 7000 - The North America Nebula is a large HII region where stars are likely being formed. The smaller Pelican Nebula to the lower right is actually part of the same region. A cloud of dark gas and dust is between us and the HII region, giving the region the shape we see.

The Double Cluster is a pair of open clusters located in the constellation Perseus. The Double Cluster is an excellent view in binoculars.

Duck! M31 - The Andromeda Galaxy is heading towards us at about 110 km/s. M31 and the Milky Way will collide in about 4.5 billion years from now.

The Hubble extreme deep field. With the exception of about 3 foreground stars, every object you see in this image is a galaxy.

Integration time is what astronomers call exposure. More integration allows you to see fainter things. The progression of integration times on these images is 1 minute, 2min, 4min, then finally 8min.

The Moon is slowly moving away from the Earth, a few centimetres per year. In order to conserve angular momentum, the energy needed for the Moon to do this comes from the Earth. As a result the Earth's rotation is slowing on the order of 2ms/100yr.

To give you an idea of just how bright supernovae are, the supernova circled here is in the galaxy we can see in the picture, about 20 Mly away. Every other individual star you can see in the image are foreground stars in our own Galaxy, only a few thousand ly away.

Yesterday I showed M101 with a supernova, I've put the SN image here with it indicated. It was a type 1a SN which are important due to what causes them. They're caused by either a white dwarf accreting too much mass or merging WD stars. Since the mass is the same each time type 1a supernova all have roughly the same intrinsic brightness. This makes them excellent standard candles for measuring distance. They're bright enough that we can use them out to about 2200 Mpc or 7.1 billion light years.

Messier 101 is a spiral galaxy located about 21 Mly away in the constellation of Ursa Major. In 2011 a Type Ia supernova was detected in this galaxy. Can you find the supernova in the second image?

Nebulae mark the beginning and the end of the lives of stars. Nebula such as M42 (L) are regions of active star formation where stars are being born. Nebula such as M1 (R) are remnants of supernova explosions, the death of massive stars.

Globular clusters, such as M2 - shown, are great balls of 10s to 100s of thousands of stars that orbit our and other galaxies. Made of mostly older lower metal stars, we don't have a clear idea of how they form.

A transit is when a smaller body passes between us and the larger body, allowing us to see the smaller body on the face of the larger. The image shows a transit of Mercury, as the planet passes between us and the Sun.

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