MISSING DARK MATTER HUBBLE MYSTERY
Dark matter is the invisible glue that holds the universe together.
"Galaxy Motion Simulation. Observed with Dark Matter (On left) and Predicted without Dark Matter (On Right.)"
Most galaxies are rotating so fast that gravity generated by stars and gas alone can’t keep them together.
They should have flown apart long ago. Something we can’t see must glue them together: dark matter.
Unlike observable matter, dark matter does not emit, absorb, or reflect light, making it hard to detect.
Instead, astronomers look for the gravity signature of dark matter by observing its effects on galaxies.
In 2018, galaxy NGC 1052-DF2 made headlines because it seemed to be missing dark matter.
The observed number of stars in NGC 1052-DF2 accounted for most of the gravity.
This unique galaxy contains a tiny fraction of the dark matter astronomers expected.
A galaxy lacking dark matter is an extraordinary claim. It upsets theories of galaxy formation and evolution.
Because this result was so unusual, some astronomers questioned it.
They looked for other explanations. Could the galaxy be closer, and have fewer stars than its brightness suggested?
It would also imply the galaxy had more dark matter, to balance the insufficient gravity due to fewer stars.
In theory, if two galaxies are the same distance away, their brightness would differ from each other.
But if the galaxy with fewer stars is brought closer…
...both galaxies would appear to be the same brightness.
Hubble collected more data to better measure the galaxy’s distance.
The team targeted aging red stars whose peak brightness is used to determine distance.
But the new Hubble measurements still found it was a distant galaxy as originally suspected.
The mystery of why NGC 1052-DF2 is missing most of its dark matter still persists.
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