Ask Me Everything

Mass interest

Blasts from the past

^ Astronomers are

often morę interested in an objecfs mass than they are in its size.

^ Mass is the amount of materiał that something is madę of.

^ In a star, mass determines how a star lives and for how long—the greater the mass, the shorter the life.

^ The most massive stars are around 100 times the Sun’s mass and the least are one tenth of the Sun’s mass.

1.3 million

The number of Earths that could fit inside the Sun

864,000

The width of the Sun in miles (1.4 million km)

3.26 million

The universe expands by around 45 miles (72 km) per second for every 3.26 million ly

The distance in light-years from the Sun to the center of the Milky Way

believe it

Earth is in the Milky Way galaxy, which is part of the Local Group of galaxies—one of the galaxy clusters that make up the Local Supercluster.

In tum, the Local Supercluster is one of the superclusters that make the Pisces-Cetus Supercluster Complex, which is around one billion ly long and 150 million ly wide.

The minimum number of galaxies in the universe

The Milky Way galaxy belongs to a collection of morę than 40 galaxies known as the Local Group. They exist in a dumbbell-shaped volume of space ten million light-years across. These are some of the group’s best-known members.

Triangulum ga!axy

50,000 ly wide

Large Magellanie Cloud

20,000 ly wide

• Galaxies are huge collections of stars, gas, dust, and dark matter all bound together by gravity.

• The biggest galaxies are around 300,000 ly across and contain around one thousand billion stars.

®The smallest galaxies, known as dwarf galaxies, measure a few thousand ly across and have around ten million stars.

Astronomers naye    (

toundahugevo»_ond

3.5 billion W-^®9_fboth

spacethatis _hasStars

know

Galaxies have been changing in size, mass, and shape

sińce they first formed billions of years ago.

Universe size I 8|9

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