If the rotational speed of the gas in the disk of a spiral galaxy is 100 km/s at a distance of 26,000 light-years from its center,then what is the mass enclosed within this radius? If the mass of luminous matter inside this radius is 5 billion 
then what fraction of the galaxy's mass is made of dark matter?
Definitions:
Insurance
A contract represented by a policy in which an individual or entity receives financial protection or reimbursement against losses from an insurance company.
Related Therapy
Therapeutic practices or interventions that are associated with and complement the primary treatment of a patient's condition or disorder.
Homeopathy
A system of alternative medicine based on the principle of treating individuals with highly diluted substances to trigger the body's natural system of healing.
Controversial
Describing an issue, subject, or opinion that provokes disagreement or debate among people.
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